MOPITT Refereed Publications

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Publication Count by Year


Chen, B., J. Hu, and Y. Wang (2024), Synergistic observation of FY-4A&4B to estimate CO concentration in China: combining interpretable machine learning to reveal the influencing mechanisms of CO variations, npj Clim Atmos Sci, 7(1), 112, doi:10.1038/s41612-023-00559-0.
Accurately estimating the concentration of carbon monoxide (CO) with high spatiotemporal resolution is crucial for assessing its meteorological-environmental-health impacts. Although machine learning models have high predictive ability in environmental research, there are relatively few explanations for model outputs. Utilizing the top-of-atmosphere radiation data of China’s new generation geostationary satellites (FY-4A and FY-4B) and interpretable machine learning models, the 24-hour near-surface CO concentrations in China was conducted (resolution: 1 hour, 0.04°). The model improved by 6.6% when using the all-sky dataset (cloud-contained model, R2 = 0.759) compared to the clear-sky dataset (cloud-removed model). The interpretability analysis of the CO estimation model used two methods, namely ante-hoc (model feature importance) and post-hoc (SHapley Additive exPlanations). The importance of daytime meteorological factors increased by 51% compared to nighttime. Combining partial dependency plots, the impact of key meteorological factors on CO was elucidated to gain a deeper understanding of the spatiotemporal variations of CO.

Srivastava, P., M. Naja, P. Bhardwaj, R. Kumar, M. C. Rajwar, and T. R. Seshadri (2024), Utilising BC observations to estimate CO contributions from fossil fuel and biomass burning in the Central Himalayan region, Environmental Pollution, 341, 122975, doi:10.1016/j.envpol.2023.122975.
The Himalayan region is adversely affected by the increasing anthropogenic emissions from the adjacent Indo-Gangetic plain. However, source apportionment studies for the Himalayan region that are crucial for estimating CO concentration, are grossly insufficient, to say the least. It is in this context that our study reported here assumes significance. This study utilizes five years (20142018) of ground-based observations of eBC and multiple linear regression framework (MLR) to estimate CO and segregate its fossil fuel and biomass emission fractions at a high-altitude (1958 m) site in the Central Himalayas. The results show that MERRA2 always underestimates the observed CO; MOPITT has a high monthly difference ranging from −32% to +57% while WRF-Chem simulations underestimate CO from February to June and overestimate in other months. In contrast, CO estimated from MLR replicates diurnal and monthly variations and estimates CO with an r2 > 0.8 for 20142017. The CO predicted during 2018 closely follows the observed variations, and its mixing ratios lie within ±17% of the observed CO. The results reveal a unimodal diurnal variation of CO, COff (ff: fossil fuel) and CObb (bb: biomass burning) governed by the boundary layer evolution and upslope winds. COff has a higher diurnal amplitude (39.167.8 ppb) than CObb (5.733.5 ppb). Overall, COff is the major contributor (27%) in CO after its background fraction (58%). CObb fraction reaches a maximum (28%) during spring, a period of increased agricultural and forest fires in Northern India. In comparison, WRF-Chem tracer runs underestimate CObb (−38% to −98%) while they overestimate the anthropogenic CO during monsoon. This study thus attempts to address the lack of continuous CO monitoring and the need to segregate its fossil fuel and biomass sources, specifically over the Central Himalayas, by employing a methodology that utilizes the existing network of eBC observations.


Ashpole, I., and A. Wiacek (2023), Differences in MOPITT surface level CO retrievals and trends from Level 2 and Level 3 products in coastal grid boxes, Atmospheric Measurement Techniques, 16(7), 19231949, doi:10.5194/amt-16-1923-2023.
Users of MOPITT (Measurement of Pollution in the Troposphere) data are advised to discard retrievals performed over water from analyses. This is because MOPITT retrievals are more sensitive to near-surface CO when performed over land than water, meaning that they have a greater measurement component and are less tied to the a priori CO concentrations (which are taken from a model climatology) that are necessarily used in their retrieval. MOPITT Level 3 (L3) products are a 1∘ × 1∘ gridded average of finer-resolution (∼ 22 × 22 km) Level 2 (L2) retrievals. In the case of coastal L3 grid boxes, L2 retrievals performed over both land and water may be averaged together to create the L3 product, with L2 retrievals over land not contributing to the average at all in certain situations. This conflicts with data usage recommendations. The aim of this paper is to highlight the consequences that this has on surface level retrievals and their temporal trends in “as-downloaded” L3 data (L3O), by comparing them to those obtained if only the L2 retrievals performed over land are averaged to create the L3 product (L3L), for all identified coastal L3 MOPITT grid boxes. First, the difference between surface level retrievals in L3L and the corresponding L2 retrievals performed over water (L3W) is established for days when they are averaged together to create the L3O product for coastal grid boxes (yielding an L3O surface index of “mixed”, L3OM). Mean retrieved volume mixing ratios (VMRs) in L3L differ by over 10 ppbv from those in L3W, and temporal trends detected in L3L are between 0.28 and 0.43 ppbv yr−1 stronger than in L3W, on average. These L3L − L3W differences are clearly linked to retrieval sensitivity differences, with L3W being more heavily tied to the a priori CO profiles used in the retrieval, which are a model-derived monthly mean climatology that, by definition, has no trend year to year. VMRs in the resulting L3OM are significantly different to L3L for 45 % of all coastal grid boxes, corresponding to 75 % of grid boxes where the L3L − L3W difference is also significant. Just under half of the grid boxes that featured a significant L3L − L3W trend difference also see trends differing significantly between L3L and L3OM. Factors that determine whether L3OM and L3L differ significantly include the proportion of the surface covered by land/water and the magnitude of landwater contrast in retrieval sensitivity. Comparing the full L3O dataset to L3L, it is shown that if L3O is filtered so that only retrievals over land (L3OL) are analysed as recommended there is a huge loss of days with data for coastal grid boxes. This is because L2 retrievals over land are routinely discarded during the L3O creation process for these grid boxes. There is less data loss if L3OM retrievals are also retained, but the resulting L3O “land or mixed” (L3OLM) subset still has fewer data days than L3L for 61 % of coastal grid boxes. As shown, these additional days with data feature some influence from retrievals made over water, demonstrably affecting mean VMRs and their trends. Coastal L3 grid boxes contain 33 of the 100 largest coastal cities in the world, by population. Focusing on the L3 grid boxes containing these cities, it is shown that mean VMRs in L3OL and L3L differ significantly for 11 of the 27 grid boxes that can be compared (there are no L3OL data for 6 of the grid boxes studied), with 9 of the 18 grid boxes where temporal trend analysis can be performed in L3OL featuring a trend that is significantly different to that in L3L. These differences are a direct result of the data loss in L3OL data that are available in L2 data (and are incorporated into the L3L product created for this study). The L3L − L3OLM mean VMR difference exceeds 10 (22) ppbv for 11 (3) of these 33 grid boxes, significant in 13 cases, with significant temporal trend differences in 5 cases. It is concluded that an L3 product based only on L2 retrievals over land the L3L product analysed in this paper, available for public download could be of benefit to MOPITT data users.

Chua, G., V. Naik, and L. W. Horowitz (2023), Exploring the drivers of tropospheric hydroxyl radical trends in the Geophysical Fluid Dynamics Laboratory AM4.1 atmospheric chemistryclimate model, Atmospheric Chemistry and Physics, 23(8), 49554975, doi:10.5194/acp-23-4955-2023.
We explore the sensitivity of modeled tropospheric hydroxyl (OH) concentration trends to meteorology and near-term climate forcers (NTCFs), namely methane (CH4) nitrogen oxides (NOx=NO2+NO) carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs) and ozone-depleting substances (ODSs), using the Geophysical Fluid Dynamics Laboratory (GFDL)’s atmospheric chemistryclimate model, the Atmospheric Model version 4.1 (AM4.1), driven by emissions inventories developed for the Sixth Coupled Model Intercomparison Project (CMIP6) and forced by observed sea surface temperatures and sea ice prepared in support of the CMIP6 Atmospheric Model Intercomparison Project (AMIP) simulations. We find that the modeled tropospheric air-mass-weighted mean [OH] has increased by ∼5 % globally from 1980 to 2014. We find that NOx emissions and CH4 concentrations dominate the modeled global trend, while CO emissions and meteorology were also important in driving regional trends. Modeled tropospheric NO2 column trends are largely consistent with those retrieved from the Ozone Monitoring Instrument (OMI) satellite, but simulated CO column trends generally overestimate those retrieved from the Measurements of Pollution in The Troposphere (MOPITT) satellite, possibly reflecting biases in input anthropogenic emission inventories, especially over China and South Asia.

Gaubert, B., D. P. Edwards, J. L. Anderson, A. F. Arellano, J. Barré, R. R. Buchholz, S. Darras, L. K. Emmons, D. Fillmore, C. Granier, J. W. Hannigan, I. Ortega, K. Raeder, A. Soulié, W. Tang, H. M. Worden, and D. Ziskin (2023), Global Scale Inversions from MOPITT CO and MODIS AOD, Remote Sensing, 15(19), 4813, doi:10.3390/rs15194813.
Top-down observational constraints on emissions flux estimates from satellite observations of chemical composition are subject to biases and errors stemming from transport, chemistry and prior emissions estimates. In this context, we developed an ensemble data assimilation system to optimize the initial conditions for carbon monoxide (CO) and aerosols, while also quantifying the respective emission fluxes with a distinct attribution of anthropogenic and wildfire sources. We present the separate assimilation of CO profile v9 retrievals from the Measurements of Pollution in the Troposphere (MOPITT) instrument and Aerosol Optical Depth (AOD), collection 6.1, from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments. This assimilation system is built on the Data Assimilation Research Testbed (DART) and includes a meteorological ensemble to assimilate weather observations within the online Community Atmosphere Model with Chemistry (CAM-chem). Inversions indicate an underestimation of CO emissions in CAMS-GLOB-ANT_v5.1 in China for 2015 and an overestimation of CO emissions in the Fire INventory from NCAR (FINN) version 2.2, especially in the tropics. These emissions increments are consistent between the MODIS AOD and the MOPITT CO-based inversions. Additional simulations and comparison with in situ observations from the NASA Atmospheric Tomography Mission (ATom) show that biases in hydroxyl radical (OH) chemistry dominate the CO errors.

Okpalaonwuka, C., S. Udo, and I. Ewona (2023), Spatiotemporal variation and trend in carbon monoxide concentration over Africa: insights from MOPITT Data, Air Qual Atmos Health, doi:10.1007/s11869-023-01457-3. [online] Available from: .
Carbon monoxide (CO) is an indirect greenhouse gas that has a significant impact on atmospheric chemistry. This study investigates the spatial and temporal variation and trend in CO concentrations over Africa from 2000 to 2019 using data from the Measurements of Pollution In The Troposphere (MOPITT) satellite instrument. The study classifies Africa into eight subregions based on emission inventories: northern hemisphere (NH), southern hemisphere (SH), arid (A), semi-arid north (SAN), savannah NH (SNH), savannah SH (SSH), semi-arid south (SAS), and tropical rainforest (TRF). It is observed that the northern hemisphere contributes about 54.07% of CO over Africa, while the SH accounts for 45.93%. The research reveals that the annual mean columnar CO over Africa declined significantly, with most subregions exhibiting a significant decrease in columnar CO, particularly over the NH windows. The columnar CO over Africa also revealed a seasonal pattern with two peaks in DJF (December-February) and SON (SeptemberNovember), reflecting affluence from both hemispheres. The seasonal maxima and minima differ among subregions. The study further demonstrates that the tropospheric CO’s spatial and temporal variability in most subregions in Africa are sensitive to biomass burning, with MOPITT CO, MODIS fire count, and MODIS FRP being key parameters used to understand CO transport and fire emission across Africa. The study is relevant to climate researchers and policymakers seeking to understand the impact of CO on atmospheric chemistry, air quality, and climate change.

Ortega, I., B. Gaubert, J. W. Hannigan, G. Brasseur, H. M. Worden, T. Blumenstock, H. Fu, F. Hase, P. Jeseck, N. Jones, C. Liu, E. Mahieu, I. Morino, I. Murata, J. Notholt, M. Palm, A. Röhling, Y. Té, K. Strong, Y. Sun, and S. Yamanouchi (2023), Anomalies of O3, CO, C2H2, H2CO, and C2H6 detected with multiple ground-based Fourier-transform infrared spectrometers and assessed with model simulation in 2020: COVID-19 lockdowns versus natural variability, Elementa: Science of the Anthropocene, 11(1), 00015, doi:10.1525/elementa.2023.00015.
Anomalies of tropospheric columns of ozone (O3), carbon monoxide (CO), acetylene (C2H2), formaldehyde (H2CO), and ethane (C2H6) are quantified during the 2020 stringent COVID-19 world-wide lockdown using multiple ground-based Fourier-transform infrared spectrometers covering urban and remote conditions. We applied an exponential smoothing forecasting approach to the data sets to estimate business-as-usual values for 2020, which are then contrasted with actual observations. The Community Atmosphere Model with chemistry (CAM-chem) is used to simulate the same gases using lockdown-adjusted and business-as-usual emissions. The role of meteorology, or natural variability, is assessed with additional CAM-chem simulations. The tropospheric column of O3 declined between March and May 2020 for most sites with a mean decrease of 9.2% ± 4.7%. Simulations reproduce these anomalies, especially under background conditions where natural variability explains up to 80% of the decline for sites in the Northern Hemisphere. While urban sites show a reduction between 1% and 12% in tropospheric CO, the remote sites do not show a significant change. Overall, CAM-chem simulations capture the magnitude of the anomalies and in many cases natural variability and lockdowns have opposite effects. We further used the long-term record of the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument to capture global anomalies of CO. Reductions of CO vary highly across regions but North America and Europe registered lower values in March 2020. The absence of CO reduction in April and May, concomitant with reductions of anthropogenic emissions, is explained by a negative anomaly in the hydroxyl radical (OH) found with CAM-chem. The implications of these findings are discussed for methane (CH4), which shows a positive lifetime anomaly during the COVID-19 lockdown period. The fossil fuel combustion by-product tracer C2H2 shows a mean drop of 13.6% ± 8.3% in urban Northern Hemisphere sites due to the reduction in emissions and in some sites exacerbated by natural variability. For some sites with anthropogenic influence there is a decrease in C2H6. The simulations capture the anomalies but the main cause may be related to natural variability. H2CO declined during the stringent 2020 lockdown in all urban sites explained by reductions in emissions of precursors.

Pathak, M., V. K. Patel, and J. Kuttippurath (2023), Spatial heterogeneity in global atmospheric CO during the COVID-19 lockdown: Implications for global and regional air quality policies, Environ Pollut, 335, 122269, doi:10.1016/j.envpol.2023.122269.
The COVID-19 lockdown (LD) provided a unique opportunity to examine the changes in regional and global air quality. Changes in the atmospheric carbon monoxide (CO) during LD warrant a thorough analysis as CO is a major air pollutant that affects human health, ecosystem and climate. Our analysis reveals a decrease of 5-10% in the CO column during LD (April-May 2020) compared to the pre-lockdown (PreLD, March 2020) periods in regions with high anthropogenic activity, such as East China (EC), Indo-Gangetic Plain (IGP), North America, parts of Europe and Russia. However, this reduction did not occur in the regions of frequent and intense wildfires and agricultural waste burning (AWB). We find high heterogeneity in the CO column distributions, from regional to city scales during the LD period. To determine the sources of CO emissions during LD, we examined the ratios of nitrogen dioxide (NO2), sulfur dioxide (SO2) to CO for major cities in the world. This facilitated the identification of contributions from different sources; including vehicles, industries and biomass burning during LD. The comparison between CO levels during the LD and PreLD periods indicates a notable reduction in the global tropospheric CO, but no significant change in the stratosphere. It is found that CO emissions decreased during LD in the hotspot regions, but rebounded after the LD restrictions were lifted. This study, therefore, highlights the importance of policy decisions and their implementations in the global and regional scales to improve the air quality, and thus to protect public health and environment.

Ravindra Babu, S., C.-F. Ou-Yang, S. M. Griffith, S. K. Pani, S. S.-K. Kong, and N.-H. Lin (2023), Transport pathways of carbon monoxide from Indonesian fire pollution to a subtropical high-altitude mountain site in the western North Pacific, Atmospheric Chemistry and Physics, 23(8), 47274740, doi:10.5194/acp-23-4727-2023.
Dry conditions associated with the El NiñoSouthern Oscillation (ENSO) and a positive Indian Ocean Dipole (IOD) are known to have caused major fire pollution events and intense carbon emissions over a vast spatial expanse of Indonesia in October 2006 and 2015. During these two events, a substantial increase in the carbon monoxide (CO) mixing ratio was detected by in situ measurements at Lulin Atmospheric Background Station (LABS; 23.47∘ N 120.87∘ E; 2862 ma.s.l.) in Taiwan, which is the only background station in the subtropical western North Pacific region. Compared to the long-term October mean (20062021), CO was elevated by ∼ 47.2 ppb (parts per billion; 37.2 %) and ∼ 36.7 ppb (28.9 %) in October 2006 and 2015, respectively. This study delineates plausible pathways for the CO transport from Indonesia to LABS using Measurement of Pollution in the Troposphere (MOPITT) CO observations and Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalysis products (winds and geopotential height GpH). Two simultaneously occurring transport pathways were identified, namely (i) horizontal transport in the free troposphere and (ii) vertical transport through the Hadley circulation (HC). The GpH analysis of both events revealed the presence of a high-pressure anticyclone over the northern part of the South China Sea (SCS), which played an important role in the free-tropospheric horizontal transport of CO. In this scenario, CO in the free troposphere is transported on the western edge of the high-pressure system and then driven by subtropical westerlies to LABS. Simultaneously, uplifted CO over Indonesia can enter the HC and be transferred to subtropical locations such as LABS. The vertical cross section of the MOPITT CO and MERRA-2 vertical pressure velocity supported the transport of CO through the HC. Furthermore, the results revealed a distinct HC strength in two events (higher in 2006 compared to 2015) due to the different ENSO conditions. Overall, the present findings can provide some insights into understanding the regional transport of pollution over Southeast Asia and the role of climate conditions on transport pathways.

Tang, Z., Z. Jiang, J. Chen, P. Yang, and Y. Shen (2023), The capabilities of the adjoint of GEOS-Chem model to support HEMCO emission inventories and MERRA-2 meteorological data, Geoscientific Model Development, 16(21), 63776392, doi:10.5194/gmd-16-6377-2023.
The adjoint of the GEOS-Chem (Goddard Earth Observing System with Chemistry) model has been widely used to constrain the sources of atmospheric compositions. Here, we designed a new framework to facilitate emission inventory updates in the adjoint of the GEOS-Chem model. The major advantage of this new framework is good readability and extensibility, which allows us to support Harmonized Emissions Component (HEMCO) emission inventories conveniently and to easily add more emission inventories following future updates in GEOS-Chem forward simulations. Furthermore, we developed new modules to support MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, version 2) meteorological data, which allows us to perform long-term analyses with consistent meteorological data for the period 1979present. The performances of the developed capabilities were evaluated with the following steps: (1) diagnostic outputs of carbon monoxide (CO) sources and sinks to ensure the correct reading and use of emission inventories, (2) forward simulations to compare the modeled surface and column CO concentrations among various model versions, (3) backward simulations to compare adjoint gradients of global CO concentrations to CO emissions with finite-difference gradients, and (4) observing system simulation experiments (OSSEs) to evaluate the model performance in 4D variational (4D-Var) assimilations. Finally, an example application of 4D-Var assimilation was presented to constrain anthropogenic CO emissions in 2015 by assimilating Measurement of Pollution in the Troposphere (MOPITT) CO observations. The capabilities developed in this work are important for better applications of the adjoint of the GEOS-Chem model in the future. These capabilities will be submitted to the standard GEOS-Chem adjoint code base for better development of the community of the adjoint of the GEOS-Chem model.


Buchholz, R. R., M. Park, H. M. Worden, W. Tang, D. P. Edwards, B. Gaubert, M. N. Deeter, T. Sullivan, M. Ru, M. Chin, R. C. Levy, B. Zheng, and S. Magzamen (2022), New seasonal pattern of pollution emerges from changing North American wildfires, Nat Commun, 13(1), 2043, doi:10.1038/s41467-022-29623-8.
Rising emissions from wildfires over recent decades in the Pacific Northwest are known to counteract the reductions in human-produced aerosol pollution over North America. Since amplified Pacific Northwest wildfires are predicted under accelerating climate change, it is essential to understand both local and transported contributions to air pollution in North America. Here, we find corresponding increases for carbon monoxide emitted from the Pacific Northwest wildfires and observe significant impacts on both local and down-wind air pollution. Between 2002 and 2018, the Pacific Northwest atmospheric carbon monoxide abundance increased in August, while other months showed decreasing carbon monoxide, so modifying the seasonal pattern. These seasonal pattern changes extend over large regions of North America, to the Central USA and Northeast North America regions, indicating that transported wildfire pollution could potentially impact the health of millions of people.

Busa, E., B. Gugamsetty, R. O. R. Kalluri, R. G. Kotalo, C. R. Tandule, L. R. Thotli, M. Chakala, S. N. R. Palle, E. Busa, B. Gugamsetty, R. O. R. Kalluri, R. G. Kotalo, C. R. Tandule, L. R. Thotli, M. Chakala, and S. N. R. Palle (2022), Diurnal, seasonal, and vertical distribution of carbon monoxide levels and their potential sources over a semi-arid region, India, Atmósfera, 35(1), 165178, doi:10.20937/atm.52808.
Daniels, W. S., R. R. Buchholz, H. M. Worden, F. Ahamad, and D. M. Hammerling (2022), Interpretable Models Capture the Complex Relationship Between Climate Indices and Fire Season Intensity in Maritime Southeast Asia, Journal of Geophysical Research: Atmospheres, 127(17), e2022JD036774, doi:10.1029/2022JD036774.
There have been many extreme fire seasons in Maritime Southeast Asia (MSEA) over the last two decades. Fires, in turn, are a major driver of atmospheric carbon monoxide (CO) variability, especially in the Southern Hemisphere. Here we attempt to maximize the amount of CO variability that can be explained during fire season in MSEA (defined as September through December) via human-interpretable statistical models that use only climate mode indices as predictor variables and are trained on data from 2001 to 2019. We expand upon previous work through the complexity at which we study the connections between climate mode indices and atmospheric CO (an indicator of fire intensity). Specifically, we present three modeling advancements. First, we analyze five different climate modes at a weekly timescale, increasing explained variability by 15% over models a monthly timescale. Second, we accommodate multiple lead times for each climate mode index, finding that some indices have very different effects on CO at different lead times. Finally, we model the interactions between climate mode indices at a weekly timescale, providing a framework for studying more complex interactions than previous work. Furthermore, we perform a stability analysis and show that our model for the MSEA region is robust, adding weight to the scientific interpretation of selected model terms. We believe the relationships quantified here provide new understanding of a significant mode of variability in MSEA, specific lead times for use in forecasts, and a method for evaluating climate mode-CO relationships in climate model output.

Deeter, M., G. Francis, J. Gille, D. Mao, S. Martínez-Alonso, H. Worden, D. Ziskin, J. Drummond, R. Commane, G. Diskin, and K. McKain (2022), The MOPITT Version 9 CO product: sampling enhancements and validation, Atmospheric Measurement Techniques, 15(8), 23252344, doi:10.5194/amt-15-2325-2022.

Abstract. Characteristics of the Version 9 (V9) MOPITT (Measurements of Pollution in the Troposphere) satellite retrieval product for tropospheric carbon monoxide (CO) are described. The new V9 product includes many CO retrievals over land which, in previous MOPITT product versions, would have been discarded by the cloud detection algorithm. Globally, the number of daytime MOPITT retrievals over land has increased by 30 %40 % relative to the Version 8 product, although the increase in retrieval coverage exhibits significant geographical variability. Areas benefiting from the improved cloud detection performance include (but are not limited to) source regions often characterized by high aerosol concentrations. The V9 MOPITT product also incorporates a modified calibration strategy for the MOPITT near-infrared (NIR) CO channels, resulting in greater temporal consistency for the NIR-only and thermal-infrarednear-infrared (TIRNIR) retrieval variants. Validation results based on in situ CO profiles acquired from aircraft in a variety of contexts indicate that retrieval biases for V9 are typically within the range of ±5 % and are generally comparable to results for the V8 product.

Desservettaz, M. J., J. A. Fisher, A. K. Luhar, M. T. Woodhouse, B. Bukosa, R. R. Buchholz, C. Wiedinmyer, D. W. T. Griffith, P. B. Krummel, N. B. Jones, N. M. Deutscher, and J. W. Greenslade (2022), Australian Fire Emissions of Carbon Monoxide Estimated by Global Biomass Burning Inventories: Variability and Observational Constraints, Journal of Geophysical Research: Atmospheres, 127(3), e2021JD035925, doi:10.1029/2021JD035925.
Australian fires are a primary driver of variability in Australian atmospheric composition and contribute significantly to regional and global carbon budgets. However, biomass burning emissions from Australia remain highly uncertain. In this work, we use surface in situ, ground-based total column and satellite total column observations to evaluate the ability of two global models (GEOS-Chem and ACCESS-UKCA) and three global biomass burning emission inventories (FINN1.5, GFED4s, and QFED2.4) to simulate carbon monoxide (CO) in the Australian atmosphere. We find that emissions from northern Australia savanna fires are substantially lower in FINN1.5 than in the other inventories. Model simulations driven by FINN1.5 are unable to reproduce either the magnitude or the variability of observed CO in northern Australia. The remaining two inventories perform similarly in reproducing the observed variability, although the larger emissions in QFED2.4 combined with an existing high bias in the southern hemisphere background lead to large CO biases. We therefore recommend GFED4s as the best option of the three for global modeling studies with focus on Australia or the Southern Hemisphere. Near fresh fire emissions, the higher resolution ACCESS-UKCA model is better able to simulate surface CO than GEOS-Chem, while GEOS-Chem captures more of the observed variability in the total column and remote surface air measurements. We also show that existing observations in Australia can only partially constrain global model estimates of biomass burning. Continuous measurements in fire-prone parts of Australia are needed, along with updates to global biomass burning inventories that are validated with Australian data.

Drummond, J. R., Z. Vaziri Zanjani, F. Nichitiu, and J. Zou (2022), A 20-year review of the performance and operation of the MOPITT instrument, Advances in Space Research, 70(10), 30783091, doi:10.1016/j.asr.2022.09.010.
The MOPITT (Measurements Of Pollution In The Troposphere) instrument has been providing continuous measurements of carbon monoxide (CO) total column and CO vertical profile on a global scale since its launch on the Terra spacecraft on 18th of December 1999. MOPITT was one of the first correlation radiometer instruments at the time of its launch, that utilizes a combination of Length Modulating Cells (LMCs), Pressure Modulating Cells (PMCs) and Stirling cryocoolers to observe CO in the troposphere from space. MOPITT is unique in that it is the only space-borne correlation radiometer instrument in current operation that measures CO in the atmosphere. After 20 years of operation, an overview of the telemetry of MOPITT provides significant insight into the performance of one of the longest operating satellite instruments in the space environment. In this work, the engineering telemetry of MOPITT’s core subsystems is examined, with emphasis on their relation to MOPITT’s long-term successes. These instrument successes include: (1) achieving an extremely stable thermal and vibrational environment; (2) allowing for compensation of subsystem failures and anomalies by means of a redundant design; (3) maintaining stable detector performance; and (4) becoming the longest living operational instrument for measuring atmospheric CO columns and profiles.

Hegarty, J. D., K. E. Cady-Pereira, V. H. Payne, S. S. Kulawik, J. R. Worden, V. Kantchev, H. M. Worden, K. McKain, J. V. Pittman, R. Commane, B. C. Daube Jr., and E. A. Kort (2022), Validation and error estimation of AIRS MUSES CO profiles with HIPPO, ATom, and NOAA GML aircraft observations, Atmospheric Measurement Techniques, 15(1), 205223, doi:10.5194/amt-15-205-2022.

Abstract. Single-footprint retrievals of carbon monoxide from the Atmospheric Infrared Sounder (AIRS) are evaluated using aircraft in situ observations. The aircraft data are from the HIAPER Pole-to-Pole Observations (HIPPO, 20092011), the first three Atmospheric Tomography Mission (ATom, 20162017) campaigns, and the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory (GML) Global Greenhouse Gas Reference Network aircraft program in years 20062017. The retrievals are obtained using an optimal estimation approach within the MUlti-SpEctra, MUlti-SpEcies, MUlti-SEnsors (MUSES) algorithm. Retrieval biases and estimated errors are evaluated across a range of latitudes from the subpolar to tropical regions over both ocean and land points.

AIRS MUSES CO profiles were compared with HIPPO, ATom, and NOAA GML aircraft observations with a coincidence of 9 h and 50 km to estimate retrieval biases and standard deviations. Comparisons were done for different pressure levels and column averages, latitudes, day, night, land, and ocean observations. We found mean biases of +6.6±4.6 %, +0.6±3.2 %, and -6.1±3.0 % for three representative pressure levels of 750, 510, and 287 hPa, as well as column average mean biases of 1.4±3.6 %. The mean standard deviations for the three representative pressure levels were 15 %, 11 %, and 12 %, and the column average standard deviation was 9 %. Observation errors (theoretical errors) from the retrievals were found to be broadly consistent in magnitude with those estimated empirically from ensembles of satellite aircraft comparisons, but the low values for these observation errors require further investigation. The GML aircraft program comparisons generally had higher standard deviations and biases than the HIPPO and ATom comparisons. Since the GML aircraft flights do not go as high as the HIPPO and ATom flights, results from these GML comparisons are more sensitive to the choice of method for extrapolation of the aircraft profile above the uppermost measurement altitude. The AIRS retrieval performance shows little sensitivity to surface type (land or ocean) or day or night but some sensitivity to latitude. Comparisons to the NOAA GML set spanning the years 20062017 show that the AIRS retrievals are able to capture the distinct seasonal cycles but show a high bias of ∼20 % in the lower troposphere during the summer when observed CO mixing ratios are at annual minimum values. The retrieval bias drift was examined over the same years 20062017 and found to be small at <0.5 %.

Huang, Y., J. Wei, J. Jin, Z. Zhou, and Q. Gu (2022), CO Fluxes in Western Europe during 2017 - 2020 Winter Seasons Inverted by WRF-Chem/Data Assimilation Research Testbed with MOPITT Observations, [online] Available from: .
The study of anthropogenic carbon monoxide (CO) emissions is crucial to investigate anthropogenic activities. Assuming the anthropogenic CO emissions accounted for the super majority of the winter CO fluxes in western Europe, they could be roughly estimated by the inversion approach. The CO fluxes and concentrations of four consecutive winter seasons (i.e., DecemberFebruary) in western Europe since 2017 were estimated by a regional CO flux inversion system based on the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and the Data Assimilation Research Testbed (DART). The CO retrievals from the Measurements Of Pollution In The Troposphere instrument (MOPITT) version 8 level 2 multi-spectral Thermal InfraRed (TIR)/Near-InfraRed (NIR) CO retrieval data products were assimilated by the inversion system. The analyses of the MOPITT data used by the inversion system indicated that the mean averaging kernel row sums of the surface level was about 0.25, and the difference percentage of the surface-level retrievals relative to a priori CO-mixing ratios was 14.79%, which was similar to that of the other levels. These results suggested the MOPITT’s surface-level observations contained roughly the same amount of information as the other levels. The inverted CO fluxes of the four winter seasons were 6198.15 kilotons, 4939.72 kilotons, 4697.80 kilotons, and 5456.19 kilotons, respectively. Based on the assumption, the United Nations Framework Convention on Climate Change (UNFCCC) inventories were used to evaluate the accuracy of the inverted CO fluxes. The evaluation results indicated that the differences between the inverted CO fluxes and UNFCCC inventories of the three winter seasons of 20172019 were 13.36%, −4.59%, and −4.76%, respectively. Detailed surface-CO concentrations and XCO comparative analyses between the experimental results and the external Community Atmosphere Model with Chemistry (CAM-Chem) results and the MOPITT data were conducted. The comparative analysis results indicated that the experimental results of the winter season of 2017 were obviously affected by high boundary conditions. The CO concentrations results of the experiments were also evaluated by the CO observation data from Integrated Carbon Observation System (ICOS), the average Mean Bias Error (MBE), and the Root Mean Square Error (RMSE) between the CO concentrations results of the inversion system, and the ICOS observations were −22.43 ppb and 57.59 ppb, respectively. The MBE and RMSE of the inversion system were 17.53-ppb and 4.17-ppb better than those of the simulation-only parallel experiments, respectively.

Inness, A., I. Aben, M. Ades, T. Borsdorff, J. Flemming, L. Jones, J. Landgraf, B. Langerock, P. Nedelec, M. Parrington, and R. Ribas (2022), Assimilation of S5P/TROPOMI carbon monoxide data with the global CAMS near-real-time system, Atmospheric Chemistry and Physics, 22(21), 1435514376, doi:10.5194/acp-22-14355-2022.
The Tropospheric Monitoring Instrument (TROPOMI) on the Copernicus Sentinel 5 Precursor (S5P) satellite, launched in October 2017, provides a wealth of atmospheric composition data, including total columns of carbon monoxide (TCCO) at high horizontal resolution (5.5 km × 7 km). Near-real-time TROPOMI TCCO data have been monitored in the global data assimilation system of the Copernicus Atmosphere Monitoring Service (CAMS) since November 2018 to assess the quality of the data. The CAMS system already routinely assimilates TCCO data from the Measurement of Pollution in the Troposphere (MOPITT) instrument and the Infrared Atmospheric Sounding Interferometer (IASI) outside the polar regions.  The assimilation of TROPOMI TCCO data in the CAMS system was tested for the period 6 July to 31 December 2021, i.e. after the TROPOMI algorithm update to version 02.02.00 in July 2021. By assimilating TROPOMI TCCO observations, the CAMS CO columns increase by on average 8 %, resulting in an improved fit to independent observations (IAGOS aircraft profiles and NDACC Fourier transform infrared (FTIR) tropospheric and total-column CO data) compared to a version of the CAMS system where only TCCO from MOPITT and IASI is assimilated. The largest absolute and relative changes from the assimilation of TROPOMI CO are found in the lower and middle troposphere, i.e. that part of the atmosphere that is not already well constrained by the assimilated TIR MOPITT and IASI data. The largest impact near the surface comes from clear-sky TROPOMI data over land, and additional vertical information comes from the retrievals of measurements in cloudy conditions.  July and August 2021 saw record numbers of boreal wildfires over North America and Russia, leading to large amounts of CO being released into the atmosphere. The paper assesses the impact of TROPOMI CO assimilation on selected CO plumes more closely. While the CO column can be well constrained by the assimilation of TROPOMI CO data, and the fit to individual IAGOS CO profiles in the lower and middle troposphere is considerably improved, the TROPOMI CO columns do not provide further constraints on individual plumes that are transported across continents and oceans at altitudes above 500 hPa.

Jalali, A., K. A. Walker, K. Strong, R. R. Buchholz, M. N. Deeter, D. Wunch, S. Roche, T. Wizenberg, E. Lutsch, E. McGee, H. M. Worden, P. Fogal, and J. R. Drummond (2022), A comparison of carbon monoxide retrievals between the MOPITT satellite and Canadian high-Arctic ground-based NDACC and TCCON FTIR measurements, Atmospheric Measurement Techniques, 15(22), 68376863, doi:10.5194/amt-15-6837-2022.
Measurements of Pollution In The Troposphere (MOPITT) is an instrument on NASA’s Terra satellite that has measured tropospheric carbon monoxide (CO) from early 2000 to the present day. Validation of data from satellite instruments like MOPITT is often conducted using ground-based measurements to ensure the continued accuracy of the space-based instrument’s measurements and its scientific results. Previous MOPITT validation studies generally found a larger bias in the MOPITT data poleward of 60∘ N. In this study, we use data from 2006 to 2019 from the Bruker IFS 125HR Fourier Transform Infrared spectrometer (FTIR) located at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada, to validate the MOPITT version 8 (V8) retrievals. These comparisons utilize mid- and near-infrared FTIR measurements made as part of the Network for the Detection for Atmospheric Composition Change (NDACC) and the Total Carbon Column Observing Network (TCCON), respectively. All MOPITT version 8 retrievals within a radius of 110 km (1∘) from the PEARL Ridge Laboratory and within a 24 h time interval are used in this validation study. MOPITT retrieval products include those from the near-infrared (NIR) channel, the thermal infrared (TIR) channel, and a joint product from the thermal and near-infrared (TIRNIR) channels. Each channel’s detector has 4 pixels. We calculated the MOPITT pixel-to-pixel biases for each pixel, which were found to vary based on the season and surface type (land or water). The systematic bias for pixel 1 over land is larger than that for other pixels, which can reach up to 20 ppb. We use a small-region approximation method to find filtering criteria. We then apply the filters to the MOPITT dataset to minimize the MOPITT pixel bias and the number of outliers in the dataset. The sensitivity of each MOPITT pixel and each product is examined over the Canadian high Arctic. We then follow the methodologies recommended by NDACC and TCCON for the comparison between the FTIR and satellite total column retrievals. MOPITT averaging kernels are used to weight the NDACC and TCCON retrievals and take into account the different vertical sensitivities between the satellite and PEARL FTIR measurements. We use a modified Taylor diagram to present the comparison results from each pixel for each product over land and water with NDACC and TCCON measurements. Our results show overall consistency between MOPITT and the NDACC and TCCON measurements. When compared to the FTIR, the NIR MOPITT retrievals have a positive bias of 3 %10 % depending on the pixel. The bias values are negative for the TIR product, with values between −5 % and 0 %. The joint TIRNIR products show differences of −4 % to 7 %. The drift in MOPITT biases (in units of % yr−1) relative to NDACC and TCCON varies by MOPITT data product. In the NIR, drifts vs. TCCON are smaller than those vs. NDACC; however, this scenario is reversed for the MOPITT TIR and joint TIRNIR products. Overall, this study aims to provide detailed validation for MOPITT version 8 measurements in the Canadian high Arctic.

Kumar, R., C. He, P. Bhardwaj, F. Lacey, R. R. Buchholz, G. P. Brasseur, W. Joubert, C. Labuschagne, E. Kozlova, and T. Mkololo (2022), Assessment of regional carbon monoxide simulations over Africa and insights into source attribution and regional transport, Atmospheric Environment, 277, 119075, doi:10.1016/j.atmosenv.2022.119075.
This study assesses the quality of carbon monoxide (CO) simulations from the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and analyzes different processes controlling CO distribution in Africa. Sixteen CO tracers are implemented in WRF-Chem to track CO from different sources and regions. The model captures the seasonal cycles of surface temperature fairly well (r > 0.75 at most sites) and reproduces key features and variability of precipitation, wind speed, and planetary boundary layer height with errors typically seen in application of a regional model over such a large domain. The model also captures CO concentration hotspots and vertical gradients but underestimates the Measurements of Pollution in the Troposphere (MOPITT) retrieved total column with a larger underestimation in northern hemispheric Africa. The model also underestimates MOPITT and aircraft observed CO profiles throughout the troposphere. We discuss outdated anthropogenic emissions, low biomass burning emissions, and well-known low biases in global models of CO as potential contributors to the discrepancies between the regional model and MOPITT CO. Source contribution analysis of surface CO showed that all sources contribute to CO in Africa with anthropogenic emissions dominating in the urban regions, fire emissions dominating in central Africa, CO inflow from domain boundaries dominating in North Africa and the oceanic regions, and photochemical production dominance aligning with seasonal changes in sunlight. We also show that regional transport of CO emissions between African regions also play a very important role in controlling surface CO distribution in Africa. In some regions, more than 50% of the anthropogenic or biomass burning emitted CO comes from sources located outside those regions, highlighting the need for regional coordination and cooperation for air quality management in Africa.

Lutsch, E., D. Wunch, D. B. A. Jones, C. Clerbaux, J. W. Hannigan, T.-L. He, I. Ortega, S. Roche, K. Strong, and H. M. Worden (2022), Can the data assimilation of CO from MOPITT or IASI constrain high-latitude wildfire emissions? A Case Study of the 2017 Canadian Wildfires, Earth and Space Science Open Archive, doi:10.1002/essoar.10510875.1. [online] Available from: .
In this study, we examine the ability of the data assimilation of global satellite-based carbon monoxide (CO) observations to constrain high-latitude boreal wildfire emissions. We compare the optimiz

Marey, H. S., J. R. Drummond, D. B. A. Jones, H. Worden, M. N. Deeter, J. Gille, and D. Mao (2022), Analysis of improvements in MOPITT observational coverage over Canada, Atmospheric Measurement Techniques, 15(3), 701719, doi:10.5194/amt-15-701-2022.

Abstract. The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument has been measuring global tropospheric carbon monoxide (CO) since March 2000, providing the longest nearly continuous record of CO from space. During its long mission, the data processing algorithms have been updated to improve the quality of CO retrievals and the sensitivity to the lower troposphere. Currently, MOPITT retrievals are only performed for clear-sky observations or over low clouds for ocean scenes. The cloud detection scheme was modified in the new V9 product, resulting in an improvement in observational coverage, especially over land. Comparison of the spatial and seasonal variations of the data coverage in V9 and V8 shows differences with significant geographical and temporal variability, with some regions such as Canada and the Amazon exhibiting a doubling of data in winter. Here we conducted an analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) cloud heights and cloud mask products along with MOPITT retrieval cloud flag descriptors to understand the impact of cloud conditions on the MOPITT observational coverage, with a particular focus on observations over Canada. The MOPITT CO total column (TC) data were modified by turning off the cloud detection scheme to allow for a CO retrieval result, regardless of their cloud status. Analyses of the standard V8 CO TC product (cloud filtered) and non-standard product (non-cloud-masked) were conducted for selected days. Results showed some coherent structures that were observed frequently in the non-masked CO product that was not present in the V8 product and could potentially be actual CO features. Many times, these CO plumes were also seen in the Infrared Atmospheric Sounding Interferometer (IASI) CO TC product. The MODIS cloud height analysis revealed that a significant number of low-cloud CO retrievals were discarded in the V8 product. Most of the missed CO plumes in the V8 product are now detected in the new V9 product as a result of the dependence of the MOPITT radiance ratio (MRT) test over land. Comparisons of the MRT and MODIS cloud height data indicate a remarkable negative correlation. As a result of the modified V9 cloud detection algorithm, a significant portion of the low-cloud CO retrievals is now incorporated in the new V9 MOPITT product. Consequently, the observational coverage over Canada is significantly improved, which benefits analyses of regional CO variability, especially during extreme pollution events. We also conducted a comparison of MOPITT and IASI CO TC and found generally good agreement, with about a 5 %10 % positive bias that is more pronounced in highly polluted scenes.

Martínez-Alonso, S., M. N. Deeter, B. C. Baier, K. McKain, H. Worden, T. Borsdorff, C. Sweeney, and I. Aben (2022), Evaluation of MOPITT and TROPOMI carbon monoxide retrievals using AirCore in situ vertical profiles, Atmospheric Measurement Techniques, 15(16), 47514765, doi:10.5194/amt-15-4751-2022.

Abstract. AirCore in situ vertical profiles sample the atmosphere from near the surface to the lower stratosphere, making them ideal for the validation of satellite tropospheric trace gas data. Here we present intercomparison results of AirCore carbon monoxide (CO) measurements with respect to retrievals from MOPITT (Measurements of Pollution In The Troposphere; version 8) and TROPOMI (TROPOspheric Monitoring Instrument), on board the NASA Terra and ESA Sentinel 5-Precursor satellites, respectively. Mean MOPITT/AirCore total column bias values and their standard deviation (0.4 ± 5.5, 1.7 ± 5.6, and 0.7 ± 6.0 for MOPITT thermal-infrared, near-infrared, and multispectral retrievals, respectively; all in %) are similar to results obtained in MOPITT/NOAA aircraft flask data comparisons from this study and from previous validation efforts. MOPITT CO retrievals are systematically validated using in situ vertical profiles from a variety of aircraft campaigns. Because most aircraft vertical profiles do not sample the troposphere’s entire vertical extent, they must be extended upwards in order to be usable in validation. Here we quantify, for the first time, the error introduced in MOPITT CO validation by the use of shorter aircraft vertical profiles extended upwards by analyzing validation results of MOPITT with respect to full and truncated AirCore CO vertical profiles. Our results indicate that the error is small, affects mostly upper tropospheric retrievals (at 300 hPa: 2.6, 0.8, and 3.2 percent points for MOPITT thermal-infrared, near-infrared, and multispectral, respectively), and may have resulted in the overestimation of MOPITT retrieval biases in that region. TROPOMI can retrieve CO under both clear and cloudy conditions. The latter is achieved by quantifying interfering trace gases and parameters describing the cloud contamination of the measurements together with the CO column; then, the reference CO profiles used in the retrieval are scaled based on estimated above-cloud CO rather than on estimated total CO. We use AirCore measurements as the reference to evaluate the error introduced by this approach in cloudy TROPOMI retrievals over land after accounting for TROPOMI’s vertical sensitivity to CO (relative bias and its standard deviation = 2.02 % ± 11.13 %). We also quantify the null-space error, which accounts for differences between the shape of TROPOMI reference profiles and that of AirCore measured profiles (for TROPOMI cloudy enull=0.98 % ± 2.32 %).

Naus, S., L. G. Domingues, M. Krol, I. T. Luijkx, L. V. Gatti, J. B. Miller, E. Gloor, S. Basu, C. Correia, G. Koren, H. M. Worden, J. Flemming, G. Pétron, and W. Peters (2022), Sixteen years of MOPITT satellite data strongly constrain Amazon CO fire emissions, Atmospheric Chemistry and Physics, 22(22), 1473514750, doi:10.5194/acp-22-14735-2022.
Despite the consensus on the overall downward trend in Amazon forest loss in the previous decade, estimates of yearly carbon emissions from deforestation still vary widely. Estimated carbon emissions are currently often based on data from local logging activity reports, changes in remotely sensed biomass, and remote detection of fire hotspots and burned area. Here, we use 16 years of satellite-derived carbon monoxide (CO) columns to constrain fire CO emissions from the Amazon Basin between 2003 and 2018. Through data assimilation, we produce 3 d average maps of fire CO emissions over the Amazon, which we verified to be consistent with a long-term monitoring programme of aircraft CO profiles over five sites in the Amazon. Our new product independently confirms a long-term decrease of 54 % in deforestation-related CO emissions over the study period. Interannual variability is large, with known anomalously dry years showing a more than 4-fold increase in basin-wide fire emissions relative to wet years. At the level of individual Brazilian states, we find that both soil moisture anomalies and human ignitions determine fire activity, suggesting that future carbon release from fires depends on drought intensity as much as on continued forest protection. Our study shows that the atmospheric composition perspective on deforestation is a valuable additional monitoring instrument that complements existing bottom-up and remote sensing methods for land-use change. Extension of such a perspective to an operational framework is timely considering the observed increased fire intensity in the Amazon Basin between 2019 and 2021.

Peiro, H., S. Crowell, and B. Moore III (2022), Optimizing 4 years of CO2 biospheric fluxes from OCO-2 and in situ data in TM5: fire emissions from GFED and inferred from MOPITT CO data, Atmospheric Chemistry and Physics, 22(24), 1581715849, doi:10.5194/acp-22-15817-2022.
Column mixing ratio of carbon dioxide (CO2) data alone do not provide enough information for source attribution. Carbon monoxide (CO) is a product of inefficient combustion often co-emitted with CO2. CO data can then provide a powerful constraint on fire emissions, supporting more accurate estimation of biospheric CO2 fluxes. In this framework and using the chemistry transport model TM5, a CO inversion using Measurements of Pollution in The Troposphere (MOPITT) v8 data is performed to estimate fire emissions which are then converted into CO2 fire emissions (called FIREMo) through the use of the emission ratio. These optimized CO2 fire emissions are used to rebalance the CO2 net ecosystem exchange (NEEMo) and respiration (RhMo) with the global CO2 growth rate. Subsequently, in a second step, these rebalanced fluxes are used as priors for a CO2 inversion to derive the NEE and ocean fluxes constrained either by the Orbiting Carbon Observatory 2 (OCO-2) v9 or by in situ (IS) CO2 data. For comparison purpose, we also balanced the respiration using fire emissions from the Global Fire Emissions Database (GFED) version 3 (GFED3) and version 4.1s (GFED4.1s). We hence study the impact of CO fire emissions in our CO2 inversions at global, latitudinal, and regional scales over the period 20152018 and compare our results to the two other similar approaches using GFED3 (FIRE3) and GFED4.1s (FIRE4) fires, as well as with an inversion using both CarnegieAmesStanford Approach (CASA)-GFED3 NEE and GFED3 fire priors (priorCMS). After comparison at the different scales, the inversions are evaluated against Total Carbon Column Observing Network (TCCON) data. Comparison of the flux estimates shows that at the global scale posterior net flux estimates are more robust than the different prior flux estimates. However, at the regional scale, we can observe differences in fire emissions among the priors, resulting in differences among the NEE prior emissions. The derived NEE prior emissions are rebalanced in concert with the fires. Consequently, the differences observed in the NEE posterior emissions are a result of the balancing with fires and the constraints provided by CO2 observations. Tropical net flux estimates from in situ inversions are highly sensitive to the prior flux assumed, of which fires are a significant component. Slightly larger net CO2 sources are derived with posterior fire emissions using either FIRE4 or FIREMo in the OCO-2 inversion, in particular for most tropical regions during the 2015 El Niño year. Similarly, larger net CO2 sources are also derived with posterior fire emissions in the in situ data inversion for Tropical Asia. Evaluation with CO2 TCCON data shows lower biases with the three rebalanced priors than with the prior using CASA-GFED3. However, posteriors have average bias and scatter very close each other, making it difficult to conclude which simulation performs better than the other. We observe that the assimilated CO2 data have a strong influence on the global net fluxes among the different inversions. Inversions using OCO-2 (or IS) data have similar emissions, mostly as a result of the observational constraints and to a lesser extent because of the fire prior used. But results in the tropical regions suggest net flux sensitivity to the fire prior for both the IS and OCO-2 inversions. Further work is needed to improve prior fluxes in tropical regions where fires are a significant component. Finally, even if the inversions using the FIREMo prior did enhance the biases over some TCCON sites, it is not the case for the majority of TCCON sites. This study consequently pushes forward the development of a COCO2 joint inversion with multi-observations for a possible stronger constraint on posterior CO2 fire and biospheric emissions.

Qu, Z., D. K. Henze, H. M. Worden, Z. Jiang, B. Gaubert, N. Theys, and W. Wang (2022), Sector-Based Top-Down Estimates of NOx, SO2, and CO Emissions in East Asia, Geophysical Research Letters, 49(2), e2021GL096009, doi:10.1029/2021GL096009.
Top-down estimates using satellite data provide important information on the sources of air pollutants. We develop a sector-based 4D-Var framework based on the GEOS-Chem adjoint model to address the impacts of co-emissions and chemical interactions on top-down emission estimates. We apply OMI NO2, OMI SO2, and MOPITT CO observations to estimate NOx, SO2, and CO emissions in East Asia during 20052012. Posterior evaluations with surface measurements show reduced normalized mean bias (NMB) by 7% (NO2)15% (SO2) and normalized mean square error (NMSE) by 8% (SO2)9% (NO2) compared to a species-based inversion. This new inversion captures the peak years of Chinese SO2 (2007) and NOx (2011) emissions and attributes their drivers to industry and energy activities. The CO peak in 2007 in China is driven by residential and industry emissions. In India, the inversion attributes NOx and SO2 trends mostly to energy and CO trend to residential emissions.

Rahman, M. M., W. Shuo, W. Zhao, X. Xu, W. Zhang, and A. Arshad (2022), Investigating the Relationship between Air Pollutants and Meteorological Parameters Using Satellite Data over Bangladesh, Remote Sensing, 14(12), 2757, doi:10.3390/rs14122757.
Understanding of the relationship between air pollutants and meteorological parameters on the regional scale is a prerequisite for setting up air pollution prevention and control strategies; however, there is a lack of methodical investigations, particularly in the context of Bangladesh’s deficiency of information on air pollution. This study represents the first attempt to investigate the relationship between air pollutants (NO2, O3, SO2, and CO) and meteorological parameters over Bangladesh using satellite data (OMI and MOPITT) during the period from 2015 to 2020. Geographically weighted regression (GWR) modelling was utilized to assess the relationship between air pollutants and weather variables. The spatial representation and average values of geographically varying coefficients showed that the column densities of air pollutants were affected by the meteorological parameters. For example, NO2 was positively associated with temperature in most of the studied regions, with an average geographically varying coefficient value of 0.12 Dobson units (DU, 1 DU = 2.687 × 1016 molecules/cm2), indicating that NO2 concentrations increase by 0.12 DU/year with every unit increase in temperature. The sources of NO2 and SO2 in Dhaka were identified through emission inventory analysis, and transportation and industry emissions were the most significant influencing factors for NO2 and SO2, respectively. Temperature and pressure showed a higher degree of relationship with all four air pollutants compared with other parameters. The results and discussion presented in this study can be of benefit for policy makers in developing air pollution control strategies in Bangladesh.

Smoydzin, L., and P. Hoor (2022), Contribution of Asian emissions to upper tropospheric CO over the remote Pacific, Atmospheric Chemistry and Physics, 22(11), 71937206, doi:10.5194/acp-22-7193-2022.

Abstract. Upon analysing the global distribution of the highest 2 % of daily CO mixing ratios at 400 hPa derived from the MOPITT satellite instrument for 20 years (20002019), we very regularly detect regions with very high CO values (i.e. mixing ratios belonging to the globally highest 2 %) over the remote Northern Hemispheric (NH) Pacific. Such events of elevated CO over the upper tropospheric NH Pacific occur throughout the year with surprisingly high regularity and frequency (70 % of all days during winter, 80 % of all days during spring). During winter, most of these pollution events are detected over the north-eastern and central NH Pacific, during spring over the central NH Pacific, and during summer over the western NH Pacific. We detect most pollution events during spring.

To link each individual pollution event detected by the 2 % filtering method with a specific CO source region, we perform trajectory calculations using MPTRAC, a Lagrangian transport model. To analyse transport pathways and uplift mechanisms, we combine MOPITT data, the trajectory calculations, and ERA-Interim reanalysis data. It becomes apparent that air masses from China that are lifted along a frontal system into the free troposphere are the major CO source throughout the year. The contributions of other source regions and uplift mechanisms show a strong seasonal cycle: NE Asia in combination with upward transport of air masses in the warm conveyor belt of a midlatitude cyclone is a significant CO source region during winter, spring, and summer, while India is an important source region mainly during spring and summer and SE Asia mainly during spring.

Tang, Z., J. Chen, and Z. Jiang (2022), Discrepancy in assimilated atmospheric CO over East Asia in 20152020 by assimilating satellite and surface CO measurements, Atmospheric Chemistry and Physics, 22(11), 78157826, doi:10.5194/acp-22-7815-2022.

Abstract. Satellite and surface carbon monoxide (CO) observations have been widely used to investigate the sources and variabilities of atmospheric CO. However, comparative analyses to explore the effects of satellite and surface measurements on atmospheric CO assimilations are still lacking. Here we investigate the assimilated atmospheric CO over East Asia in 20152020, via assimilating CO measurements from the Measurement of Pollution in the Troposphere (MOPITT) instrument and Ministry of Ecology and Environment of China (MEE) monitoring network. We find noticeable inconsistencies in the assimilations: the adjusted CO columns (Xco) are about 162, 173 and 172 ppb by assimilating surface CO measurements, in contrast to 138144, 149155 and 144151 ppb by assimilating MOPITT CO observations over East China, the North China Plain (NCP), and the Yangtze River Delta (YRD), respectively. These inconsistencies could be associated with possible representation errors due to differences between urban and regional CO backgrounds. Furthermore, the adjusted surface CO concentrations are about 631, 806, and 657 ppb by assimilating surface CO measurements, in contrast to 418427, 627639 and 500509 ppb by assimilating MOPITT CO observations over East China, NCP, and YRD, respectively; assimilations of normalized surface CO measurements (to mitigate the influences of representation errors) indicate declines of CO columns by about 2.2, 2.1, and 1.8 ppb yr−1, in contrast to 0.630.86, 0.971.29, and 1.01.27 ppb yr−1 by assimilating MOPITT CO measurements over East China, South Korea, and Japan, respectively. These discrepancies reflect the different vertical sensitivities of satellite and surface observations in the lower and free troposphere. This work demonstrates the importance of integrating information from satellite and surface measurements to provide a more accurate evaluation of atmospheric CO changes.

Wang, Y., Q. Yuan, S. Zhou, and L. Zhang (2022), Global spatiotemporal completion of daily high-resolution TCCO from TROPOMI over land using a swath-based local ensemble learning method, ISPRS Journal of Photogrammetry and Remote Sensing, 194, 167180, doi:10.1016/j.isprsjprs.2022.10.012.
At present, the daily global Total Column carbon monoxide (CO) (TCCO) product from TROPOMI is performed at the highest spatial resolution, which has been broadly adopted in atmospheric CO-related researches. Unfortunately, missing data emerges in the TROPOMI TCCO and the studies for the recovery of its missing pixels on a globe-scale are scarce. To address this issue, we develop a novel framework to recover missing data in global TROPOMI TCCO product over land from Jun. 01, 2018 to May. 31, 2021 by fusing multisource data. A finely devised Swath-based Local Ensemble Learning (SLEL) method is proposed due to the spatiotemporal discrepancy of missing pixels. In our study, three validation schemes are employed, including a Cross-Validation technique for each swath, in-situ validation against NDACC and TCCON, and transverse comparison with MOPITT and CAMS TCCO products. Validation results show that the developed framework presents an expected accuracy for recovering missing data in each swath, with daily average R and MB fluctuating around 0.9 and 0 mol/m2, respectively. Meanwhile, the accuracy of recovered results is satisfactory and close to that of TROPOMI, with the R of 0.885 against NDACC and 0.918 against TCCON. Furthermore, the recovered results achieve a small (distinctly) better performance than those of MOPITT (CAMS). The spatial pattern of the recovered TCCO is consistent with that of the MOPITT TCCO and can specify much finer spatial details by comparison with CAMS. As for daily examples, the SLEL method well recovers the missing pixels in global TROPOMI TCCO with rich spatial details, even for some critical missing cases. Seasonal variations of global CO spatial patterns are also clearly captured in our results. The daily full-coverage high-resolution (0.07°) TCCO can help obtain spatiotemporally continuous global changes of CO and support related researches, which is accessible on

Worden, H. M., G. L. Francis, S. S. Kulawik, K. W. Bowman, K. Cady-Pereira, D. Fu, J. D. Hegarty, V. Kantchev, M. Luo, V. H. Payne, J. R. Worden, R. Commane, and K. McKain (2022), TROPESS/CrIS carbon monoxide profile validation with NOAA GML and ATom in situ aircraft observations, Atmospheric Measurement Techniques, 15(18), 53835398, doi:10.5194/amt-15-5383-2022.

Abstract. The new single-pixel TROPESS (TRopospheric Ozone and its Precursors from Earth System Sounding) profile retrievals of carbon monoxide (CO) from the Cross-track Infrared Sounder (CrIS) are evaluated using vertical profiles of in situ observations from the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory (GML) aircraft program and from the Atmospheric Tomography Mission (ATom) campaigns. The TROPESS optimal estimation retrievals are produced using the MUSES (MUlti-SpEctra, MUlti-SpEcies, MUlti-Sensors) algorithm, which has heritage from retrieval algorithms developed for the EOS/Aura Tropospheric Emission Spectrometer (TES). TROPESS products provide retrieval diagnostics and error covariance matrices that propagate instrument noise as well as the uncertainties from sequential retrievals of parameters such as temperature and water vapor that are required to estimate the carbon monoxide profiles. The validation approach used here evaluates biases in column and profile values as well as the validity of the retrieval error estimates using the mean and variance of the compared satellite and aircraft observations. CrISNOAA GML comparisons had biases of 0.6 % for partial column average volume mixing ratios (VMRs) and (2.3, 0.9, −4.5) % for VMRs at (750, 511, 287) hPa vertical levels, respectively, with standard deviations from 9 % to 14 %. CrISATom comparisons had biases of −0.04 % for partial column and (2.2, 0.5, −3.0) % for (750, 511, 287) hPa vertical levels, respectively, with standard deviations from 6 % to 10 %. The reported observational errors for TROPESS/CrIS CO profiles have the expected behavior with respect to the vertical pattern in standard deviation of the comparisons. These comparison results give us confidence in the use of TROPESS/CrIS CO profiles and error characterization for continuing the multi-decadal record of satellite CO observations.


Buchholz, R. R., H. M. Worden, M. Park, G. Francis, M. N. Deeter, D. P. Edwards, L. K. Emmons, B. Gaubert, J. Gille, S. Martínez-Alonso, W. Tang, R. Kumar, J. R. Drummond, C. Clerbaux, M. George, P.-F. Coheur, D. Hurtmans, K. W. Bowman, M. Luo, V. H. Payne, J. R. Worden, M. Chin, R. C. Levy, J. Warner, Z. Wei, and S. S. Kulawik (2021), Air pollution trends measured from Terra: CO and AOD over industrial, fire-prone, and background regions, Remote Sensing of Environment, 256, 112275, doi:10.1016/j.rse.2020.112275.
Following past studies to quantify decadal trends in global carbon monoxide (CO) using satellite observations, we update estimates and find a CO trend in column amounts of about −0.50 % per year between 2002 to 2018, which is a deceleration compared to analyses performed on shorter records that found −1 % per year. Aerosols are co-emitted with CO from both fires and anthropogenic sources but with a shorter lifetime than CO. A combined trend analysis of CO and aerosol optical depth (AOD) measurements from space helps to diagnose the drivers of regional differences in the CO trend. We use the long-term records of CO from the Measurements of Pollution in the Troposphere (MOPITT) and AOD from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. Other satellite instruments measuring CO in the thermal infrared, AIRS, TES, IASI, and CrIS, show consistent hemispheric CO variability and corroborate results from the trend analysis performed with MOPITT CO. Trends are examined by hemisphere and in regions for 2002 to 2018, with uncertainties quantified. The CO and AOD records are split into two sub-periods (2002 to 2010 and 2010 to 2018) in order to assess trend changes over the 16 years. We focus on four major population centers: Northeast China, North India, Europe, and Eastern USA, as well as fire-prone regions in both hemispheres. In general, CO declines faster in the first half of the record compared to the second half, while AOD trends show more variability across regions. We find evidence of the atmospheric impact of air quality management policies. The large decline in CO found over Northeast China is initially associated with an improvement in combustion efficiency, with subsequent additional air quality improvements from 2010 onwards. Industrial regions with minimal emission control measures such as North India become more globally relevant as the global CO trend weakens. We also examine the CO trends in monthly percentile values to understand seasonal implications and find that local changes in biomass burning are sufficiently strong to counteract the global downward trend in atmospheric CO, particularly in late summer.

Deeter, M. N., D. Mao, S. Martínez-Alonso, H. M. Worden, M. O. Andreae, and H. Schlager (2021a), Impacts of MOPITT cloud detection revisions on observation frequency and mapping of highly polluted scenes, Remote Sensing of Environment, 262, 112516, doi:10.1016/j.rse.2021.112516.
Measurements made by the MOPITT (“Measurements of Pollution in the Troposphere”) instrument on the NASA Terra polar-orbiting platform enable the retrieval of tropospheric carbon monoxide (CO) concentrations. As determined by the Terra orbit and MOPITT swath width, the frequency of MOPITT observations at a specific location, or measurement sampling frequency, is typically about once every three to four days. However, because the MOPITT retrieval algorithm is only applicable to clear-sky scenes, MOPITT retrieval sampling frequency strongly depends on regional cloudiness and can be much smaller than the measurement sampling frequency. Moreover, highly polluted scenes, characterized by high aerosol optical depths, can be confused with cloudy scenes and thus be discarded unnecessarily by the MOPITT cloud detection algorithm. Herein are described revisions to this algorithm which substantially increase retrieval sampling over land in varying pollution conditions. The performance of the revised cloud detection algorithm is evaluated through validation, case studies, and continental-scale maps of retrieval sampling frequency. Presented case studies illustrate (1) why the current operational MOPITT cloud detection algorithm excludes extended areas of potentially valuable cloud-free MOPITT observations and (2) how, for the same scenes, improved retrieval coverage benefits analyses of regional CO variability. Maps of retrieval sampling frequency for South America and Asia exhibit well-defined improvements, especially in regions with poor sampling frequency in the current product.

Deeter, M. N., D. Mao, S. Martinez-Alonso, H. M. Worden, M. O. Andreae, and H. Schlager (2021b), Impacts of MOPITT cloud detection revisions on observation frequency and mapping of highly polluted scenes, Remote Sens. Environ., 262, 112516, doi:10.1016/j.rse.2021.112516.
Measurements made by the MOPITT (“Measurements of Pollution in the Troposphere”) instrument on the NASA Terra polar-orbiting platform enable the retrieval of tropospheric carbon monoxide (CO) concentrations. As determined by the Terra orbit and MOPITT swath width, the frequency of MOPITT observations at a specific location, or measurement sampling frequency, is typically about once every three to four days. However, because the MOPITT retrieval algorithm is only applicable to clear-sky scenes, MOPITT retrieval sampling frequency strongly depends on regional cloudiness and can be much smaller than the measurement sampling frequency. Moreover, highly polluted scenes, characterized by high aerosol optical depths, can be confused with cloudy scenes and thus be discarded unnecessarily by the MOPITT cloud detection algorithm. Herein are described revisions to this algorithm which substantially increase retrieval sampling over land in varying pollution conditions. The performance of the revised cloud detection algorithm is evaluated through validation, case studies, and continental-scale maps of retrieval sampling frequency. Presented case studies illustrate (1) why the current operational MOPITT cloud detection algorithm excludes extended areas of potentially valuable cloud-free MOPITT observations and (2) how, for the same scenes, improved retrieval coverage benefits analyses of regional CO variability. Maps of retrieval sampling frequency for South America and Asia exhibit well-defined improvements, especially in regions with poor sampling frequency in the current product.

Fortems-Cheiney, A., I. Pison, G. Broquet, G. Dufour, A. Berchet, E. Potier, A. Coman, G. Siour, and L. Costantino (2021), Variational regional inverse modeling of reactive species emissions with PYVAR-CHIMERE-v2019, Geosci. Model Dev., 14(5), 29392957, doi:10.5194/gmd-14-2939-2021.
Up-to-date and accurate emission inventories for air pollutants are essential for understanding their role in the formation of tropospheric ozone and particulate matter at various temporal scales, for anticipating pollution peaks and for identifying the key drivers that could help mitigate their concentrations. This paper describes the Bayesian variational inverse system PYVAR-CHIMERE, which is now adapted to the inversion of reactive species. Complementarily with bottom-up inventories, this system aims at updating and improving the knowledge on the high spatiotemporal variability of emissions of air pollutants and their precursors. The system is designed to use any type of observations, such as satellite observations or surface station measurements. The potential of PYVAR-CHIMERE is illustrated with inversions of both carbon monoxide (CO) and nitrogen oxides (NOx) emissions in Europe, using the MOPITT and OMI satellite observations, respectively. In these cases, local increments on CO emissions can reach more than +50 %, with increases located mainly over central and eastern Europe, except in the south of Poland, and decreases located over Spain and Portugal. The illustrative cases for NOx emissions also lead to large local increments (> 50 %), for example over industrial areas (e.g., over the Po Valley) and over the Netherlands. The good behavior of the inversion is shown through statistics on the concentrations: the mean bias, RMSE, standard deviation, and correlation between the simulated and observed concentrations. For CO, the mean bias is reduced by about 27% when using the posterior emissions, the RMSE and the standard deviation are reduced by about 50 %, and the cor-relation is strongly improved (0.74 when using the posterior emissions against 0.02); for NOx, the mean bias is reduced by about 24% and the RMSE and the standard deviation are reduced by about 7 %, but the correlation is not improved. We reported strong non-linear relationships between NOx emissions and satellite NO2 columns, now requiring a fully comprehensive scientific study.

Hedelius, J. K., G. C. Toon, R. R. Buchholz, L. T. Iraci, J. R. Podolske, C. M. Roehl, P. O. Wennberg, H. M. Worden, and D. Wunch (2021), Regional and Urban Column CO Trends and Anomalies as Observed by MOPITT Over 16 Years, Journal of Geophysical Research: Atmospheres, 126(5), e2020JD033967, doi:
Atmospheric carbon monoxide (CO) concentrations have decreased since the beginning of the century, and the rate of decrease depends on the region. Depending on how regions are chosen, their boundaries may not always align with where there are differences in trends. To address this, we calculate trends within 0.4° × 0.4° grid cells independently throughout the globe using satellite CO retrievals from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument from 2002 to 2017. These trends are found with the caveat that there are large singular biomass burning events somewhere nearly every year, and we include examples of large column CO anomalies during sporadic but large burning events in the North American and Eurasian boreal forests, the Amazon, Africa, and Indonesia. CO trends behave similarly within regions that span about a few thousand kilometers. Using TransCom region definitions, we find average trends between −0.9 and 0.1 ppb year−1 (about −0.9 to 0.1% year−1) for 20022017. Over 5-year subsets, trends in TransCom regions vary between −3.6 and 1.8 ppb year−1. This substantial spatial and temporal variability in trends is in agreement with other studies. With an understanding of regional trends, we compare with trends from urban areas. Generally, CO trends within urban areas are indistinguishable from regional trends. This may be because of a combination of noise in the data, the large footprint for MOPITT, or because anthropogenic CO reduction measures were implemented before the MOPITT record began. We provide case studies for a few cities, such as Los Angeles, and find long-term variation in the rate of change of column CO.

Jeong, U., and H. Hong (2021), Comparison of Total Column and Surface Mixing Ratio of Carbon Monoxide Derived from the TROPOMI/Sentinel-5 Precursor with In-Situ Measurements from Extensive Ground-Based Network over South Korea, Remote Sens., 13(19), 3987, doi:10.3390/rs13193987.
Atmospheric carbon monoxide (CO) significantly impacts climate change and human health, and has become the focus of increased air quality and climate research. Since 2018, the Troposphere Monitoring Instrument (TROPOMI) has provided total column amounts of CO (C-TROPOMI) with a high spatial resolution to monitor atmospheric CO. This study compared and assessed the accuracy of C-TROPOMI measurements using surface in-situ measurements (S-KME) obtained from an extensive ground-based network over South Korea, where CO level is persistently affected by both local emissions and trans-boundary transport. Our analysis reveals that the TROPOMI effectively detected major emission sources of CO over South Korea and efficiently complemented the spatial coverage of the ground-based network. In general, the correlations between C-TROPOMI and S-KME were lower than those for NO2 reported in a previous study, and this discrepancy was partly attributed to the lower spatiotemporal variability. Moreover, vertical CO profiles were sampled from the ECMWF CAMS reanalysis data (EAC4) to convert C-TROPOMI to surface mixing ratios (S-TROPOMI). S-TROPOMI showed a significant underestimation compared with S-KME by approximately 40%, with a moderate correlation of approximately 0.51. The low biases of S-TROPOMI were more significant during the winter season, which was mainly attributed to the underestimation of the EAC4 CO at the surface. This study can contribute to the assessment of satellite and model data for monitoring surface air quality and greenhouse gas emissions.

Khade, V., S. M. Polavarapu, M. Neish, P. L. Houtekamer, D. B. A. Jones, S.-J. Baek, T.-L. He, and S. Gravel (2021), The Environment and Climate Change Canada Carbon Assimilation System (EC-CAS v1.0): demonstration with simulated CO observations, Geoscientific Model Development, 14(5), 25252544, doi:10.5194/gmd-14-2525-2021.

Abstract. In this study, we present the development of a new coupled weather and carbon monoxide (CO) data assimilation system based on the Environment and Climate Change Canada (ECCC) operational ensemble Kalman filter (EnKF). The estimated meteorological state is augmented to include CO. Variable localization is used to prevent the direct update of meteorology by the observations of the constituents and vice versa. Physical localization is used to damp spurious analysis increments far from a given observation. Perturbed surface flux fields are used to account for the uncertainty in CO due to errors in the surface fluxes. The system is demonstrated for the estimation of three-dimensional CO states using simulated observations from a variety of networks. First, a hypothetically dense, uniformly distributed observation network is used to demonstrate that the system is working. More realistic observation networks, based on surface hourly observations, and space-based observations provide a demonstration of the complementarity of the different networks and further confirm the reasonable behavior of the coupled assimilation system. Having demonstrated the ability to estimate CO distributions, this system will be extended to estimate surface fluxes in the future.

Park, M., H. M. Worden, D. E. Kinnison, B. Gaubert, S. Tilmes, L. K. Emmons, M. L. Santee, L. Froidevaux, and C. D. Boone (2021), Fate of Pollution Emitted During the 2015 Indonesian Fire Season, J. Geophys. Res.-Atmos., 126(9), e2020JD033474, doi:10.1029/2020JD033474.
The El Nino-driven fire season in Indonesia in September-October 2015 produced the largest fire emissions on record since NASA’s EOS satellites started making observations of tropospheric pollutants from space. In this study, measurements of carbon monoxide (CO) from the Measurement of Pollution in the Troposphere (MOPITT) on Terra and the Microwave Limb Sounder are used to characterize the anomalously high CO emitted during the 2015 Indonesian fire season transported into the tropical upper troposphere and stratosphere. The satellite measurements indicate that CO emitted from wildfires was transported into the upper troposphere with time lags up to similar to 2 months and continued to be transported into the stratosphere, which resulted in higher concentrations of CO extending up to similar to 20 hPa by the end of 2016. Hydrogen cyanide (HCN) measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) confirms that anomalously high HCN emitted from the same wildfires was also transported into the tropical stratosphere and persisted throughout 2017. Simulations of CO from the Community Atmosphere Model with Chemistry (CAM-chem) show a significant increase in CO concentrations in the troposphere in October 2015. However, comparisons between CAM-chem and MOPITT CO suggest that the model underestimates the amount of CO even with doubled emissions of CO in October 2015. Both the satellite measurements and the model simulations show that the pollution emitted from the wildfires over Indonesia was transported to and persisted in the tropical stratosphere much longer than the previous El-Nino driven fire events due to unprecedented amount of the fire emissions.

Pouyaei, A., B. Sadeghi, Y. Choi, J. Jung, A. H. Souri, C. Zhao, and C. H. Song (2021), Development and Implementation of a Physics-Based Convective Mixing Scheme in the Community Multiscale Air Quality Modeling Framework, J. Adv. Model. Earth Syst., 13(6), e2021MS002475, doi:10.1029/2021MS002475.
To improve the representation of convective mixing of atmospheric pollutants in the presence of clouds, we developed a convection module based on Kain and Fritsch (KF) method and implemented it in the Community Multiscale Air Quality model. The KF-convection method is a mass-flux-based model that accounts for updraft flux, downdraft flux, entrainment, detrainment, and the subsidence effect. The method is consistent with the convection parametrization of the meteorology model. We apply the KF-convection model to an idealized case and to a reference setup prepared for East Asia during the KORUS-AQ campaign period to investigate its impact on carbon monoxide (CO) concentration at various atmospheric altitudes. We investigate the impact of KF-convection on the horizontal distribution of CO concentrations by comparing it to aircraft measurements and the MOPITT CO column. We further discuss two types of impacts of KF-convection: the direct impact caused by vertical movement of CO concentrations by updraft or downdraft and the indirect impact caused by transport of lifted CO concentrations to another region. May 12 saw a high indirect impact originating from the Shanghai region at higher altitudes and a high direct impact of updraft fluxes at 1 km altitude. However, May 26 revealed an immense updraft increasing higher altitude concentrations (up to 40 ppbv) and diverse indirect impacts over the region of the study (+/- 50 ppbv). The overall comparison shows a strong connection between differences in the amount of concentration caused by the direct impact at each altitude with the presence of an updraft at that altitude. The developed model can be employed in large domains (i.e., East Asia, Europe, North America, and Northern Hemisphere) with sub-grid scale cloud modeling to include the impacts of convection.

Sekiya, T., K. Miyazaki, K. Ogochi, K. Sudo, M. Takigawa, H. Eskes, and K. F. Boersma (2021), Impacts of Horizontal Resolution on Global Data Assimilation of Satellite Measurements for Tropospheric Chemistry Analysis, J. Adv. Model. Earth Syst., 13(6), e2020MS002180, doi:10.1029/2020MS002180.
We present the results from a global 0.56 degrees-resolution chemical data assimilation that integrates satellite observations of ozone, NO2, CO, HNO3, and SO2 from OMI, GOME-2, SCIAMACHY, TES, MOPITT, and MLS. The assimilation is based on an ensemble Kalman filter technique and simultaneously optimizes ozone precursor emissions and concentrations of various species. The data assimilation at 0.56 degrees resolution reduced model errors against independent surface, aircraft, and ozonesonde observations, which was larger than at coarser resolutions for many cases. By the data assimilation, surface model errors over major polluted regions were reduced by 33%-75% for NO2 and by 15%-18% for ozone. Agreements against assimilated observations for NO2 were improved using the data assimilation at 0.56 degrees resolution by a factor of 1.5-3 compared to 2.8 degrees resolution over major polluted regions. The estimated global total NOx emission over medium and strong source areas were smaller by 15% at 0.56 degrees resolution than at 2.8 degrees resolution associated with resolving small-scale transport and chemistry processes, while 2%-26% smaller emissions were found for regional total emissions over Europe, the United States, China, India, and South Africa, with larger differences over megacities such as Los Angeles (-41%). The estimated ship emissions were 5%-7% smaller at 0.56 degrees resolution over the Pacific and Atlantic. The 0.56 degrees-resolution data assimilation provides globally consistent analyses of the emissions and concentrations on a megacity scale, which benefit studies on air quality and its impact on human health at various spatial scales over different regions of the world.

Sicard, P., P. Crippa, A. De Marco, S. Castruccio, P. Giani, J. Cuesta, E. Paoletti, Z. Feng, and A. Anav (2021), High spatial resolution WRF-Chem model over Asia: Physics and chemistry evaluation, Atmospheric Environment, 244, 118004, doi:10.1016/j.atmosenv.2020.118004.
The representation of air quality and meteorology over Asia remains challenging for chemical transport models as a result of the complex interactions between the East Asian monsoons and the large uncertainty (in space and time) of the high anthropogenic emissions levels over the region. High spatial resolution models allow resolving small-scale features induced by the complex topography of this region. In this study, the Weather Research and Forecasting model with Chemistry (WRF-Chem) was used to simulate the spatial and seasonal variability of main physical and chemical variables over Asia for the year 2015 at 8-km horizontal resolution to enable resolving small-scale features induced by the region complex topography. The simulated atmospheric composition was evaluated against satellite retrievals (MOPITT, IASI + GOME2, MODIS and OMI) in addition to ground-based observations in China for the year 2015, while the meteorological variables were evaluated by several observational-based datasets (ERA5, CRU, MODIS, MTE). Results showed low to moderate seasonal biases for major meteorological variables, i.e. air temperature, relative humidity, precipitation, latent heat, sensible heat and snow cover fraction. Overall, WRF-Chem reproduced well the spatial and seasonal variability of lowermost tropospheric ozone content, total column carbon monoxide and aerosol optical depth, while large discrepancies were found for tropospheric nitrogen dioxide content, mainly during the warm season. In consistency with previous studies, the different biases between model-simulated and satellite-retrieved values can be mainly attributed to i) the large uncertainties in anthropogenic and natural nitrogen oxides emission estimates, as well as dust and sea salt emissions in the case of aerosol optical depth, and ii) some coarse parameterizations used to reproduce main small-scale features (e.g. meteorology, chemical processes, dry deposition to vegetation). Compared to ground-based observations, the WRF-Chem model reproduced well the mean annual cycle of surface nitrogen dioxide, ozone and fine particles concentrations in all seasons across China. Our results suggest that WRF-Chem provides reliable spatio-temporal patterns for most of the meteorological and chemical variables, adding thus confidence to its applicability in the context of air pollution risk assessment to human and ecosystems health.

Wang, S., J. B. Cohen, W. Deng, K. Qin, and J. Guo (2021), Using a New Top-Down Constrained Emissions Inventory to Attribute the Previously Unknown Source of Extreme Aerosol Loadings Observed Annually in the Monsoon Asia Free Troposphere, Earth Future, 9(7), e2021EF002167, doi:10.1029/2021EF002167.
The contribution of biomass burning to the total aerosol loading over Monsoon Asia is both significant and continuing to increase. To better match the spatio-temporal distribution of aerosols and trace gasses observed in the free troposphere, this work applied a 3-D constrained emission inventory based on top-down remotely sensed NO2 measurement to investigate the most extreme of the annually occurring biomass burning seasons in Monsoon Asia. In 2016, this constituted an extreme event observed over a 6-day period covering millions of square kilometers, including over regions that are typically in the rainy phase of the Asian Monsoon. The results are shown to be consistent with respect to Tropical Rainfall Measuring Mission precipitation, AERONET measurements, MODIS AOD, MOPITT CO, and reanalysis meteorology, over both the biomass burning source as well as the millions of square kilometers downwind both to the East and to the Southwest. Reproducing the observed long-range transport pattern requires the time of biomass burning to be increased, regions not previously identified as burning to be actual source regions, and the emissions of Black Carbon (BC) to be 6.6 to 11.9 times larger than current inventories. The underlying mechanism for this long-range transport involves a new 3-D pathway that can occur during the transition from the North phase to the South phase of the Asian Monsoon. The results are also consistent with the new idea that large loadings of BC in the lower free troposphere may significantly affect the meteorological field and the overall vertical distribution of aerosols in the tropical troposphere.

Worden, J., S. Saatchi, M. Keller, A. A. Bloom, J. Liu, N. Parazoo, J. B. Fisher, K. Bowman, J. T. Reager, K. Fahy, D. Schimel, R. Fu, S. Worden, Y. Yin, P. Gentine, A. G. Konings, G. R. Quetin, M. Williams, H. Worden, M. Shi, and A. Barkhordarian (2021), Satellite Observations of the Tropical Terrestrial Carbon Balance and Interactions With the Water Cycle During the 21st Century, Reviews of Geophysics, 59(1), e2020RG000711, doi:10.1029/2020RG000711.
Abstract A constellation of satellites is now in orbit providing information about terrestrial carbon and water storage and fluxes. These combined observations show that the tropical biosphere has changed significantly in the last 2 decades from the combined effects of climate variability and land use. Large areas of forest have been cleared in both wet and dry forests, increasing the source of carbon to the atmosphere. Concomitantly, tropical fire emissions have declined, at least until 2016, from changes in land-use practices and rainfall, increasing the net carbon sink. Measurements of carbon stocks and fluxes from disturbance and recovery and of vegetation photosynthesis show significant regional variability of net biosphere exchange and gross primary productivity across the tropics and are tied to seasonal and interannual changes in water fluxes and storage. Comparison of satellite based estimates of evapotranspiration, photosynthesis, and the deuterium content of water vapor with patterns of total water storage and rainfall demonstrate the presence of vegetation-atmosphere interactions and feedback mechanisms across tropical forests. However, these observations of stocks, fluxes and inferred interactions between them do not point unambiguously to either positive or negative feedbacks in carbon and water exchanges. These ambiguities highlight the need for assimilation of these new measurements with Earth System models for a consistent assessment of process interactions, along with focused field campaigns that integrate ground, aircraft and satellite measurements, to quantify the controlling carbon and water processes and their feedback mechanisms.

Xiao, Q., F. Liang, M. Ning, Q. Zhang, J. Bi, K. He, Y. Lei, and Y. Liu (2021), The long-term trend of PM2.5-related mortality in China: The effects of source data selection, Chemosphere, 263, 127894, doi:10.1016/j.chemosphere.2020.127894.
Quantification of PM2.5 exposure and associated mortality is critical to inform policy making. Previous studies estimated varying PM2.5-related mortality in China due to the usage of different source data, but rarely justify the data selection. To quantify the sensitivity of mortality assessment to source data, we first constructed state-of-the-art PM2.5 predictions during 20002018 at a 1-km resolution with an ensemble machine learning model that filled missing data explicitly. We also calibrated and fused various gridded population data with a geostatistical method. Then we assessed the PM2.5-related mortality with various PM2.5 predictions, population distributions, exposure-response functions, and baseline mortalities. We found that in addition to the well documented uncertainties in the exposure-response functions, missingness in PM2.5 prediction, PM2.5 prediction error, and prediction error in population distribution resulted to a 40.5%, 25.2% and 15.9% lower mortality assessment compared to the mortality assessed with the best-performed source data, respectively. With the best-performed source data, we estimated a total of approximately 25 million PM2.5-related mortality during 20012017 in China. From 2001 to 2017, The PM2.5 variations, growth and aging of population, decrease in baseline mortality led to a 7.8% increase, a 42.0% increase and a 24.6% decrease in PM2.5-related mortality, separately. We showed that with the strict clean air policies implemented in 2013, the population-weighted PM2.5 concentration decreased remarkably at an annual rate of 4.5 μg/m3, leading to a decrease of 179 thousand PM2.5-related deaths nationwide during 20132017. The mortality decrease due to PM2.5 reduction was offset by the population growth and aging population.


Adebiyi, A., J. Kok, Y. Wang, A. Ito, D. Ridley, P. Nabat, and C. Zhao (2020), Dust Constraints from joint Observational-Modelling-experiMental analysis (DustCOMM): comparison with measurements and model simulations, Atmospheric Chemistry and Physics, 20(2), doi:DOI:10.5194/acp-20-829-2020. [online] Available from: .
Mineral dust is the most abundant aerosol species by mass in the atmosphere, and it impacts global climate, biogeochemistry, and human health. Understanding these varied impacts on the Earth system requires accurate knowledge of dust abundance, size, and optical properties, and how they vary in space and time. However, current global models show substantial biases against measurements of these dust properties. For instance, recent studies suggest that atmospheric dust is substantially coarser and more aspherical than accounted for in models, leading to persistent biases in modelled impacts of dust on the Earth system. Here, we facilitate more accurate constraints on dust impacts by developing a new dataset: Dust Constraints from joint Observational-Modelling-experiMental analysis (DustCOMM). This dataset combines an ensemble of global model simulations with observational and experimental constraints on dust size distribution and shape to obtain more accurate constraints on three-dimensional (3-D) atmospheric dust properties than is possible from global model simulations alone. Specifically, we present annual and seasonal climatologies of the 3-D dust size distribution, 3-D dust mass extinction efficiency at 550 nm, and two-dimensional (2-D) atmospheric dust loading. Comparisons with independent measurements taken over several locations, heights, and seasons show that DustCOMM estimates consistently outperform conventional global model simulations. In particular, DustCOMM achieves a substantial reduction in the bias relative to measured dust size distributions in the 0.520 µm diameter range. Furthermore, DustCOMM reproduces measurements of dust mass extinction efficiency to almost within the experimental uncertainties, whereas global models generally overestimate the mass extinction efficiency. DustCOMM thus provides more accurate constraints on 3-D dust properties, and as such can be used to improve global models or serve as an alternative to global model simulations in constraining dust impacts on the Earth system.

Adedeji, A. R., L. Dagar, M. I. Petra, and L. C. D. Silva (2020), Sensitivity of WRF-Chem model resolution in simulating tropospheric ozone in Southeast Asia, IOP Conf. Ser.: Earth Environ. Sci., 489, 012030, doi:10.1088/1755-1315/489/1/012030.
In this paper, WRF-Chem model response to horizontal resolution has been presented in simulating tropospheric ozone distribution during an intense biomass burning across Southeast Asia. Model resolution is varied between 100 km and 20 km. Enhanced fire emissions were also considered in the 20 km resolution simulation. Evaluations were made against observed meteorology such as temperature, relative humidity, wind speed and direction. Spatio-temporal distribution of ozone precursors such as NO2 and CO at the surface retrieved from OMI and MOPITT instruments respectively, were compared against model outputs. Ozonesonde datasets for ozone profile from SHADOZ campaign at Watukosek-Java, Hanoi and Kuala Lumpur were used in evaluating simulated results. All the model simulations adequately represented the observed meteorology. Except in Watukosek-Java where ozone levels were overrepresented, the levels in other locations such as Kuala Lumpur and Hanoi were captured adequately. For model simulations using low-resolution, high-resolution and high-resolution with enhanced fire emissions in Hanoi, Kuala Lumpur and Watukosek-Java region, normalized bias factors are around -0.06, 0.14 and 0.22; 0.01, 0.28 and 0.18, and; 1.20, 3.36 and 3.21, respectively. Normalized root mean square error obtained is as low as 0.09 in Hanoi, and as high as 1.02 in Watukosek-Java region.

Akhmedzhanov, A. K., and T. K. Karadanov (2020), Atmospheric Carbon Dioxide Dynamics over Kazakhstan Derived from Satellite Data, Russ. Meteorol. Hydrol., 45(1), 5457, doi:10.3103/S1068373920010070.
The investigation of atmospheric conditions in the steppe, forest-steppe, and semi-desert zones of Kazakhstan is relevant, the observations of air pollution are carried out in all big settlements. Satellite data are most suitable for solving the problems of quantitative and qualitative assessment of propagation of atmospheric pollutants. The contamination of the atmosphere over large territories which depends on the natural and anthropogenic sources of emission of trace gases can be determined from space. The statistical analysis of ground-based data on the atmospheric concentration of carbon monoxide (CO) over the most polluted big industrial cities is performed. The CO content in the atmosphere over Kazakhstan is analyzed using MOPITT satellite IR radiometer data for the period of 2007-2017. The seasonal and long-term variability of the total CO is revealed. The CO maximum falls on March-April, the minimum is registered in July to October. The average CO content in the atmosphere over Kazakhstan has decreased by 4.7% in the recent decade.

Ashpole, I., and A. Wiacek (2020), Impact of land-water sensitivity contrast on MOPITT retrievals and trends over a coastal city, Atmos. Meas. Tech., 13(7), 35213542, doi:10.5194/amt-13-3521-2020.
We compare MOPITT Version 7 (V7) Level 2 (L2) and Level 3 (L3) carbon monoxide (CO) products for the 1 degrees x 1 degrees L3 grid box containing the coastal city of Halifax, Canada (longitude -63.58 degrees, latitude 44.65 degrees), with a focus on the seasons DJF and JJA, and highlight a limitation in the L3 products that has significant consequences for the temporal trends in near-surface CO identified using those data. Because this grid box straddles the coastline, the MOPITT L3 products are created from the finer spatial resolution L2 products that are retrieved over both land and water, with a greater contribution from retrievals over water because more of the grid box lies over water than land. We create alternative L3 products for this grid box by separately averaging the bounded L2 retrievals over land (L3L) and water (L3W) and demonstrate that profile and total column CO (TCO) concentrations, retrieved at the same time, differ depending on whether the retrieval took place over land or water. These differences (Delta RET) are greatest in the lower troposphere (LT), where mean retrieved volume mixing ratios (VMRs) are greater in L3W than L3L, with maximum mean differences of 11.6 % (14.3 ppbv, p = 0.001) at the surface level in JJA. Retrieved CO concentrations are more similar, on average, in the middle and upper troposphere (MT and UT), although large differences (in excess of 40 %) do infrequently occur. TCO is also greater in L3W than L3L in both seasons. By analysing L3L and L3W retrieval averaging kernels and simulations of these retrievals, we demonstrate that, in JJA, Delta RET is strongly influenced by differences in retrieval sensitivity over land and water, especially close to the surface where L3L has significantly greater information content than L3W. In DJF, land-water differences in retrieval sensitivity are much less pronounced and appear to have less of an impact on Delta RET, which analysis of wind directions suggests is more likely to reflect differences in true profile concentrations (i.e. real differences). The original L3 time series for the 1 degrees x 1 degrees grid box containing Halifax (L30) corresponds much more closely to L3W than L3L, owing to the greater contribution from L2 retrievals over water than land. Thus, in JJA, variability in retrieved CO concentrations close to the surface in L30 is suppressed compared to L3L, and a declining trend detected using weighted least squares (WLS) regression analysis is significantly slower in L30 (strongest surface level trend identifiable is -1.35 (+/- 0.35) ppbv yr(-1)) than L3L (-2.85 (+/- 0.60) ppbv yr(-1)). This is because contributing L2 retrievals over water are closely tied to a priori CO concentrations used in the retrieval, owing to their lack of near-surface sensitivity in JJA, and these are based on monthly climatological CO profiles from a chemical transport model and therefore have no yearly change (surface level trend in L3W is -0.60 (+/- 0.33) ppbv yr(-1)). Although our analysis focuses on DJF and JJA, we demonstrate that the findings also apply to MAM and SON. The results that we report here suggest that similar analyses be performed for other coastal cities before using MOPITT surface CO.

Borsdorff, T., J. Landgraf, and M. K. Sha (2020), TROPOMI Carbon Monoxide, in Handbook of Air Quality and Climate Change, edited by H. Akimoto and H. Tanimoto, pp. 110, Springer, Singapore. [online] Available from: .
One of the primary targets of the TROPOspheric Monitoring Instrument (TROPOMI), which was launched on 13 October 2017 on-board the Copernicus Sentinel-5 Precursor satellite, is to provide measurements of the total column concentrations of carbon monoxide (CO) in the atmosphere with daily global coverage and a high spatial resolution up to 5.5 × 7 km2. SRON, the Netherlands Institute for Space Research, developed the Shortwave Infrared CO retrieval (SICOR) algorithm that infers CO columns simultaneously with effective cloud parameters from TROPOMI’s 2.3 μm measurements and is deployed by the European Space Agency (ESA) for the near real-time and offline processing of TROPOMI data. Already early in the mission, the TROPOMI CO data set was validated with reference measurements of the Total Carbon Column Observing Network (TCCON), the Infrared Working Group of the Network for the Detection of Atmospheric Composition Change (NDACC-IRWG), and the Measurements Of Pollution in the Atmosphere (MOPITT) and inter-compared with the calculation of the European Centre for Medium-Range Weather Forecasts (ECMWF) assimilation system (ECMWF-IFS). The overall conclusion is that the TROPOMI CO data set is well within the mission requirements of 10% precision and 15% accuracy, and so the product was released by ESA for public access via the Copernicus Open Access Hub ( The TROPOMI CO data set proves useful to track the transport of air pollution on regional and global scales. The high signal to noise ratio of the measurements additionally allows to monitor pollution hot spots like cities, main traffic roads, and plumes from industrial activities, e.g., steel plants and biomass burning events using data from individual satellite overpasses.

Cazorla, M., and E. Herrera (2020), Air quality in the Galapagos Islands: A baseline view from remote sensing and in situ measurements, Meteorol. Appl., doi:10.1002/met.1878.
A characterization of ambient air levels of PM2.5, O-3, SO2, NO2 and CO in the Galapagos Islands of Ecuador is presented from in situ and remote sensing observations. PM2.5 was derived from aerosol optical depth (AOD; AERONET) measured at the Universidad San Francisco de Quito, Galapagos Campus (2017-2019). Boundary layer (BL) ozone was obtained from Southern Hemisphere Additional Ozonesondes (SHADOZ) profiles (1998-2016). Background SO2 and pollution events during volcanic eruptions (2005-2018) were estimated from Ozone Monitoring Instrument (OMI) total column measurements through a well-mixed volume approach. Similarly, ambient NO2 was estimated from OMI data (2012-2019). CO was obtained from Measurement Of Pollution In The Troposphere (MOPITT) observations (2012-2017). The study was complemented using Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) reanalysis products and backward trajectory model runs. From the results, baseline levels of the analysed species (PM2.5 = 3.8 mu g center dot m(-3), O-3 = 17 ppbv, SO2 = 3.6 ppbv, CO = 80 ppbv, NO2 in populated islands = 23 pptv as one year averages) are comparable with other pristine regions, but some factors can cause increased concentrations. First, high tourism seasons (February-April and July-September) raise background PM2.5, NO2 and CO. Furthermore, signals in July-September can be augmented by transport from biomass-burning regions in the Amazon. This latter factor episodically causes ozone to increase up to 45-75 ppbv (1 hr mean). Lastly, volcanic eruptions raise SO2 up to almost 700 ppbv (24 hr mean) and increase PM2.5 to 29.5 mu g center dot m(-3) (1 hr mean). The present study provides for the first time baseline levels of air contaminants in the Galapagos, and identifies specific sources whose effect in time is necessary to monitor given global conditions of vulnerable environmental quality.

Dajuma, A., K. Ogunjobi, H. Vogel, P. Knippertz, S. Siélé, N. Touré, V. Yoboué, and B. Vogel (2020), Downward cloud venting of the central African biomass burning plume during the West Africa summer monsoon, Atmospheric Chemistry and Physics, 20, 53735390, doi:10.5194/acp-20-5373-2020.
Between June and September large amounts of biomass burning aerosol are released into the atmosphere from agricultural fires in central and southern Africa. Recent studies have suggested that this plume is carried westward over the Atlantic Ocean at altitudes between 2 and 4 km and then northward with the monsoon flow at low levels to increase the atmospheric aerosol load over coastal cities in southern West Africa (SWA), thereby exacerbating air pollution problems. However, the processes by which these fire emissions are transported into the planetary boundary layer (PBL) are still unclear. One potential factor is the large-scale subsidence related to the southern branch of the monsoon Hadley cell over the tropical Atlantic. Here we use convection-permitting model simulations with COSMO-ART to investigate for the first time the contribution of downward mixing induced by clouds, a process we refer to as downward cloud venting in contrast to the more common process of upward transport from a polluted PBL. Based on a monthly climatology, model simulations compare satisfactory with wind fields from reanalysis data, cloud observations, and satellite-retrieved carbon monoxide (CO) mixing ratio. For a case study on 2 July 2016, modelled clouds and rainfall show overall good agreement with Spinning Enhanced Visible and InfraRed Imager (SEVIRI) cloud products and Global Precipitation Measurement Integrated Multi-satellitE Retrievals (GPM-IMERG) rainfall estimates. However, there is a tendency for the model to produce too much clouds and rainfall over the Gulf of Guinea. Using the CO dispersion as an indicator for the biomass burning plume, we identify individual mixing events south of the coast of Côte d’Ivoire due to midlevel convective clouds injecting parts of the biomass burning plume into the PBL. Idealized tracer experiments suggest that around 15 % of the CO mass from the 24 km layer is mixed below 1 km within 2 d over the Gulf of Guinea and that the magnitude of the cloud venting is modulated by the underlying sea surface temperatures. There is even stronger vertical mixing when the biomass burning plume reaches land due to daytime heating and a deeper PBL. In that case, the long-range-transported biomass burning plume is mixed with local anthropogenic emissions. Future work should provide more robust statistics on the downward cloud venting effect over the Gulf of Guinea and include aspects of aerosol deposition.

Elguindi, N., C. Granier, T. Stavrakou, S. Darras, M. Bauwens, H. Cao, C. Chen, H. A. C. D. van der Gon, O. Dubovik, T. M. Fu, D. K. Henze, Z. Jiang, S. Keita, J. J. P. Kuenen, J. Kurokawa, C. Liousse, K. Miyazaki, J.-F. Mueller, Z. Qu, F. Solmon, and B. Zheng (2020), Intercomparison of Magnitudes and Trends in Anthropogenic Surface Emissions From Bottom-Up Inventories, Top-Down Estimates, and Emission Scenarios, Earth Future, 8(8), e2020EF001520, doi:10.1029/2020EF001520.
This study compares recent CO, NOx, NMVOC, SO2, BC, and OC anthropogenic emissions from several state-of-the-art top-down estimates to global and regional bottom-up inventories and projections from five Shared Socioeconomic Pathways (SSPs) in several regions. Results show that top-down emissions derived in several recent studies exhibit similar uncertainty as bottom-up inventories in some regions for certain species and even less in the case of Chinese CO emissions. In general, the largest discrepancies are found outside of regions such as the United States, Europe, and Japan where the most accurate and detailed information on emissions is available. In some regions such as China, which has recently undergone dynamical economic growth and changes in air quality regulations, the top-down estimates better capture recent emission trends than global bottom-up inventories. These results show the potential of top-down estimates to complement bottom-up inventories and to aide in the development of emission scenarios, particularly in regions where global inventories lack the necessary up-to-date and accurate information regarding regional activity data and emission factors such as Africa and India. Areas of future work aimed at quantifying and reducing uncertainty are also highlighted. A regional comparison of recent CO and NO(x)trends in the five SSPs indicate that SSP126, a strong pollution control scenario, best represents the trends from the top-down and regional bottom-up inventories in the United States, Europe, and China, while SSP460, a low-pollution control scenario, lies closest to actual trends in West Africa. This analysis can be useful for air quality forecasting and near-future pollution control/mitigation policy studies.

Gaubert, B., L. K. Emmons, K. Raeder, S. Tilmes, K. Miyazaki, A. F. Arellano Jr., N. Elguindi, C. Granier, W. Tang, J. Barré, H. M. Worden, R. R. Buchholz, D. P. Edwards, P. Franke, J. L. Anderson, M. Saunois, J. Schroeder, J.-H. Woo, I. J. Simpson, D. R. Blake, S. Meinardi, P. O. Wennberg, J. Crounse, A. Teng, M. Kim, R. R. Dickerson, H. He, X. Ren, S. E. Pusede, and G. S. Diskin (2020), Correcting model biases of CO in East Asia: impact on oxidant distributions during KORUS-AQ, Atmospheric Chemistry and Physics, 20(23), 1461714647, doi:

Abstract. Global coupled chemistryclimate models underestimate carbon monoxide (CO) in the Northern Hemisphere, exhibiting a pervasive negative bias against measurements peaking in late winter and early spring. While this bias has been commonly attributed to underestimation of direct anthropogenic and biomass burning emissions, chemical production and loss via OH reaction from emissions of anthropogenic and biogenic volatile organic compounds (VOCs) play an important role. Here we investigate the reasons for this underestimation using aircraft measurements taken in May and June 2016 from the KoreaUnited States Air Quality (KORUS-AQ) experiment in South Korea and the Air Chemistry Research in Asia (ARIAs) in the North China Plain (NCP). For reference, multispectral CO retrievals (V8J) from the Measurements of Pollution in the Troposphere (MOPITT) are jointly assimilated with meteorological observations using an ensemble adjustment Kalman filter (EAKF) within the global Community Atmosphere Model with Chemistry (CAM-Chem) and the Data Assimilation Research Testbed (DART). With regard to KORUS-AQ data, CO is underestimated by 42 % in the control run and by 12 % with the MOPITT assimilation run. The inversion suggests an underestimation of anthropogenic CO sources in many regions, by up to 80 % for northern China, with large increments over the Liaoning Province and the North China Plain (NCP). Yet, an often-overlooked aspect of these inversions is that correcting the underestimation in anthropogenic CO emissions also improves the comparison with observational O3 datasets and observationally constrained box model simulations of OH and HO2. Running a CAM-Chem simulation with the updated emissions of anthropogenic CO reduces the bias by 29 % for CO, 18 % for ozone, 11 % for HO2, and 27 % for OH. Longer-lived anthropogenic VOCs whose model errors are correlated with CO are also improved, while short-lived VOCs, including formaldehyde, are difficult to constrain solely by assimilating satellite retrievals of CO. During an anticyclonic episode, better simulation of O3, with an average underestimation of 5.5 ppbv, and a reduction in the bias of surface formaldehyde and oxygenated VOCs can be achieved by separately increasing by a factor of 2 the modeled biogenic emissions for the plant functional types found in Korea. Results also suggest that controlling VOC and CO emissions, in addition to widespread NOx controls, can improve ozone pollution over East Asia.

Girach, I. A., N. Tripathi, P. R. Nair, L. K. Sahu, and N. Ojha (2020a), O3 and CO in the South Asian outflow over the Bay of Bengal: Impact of monsoonal dynamics and chemistry, Atmos. Environ., 233, 117610, doi:10.1016/j.atmosenv.2020.117610.
Monsoonal dynamics strongly impacts the composition over the South Asian region, however, in situ measurements remain limited mostly to the continental region. Whereas, remote oceanic regions of the Bay of Bengal (BoB) remain largely unexplored where shipping emissions can infuse into the South Asian outflow. In this direction, we performed ship-based measurements of ozone (O-3) and carbon monoxide (CO) over the BoB during July.August 2018 and corroborated the analyses with model results and satellite retrievals. Surface level mixing ratios of O-3 and CO varied in the range of 14-45 and 50-164 ppbv, respectively during the expedition. Elevated O-3 and CO levels were observed in coastal region downwind of a tropical megacity (Chennai), referred to as the Chennai-plume. Analysis of the Copernicus Atmosphere Monitoring Service (CAMS) model simulations suggests volatile organic compound (VOC)-limited O-3 production in morning over most of the plume and east coast followed by gradual shift to NOx-limited regime over the BoB in afternoon. While the southern BoB (7-10 degrees N) received generally pristine airmasses from the equatorial Indian Ocean, impacts of shipping emissions near 6 degrees N are observed. Consequently, higher values of CO (as much as 120 ppbv) and net O-3 production by 1.1-1.3 ppbv h(-1) with a diurnal amplitude of 4-8 ppbv are observed over the southern BoB. Satellite-based observations from the Measurements of Pollution in the Troposphere (MOPITT) and results from CAMS model show decreasing trend (4.1-5 +/- 1 ppbv decade(-1)) of surface CO, as also inferred from in situ measurements. Zonal fluxes of CO across the east coast show the outflow over the BoB with higher values (2-3. 10(19) molecules m(-2) s(-1)) over the northern BoB. Positive vertical fluxes (similar to 2. 10(16) molecules m(-2) s(-1)) show the transport of CO from marine boundary layer to the free-troposphere. Due to strong updrafts, CO levels in upper and lower troposphere are seen to be comparable during monsoon. These findings in conjunction with higher methane and nitrogen dioxide in the upper-troposphere manifest the influences of monsoonal convection and trapping of trace gases in the anticyclone.

Girach, I. A., P. R. Nair, N. Ojha, and L. K. Sahu (2020b), Tropospheric carbon monoxide over the northern Indian Ocean during winter: influence of inter-continental transport, Clim. Dyn., 54(1112), 50495064, doi:10.1007/s00382-020-05269-4.
South Asian outflow over the adjoining marine regions is most pronounced during winter season, whereas the prevalence of strong winds aloft can transport the influences from inter-continental sources. Here, we investigate the tropospheric carbon monoxide (CO) distribution over the northern Indian Ocean (IO) combining shipborne measurements carried out during the Integrated Campaign for Aerosols, gases, and Radiation Budget (ICARB) campaign (January-February 2018), retrievals from Measurements of Pollution in the Troposphere (MOPITT), and Copernicus Atmosphere Monitoring Service (CAMS) model. Surface CO varied from similar to 50 to 365 ppbv (179 +/- 67 ppbv) with higher levels over the coastal region of southeast Arabian Sea and lower levels over the equatorial IO. We observed lower CO levels (200 +/- 43 ppbv) than those during the Indian Ocean Experiment-1999 (229 +/- 40 ppbv) supporting the reported decreasing trend of tropospheric CO. In situ CO observations are found to be in a good agreement with the satellite retrievals (MOPITT-version 8) as well as the CAMS model results (r(2) = 0.60-0.65). The upper-tropospheric CO (300-200 hPa) over the equatorial IO is observed to be higher by up to 30% during February-2018 as compared to the decadal mean, coinciding with anomalous westerlies resulting from a disturbed Walker cell over the equatorial IO and deeper penetration of the sub-tropical jet. The influences of African forest fires are suggested to have enhanced the upper-tropospheric CO over the IO during February-2018. Our study highlights the importance of strong large-scale dynamics and global biomass-burning emissions in the wintertime pollution loading over the IO, besides the South Asian outflow.

Horowitz, L. W., V. Naik, F. Paulot, P. A. Ginoux, J. P. Dunne, J. Mao, J. Schnell, X. Chen, J. He, J. G. John, M. Lin, P. Lin, S. Malyshev, D. Paynter, E. Shevliakova, and M. Zhao (2020), The GFDL Global Atmospheric Chemistry-Climate Model AM4.1: Model Description and Simulation Characteristics, Journal of Advances in Modeling Earth Systems, n/a(n/a), doi:10.1029/2019MS002032. [online] Available from: .
We describe the baseline model configuration and simulation characteristics of GFDL’s Atmosphere Model version 4.1 (AM4.1), which builds on developments at GFDL over 20132018 for coupled carbon-chemistry-climate simulation as part of the sixth phase of the Coupled Model Intercomparison Project. In contrast with GFDL’s AM4.0 development effort, which focused on physical and aerosol interactions and which is used as the atmospheric component of CM4.0, AM4.1 focuses on comprehensiveness of Earth system interactions. Key features of this model include doubled horizontal resolution of the atmosphere ( 200 km to 100 km) with revised dynamics and physics from GFDL’s previous-generation AM3 atmospheric chemistry-climate model. AM4.1 features improved representation of atmospheric chemical composition, including aerosol and aerosol precursor emissions, key land-atmosphere interactions, comprehensive land-atmosphere-ocean cycling of dust and iron, and interactive ocean-atmosphere cycling of reactive nitrogen. AM4.1 provides vast improvements in fidelity over AM3, captures most of AM4.0’s baseline simulations characteristics and notably improves on AM4.0 in the representation of aerosols over the Southern Ocean, India, and Chinaeven with its interactive chemistry representationand in its manifestation of sudden stratospheric warmings in the coldest months. Distributions of reactive nitrogen and sulfur species, carbon monoxide, and ozone are all substantially improved over AM3. Fidelity concerns include degradation of upper atmosphere equatorial winds and of aerosols in some regions.

Huijnen, V., K. Miyazaki, J. Flemming, A. Inness, T. Sekiya, and M. G. Schultz (2020), An intercomparison of tropospheric ozone reanalysis products from CAMS, CAMS interim, TCR-1, and TCR-2., Geoscientific Model Development, 13(3). [online] Available from: .
Global tropospheric ozone reanalyses constructed using different state-of-the-art satellite data assimilation systems, prepared as part of the Copernicus Atmosphere Monitoring Service (CAMS-iRean and CAMS-Rean) as well as two fully independent reanalyses (TCR-1 and TCR-2, Tropospheric Chemistry Reanalysis), have been intercompared and evaluated for the past decade. The updated reanalyses (CAMS-Rean and TCR-2) generally show substantially improved agreements with independent ground and ozone-sonde observations over their predecessor versions (CAMS-iRean and TCR-1) for diurnal, synoptical, seasonal, and interannual variabilities. For instance, for the Northern Hemisphere (NH) mid-latitudes the tropospheric ozone columns (surface to 300 hPa) from the updated reanalyses show mean biases to within 0.8 DU (Dobson units, 3 % relative to the observed column) with respect to the ozone-sonde observations. The improved performance can likely be attributed to a mixture of various upgrades, such as revisions in the chemical data assimilation, including the assimilated measurements, and the forecast model performance. The updated chemical reanalyses agree well with each other for most cases, which highlights the usefulness of the current chemical reanalyses in a variety of studies. Meanwhile, significant temporal changes in the reanalysis quality in all the systems can be attributed to discontinuities in the observing systems. To improve the temporal consistency, a careful assessment of changes in the assimilation configuration, such as a detailed assessment of biases between various retrieval products, is needed. Our comparison suggests that improving the observational constraints, including the continued development of satellite observing systems, together with the optimization of model parameterizations such as deposition and chemical reactions, will lead to increasingly consistent long-term reanalyses in the future.

I, N., S. Srivastava, Y. Yarragunta, R. Kumar, and D. Mitra (2020), Distribution of surface carbon monoxide over the Indian subcontinent: Investigation of source contributions using WRF-Chem, Atmospheric Environment, 243, 117838, doi:10.1016/j.atmosenv.2020.117838.
This study investigates fractional contribution of different carbon monoxide (CO) sources over the Indian subcontinent at the surface in 2015 using a tagged tracer approach in the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). Model simulations are evaluated with respect to in-situ and satellite observations. The simulated CO levels reproduced in-situ observations in Pune, Anantapur, Udaipur, Ahmedabad, and Chennai reasonably well with mean bias ranging from −89.9 to 87.0 ppbv and RMSE ranging from 28 to 40% but a poor model performance was noticed in Hyderabad, Jabalpur, and Kanpur with larger mean bias (−259.0190.9 ppbv) and RMSE (4596%). Simulated CO concentrations are also compared with CO retrieved by MOPITT at 800 hPa and 200 hPa. At 800 hPa (200 hPa), the annual average WRF-Chem CO varies from 195 ± 69 to 224 ± 93 ppbv (102 ± 25 to 136 ± 21 ppbv) while MOPITT CO varies from 103 ± 26 to 114 ± 29 ppbv (103 ± 30 to 134 ± 33) over different Indian sub-regions. Over most of the regions, good correlation (coefficient of correlation > 0.7) is observed between simulated and satellite observed CO with mean bias of 92118 ppbv at 800 hPa and −4 to 3 ppbv at 200 hPa. Over the total Indian region, we find the highest contribution from anthropogenic emissions (CO-ANT) and inflow into the model domain from domain boundaries (CO-BACK) with 4546% contribution each and very small contribution (<5%) of biomass burning (CO-BIOM), biogenic (CO-BIOG) emissions, and photochemical production (CO-CHEM). Fractional contribution of these tracers are analysed over different Indian sub-regions. CO-ANT (2169%) and CO-BACK (2266%) contributions are found high throughout the year over all the Indian landmass regions. CO-BACK contribution is found to be maximum (7095%) over the Bay of Bengal and Arabian Sea. During winter season, CO-ANT and CO-BACK contribute 3269% and 2756% respectively over landmass regions of India. During spring, highest CO-BACK (66%) over Western India as compared to other landmass regions is attributed to CO inflow from the Arabian Peninsula and Middle East region. CO-BIOM contributes more than 22% in NE&M (North-East India and Myanmar) during spring due to slash and burn agriculture practice. During summer, transport of cleaner marine air and stronger vertical mixing are major causes of lower CO concentration over all sub-regions. During autumn, CO-ANT contributes 3370% over different landmass regions. Surface CO concentration is found to be mainly controlled by the direct anthropogenic emission in Indian megacities with a contribution exceeding 70% to CO in Delhi and Kolkata throughout the year.

Irwan, Z., A. R. M. Amin, and N. E. F. M. Akhir (2020), TROPHOSPHERIC CARBON MONOXIDE TRENDS OVER MALAYSIA USING SATELLITE-SENSED DATA FOR A PERIOD OF 2000-2018, Gading Journal of Science and Technology (e-ISSN: 2637-0018), 3(01), 6066.
Tropospheric carbon monoxide (CO) is one of the most significant air pollutant gas that can affect human health, as stated by United States Environmental Protection Agency (USEPA). This study aims to evaluate the trend of CO gas using 18 years of data (April 2000 December 2018) measured by Measurements of Pollution in the Troposphere (MOPITT) over Malaysia. The results show significant decrease in concentration of CO with mean of monthly carbon monoxide of 113.25 ppbv for the entire period. The seasonal cycle of CO showed maximum levels in December-January, but minimum levels in June-August. The highest values of CO were in west region of Peninsular Malaysia throughout the year. The CO gas was highly concentrated over the west region of Peninsular Malaysia resulted from human activity and abundance sources of CO at this area due to its larger number of human populations, various industrial activities, crowded city with extremely higher traffic.

Kalluri, R. O. R., X. Zhang, L. Bi, J. Zhao, L. Yu, and R. G. Kotalo (2020), Carbonaceous aerosol emission reduction over Shandong province and the impact of air pollution control as observed from synthetic satellite data, Atmospheric Environment, 222, 117150, doi:10.1016/j.atmosenv.2019.117150.
Aerosol loading and trace gas emissions from agriculture crop residue burning has been one of the main factors leading to the deterioration of air quality especially during the harvest time in China. Here, we evaluate the contribution of atmospheric aerosol loading from biomass burning and its relationship to the air pollution control policy. We focused on Shandong province, China because it has the highest level of agriculture burning pollution in October. Satellite-based data related to biomass burning including aerosol optical depth (AOD) and fire pixel counts from Moderate Resolution Imaging Spectroradiometer (MODIS), carbon monoxide (CO) from Measurements Of Pollution In The Troposphere (MOPITT), aerosol index (AI) and tropospheric NO2 from Ozone Monitoring Instrument (OMI), and aerosol layer depths from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). These metrics were synthetically utilized to evaluate spatial and temporal variation of atmospheric aerosols during the agriculture crop residue burning month from 2006 to 2017. Carbonaceous aerosol emission reduction and the impact of the air pollution control policy can be found in the CALIPSO aerosol types and MODIS fire pixel counts data. The AOD, NO2, CO, and AI over three different land covers (cropland, forest and impervious surfaces) were further obtained according to the land cover data set. The results indicated that there was an obvious decrease in all carbonaceous aerosol-related quantities after year 2012 when the local government began to enact and implement strict air pollution control policies, although a period (23 years) of transition after the policy implementation time was identified. We also found that CO is stable and low over the cropland versus forest and impervious surfaces; NO2 exhibits a continuously high value in the northern areas of the oil field. The impact of industry activity rather than straw burning should be also considered for NO2 and CO in certain areas.

Kanawade, V. P., A. K. Srivastava, K. Ram, E. Asmi, V. Vakkari, V. K. Soni, V. Varaprasad, and C. Sarangi (2020), What caused severe air pollution episode of November 2016 in New Delhi?, Atmospheric Environment, 222, 117125, doi:10.1016/j.atmosenv.2019.117125.
In recent years, South Asia is experiencing severely degraded air quality, with particulate matter less than 2.5 μm (PM2.5) reaching unprecedented high levels. Here, we investigate a severe air pollution episode (SAPE) witnessed in New Delhi during 17 November 2016. This was a very unusual air pollution episode wherein air quality index exceeded >500 and was persistent for about a week encapsulating the entire Indo-Gangetic Plain (IGP). We demonstrate that a stagnant weather condition was the dominant cause of the SAPE. Mean concentration of PM2.5 in New Delhi before, during, and after the SAPE were 142 μg/m3, 563 μg/m3, and 240 μg/m3, respectively. Satellite-based aerosol optical depth (AOD), ultraviolet-aerosol index (UV-AI) and surface carbon monoxide (CO) concentrations also showed significant enhancements over large locale spatially by about 5070% during the SAPE. A large and simultaneous increase in UV-AI and CO downwind of a large number of fire hotspots (Punjab and Haryana) is a clear indication of biomass burning aerosols. Analysis of absorption Ångström exponent further substantiates this finding, showing a large fraction of light absorbing carbonaceous-type aerosols. Radiosonde observations clearly showed that stagnant atmospheric conditions led to SAPE in New Delhi by allowing pollution to accumulate and persist in the near-surface environment. As a result new particle formation was suppressed due to very high pre-existing aerosol concentrations during the SAPE. The heating rate induced by light absorbing aerosols into an atmospheric layer during SAPE was also very high (3.1 ± 0.7 K/day). These findings will help in understanding air quality and climate effects, as well as in formulating policies to mitigate these complex pollution episodes in an anthropogenic future.

Kuai, L., K. W. Bowman, K. Miyazaki, M. Deushi, L. Revell, and E. Rozanov (2020), Attribution of Chemistry-Climate Model Initiative (CCMI) ozone radiative flux bias from satellites., Atmospheric Chemistry and Physics, 20(1), 281281.
Kumari, S., A. Lakhani, and K. M. Kumari (2020), Transport of aerosols and trace gases during dust and crop-residue burning events in Indo-Gangetic Plain: Influence on surface ozone levels over downwind region, Atmospheric Environment, 241, 117829, doi:10.1016/j.atmosenv.2020.117829.
The present study addresses the influence of long-range transport from dust storm (event 1) and crop-residue burning (event 2) sources over Indo-Gangetic Plain (IGP) using ground-based measurements and satellite observations. In the present study, the spatial distribution and temporal variation of ambient particulate matter (PM) were assessed at 15 air quality monitoring stations situated in Rajasthan, north-western-Indo-Gangetic Plain (NW-IGP) and downwind region. During the dust event, the daily average mass concentrations of PM2.5 and PM10 were 1.23.3 and 2.24.6 times higher than the National Ambient Air Quality Standards (NAAQS 60 μg/m3 for PM2.5 and 100 μg/m3 for PM10) across stations in the vicinity of the Thar Desert. Stations in NW-IGP showed enhancement in PM2.5 and PM10 during crop-residue burning period. Agra being a downwind site was influenced by both the events and enhancement in PM levels was observed, however ozone (O3) showed different variations during event 1 and 2. During the dust event, 6.1% reduction in the mean O3 level compared to the study period was found while a significant enhancement (15.1%) during event 2 was observed at Agra. To determine the possible reasons for different O3 trends, the variation of O3 precursors carbon monoxide (CO) and nitrogen oxides (NOx) along with the meteorological parameters was also assessed. CO and NOx levels during event 1 were reduced similar to O3 whereas during event 2 an enhancement in CO and NOx levels was observed. Satellite observations and backward air-mass trajectories suggested transport of aerosols from Thar Desert resulted in reduced O3 levels during dust event while transport of O3 precursors enhanced photochemical production of O3 during crop-residue burning period at Agra.

Lalitaporn, P., and T. Mekaumnuaychai (2020), Satellite measurements of aerosol optical depth and carbon monoxide and comparison with ground data, Environ. Monit. Assess., 192(6), 369, doi:10.1007/s10661-020-08346-7.
Satellite data of aerosol optical depths (AODs) from the moderate resolution imaging spectroradiometer (MODIS) and carbon monoxide (CO) columns from the measurements of pollution in the troposphere (MOPITT) were collected for the study in Northern Thailand. Comparative analyses were conducted of MODIS (Terra and Aqua) AODs with ground particulate matter with diameter below 10 microns (PM10) concentrations and MOPITT CO surface/total columns with ground CO concentrations for 2014-2017. Temporal variations in both the satellite and ground datasets were in good agreement. High levels of air pollutants were common during March-April. The annual analysis of both satellite and ground datasets revealed the highest levels of air pollutants in 2016 and the lowest levels in 2017. The AODs and PM10 concentrations were at higher levels in the morning than in the afternoon. The comparison between satellite products showed that AODs correlated better with the CO total columns than the CO surface columns. The regression analysis presented better performance of Aqua AODs-PM10 than Terra AODs-PM10 with correlation coefficients (r) of 0.72-0.83 and 0.57-0.79, respectively. Ground CO concentrations correlated better with MOPITT CO surface columns (r = 0.65-0.73) than with CO total columns (r = 0.56-0.72). The r values of satellite and ground datasets were greatest when the analysis was restricted to November-March (dry weather periods with possible low mixing height (MH)). Overall, the results suggested that the relationships between satellite and ground data can be used to develop predictive models for ground PM10 and CO in northern Thailand, particularly during air pollution episodes located where ground monitoring stations are limited.

Lama, S., S. Houweling, K. F. Boersma, H. Eskes, I. Aben, H. A. C. Denier van der Gon, M. C. Krol, H. Dolman, T. Borsdorff, and A. Lorente (2020), Quantifying burning efficiency in megacities using the NO2∕CO ratio from the Tropospheric Monitoring Instrument (TROPOMI), Atmospheric Chemistry and Physics, 20(17), 1029510310, doi:

Abstract. This study investigates the use of co-located nitrogen dioxide (NO2) and carbon monoxide (CO) retrievals from the TROPOMI satellite to improve the quantification of burning efficiency and emission factors (EFs) over the megacities of Tehran, Mexico City, Cairo, Riyadh, Lahore, and Los Angeles. Efficient combustion is characterized by high NOx (NO+NO2) and low CO emissions, making the NO2∕CO ratio a useful proxy for combustion efficiency (CE). The local enhancement of CO and NO2 above megacities is well captured by TROPOMI at short averaging times compared with previous satellite missions. In this study, the upwind background and plume rotation methods are used to investigate the accuracy of satellite-derived ΔNO2∕ΔCO ratios. The column enhancement ratios derived using these two methods vary by 5&thinsp;% to 20&thinsp;% across the selected megacities. TROPOMI-derived column enhancement ratios are compared with emission ratios from the EDGAR v4.3.2 (Emission Database for Global Atmospheric Research v4.3.2) and the MACCity (Monitoring Atmospheric Chemistry and Climate and CityZen) 2018 emission inventories. TROPOMI correlates strongly (r=0.85 and 0.7) with EDGAR and MACCity, showing the highest emission ratio for Riyadh and lowest emission ratio for Lahore. However, inventory-derived emission ratios are 60&thinsp;% to 85&thinsp;% higher than TROPOMI column enhancement ratios across the six megacities. The short lifetime of NO2 and the different vertical sensitivity of TROPOMI NO2 and CO explain most of this difference. We present a method to translate TROPOMI-retrieved column enhancement ratios into corresponding emission ratios, thereby accounting for these influences. Except for Los Angeles and Lahore, TROPOMI-derived emission ratios are close (within 10&thinsp;% to 25&thinsp;%) to MACCity values. For EDGAR, however, emission ratios are ∼65&thinsp;% higher for Cairo and 35&thinsp;% higher for Riyadh. For Los Angeles, EDGAR and MACCity are a factor of 2 and 3 higher than TROPOMI respectively. The air quality monitoring networks in Los Angeles and Mexico City are used to validate the use of TROPOMI. For Mexico City and Los Angeles, these measurements are consistent with TROPOMI-derived emission ratios, demonstrating the potential of TROPOMI with respect to monitoring burning efficiency.

Lin, C., and J. Cohen (2020), New simple approach to understand the spatial and vertical distribution of biomass burning CO emission based on the MOPITT vertical measurements, , 22, 9220.
A simple variance-maximization approach, based on 19 years of weekly  Moderate Resolution Imaging spectroradiometer (MOPITT) CO vertical measurements, was employed to quantify the spatial distribution of the global seasonal biomass burning region. Results demonstrate there are a few large-scale and typical biomass burning regions responsible for most of the biomass burning emissions throughout the world, with the largest of these such regions located in Amazonian South America, Western Africa, Indonesia, and Northern Southeast Asia (Eastern India, Northern Myanmar, Laos, Vietnam and Eastern Bangladesh), which are highly associated with the results of Global Fire Emission Database(GFED). The CO is primarily lofted to and spreads downwind at 800mb or 700mb with three exceptions: The Maritime Continent and South America where there is significant spread at 300mb consistent with known deep- and pyro-convection; and Southern Africa where there is significant spread at 600mb. The total mass of CO lofted into the free troposphere ranges from 46% over Central Africa to 92% over Australia.

Lin, C., J. B. Cohen, S. Wang, R. Lan, and W. Deng (2020a), A new perspective on the spatial, temporal, and vertical distribution of biomass burning: quantifying a significant increase in CO emissions, Environ. Res. Lett., doi:10.1088/1748-9326/abaa7a. [online] Available from: .
A variance-maximization approach based on 19-years of weekly MOPITT Carbon Monoxide (CO) measurements quantifies the spatial-temporal distribution of global biomass burning. Seven regions consistent with existing datasets are discovered and shown to burn for longer, over a more widespread area. Each region has a unique and recurring burning season, with three dominated by inter- and intra-annual variation. The CO is primarily lofted to the free troposphere from where it spreads downwind at 800 to 700mb with three exceptions: The Maritime Continent and South America where there is spread at 300mb consistent with deep- and pyro-convection; and Southern Africa which reaches to 600mb. The total mass of CO lofted into the free troposphere ranges from 46% over Central Africa to 92% over Australia. The global, annual emissions made using two different techniques lead to an increase of biomass burning CO emissions of 47TgCO/year and 99TgCO/year respectively. The larger increase is mainly due to two factors: first, a large amount of the emissions is lofted rapidly upwards over the biomass burning region and subsequently transported downwind, therefore not appearing near the biomass source in space and time and second, an increase in inter-annual variability. Consistently, there is an increase in variability year-to-year and during peak events, from which 35% to more than 80% of the total emissions is lofted into the free troposphere. The results demonstrate a significantly higher CO emission from biomass burning, a larger impact on the global atmospheric composition, and likely impacts on atmospheric chemistry and climate change.

Lin, C., J. B. Cohen, S. Wang, and R. Lan (2020b), Application of a combined standard deviation and mean based approach to MOPITT CO column data, and resulting improved representation of biomass burning and urban air pollution sources, Remote Sensing of Environment, 241, 111720, doi:10.1016/j.rse.2020.111720.
This work presents a new methodology to simultaneously account for both the mean and variance of 17 years of Carbon Monoxide [CO] measurements from the MOPITT satellite (from 2000 to 2016) over Southeast and East Asia. We demonstrate that the new technique is stable and produces a set of results which are both consistent with the understood geographical and temporal distribution of CO sources, as well as those of some other co-emitted species. These regions were chosen because they have high levels of CO loadings and complex factors driving their underlying emissions profiles. We first successfully categorize the region, based on the total CO column measurements, into those locations impacted by intense urbanization (high climatological mean, low climatological variance, high loading throughout most of the year, and variation mostly due to global-scale chemistry and climatology), large-scale biomass burning (low climatological mean, high climatological variance, mostly clean but with short and intense peak events occurring around a similar time year-to-year), those regions undergoing a significant change from one type to another, and those regions which are clean. We further reproduce the temporal and spatial distributions of other co-emitted species measured by other measurement platforms, including aerosols (AOD) and gasses (NO2), and demonstrate consistency across all three platforms. Third of all, we produce an important scientific finding using these new results, in terms of a significant geographic expansion of the known biomass burning regions from Myanmar through Northern Vietnam, as compared with previous research. Fourth, we also find that urbanization dominates emissions of CO over both known urban agglomerations in East and Southeast Asia, including around Beijing, Shanghai, the Pearl River Delta, Seoul, Shandong, Chengdu, Chongqing, Hanoi and Bangkok, but also extend into otherwise unclassified or recently emerging mega-cities including Shanxi Province, Henan Province, and Liaoning Province. Additionally, we have found that there is a 37% overlap with emissions from FINN, providing both validation of the technique over known biomass burning regions, and an ability to quantify regions that are burning but not presently identified. Finally, we have a consistent and value-adding comparison and contrast with an EOF/PCA analysis in terms of both our regions classified as biomass burning and mixed/urban, with each approach offering its unique advantages and drawbacks. Although our approach has made some very simple assumptions in terms of cutoff that can and should be improved by the community, its robust results provide new insights into the rapid changes impacting CO throughout Asia, and will allow models to have an improved chance at representing peak events or areas undergoing rapid change.

Martínez-Alonso, S., M. Deeter, H. Worden, T. Borsdorff, I. Aben, R. Commane, B. Daube, G. Francis, M. George, J. Landgraf, D. Mao, K. McKain, and S. Wofsy (2020), 1.5 years of TROPOMI CO measurements: comparisons to MOPITT and ATom, Atmospheric Measurement Techniques, 13(9), 48414864, doi:
We have analyzed TROPOspheric Monitoring Instrument (TROPOMI) carbon monoxide (CO) data acquired between November 2017 and March 2019 with respect to other satellite (MOPITT, Measurement Of Pollution In The Troposphere) and airborne (ATom, Atmospheric Tomography mission) datasets to better understand TROPOMI’s contribution to the global tropospheric CO record (2000 to present). MOPITT and TROPOMI are two of only a few satellite instruments to ever derive CO from solar-reflected radiances. Therefore, it is particularly important to understand how these two datasets compare. Our results indicate that TROPOMI CO retrievals over land show excellent agreement with respect to MOPITT: relative biases and their SD (i.e., accuracy and precision) are on average 􀀀3:73%  11:51%, 􀀀2:24% 12:38%, and 􀀀3:22% 11:13% compared to the MOPITT TIR (thermal infrared), NIR (near infrared), and TIRCNIR (multispectral) products, respectively. TROPOMI and MOPITT data also show good agreement in terms of temporal and spatial patterns. Despite depending on solar-reflected radiances for its measurements, TROPOMI can also retrieve CO over bodies of water if clouds are present by approximating partial columns under cloud tops using scaled, model-based reference CO profiles. We quantify the bias of TROPOMI total column retrievals over bodies of water with respect to colocated in situ ATom CO profiles after smoothing the latter with the TROPOMI column averaging kernels (AKs), which account for signal attenuation under clouds (relative bias and its SDD 3:25% 11:46 %). In addition, we quantify enull (the null-space error), which accounts for differences between the shape of the TROPOMI reference profile and that of the ATom true profile (enull D 2:16% 2:23 %). For comparisons of TROPOMI and MOPITT retrievals over open water we compare TROPOMI total CO columns to their colocated MOPITT TIR counterparts. Relative bias and its SD are 2:98% 15:71% on average. We investigate the impact of discrepancies between the a priori and reference CO profiles (used by MOPITT and TROPOMI, respectively) on CO retrieval biases by applying a null-space adjustment (based on the MOPITT a priori) to the TROPOMI total column values. The effect of this adjustment on MOPITT and TROPOMI biases is minor, typically 12 percentage points.

Mekaumnuaychai, T., K. Suranowarath, T. Kanabkaew, and P. Lalitaporn (2020), Observations of Atmospheric Carbon Monoxide and Formaldehyde in Thailand Using Satellites., EnvironmentAsia, 13. [online] Available from: .
Carbon monoxide (CO) and formaldehyde (CH2O) are air pollutants playing an important role in the formation of tropospheric ozone (O3), which in turn have an influence on climate change. This study investigated the levels of CO and CH2O in Thailand during the periods of 2007 to 2017 (11 years). The observed data of CO were collected from the MOPITT satellite. For CH2O, the observed data were collected from the OMI satellite. Overall, during the study period, CO were detected at high levels from October to April and at low levels from May to September. For CH2O, the higher levels were detected from February to May while the lower levels were detected from June to September. Moreover, ground monitoring data of CO and CH2O were also obtained from the Pollution Control Department (PCD) from all over Thailand to compare with the satellite observed data. The results showed well correlated between satellite and ground CO levels in term of monthly pattern. However, the correlation between satellite and ground CH2O was relatively low. The results in this study showed that satellite observations of CO are useful to support ground measurements, particularly when ground monitoring stations are limited.

Miyazaki, K., K. Bowman, T. Sekiya, Z. Jiang, X. Chen, H. Eskes, M. Ru, Y. Zhang, and D. Shindell (2020a), Air Quality Response in China Linked to the 2019 Novel Coronavirus (COVID-19) Lockdown, Geophysical Research Letters, 47(19), e2020GL089252, doi:10.1029/2020GL089252.
Efforts to stem the spread of COVID-19 in China hinged on severe restrictions to human movement starting 23 January 2020 in Wuhan and subsequently to other provinces. Here, we quantify the ancillary impacts on air pollution and human health using inverse emissions estimates based on multiple satellite observations. We find that Chinese NOx emissions were reduced by 36% from early January to mid-February, with more than 80% of reductions occurring after their respective lockdown in most provinces. The reduced precursor emissions increased surface ozone by up to 16 ppb over northern China but decreased PM2.5 by up to 23 μg m−3 nationwide. Changes in human exposure are associated with about 2,100 more ozone-related and at least 60,000 fewer PM2.5-related morbidity incidences, primarily from asthma cases, thereby augmenting efforts to reduce hospital admissions and alleviate negative impacts from potential delayed treatments.

Miyazaki, K., K. W. Bowman, and K. Yumimoto (2020b), Evaluation of a multi-model, multi-constituent assimilation framework for tropospheric chemical reanalysis, Atmospheric Chemistry & Physics, 20(2), doi:DOI:10.5194/acp-20-931-2020. [online] Available from: .
We introduce a Multi-mOdel Multi-cOnstituent Chemical data assimilation (MOMO-Chem) framework that directly accounts for model error in transport and chemistry, and we integrate a portfolio of data assimilation analyses obtained using multiple forward chemical transport models in a state-of-the-art ensemble Kalman filter data assimilation system. The data assimilation simultaneously optimizes both concentrations and emissions of multiple species through ingestion of a suite of measurements (ozone, NO2, CO, HNO3) from multiple satellite sensors. In spite of substantial model differences, the observational density and accuracy was sufficient for the assimilation to reduce the multi-model spread by 20 %85 % for ozone and annual mean bias by 39 %97 % for ozone in the middle troposphere, while simultaneously reducing the tropospheric NO2 column biases by more than 40 % and the negative biases of surface CO in the Northern Hemisphere by 41 %94 %. For tropospheric mean OH, the multi-model mean meridional hemispheric gradient was reduced from 1.32 ± 0.03 to 1.19 ± 0.03, while the multimodel spread was reduced by 24 %58 % over polluted areas. The uncertainty ranges in the a posteriori emissions due to model errors were quantified in 4 %31 % for NOx and 13 %35 % for CO regional emissions. Harnessing assimilation increments in both NOx and ozone, we show that the sensitivity of ozone and NO2 surface concentrations to NOx emissions varied by a factor of 2 for end-member models, revealing fundamental differences in the representation of fast chemical and dynamical processes. A systematic investigation of model ozone response and analysis increment in MOMO-Chem could benefit evaluation of future prediction of the chemistryclimate system as a hierarchical emergent constraint.

Miyazaki, K., K. Bowman, T. Sekiya, H. Eskes, F. Boersma, H. Worden, N. Livesey, V. H. Payne, K. Sudo, Y. Kanaya, M. Takigawa, and K. Ogochi (2020c), Updated tropospheric chemistry reanalysis and emission estimates, TCR-2, for 20052018, Earth System Science Data, 12(3), 22232259, doi:

Abstract. This study presents the results from the Tropospheric Chemistry Reanalysis version 2 (TCR-2) for the period 20052018 at 1.1 horizontal resolution obtained from the assimilation of multiple updated satellite measurements of ozone, CO, NO2, HNO3, and SO2 from the OMI, SCIAMACHY, GOME-2, TES, MLS, and MOPITT satellite instruments. The reanalysis calculation was conducted using a global chemical transport model MIROC-CHASER and an ensemble Kalman filter technique that optimizes both chemical concentrations of various species and emissions of several precursors, which was efficient for the correction of the entire tropospheric profile of various species and its year-to-year variations. Comparisons against independent aircraft, satellite, and ozonesonde observations demonstrate the quality of the reanalysis fields for numerous key species on regional and global scales, as well as for seasonal, yearly, and decadal scales, from the surface to the lower stratosphere. The multi-constituent data assimilation brought the model vertical profiles and interhemispheric gradient of OH closer to observational estimates, which was important in improving the description of the oxidation capacity of the atmosphere and thus vertical profiles of various species. The evaluation results demonstrate the capability of the chemical reanalysis to improve understanding of the processes controlling variations in atmospheric composition, including long-term changes in near-surface air quality and emissions. The estimated emissions can be employed for the elucidation of detailed distributions of the anthropogenic and biomass burning emissions of co-emitted species (NOx, CO, SO2) in all major regions, as well as their seasonal and decadal variabilities. The data sets are available at (Miyazaki et al., 2019a).

Nandi, I., S. Srivastava, Y. Yarragunta, R. Kumar, and D. Mitra (2020), Distribution of surface carbon monoxide over the Indian subcontinent: Investigation of source contributions using WRF-Chem, Atmospheric Environment, 243, 117838, doi:10.1016/j.atmosenv.2020.117838.
This study investigates fractional contribution of different carbon monoxide (CO) sources over the Indian subcontinent at the surface in 2015 using a tagged tracer approach in the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). Model simulations are evaluated with respect to in-situ and satellite observations. The simulated CO levels reproduced in-situ observations in Pune, Anantapur, Udaipur, Ahmedabad, and Chennai reasonably well with mean bias ranging from −89.9 to 87.0 ppbv and RMSE ranging from 28 to 40% but a poor model performance was noticed in Hyderabad, Jabalpur, and Kanpur with larger mean bias (−259.0190.9 ppbv) and RMSE (4596%). Simulated CO concentrations are also compared with CO retrieved by MOPITT at 800 hPa and 200 hPa. At 800 hPa (200 hPa), the annual average WRF-Chem CO varies from 195 ± 69 to 224 ± 93 ppbv (102 ± 25 to 136 ± 21 ppbv) while MOPITT CO varies from 103 ± 26 to 114 ± 29 ppbv (103 ± 30 to 134 ± 33) over different Indian sub-regions. Over most of the regions, good correlation (coefficient of correlation > 0.7) is observed between simulated and satellite observed CO with mean bias of 92118 ppbv at 800 hPa and −4 to 3 ppbv at 200 hPa. Over the total Indian region, we find the highest contribution from anthropogenic emissions (CO-ANT) and inflow into the model domain from domain boundaries (CO-BACK) with 4546% contribution each and very small contribution (<5%) of biomass burning (CO-BIOM), biogenic (CO-BIOG) emissions, and photochemical production (CO-CHEM). Fractional contribution of these tracers are analysed over different Indian sub-regions. CO-ANT (2169%) and CO-BACK (2266%) contributions are found high throughout the year over all the Indian landmass regions. CO-BACK contribution is found to be maximum (7095%) over the Bay of Bengal and Arabian Sea. During winter season, CO-ANT and CO-BACK contribute 3269% and 2756% respectively over landmass regions of India. During spring, highest CO-BACK (66%) over Western India as compared to other landmass regions is attributed to CO inflow from the Arabian Peninsula and Middle East region. CO-BIOM contributes more than 22% in NE&M (North-East India and Myanmar) during spring due to slash and burn agriculture practice. During summer, transport of cleaner marine air and stronger vertical mixing are major causes of lower CO concentration over all sub-regions. During autumn, CO-ANT contributes 3370% over different landmass regions. Surface CO concentration is found to be mainly controlled by the direct anthropogenic emission in Indian megacities with a contribution exceeding 70% to CO in Delhi and Kolkata throughout the year.

Park, S., S.-W. Son, M.-I. Jung, J. Park, and S. S. Park (2020), Evaluation of tropospheric ozone reanalyses with independent ozonesonde observations in East Asia, Geosci. Lett., 7(1), 12, doi:10.1186/s40562-020-00161-9.
The modern reanalysis datasets provide not only meteorological variables, but also atmospheric chemical compositions such as tropospheric ozone and aerosol concentration. However, the quality of chemical compositions has been rarely assessed especially over East Asia. To better understand the characteristics of reanalysis datasets on regional scale, the present study evaluates tropospheric ozone derived from seven reanalyses against five independent ozonesonde observations in East Asia. The reanalysis datasets are the ECMWF Reanalysis 5th (ERA5), Monitoring Atmospheric Composition and Climate reanalysis (MACCRA), Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA), as well as the NCEP Climate Forecast System Reanalysis (CFSR), NASA Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2), Japanese 55-year Reanalysis (JRA-55), and updated Tropospheric Chemistry Reanalysis (TCR-2). It turns out that MACCRA, CAMSRA, and TCR-2, which incorporate chemical transport model, depict most reasonable spatio-temporal variability of tropospheric ozone in East Asia. The MACC exhibits a better quality with relatively small mean biases of 6.4 ± 1.3% in tropospheric column ozone than biases of 7.8 ± 2.7% and 7.8 ± 2.8% for CAMSRA and TCR-2. The CAMSRA further shows a significant monthly correlation with the observation of up to 0.7 at 850 hPa. Among the seven reanalyses, MACC, CAMSRA, and TCR-2 are suitable for local tropospheric ozone study on seasonal to inter-annual time scales. However, none of the seven reanalysis datasets reproduce the observed trend of tropospheric ozone. This result suggests that even the latest datasets are inadequate for the long-term ozone change study.

Pathakoti, M., A. Muppalla, S. Hazra, M. Dangeti, R. Shekhar, S. Jella, S. S. Mullapudi, P. Andugulapati, and U. Vijayasundaram (2020), An assessment of the impact of a nation-wide lockdown on air pollution - a remote sensing perspective over India, Atmospheric Chemistry and Physics Discussions, 116, doi:
The nation-wide lockdown imposed over India from 25th March 2020 onwards, in response to the COVID-19 pandemic, placed severe restrictions upon the industrial and transport sectors, which together form a significant chunk of anthropogenic emissions of pollutants into the atmosphere. Atmospheric concentrations of Nitrogen dioxide (NO2), carbon monoxide (CO) and aerosol optical depth (AOD) for lockdown and pre-lockdown periods were investigated with observations from Aura/OMI, Terra/MOPITT, Sentinel-5p/TROPOMI and Aqua-Terra/MODIS satellite sensors. Mean NO2 levels over India during the lockdown period showed a dip of 17&thinsp;% as compared to pre-lockdown period and a decrease of 18&thinsp;% against the 5-year average. Over New Delhi in particular, there was a sharp decrease of 62&thinsp;% in NO2 levels as compared to 2019 and a decline by 54&thinsp;% relative to the preceding 5-year period (2015&ndash;2019). Aerosol levels reduced over the country by ~&thinsp;24&thinsp;% from the 5-year mean levels, with a marked reduction over the Indo-Gangetic plains region. An increase in CO levels was noticeable, probably due to its longer life-time as compared to NO2 and aerosols. This study also reports the rate of change of NO2, CO and AOD, indicating increase/decrease in pollutant emissions over the different states of India.

Raispour, K., and Y. Khosravi (2020), Spatiotemporal Analysis of Carbon Monoxide Observed by Terra/MOPITT in the Troposphere of Iran, Pollution, 6(4), 759771, doi:10.22059/poll.2020.300275.770.
It has been more than 20 years that the Measurement of Pollution in The Troposphere (MOPITT) mission onboard the NASA Terra satellite keeps providing us CO atmospheric concentration measurements around the globe. The current paper observes CO mixing ratio from the MOPITT Version 8 (MOP03J_V008) instrument in order to study the spatiotemporal analysis of CO (spanning from April 2000 to February 2020) in the Troposphere of Iran. Results indicate that the average CO in Iran’s troposphere has been 133.5 ppbv (i.e., 5.5 ppbv lower than the global mean CO). The highest distribution of CO (with an average of 150 ppbv) belongs to the city of Tehran (the capital of Iran) as well as the Caspian Sea coastal area, while the lowest value (with an average of less than 110 ppbv) has been estimated on the Zagros Mountains (southwestern Iran). The highest and lowest CO values have been observed in cold and hot months, respectively. Seasonally speaking, it is also clear that the highest and lowest carbon monoxide values occur in winter and summer, respectively. The vertical profile of MOPITT CO shows the maximum CO concentration at lower levels of the troposphere. It has been expanded up to 150 hPa. The trend is investigated by means of Pearson correlation coefficient statistical method. Overall, long-term monitoring of MOPITT CO in Iran indicates a decreasing trend of tropospheric CO over the 20 years (Y=-0.008X+449.31). Possible reasons for such a decrease can be related to improved transportation fleet, increased fuel quality, plans for traffic control, promotion of heating systems, and promotion of industrial fuels and factories.

Rushingabigwi, G., P. Nsengiyumva, L. Sibomana, C. Twizere, and W. Kalisa (2020), Analysis of the atmospheric dust in Africa: The breathable dust’s fine particulate matter PM2.5 in correlation with carbon monoxide, Atmos. Environ., 224, 117319, doi:10.1016/j.atmosenv.2020.117319.
The dust has direct effects on people’s health and climate change; so, this research studied the remotely sensed dust deposition in Africa from 1980 to 2018, and the dust’s particulate matter of 2.5 mu m size (or PM2.5), in particular, which pollutes the breathable air. PM2.5 is studied in comparison with multispectral carbon monoxide (CO), an abundant atmospheric air pollutant in central Africa. CO is an atmospheric gaseous pollutant for which the smoke, a gaseous aerosol from incomplete combustion processes, is the biggest source. The literature clarifies that both the particulate matter and the CO endanger human health while breathed in. The dust from the desert of Sahara is windblown all over the world. CO, in Africa, is from the anthropogenic fire and volcanic eruptions’ smoke; these are two good reasons to have focused on Africa. Due to the big size of Africa, five sub-regions are set; these are the western, central, northern, eastern and southern sub-regions. The Goddard interactive online visualization and analysis infrastructure (GIOVANNI) has been a bridge to the collected remote sensing data, in this research. The data was collected online, from the measurement of pollution in the troposphere (MOPITT) as well as a second version of the modern era retrospective analysis for research and applications (MERRA-2); the analysis was done by a joint of the software tools, worth noting is the Arc GIS. As the amount of African dust dramatically increased by 2000; the heaviest in 2004, results are based on the selected dust deposition over 2000-2018: time-averaged maps, correlations, and quantitative estimations are reported in this research. The heaviest annual dust deposition reached 25.3 t/km(2) over the year 2004, in Liberia, a focal point of study for the western sub-region. An important finding: the dust’s PM2.5 positively correlated with multispectral CO from November to May; the positively high correlation coefficient was 0.86 in April 2018. The negative correlation between the two measurements started from June to October; the negatively high correlation was 0.68 in October 2015; this research discussed the possible reasons. This research recommends some onsite studies about the real figures and facts about the dust’s effects on health, in all the seasons; thus, an alert to policymakers who would set some strategies to mitigate the dust hazards on the health of African inhabitants, neighbors, and visitors.

Salimi, S., S. A. Hosseini, Z. Yarmoradi, J. Rezaei, and A. Bayat (2020), Statistical and synoptical analysis of China’s carbon monoxide emission and transportation using satellite images, Model. Earth Syst. Environ., 6(1), 301309, doi:10.1007/s40808-019-00679-8.
Air pollution, one of the most hazardous environmental problems in urban space is closely associated with the climate conditions. Today, pollution in the metropolitan has become an important issue which requires the management to provide practical solutions to improve biological conditions. Thus, recognizing the relationship between synoptic systems and air pollutants will contribute greatly to solving the environmental issues and for future planning. Hence, the present research was carried out to analyze the statisticalsynoptical aspects of China’s carbon monoxide (CO) emission and transfer during 201617. For this purpose, the number of pollutant days was extracted. Then, the synoptic patterns of pollutant days were analyzed using satellite images of CO concentration and mean sea level pressure. The results revealed that January and July periods, respectively, had the highest and lowest amount of CO in low- and high-pressure systems for the transfer of pollutant expansion. Also, based on the results, sub-tropical high pressure (STHP) was the main factor for CO transfer and compression of the western Pacific to the northern parts of the Pacific and the western coast of North America and Canada. The capability of absorption of low pressures and transfer of high pressures had a major role in lower atmospheric CO transfer of eastern and southeastern coasts of Asia to the Pacific Ocean regions. In terms of CO pollution, a correlation of 0.47 was, also, observed between two regions of China and the Pacific Ocean.

Schneising, O., M. Buchwitz, M. Reuter, H. Bovensmann, and J. P. Burrows (2020), Severe Californian wildfires in November 2018 observed from space: the carbon monoxide perspective., Atmospheric Chemistry & Physics, 20(6). [online] Available from: .
Due to proceeding climate change, some regions such as California face rising weather extremes with dry periods becoming warmer and drier, entailing the risk that wildfires and associated air pollution episodes will continue to increase. November 2018 turned into one of the most severe wildfire episodes on record in California, with two particularly destructive wildfires spreading concurrently through the north and the south of the state. Both fires ignited at the wildlandurban interface, causing many civilian fatalities and forcing the total evacuation of several cities and communities. Here we demonstrate that the inherent carbon monoxide (CO) emissions of the wildfires and subsequent transport can be observed from space by analysing radiance measurements of the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor satellite in the shortwave infrared spectral range. From the determined CO distribution we assess the corresponding air quality burden in major Californian cities caused by the fires and discuss the associated uncertainties. As a result of the prevailing wind conditions, the largest CO load during the first days of the fires is found in Sacramento and San Francisco, with city area averages reaching boundary layer concentration anomalies of about 2.5 mgCOm-3. Even the most polluted city scenes likely comply with the national ambient air quality standards (10 mgCOm-3 with 8 h averaging time). This finding based on dense daily recurrent satellite monitoring is consistent with isolated ground-based air quality measurements.

Tang, W., H. M. Worden, M. N. Deeter, D. P. Edwards, L. K. Emmons, S. Martinez-Alonso, B. Gaubert, R. R. Buchholz, G. S. Diskin, R. R. Dickerson, X. Red, H. He, and Y. Kondo (2020), Assessing Measurements of Pollution in the Troposphere (MOPITT) carbon monoxide retrievals over urban versus non-urban regions, Atmos. Meas. Tech., 13(3), 13371356, doi:10.5194/amt-13-1337-2020.
The Measurements of Pollution in the Troposphere (MOPITT) retrievals over urban regions have not been validated systematically, even though MOPITT observations are widely used to study CO over urban regions. Here we compare MOPITT products over urban and non-urban regions with aircraft measurements from the Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ - 2011-2014), Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC(4)RS - 2013), Air Chemistry Research In Asia (ARIAs - 2016), A-FORCE (2009, 2013), and Korea United States Air Quality (KORUS-AQ - 2016) campaigns. In general, MOPITT agrees reasonably well with the in situ profiles, over both urban and non-urban regions. Version 8 multispectral product (V8J) biases vary from -0.7% to 0.0% and version 8 thermal-infrared product (TIR) biases vary from 2.0% to 3.5 %. The evaluation statistics of MOPITT V8J and V8T over non-urban regions are better than those over urban regions with smaller biases and higher correlation coefficients. We find that the agreement of MOPITT V8J and V8T with aircraft measurements at high CO concentrations is not as good as that at low CO concentrations, although CO variability may tend to exaggerate retrieval biases in heavily polluted scenes. We test the sensitivities of the agreements between MOPITT and in situ profiles to assumptions and data filters applied during the comparisons of MOPITT retrievals and in situ profiles. The results at the surface layer are insensitive to the model-based profile extension (required due to aircraft altitude limitations), whereas the results at levels with limited aircraft observations (e.g., the 600 hPa layer) are more sensitive to the model-based profile extension. The results are insensitive to the maximum allowed time difference criterion for co-location (12, 6, 3, and 1 h) and are generally insensitive to the radius for co-location, except for the case where the radius is small (25 km), and hence few MOPITT retrievals are included in the comparison. Daytime MOPITT products have smaller overall biases than nighttime MOPITT products when comparing both MOPITT daytime and nighttime retrievals to the daytime aircraft observations. However, it would be premature to draw conclusions on the performance of MOPITT nighttime retrievals without nighttime aircraft observations. Applying signal-to-noise ratio (SNR) filters does not necessarily improve the overall agreement between MOPITT retrievals and in situ profiles, likely due to the reduced number of MOPITT retrievals for comparison. Comparisons of MOPITT retrievals and in situ profiles over complex urban or polluted regimes are inherently challenging due to spatial and temporal variabilities of CO within MOPITT retrieval pixels (i.e., footprints). We demonstrate that some of the errors are due to CO representativeness with these sensitivity tests, but further quantification of representativeness errors due to CO variability within the MOPITT footprint will require future work.

Wang, K., W. Wang, W. Wang, X. Jiang, T. Yu, and P. Ciren (2020a), Spatial Assessment of Health Economic Losses from Exposure to Ambient Pollutants in China, Remote Sensing, 12(5), 790, doi:10.3390/rs12050790.
Increasing emissions of ambient pollutants have caused considerable air pollution and negative health impact for human in various regions of China over the past decade. The resulting premature mortality and excessive morbidity caused huge human economic losses to the entire society. To identify the differences of health economic losses in various regions of China and help decision-making on targeting pollutants control, spatial assessment of health economic losses due to ambient pollutants in China is indispensable. In this study, to better represent the spatial variability, the satellite-based retrievals of the concentrations of various pollutants (PM10, PM2.5, O3, NO2, SO2 and CO) for the time period from 2007 to 2017 in China are used instead of using in-situ data. Population raster data were applied together with exposure-response function to calculate the spatial distribution of health impact and then the health impact is further quantified by using amended human capital (AHC) approach. The results which presented in a spatial resolution of 0.25&deg; &times; 0.25&deg;, show the signification contribution from the spatial assessment to revealing the spatial distribution and variance of health economic losses in various regions of China. Spatial assessment of overall health economic losses is different from conventional result due to more detail spatial information. This spatial assessment approach also provides an alternative method for losses measurement in other fields.

Wang, S., J. B. Cohen, C. Lin, and W. Deng (2020b), Constraining the relationships between aerosol height, aerosol optical depth and total column trace gas measurements using remote sensing and models, Atmos. Chem. Phys., 20(23), 1540115426, doi:10.5194/acp-20-15401-2020.
Proper quantification of the aerosol vertical height is essential to constrain the atmospheric distribution and lifetime of aerosols, as well as their impact on the environment. We use globally distributed, daily averaged measurements of aerosol stereo heights of fire aerosols from the Multi-angle Imaging SpectroRadiometer (MISR) to understand the aerosol distribution. We also connect these results with a simple plume rise model and a new multi-linear regression model approach based on daily measurements of NO2 from OMI and CO from MOPITT to understand and model the global aerosol vertical height profile over biomass burning regions. First, plumes associated with the local dry-burning season at midlatitudes to high latitudes frequently have a substantial fraction lofted into the free troposphere and in some cases even the stratosphere. Second, plumes mainly associated with less-polluted regions in developing countries and heavily forested areas tend to stay closer to the ground, although they are not always uniformly distributed throughout the boundary layer. Third, plumes associated with more serious loadings of pollution (such as in Africa, Southeast Asia and northeast China) tend to have a substantial amount of smoke transported uniformly through the planetary boundary layer and up to around 3 km. Fourth, the regression model approach yields a better ability to reproduce the measured heights compared to the plume rise model approach. This improvement is based on a removal of the negative bias observed from the plume model approach, as well as a better ability to work under more heavily polluted conditions. However, over many regions, both approaches fail, requiring deeper work to understand the physical, chemical and dynamical reasons underlying the failure over these regions.

Xue, L., A. Ding, O. Cooper, X. Huang, W. Wang, D. Zhou, Z. Wu, A. McClure-Begley, I. Petropavlovskikh, M. O. Andreae, and C. Fu (2020), ENSO and Southeast Asian biomass burning modulate subtropical trans-Pacific ozone transport, Natl Sci Rev, doi:10.1093/nsr/nwaa132. [online] Available from: .
Abstract.  Trans-Pacific transport of enhanced ozone plumes has been mainly attributed to fossil fuel combustion in Asia in spring, but less attention has been

Yin, S., X. Wang, M. Guo, H. Santoso, and H. Guan (2020a), The abnormal change of air quality and air pollutants induced by the forest fire in Sumatra and Borneo in 2015, Atmos. Res., 243, UNSP 105027, doi:10.1016/j.atmosres.2020.105027.
We comprehensively integrated various remote sensing, modeling and meteorological datasets to assess and quantify the effects of Indonesia’s forest fires in 2015 on the ambient atmosphere. When the forest fires occurred, the fire spots in Sumatra and Borneo increased sharply to 78,055 and fire radiative power (FRP) rose to 4.05 x 10(6) MW in September-October 2015. The Aerosol Optical Depth (AOD) and the retrieved concentration of PM2.5 around these two islands also peaked during this period. With the remote sensing data from 2016 and 2017 as the background, we found that the carbon monoxide (CO) anomalies along the equatorial Indian and Pacific Oceans (25 degrees S to 25 degrees N and 40 degrees E to 160 degrees E) reached 10.32 +/- 0.58 ML and 25.05 1.35 ML in September and October 2015, respectively. Meanwhile, the nitrogen dioxide (NO2) changes were not so obvious; the NO2 anomalies within Sumatra and Borneo were only 0.46 +/- 0.14 Kt and 0.49 +/- 0.17 Kt, respectively. All the four indicators (AOD, PM2 5 concentration, CO and NO2 anomalies) revealed that the ambient air quality in October 2015 was even worse than that in September. The precipitation anomaly (PA) of these two islands decreased to -1.89 mm/day in September 2015, which is assumed to be the main meteorological factor to induce the forest fires. During the 1997/1998 El Nino event, the PA decreased to -3.04 mm/day on October 1997 and temperature anomaly (TA) increased to 1.52 degrees C on March 1998, the variation of which is more significant than other two El Nino events in 1982/1983 and 2015/2016.

Yin, Y., A. A. Bloom, J. Worden, S. Saatchi, Y. Yang, M. Williams, J. Liu, Z. Jiang, H. Worden, K. Bowman, C. Frankenberg, and D. Schimel (2020b), Fire decline in dry tropical ecosystems enhances decadal land carbon sink, Nature Communications, 11(1), 1900, doi:10.1038/s41467-020-15852-2.
The terrestrial carbon sink has significantly increased in the past decades, but the underlying mechanisms are still unclear. The current synthesis of process-based estimates of land and ocean sinks requires an additional sink of 0.6 PgC yr−1 in the last decade to explain the observed airborne fraction. A concurrent global fire decline was observed in association with tropical agriculture expansion and landscape fragmentation. Here we show that a decline of 0.2 ± 0.1 PgC yr−1 in fire emissions during 20082014 relative to 20012007 also induced an additional carbon sink enhancement of 0.4 ± 0.2 PgC yr−1 attributable to carbon cycle feedbacks, amounting to a combined sink increase comparable to the 0.6 PgC yr−1 budget imbalance. Our results suggest that the indirect effects of fire, in addition to the direct emissions, is an overlooked mechanism for explaining decadal-scale changes in the land carbon sink and highlight the importance of fire management in climate mitigation.

Zhang, X., J. Liu, H. Han, Y. Zhang, Z. Jiang, H. Wang, L. Meng, Y. C. Li, and Y. Liu (2020), Satellite-Observed Variations and Trends in Carbon Monoxide over Asia and Their Sensitivities to Biomass Burning, Remote Sens., 12(5), 830, doi:10.3390/rs12050830.
As the carbon monoxide (CO) total column over Asia is among the highest in the world, it is important to characterize its variations in space and time. Using Measurements of Pollution in the Troposphere (MOPITT) and Atmospheric InfraRed Sounder (AIRS) satellite data, the variations and trends in CO total column over Asia and its seven subregions during 2003-2017 are investigated in this study. The CO total column in Asia is higher in spring and winter than in summer and autumn. The seasonal maximum and minimum are in spring and summer respectively in the regional mean over Asia, varying between land and oceans, as well as among the subregions. The CO total column in Asia shows strong interannual variation, with a regional mean coefficient of variation of 5.8% in MOPITT data. From 2003 to 2017, the annual mean of CO total column over Asia decreased significantly at a rate of (0.58 +/- 0.15)% per year (or -(0.11 +/- 0.03) x 10(17) molecules cm(-2) per year) in MOPITT data, resulting from significant CO decreases in winter, summer, and spring. In most of the subregions, significant decreasing trends in CO total column are also observed, more obviously over areas with high CO total column, including eastern regions of China and the Sichuan Basin. The regional decreasing trends in these areas are over 1% per year. Over the entire Asia, and in fire-prone subregions including South Siberia, Indo-China Peninsula, and Indonesia, we found significant correlations between the MOPITT CO total column and the fire counts from the Moderate Resolution Imaging Spectroradiometer (MODIS). The variations in MODIS fire counts may explain 58%, 60%, 36%, and 71% of the interannual variation in CO total column in Asia and these three subregions, respectively. Over different land cover types, the variations in biomass burning may explain 62%, 52%, and 31% of the interannual variation in CO total column, respectively, over the forest, grassland, and shrubland in Asia. Extremes in CO total column in Asia can be largely explained by the extreme fire events, such as the fires over Siberia in 2003 and 2012 and over Indonesia in 2006 and 2015. The significant decreasing trends in MODIS fire counts inside and outside Asia suggest that global biomass burning may be a driver for the decreasing trend in CO total column in Asia, especially in spring. In general, the variations and trends in CO total column over Asia detected by AIRS are similar to but smaller than those by MOPITT. The two datasets show similar spatial and temporal variations in CO total column over Asia, with correlation coefficients of 0.86-0.98 in the annual means. This study shows that the interannual variation in atmospheric CO in Asia is sensitive to biomass burning, while the decreasing trend in atmospheric CO over Asia coincides with the decreasing trend in MODIS fire counts from 2003 to 2017.


Ahn, D. H., T. Choi, J. Kim, S. S. Park, Y. G. Lee, S. J. Kim, and J. H. Koo (2019), Southern Hemisphere mid- and high-latitudinal AOD, CO, NO 2 , and HCHO: spatiotemporal patterns revealed by satellite observations, Progress in Earth and Planetary Science, 6(1), 34, doi:10.1186/s40645-019-0277-y.
To assess air pollution emitted in Southern Hemisphere mid-latitudes and transported to Antarctica, we investigate the climatological mean and temporal trends in aerosol optical depth (AOD), carbon monoxide (CO), nitrogen dioxide (NO 2 ), and formaldehyde (HCHO) columns using satellite observations. Generally, all these measurements exhibit sharp peaks over and near the three nearby inhabited continents: South America, Africa, and Australia. This pattern indicates the large emission effect of anthropogenic activities and biomass burning processes. High AOD is also found over the Southern Atlantic Ocean, probably because of the sea salt production driven by strong winds. Since the pristine Antarctic atmosphere can be polluted by transport of air pollutants from the mid-latitudes, we analyze the 10-day back trajectories that arrive at Antarctic ground stations in consideration of the spatial distribution of mid-latitudinal AOD, CO, NO 2 , and HCHO. We find that the influence of mid-latitudinal emission differs across Antarctic regions: western Antarctic regions show relatively more back trajectories from the mid-latitudes, while the eastern Antarctic regions do not show large intrusions of mid-latitudinal air masses. Finally, we estimate the long-term trends in AOD, CO, NO 2 , and HCHO during the past decade (20052016). While CO shows a significant negative trend, the others show overall positive trends. Seasonal and regional differences in trends are also discussed.

Borsdorff, T., J. aan de Brugh, S. Pandey, O. Hasekamp, U. Aben, S. Houweling, and J. Landgraf (2019), Carbon monoxide air pollution on sub-city scales and along arterial roads detected by the Tropospheric Monitoring Instrument, Atmos. Chem. Phys., 19(6), 35793588, doi:10.5194/acp-19-3579-2019.
The Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite provides measurements of carbon monoxide (CO) total column concentrations based on earthshine radiance measurements in the 2.3 mu m spectral range with a spatial resolution of 7km x 7km and daily global coverage. Due to the high accuracy of the observations, CO pollution can be detected over cities and industrial areas using single orbit overpasses. In this study, we analyzed local CO enhancements in an area around Iran from 1 November to 20 December 2017. We employed the Weather Research and Forecasting (WRF) model v3.8.1 using the EDGAR v4.2 emission inventory and evaluated CO emissions from the cities of Tehran, Yerevan, Urmia, and Tabriz on a spatial resolution comparable to that of TROPOMI. For background conditions, the WRF simulation agrees well with TROPOMI CO, with a mean difference of 5.7 %. However, the emissions for the city area had to be significantly increased in order to match the observations. Moreover, significant differences at the sub-city scale remain. To match the TROPOMI CO observations around the Armenian city of Yerevan, it is necessary to introduce CO emissions along a southeast arterial road of Yerevan. Overall, this hints at deficits in the EDGAR inventory in the region around Iran and indicates TROPOMI’s capability to identify localized CO pollution on sub-city scales, which at the same time challenges current atmospheric modeling at high spatial and temporal resolution.

Buchholz Rebecca, Worden Helen, Hammerling Dorit, Gaubert Benjamin, Emmons Louisa, and Wiedinmyer Christine (2019), Chemistry-Climate Links for Carbon Monoxide in Northern Hemisphere Boreal Fire Regions and an Assessment of Global Fire Inventories, Earth and Space Science Open Archive, doi:10.1002/essoar.10500487.1. [online] Available from: .
Fire emissions are a major contributor to atmospheric composition, affecting atmospheric oxidizing capacity and air quality. Transported amounts from Northern Hemisphere boreal fires can reach the pristine Arctic atmosphere as well as impact air quality in populated regions. Carbon monoxide (CO) is a useful trace gas emitted from fires that can be used to link extreme fire events with climate variability. We use our recently developed statistical tool to investigate the climate drivers of satellite measured CO variability in two Northern Hemisphere boreal fire regions: northwest Canada and Siberia. Our focus is on quantifying the ability of climate mode indices for the Pacific, Atlantic, Indian and Arctic Oceans in predicting CO amounts in these regions. Climate mode indices El Niño Southern Oscillation (ENSO), Tropical North Atlantic (TNA), the Dipole Mode Index (DMI) and the Arctic Oscillation (AO) are used to develop statistical models of column CO interannual variability from the Measurements of Pollution In The Troposphere (MOPITT) satellite instrument, for the time period covering 2001-2017. In addition, we assess the ability of fire emission inventories to reproduce CO, including the Fire Inventory from NCAR (FINN), the NASA Quick Fire Emissions Dataset (QFED) and the Copernicus Atmosphere Monitoring Service (CAMS) Global Fire Assimilation System (GFAS). These are implemented in the NCAR Community Atmosphere Model with chemistry (CAM-chem) and subsequently evaluated against MOPITT CO observations. Emission uncertainty contribution to inter-inventory differences are quantified, and the modeled contribution of fires to CO interannual variability is determined.

Cen Juhui, He, Wenying, and Chen, Hongbin (2019), Analysis of the difference in CO concentration between MOPITT and MLS at 200 hPa and its cause analysis, Climate and Environment Research. [online] Available from: .
The MLS (Microwave Limb Sounder) data with superior vertical resolution and inversion accuracy and MOPITT (Measurements of Pollution in the Troposphere) data have an intersection in the upper troposphere-lower stratosphere (UT-LS) area. Therefore, the CO data at the height of 200 hPa measured by MOPITT and MLS were compared and analyzed. The comparison results show that the distributions of the two are relatively close in the middle and low latitudes, and there are large-scale high-value central areas in central and western Africa, north-central South America, and Southeast Asia; MOPITT CO is significantly higher in concentration than MLS CO, and MOPITT CO There is a global systematic deviation of the concentration at low latitudes of about 35 ppb (10 ~ (-6)). The reason for the difference between MOPITT and MLS CO was analyzed through the CALIOP cloud layer data, which showed that the formation of the high-value CO region was related to the strong convection.

Cui Yueju (2019), CH_4 and CO anomalies related to Wenchuan and Lushan earthquakes, International Earthquake Dynamics. [online] Available from: .
Positive CH_4 is closely related to earthquake and tectonic activity, and its release can reflect the intensity of earthquake and tectonic activity. A large number of observations indicate that CH_4 anomalies are common in water, soil and atmosphere before and after the earthquake. CO is also one of the precursor parameters of seismic monitoring. Singh et al. (2010) used MOPITT satellite data to analyze changes in CO concentrations at different heights and found that CO concentrations increased a few days before the Gujarat 7.6 earthquake, indicating that CO gas should be earthquake precursor information and increase stress before earthquake. The resulting CO emissions are also thought to be associated with an abnormal increase in surface temperature a few days before the earthquake.

Deeter, M. N., D. P. Edwards, G. L. Francis, J. C. Gille, D. Mao, S. Martinez-Alonso, H. M. Worden, D. Ziskin, and M. O. Andreae (2019), Radiance-based retrieval bias mitigation for the MOPITT instrument: the version 8 product, Atmos. Meas. Tech., 12(8), 45614580, doi:10.5194/amt-12-4561-2019.
The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making nearly continuous observations of atmospheric carbon monoxide (CO) since 2000. Satellite observations of CO are routinely used to analyze emissions from fossil fuels and biomass burning, as well as the atmospheric transport of those emissions. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the version 8 (V8) product. V8 products benefit from updated spectroscopic data for water vapor and nitrogen used to develop the operational radiative transfer model and exploit a new method for minimizing retrieval biases through parameterized radiance bias correction. In situ datasets used for algorithm development and validation include the NOAA (National Oceanic and Atmospheric Administration) and HIPPO (HIAPER Pole-to-Pole Observations) datasets used for earlier MOPITT validation work in addition to measurements from the ACRIDICON-CHUVA (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems - Cloud processes of the main precipitation systems in Brazil: A contribution to cloud resolving modeling and to the GPM (Global Precipitation Measurement)), KORUS-AQ (The Korea-United States Air Quality Study), and ATom (The Atmospheric Tomography Mission) programs. Validation results illustrate clear improvements with respect to long-term bias drift and geographically variable retrieval bias. For example, whereas bias drift for the V7 thermal-infrared (TIR)-only product exceeded 0.5 % yr(-1) for levels in the upper troposphere (e.g., at 300 hPa), bias drift for the V8 TIR-only product is found to be less than 0.1 % yr(-1) at all levels. Also, whereas upper-tropospheric (300 hPa) retrieval bias in the V7 TIR-only product exceeded 10 % in the tropics, corresponding V8 biases are less than 5 % (in terms of absolute value) at all latitudes and do not exhibit a clear latitudinal dependence.

Hedelius, J. K., T.-L. He, D. B. A. Jones, B. C. Baier, R. R. Buchholz, M. De Maziere, N. M. Deutscher, M. K. Dubey, D. G. Feist, D. W. T. Griffith, F. Hase, L. T. Iraci, P. Jeseck, M. Kiel, R. Kivi, C. Liu, I. Morino, J. Notholt, Y.-S. Oh, H. Ohyama, D. F. Pollard, M. Rettinger, S. Roche, C. M. Roehl, M. Schneider, K. Shiomi, K. Strong, R. Sussmann, C. Sweeney, Y. Te, O. Uchino, V. A. Velazco, W. Wang, T. Warneke, P. O. Wennberg, H. M. Worden, and D. Wunch (2019), Evaluation of MOPITT Version 7 joint TIR-NIR X-CO retrievals with TCCON, Atmos. Meas. Tech., 12(10), 55475572, doi:10.5194/amt-12-5547-2019.
Observations of carbon monoxide (CO) from the Measurements Of Pollution In The Troposphere (MOPITT) instrument aboard the Terra spacecraft were expected to have an accuracy of 10% prior to the launch in 1999. Here we evaluate MOPITT Version 7 joint (V7J) thermal-infrared and near-infrared (TIR-NIR) retrieval accuracy and precision and suggest ways to further improve the accuracy of the observations. We take five steps involving filtering or bias corrections to reduce scatter and bias in the data relative to other MOPITT soundings and ground-based measurements. (1) We apply a preliminary filtering scheme in which measurements over snow and ice are removed. (2) We find a systematic pairwise bias among the four MOPITT alongtrack detectors (pixels) on the order of 3-4 ppb with a small temporal trend, which we remove on a global scale using a temporally trended bias correction. (3) Using a small-region approximation (SRA), a new filtering scheme is developed and applied based on additional quality indicators such as the signal-to-noise ratio (SNR). After applying these new filters, the root-mean-squared error computed using the local median from the SRA over 16 years of global observations decreases from 3.84 to 2.55 ppb. (4) We also use the SRA to find variability in MOPITT retrieval anomalies that relates to retrieval parameters. We apply a bias correction to one parameter from this analysis. (5) After applying the previous bias corrections and filtering, we compare the MOPITT results with the GGG2014 ground-based Total Carbon Column Observing Network (TCCON) observations to obtain an overall global bias correction. These comparisons show that MOPITT V7J is biased high by about 6 %-8 %, which is similar to past studies using independent validation datasets on V6J. When using TCCON spectrometric column retrievals without the standard airmass correction or scaling to aircraft (WMO scale), the ground- and satellite-based observations overall agree to better than 0.5 %. GEOS-Chem data assimilations are used to estimate the influence of filtering and scaling to TCCON on global CO and tend to pull concentrations away from the prior fluxes and closer to the truth. We conclude with suggestions for further improving the MOPITT data products.

Huijnen, V., A. Pozzer, J. Arteta, G. Brasseur, I. Bouarar, S. Chabrillat, Y. Christophe, T. Doumbia, J. Flemming, J. Guth, B. Josse, V. A. Karydis, V. Marécal, and S. Pelletier (2019), Quantifying uncertainties due to chemistry modelling evaluation of tropospheric composition simulations in the CAMS model (cycle 43R1), Geoscientific Model Development, 12(4), 17251752, doi:
We report on an evaluation of tropospheric ozone and its precursor gases in three atmospheric chemistry versions as implemented in the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS), referred to as IFS(CB05BASCOE), IFS(MOZART) and IFS(MOCAGE). While the model versions were forced with the same overall meteorology, emissions, transport and deposition schemes, they vary largely in their parameterisations describing atmospheric chemistry, including the organics degradation, heterogeneous chemistry and photolysis, as well as chemical solver. The model results from the three chemistry versions are compared against a range of aircraft field campaigns, surface observations, ozone-sondes and satellite observations, which provides quantification of the overall model uncertainty driven by the chemistry parameterisations. We find that they produce similar patterns and magnitudes for carbon monoxide (CO) and ozone (O3), as well as a range of non-methane hydrocarbons (NMHCs), with averaged differences for O3 (CO) within 10&thinsp;% (20&thinsp;%) throughout the troposphere. Most of the divergence in the magnitude of CO and NMHCs can be explained by differences in OH concentrations, which can reach up to 50&thinsp;%, particularly at high latitudes. There are also comparatively large discrepancies between model versions for NO2, SO2 and HNO3, which are strongly influenced by secondary chemical production and loss. Other common biases in CO and NMHCs are mainly attributed to uncertainties in their emissions. This configuration of having various chemistry versions within IFS provides a quantification of uncertainties induced by chemistry modelling in the main CAMS global trace gas products beyond those that are constrained by data assimilation.

Inness, A., M. Ades, A. Agustí-Panareda, J. Barré, A. Benedictow, A.-M. Blechschmidt, J. J. Dominguez, R. Engelen, H. Eskes, J. Flemming, V. Huijnen, L. Jones, Z. Kipling, S. Massart, M. Parrington, V.-H. Peuch, M. Razinger, S. Remy, M. Schulz, and M. Suttie (2019), The CAMS reanalysis of atmospheric composition, Atmospheric Chemistry and Physics, 19(6), 35153556, doi:
The Copernicus Atmosphere Monitoring Service (CAMS) reanalysis is the latest global reanalysis dataset of atmospheric composition produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), consisting of three-dimensional time-consistent atmospheric composition fields, including aerosols and chemical species. The dataset currently covers the period 20032016 and will be extended in the future by adding 1 year each year. A reanalysis for greenhouse gases is being produced separately. The CAMS reanalysis builds on the experience gained during the production of the earlier Monitoring Atmospheric Composition and Climate (MACC) reanalysis and CAMS interim reanalysis. Satellite retrievals of total column CO; tropospheric column NO2; aerosol optical depth (AOD); and total column, partial column and profile ozone retrievals were assimilated for the CAMS reanalysis with ECMWF’s Integrated Forecasting System. The new reanalysis has an increased horizontal resolution of about 80&thinsp;km and provides more chemical species at a better temporal resolution (3-hourly analysis fields, 3-hourly forecast fields and hourly surface forecast fields) than the previously produced CAMS interim reanalysis. The CAMS reanalysis has smaller biases compared with most of the independent ozone, carbon monoxide, nitrogen dioxide and aerosol optical depth observations used for validation in this paper than the previous two reanalyses and is much improved and more consistent in time, especially compared to the MACC reanalysis. The CAMS reanalysis is a dataset that can be used to compute climatologies, study trends, evaluate models, benchmark other reanalyses or serve as boundary conditions for regional models for past periods.

Kang, H., B. Zhu, R. J. van der A, C. Zhu, G. de Leeuw, X. Hou, and J. Gao (2019), Natural and anthropogenic contributions to long-term variations of SO2, NO2, CO, and AOD over East China, Atmospheric Research, 215, 284293, doi:10.1016/j.atmosres.2018.09.012.
Concentrations of atmospheric pollutants over East China have varied considerably during the past decades. These variations are partly due to variations of human activities, e.g., increasing energy consumption and implementation of government emission control policies, and partly to natural fluctuations. This study aims to separate the effects of natural processes and anthropogenic activities on the increase/decrease of the concentrations of some of the most important pollutants (SO2, NO2, CO and aerosols) over East China in the last decade. This was achieved by the comparison of the temporal variations in long-term time series of satellite-retrieved aerosol optical depth (AOD) and vertical column densities (VCDs) of SO2, NO2, and CO, with those in model-simulated time series of the natural variations only. The latter were created by the use of the same anthropogenic emissions throughout the whole simulation, while using re-analysis data (MERRA) to describe meteorological processes and natural emissions. Thus, the comparison between observed and simulated temporal variations reveals the effects due to anthropogenic emissions only, assuming that the atmospheric processes affect natural and anthropogenic species in the same way. In the analysis, a KolmogorovZurbenko (KZ) filter is used to extract long-term components from both the observed and simulated data and normalization to the situation at a certain reference point is used to eliminate bias between observations and simulations. By this new method, natural and anthropogenic contributions to long-term variations of trace gases and AOD are quantitatively estimated. The results show that NO2 VCDs increased from 2004 to 2011 by 76% and of the overall increase in this period only 1% ± 1% was attributed to natural factors, 99% ± 1% attributed to anthropogenic factors. AOD increased by 24% between 2001 and 2011 and of the overall increase 24% ± 32% was due to natural factors and 76% ± 32% was due to anthropogenic factors. SO2 VCDs decreased by 15% from 2007 to 2013, natural and anthropogenic factors contributed respectively 16% ± 14% and 84% ± 14% to the overall decrease in this period. CO decreased since 2003 with 13% and of the overall decrease 6% ± 6% was due to natural factors and 94% ± 6% was due to anthropogenic factors.

Lin, Chuyong, Wang, Shuo, and Cohen, Jason (2019), AN INTER-COMPARISON OF THE SPATIAL AND TEMPORAL CHARACTERISTICS OF CO OVER HIGH FIRE REGIONS BASED ON MOPITT AND GFED, The International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences, doi:DOI:10.5194/isprs-archives-XLII-3-W9-119-2019. [online] Available from: .
The  spatial  and  temporal  distributions  of  Carbon  Monoxide  (CO)  as  measured  by  the  Moderate  Resolution  Imaging spectroradiometer (MOPITT) instrument are analyzedin depth in this work. We specifically look at how these values, their statistics and their trends behave from 2000 to 2018 over regions defined ashigh fire regions, based on the carbon emissions productfrom the Global  Fire  Emission  Database  (GFED).Our  results  indicate  that  there  are  significant  differences  in  the  timing,  duration,  and magnitude  of  the  fires as  measured  by  MOPITTover  different high fire  regions.Our  results  are  alsodifferent  from  past  studies which  have  relied  upon remotely  sensedaerosol  measurements,  such  as  AOD.  Over  these  high  fire  regions,  we  find  that  the  fires contribute the vast majority of the CO loading, which always occurs over a short periodof time, on order of weeks. Over7regions studied,  we  have  found  a  statistically  significant  decreasing  trend,  albeit  smaller  than  the  measurement  error.  The  correlation between the MOPITT and GFED approaches if found to be reliableover the regions where the two datasets overlap. We finally find evidence for possible long-rangetransport of CO from one fire region to another.

Liu, D., B. Di, Y. Luo, X. Deng, H. Zhang, F. Yang, M. L. Grieneisen, and Y. Zhan (2019), Estimating ground-level CO concentrations across China based on the national monitoring network and MOPITT: potentially overlooked CO hotspots in the Tibetan Plateau, Atmospheric Chemistry and Physics, 19(19), 1241312430, doi:
Given its relatively long lifetime in the troposphere, carbon monoxide (CO) is commonly employed as a tracer for characterizing airborne pollutant distributions. The present study aims to estimate the spatiotemporal distributions of ground-level CO concentrations across China during 20132016. We refined the random-forestspatiotemporal kriging (RFSTK) model to simulate the daily CO concentrations on a 0.1 grid based on the extensive CO monitoring data and the Measurements of Pollution in the Troposphere CO retrievals (MOPITT CO). The RFSTK model alleviated the negative effects of sampling bias and variance heterogeneity on the model training, with cross-validation R2 of 0.51 and 0.71 for predicting the daily and multiyear average CO concentrations, respectively. The national population-weighted average CO concentrations were predicted to be 0.99±0.30&thinsp;mg&thinsp;m−3 (μ±σ) and showed decreasing trends over all regions of China at a rate of -0.021±0.004&thinsp;mg&thinsp;m−3&thinsp;yr−1. The CO pollution was more severe in North China (1.19±0.30&thinsp;mg&thinsp;m−3), and the predicted patterns were generally consistent with MOPITT CO. The hotspots in the central Tibetan Plateau where the CO concentrations were underestimated by MOPITT CO were apparent in the RFSTK predictions. This comprehensive dataset of ground-level CO concentrations is valuable for air quality management in China.

Miyazaki, K., T. Sekiya, D. Fu, K. W. Bowman, S. S. Kulawik, K. Sudo, T. Walker, Y. Kanaya, M. Takigawa, K. Ogochi, H. Eskes, K. F. Boersma, A. M. Thompson, B. Gaubert, J. Barre, and L. K. Emmons (2019), Balance of Emission and Dynamical Controls on Ozone During the Korea-United States Air Quality Campaign From Multiconstituent Satellite Data Assimilation, Journal of Geophysical Research: Atmospheres, 124(1), 387413, doi:10.1029/2018JD028912.
Global multiconstituent concentration and emission fields obtained from the assimilation of the satellite retrievals of ozone, CO, NO2, HNO3, and SO2 from the Ozone Monitoring Instrument (OMI), Global Ozone Monitoring Experiment 2, Measurements of Pollution in the Troposphere, Microwave Limb Sounder, and Atmospheric Infrared Sounder (AIRS)/OMI are used to understand the processes controlling air pollution during the Korea-United States Air Quality (KORUS-AQ) campaign. Estimated emissions in South Korea were 0.42 Tg N for NOx and 1.1 Tg CO for CO, which were 40% and 83% higher, respectively, than the a priori bottom-up inventories, and increased mean ozone concentration by up to 7.5 ± 1.6 ppbv. The observed boundary layer ozone exceeded 90 ppbv over Seoul under stagnant phases, whereas it was approximately 60 ppbv during dynamical conditions given equivalent emissions. Chemical reanalysis showed that mean ozone concentration was persistently higher over Seoul (75.10 ± 7.6 ppbv) than the broader KORUS-AQ domain (70.5 ± 9.2 ppbv) at 700 hPa. Large bias reductions (>75%) in the free tropospheric OH show that multiple-species assimilation is critical for balanced tropospheric chemistry analysis and emissions. The assimilation performance was dependent on the particular phase. While the evaluation of data assimilation fields shows an improved agreement with aircraft measurements in ozone (to less than 5 ppbv biases), CO, NO2, SO2, PAN, and OH profiles, lower tropospheric ozone analysis error was largest at stagnant conditions, whereas the model errors were mostly removed by data assimilation under dynamic weather conditions. Assimilation of new AIRS/OMI ozone profiles allowed for additional error reductions, especially under dynamic weather conditions. Our results show the important balance of dynamics and emissions both on pollution and the chemical assimilation system performance.

Mohan, S., and P. Saranya (2019), Assessment of tropospheric ozone at an industrial site of Chennai megacity, J. Air Waste Manage. Assoc., 69(9), 10791095, doi:10.1080/10962247.2019.1604451.
This paper presents the temporal variation in surface-level ozone (O-3) measured at Gummidipoondi near Chennai, Tamilnadu. The site chosen for the present study has high potential for ozone generation sources, such as vehicular traffic and industrial activities. The site is also located near a hazardous waste management facility. The key sources of nitrogen oxides (NOx), which are considered to be an important precursor of O-3, include hazardous waste incineration, trucks bringing the hazardous wastes, and vehicles plying on the nearby National Highway 16 (NH 16). The measurements clearly showed diurnal variation, with maximum values observed during the noon hours and minimum values observed when solar radiation was less. The data showed a marked seasonal variation in O-3, with the highest hourly average O-3 concentration (497.2 mu g/m(3)) in the summer season. Consequently, in order to identify the long-range transport sources adding to the increased O-3 levels, backward trajectories were computed using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. It was found that the polluted air mass originated from the Southeast Asian region and the Indo-Gangetic Plain. The polluted air mass, which advected large amounts of carbon monoxide (CO) plumes, was analyzed using the Measurement of Pollution in the Troposphere (MOPITT) retrievals. The correlations of O-3 with temperature (r = 0.746; P < 0.01) and solar radiation (r = 0.751; P < 0.01) were strongly positive, and that with NOx was found to be negative. Stronger correlation of O-3 with NOx was observed during pre-monsoon months (r = 0.627; P < 0.01) and following hours of photochemical reactions. There were substantial differences in concentrations between weekdays and weekends, with higher nitric oxide (NO) and nitrogen dioxide (NO2), but lower O-3, concentrations on weekdays. A substantial weekday-weekend difference in O-3, which was higher on weekends, appears to be attributable to lower daytime traffic activity and hence reduced emissions of NOx to a “NOx-saturated” atmosphere. Implications: The assessment of ground-level ozone in an industrial area with hazardous waste management facility is very important, as there is high possibility for more generation of tropospheric ozone. Since the location of the study area is coastal, wind plays a major role in O-3 transportation; hence, the effects of wind speed and wind direction have been studied in different seasons. When compared with the other studies carried out in different places across India, the present study area has recorded much greater O-3 mixing ratio. This study can be useful for setting up control strategies in such industrial areas.

Shan, C., W. Wang, C. Liu, Y. Sun, Q. Hu, X. Xu, Y. Tian, H. Zhang, I. Morino, D. W. T. Griffith, and V. A. Velazco (2019), Regional CO emission estimated from ground-based remote sensing at Hefei site, China, Atmospheric Research, 222, 2535, doi:10.1016/j.atmosres.2019.02.005.
Carbon monoxide (CO) is regarded as a useful tracer of biomass burning and anthropogenic pollution, so CO measurements can provide valuable information about the intensity of various anthropogenic activities. However, the emission estimates of CO based on inventories are associated with high uncertainties, especially in China. As CO is co-emitted with CO2 in the combustion of carbonaceous fuels, the relationship between CO and CO2 is often used to estimate regional CO emissions. Hefei is located in the area of eastern central China, which is one of the most industrialized regions in China, with severe regional air pollution. The enhancement slopes of ∆CO to ∆CO2 were calculated and compared from ground-based remote sensing observations, surface in-situ measurements, satellite and emission inventory data at the Hefei site during the period from September 2015 to August 2017. Both inventory based ratios of ΔCO to ΔCO2 are significantly larger than the ratios based on the observation data, including Fourier Transform Spectrometer (FTS) data, in-situ data, and satellite data. Further the CO emissions in the central China were estimated from the enhancement slopes of ∆CO/∆CO2 combined with the CO2 emission inventory. The CO emission estimated from the ground-based FTS observations and the Peking University (PKU) inventory based CO2 emission is about 10.96 ± 0.88 and 11.95 ± 0.71 Tg CO yr−1 during the 20152016 and the 20162017 period, respectively. The CO emission estimated from the ground-based FTS observations and the Emission Database for Global Atmospheric Research (EDGAR) inventory based CO2 emission is about 11.27 ± 0.91 and 12.35 ± 0.74 Tg CO yr−1, respectively. So the CO emissions estimated from the ground-based FTS data and the different inventory based CO2 emission show a good agreement. However, CO emissions derived from FTS data are substantially lower than those calculated directly from the inventories, i.e. there is a large difference between CO emissions derived from FTS and CO emissions directly derived from the two inventories. The phenomenon suggests that the emission inventories greatly overestimate the actual CO emission in the study area. This study estimates the regional CO emissions from ground-based remote sensing observations and investigates how much the difference is between the emissions from inventories and ground-based measurements.

Sitnov, S. A., and I. I. Mokhov (2019), Variations in atmospheric composition over Northern Eurasia regions under weather and climate anomalies associated with atmospheric blocking events, IOP Conf. Ser.: Earth Environ. Sci., 231, 012049, doi:10.1088/1755-1315/231/1/012049.
Changes in the composition of the atmosphere associated with the atmospheric blocking events were analyzed using the measurements of ozone, water vapor, methane, formaldehyde, carbon monoxide, nitrogen dioxide, as well as aerosol optical characteristics from the satellite instruments OMI, MLS, AIRS, MODIS and MOPITT as well as ground-based, balloon and NCEP/NCAR reanalysis data. The changes in atmospheric composition associated with pyrogenic, biogenic and soil emissions of aerosol and gas constituents as well as the changes due to the regional peculiarities of the large-scale atmospheric dynamics are discussed.

Tang, W., A. F. Arellano, B. Gaubert, K. Miyazaki, and H. M. Worden (2019a), Satellite data reveal a common combustion emission pathway for major cities in China, Atmospheric Chemistry and Physics, 19(7), 42694288, doi:
Extensive fossil fuel combustion in rapidly developing cities severely affects air quality and public health. We report observational evidence of decadal changes in the efficiency and cleanness of bulk combustion over large cities in mainland China. In order to estimate the trends in enhancement ratios of CO and SO2 to NO2 (ΔCO∕ΔNO2 and ΔSO2∕ΔNO2) and infer emergent bulk combustion properties over these cities, we combine air quality retrievals from widely used satellite instruments across 20052014. We present results for four Chinese cities (Shenyang, Beijing, Shanghai, and Shenzhen) representing four levels of urban development. Our results show a robust coherent progression of declining to growing ΔCO∕ΔNO2 relative to 2005 (−5.4±0.7 to +8.3±3.1% yr−1) and slowly declining ΔSO2∕ΔNO2 (−6.0±1.0 to −3.4±1.0 % yr−1) across the four cities. The coherent progression we find is not evident in the trends of emission ratios reported in Representative Concentration Pathway (RCP8.5) inventory. This progression is likely due to a shift towards cleaner combustion from industrial and residential sectors in Shanghai and Shenzhen that is not yet seen in Shenyang and Beijing. This overall trend is presently obfuscated by China’s still relatively higher dependence on coal. Such progression is well-correlated with economic development and traces a common emission pathway that resembles evolution of air pollution in more developed cities. Our results highlight the utility of augmenting observing and modeling capabilities by exploiting enhancement ratios in constraining the time variation in emission ratios in current inventories. As cities and/or countries continue to socioeconomically develop, the ability to monitor combustion efficiency and effectiveness of pollution control becomes increasingly important in assessing sustainable control strategies.

Tang, W., L. K. Emmons, A. F. Arellano, B. Gaubert, C. Knote, S. Tilmes, R. R. Buchholz, G. G. Pfister, G. S. Diskin, D. R. Blake, N. J. Blake, S. Meinardi, J. P. DiGangi, Y. Choi, J.-H. Woo, C. He, J. R. Schroeder, I. Suh, H.-J. Lee, H.-Y. Jo, Y. Kanaya, J. Jung, Y. Lee, and D. Kim (2019b), Source Contributions to Carbon Monoxide Concentrations During KORUS-AQ Based on CAM-chem Model Applications, J. Geophys. Res.-Atmos., 124(5), 27962822, doi:10.1029/2018JD029151.
We investigate regional sources contributing to CO during the Korea United States Air Quality (KORUS-AQ) campaign conducted over Korea (1 May to 10 June 2016) using 17 tagged CO simulations from the Community Atmosphere Model with chemistry (CAM-chem). The simulations use three spatial resolutions, three anthropogenic emission inventories, two meteorological fields, and nine emission scenarios. These simulations are evaluated against measurements from the DC-8 aircraft and Measurements Of Pollution In The Troposphere (MOPITT). Results show that simulations using bottom-up emissions are consistently lower (bias: -34 to -39%) and poorer performing (Taylor skill: 0.38-0.61) than simulations using alternative anthropogenic emissions (bias: -6 to -33%; Taylor skill: 0.48-0.86), particularly for enhanced Asian CO and volatile organic compound (VOC) emission scenarios, suggesting underestimation in modeled CO background and emissions in the region. The ranges of source contributions to modeled CO along DC-8 aircraft from Korea and southern (90 degrees E to 123 degrees E, 20 degrees N to 29 degrees N), middle (90 degrees E to 123 degrees E, 29 degrees N to 38.5 degrees N), and northern (90 degrees E to 131.5 degrees E, 38.5 degrees N to 45 degrees N) East Asia (EA) are 6-13%, similar to 5%, 16-28%, and 9-18%, respectively. CO emissions from middle and northern EA can reach Korea via transport within the boundary layer, whereas those from southern EA are transported to Korea mainly through the free troposphere. Emission contributions from middle EA dominate during continental outflow events (29-51%), while Korean emissions play an overall more important role for ground sites (up to 25-49%) and plumes within the boundary layer (up to 25-44%) in Korea. Finally, comparisons with four other source contribution approaches (FLEXPART 9.1 back trajectory calculations driven by Weather Research and Forecasting (WRF) WRF inert tracer, China signature VOCs, and CO to CO2 enhancement ratios) show general consistency with CAM-chem.

Ustinov, V. P., E. L. Baranova, K. N. Visheratin, M. I. Grachev, and A. V. Kal’sin (2019a), Carbon Monoxide Variations in the Antarctic Atmosphere from Ground-Based and Satellite Measurement Data, Izv. Atmos. Ocean. Phys., 55(9), 12101217, doi:10.1134/S0001433819090536.
The results of systematic (2003-2017) measurements of the total content and height-averaged relative volume concentration of CO at st. Novolazarevskaya with a spectrometer with a resolution of 0.2 cm(-1) are presented. The inverse problem of determining the total content of CO as well as interfering gases (H2O and N2O) was solved using the SFIT4 software package. A data analysis indicated that during the measurements the average total CO content at st. Novolazarevskaya was (8 +/- 2) 10(17) molecules/cm(2) and the height-averaged volume concentration was (37 +/- 8) ppb. The resulting data were compared with variations in the total CO content at st. Arrival-Heights, MOPITT satellite data, and CO surface concentrations at st. Syowa. The maximum and minimum values of CO were observed in September and January-February, respectively. For all the data series considered, the trends are insignificant; in this case, an increased CO content was observed in 2010, and an increasing trend of the minimum values of CO was observed in recent years (2014-2017). Both stations (Novolazarevskaya and Arrival-Heights) are characterized by an excess of satellite data over ground-based measurement data (19% and 14%, respectively); here, a seasonal dependence of the deviation was observed with minimal deviations in December-January. Data of surface measurements of the total content at st. Novolazarevskaya and Arrival-Heights are rather well consistent, and the average deviation since 2010 was 2.4%. The average concentration of CO at st. Syowa (51 ppb) is higher than the height-averaged concentration at st. Novolazarevskaya. According to spectral, wavelet, and composite analyzes, all data series considered include oscillations in the range of 6-45 months with almost identical periods and phase relationships.

Ustinov, V. P., У. В. П, E. L. Baranova, Б. Е. Л, K. N. Visheratin, В. К. Н, M. I. Grachev, Г. М. И, A. V. Kalsin, and К. А. В (2019b), Variations of carbon monoxide in the atmosphere of Antarctica according to ground-based and satellite measurements, Исследования Земли из Космоса, 0(2), 97106, doi:10.31857/S0205-96142019297-106.
The results of systematic (20032017) measurements of the total content and the volume mixing ratio of CO at Novolazarevskaya station with a spectrometer with a resolution of 0.2 cm 1 are presented. The inverse problem of determining the total CO content, as well as interfering gases (H2O and N2O), was solved using the SFIT4 software package. Data analysis showed that over the measurement period the average total CO content at Novolazarevskaya amounted to (8 ± 2) 1017 molec/cm2, and the average volume mixing ratio amounted to (37 ± 8) ppb. The obtained data are compared with variations in the total content of CO in Arrival-Heights station, with MOPITT satellite data, as well as with surface values of CO concentration at Syova station. The maximum values of CO are observed in September, the minimum in JanuaryFebruary. For all the considered series, the trends are insignificant, while there are periods of increased CO content (2010). In recent years (20142017) there is a tendency towards an increase in the minimum values of CO. For  Novolazarevskaya and  Arrival-Heights satellite data are characterized by the excess of over ground data, amounting to 19% and 14%, respectively, while there is a seasonal dependence of the deviation with the minimum in DecemberJanuary. Surface measurements of the total CO content are in fairly good agreement at Novolazarevskaya and Arrival-Heights, and since 2010 the average deviation is 2.4%. The average value of the concentration of CO on Syova 51 ppb is higher than the average volume mixing ratio at Novolazarevskaya. According to the spectral, wavelet and composite analyzes, in all the considered series there are oscillations in the range of 645 months with closely coinciding periods and phases.

Wang, S., C. Y. Lin, and J. B. Cohen (2019), COMPARING A RANGE OF SIMPLE PLUME RISE MODELS AND MISR AEROSOL HEIGHT MEASUREMENTS, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-3/W9, 165170, doi:10.5194/isprs-archives-XLII-3-W9-165-2019.
Rapid economic development leads to increasing sources of aerosols from both urban and biomass sources, which in turn have a significant impact on the atmosphere and the environment. There are significant differences however between urban sources, which tend to be emitted at low temperature, and biomass sources, which are co-emitted with a significant amount of heat. In this work, we first analyse the spatial and temporal distribution of aerosol height from 3.5 years of day-by-day global measurements of aerosol plume height from MISR from January 2008 through June of 2011). We next use a simple plume rise model (PRM) based on FRP and various meteorological variables both from MISR and from other data sources. We find that the PRM makes a reasonable reproduction of the MISR measurements in Western Siberia, Alaska, Central Canada, Argentina, and Eastern Europe, although it underestimates the MISR measurements everywhere. We compute the amount of aerosol above the boundary layer as well as its distribution, and find that the PRM can only come close to reproducing this in conditions which are dry and found in extra-tropical regions. In specific we find that there is a slight model improvement when we apply factors to the wind speed. In general, we find the results are optimized when wind speed is adjusted by 20% around the given mean value, and the vertical velocity is adjusted by -20% to +40% of the original value. The best fitting region, Argentina, is obtained with an RMS error (model biased low) of 0.39km, when the horizontal wind is unadjusted and the vertical wind is adjusted by -20%. We further find that the PRM approach is not applicable over those regions which have the highest magnitude of aerosol emissions, as detected by OMI and MOPITT measurements of NO2 and CO respectively, leading to future plans on how to correct for and improve this approach.

Weir, B., S. Crowell, S. R. Kawa, L. Ott, A. Chatterjee, S. Pawson, and B. Moore (2019), The Ability of GeoCarb to Constrain the Interannual Variability of Carbon Gases over the Amazon, [online] Available from: .
We perform a number of idealized assimilation experiments with the GEOS constituent data assimilation system to test the ability of GeoCarb retrievals of CO, CO2, and CH4 to constrain the interannual variability of these gases over the Amazon.

Worden, H. M., A. A. Bloom, J. R. Worden, Z. Jiang, E. A. Marais, T. Stavrakou, B. Gaubert, and F. Lacey (2019), New constraints on biogenic emissions using satellite-based estimates of carbon monoxide fluxes, Atmos. Chem. Phys., 19(21), 1356913579, doi:10.5194/acp-19-13569-2019.
Biogenic non-methane volatile organic compounds (NMVOCs) emitted from vegetation are a primary source for the chemical production of carbon monoxide (CO) in the atmosphere, and these biogenic emissions account for about 18% of the global CO burden. Partitioning CO fluxes to different source types in top-down inversion methods is challenging; typically a simple scaling of the posterior flux to prior flux values for fossil fuel, biogenic and biomass burning sources is used. Here we show top-down estimates of biogenic CO fluxes using a Bayesian inference approach, which explicitly accounts for both posterior and a priori CO flux uncertainties. This approach re-partitions CO fluxes following inversion of Measurements Of Pollution In The Troposphere (MOPITT) CO observations with the GEOS-Chem model, a global chemical transport model driven by assimilated meteorology from the NASA Goddard Earth Observing System (GEOS). We compare these results to the prior information for CO used to represent biogenic NMVOCs from GEOS-Chem, which uses the Model of Emissions of Gases and Aerosols from Nature (MEGAN) for biogenic emissions. We evaluate the a posteriori biogenic CO fluxes against top-down estimates of isoprene fluxes using Ozone Monitoring Instrument (OMI) formaldehyde observations. We find similar seasonality and spatial consistency in the posterior CO and top-down isoprene estimates globally. For the African savanna region, both top-down CO and isoprene seasonality vary significantly from the MEGAN a priori inventory. This method for estimating biogenic sources of CO will provide an independent constraint on modeled biogenic emissions and has the potential for diagnosing decadal-scale changes in emissions due to land-use change and climate variability.

Yin, S., X. Wang, X. Zhang, Z. Zhang, Y. Xiao, H. Tani, and Z. Sun (2019), Exploring the effects of crop residue burning on local haze pollution in Northeast China using ground and satellite data, Atmospheric Environment, 199, 189201, doi:10.1016/j.atmosenv.2018.11.033.
In this study, we used ground-measured air pollutants and various remote sensing and meteorological datasets to explore the possible causes of the severe particulate matter (PM) pollution episodes of October and November 2015 in Northeast China. The three pollution episodes in different regions were elaborately characterized by analyzing the time variation of PM2.5 and other pollutants, e.g., CO, NO2, and SO2. The results from MODerate-resolution Imaging Spectrometer (MODIS) revealed that during the study period, dramatic crop residue burning occurred in Northeast China. Combining its time variation and spatial distribution with air pollutants, the crop residue burning was inferred to have a direct influence on the first and second pollution episodes, especially in Heilongjiang Province. Since a cold wave swept Northeast China beginning on 4th November, the PM pollutants were assumed to be transported southward. This assumption was further verified by the backward and forward trajectory models. Additionally, the suddenly increased relative humidity beginning on 7th November and the week of no wind after the cold wave also greatly contributed to the most severe pollution of Liaoning and Jilin on approximately 8th November. Lastly, we compared air quality indexes and pollutants from remote sensing with ground-measured datasets; the results indicated that there were certain correlations and spatial consistency between the two types of datasets, except for UVAI, which is meaningful to the area without an effective ground monitoring network.

Yin, S., Wang, X., Zhang, X., Guo, M., Miura, M., and Xiao, Y. (2019), Influence of biomass burning on local air pollution in mainland Southeast Asia from 2001 to 2016, Environmental Pollution, 254. [online] Available from:
In this study, various remote sensing data, modeling data and emission inventories were integrated to analyze the tempo-spatial distribution of biomass burning in mainland Southeast Asia and its effects on the local ambient air quality from 2001 to 2016. Land cover changes have been considered in dividing the biomass burning into four types: forest fires, shrubland fires, crop residue burning and other fires. The results show that the monthly average number of fire spots peaked at 34,512 in March and that the monthly variation followed a seasonal pattern, which was closely related to precipitation and farming activities. The four types of biomass burning fires presented different tempo-spatial distributions. Moreover, the monthly Aerosol Optical Depth (AOD), concentration of particulate matter with a diameter less than 2.5 μm (PM2.5) and carbon monoxide (CO) total column also peaked in March with values of 0.62, 45 μg/m3 and 3.25 × 1018 molecules/cm2, respectively. There are significant correlations between the monthly means of AOD (r = 0.74, P < 0.001), PM2.5 concentration (r = 0.88, P < 0.001), and CO total column (r = 0.82, P < 0.001) and the number of fire spots in the fire season. We used Positive Matrix Factorization (PMF) model to resolve the sources of PM2.5 into 3 factors. The result indicated that the largest contribution (48%) to annual average concentration of PM2.5 was from Factor 1 (dominated by biomass burning), followed by 27% from Factor 3 (dominated by anthropogenic emission), and 25% from Factor 2 (long-range transport/local nature source). The annually anthropogenic emission of CO and PM2.5 from 2001 to 2012 and the monthly emission from the Emission Database for Global Atmosphere Research (EDGAR) were consistent with PMF analysis and further prove that biomass burning is the dominant cause of the variation in the local air quality in mainland Southeast Asia. There are significant correlations between the monthly AOD, PM2.5 concentration, and CO total column and the number of fire spots in the fire season. Biomass burning is the dominant cause of the variation in the local quality in mainland Southeast Asia.

Zeb, N., M. F. Khokhar, A. Pozzer, and S. A. Khan (2019), Exploring the temporal trends and seasonal behaviour of tropospheric trace gases over Pakistan by exploiting satellite observations, Atmos. Environ., 198, 279290, doi:10.1016/j.atmosenv.2018.10.053.
Air pollution has emerged as a key environmental issue of Pakistan as its major cities are ranked among top polluted cities in the South Asian region. Due to lack of adequate ground-based monitoring facilities, satellite observations are the only viable source for long-term assessment of air quality over the region. This study analyses the atmospheric concentrations and decadal changes derived from multiple satellite instruments of four important tropospheric trace gases over Pakistan: surface concentrations of carbon monoxide (CO), tropospheric columns of formaldehyde (HCHO), nitrogen dioxide (NO2) and ozone (O-3). High levels of all these trace gases were observed over Punjab region, which may be attributed to its metropolitan importance. It is the major agricultural, industrialized and urbanized region of the country. Seasonal Mann-Kendall (SMK) test is used to calculate the statistical significance of temporal trend during the last decade (2005-2014). Surface CO showed a significant decrease of about 13 +/- 1% over the decade. Tropospheric column ozone (O-3) exhibited a significant increasing trend with a temporal increase of 10.4 +/- 1.2%/decade whereas NO2 showed a significant temporal increase of about 28 +/- 2%/decade. However, an insignificant increase of about 8.3 +/- 0.3%/decade is estimated for HCHO over the decade. A distinct seasonal behaviour is observed among trace gases. The long-term relationship among trace gases is further explored by statistical tests. It is found that O-3, NO2 and HCHO have a significant impact on the long-term decrease of CO whereas; the trend in O-3 critically depends on NO2 levels along with CO over the region. A statistical model is developed to estimate the long-term association of trace gases over the region. The model indicates that O-3 production may have major influence on decrease of CO over Pakistan in a (volatile organic compound) VOC-limited regime.

Zhang, X., D. B. A. Jones, M. Keller, T. W. Walker, Z. Jiang, D. K. Henze, H. M. Worden, A. E. Bourassa, D. A. Degenstein, and Y. J. Rochon (2019), Quantifying Emissions of CO and NOx Using Observations From MOPITT, OMI, TES, and OSIRIS, Journal of Geophysical Research: Atmospheres, 124(2), 11701193, doi:10.1029/2018JD028670.
We use the GEOS-Chem four-dimensional variational data assimilation system to estimate emissions of carbon monoxide (CO) and nitrogen oxides (NOx) in November 2009 and July 2010. We assimilated CO retrievals from The Measurements of Pollution In The Troposphere (MOPITT), ozone (O3) retrievals from the Tropospheric Emission Spectrometer (TES) and the Optical Spectrograph and InfraRed Imager System (OSIRIS), and NO2 columns from the Ozone Monitoring Instrument (OMI). By assimilating data for multiple chemical species with the four-dimensional variational scheme we obtain a consistent chemical state over the assimilation period. The modeled O3 bias was reduced to less than 3.5 ppbv everywhere, relative to independent aircraft O3 data, except in the high-latitude upper troposphere and lower stratosphere. We found that in November, the CO and NOx emission estimates obtained with the multiple species assimilation were generally comparable to those inferred from assimilating only MOPITT or OMI data, respectively, whereas in July the differences were larger. For the main anthropogenic source regions, the inferred North American and European emissions responded most strongly to the multispecies information in the assimilation. In July, North American and European CO emission estimates differed by 31% and 65% relative to the MOPITT-only estimates, respectively. We also found large differences for the North American and European NOx emission estimates, which differed by 27% and 16% relative to the OMI-only estimates, respectively. Our results highlight the potential benefit of exploiting the additional constraints offered by multispecies chemical data assimilation.

Zheng, B., F. Chevallier, Y. Yin, P. Ciais, A. Fortems-Cheiney, M. N. Deeter, R. J. Parker, Y. Wang, H. M. Worden, and Y. Zhao (2019a), Global atmospheric carbon monoxide budget 2000-2017 inferred from multi-species atmospheric inversions, Earth Syst. Sci. Data, 11(3), 14111436, doi:10.5194/essd-11-1411-2019.
Atmospheric carbon monoxide (CO) concentrations have been decreasing since 2000, as observed by both satellite-and ground-based instruments, but global bottom-up emission inventories estimate increasing anthropogenic CO emissions concurrently. In this study, we use a multi-species atmospheric Bayesian inversion approach to attribute satellite-observed atmospheric CO variations to its sources and sinks in order to achieve a full closure of the global CO budget during 2000-2017. Our observation constraints include satellite retrievals of the total column mole fraction of CO, formaldehyde (HCHO), and methane (CH4) that are all major components of the atmospheric CO cycle. Three inversions (i.e., 2000-2017, 2005-2017, and 2010-2017) are performed to use the observation data to the maximum extent possible as they become available and assess the consistency of inversion results to the assimilation of more trace gas species. We identify a declining trend in the global CO budget since 2000 (three inversions are broadly consistent during overlapping periods), driven by reduced anthropogenic emissions in the US and Europe (both likely from the transport sector), and in China (likely from industry and residential sectors), as well as by reduced biomass burning emissions globally, especially in equatorial Africa (associated with reduced burned areas). We show that the trends and drivers of the inversion-based CO budget are not affected by the inter-annual variation assumed for prior CO fluxes. All three inversions contradict the global bottom-up inventories in the world’s top two emitters: for the sign of anthropogenic emission trends in China (e.g., here 0.8 +/- 0.5% yr(-1) since 2000, while the prior gives 1.3 +/- 0.4% yr(-1)) and for the rate of anthropogenic emission increase in South Asia (e.g., here 1.0 +/- 0.6% yr(-1) since 2000, smaller than 3.5 +/- 0.4% yr(-1) in the prior inventory). The posterior model CO concentrations and trends agree well with independent ground-based observations and correct the prior model bias. The comparison of the three inversions with different observation constraints further suggests that the most complete constrained inversion that assimilates CO, HCHO, and CH4 has a good representation of the global CO budget, and therefore matches best with independent observations, while the inversion only assimilating CO tends to underestimate both the decrease in anthropogenic CO emissions and the increase in the CO chemical production.

Zheng, B., K. M. de Beurs, B. C. Owsley, and G. M. Henebry (2019b), Scaling relationship between CO pollution and population size over major, Landsc. Urban Plan., 187, 191198, doi:10.1016/j.landurbplan.2018.12.009.
As the world’s population is projected to reach 9.7 billion by 2050, large and small cities will continue to expand. There are few studies investigating how the size of cities affects air pollution. Carbon monoxide (CO), a precursor of ozone and a by-product of incomplete combustion, is a common air pollutant. The major sources of CO in the US urban areas are motor vehicles. Here we examined the scaling relation of CO concentrations over major US metropolitan statistical areas (MSAs) using Measurement Of Pollution in The Troposphere (MOPITT) surface CO retrievals and National Emissions Inventory (NEI) data. We found significant power-law scaling relationships between CO and population (r(2) of 0.30 for MOPITT average CO concentration and r(2) of 0.71 for NEI total CO emission). We found decreasing CO trends from 2000 to 2015 using MOPITT and EPA CO ground measurements. Sublinear scaling relationships (scaling coefficient beta < 1) suggest that larger MSAs are more combustion-efficient in terms of CO emissions. We found a weaker scaling relation and smaller scaling coefficient from MOPITT CO concentrations than from NEI total CO emission data. This pattern may be attributed to the differences between the two CO datasets: annual average of monthly MOPITT CO concentration at 1 degrees by 1 degrees spatial resolution versus the NEI annual CO emissions compiled from emission inventories and estimated from mobile source emissions models. Future research is needed to investigate the capability of using satellite observations to study scaling relations between air pollutants and population.

Zoran, M. A., R. S. Savastru, D. M. Savastru, and M.-C. V. Penache (2019), Temporal trends of carbon monoxide (CO) and radon (Rn-222) tracers of urban air pollution, J. Radioanal. Nucl. Chem., 320(1), 5570, doi:10.1007/s10967-019-06443-7.
The use of carbon monoxide (CO) and radon (Rn-222) during 1year continuous monitoring in Bucharest, Romania in relation with other air pollutants (ozoneO(3), nitrogen dioxideNO(2), sulphur dioxideSO(2), airborne particulate matter PM10), air quality indices, meteorological variables and planetary boundary layer heights has provided relevant information about lower atmospheric dynamics. Annual average air daily mean CO (328.72 +/- 100.02 mu g/m(3)) and Rn-222 (38.43 +/- 17.68Bq/m(3)) do not exceed the threshold limits established by European legislation. Statistical analysis of CO and Rn-222 temporal trends revealed their suitability as tracer gases for urban air pollution.


Adame, J. A., L. Lope, P. J. Hidalgo, M. Sorribas, I. Gutierrez-Alvarez, A. del Aguila, A. Saiz-Lopez, and M. Yela (2018), Study of the exceptional meteorological conditions, trace gases and particulate matter measured during the 2017 forest fire in Donana Natural Park, Spain, Sci. Total Environ., 645, 710720, doi:10.1016/j.scitotenv.2018.07.181.
In late June 2017, a forest fire occurred in Donana Natural Park, which is located in southwestern Europe. Many animal and plant species, some of which are threatened, suffered from the impact of this fire, and important ecosystems in the European Union were seriously affected. This forest fire occurred under exceptional weather conditions. The meteorological situation was studied at both the synoptic scale and the local scale using meteorological fields in the ERA-Interim global model from ECMWF (European Centre for Medium Range Weather Forecasts), the WRF (Weather Research and Forecasting) mesoscale model and ground observations collected at El Arenosillo observatory. Anomalies were obtained using records (observations and simulations) over the last two decades (1996-2016). An anticyclonic system dominated the synoptic meteorological conditions, but a strong pressure gradient was present; positive high pressure anomalies and negative low pressure anomalies resulted in intense NW flows. At the surface, wind gusts of 80 km h(-1), temperatures up to 35 degrees C and relative humidity values <20% were observed. In terms of anomalies, these observations corresponded to positive temperature anomalies (differences of 12 degrees C), positive wind speed anomalies (>29 km h(-1)) and negative relative humidity anomalies (differences of 40%). The forest fire reached El Arenosillo observatory approximately 8 h after it began. When the fire started, record-setting maximum values were measured for all gases monitored at this site (specifically, peaks of 99,995 mu g m(-3) for CO, 951 mu g m(-3) for O-3, 478 mu g m(-3) for NO2, 116 mu g m(-3) for SO2 and 1000 mu g m(-3) for PM10). According to the temporal evolution patterns of these species, the atmosphere over a burnt area can recover to initial atmospheric levels between 48 and 96 h after an event. The impact of the Donana plume was studied using hourly forward trajectories computed with the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model to analyse the emission source for the burnt area. The Donana fire plume affected large metropolitan areas near the Mediterranean coast. Air quality stations located in the cities of Seville and Cadiz registered the arrival of the plume based on increases in CO and PM10. Using CO as a tracer, measurements from the AIRS and MOPITT instruments allowed us to observe the transport of the Donana plume from the Strait of Gibraltar to the Mediterranean. Finally, after two days, the Donana forest fire plume reached the western Mediterranean basin. (C) 2018 Published by Elsevier B.V.

Aliyu, Y. A., and J. O. Botai (2018), Appraising city-scale pollution monitoring capabilities of multi-satellite datasets using portable pollutant monitors, Atmospheric Environment, 179, 239249, doi:10.1016/j.atmosenv.2018.02.034.
The retrieval characteristics for a city-scale satellite experiment was explored over a Nigerian city. The study evaluated carbon monoxide and aerosol contents in the city atmosphere. We utilized the MSA Altair 5× gas detector and CW-HAT200 particulate counter to investigate the city-scale monitoring capabilities of satellite pollution observing instruments; atmospheric infrared sounder (AIRS), measurement of pollution in the troposphere (MOPITT), moderate resolution imaging spectroradiometer (MODIS), multi-angle imaging spectroradiometer (MISR) and ozone monitoring instrument (OMI). To achieve this, we employed the Kriging interpolation technique to collocate the satellite pollutant estimations over 19 ground sample sites for the period of 20152016. The portable pollutant devices were validated using the WHO air filter sampling model. To determine the city-scale performance of the satellite datasets, performance indicators: correlation coefficient, model efficiency, reliability index and root mean square error, were adopted as measures. The comparative analysis revealed that MOPITT carbon monoxide (CO) and MODIS aerosol optical depth (AOD) estimates are the appropriate satellite measurements for ground equivalents in Zaria, Nigeria. Our findings were within the acceptable limits of similar studies that utilized reference stations. In conclusion, this study offers direction to Nigeria’s air quality policy organizers about available alternative air pollution measurements for mitigating air quality effects within its limited resource environment.

Aragão, L. E. O. C., L. O. Anderson, M. G. Fonseca, T. M. Rosan, L. B. Vedovato, F. H. Wagner, C. V. J. Silva, C. H. L. S. Junior, E. Arai, A. P. Aguiar, J. Barlow, E. Berenguer, M. N. Deeter, L. G. Domingues, L. Gatti, M. Gloor, Y. Malhi, J. A. Marengo, J. B. Miller, O. L. Phillips, and S. Saatchi (2018), 21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions, Nature Communications, 9(1), 536, doi:10.1038/s41467-017-02771-y.
Deforestation carbon emissions from the Brazilian Amazon have declined steeply, but how much drought-induced forest fire emissions add to this process is still unclear. Here the authors show that gross emissions from forest fires are more than half as great as those from deforestation during drought years.

Borsdorff, T., J. Andrasec, J. aan de Brugh, H. Hu, I. Aben, and J. Landgraf (2018a), Detection of carbon monoxide pollution from cities and wildfires on regional and urban scales: the benefit of CO column retrievals from SCIAMACHY 2.3 mu m measurements under cloudy conditions, Atmos. Meas. Tech., 11(5), 25532565, doi:10.5194/amt-11-2553-2018.
In the perspective of the upcoming TROPOMI Sentinel-5 Precursor carbon monoxide data product, we discuss the benefit of using CO total column retrievals from cloud-contaminated SCIAMACHY 2.3 mu m shortwave infrared spectra to detect atmospheric CO enhancements on regional and urban scales due to emissions from cities and wildfires. The study uses the operational Sentinel-5 Precursor algorithm SICOR, which infers the vertically integrated CO column together with effective cloud parameters. We investigate its capability to detect localized CO enhancements distinguishing between clear-sky observations and observations with low (< 1.5 km) and medium-high clouds (1.5-5 km). As an example, we analyse CO enhancements over the cities Paris, Los Angeles and Tehran as well as the wildfire events in Mexico-Guatemala 2005 and Alaska- Canada 2004. The CO average of the SCIAMACHY full-mission data set of clear-sky observations can detect weak CO enhancements of less than 10 ppb due to air pollution in these cities. For low-cloud conditions, the CO data product performs similarly well. For medium-high clouds, the observations show a reduced CO signal both over Tehran and Los Angeles, while for Paris no significant CO enhancement can be detected. This indicates that information about the vertical distribution of CO can be obtained from the SCIAMACHY measurements. Moreover, for the Mexico-Guatemala fires, the low-cloud CO data captures a strong outflow of CO over the Gulf of Mexico and the Pacific Ocean and so provides complementary information to clear-sky retrievals, which can only be obtained over land. For both burning events, enhanced CO values are even detectable with medium-high-cloud retrievals, confirming a distinct vertical extension of the pollution. The larger number of additional measurements, and hence the better spatial coverage, significantly improve the detection of wildfire pollution using both the clear-sky and cloudy CO retrievals. Due to the improved instrument performance of the TROPOMI instrument with respect to its precursor SCIAMACHY, the upcoming Sentinel-5 Precursor CO data product will allow improved detection of CO emissions and their vertical extension over cities and fires, making new research applications possible.

Borsdorff, T., J. Aan de Brugh, H. Hu, I. Aben, O. Hasekamp, and J. Landgraf (2018b), Measuring Carbon Monoxide With TROPOMI: First Results and a Comparison With ECMWF-IFS Analysis Data, Geophysical Research Letters, 45(6), 28262832, doi:10.1002/2018GL077045.
The Tropospheric Monitoring Instrument (TROPOMI) was launched onboard of the European Space Agency’s (ESA) Sentinel-5P satellite. One of the mission’s key products is the total column density of carbon monoxide, inferred from TROPOMI’s 2.3 μm measurements. Using the operational processing algorithm, we analyze six subsequent days of measurements during the commissioning phase. The TROPOMI product is compared with CO fields from the European Centre for Medium-Range Weather Forecasts (ECMWF) assimilation system. Globally, a small mean difference between the data sets of 3.2 ± 5.5% with a correlation coefficient of 0.97 is found. The daily global coverage of TROPOMI enables it to capture day-to-day evolution of the atmospheric composition. As an example, we discuss the air pollution event of India in November 2017 with high carbon monoxide (CO) concentrations, which partly dispersed when the CO polluted air was transported north alongside the Himalaya to China. The striking agreement and also regional differences with ECMWF indicate new exciting applications for the TROPOMI CO data product.

Buchholz, R. R., D. Hammerling, H. M. Worden, M. N. Deeter, L. K. Emmons, D. P. Edwards, and S. A. Monks (2018), Links Between Carbon Monoxide and Climate Indices for the Southern Hemisphere and Tropical Fire Regions, J. Geophys. Res.-Atmos., 123(17), 97869800, doi:10.1029/2018JD028438.
In the Southern Hemisphere and tropics, the main contribution to carbon monoxide (CO) variability is from fire emissions, which are connected to climate through the availability, type, and dryness of fuel. Here we assess the data-driven relationships between CO and climate, aiming to predict atmospheric loading during fire seasons. Observations of total column CO from the Measurements Of Pollution In The Troposphere satellite instrument are used to build a record of monthly anomalies between 2001 and 2016, focusing on seven biomass burning regions of the Southern Hemisphere and tropics. With the exception of 2015, the range of absolute variability in CO is similar between regions. We model CO anomalies in each of the regions using climate indices for the climate modes: El Nino-Southern Oscillation, Indian Ocean Dipole, Tropical South Atlantic, and Antarctic Oscillation. Stepwise forward and backward variable selection is used to choose from statistical regression models that use combinations of climate indices, at lag times between 1 and 8months relative to CO anomalies. The Bayesian information criterion selects models with the best predictive power. We find that all climate mode indices are required to model CO in each region, generally explaining over 50% of the variability and over 70% for tropical regions. First-order interaction terms of the climate modes are necessary, producing greatly improved explanation of CO variability over single terms. Predictive capability is assessed for the Maritime Southeast Asia and the predicted peak CO anomaly in 2015 is within 20% of the measurements.

Cuesta, J., Y. Kanaya, M. Takigawa, G. Dufour, M. Eremenko, G. Foret, K. Miyazaki, and M. Beekmann (2018), Transboundary ozone pollution across East Asia: daily evolution and photochemical production analysed by IASI + GOME2 multispectral satellite observations and models, Atmospheric Chemistry and Physics, 18(13), 94999525, doi:
We characterise a transboundary ozone pollution outbreak transported across East Asia in early May 2009 using new multispectral satellite observations of lowermost tropospheric ozone (located below 3 km altitude) in synergy with other satellite data and models. Our analysis is focused on the daily evolution of ozone pollution plumes initially formed over the North China Plain (NCP) and their transport pathways over northern China, Korea, Japan and the surrounding seas. A main aspect of the study is an estimation of the contribution of photochemical production of ozone during transport using the ratio of ozone to carbon monoxide enhancements with respect to background levels derived from satellite data and also from chemistrytransport models.  A key contribution of the analysis is the use of new satellite data offering unprecedented skills to observe the horizontal distribution of lowermost tropospheric ozone over East Asia on a daily basis, with a multispectral approach called IASI + GOME2 (combining Infrared Atmospheric Sounding Interferometer observations in the IR and Global Ozone Monitoring Experiment-2 measurements in the UV). These satellite observations are in good agreement with ozonesondes, with low mean biases (3 %), a precision of about 16 %, a correlation coefficient of 0.85 and practically the same standard deviation for a comparison based on 2 years of data from 46 launching stations distributed worldwide, during all seasons. A similar agreement is also found over East Asia. Moreover, IASI + GOME2 offers a unique capacity for observing the evolution of near-surface ozone during pollution outbreaks (with 5 % bias and 0.69 correlation), according to a comparison with surface in situ measurements during two major ozone events over several Japanese islands. Single-band ozone retrievals, such as those from IASI in the thermal infrared, do not capture such variability.  Using IASI + GOME2, we show that (i) ozone pollution plumes are transported by an anticyclonic circulation around the Yellow Sea from the NCP to northern China, Korea and Japan, collocated with carbon monoxide plumes; (ii) over northern China the plume splits into two pollution filaments with one mixing with freshly emitted pollutants; and (iii) ozone is produced every day of the event, accounting for an enhancement in concentration during transport across East Asia of up to  ∼ 84 % with respect to that produced over NCP. This estimation is done according to monotonically increasing values during 7 days of the ratio of ozone to carbon monoxide enhancements within the transported pollution plumes from about  ∼ 0.25 over the NCP to  ∼ 0.46 over the Pacific south of Japan.

Deeter, M. N., S. Martínez‐Alonso, M. O. Andreae, and H. Schlager (2018), Satellite-Based Analysis of CO Seasonal and Interannual Variability Over the Amazon Basin, Journal of Geophysical Research: Atmospheres, 0(0), doi:10.1029/2018JD028425. [online] Available from: .
The “Measurements of Pollution in the Troposphere” (MOPITT) satellite record is applied to study the geographical and temporal variability of carbon monoxide (CO) from biomass burning in the Amazon Basin. The presented analysis demonstrates the use of satellite observations for interpreting the effects of deforestation and climate on past and future emissions of CO. The study exploits the MOPITT “multispectral” retrieval product which effectively resolves tropospheric CO into two independently measured layers. New validation results based on in situ measurements during the ACRIDICON-CHUVA aircraft campaign in 2014 are used for bias correction. Contrasting CO monthly climatologies are presented for the Amazon Basin for the lower and upper troposphere (“LT” and “UT”) with an emphasis on the Amazonian dry season. Climatologically, spatial patterns of UT CO over the Amazon Basin appear to be related to both deep convection and anticyclonic flow. Strongly enhanced LT basin-mean CO concentrations are observed for the dry season months in 2005, 2007, 2010, and 2015, while the record also indicates a decreasing long-term trend. These observations are consistent with the expected effects of falling deforestation rates since 2004, punctuated by CO spikes in drought years due to large-scale wildfires.

Donets, V., E. L. Atlas, L. L. Pan, S. M. Schauffler, S. Honomichl, R. S. Hornbrook, E. C. Apel, T. Campos, S. R. Hall, K. Ullmann, J. F. Bresch, M. Navarro, and D. R. Blake (2018), Wintertime Transport of Reactive Trace Gases From East Asia Into the Deep Tropics, Journal of Geophysical Research: Atmospheres, 123(22), 12,877-12,896, doi:10.1029/2017JD028231.
Unprecedented growth of East Asian economies has led to increases of anthropogenic pollutants in the regional atmosphere. This pollutant burden is transported into the global atmosphere and is a significant source of intercontinental and transboundary anthropogenic pollution. This work analyzes pollution transport into the western Pacific associated with the dispersion of East Asian pollution during Northern Hemisphere winter. To examine transport characteristics, we use chemical and dynamical data sets obtained during the CONvective TRansport of Active Species in the Tropics (CONTRAST) field campaign, conducted from Guam during JanuaryFebruary 2014. We identify that the evolution of shear lines from decaying cold fronts and their southward advancement facilitates polluted air transport into low latitudes of the Western Pacific Ocean. Observations from two cases of shear line passage are analyzed. The result shows that this transport process significantly elevates anthropogenic trace gases in the marine boundary layer and lowermost free troposphere up to 34 km. Results of our analysis show that chemical influence of the shear line on the background tropical marine atmosphere varies as a function of pollution source, intensity, shear line strength, and the speed of advancement, as well as local background conditions. To quantify the contribution of shear-line-related transport, we introduce an index, the Anthropogenic Enhancement Factor (AEF), defined as a fractional change in mixing ratio of a gas brought about by the advancing front. This index shows that the most significant enhancements are for species with photochemical lifetimes comparable to their transport times from source regions.

Edwards, D. P., H. M. Worden, D. Neil, G. Francis, T. Valle, and A. F. Arellano (2018), The CHRONOS mission: capability for sub-hourly synoptic observations of carbon monoxide and methane to quantify emissions and transport of air pollution, Atmos. Meas. Tech., 11(2), 10611085, doi:10.5194/amt-11-1061-2018.
The CHRONOS space mission concept provides time-resolved abundance for emissions and transport studies of the highly variable and highly uncertain air pollutants carbon monoxide and methane, with sub-hourly revisit rate at fine (similar to 4 km) horizontal spatial resolution across a North American domain. CHRONOS can provide complete synoptic air pollution maps (“snapshots”) of the continental domain with less than 10 min of observations. This rapid mapping enables visualization of air pollution transport simultaneously across the entire continent and enables a sentinel-like capability for monitoring evolving, or unanticipated, air pollution sources in multiple locations at the same time with high temporal resolution. CHRONOS uses a compact imaging gas filter correlation radiometer for these observations, with heritage from more than 17 years of scientific data and algorithm advances by the science teams for the Measurements of Pollution in the Troposphere (MOPITT) instrument on NASA’s Terra spacecraft in low Earth orbit. To achieve continental-scale sub-hourly sampling, the CHRONOS mission would be conducted from geostationary orbit, with the instrument hosted on a communications or meteorological platform. CHRONOS observations would contribute to an integrated observing system for atmospheric composition using surface, suborbital and satellite data with atmospheric chemistry models, as defined by the Committee on Earth Observing Satellites. Addressing the U.S. National Academy’s 2007 decadal survey direction to characterize diurnal changes in tropospheric composition, CHRONOS observations would find direct societal applications for air quality management and forecasting to protect public health.

Giuseppe, F. D., S. Rémy, F. Pappenberger, and F. Wetterhall (2018), Using the Fire Weather Index (FWI) to improve the estimation of fire emissions from fire radiative power (FRP) observations, Atmospheric Chemistry and Physics, 18(8), 53595370, doi:

The atmospheric composition analysis and forecast for the European Copernicus Atmosphere Monitoring Services (CAMS) relies on biomass-burning fire emission estimates from the Global Fire Assimilation System (GFAS). The GFAS is a global system and converts fire radiative power (FRP) observations from MODIS satellites into smoke constituents. Missing observations are filled in using persistence, whereby observed FRP values from the previous day are progressed in time until a new observation is recorded. One of the consequences of this assumption is an increase of fire duration, which in turn translates into an increase of emissions estimated from fires compared to what is available from observations. In this study persistence is replaced by modelled predictions using the Canadian Fire Weather Index (FWI), which describes how atmospheric conditions affect the vegetation moisture content and ultimately fire duration. The skill in predicting emissions from biomass burning is improved with the new technique, which indicates that using an FWI-based model to infer emissions from FRP is better than persistence when observations are not available.

Jiang, Z., B. C. McDonald, H. Worden, J. R. Worden, K. Miyazaki, Z. Qu, D. K. Henze, D. B. A. Jones, A. F. Arellano, E. V. Fischer, L. Zhu, and K. F. Boersma (2018), Unexpected slowdown of US pollutant emission reduction in the past decade, PNAS, 201801191, doi:10.1073/pnas.1801191115.
Ground and satellite observations show that air pollution regulations in the United States (US) have resulted in substantial reductions in emissions and corresponding improvements in air quality over the last several decades. However, large uncertainties remain in evaluating how recent regulations affect different emission sectors and pollutant trends. Here we show a significant slowdown in decreasing US emissions of nitrogen oxides (NOx) and carbon monoxide (CO) for 20112015 using satellite and surface measurements. This observed slowdown in emission reductions is significantly different from the trend expected using US Environmental Protection Agency (EPA) bottom-up inventories and impedes compliance with local and federal agency air-quality goals. We find that the difference between observations and EPA’s NOx emission estimates could be explained by: (i) growing relative contributions of industrial, area, and off-road sources, (ii) decreasing relative contributions of on-road gasoline, and (iii) slower than expected decreases in on-road diesel emissions.

Kumar, R., M. C. Barth, G. G. Pfister, L. D. Monache, J. F. Lamarque, S. Archer‐Nicholls, S. Tilmes, S. D. Ghude, C. Wiedinmyer, M. Naja, and S. Walters (2018), How Will Air Quality Change in South Asia by 2050?, Journal of Geophysical Research: Atmospheres, 123(3), 18401864, doi:10.1002/2017JD027357.
Exposure to unhealthy air causes millions of premature deaths and damages crops sufficient to feed a large portion of the South Asian population every year. However, little is known about how future air quality in South Asia will respond to changing human activities. Here we examine the combined effect of changes in climate and air pollutant emissions projected by the Representative Concentration Pathways (RCP) 8.5 and RCP6.0 on air quality of South Asia in 2050 using a state-of-the-science Nested Regional Climate model with Chemistry (NRCM-Chem). RCP8.5 and RCP6.0 are selected to represent scenarios of highest and lowest air pollution in South Asia by 2050. NRCM-Chem shows the ability to capture observed key features of variability in meteorological parameters, ozone and related gases, and aerosols. NRCM-Chem results show that surface ozone and particulate matter of less than 2.5 μm in diameter will increase significantly by midcentury in South Asia under the RCP8.5 but remain similar to present day under RCP6.0. No RCP suggest an improvement in air pollution in South Asia by midcentury. Under RCP8.5, the frequency of air pollution events is predicted to increase by 20120 days per year in 2050 compared to the present-day conditions, with particulate matter of less than 2.5 μm in diameter predicted to breach the World Health Organization ambient air quality guidelines on an almost daily basis in many parts of South Asia. These results indicate that while the RCP scenarios project a global improvement in air quality, they generally result in degrading air quality in South Asia.

Kumari, S., N. Verma, A. Lakhani, S. Tiwari, and M. K. Kandikonda (2018), Tropospheric ozone enhancement during post-harvest crop-residue fires at two downwind sites of the Indo-Gangetic Plain, Environ. Sci. Pollut. Res., 25(19), 1887918893, doi:10.1007/s11356-018-2034-y.
In the present study, surface ozone (O-3), nitrogen oxides (NOx), and carbon monoxide (CO) levels were measured at two sites downwind of fire active region in the Indo-Gangetic Plain (IGP): Agra (27.16 degrees N, 78.08 degrees E) and Delhi (28.37 degrees N, 77.12 degrees E) to study the impact of post-harvest crop-residue fires. The study period was classified into two groups: Pre-harvest period and Post-harvest period. During the post-harvest period, an enhancement of 17.3 and 31.7 ppb in hourly averaged O-3 mixing ratios was observed at Agra and Delhi, respectively, under similar meteorological conditions. The rate of change of O-3 was also higher in the post-harvest period by 56.2% in Agra and 39.5% in Delhi. Relatively higher O-3 episodic days were observed in the post-harvest period. Fire hotspots detected by Moderate Resolution Imaging Spectroradiometer (MODIS) along with backward air-mass trajectory analysis suggested that the enhanced O-3 and CO levels at the study sites during the post-harvest period could be attributed to crop-residue burning over the North-West IGP (NW-IGP). Satellite observations of surface CO mixing ratios and tropospheric formaldehyde (HCHO) column also showed higher levels during the post-harvest period.

Lalitaporn, P. (2018), Long-term assessment of carbon monoxide using MOPITT satellite and surface data over Thailand, 1, 45(2), 132139.
Lin, Chuyong and Cohen, Jason (2018), A DECADAL ANALYSIS AND SENSITIVITY STUDY USING MOPITT CO COLUMNS OVER ASIA., International Archives of the Photogrammetry, Remote Sensing & Spatial Information Sciences, 42(3/W5), 5359.
Biomass burning and urbanization are both significant sources of CO emissions and atmospheric loadings in the real environment. The sources of CO are due to incomplete combustion, on one hand of biomass from agriculture or forest clearing, and on the other hand from coal, oil, gas, and other similar materials. However, the spatial and temporal underlying properties and patterns are quite different between these two types of source regions, with urban regions having a relatively constant source of CO emissions, with only short term concentration fluctuations due to local meteorology. On the other hand, in biomass burning regions, the emissions themselves tend to be highly concentrated over a short burning period, and very low otherwise. We hence present a new technique to classify and quantify biomass burning regions and urban regions based on an objective analysis of the CO total column measurements from the MOPITT satellite. By using all of the data from2000-2016, in connection with averages and standard deviation cutoffs, we successfully determine these regions. By performing a sensitivity analysis, in connection with additional ground-based measurements, we determine that the ideal cutoffs for the mean column loading and standard deviation of the column loading 28×1017 mol/cm2 and 6×1017 mol/cm2 respectively. These results are capable of representing known urban regions and biomass burning regions well throughout China, Southeast Asia, and South Asia, specifically including Beijing, Hebei, Shandong, Jiangsu, Anhui, Hunan, Guangdong, and Bangkok on one hand, and Northeastern India, Myanmar, Laos, Northern Thailand, and Vietnam on the other hand. A detailed analysis of the time series over the different classified regions show that while the urban areas have a much higher annual value, and a relatively long peak time, that their maximum is never as high as the peaks in the biomass burning regions, and that these peaks in the biomass burning regions are extremely short in duration, although they occur annually or bi-annually. Finally, we have not been able to obtain a statistically relevant decreasing trend, as others have found, making CO possibly an interesting species for future studies.

Liu, L., Q. Zhuang, Q. Zhu, S. Liu, H. van Asperen, and M. Pihlatie (2018), Global soil consumption of atmospheric carbon monoxide: an analysis using a process-based biogeochemistry model, Atmospheric Chemistry and Physics, 18(11), 79137931, doi:
Carbon monoxide (CO) plays an important role in controlling the oxidizing capacity of the atmosphere by reacting with OH radicals that affect atmospheric methane (CH4) dynamics. We develop a process-based biogeochemistry model to quantify the CO exchange between soils and the atmosphere with a 5 min internal time step at the global scale. The model is parameterized using the CO flux data from the field and laboratory experiments for 11 representative ecosystem types. The model is then extrapolated to global terrestrial ecosystems using monthly climate forcing data. Global soil gross consumption, gross production, and net flux of the atmospheric CO are estimated to be from −197 to −180, 34 to 36, and −163 to −145 Tg CO yr−1 (1 Tg = 1012 g), respectively, when the model is driven with satellite-based atmospheric CO concentration data during 20002013. Tropical evergreen forest, savanna and deciduous forest areas are the largest sinks at 123 Tg CO yr−1. The soil CO gross consumption is sensitive to air temperature and atmospheric CO concentration, while the gross production is sensitive to soil organic carbon (SOC) stock and air temperature. By assuming that the spatially distributed atmospheric CO concentrations (∼ 128 ppbv) are not changing over time, the global mean CO net deposition velocity is estimated to be 0.160.19 mm s−1 during the 20th century. Under the future climate scenarios, the CO deposition velocity will increase at a rate of 0.00020.0013 mm s−1 yr−1 during 20142100, reaching 0.200.30 mm s−1 by the end of the 21st century, primarily due to the increasing temperature. Areas near the Equator, the eastern US, Europe and eastern Asia will be the largest sinks due to optimum soil moisture and high temperature. The annual global soil net flux of atmospheric CO is primarily controlled by air temperature, soil temperature, SOC and atmospheric CO concentrations, while its monthly variation is mainly determined by air temperature, precipitation, soil temperature and soil moisture.

Mead, M. I., S. Castruccio, M. T. Latif, M. S. M. Nadzir, D. Dominick, A. Thota, and P. Crippa (2018), Impact of the 2015 wildfires on Malaysian air quality and exposure: a comparative study of observed and modeled data, Environ. Res. Lett., 13(4), 044023, doi:10.1088/1748-9326/aab325.
In September and October 2015, Equatorial Asia experienced the most intense biomass burning episodes over the past two decades. These events, mostly enhanced by the extremely dry weather associated with the occurrence of strong El Niño conditions, resulted in the transnational transport of hazardous pollutants from the originating sources in Indonesian Borneo and Sumatra to the highly populated Malaysian Peninsula. Quantifying the population exposure form this event is a major challenge, and only two model-based studies have been performed to date, with limited evaluation against measurements. This manuscript presents a new data set of 49 monitoring stations across Peninsular Malaysia and Malaysian Borneo active during the 2015 haze event, and performs the first comparative study of PM10 (particulate matter with diameter < 10 µm) and carbon monoxide (CO) against the output of a state-of-the-art regional model (WRF-Chem). WRF-Chem presents high skills in describing the spatio-temporal patterns of both PM10 and CO and thus was applied to estimate the impact of the 2015 wildfires on population exposure. This study showed that more than 60% of the population living in the highly populated region of the Greater Klang Valley was systematically exposed to unhealthy/hazardous air quality conditions associated with the increased pollutant concentrations from wildfires and that almost 40% of the Malaysian population was on average exposed to PM10 concentrations higher than 100 µg m−3 during September and October 2015.

Mizzi, Arthur P., Edwards D. P., and Anderson J. L. (2018), Assimilating compact phase space retrievals (CPSRs): comparison with independent observations (MOZAIC in situ and IASI retrievals) and extension to assimilation of truncated retrieval profiles., Geoscientific Model Development, 11(9), p3727-3745.
Assimilation of atmospheric composition retrievals presents computational challenges due to their high data volume and often sparse information density. Assimilation of compact phase space retrievals (CPSRs) meets those challenges and offers a promising alternative to assimilation of raw retrievals at reduced computational cost (Mizzi et al., 2016). This paper compares analysis and forecast results from assimilation of Terra/Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) CPSRs with independent observations. We use MetOp-A/Infrared Atmospheric Sounding Interferometer (IASI) CO retrievals and Measurement of OZone, water vapor, carbon monoxide, and nitrogen oxides by in-service AIrbus airCraft (MOZAIC) in situ CO profiles for our independent observation comparisons. Generally, the results confirm that assimilation of MOPITT CPSRs improves the Weather Research and Forecasting model with chemistry coupled to the ensemble Kalman filter data assimilation from the Data Assimilation Research Testbed (WRF-Chem/DART) analysis fit and forecast skill at a reduced computational cost compared to assimilation of raw retrievals. Comparison with the independent observations shows that assimilation of MOPITT CO generally improved the analysis fit and forecast skill in the lower troposphere but degraded it in the upper troposphere. We attribute that degradation to assimilation of MOPITT CO retrievals with a possible bias of ~ 14% above 300 hPa. To discard the biased retrievals, in this paper, we also extend CPSRs to assimilation of truncated retrieval profiles (as opposed to assimilation of full retrieval profiles). Those results show that not assimilating the biased retrievals (i) resolves the upper tropospheric analysis fit degradation issue and (ii) reduces the impact of assimilating the remaining unbiased retrievals because the total information content and vertical sensitivities are changed.

Muller, J.-F., T. Stavrakou, M. Bauwens, M. George, D. Hurtmans, P.-F. Coheur, C. Clerbaux, and C. Sweeney (2018), Top-Down CO Emissions Based On IASI Observations and Hemispheric Constraints on OH Levels, Geophys. Res. Lett., 45(3), 16211629, doi:10.1002/2017GL076697.
Assessments of carbon monoxide emissions through inverse modeling are dependent on the modeled abundance of the hydroxyl radical (OH) which controls both the primary sink of CO and its photochemical source through hydrocarbon oxidation. However, most chemistry transport models (CTMs) fall short of reproducing constraints on hemispherically averaged OH levels derived from methylchloroform (MCF) observations. Here we construct five different OH fields compatible with MCF-based analyses, and we prescribe those fields in a global CTM to infer CO fluxes based on Infrared Atmospheric Sounding Interferometer (IASI) CO columns. Each OH field leads to a different set of optimized emissions. Comparisons with independent data (surface, ground-based remotely sensed, aircraft) indicate that the inversion adopting the lowest average OH level in the Northern Hemisphere (7.8 x 10(5) molec cm(-3), approximate to 18% lower than the best estimate based on MCF measurements) provides the best overall agreement with all tested observation data sets.

Nechita-Banda, N., M. Krol, G. R. van der Werf, J. W. Kaiser, S. Pandey, V. Huijnen, C. Clerbaux, P. Coheur, M. N. Deeter, and T. Rockmann (2018), Monitoring emissions from the 2015 Indonesian fires using CO satellite data, Philos. Trans. R. Soc. B-Biol. Sci., 373(1760), 20170307, doi:10.1098/rstb.2017.0307.
Southeast Asia, in particular Indonesia, has periodically struggled with intense fire events. These events convert substantial amounts of carbon stored as peat to atmospheric carbon dioxide (CO2) and significantly affect atmospheric composition on a regional to global scale. During the recent 2015 El Nino event, peat fires led to strong enhancements of carbon monoxide (CO), an air pollutant and well-known tracer for biomass burning. These enhancements were clearly observed from space by the Infrared Atmospheric Sounding Interferometer (IASI) and the Measurements of Pollution in the Troposphere (MOPITT) instruments. We use these satellite observations to estimate CO fire emissions within an inverse modelling framework. We find that the derived CO emissions for each sub-region of Indonesia and Papua are substantially different from emission inventories, highlighting uncertainties in bottom-up estimates. CO fire emissions based on either MOPITT or IASI have a similar spatial pattern and evolution in time, and a 10% uncertainty based on a set of sensitivity tests we performed. Thus, CO satellite data have a high potential to complement existing operational fire emission estimates based on satellite observations of fire counts, fire radiative power and burned area, in better constraining fire occurrence and the associated conversion of peat carbon to atmospheric CO2. A total carbon release to the atmosphere of 0.35-0.60 Pg C can be estimated based on our results. This article is part of a discussion meeting issue “The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications”.

Palve, S. N., P. D. Nemade, and S. D. Ghude (2018), MOPITT carbon monoxide its source distributions, interannual variability and transport pathways over India during 2005-2015, Int. J. Remote Sens., 39(18), 59525964, doi:10.1080/01431161.2018.1452076.
Rapid industrial and economic development over the past two decades in India leads the high levels of air pollution. Carbon monoxide (CO) is one of the main pollutants, is not only harmful for human beings but also for its impact on climate. The major CO sources in India are biomass burning and vehicular emissions. Here we used Measurement of Pollution in the Troposphere (MOPITT) CO data from 2005-2015 to examine CO sources, interannual variability, and transport pathways over India. We observed that during the winter months CO emissions over eastern part of Bihar, west Bengal and Northern Indo Gangetic (IG) plain are much higher than during the summer months. The increased vehicular emissions and industrial activity after 2010 resulted in increased CO in the same regions. CO mixing ratios at 350 hPa lowered at 68-90 mu g m(-3) over Arabian Sea and approximately 90 mu g m(-3) over Bay of Bengal during Indian summer monsoon. Deep convective activities transported maximum CO pollutants up to 200 mu g m(-3) over northern and eastern part of India during monsoon season.

Rajab, J. M., I. S. Abdulfattah, and H. A. Mossa (2018), A Comparison of Satellite Carbon Monoxide Measurements from MOPITT and AIRS over Iraq during the Winter and Spring of 2012, Indian Journal of Public Health Research & Development, 9(12), 742, doi:10.5958/0976-5506.2018.01932.0.
Sahu, L. K., N. Tripathi, V. Sheel, M. Kajino, M. Deushi, R. Yadav, and P. Nedelec (2018), Impact of the tropical cyclone Nilam on the vertical distribution of carbon monoxide over Chennai on the Indian peninsula, Quarterly Journal of the Royal Meteorological Society, 144(713), 10911105, doi:10.1002/qj.3276.
The present study investigates the impact of tropical cyclone (TC) Nilam on the vertical distribution of carbon monoxide (CO) over Chennai in southern India. Measurements of OZone and water vapour by Airbus In-service airCraft (MOZAIC) profiles of CO measured during OctoberNovember 2012 were analysed. The vertical profiles of CO on 15 October and 2 November were influenced by convective motions with a significant decrease in outgoing long-wave radiation (OLR) compared to that on normal days of observations. The near-surface mixing ratios of CO (185 ± 24 ppbv) in convectively influenced conditions were much lower than those measured during normal days (>210 ppbv). The occurrence of minimum CO values at altitudes of 46 km coincided with the lowest lapse rate (LR) value of 45 °C/km. The uplift of surface air masses led to a large increase in the CO mixing ratio in the free troposphere. The differences in CO between the lower and free troposphere were relatively small (4050 ppbv) and large (90100 ppbv) during convective and normal days, respectively. In the lower troposphere, elevated values of CO (>250 ppbv) were measured for lighter wind speeds from the north, while lower values (<150 ppbv) were measured for strong winds from the western sectors. The Model for OZone And Related chemical Tracers (MOZART-4) and Chemistry Climate Model 2 (CCM2) simulations did not capture the detailed features of the CO profiles. For cyclone-influenced measurements in the lower troposphere, MOZART-4 underestimated the CO values by approximately 13%, but CCM2 overestimated the CO values by 70%. In the upper troposphere, MOZART-4 and CCM2 underestimated the observations by 68% and 1222%, respectively. The mixing scheme of the model and simulated concentrations seem to be the key causes of disagreements. However, the performances of both the MOZART-4 and CCM2 simulations were better for convection-free normal days.

Strode, S. A., J. Liu, L. Lait, R. Commane, B. Daube, S. Wofsy, A. Conaty, P. Newman, and M. Prather (2018), Forecasting carbon monoxide on a global scale for the ATom-1 aircraft mission: insights from airborne and satellite observations and modeling, Atmospheric Chemistry and Physics, 18(15), 1095510971, doi:

Abstract. The first phase of the Atmospheric Tomography Mission (ATom-1) took place in JulyAugust 2016 and included flights above the remote Pacific and Atlantic oceans. Sampling of atmospheric constituents during these flights is designed to provide new insights into the chemical reactivity and processes of the remote atmosphere and how these processes are affected by anthropogenic emissions. Model simulations provide a valuable tool for interpreting these measurements and understanding the origin of the observed trace gases and aerosols, so it is important to quantify model performance. Goddard Earth Observing System Model version 5 (GEOS-5) forecasts and analyses show considerable skill in predicting and simulating the CO distribution and the timing of CO enhancements observed during the ATom-1 aircraft mission. We use GEOS-5’s tagged tracers for CO to assess the contribution of different emission sources to the regions sampled by ATom-1 to elucidate the dominant anthropogenic influences on different parts of the remote atmosphere. We find a dominant contribution from non-biomass-burning sources along the ATom transects except over the tropical Atlantic, where African biomass burning makes a large contribution to the CO concentration. One of the goals of ATom is to provide a chemical climatology over the oceans, so it is important to consider whether August 2016 was representative of typical boreal summer conditions. Using satellite observations of 700hPa and column CO from the Measurement of Pollution in the Troposphere (MOPITT) instrument, 215hPaCO from the Microwave Limb Sounder (MLS), and aerosol optical thickness from the Moderate Resolution Imaging Spectroradiometer (MODIS), we find that CO concentrations and aerosol optical thickness in August 2016 were within the observed range of the satellite observations but below the decadal median for many of the regions sampled. This suggests that the ATom-1 measurements may represent relatively clean but not exceptional conditions for lower-tropospheric CO.

Tang, W., A. F. Arellano, J. P. DiGangi, Y. Choi, G. S. Diskin, A. Agustí-Panareda, M. Parrington, S. Massart, B. Gaubert, Y. Lee, D. Kim, J. Jung, J. Hong, J.-W. Hong, Y. Kanaya, M. Lee, R. M. Stauffer, A. M. Thompson, J. H. Flynn, and J.-H. Woo (2018), Evaluating high-resolution forecasts of atmospheric CO and CO2 from a global prediction system during KORUS-AQ field campaign, Atmospheric Chemistry and Physics, 18(15), 1100711030, doi:

Abstract. Accurate and consistent monitoring of anthropogenic combustion is imperative because of its significant health and environmental impacts, especially at city-to-regional scale. Here, we assess the performance of the Copernicus Atmosphere Monitoring Service (CAMS) global prediction system using measurements from aircraft, ground sites, and ships during the Korea-United States Air Quality (KORUS-AQ) field study in May to June 2016. Our evaluation focuses on CAMS CO and CO2 analyses as well as two higher-resolution forecasts (16 and 9&thinsp;km horizontal resolution) to assess their capability in predicting combustion signatures over east Asia. Our results show a slight overestimation of CAMS CO2 with a mean bias against airborne CO2 measurements of 2.2, 0.7, and 0.3&thinsp;ppmv for 16 and 9&thinsp;km CO2 forecasts, and analyses, respectively. The positive CO2 mean bias in the 16&thinsp;km forecast appears to be consistent across the vertical profile of the measurements. In contrast, we find a moderate underestimation of CAMS CO with an overall bias against airborne CO measurements of 19.2 (16&thinsp;km), 16.7 (9&thinsp;km), and 20.7&thinsp;ppbv (analysis). This negative CO mean bias is mostly seen below 750&thinsp;hPa for all three forecast/analysis configurations. Despite these biases, CAMS shows a remarkable agreement with observed enhancement ratios of CO with CO2 over the Seoul metropolitan area and over the West (Yellow) Sea, where east Asian outflows were sampled during the study period. More efficient combustion is observed over Seoul (dCO/dCO2=9&thinsp;ppbv&thinsp;ppmv−1) compared to the West Sea (dCO/dCO2=28&thinsp;ppbv&thinsp;ppmv−1). This “combustion signature contrast” is consistent with previous studies in these two regions. CAMS captured this difference in enhancement ratios (Seoul: 812&thinsp;ppbv&thinsp;ppmv−1, the West Sea: ∼30&thinsp;ppbv&thinsp;ppmv−1) regardless of forecast/analysis configurations. The correlation of CAMS CO bias with CO2 bias is relatively high over these two regions (Seoul: 0.640.90, the West Sea: ∼0.80) suggesting that the contrast captured by CAMS may be dominated by anthropogenic emission ratios used in CAMS. However, CAMS shows poorer performance in terms of capturing local-to-urban CO and CO2 variability. Along with measurements at ground sites over the Korean Peninsula, CAMS produces too high CO and CO2 concentrations at the surface with steeper vertical gradients (∼0.4&thinsp;ppmv&thinsp;hPa−1 for CO2 and 3.5&thinsp;ppbv&thinsp;hPa−1 for CO) in the morning samples than observed (∼0.25&thinsp;ppmv&thinsp;hPa−1 for CO2 and 1.7&thinsp;ppbv&thinsp;hPa−1 for CO), suggesting weaker boundary layer mixing in the model. Lastly, we find that the combination of CO analyses (i.e., improved initial condition) and use of finer resolution (9&thinsp;km vs. 16&thinsp;km) generally produces better forecasts.

Wang, P., N. F. Elansky, Y. M. Timofeev, G. Wang, G. S. Golitsyn, M. V. Makarova, V. S. Rakitin, Y. Shtabkin, A. I. Skorokhod, E. I. Grechko, E. V. Fokeeva, A. N. Safronov, L. Ran, and T. Wang (2018a), Long-Term Trends of Carbon Monoxide Total Columnar Amount in Urban Areas and Background Regions: Ground- and Satellite-based Spectroscopic Measurements, Adv. Atmos. Sci., 35(7), 785795, doi:10.1007/s00376-017-6327-8.
A comparative study was carried out to explore carbon monoxide total columnar amount (CO TC) in background and polluted atmosphere, including the stations of ZSS (Zvenigorod), ZOTTO (Central Siberia), Peterhof, Beijing, and Moscow, during 1998-2014, on the basis of ground- and satellite-based spectroscopic measurements. Interannual variations of CO TC in different regions of Eurasia were obtained from ground-based spectroscopic observations, combined with satellite data from the sensors MOPITT (2001-14), AIRS (2003-14), and IASI MetOp-A (2010-13). A decreasing trend in CO TC (1998-2014) was found at the urban site of Beijing, where CO TC decreased by 1.14%+/- 0.87% yr(-1). Meanwhile, at the Moscow site, CO TC decreased remarkably by 3.73%+/- 0.39% yr(-1). In the background regions (ZSS, ZOTTO, Peterhof), the reduction was 0.9%-1.7% yr(-1) during the same period. Based on the AIRSv6 satellite data for the period 2003-14, a slight decrease (0.4%-0.6% yr(-1)) of CO TC was detected over the midlatitudes of Eurasia, while a reduction of 0.9%-1.2% yr(-1) was found in Southeast Asia. The degree of correlation between the CO TC derived from satellite products (MOPITTv6 Joint, AIRSv6 and IASI MetOp-A) and ground-based measurements was calculated, revealing significant correlation in unpolluted regions. While in polluted areas, IASI MetOp-A and AIRSv6 data underestimated CO TC by a factor of 1.5-2.8. On average, the correlation coefficient between ground- and satellite-based data increased significantly for cases with PBL heights greater than 500 m.

Wang, S.-C., Y. Wang, M. Estes, R. Lei, R. Talbot, L. Zhu, and P. Hou (2018b), Transport of Central American Fire Emissions to the U.S. Gulf Coast: Climatological Pathways and Impacts on Ozone and PM2.5, Journal of Geophysical Research: Atmospheres, 123(15), 83448361, doi:10.1029/2018JD028684.
Fire emissions from Mexico and Central America are transported regularly to the U.S. Gulf Coast every spring under prevailing circulation patterns and affect U.S. air quality. Here we use a GEOS-Chem passive tracer simulation to develop the climatology of transport pathways of fire emissions over a long-term time period of April and May 20022015 and estimate their adverse air quality effects for urban areas along the Gulf Coast. A conceptual model is presented to describe the transport mechanisms, which involve southerly low-level jets in the lower troposphere and warm conveyor belt in the middle troposphere. The warm conveyor belts and the southerly low-level jets explain 31% and 69% of the interannual variability of the mid-altitude (1.56 km) and low-altitude events (01.5 km), respectively. Considering both transport and fire emissions, approximately 9% of the study period (5988 days of 854 days) were identified as large pollution events during which Central American fire emissions adversely impacted surface air quality at several major urban centers along the Gulf Coast, including Houston and Corpus Christi in TX, New Orleans in LA, Mobile in AL, and Pensacola in FL. Compared to clean maritime flow from the Gulf of Mexico, these events were estimated to result in average enhancements of maximum daily average 8-hr (MDA8) ozone and daily PM2.5 (fine particulate matter <2.5 μm in diameter) in the Gulf Coast cities of 312 ppbv and 25 μg/m3, respectively. Only one ozone exceedance day (79 ppbv, on 18 May 2003) was found among the fire-impact days for the Houston region.

Wang, Y., C. Yu, J. Tao, Z. Wang, Y. Si, L. Cheng, H. Wang, S. Zhu, and L. Chen (2018c), Spatio-Temporal Characteristics of Tropospheric Ozone and Its Precursors in Guangxi, South China, Atmosphere, 9(9), 355, doi:10.3390/atmos9090355.
The temporal and spatial distributions of tropospheric ozone and its precursors (NO2, CO, HCHO) are analyzed over Guangxi (GX) in South China. We used tropospheric column ozone (TCO) from the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) onboard the Aura satellite (OMI/MLS), NO2 and HCHO from OMI and CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument in the period 2005-2016. The TCO shows strong seasonality, with the highest value in spring and the lowest value observed in the monsoon season. The seasonal variation of HCHO is similar to that of TCO, while NO2 and CO show slightly different patterns with higher values in spring and winter compared to lower values in autumn and summer. The surface ozone, NO2 and CO observed by national air quality monitoring network sites are also compared with satellite-observed TCO, NO2 and CO, showing good agreement for NO2 and CO but a different seasonal pattern for ozone. Unlike TCO, surface ozone has the highest value in autumn and the lowest value in winter. To reveal the difference, the vertical profiles of ozone and CO from the measurement of ozone and water vapor by airbus in-service aircraft (MOZAIC) observations over South China are also examined. The seasonal averaged vertical profiles of ozone and CO show obvious enhancements at 2-6 km altitudes in spring. Furthermore, we investigate the dependence of TCO and surface ozone on meteorology and transport in detail along with the ECMWF reanalysis data, Tropical Rainfall Measuring Mission (TRMM) 3BV42 dataset, OMI ultraviolet index (UV index) dataset, MODIS Fire Radiative Power (FRP) and back trajectory. Our results show that the wind pattern at 800 hPa plays a significant role in determining the seasonality of TCO over GX, especially for the highest value in spring. Trajectory analysis, combined with MODIS FRP suggests that the air masses that passed through the biomass burning (BB) region of Southeast Asia (SEA) induced the enhancement of TCO and CO in the upper-middle troposphere in spring. However, the seasonal cycle of surface ozone is associated with wind patterns at 950 hPa, and the contribution of the photochemical effect is offset by the strong summer monsoon, which results in the maximum surface ozone concentration in post-monsoon September. The variations in the meteorological conditions at different levels and the influence of transport from SEA can account for the vertical distribution of ozone and CO. We conclude that the seasonal distribution of TCO results from the combined impact of meteorology and long-term transport.

Xu, Xing-Wei, Wang, Wei, Liu, Cheng, Shan, Chang-gong, Sun, You-wen, Hu, Qi-hou, Tian, Yuan, Han, Xue-bing, and Yang, Wei (2018), Observations of Total Columns of CO Based on Solar Absorption Spectra, Spectroscopy and Spectral Analysis, 38(5), doi:Doi:10.3964/j.issn.1000-0593(2018)05-1329-06. [online] Available from:
Observations of the total columns of carbon monoxide(CO) in Hefei area are performed based on ground-based high resolution Fourier transform infrared spectroscopy, and we continuously collect the near-infrared solar absorption spectra and obtain time series of total column of CO through the atmosphere from September 2015 to July 2016. The observation results show that the column-averaged dry air mole fraction XCO in this area has obvious seasonal variation during the measurement period. Observation result shows that in the measured period XCO in Hefei area has obvious seasonal change. In October 2015 it has a smaller value, and then it gradually increases, in March 2016 it reaches the maximum at the end of July. Then it declines gradually, and gets to the minimum. We also analyze the reason of the XCO seasonal variation. In order to verify the observations based on the near-infrared region, we use MOPITT satellite data and CO total columns retrieved from the mid-infrared spectra collected by the same spectrometer at Hefei site to compare with the simultaneous measurements. The comparison results show that the seasonal variation of MOPITT data is similar to that of ground-based near-infrared observations, and overall MOPITT observations are higher than ground-based FTS observations. The seasonal variation and variation range of column values of CO retrieved from the mid-infrared spectra agree with those from the near-infrared spectra. The correlation coefficients between the daily averaged CO total columns of the ground-based near-infrared observations with those of satellite and mid-infrared observations are 0.85 and 0.91, respectively, which shows the high correlation and proves the accuracy of the CO total columns of the ground-based near-infrared observations. It is the first time to observe the total columns of carbon monoxide(CO) in Hefei area by using ground-based high resolution Fourier transform infrared spectroscopy, and compare them with MOPITT satellite data to get precise result. It provides the theoretical basis to understand the time and space distribution and changes of CO in atmospheric and trace source-sink distribution of CO in Hefei area.

Zheng, B., F. Chevallier, P. Ciais, Y. Yin, and Y. Wang (2018a), On the Role of the Flaming to Smoldering Transition in the Seasonal Cycle of African Fire Emissions, Geophysical Research Letters, 45(21), doi:10.1029/2018GL079092. [online] Available from: .
Satellite estimates of burned area, associated carbon monoxide (CO) emission estimates, and CO column retrievals do not agree on the peak fire month in Africa, evident in both Northern and Southern Africa though distinct in the burning seasonality. Here we analyze this long-standing problem using (1) a top-down Bayesian inversion of Measurements Of Pollution In The Troposphere CO columns during 20052016 into surface CO emissions and (2) the bottom-up Global Fire Emissions Database 4.1 s. We show that Global Fire Emissions Database 4.1 s underestimates CO emissions by 1262% in the late fire season and hypothesize that this is partly because it assumes seasonally static emission factors. However, the degree to which emission factors would have to vary through the season to bring top-down and bottom-up in agreement cannot be confirmed by past field-based measurements. Improved observational constraint on the seasonality of burned area, fuel combustion, and emission factors would further reduce the discrepancy between bottom-up and top-down emission estimates.

Zheng, B., F. Chevallier, P. Ciais, Y. Yin, M. N. Deeter, H. M. Worden, Y. Wang, Qiang Zhang, and K. He (2018b), Rapid decline in carbon monoxide emissions and export from East Asia between years 2005 and 2016, Environ. Res. Lett., 13(4), 044007, doi:10.1088/1748-9326/aab2b3.
Measurements of Pollution in the Troposphere (MOPITT) satellite and ground-based carbon monoxide (CO) measurements both suggest a widespread downward trend in CO concentrations over East Asia during the period 20052016. This negative trend is inconsistent with global bottom-up inventories of CO emissions, which show a small increase or stable emissions in this region. We try to reconcile the observed CO trend with emission inventories using an atmospheric inversion of the MOPITT CO data that estimates emissions from primary sources, secondary production, and chemical sinks of CO. The atmospheric inversion indicates a −2% yr −1 decrease in emissions from primary sources in East Asia from 20052016. The decreasing emissions are mainly caused by source reductions in China. The regional MEIC inventory for China is the only bottom up estimate consistent with the inversion-diagnosed decrease of CO emissions. According to the MEIC data, decreasing CO emissions from four main sectors (iron and steel industries, residential sources, gasoline-powered vehicles, and construction materials industries) in China explain 76% of the inversion-based trend of East Asian CO emissions. This result suggests that global inventories underestimate the recent decrease of CO emission factors in China which occurred despite increasing consumption of carbon-based fuels, and is driven by rapid technological changes with improved combustion efficiency and emission control measures.

Zheng, B., D. Tong, M. Li, F. Liu, C. Hong, G. Geng, H. Li, X. Li, L. Peng, J. Qi, L. Yan, Y. Zhang, H. Zhao, Y. Zheng, K. He, and Q. Zhang (2018c), Trends in China’s anthropogenic emissions since 2010 as the consequence of clean air actions, Atmospheric Chemistry and Physics, 18(19), 1409514111, doi:
To tackle the problem of severe air pollution, China has implemented active clean air policies in recent years. As a consequence, the emissions of major air pollutants have decreased and the air quality has substantially improved. Here, we quantified China’s anthropogenic emission trends from 2010 to 2017 and identified the major driving forces of these trends by using a combination of bottom-up emission inventory and index decomposition analysis (IDA) approaches. The relative change rates of China’s anthropogenic emissions during 20102017 are estimated as follows: −62 % for SO2, −17 % for NOx, +11 % for nonmethane volatile organic compounds (NMVOCs), +1 % for NH3, −27 % for CO, −38 % for PM10, −35 % for PM2.5, −27 % for BC, −35 % for OC, and +16 % for CO2. The IDA results suggest that emission control measures are the main drivers of this reduction, in which the pollution controls on power plants and industries are the most effective mitigation measures. The emission reduction rates markedly accelerated after the year 2013, confirming the effectiveness of China’s Clean Air Action that was implemented since 2013. We estimated that during 20132017, China’s anthropogenic emissions decreased by 59 % for SO2, 21 % for NOx, 23 % for CO, 36 % for PM10, 33 % for PM2.5, 28 % for BC, and 32 % for OC. NMVOC emissions increased and NH3 emissions remained stable during 20102017, representing the absence of effective mitigation measures for NMVOCs and NH3 in current policies. The relative contributions of different sectors to emissions have significantly changed after several years’ implementation of clean air policies, indicating that it is paramount to introduce new policies to enable further emission reductions in the future.


Andela, N., D. C. Morton, L. Giglio, Y. Chen, G. R. van der Werf, P. S. Kasibhatla, R. S. DeFries, G. J. Collatz, S. Hantson, S. Kloster, D. Bachelet, M. Forrest, G. Lasslop, F. Li, S. Mangeon, J. R. Melton, C. Yue, and J. T. Randerson (2017), A human-driven decline in global burned area, Science, 356(6345), 13561362, doi:10.1126/science.aal4108.
Fire is an essential Earth system process that alters ecosystem and atmospheric composition. Here we assessed long-term fire trends using multiple satellite data sets. We found that global burned area declined by 24.3 ± 8.8% over the past 18 years. The estimated decrease in burned area remained robust after adjusting for precipitation variability and was largest in savannas. Agricultural expansion and intensification were primary drivers of declining fire activity. Fewer and smaller fires reduced aerosol concentrations, modified vegetation structure, and increased the magnitude of the terrestrial carbon sink. Fire models were unable to reproduce the pattern and magnitude of observed declines, suggesting that they may overestimate fire emissions in future projections. Using economic and demographic variables, we developed a conceptual model for predicting fire in human-dominated landscapes. Global burned area has declined by ~25% over the past 18 years. Global burned area has declined by ~25% over the past 18 years.

Badia, A., O. Jorba, A. Voulgarakis, D. Dabdub, C. P. Garcia-Pando, A. Hilboll, M. Goncalves, and Z. Janjic (2017), Description and Evaluation of the Multiscale Online Nonhydrostatic AtmospheRe CHemistry Model (NMMB-MONARCH) Version 1.0: Gas-Phase Chemistry at Global Scale, Geoscientific Model Development, 10(2), 609638, doi:10.5194/gmd-10-609-2017.
This paper presents a comprehensive description and benchmark evaluation of the tropospheric gas-phase chemistry component of the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model , formerly known as NMMB/BSC-CTM, that can be run on both regional and global domains. Here, we provide an extensive evaluation of a global annual cycle simulation using a variety of background surface stations , ozonesondes , aircraft data , and satellite observations .We also include an extensive discussion of our results in comparison to other state-of-the-art models. We note that in this study, we omitted aerosol processes and some natural emissions . The model shows a realistic oxidative capacity across the globe. The seasonal cycle for CO is fairly well represented at different locations , although concentrations are underestimated in spring and winter in the Northern Hemisphere, and are overestimated throughout the year at 800 and 500 hPa in the Southern Hemisphere. Nitrogen species are well represented in almost all locations, particularly NO2 in Europe . The modeled vertical distributions of NOx and HNO3 are in excellent agreement with the observed values and the spatial and seasonal trends of tropospheric NO2 columns correspond well to observations from SCIAMACHY, capturing the highly polluted areas and the biomass burning cycle throughout the year. Over Asia, the model underestimates NOx from March to August, probably due to an underestimation of NOx emissions in the region. Overall, the comparison of the modeled CO and NO2 with MOPITT and SCIAMACHY observations emphasizes the need for more accurate emission rates from anthropogenic and biomass burning sources .

Borsdorff, T., J. A. de Brugh, H. Hu, P. Nedelec, I. Aben, and J. Landgraf (2017), Carbon monoxide column retrieval for clear-sky and cloudy atmospheres: a full-mission data set from SCIAMACHY 2.3 mu m reflectance measurements, Atmos. Meas. Tech., 10(5), 17691782, doi:10.5194/amt-10-1769-2017.
We discuss the retrieval of carbon monoxide (CO) vertical column densities from clear-sky and cloud contaminated 2311-2338 nm reflectance spectra measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) from January 2003 until the end of the mission in April 2012. These data were processed with the Shortwave Infrared CO Retrieval algorithm (SICOR) that we developed for the operational data processing of the Tropospheric Monitoring Instrument (TROPOMI) that will be launched on ESA’s Sentinel-5 Precursor (S5P) mission. This study complements previous work that was limited to clear-sky observations over land. Over the oceans, CO is estimated from cloudy-sky measurements only, which is an important addition to the SCIAMACHY clear-sky CO data set as shown by NDACC and TCCON measurements at coastal sites. For Ny-Alesund, Lauder, Mauna Loa and Reunion, a validation of SCIAMACHY clear-sky retrievals is not meaningful because of the high retrieval noise and the few collocations at these sites. The situation improves significantly when considering cloudy-sky observations, where we find a low mean bias (b) over bar = +/- 6.0 ppb and a strong correlation between the validation and the SCIAMACHY results with a mean Pearson correlation coefficient r = 0.7. Also for land observations, cloudy-sky CO retrievals present an interesting complement to the clear-sky data set. For example, at the cities Tehran and Beijing the agreement of SCIAMACHY clear-sky CO observations with MOZAIC/IAGOS airborne measurements is poor with a mean bias of (b) over bar = 171.2 ppb and 57.9 ppb because of local CO pollution, which cannot be captured by SCIAMACHY. For cloudy-sky retrievals, the validation improves significantly. Here the retrieved column is mainly sensitive to CO above the cloud and so not affected by the strong local surface emissions. Adjusting the MOZAIC/IAGOS measurements to the vertical sensitivity of the retrieval, the mean bias adds up to (b) over bar = 52.3 ppb and 5.0 ppb for Tehran and Beijing. At the less urbanised region around the airport Windhoek, local CO pollution is less prominent and so MOZAIC/IAGOS measurements agree well with SCIAMACHY clear-sky retrievals with a mean bias of (b) over bar = 15.5 ppb, but can be even further improved for cloudy SCIAMACHY observations with a mean bias of (b) over bar = 0.2 ppb. Overall the cloudy-sky CO retrievals from SCIA-MACHY short-wave infrared measurements present a major extension of the clear-sky-only data set, which more than triples the amount of data and adds unique observations over the oceans. Moreover, the study represents the first application of the S5P algorithm for operational CO data processing on cloudy observations prior to the launch of the S5P mission.

Bowman, K. W., J. Liu, A. A. Bloom, N. C. Parazoo, M. Lee, Z. Jiang, D. Menemenlis, M. M. Gierach, G. J. Collatz, K. R. Gurney, and D. Wunch (2017), Global and Brazilian Carbon Response to El Niño Modoki 20112010, Earth and Space Science, 4(10), 637660, doi:10.1002/2016EA000204.
The El Niño Modoki in 2010 led to historic droughts in Brazil. In order to understand its impact on carbon cycle variability, we derive the 20112010 annual carbon flux change (δF↑) globally and specifically to Brazil using the NASA Carbon Monitoring System Flux (CMS-Flux) framework. Satellite observations of CO2, CO, and solar-induced fluorescence (SIF) are ingested into a 4D-variational assimilation system driven by carbon cycle models to infer spatially resolved carbon fluxes including net ecosystem production, biomass burning, and gross primary productivity (GPP). The global 20112010 net carbon flux change was estimated to be δF↑=−1.60 PgC, while the Brazilian carbon flux change was −0.24 ± 0.11 PgC. This estimate is broadly within the uncertainty of previous aircraft-based estimates restricted to the Amazon basin. The 20112010 biomass burning change in Brazil was −0.24 ± 0.036 PgC, which implies a near-zero 20112010 change of the net ecosystem production (NEP): The near-zero NEP change is the result of quantitatively comparable increases GPP (0.31 ± 0.20 PgC) and respiration in 2011. Comparisons between Brazilian and global component carbon flux changes reveal complex interactions between the processes controlling annual land-atmosphere CO2 exchanges. These results show the potential of multiple satellite observations to help quantify and spatially resolve the response of productivity and respiration fluxes to climate variability.

Buchholz, R. R., M. N. Deeter, H. M. Worden, J. Gille, D. P. Edwards, J. W. Hannigan, N. B. Jones, C. Paton-Walsh, D. W. T. Griffith, D. Smale, J. Robinson, K. Strong, S. Conway, R. Sussmann, F. Hase, T. Blumenstock, E. Mahieu, and B. Langerock (2017), Validation of MOPITT carbon monoxide using ground-based Fourier transform infrared spectrometer data from NDACC, Atmos. Meas. Tech., 10(5), 19271956, doi:10.5194/amt-10-1927-2017.
The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument provides the longest continuous dataset of carbon monoxide (CO) from space. We perform the first validation of MOPITT version 6 retrievals using total column CO measurements from ground-based remote-sensing Fourier transform infrared spectrometers (FTSs). Validation uses data recorded at 14 stations, that span a wide range of latitudes (80 degrees N to 78 degrees S), in the Network for the Detection of Atmospheric Composition Change (NDACC). MOPITT measurements are spatially co-located with each station, and different vertical sensitivities between instruments are accounted for by using MOPITT averaging kernels (AKs). All three MOPITT retrieval types are analyzed: thermal infrared (TIR-only), joint thermal and near infrared (TIR-NIR), and near infrared (NIR-only). Generally, MOPITT measurements overestimate CO relative to FTS measurements, but the bias is typically less than 10 %. Mean bias is 2.4% for TIR-only, 5.1% for TIR-NIR, and 6.5% for NIR-only. The TIR-NIR and NIR-only products consistently produce a larger bias and lower correlation than the TIR-only. Validation performance of MOPITT for TIR-only and TIR-NIR retrievals over land or water scenes is equivalent. The four MOPITT detector element pixels are validated separately to account for their different uncertainty characteristics. Pixel 1 produces the highest standard deviation and lowest correlation for all three MOPITT products. However, for TIR-only and TIR-NIR, the error-weighted average that includes all four pixels often provides the best correlation, indicating compensating pixel biases and well-captured error characteristics. We find that MOPITT bias does not depend on latitude but rather is influenced by the proximity to rapidly changing atmospheric CO. MOPITT bias drift has been bound geographically to within +/- 0.5% yr 1 or lower at almost all locations.

Chatterjee, A., M. M. Gierach, A. J. Sutton, R. A. Feely, D. Crisp, A. Eldering, M. R. Gunson, C. W. O’Dell, B. B. Stephens, and D. S. Schimel (2017), Influence of El Niño on atmospheric CO2 over the tropical Pacific Ocean: Findings from NASA’s OCO-2 mission, Science, 358(6360), eaam5776, doi:10.1126/science.aam5776.
Structured Abstract INTRODUCTIONThe Orbiting Carbon Observatory-2 (OCO-2) is NASA’s first satellite designed to measure atmospheric carbon dioxide (CO2) with the precision, resolution, and coverage necessary to quantify regional carbon sources and sinks. OCO-2 launched on 2 July 2014, and during the first 2 years of its operation, a major El Niño occurred: the 20152016 El Niño, which was one of the strongest events ever recorded.El Niño and its cold counterpart La Niña (collectively known as the El NiñoSouthern Oscillation or ENSO) are the dominant modes of tropical climate variability. ENSO originates in the tropical Pacific Ocean but spurs a variety of anomalous weather patterns around the globe. Not surprisingly, it also leaves an imprint on the global carbon cycle. Understanding the magnitude and phasing of the ENSO-CO2 relationship has important implications for improving the predictability of carbon-climate feedbacks.The high-density observations from NASA’s OCO-2 mission, coupled with surface ocean CO2 measurements from NOAA buoys, have provided us with a unique data set to track the atmospheric CO2 concentrations and unravel the timing of the response of the ocean and the terrestrial carbon cycle during the 20152016 El Niño. RATIONALEDuring strong El Niño events, there is an overall increase in global atmospheric CO2 concentrations. This increase is predominantly due to the response of the terrestrial carbon cycle to El Niñoinduced changes in weather patterns. But along with the terrestrial component, the tropical Pacific Ocean also plays an important role. Typically, the tropical Pacific Ocean is a source of CO2 to the atmosphere due to equatorial upwelling that brings CO2-rich water from the interior ocean to the surface. During El Niño, this equatorial upwelling is suppressed in the eastern and the central Pacific Ocean, reducing the supply of CO2 to the surface. If CO2 fluxes were to remain constant elsewhere, this reduction in ocean-to-atmosphere CO2 fluxes should contribute to a slowdown in the growth of atmospheric CO2. This hypothesis cannot be verified, however, without large-scale CO2 observations over the tropical Pacific Ocean. RESULTSOCO-2 observations confirm that the tropical Pacific Ocean played an early and important role in the response of atmospheric CO2 concentrations to the 20152016 El Niño. By analyzing trends in the time series of atmospheric CO2, we see clear evidence of an initial decrease in atmospheric CO2 concentrations over the tropical Pacific Ocean, specifically during the early stages of the El Niño event (March through July 2015). Atmospheric CO2 concentration anomalies suggest a flux reduction of 26 to 54% that is validated by the NOAA Tropical Atmosphere Ocean (TAO) mooring CO2 data. Both the OCO-2 and TAO data further show that the reduction in ocean-to-atmosphere fluxes is spatially variable and has strong gradients across the tropical Pacific Ocean.During the later stages of the El Niño (August 2015 and later), the OCO-2 observations register a rise in atmospheric CO2 concentrations. We attribute this increase to the response from the terrestrial component of the carbon cyclea combination of reduction in biospheric uptake of CO2 over pan-tropical regions and an enhancement in biomass burning emissions over Southeast Asia and Indonesia. The net impact of the 20152016 El Niño event on the global carbon cycle is an increase in atmospheric CO2 concentrations, which would likely be larger if it were not for the reduction in outgassing from the ocean. CONCLUSIONThe strong El Niño event of 20152016 provided us with an opportunity to study how the global carbon cycle responds to a change in the physical climate system. Space-based observations of atmospheric CO2, such as from OCO-2, allow us to observe and monitor the temporal sequence of El Niñoinduced changes in CO2 concentrations. Disentangling the timing of the ocean and terrestrial responses is the first step toward interpreting their relative contribution to the global atmospheric CO2 growth rate, and thereby understanding the sensitivity of the carbon cycle to climate forcing on interannual to decadal time scales. Download high-res image Open in new tab Download Powerpoint NASA’s carbon sleuth tracks the influence of El Niño on atmospheric CO2.The tropical Pacific Ocean, the center of action during an El Niño event, is shown in cross section. Warm ocean surface temperatures are shown in red, cooler waters in blue. The Niño 3.4 region, which scientists use to study the El Niño, is denoted by yellow dashed lines. As a result of OCO-2’s global coverage and 16-day repeat cycle, it flies over the entire region every few days, keeping tabs on the changes in atmospheric CO2 concentration. Spaceborne observations of carbon dioxide (CO2) from the Orbiting Carbon Observatory-2 are used to characterize the response of tropical atmospheric CO2 concentrations to the strong El Niño event of 20152016. Although correlations between the growth rate of atmospheric CO2 concentrations and the El NiñoSouthern Oscillation are well known, the magnitude of the correlation and the timing of the responses of oceanic and terrestrial carbon cycle remain poorly constrained in space and time. We used space-based CO2 observations to confirm that the tropical Pacific Ocean does play an early and important role in modulating the changes in atmospheric CO2 concentrations during El Niño eventsa phenomenon inferred but not previously observed because of insufficient high-density, broad-scale CO2 observations over the tropics.

Deeter, M. N., D. P. Edwards, G. L. Francis, J. C. Gille, S. Martinez-Alonso, H. M. Worden, and C. Sweeney (2017), A Climate-scale Satellite Record for Carbon Monoxide: The MOPITT Version 7 Product, Atmos. Meas. Tech. Discuss., 2017, 134, doi:10.5194/amt-2017-71.
The MOPITT (“Measurements of Pollution in the Troposphere”) satellite instrument has been making observations of atmospheric carbon monoxide since 2000. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the Version 7 (V7) product. Improvements include (1) representation of growing atmospheric concentrations of N2O, (2) use of meteorological fields from the MERRA-2 reanalysis for the entire MOPITT mission (instead of MERRA), (3) use of the MODIS Collection 6 cloud mask product (instead of Collection 5), (4) a new strategy for radiance bias correction, and (5) an improved method for calibrating MOPITT’s NIR radiances. Statistical comparisons of V7 validation results with corresponding V6 results are presented, using aircraft in-situ measurements as the reference. Clear improvements are demonstrated for V7 products with respect to overall retrieval biases, bias variability, and bias drift uncertainty.

Dekker, I. N., S. Houweling, I. Aben, T. Röckmann, M. Krol, S. Martínez-Alonso, M. N. Deeter, and H. M. Worden (2017), Quantification of CO emissions from the city of madrid using MOPITT satellite retrievals and WRF simulations, Atmospheric Chemistry and Physics, 17(23), 1467514694, doi:10.5194/acp-17-14675-2017.

The growth of mega-cities leads to air quality problems directly affecting the citizens. Satellite measurements are becoming of higher quality and quantity, which leads to more accurate satellite retrievals of enhanced air pollutant concentrations over large cities. In this paper, we compare and discuss both an existing and a new method for estimating urban-scale trends in CO emissions using multiyear retrievals from the MOPITT satellite instrument. The first method is mainly based on satellite data, and has the advantage of fewer assumptions, but also comes with uncertainties and limitations as shown in this paper. To improve the reliability of urban-To-regional scale emission trend estimation, we simulate MOPITT retrievals using the Weather Research and Forecast model with chemistry core (WRFChem). The difference between model and retrieval is used to optimize CO emissions in WRF-Chem, focusing on the city of Madrid, Spain. This method has the advantage over the existing method in that it allows both a trend analysis of CO concentrations and a quantification of CO emissions. Our analysis confirms that MOPITT is capable of detecting CO enhancements over Madrid, although significant differences remain between the yearly averaged model output and satellite measurements (R2 D0.75) over the city. After optimization, we find Madrid CO emissions to be lower by 48% for 2002 and by 17% for 2006 compared with the EdgarV4.2 emission inventory. The MOPITT-derived emission adjustments lead to better agreement with the European emission inventory TNO-MAC-III for both years. This suggests that the downward trend in CO emissions over Madrid is overestimated in EdgarV4.2 and more realistically represented in TNO-MACC-III. However, our satellite and model based emission estimates have large uncertainties, around 20% for 2002 and 50% for 2006.

Eldering, A., P. O. Wennberg, D. Crisp, D. S. Schimel, M. R. Gunson, A. Chatterjee, J. Liu, F. M. Schwandner, Y. Sun, C. W. O’Dell, C. Frankenberg, T. Taylor, B. Fisher, G. B. Osterman, D. Wunch, J. Hakkarainen, J. Tamminen, and B. Weir (2017), The Orbiting Carbon Observatory-2 early science investigations of regional carbon dioxide fluxes, Science, 358(6360), eaam5745, doi:10.1126/science.aam5745.
Structured Abstract INTRODUCTIONEarth’s carbon cycle involves large fluxes of carbon dioxide (CO2) between the atmosphere, land biosphere, and oceans. Over the past several decades, net loss of CO2 from the atmosphere to the land and oceans has varied considerably from year to year, equaling 20 to 80% of CO2 emissions from fossil fuel combustion and land use change. On average, the uptake is about 50%. The imbalance between CO2 emissions and removal is seen in increasing atmospheric CO2 concentrations. In recent years, an increase of 2 to 3 parts per million (ppm) per year in the atmospheric mole fraction, which is currently about 400 ppm, has been observed.Almost a quarter of the CO2 emitted by human activities is being absorbed by the ocean, and another quarter is absorbed by processes on land. The identity and location of the terrestrial sinks are poorly understood. This absorption has been attributed by some to tropical or Eurasian temperate forests, whereas others argue that these regions may be net sources of CO2. The efficiency of these land sinks appears to vary dramatically from year to year. Because the identity, location, and processes controlling these natural sinks are not well constrained, substantial additional uncertainty is added to projections of future CO2 levels. RATIONALEThe NASA satellite, the Orbiting Carbon Observatory-2 (OCO-2), which was launched on 2 July 2014, is designed to collect global measurements with sufficient precision, coverage, and resolution to aid in resolving sources and sinks of CO2 on regional scales. Since 6 September 2014, the OCO-2 mission has been producing about 2 million estimates of the column-averaged CO2 dry-air mole fraction (Embedded Image) each month after quality screening, with spatial resolution of <3 km2 per sounding. Solar-induced chlorophyll fluorescence (SIF), a small amount of light emitted during photosynthesis, is detected in remote sensing measurements of radiance within solar Fraunhofer lines and is another data product from OCO-2. RESULTSThe measurements from OCO-2 provide a global view of the seasonal cycles and spatial patterns of atmospheric CO2, with the anticipated year-over-year growth rate. The buildup of CO2 in the Northern Hemisphere during winter and its rapid decrease in concentration as spring arrives (and the SIF increases) is seen in unprecedented detail. The enhanced CO2 in urban areas relative to nearby background areas is observed with a single overpass of OCO-2. Increases in CO2 due to the biomass burning in Africa are also clearly observed. The dense, global, Embedded Image and SIF data sets from OCO-2 are combined with other remote sensing data sets and used to disentangle the processes driving the carbon cycle on regional scales during the recent 20152016 El Niño event. This analysis shows more carbon release in 2015 relative to 2011 over Africa, South America, and Southeast Asia. Now, the fundamental driver for the change in carbon release can be assessed continent by continent, rather than treating the tropics as a single, integrated region. Small changes in Embedded Image were also observed early in the El Niño over the equatorial eastern Pacific, due to less upwelling of cold, carbon-rich water than is typical. CONCLUSIONNASA’s OCO-2 mission is collecting a dense, global set of high-spectral resolution measurements that are used to estimate Embedded Image and SIF. The OCO-2 mission data set can now be used to assess regional-scale sources and sinks of CO2 around the globe. The papers in this collection present early scientific findings from this new data set. Download high-res image Open in new tab Download Powerpoint El Niño impact on carbon flux in 2015 relative to 2011, detected from Greenhouse Gases Observing Satellite (GOSAT) and OCO-2 data.OCO-2 uses reflected sunlight to derive Embedded Image and SIF. This shows OCO-2 Embedded Image data over North America from 12 August 2015 to 26 August 2015. NASA’s Orbiting Carbon Observatory-2 (OCO-2) mission was motivated by the need to diagnose how the increasing concentration of atmospheric carbon dioxide (CO2) is altering the productivity of the biosphere and the uptake of CO2 by the oceans. Launched on 2 July 2014, OCO-2 provides retrievals of the column-averaged CO2 dry-air mole fraction (Embedded Image) as well as the fluorescence from chlorophyll in terrestrial plants. The seasonal pattern of uptake by the terrestrial biosphere is recorded in fluorescence and the drawdown of Embedded Image during summer. Launched just before one of the most intense El Niños of the past century, OCO-2 measurements of Embedded Image and fluorescence record the impact of the large change in ocean temperature and rainfall on uptake and release of CO2 by the oceans and biosphere.

Flemming, J., A. Benedetti, A. Inness, R. J. Engelen, L. Jones, V. Huijnen, S. Remy, M. Parrington, M. Suttie, A. Bozzo, V.-H. Peuch, D. Akritidis, and E. Katragkou (2017), The CAMS interim Reanalysis of Carbon Monoxide, Ozone and Aerosol for 20032015, Atmospheric Chemistry and Physics, 17(3), 19451983, doi:

Abstract. A new global reanalysis data set of atmospheric composition (AC) for the period 20032015 has been produced by the Copernicus Atmosphere Monitoring Service (CAMS). Satellite observations of total column (TC) carbon monoxide (CO) and aerosol optical depth (AOD), as well as several TC and profile observations of ozone, have been assimilated with the Integrated Forecasting System for Composition (C-IFS) of the European Centre for Medium-Range Weather Forecasting. Compared to the previous Monitoring Atmospheric Composition and Climate (MACC) reanalysis (MACCRA), the new CAMS interim reanalysis (CAMSiRA) is of a coarser horizontal resolution of about 110 km, compared to 80 km, but covers a longer period with the intent to be continued to present day. This paper compares CAMSiRA with MACCRA and a control run experiment (CR) without assimilation of AC retrievals. CAMSiRA has smaller biases than the CR with respect to independent observations of CO, AOD and stratospheric ozone. However, ozone at the surface could not be improved by the assimilation because of the strong impact of surface processes such as dry deposition and titration with nitrogen monoxide (NO), which were both unchanged by the assimilation. The assimilation of AOD led to a global reduction of sea salt and desert dust as well as an exaggerated increase in sulfate. Compared to MACCRA, CAMSiRA had smaller biases for AOD, surface CO and TC ozone as well as for upper stratospheric and tropospheric ozone. Finally, the temporal consistency of CAMSiRA was better than the one of MACCRA. This was achieved by using a revised emission data set as well as by applying careful selection and bias correction to the assimilated retrievals. CAMSiRA is therefore better suited than MACCRA for the study of interannual variability, as demonstrated for trends in surface CO.

Gaubert, B., H. M. Worden, A. F. J. Arellano, L. K. Emmons, S. Tilmes, J. Barre, S. M. Alonso, F. Vitt, J. L. Anderson, F. Alkemade, S. Houweling, and D. P. Edwards (2017), Chemical Feedback From Decreasing Carbon Monoxide Emissions, Geophys. Res. Lett., 44(19), 99859995, doi:10.1002/2017GL074987.
Understanding changes in the burden and growth rate of atmospheric methane (CH4) has been the focus of several recent studies but still lacks scientific consensus. Here we investigate the role of decreasing anthropogenic carbon monoxide (CO) emissions since 2002 on hydroxyl radical (OH) sinks and tropospheric CH4 loss. We quantify this impact by contrasting two model simulations for 2002-2013: (1) a Measurement of the Pollution in the Troposphere (MOPITT) CO reanalysis and (2) a Control-Run without CO assimilation. These simulations are performed with the Community Atmosphere Model with Chemistry of the Community Earth System Model fully coupled chemistry climate model with prescribed CH4 surface concentrations. The assimilation of MOPITT observations constrains the global CO burden, which significantly decreased over this period by similar to 20%. We find that this decrease results to (a) increase in CO chemical production, (b) higher CH4 oxidation by OH, and (c) similar to 8% shorter CH4 lifetime. We elucidate this coupling by a surrogate mechanism for CO-OH-CH4 that is quantified from the full chemistry simulations.

Jeong, U., J. Kim, H. Lee, and Y. G. Lee (2017), Assessing the effect of long-range pollutant transportation on air quality in Seoul using the conditional potential source contribution function method, Atmospheric Environment, 150, 3344, doi:10.1016/j.atmosenv.2016.11.017.
It is important to estimate the effects of the long-range transport of atmospheric pollutants for efficient and effective strategies to control air quality. In this study, the contributions of trans-boundary transport to the mean concentrations of SO2, NO2, CO, and PM10 in Seoul, Korea from 2001 to 2014 were estimated based on the conditional potential source contribution function (CPSCF) method. Eastern China was found to be the major source of trans-boundary pollution in Seoul, but moderate sources were also located in northeastern China. The contribution of long-range transport from Japan was negligible. The spatial distributions of the potential source contribution function (PSCF) values of each pollutant showed reasonable consistency with their emission inventory and satellite products. The PSCF values of SO2 and PM10 from eastern China were higher than those of NO2 and CO. The mean concentrations of SO2, NO2, CO, and PM10 in Seoul for the period from 2001 to 2014 were 5.34, 37.0, and 619.1 ppb, and 57.4 4 μg/m3, respectively. The contributions of long-range transport to the mean concentrations of SO2, NO2, CO, and PM10 in Seoul were 0.74, 3.4, and 39.0 ppb, and 12.1 μg/m3, respectively, which are 14%, 9%, 6%, and 21% of the mean concentrations, respectively. The annual mean concentrations of SO2 and NO2 followed statistically significant increasing linear trends (0.5 and 1.6 ppb per decade, respectively), whereas the trends in the annual mean concentrations of CO and PM10 were statistically insignificant. The trends in the ratio of the increased concentrations associated with long-range transport to the annual mean concentrations of the pollutants were statistically insignificant. However, the results indicate that the trans-boundary transport of SO2, NO2, CO, and PM10 from eastern China consistently affected air quality in Seoul over the study period (20012014). Regionally, the effects of the long-range transport of pollutants from Beijing and Harbin-Changchun on air quality in Seoul have become more significant over this period.

Jiang, Z., J. R. Worden, H. Worden, M. Deeter, D. B. A. Jones, A. F. Arellano, and D. K. Henze (2017), A 15-year record of CO emissions constrained by MOPITT CO observations, Atmos. Chem. Phys., 17(7), 45654583, doi:10.5194/acp-17-4565-2017.
Long-term measurements from satellites and surface stations have demonstrated a decreasing trend of tropospheric carbon monoxide (CO) in the Northern Hemisphere over the past decade. Likely explanations for this decrease include changes in anthropogenic, fires, and/or biogenic emissions or changes in the primary chemical sink hydroxyl radical (OH). Using remotely sensed CO measurements from the Measurement of Pollution in the Troposphere (MOPITT) satellite instrument, in situ methyl chloroform (MCF) measurements from the World Data Centre for Greenhouse Gases (WDCGG) and the adjoint of the GEOS-Chem model, we estimate the change in global CO emissions from 2001 to 2015. We show that the loss rate of MCF varied by 0.2 % in the past 15 years, indicating that changes in global OH distributions do not explain the recent decrease in CO. Our two-step inversion approach for estimating CO emissions is intended to mitigate the effect of bias errors in the MOPITT data as well as model errors in transport and chemistry, which are the primary factors contributing to the uncertainties when quantifying CO emissions using these remotely sensed data. Our results confirm that the decreasing trend of tropospheric CO in the Northern Hemisphere is due to decreasing CO emissions from anthropogenic and biomass burning sources. In particular, we find decreasing CO emissions from the United States and China in the past 15 years, and unchanged anthropogenic CO emissions from Europe since 2008. We find decreasing trends of biomass burning CO emissions from boreal North America, boreal Asia and South America, but little change over Africa. In contrast to prior results, we find that a positive trend in CO emissions is likely for India and southeast Asia.

Khan, A., J. E. Szulejko, M.-S. Bae, Z. H. Shon, J.-R. Sohn, J. W. Seo, E.-C. Jeon, and K.-H. Kim (2017a), Long-term trend analysis of CO in the Yongsan district of Seoul, Korea, between the years 1987 and 2013, Atmospheric Pollution Research, doi:10.1016/j.apr.2017.03.006. [online] Available from: .
In this study, the long-term trend in atmospheric carbon monoxide (CO) concentration was analyzed using the CO levels measured (intermittently) at an air quality monitoring (AQM) station in Seoul, Korea, between the years 1987 and 2013. Temporal trends in CO were analyzed on an annual and seasonal basis in reference to other important air pollutants such as methane (CH4), particulate matter (PM10), sulfur dioxide (SO2), nitrogen monoxide (NO), nitrogen dioxide (NO2), mercury (Hg), and ozone (O3). The annual mean of CO for the entire period was 0.93 ± 0.22 ppm. CO levels were reduced by 83% from 3.25 ± 0.78 ppm (1987) to 0.51 ± 0.31 ppm (2013). Its relative reduction was compared over three periods chosen arbitrarily as period 1 (fast reduction, 19871988), period 2 (intermediate reduction, 19992000), and period 3 (slow reduction, 20042013). The concentrations of CO were strongly correlated with others (e.g., SO2, NO, NO2, O3, and Hg), suggesting the effects of similar source processes (e.g., fuel combustion). The reduction in its level was marginally consistent with the decreasing trend in the total CO column concentration in Seoul by the Measurements of Pollution in the Troposphere (MOPITT) satellite between 2000 and 2013, indicating decreasing anthropogenic CO emissions (despite increasing anthropogenic CO2 emissions). The rapid relative reduction of CO in period 1 and the subsequent slower but moderate reduction thereafter appear to reflect the effects of both enforcement of administrative regulations and advances in emissions control technologies.

Khan, A., J. E. Szulejko, M.-S. Bae, Z. H. Shon, J.-R. Sohn, J. W. Seo, E.-C. Jeon, and K.-H. Kim (2017b), Long-term trend analysis of CO in the Yongsan district of Seoul, Korea, between the years 1987 and 2013, Atmospheric Pollution Research, 8(5), 988996, doi:10.1016/j.apr.2017.03.006.
In this study, the long-term trend in atmospheric carbon monoxide (CO) concentration was analyzed using the CO levels measured (intermittently) at an air quality monitoring (AQM) station in Seoul, Korea, between the years 1987 and 2013. Temporal trends in CO were analyzed on an annual and seasonal basis in reference to other important air pollutants such as methane (CH4), particulate matter (PM10), sulfur dioxide (SO2), nitrogen monoxide (NO), nitrogen dioxide (NO2), mercury (Hg), and ozone (O3). The annual mean of CO for the entire period was 0.93 ± 0.22 ppm. CO levels were reduced by 83% from 3.25 ± 0.78 ppm (1987) to 0.51 ± 0.31 ppm (2013). Its relative reduction was compared over three periods chosen arbitrarily as period 1 (fast reduction, 19871988), period 2 (intermediate reduction, 19992000), and period 3 (slow reduction, 20042013). The concentrations of CO were strongly correlated with others (e.g., SO2, NO, NO2, O3, and Hg), suggesting the effects of similar source processes (e.g., fuel combustion). The reduction in its level was marginally consistent with the decreasing trend in the total CO column concentration in Seoul by the Measurements of Pollution in the Troposphere (MOPITT) satellite between 2000 and 2013, indicating decreasing anthropogenic CO emissions (despite increasing anthropogenic CO2 emissions). The rapid relative reduction of CO in period 1 and the subsequent slower but moderate reduction thereafter appear to reflect the effects of both enforcement of administrative regulations and advances in emissions control technologies.

Kulawik, S. S., C. O’Dell, V. H. Payne, L. Kuai, H. M. Worden, S. C. Biraud, C. Sweeney, B. Stephens, L. T. Iraci, E. L. Yates, and T. Tanaka (2017), Lower-tropospheric CO2 from near-infrared ACOS-GOSAT observations, Atmos. Chem. Phys., 17(8), 54075438, doi:10.5194/acp-17-5407-2017.
We present two new products from near-infrared Greenhouse Gases Observing Satellite (GOSAT) observations: lowermost tropospheric (LMT, from 0 to 2.5 km) and upper tropospheric-stratospheric (U, above 2.5 km) carbon dioxide partial column mixing ratios. We compare these new products to aircraft profiles and remote surface flask measurements and find that the seasonal and year-to-year variations in the new partial column mixing ratios significantly improve upon the Atmospheric CO2 Observations from Space (ACOS) and GOSAT (ACOS-GOSAT) initial guess and/or a priori, with distinct patterns in the LMT and U seasonal cycles that match validation data. For land monthly averages, we find errors of 1.9, 0.7, and 0.8 ppm for retrieved GOSAT LMT, U, and X CO2; for ocean monthly averages, we find errors of 0.7, 0.5, and 0.5 ppm for retrieved GOSAT LMT, U, and X CO2. In the southern hemispheric biomass burning season, the new partial columns show similar patterns to MODIS fire maps and MOPITT multispectral CO for both vertical levels, despite a flat ACOS-GOSAT prior, and a CO-CO2 emission factor comparable to published values. The difference of LMT and U, useful for evaluation of model transport error, has also been validated with a monthly average error of 0.8 (1.4) ppm for ocean (land). LMT is more locally influenced than U, meaning that local fluxes can now be better separated from CO2 transported from far away.

Li, M., Q. Zhang, J. Kurokawa, J.-H. Woo, K. He, Z. Lu, T. Ohara, Y. Song, D. G. Streets, G. R. Carmichael, Y. Cheng, C. Hong, H. Huo, X. Jiang, S. Kang, F. Liu, H. Su, and B. Zheng (2017), MIX: a mosaic Asian anthropogenic emission inventory under the international collaboration framework of the MICS-Asia and HTAP, Atmospheric Chemistry and Physics, 17(2), 935963, doi:

Abstract. The MIX inventory is developed for the years 2008 and 2010 to support the Model Inter-Comparison Study for Asia (MICS-Asia) and the Task Force on Hemispheric Transport of Air Pollution (TF HTAP) by a mosaic of up-to-date regional emission inventories. Emissions are estimated for all major anthropogenic sources in 29 countries and regions in Asia. We conducted detailed comparisons of different regional emission inventories and incorporated the best available ones for each region into the mosaic inventory at a uniform spatial and temporal resolution. Emissions are aggregated to five anthropogenic sectors: power, industry, residential, transportation, and agriculture. We estimate the total Asian emissions of 10 species in 2010 as follows: 51.3 Tg SO2, 52.1 Tg NOx, 336.6 Tg CO, 67.0 Tg NMVOC (non-methane volatile organic compounds), 28.8 Tg NH3, 31.7 Tg PM10, 22.7 Tg PM2.5, 3.5 Tg BC, 8.3 Tg OC, and 17.3 Pg CO2. Emissions from China and India dominate the emissions of Asia for most of the species. We also estimated Asian emissions in 2006 using the same methodology of MIX. The relative change rates of Asian emissions for the period of 20062010 are estimated as follows: −8.1 % for SO2, +19.2 % for NOx, +3.9 % for CO, +15.5 % for NMVOC, +1.7 % for NH3, −3.4 % for PM10, −1.6 % for PM2.5, +5.5 % for BC, +1.8 % for OC, and +19.9 % for CO2. Model-ready speciated NMVOC emissions for SAPRC-99 and CB05 mechanisms were developed following a profile-assignment approach. Monthly gridded emissions at a spatial resolution of 0.25° × 0.25° are developed and can be accessed from

Liu, J., K. W. Bowman, D. S. Schimel, N. C. Parazoo, Z. Jiang, M. Lee, A. A. Bloom, D. Wunch, C. Frankenberg, Y. Sun, C. W. O’Dell, K. R. Gurney, D. Menemenlis, M. Gierach, D. Crisp, and A. Eldering (2017), Contrasting carbon cycle responses of the tropical continents to the 20152016 El Niño, Science, 358(6360), eaam5690, doi:10.1126/science.aam5690.
Structured Abstract INTRODUCTIONThe influence of El Niño on climate is accompanied by large changes to the carbon cycle, and El Niñoinduced variability in the carbon cycle has been attributed mainly to the tropical continents. However, owing to a dearth of observations in the tropics, tropical carbon fluxes are poorly quantified, and considerable debate exists over the dominant mechanisms (e.g., plant growth, respiration, fire) and regions (e.g., humid versus semiarid tropics) on the net carbon balance. RATIONALEThe launch of the Orbiting Carbon Observatory-2 (OCO-2) shortly before the 20152016 El Niño, the second strongest since the 1950s, has provided an opportunity to understand how tropical land carbon fluxes respond to the warm and dry climate characteristics of El Niño conditions. The El Niño events may also provide a natural experiment to study the response of tropical land carbon fluxes to future climate changes, because anomalously warm and dry tropical environments typical of El Niño are expected to be more frequent under most emission scenarios. RESULTSThe tropical regions of three continents (South America, Asia, and Africa) had heterogeneous responses to the 20152016 El Niño, in terms of both climate drivers and the carbon cycle. The annual mean precipitation over tropical South America and tropical Asia was lower by 3.0σ and 2.8σ, respectively, in 2015 relative to the 2011 La Niña year. Tropical Africa, on the other hand, had near equal precipitation and the same number of dry months between 2015 and 2011; however, surface temperatures were higher by 1.6σ, dominated by the positive anomaly over its eastern and southern regions. In response to the warmer and drier climate anomaly in 2015, the pantropical biosphere released 2.5 ± 0.34 gigatons more carbon into the atmosphere than in 2011, which accounts for 83.3% of the global total 3.0gigatons of carbon (gigatons C) net biosphere flux differences and 92.6% of the atmospheric CO2 growth-rate differences between 2015 and 2011. It indicates that the tropical land biosphere flux anomaly was the driver of the highest atmospheric CO2 growth rate in 2015. The three tropical continents had an approximately even contribution to the pantropical net carbon flux anomaly in 2015, but had diverse dominant processes: gross primary production (GPP) reduced carbon uptake (0.9 ± 0.96 gigatons C) in tropical South America, fire increased carbon release (0.4 ± 0.08 gigatons C) in tropical Asia, and respiration increased carbon release (0.6 ± 1.01 gigatons C) in Africa. We found that most of the excess carbon release in 2015 was associated with either extremely low precipitation or high temperatures, or both. CONCLUSIONOur results indicate that the global El Niño effect is a superposition of regionally specific effects. The heterogeneous climate forcing and carbon response over the three tropical continents to the 20152016 El Niño challenges previous studies that suggested that a single dominant process determines carbon cycle interannual variability, which could also be due to previous disturbance and soil and vegetation structure. The similarity between the 2015 tropical climate anomaly and the projected climate changes imply that the role of the tropical land as a buffer for fossil fuel emissions may be reduced in the future. The heterogeneous response may reflect differences in temperature and rainfall anomalies, but intrinsic differences in vegetation species, soils, and prior disturbance may contribute as well. A synergistic use of multiple satellite observations and a long time series of spatially resolved fluxes derived from sustained satellite observations will enable tests of these hypotheses, allow for a more process-based understanding, and, ultimately, aid improved carbon-climate model projections. Download high-res image Open in new tab Download Powerpoint Diverse climate driver anomalies and carbon cycle responses to the 20152016 El Niño over the three tropical continents.Schematic of climate anomaly patterns over the three tropical continents and the anomalies of the net carbon flux and its dominant constituent flux (i.e., GPP, respiration, and fire) relative to the 2011 La Niña during the 20152016 El Niño. GtC, gigatons C. The 20152016 El Niño led to historically high temperatures and low precipitation over the tropics, while the growth rate of atmospheric carbon dioxide (CO2) was the largest on record. Here we quantify the response of tropical net biosphere exchange, gross primary production, biomass burning, and respiration to these climate anomalies by assimilating column CO2, solar-induced chlorophyll fluorescence, and carbon monoxide observations from multiple satellites. Relative to the 2011 La Niña, the pantropical biosphere released 2.5 ± 0.34 gigatons more carbon into the atmosphere in 2015, consisting of approximately even contributions from three tropical continents but dominated by diverse carbon exchange processes. The heterogeneity of the carbon-exchange processes indicated here challenges previous studies that suggested that a single dominant process determines carbon cycle interannual variability.

van Marle, M. J. E., R. D. Field, G. R. van der Werf, I. A. E. de Wagt, R. A. Houghton, L. V. Rizzo, P. Artaxo, and K. Tsigaridis (2017), Fire and deforestation dynamics in Amazonia (19732014), Global Biogeochemical Cycles, 31(1), 2438, doi:10.1002/2016GB005445.
Consistent long-term estimates of fire emissions are important to understand the changing role of fire in the global carbon cycle and to assess the relative importance of humans and climate in shaping fire regimes. However, there is limited information on fire emissions from before the satellite era. We show that in the Amazon region, including the Arc of Deforestation and Bolivia, visibility observations derived from weather stations could explain 61% of the variability in satellite-based estimates of bottom-up fire emissions since 1997 and 42% of the variability in satellite-based estimates of total column carbon monoxide concentrations since 2001. This enabled us to reconstruct the fire history of this region since 1973 when visibility information became available. Our estimates indicate that until 1987 relatively few fires occurred in this region and that fire emissions increased rapidly over the 1990s. We found that this pattern agreed reasonably well with forest loss data sets, indicating that although natural fires may occur here, deforestation and degradation were the main cause of fires. Compared to fire emissions estimates based on Food and Agricultural Organization’s Global Forest and Resources Assessment data, our estimates were substantially lower up to the 1990s, after which they were more in line. These visibility-based fire emissions data set can help constrain dynamic global vegetation models and atmospheric models with a better representation of the complex fire regime in this region.

Miyazaki, K., and K. Bowman (2017), Evaluation of ACCMIP ozone simulations and ozonesonde sampling biases using a satellite-based multi-constituent chemical reanalysis, Atmos. Chem. Phys., 17(13), 82858312, doi:10.5194/acp-17-8285-2017.
The Atmospheric Chemistry Climate Model Intercomparison Project (ACCMIP) ensemble ozone simulations for the present day from the 2000 decade simulation results are evaluated by a state-of-the-art multi-constituent atmospheric chemical reanalysis that ingests multiple satellite data including the Tropospheric Emission Spectrometer (TES), the Microwave Limb Sounder (MLS), the Ozone Monitoring Instrument (OMI), and the Measurement of Pollution in the Troposphere (MOPITT) for 20052009. Validation of the chemical reanalysis against global ozonesondes shows good agreement throughout the free troposphere and lower stratosphere for both seasonal and year-to-year variations, with an annual mean bias of less than 0.9 ppb in the middle and upper troposphere at the tropics and mid-latitudes. The reanalysis provides comprehensive spatiotemporal evaluation of chemistry-model performance that compliments direct ozonesonde comparisons, which are shown to suffer from significant sampling bias. The reanalysis reveals that the ACCMIP ensemble mean overestimates ozone in the northern extratropics by 611 ppb while underestimating by up to 18 ppb in the southern tropics over the Atlantic in the lower troposphere. Most models underestimate the spatial variability of the annual mean lower tropospheric concentrations in the extratropics of both hemispheres by up to 70 %. The ensemble mean also overestimates the seasonal amplitude by 2570 % in the northern extratropics and overestimates the inter-hemispheric gradient by about 30 % in the lower and middle troposphere. A part of the discrepancies can be attributed to the 5-year reanalysis data for the decadal model simulations. However, these differences are less evident with the current sonde network. To estimate ozonesonde sampling biases, we computed model bias separately for global coverage and the ozonesonde network. The ozonesonde sampling bias in the evaluated model bias for the seasonal mean concentration relative to global coverage is 4050 % over the western Pacific and east Indian Ocean and reaches 110 % over the equatorial Americas and up to 80 % for the global tropics. In contrast, the ozonesonde sampling bias is typically smaller than 30 % for the Arctic regions in the lower and middle troposphere. These systematic biases have implications for ozone radiative forcing and the response of chemistry to climate that can be further quantified as the satellite observational record extends to multiple decades.

Miyazaki, K., H. Eskes, K. Sudo, K. F. Boersma, K. Bowman, and Y. Kanaya (2017), Decadal changes in global surface NOx emissions from multi-constituent satellite data assimilation, Atmospheric Chemistry and Physics, 17(2), 807837, doi:

Abstract. Global surface emissions of nitrogen oxides (NOx) over a 10-year period (2005&ndash;2014) are estimated from an assimilation of multiple satellite data sets: tropospheric NO2 columns from Ozone Monitoring Instrument (OMI), Global Ozone Monitoring Experiment-2 (GOME-2), and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), O3 profiles from Tropospheric Emission Spectrometer (TES), CO profiles from Measurement of Pollution in the Troposphere (MOPITT), and O3 and HNO3 profiles from Microwave Limb Sounder (MLS) using an ensemble Kalman filter technique. Chemical concentrations of various species and emission sources of several precursors are simultaneously optimized. This is expected to improve the emission inversion because the emission estimates are influenced by biases in the modelled tropospheric chemistry, which can be partly corrected by also optimizing the concentrations. We present detailed distributions of the estimated emission distributions for all major regions, the diurnal and seasonal variability, and the evolution of these emissions over the 10-year period. The estimated regional total emissions show a strong positive trend over India (+29 % decade−1), China (+26 % decade−1), and the Middle East (+20 % decade−1), and a negative trend over the USA (−38 % decade−1), southern Africa (−8.2 % decade−1), and western Europe (−8.8 % decade−1). The negative trends in the USA and western Europe are larger during 2005&ndash;2010 relative to 2011&ndash;2014, whereas the trend in China becomes negative after 2011. The data assimilation also suggests a large uncertainty in anthropogenic and fire-related emission factors and an important underestimation of soil NOx sources in the emission inventories. Despite the large trends observed for individual regions, the global total emission is almost constant between 2005 (47.9 Tg N yr−1) and 2014 (47.5 Tg N yr−1).

Mok, J., S. S. Park, H. Lim, J. Kim, D. Edwards, J. Lee, J. Yoon, Y. G. Lee, and J.-H. Koo (2017a), Correlation analysis between regional carbon monoxide and black carbon from satellite measurements, Atmospheric Research, doi:10.1016/j.atmosres.2017.04.004. [online] Available from: .
In this study, we present and compare regional correlations between CO total column density (TCDCO) from the data set of Measurement of Pollution in the Troposphere (MOPITT), and high-absorbing BC dominant aerosol optical depth (AODBC) from the retrieval algorithm using Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) (MODIS-OMI algorithm, MOA). TCDCO shows positive relationship to both fine-mode AOD (AODFM) and AODBC in general, but TCDCO better correlates with AODBC than AODFM. This enhanced correlation between TCDCO and AODBC appears more clearly during spring and summer. Correlation between TCDCO and AODBC is exceptionally poor in Northern Africa where the BC-dominated aerosols are frequently mixed with mineral dust particles from the Sahara. Another issue is also found in Southern Africa; the correlation between AODBC and TCDCO in this region is not much higher than that between the AODFM and TCDCO in spite of large occurrence of biomass burning and wildfire. This can be explained by the cloud perturbation near the source regions and dispersion effect due to the typical wind pattern. Correlations between AODBC and TCDCO increase further when fire detected areas are only considered, but does not change much over the urban area. This difference clarifies the large contribution of burning events to the positive relationship between BC and CO. All findings in this study demonstrate a possible use of satellite CO product in evaluating the BC-dominated aerosol product from satellite remote sensing over the globe.

Mok, J., S. S. Park, H. Lim, J. Kim, D. P. Edwards, J. Lee, J. Yoon, Y. G. Lee, and J.-H. Koo (2017b), Correlation analysis between regional carbon monoxide and black carbon from satellite measurements, Atmos. Res., 196, 2939, doi:10.1016/j.atmosres.2017.04.004.
In this study, we present and compare regional correlations between CO total column density (TCDco) from the data set of Measurement of Pollution in the Troposphere (MOPITT), and high-absorbing BC dominant aerosol optical depth (AOD(Bc)) from the retrieval algorithm using Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) (MODIS-OMI algorithm, MOA). TCDco shows positive relationship to both fine -mode AOD (AOD(Fm)) and AODBc in general, but TCDco better correlates with AODBc than AODFm. This enhanced correlation between TCDco and AODBc appears more clearly during spring and summer. Correlation between TCDco and AODBc is exceptionally poor in Northern Africa where the BC dominated aerosols are frequently mixed with mineral dust particles from the Sahara. Another issue is also found in Southern Africa; the correlation between AODBc and TCDco in this region is not much higher than that between the AODFm and TCDco in spite of large occurrence of biomass burning and wildfire. This can be explained by the cloud perturbation near the source regions and dispersion effect due to the typical wind pattern. Correlations between AODBc and TCDco increase further when fire detected areas are only considered, but does not change much over the urban area. This difference clarifies the large contribution of burning events to the positive relationship between BC and CO. All findings in this study demonstrate a possible use of satellite CO product in evaluating the BC-dominated aerosol product from satellite remote sensing over the globe.

Monks, S. A., S. R. Arnold, M. J. Hollaway, R. J. Pope, C. Wilson, W. Feng, K. M. Emmerson, B. J. Kerridge, B. L. Latter, G. M. Miles, R. Siddans, and M. P. Chipperfield (2017), The TOMCAT global chemical transport model v1.6: description of chemical mechanism and model evaluation, Geoscientific Model Development, 10(8), 30253057, doi:

Abstract. This paper documents the tropospheric chemical mechanism scheme used in the TOMCAT 3-D chemical transport model. The current scheme includes a more detailed representation of hydrocarbon chemistry than previously included in the model, with the inclusion of the emission and oxidation of ethene, propene, butane, toluene and monoterpenes. The model is evaluated against a range of surface, balloon, aircraft and satellite measurements. The model is generally able to capture the main spatial and seasonal features of high and low concentrations of carbon monoxide (CO), ozone (O3), volatile organic compounds (VOCs) and reactive nitrogen. However, model biases are found in some species, some of which are common to chemistry models and some that are specific to TOMCAT and warrant further investigation. The most notable of these biases are (1) a negative bias in Northern Hemisphere (NH) winter and spring CO and a positive bias in Southern Hemisphere (SH) CO throughout the year, (2) a positive bias in NH O3 in summer and a negative bias at high latitudes during SH winter and (3) a negative bias in NH winter C2 and C3 alkanes and alkenes. TOMCAT global mean tropospheric hydroxyl radical (OH) concentrations are higher than estimates inferred from observations of methyl chloroform but similar to, or lower than, multi-model mean concentrations reported in recent model intercomparison studies. TOMCAT shows peak OH concentrations in the tropical lower troposphere, unlike other models which show peak concentrations in the tropical upper troposphere. This is likely to affect the lifetime and transport of important trace gases and warrants further investigation.

Pandey, A. K., A. K. Mishra, R. Kumar, S. Berwal, R. Devadas, A. Huete, and K. Kumar (2017), CO variability and its association with household cooking fuels consumption over the Indo-Gangetic Plains, Environmental Pollution, 222, 8393, doi:10.1016/j.envpol.2016.12.080.
This study examines the spatio-temporal trends obtained from decade long (Jan 2003Dec 2014) satellite observational data of Atmospheric Infrared Sounder (AIRS) and Measurements of Pollution in the Troposphere (MOPITT) on carbon monoxide (CO) concentration over the Indo-Gangetic Plains (IGP) region. The time sequence plots of columnar CO levels over the western, central and eastern IGP regions reveal marked seasonal behaviour, with lowest CO levels occurring during the monsoon months and the highest CO levels occurring during the pre-monsoon period. A negative correlation between CO levels and rainfall is observed. CO vertical profiles show relatively high values in the upper troposphere at ∼200 hPa level during the monsoon months, thus suggesting the role of convective transport and advection in addition to washout behind the decreased CO levels during this period. MOPITT and AIRS observations show a decreasing trend of 9.6 × 1015 and 1.5 × 1016 molecules cm−2 yr−1, respectively, in columnar CO levels over the IGP region. The results show the existence of a spatial gradient in CO from the eastern (higher levels) to western IGP region (lower levels). Data from the Census of India on the number of households using various cooking fuels in the IGP region shows the prevalence of biomass-fuel (i.e. firewood, crop residue, cowdung etc.) use over the eastern and central IGP regions and that of liquefied petroleum gas over the western IGP region. CO emission estimates from cooking activity over the three IGP regions are found to be in the order east &gt; central &gt; west, which support the existence of the spatial gradient in CO from eastern to the western IGP region. Our results support the intervention of present Indian government on limiting the use of biomass-fuels in domestic cooking to achieve the benefits in terms of the better air quality, household health and regional/global climate change mitigation.

Ryoo, J.-M., M. S. Johnson, L. T. Iraci, E. L. Yates, and W. Gore (2017), Investigating sources of ozone over California using AJAX airborne measurements and models: Assessing the contribution from long-range transport, Atmospheric Environment, 155, 5367, doi:10.1016/j.atmosenv.2017.02.008.
High ozone (O3) concentrations at low altitudes (1.54 km) were detected from airborne Alpha Jet Atmospheric eXperiment (AJAX) measurements on 30 May 2012 off the coast of California (CA). We investigate the causes of those elevated O3 concentrations using airborne measurements and various models. GEOS-Chem simulation shows that the contribution from local sources is likely small. A back-trajectory model was used to determine the air mass origins and how much they contributed to the O3 over CA. Low-level potential vorticity (PV) from Modern Era Retrospective analysis for Research and Applications 2 (MERRA-2) reanalysis data appears to be a result of the diabatic heating and mixing of airs in the lower altitudes, rather than be a result of direct transport from stratospheric intrusion. The Q diagnostic, which is a measure of the mixing of the air masses, indicates that there is sufficient mixing along the trajectory to indicate that O3 from the different origins is mixed and transported to the western U.S. The back-trajectory model simulation demonstrates the air masses of interest came mostly from the mid troposphere (MT, 76%), but the contribution of the lower troposphere (LT, 19%) is also significant compared to those from the upper troposphere/lower stratosphere (UT/LS, 5%). Air coming from the LT appears to be mostly originating over Asia. The possible surface impact of the high O3 transported aloft on the surface O3 concentration through vertical and horizontal transport within a few days is substantiated by the influence maps determined from the Weather Research and ForecastingStochastic Time Inverted Lagrangian Transport (WRF-STILT) model and the observed increases in surface ozone mixing ratios. Contrasting this complex case with a stratospheric-dominant event emphasizes the contribution of each source to the high O3 concentration in the lower altitudes over CA. Integrated analyses using models, reanalysis, and diagnostic tools, allows high ozone values detected by in-situ measurements to be attributed to multiple source processes.

Silva, S. J., and A. F. Arellano (2017), Characterizing Regional-Scale Combustion Using Satellite Retrievals of CO, NO2 and CO2, Remote Sensing, 9(7), 744, doi:10.3390/rs9070744.
We present joint analyses of satellite-observed combustion products to examine bulk characteristics of combustion in megacities and fire regions. We use retrievals of CO, NO2 and CO2 from NASA/Terra Measurement of Pollution In The Troposphere, NASA/Aura Ozone Monitoring Instrument, and JAXA Greenhouse Gases Observing Satellite to estimate atmospheric enhancements of these co-emitted species based on their spatiotemporal variability (spread, σ) within 14 regions dominated by combustion emissions. We find that patterns in σXCO/σXCO2 and σXCO/σXNO2 are able to distinguish between combustion types across the globe. These patterns show distinct groupings for biomass burning and the developing/developed status of a region that are not well represented in global emissions inventories. We show here that such multi-species analyses can provide constraints on emission inventories, and be useful in monitoring trends and understanding regional-scale combustion.

Sitnov, S. A., I. I. Mokhov, and A. V. Dzhola (2017), Total content of carbon monoxide in the atmosphere over Russian regions according to satellite data, Izvestiya, Atmospheric and Oceanic Physics, 1(53), 3248, doi:10.1134/S0001433817010121.
Carbon monoxide (CO) total columns over European Russia (ER) and western Siberia (WS) have been analyzed using MOPITT (V5, TIR/NIR, L3) IR-radiometer data obtained in 20002014. High CO contents are revealed over large urban and industrial agglomerations and over regions of oil-and-gas production. A stable local CO maximum is observed over the Moscow agglomeration. Statistical characteristics of CO total columns observed in the atmosphere over ER and WS in 20002014 are presented. An analysis of long-term changes in CO content reveals nonlinear changes in the CO total column over northern Eurasia in 20002014. Results of a comparative analysis of annual variations in atmospheric CO contents over ER and WS are given. Based on Fourier analysis, empirical models of annual variations in total CO contents over ER and WS are proposed. Relations between regional CO contents and fire characteristics and between spatial CO distributions and features of large-scale atmospheric dynamics under conditions of weather and climate anomalies in the summers of 2010 in ER and 2012 in WS are analyzed. Data on total CO contents measured with a MOPITT satellite radiometer and a ground-based spectrometer operating at the Zvenigorod Scientific Station of the Obukhov Institute of Atmospheric Physics are compared.

Sun, YuTao, GUO ZhengFu, CHENG ZhiHui, ZHANG MaoLiang, and ZHANG LiHong (2017), Gaseous anomalies related to the activities of Changbai Volcano in 2002 ~ 2005 : Evidence from multi-sensor hyperspatial satellite archived data, Acta Petrologica Sinica, 33(1). [online] Available from:
The Changbai Mountain volcanic area is an active volcano with potential eruption in China. In 2002-2005, volcanic activity increased and magma chamber disturbances appeared. The use of satellite remote sensing technology has the advantages of large observation range, long observation time and continuous observation. Therefore, this article The tropospheric pollution detector (MOPITT) and atmospheric infrared detector (AIRS) hyperspectral remote sensing data were used to extract total CO, O3, total water vapor, and surface temperature anomalies in the Tianchi volcanic area of Changbai Mountain from 2002 to 2005. Spectrum remote sensing gas geochemistry ... view all >> view all >>: The Changbai Mountain volcanic area is an active volcano with potential eruption in China. The volcanic activity increased in 2002 and magma disturbance occurred. The use of satellite remote sensing technology has the advantages of large observation range, long and continuous observation time. Therefore, this article uses The Tropospheric Pollution Detector (MOPITT) and Atmospheric Infrared Detector (AIRS) hyperspectral remote sensing data extracted the total CO, O3, total water vapor, and surface temperature anomalies from the Tianchi volcanic area of ​​Changbai Mountain from 2002 to 2005. The relationship between remote sensing gas geochemical anomaly information and volcanic activity, and the volcanic activity in the Tianchi volcanic area of ​​Changbai Mountain from 2002 to 2005 was studied. The results show that the gas geochemical (CO, O3, The water vapor anomaly is consistent with the results of earthquake, deformation monitoring and surface fluid (CO2, He, H2) observations, indicating that the gas anomaly changes observed by MOPITT and AIRS hyperspectral remote sensing satellites better reflect the large-scale Deep magma local disturbances. During volcanic activity from 2002 to 2005, total CO, O3, water vapor, and surface temperature all showed significant changes. Anomalies and the corresponding quasi-deviations during the occurrence of the anomaly significantly increase, reflecting the heterogeneity of the gas selection in time, which may be related to the role and change of geostress during volcanic and seismic activities. Comprehensive analysis of ground observation results shows that the magma chamber disturbance did not produce a long-term rise and migration of the mantle material flow from 2002 to 2005. During the period of enhanced volcanic activity, the surface temperature showed abnormally low values, which may be related to the subduction of the Pacific plate. The tension induced by the fault during the process is enhanced. In addition, the gas selected during the volcanic activity enters the atmosphere to generate an atmospheric chemical reaction, which will also cause the gas geochemical anomaly observed by hyperspectral remote sensing. The research results are from Changbai Mountain from 2002 to 2005 The study of volcanic activity provides new evidence for gas geochemistry from hyperspectral remote sensing data, and also has certain significance for the study of volcanic activity laws and the application of volcanic monitoring by hyperspectral resolution remote sensing data.

Tang, W., and A. F. Arellano (2017), Investigating dominant characteristics of fires across the Amazon during 20052014 through satellite data synthesis of combustion signatures, Journal of Geophysical Research: Atmospheres, 122(2), 12241245, doi:10.1002/2016JD025216.
Estimates of fire emissions remain uncertain due to limited constraints on the variations in fire characteristics. Here we demonstrate the utility of space-based observations of smoke constituents in addressing this limitation. We introduce a satellite-derived smoke index (SI) as an indicator of the dominant phase of large-scale fires. This index is calculated as the ratio of the geometric mean of observed fractional enhancements (due to fire) in carbon monoxide and aerosol optical depth to that of nitrogen dioxide. We assess the usefulness of this index on fires in the Amazon. We analyze the seasonal, regional, and interannual joint distribution of SI and fire radiative power (FRP) in relation to fire hotspots, land cover, Drought Severity Index, and deforestation rate estimates. We also compare this index with an analogous quantity derived from field data or emission inventories. Our results show that SI changes from low (more flaming) to high (more smoldering) during the course of a fire season, which is consistent with the changes in observed maximum FRPs from high to low. We also find that flaming combustion is more dominant in areas where deforestation fires dominate, while smoldering combustion has a larger influence during drought years when understory fires are more likely enhanced. Lastly, we find that the spatiotemporal variation in SI is inconsistent with current emission inventories. Although we recognize some limitations of this approach, our results point to the utility of SI as a proxy for overall combustion efficiency in the parameterization of fire emission models.

Tratt, D. M., S. J. Young, J. A. Hackwell, D. J. Rudy, D. W. Warren, A. G. Vore, and P. D. Johnson (2017), MAHI: An Airborne Mid-Infrared Imaging Spectrometer for Industrial Emissions Monitoring, IEEE Transactions on Geoscience and Remote Sensing, 55(8), 45584566, doi:10.1109/TGRS.2017.2693979.
An airborne hyperspectral imager operating in the midwave-infrared spectral range is described. The Mid-infrared Airborne Hyperspectral Imager (MAHI) features 3.3-nm spectral sampling over its 3.3-5.4 μm wavelength range. MAHI operates in a roll-stabilized pushbroom configuration with 480 crosstrack pixels, each with an instantaneous field-of-view (IFOV) of 0.94 mrad, to provide for a total FOV of 25.8°. The sensor spectroradiometric performance is illustrated by case studies featuring the detection, identification, and quantification of a number of fugitive gaseous emissions from industrial sources.

Verma, N., A. Satsangi, A. Lakhani, K. M. Kumari, and S. Lal (2017), Diurnal, Seasonal, and Vertical Variability in Carbon Monoxide Levels at a Semi-Urban Site in India, Clean Soil Air Water, n/a-n/a, doi:10.1002/clen.201600432.
In the present study, near-surface carbon monoxide (CO) measurements were carried out at a semi-urban site in Agra, India (27°10′N, 78°05′E), during March 2015 to February 2016. The study includes the diurnal, seasonal, and vertical variation of CO and the effect of meteorological parameters on its levels. The diurnal variation of CO was characterized by high levels during morning (910 am) and evening (1011 pm) hours and low levels during the afternoon (35 pm). The morning and evening peak levels may be due to high emissions from traffic and low planetary boundary layer (PBL) height which prevents dispersion of pollutants. The low levels during afternoon hours may be due to increasing PBL height and loss through photochemical reactions. CO showed a distinct seasonal variation with highest levels in winter (770 ± 466 ppb) and lowest in monsoon (153 ± 122 ppb). The high levels in the winter season may be attributed to increased emissions from coal and wood burning used for heating in combination with stagnant weather conditions. The study also included latest retrievals of CO using Measurements of Pollution in the Troposphere (MOPITT) to define the vertical and seasonal variation of CO. The pattern of seasonal variation observed by ground level measurements was consistent with MOPITT surface CO levels.

Worden, J. R., A. A. Bloom, S. Pandey, Z. Jiang, H. M. Worden, T. W. Walker, S. Houweling, and T. Rockmann (2017), Reduced biomass burning emissions reconcile conflicting estimates of the post-2006 atmospheric methane budget, Nat. Commun., 8, 2227, doi:10.1038/s41467-017-02246-0.
Several viable but conflicting explanations have been proposed to explain the recent similar to 8 p.p.b. per year increase in atmospheric methane after 2006, equivalent to net emissions increase of similar to 25 Tg CH4 per year. A concurrent increase in atmospheric ethane implicates a fossil source; a concurrent decrease in the heavy isotope content of methane points toward a biogenic source, while other studies propose a decrease in the chemical sink (OH). Here we show that biomass burning emissions of methane decreased by 3.7 (+/- 1.4) Tg CH4 per year from the 2001-2007 to the 2008-2014 time periods using satellite measurements of CO and CH4, nearly twice the decrease expected from prior estimates. After updating both the total and isotopic budgets for atmospheric methane with these revised biomass burning emissions (and assuming no change to the chemical sink), we find that fossil fuels contribute between 12-19 Tg CH4 per year to the recent atmospheric methane increase, thus reconciling the isotopic-and ethane-based results.

Yahya, K., K. Wang, P. Campbell, Y. Chen, T. Glotfelty, J. He, M. Pirhalla, and Y. Zhang (2017), Decadal application of WRF/Chem for regional air quality and climate modeling over the U.S. under the representative concentration pathways scenarios. Part 1: Model evaluation and impact of downscaling, Atmospheric Environment, 152, 562583, doi:10.1016/j.atmosenv.2016.12.029.
An advanced online-coupled meteorology-chemistry model, i.e., the Weather Research and Forecasting Model with Chemistry (WRF/Chem), is applied for current (20012010) and future (20462055) decades under the representative concentration pathways (RCP) 4.5 and 8.5 scenarios to examine changes in future climate, air quality, and their interactions. In this Part I paper, a comprehensive model evaluation is carried out for current decade to assess the performance of WRF/Chem and WRF under both scenarios and the benefits of downscaling the North Carolina State University’s (NCSU) version of the Community Earth System Model (CESM_NCSU) using WRF/Chem. The evaluation of WRF/Chem shows an overall good performance for most meteorological and chemical variables on a decadal scale. Temperature at 2-m is overpredicted by WRF (by ∼0.20.3 °C) but underpredicted by WRF/Chem (by ∼0.30.4 °C), due to higher radiation from WRF. Both WRF and WRF/Chem show large overpredictions for precipitation, indicating limitations in their microphysics or convective parameterizations. WRF/Chem with prognostic chemical concentrations, however, performs much better than WRF with prescribed chemical concentrations for radiation variables, illustrating the benefit of predicting gases and aerosols and representing their feedbacks into meteorology in WRF/Chem. WRF/Chem performs much better than CESM_NCSU for most surface meteorological variables and O3 hourly mixing ratios. In addition, WRF/Chem better captures observed temporal and spatial variations than CESM_NCSU. CESM_NCSU performance for radiation variables is comparable to or better than WRF/Chem performance because of the model tuning in CESM_NCSU that is routinely made in global models.

Yarragunta, Y., S. Srivastava, and D. Mitra (2017), Validation of lower tropospheric carbon monoxide inferred from MOZART model simulation over India, Atmospheric Research, 184, 3547, doi:10.1016/j.atmosres.2016.09.010.
In the present study, MOZART-4 (Model for Ozone and Related chemical Tracers-Version-4) simulation has been made from 2003 to 2007 and compared with satellite and in-situ observations with a specific focus on Indian subcontinent to illustrate the capabilities of MOZART-4 model. The model simulated CO have been compared with latest version (version-6) of MOPITT (Measurement Of Pollution In The Troposphere) carbon monoxide (CO) retrievals at 900, 800 and 700 hPa. Model reproduces major features present in satellite observations. However model significantly overestimates CO over the entire Indian region at 900 hPa and moderately overestimates at 800 hPa and 700 hPa. The frequency distribution of all simulated data points with respect to MOZART error shows maximum in the error range of 1020% at all pressure levels. Over total Indian landmass, the percentage of gridded CO data that are being overestimated in the range of 030% at 900 hPa, 800 hPa and 700 hPa are 58%, 62% and 66% respectively. The study reflects very good correlation between two datasets over Central India (CI) and Southern India (SI). The coefficient of determination (r2) is found to be 0.680.78 and 0.700.78 over the CI and SI respectively. The weak correlation is evident over Northern India (NI) with r2 values of 0.10.3. Over Eastern India (EI), Good correlation at 800 hPa (r2 = 0.72) and 700 hPa (r2 = 0.66) whereas moderately weak correlation at 900 hPa (r2 = 0.48) has been observed. In contrast, Over Western India (WI), strong correlation is evident at 900 hPa (r2 = 0.64) and moderately weak association is found to be present at 800 hPa and 700 hPa. Model fairly reproduces seasonal cycle of CO in the lower troposphere over most of the Indian regions. However, during June to December, model shows overestimation over NI. The magnitude of overestimation is increasing linearly from 900 hPa to 700 hPa level. During AprilJune months, model results are coinciding with observed CO concentrations over SI region at 900 hPa. Model simulation has been compared with surface in-situ observations over ten Indian locations. Model performance is found to be moderate to good over various observational locations. However, over highly polluted megacities, model underestimates observed CO concentration by up to 3500 ppbv. A case study over the forest fire prone area reveals the clear increase of modeled and retrieved CO in FebruaryMarch and a decrease in May which is coinciding with biomass burning emissions and fire counts. Model performance is found to be relatively poor over this region with r2 of 0.29 and slope of 0.56.

Zhang, X., D. B. A. Jones, M. Keller, Z. Jiang, A. E. Bourassa, D. A. Degenstein, C. Clerbaux, and P.-F. Coheur (2017), Global CO emission estimates inferred from assimilation of MOPITT and IASI CO data, together with observations of O3, NO2, HNO3, and HCHO. [online] Available from: .
Atmospheric carbon monoxide (CO) emissions estimated from inverse modeling analyses exhibit large uncertainties, due, in part, to discrepancies in the tropospheric chemistry in atmospheric models. We attempt to reduce the uncertainties in CO emission estimates by constraining the modeled abundance of ozone (O3), nitrogen dioxide (NO2), nitric acid (HNO3), and formaldehyde (HCHO), which are constituents that play a key role in tropospheric chemistry. Using the GEOS-Chem four-dimensional variational (4D-Var) data assimilation system, we estimate CO emissions by assimilating observations of CO from the Measurement of Pollution In the Troposphere (MOPITT) and the Infrared Atmospheric Sounding Interferometer (IASI), together with observations of O3 from the Optical Spectrograph and InfraRed Imager System (OSIRIS) and IASI, NO2 and HCHO from the Ozone Monitoring Instrument (OMI), and HNO3 from the Microwave Limb Sounder (MLS). Our experiments evaluate the inferred CO emission estimates from major anthropogenic, biomass burning and biogenic sources. Moreover, we also infer surface emissions of nitrogen oxides (NOx = NO + NO2) and isoprene. Our results reveal that this multiple species chemical data assimilation produces a chemical consistent state that effectively adjusts the CO-O3-OH coupling in the model. The O3-induced changes in OH are particularly large in the tropics. Overall, our analysis results in a better constrained tropospheric chemical state.

Zhou, Y., H. Mao, K. Demerjian, C. Hogrefe, and J. Liu (2017), Regional and hemispheric influences on temporal variability in baseline carbon monoxide and ozone over the Northeast US, Atmospheric Environment, 164, 309324, doi:10.1016/j.atmosenv.2017.06.017.
Interannual variability in baseline carbon monoxide (CO) and ozone (O3), defined as mixing ratios under minimal influence of recent and local emissions, was studied for seven rural sites in the Northeast US over 20012010. Annual baseline CO exhibited statistically significant decreasing trends (−4.3 to −2.3 ppbv yr−1), while baseline O3 did not display trends at any site. In examining the data by season, wintertime and springtime baseline CO at the two highest sites (1.5 km and 2 km asl) did not experience significant trends. Decadal increasing trends (∼2.55 ppbv yr−1) were found in springtime and wintertime baseline O3 in southern New Hampshire, which was associated with anthropogenic NOx emission reductions from the urban corridor. Biomass burning emissions impacted summertime baseline CO with ∼38% variability from wildfire emissions in Russia and ∼22% from Canada at five sites and impacted baseline O3 at the two high elevation sites only with ∼27% variability from wildfires in both Russia and Canada. The Arctic Oscillation was negatively correlated with summertime baseline O3, while the North Atlantic Oscillation was positively correlated with springtime baseline O3. This study suggested that anthropogenic and biomass burning emissions, and meteorological conditions were important factors working together to determine baseline O3 and CO in the Northeast U.S. during the 2000s.


Azmi, U., and M. Marzuki (2016), Distribusi Vertikal Karbon Monoksida di Sumatera Berdasarkan Pengamatan Measurement of Pollution in the Troposphere (MOPITT) Selama Kebakaran Hutan Tahun 2015, Jurnal Fisika Unand, 5(3), 252260.
Distribusi vertikal karbon monoksida (CO) di Sumatera selama kebakaran hutan tahun 2015 telah diteliti menggunakan data satelit MOPITT (Measurements of Pollution in the Troposphere). Pengaruh proses konveksi terhadap pergerakan CO ke lapisan atmosfer diamati dengan data OLR (Outgoing Longwave Radiation) dan pergerakan udara dari data NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research). Hasil penelitian memperlihatkan bahwa kebakaran hutan tahun 2015 telah meningkatkan konsentrasi CO di Indonesia. Namun, jumlah gas CO yang terekam oleh MOPITT tidak terlalu tinggi (~40-120 ppbv). Hal ini disebabkan oleh tingginya konsentrasi uap air di ekuator sehingga konsentrasi CO rendah dan waktu tinggal CO di atmosfer juga berkurang. Selain di permukaan, peningkatan konsentrasi CO juga teramati pada lapisan atmosfer yang lebih tinggi. Namun, hubungan antara pergerakan CO ke lapisan atmosfer atas dengan aktivitas konveksi sulit untuk diamati dengan data satelit MOPITT. Perulangan waktu pengamatan MOPITT untuk titik pengamatan yang sama cukup lama yaitu 4 hari menjadi salah satu kendala. Walaupun demikian, dari tiga studi kasus yang diteliti, teramati pengaruh konveksi terhadap pergerakan CO ke atas pada dua kasus yaitu tanggal 11 dan 15 Oktober 2015. Pada 11 Oktober, jumlah CO bertambah dari 60 ppbv menuju 80-100 ppbv dan pada tanggal 15 Oktober, juga mengalami peningkatan dari 60 ppbv menjadi 80-90 ppbv pada 100 hPa.Kata kunci:CO, MOPITT, konveksi, Sumatera, kebakaran hutan 2015

Borsdorff, T., P. Tol, J. E. Williams, J. de Laat, J. aan de Brugh, P. Nedelec, I. Aben, and J. Landgraf (2016), Carbon monoxide total columns from SCIAMACHY 2.3 mu m atmospheric reflectance measurements: towards a full-mission data product (2003-2012), Atmos. Meas. Tech., 9(1), 227248, doi:10.5194/amt-9-227-2016.
We present a full-mission data product of carbon monoxide ( CO) vertical column densities using the 2310-2338 nm SCIAMACHY reflectance measurements over clear-sky land scenes for the period January 2003-April 2012. The retrieval employs the SICOR algorithm, which will be used for operational data processing of the Sentinel-5 Precursor mission. The retrieval approach infers simultaneously carbon monoxide, methane and water vapour column densities together with a Lambertian surface albedo from individual SCIAMACHY measurements employing a non-scattering radiative transfer model. To account for the radiometric instrument degradation including the formation of an ice-layer on the 2.3 mu m detector array, we consider clear-sky measurements over the Sahara as a natural calibration target. For these specific measurements, we spectrally calibrate the SCIAMACHY measurements and determine a spectral radiometric offset and the width of the instrument spectral response function as a function of time for the entire operational phase of the mission. We show that the smoothing error of individual clear-sky CO retrievals is less than +/- 1 ppb and thus this error contribution does not need to be accounted for in the validation considering the much higher retrieval noise. The CO data product is validated against measurements of ground-based Fourier transform infrared spectrometers at 27 stations of the NDACC-IRWG and TCCON network and MOZAIC/IAGOS aircraft measurements at 26 airports worldwide. Overall, we find a good agreement with TCCON measurements with a mean bias N (b) over bar = -1.2 ppb and a station-to-station bias with (sigma) over bar = 7.2 ppb. The negative sign of the bias means a low bias of SCIAMACHY CO with respect to TCCON. For the NDACC-IRWG network, we obtain a larger mean station bias of N (b) over bar = -92 ppb with (sigma) over bar = 8.1 ppb and for the MOZAIC/IAGOS measurements we find (b) over bar = -6.4 ppb with (sigma) over bar = 5.6 ppb. The SCIAMACHY data set is subject to a small but significant bias trend of 1.47 +/- 0.25 ppbyr(-1). After trend correction, the bias with respect to MOZAIC/IAGOS observation is 2.5 ppb, with respect to TCCON measurements it is -4.6 ppb and with respect to NDACC-IRWG measurements -8.4 ppb. Hence, a discrepancy of 3.8 ppb remains between the global biases with NDACC-IRWG and TCCON, which is confirmed by directly comparing NDACC-IRWG and TCCON measurements. Generally, the scatter of the individual SCIAMACHY CO retrievals is high and dominated by large measurement noise. Hence, for practical usage of the data set, averaging of individual retrievals is required. As an example, we show that monthly mean SCIAMACHY CO retrievals, averaged separately over Northern and Southern Africa, reflect the spatial and temporal variability of biomass burning events in agreement with the global chemical transport model TM5.

Cai, C., X. Zhang, K. Wang, Y. Zhang, L. Wang, Q. Zhang, F. Duan, K. He, and S.-C. Yu (2016), Incorporation of new particle formation and early growth treatments into WRF/Chem: Model improvement, evaluation, and impacts of anthropogenic aerosols over East Asia, Atmospheric Environment, 124, Part B, 262284, doi:10.1016/j.atmosenv.2015.05.046.
New particle formation (NPF) provides an important source of aerosol particles and cloud condensation nuclei, which may result in enhanced cloud droplet number concentration (CDNC) and cloud shortwave albedo. In this work, several nucleation parameterizations and one particle early growth parameterization are implemented into the online-coupled Weather Research and Forecasting model coupled with chemistry (WRF/Chem) to improve the model’s capability in simulating NPF and early growth of ultrafine particles over East Asia. The default 8-bin over the size range of 39 nm10 μm used in the Model for Simulating Aerosol Interactions and Chemistry aerosol module is expanded to the 12-bin over 1 nm10 μm to explicitly track the formation and evolution of new particles. Although model biases remain in simulating H2SO4, condensation sink, growth rate, and formation rate, the evaluation of July 2008 simulation identifies a combination of three nucleation parameterizations (i.e., COMB) that can best represent the atmospheric nucleation processes in terms of both surface nucleation events and the resulting vertical distribution of ultrafine particle concentrations. COMB consists of a power law of Wang et al. (2011) based on activation theory for urban areas in planetary boundary layer (PBL), a power law of Boy et al. (2008) based on activation theory for non-urban areas in PBL, and the ion-mediated nucleation parameterization of YU10 for above PBL. The application and evaluation of the improved model with 12-bin and the COMB nucleation parameterization in East Asia during January, April, July, and October in 2001 show that the model has an overall reasonably good skill in reproducing most observed meteorological variables and surface and column chemical concentrations. Relatively large biases in simulated precipitation and wind speeds are due to inaccurate surface roughness and limitations in model treatments of cloud formation and aerosol-cloud-precipitation interactions. Large biases in the simulated surface concentrations of PM10, NOx, CO, SO2, and VOCs at some sites are due in part to possible underestimations of emissions and in part to inaccurate meteorological predictions. The simulations of 2001 show that anthropogenic aerosols can increase aerosol optical depth by 64.0228.3%, CDNC by 40.276.4%, and cloud optical thickness by 14.325.3%; they can reduce surface net shortwave radiation by up to 42.552.8 W m−2, 2-m temperature by up to 0.340.83 °C, and PBL height by up to 76.8125.9 m. Such effects are more significant than those previously reported for the U.S. and Europe.

Chandra, N., S. Venkataramani, S. Lal, V. Sheel, and A. Pozzer (2016), Effects of convection and long-range transport on the distribution of carbon monoxide in the troposphere over India, Atmospheric Pollution Research, 7(5), 775785, doi:10.1016/j.apr.2016.03.005.
Variability in the tropospheric distributions of carbon monoxide (CO) over five selected regions of India has been studied using the MOPITT data for the period of 20012014. The average seasonal profiles show highest mixing ratios at 900 hPa in the boreal winter and lowest in the Indian summer monsoon over all the study regions. We observe a slight increase in CO levels from 500 hPa to 200 hPa over all the locations. The CO mixing ratios are found to be higher by about 1040% around 300200 hPa as compared to 900 hPa over Ahmedabad, Hyderabad and Trivandrum during monsoon period. This could be due to lifting of polluted air by convection and getting trapped in the anticyclonic winds over the Indian region during the monsoon. Most of the 7 day back trajectories over these regions show transport of the polluted air mass from the major biomass burning regions of central Africa and SE Asia. The results show dominance of the seasonal amplitude at 900 hPa over all the regions, while inter-annual variability dominates mostly over Ahmedabad, Hyderabad and Trivandrum at 300 hPa. In order to check the ability of different models in capturing the observed variability, the results have been compared with simulations from two chemistry transport models (MOZART and EMAC). This comparison shows that both the models perform reasonably well in simulating the basic features such as annual variation as well as increase in CO around 300200 hPa due to convection during the monsoon season.

Deeter, M. N., S. Martínez-Alonso, L. V. Gatti, M. Gloor, J. B. Miller, L. G. Domingues, and C. S. C. Correia (2016), Validation and analysis of MOPITT CO observations of the Amazon Basin, Atmos. Meas. Tech., 9(8), 39994012, doi:10.5194/amt-9-3999-2016.
We analyze satellite retrievals of carbon monoxide from the MOPITT (Measurements of Pollution in the Troposphere) instrument over the Amazon Basin, focusing on the MOPITT Version 6 “multispectral” retrieval product (exploiting both thermal-infrared and near-infrared channels). Validation results based on in situ vertical profiles measured between 2010 and 2013 are presented for four sites in the Amazon Basin. Results indicate a significant negative bias in retrieved lower-tropospheric CO concentrations. The possible influence of smoke aerosol as a source of retrieval bias is investigated using collocated Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) measurements at two sites but does not appear to be significant. Finally, we exploit the MOPITT record to analyze both the mean annual cycle and the interannual variability of CO over the Amazon Basin since 2002.

Elshorbany, Y. F., B. N. Duncan, S. A. Strode, J. S. Wang, and J. Kouatchou (2016), The description and validation of the computationally Efficient CH4COOH (ECCOHv1.01) chemistry module for 3-D model applications, Geoscientific Model Development, 9(2), 799822, doi:

Abstract. We present the Efficient CH4COOH (ECCOH) chemistry module that allows for the simulation of the methane, carbon monoxide, and hydroxyl radical (CH4COOH) system, within a chemistry climate model, carbon cycle model, or Earth system model. The computational efficiency of the module allows many multi-decadal sensitivity simulations of the CH4COOH system, which primarily determines the global atmospheric oxidizing capacity. This capability is important for capturing the nonlinear feedbacks of the CH4COOH system and understanding the perturbations to methane, CO, and OH, and the concomitant impacts on climate. We implemented the ECCOH chemistry module in the NASA GEOS-5 atmospheric global circulation model (AGCM), performed multiple sensitivity simulations of the CH4COOH system over 2 decades, and evaluated the model output with surface and satellite data sets of methane and CO. The favorable comparison of output from the ECCOH chemistry module (as configured in the GEOS-5 AGCM) with observations demonstrates the fidelity of the module for use in scientific research.

Field, R. D., G. R. van der Werf, T. Fanin, E. J. Fetzer, R. Fuller, H. Jethva, R. Levy, N. J. Livesey, M. Luo, O. Torres, and H. M. Worden (2016), Indonesian fire activity and smoke pollution in 2015 show persistent nonlinear sensitivity to El Nino-induced drought, Proc. Natl. Acad. Sci. U. S. A., 113(33), 92049209, doi:10.1073/pnas.1524888113.
The 2015 fire season and related smoke pollution in Indonesia was more severe than the major 2006 episode, making it the most severe season observed by the NASA Earth Observing System satellites that go back to the early 2000s, namely active fire detections from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS), MODIS aerosol optical depth, Terra Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO), Aqua Atmospheric Infrared Sounder (AIRS) CO, Aura Ozone Monitoring Instrument (OMI) aerosol index, and Aura Microwave Limb Sounder (MLS) CO. The MLS CO in the upper troposphere showed a plume of pollution stretching from East Africa to the western Pacific Ocean that persisted for 2 mo. Longer-term records of airport visibility in Sumatra and Kalimantan show that 2015 ranked after 1997 and alongside 1991 and 1994 as among the worst episodes on record. Analysis of yearly dry season rainfall from the Tropical Rainfall Measurement Mission (TRMM) and rain gauges shows that, due to the continued use of fire to clear and prepare land on degraded peat, the Indonesian fire environment continues to have nonlinear sensitivity to dry conditions during prolonged periods with less than 4 mm/d of precipitation, and this sensitivity appears to have increased over Kalimantan. Without significant reforms in land use and the adoption of early warning triggers tied to precipitation forecasts, these intense fire episodes will reoccur during future droughts, usually associated with El Nino events.

Fu, D., K. W. Bowman, H. M. Worden, V. Natraj, J. R. Worden, S. Yu, P. Veefkind, I. Aben, J. Landgraf, L. Strow, and Y. Han (2016), High-resolution tropospheric carbon monoxide profiles retrieved from CrIS and TROPOMI, Atmos. Meas. Tech., 9(6), 25672579, doi:10.5194/amt-9-2567-2016.
The Measurements of Pollution in the Troposphere (MOPITT) instrument is the only satellite-borne sensor in operation that uses both thermal (TIR) and near-infrared (NIR) channels to estimate CO profiles. With more than 15 years (2000 to present) of validated multispectral observations, MOPITT provides the unique capability to separate CO in the lowermost troposphere (LMT, surface to 3 km (similar to 700 hPa)) from the free-tropospheric abundance. To extend this record, a new, hyper-spectral approach is presented here that will provide CO data products exceeding the capabilities of MOPITT by combining the short-wavelength infrared (SWIR, equivalent to the MOPITT NIR) channels from the TROPOspheric Monitoring Instrument (TROPOMI) to be launched aboard the European Sentinel 5 Precursor (S5p) satellite in 2016 and the TIR channels from the Cross-track Infrared Sounder (CrIS) aboard the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite. We apply the MUlti-SpEctra, MUlti-SpEcies, Multi-SEnsors (MUSES) retrieval algorithm to quantify the potential of this joint CO product. CO profiles are retrieved from a single-footprint, full-spectral-resolution CrIS transect over Africa on 27-28 August 2013 coincident with significant biomass burning. Comparisons of collocated CrIS and MOPITT CO observations for the LMT show a mean difference of 2.8 +/- 24.9 ppb, which is well within the estimated measurement uncertainty of both sensors. The estimated degrees of freedom (DOF) for CO signals from synergistic CrIS-TROPOMI retrievals are approximately 0.9 in the LMT and 1.3 above the LMT, which indicates that the LMT CO can be distinguished from the free troposphere, similar to MOPITT multispectral observations (0.8 in the LMT, and 1.1 above the LMT). In addition to increased sensitivity, the combined retrievals reduce measurement uncertainty, with similar to 15% error reduction in the LMT. With a daily global coverage and a combined spatial footprint of 14 km, the joint CrIS-TROPOMI measurements have the potential to extend and improve upon the MOPITT multispectral CO data records for the coming decade.

Gaubert, B., A. F. Arellano, J. Barré, H. M. Worden, L. K. Emmons, S. Tilmes, R. R. Buchholz, F. Vitt, K. Raeder, N. Collins, J. L. Anderson, C. Wiedinmyer, S. Martinez Alonso, D. P. Edwards, M. O. Andreae, J. W. Hannigan, C. Petri, K. Strong, and N. Jones (2016), Toward a chemical reanalysis in a coupled chemistry-climate model: An evaluation of MOPITT CO assimilation and its impact on tropospheric composition, J. Geophys. Res. Atmos., 121(12), 2016JD024863, doi:10.1002/2016JD024863.
We examine in detail a 1 year global reanalysis of carbon monoxide (CO) that is based on joint assimilation of conventional meteorological observations and Measurement of Pollution in The Troposphere (MOPITT) multispectral CO retrievals in the Community Earth System Model (CESM). Our focus is to assess the impact to the chemical system when CO distribution is constrained in a coupled full chemistry-climate model like CESM. To do this, we first evaluate the joint reanalysis (MOPITT Reanalysis) against four sets of independent observations and compare its performance against a reanalysis with no MOPITT assimilation (Control Run). We then investigate the CO burden and chemical response with the aid of tagged sectoral CO tracers. We estimate the total tropospheric CO burden in 2002 (from ensemble mean and spread) to be 371 ± 12% Tg for MOPITT Reanalysis and 291 ± 9% Tg for Control Run. Our multispecies analysis of this difference suggests that (a) direct emissions of CO and hydrocarbons are too low in the inventory used in this study and (b) chemical oxidation, transport, and deposition processes are not accurately and consistently represented in the model. Increases in CO led to net reduction of OH and subsequent longer lifetime of CH4 (Control Run: 8.7 years versus MOPITT Reanalysis: 9.3 years). Yet at the same time, this increase led to 510% enhancement of Northern Hemisphere O3 and overall photochemical activity via HOx recycling. Such nonlinear effects further complicate the attribution to uncertainties in direct emissions alone. This has implications to chemistry-climate modeling and inversion studies of longer-lived species.

Glotfelty, T., Y. Zhang, P. Karamchandani, and D. G. Streets (2016), Changes in future air quality, deposition, and aerosol-cloud interactions under future climate and emission scenarios, Atmospheric Environment, 139, 176191, doi:10.1016/j.atmosenv.2016.05.008.
The prospect of global climate change will have wide scale impacts, such as ecological stress and human health hazards. One aspect of concern is future changes in air quality that will result from changes in both meteorological forcing and air pollutant emissions. In this study, the GU-WRF/Chem model is employed to simulate the impact of changing climate and emissions following the IPCC AR4 SRES A1B scenario. An average of 4 future years (2020, 2030, 2040, and 2050) is compared against an average of 2 current years (2001 and 2010). Under this scenario, by the Mid-21st century global air quality is projected to degrade with a global average increase of 2.5 ppb in the maximum 8-hr O3 level and of 0.3 μg m−3 in 24-hr average PM2.5. However, PM2.5 changes are more regional due to regional variations in primary aerosol emissions and emissions of gaseous precursor for secondary PM2.5. Increasing NOx emissions in this scenario combines with a wetter climate elevating levels of OH, HO2, H2O2, and the nitrate radical and increasing the atmosphere’s near surface oxidation state. This differs from findings under the RCP scenarios that experience declines in OH from reduced NOx emissions, stratospheric recovery of O3, and increases in CH4 and VOCs. Increasing NOx and O3 levels enhances the nitrogen and O3 deposition, indicating potentially enhanced crop damage and ecosystem stress under this scenario. The enhanced global aerosol level results in enhancements in aerosol optical depth, cloud droplet number concentration, and cloud optical thickness. This leads to dimming at the Earth’s surface with a global average reduction in shortwave radiation of 1.2 W m−2. This enhanced dimming leads to a more moderate warming trend and different trends in radiation than those found in NCAR’s CCSM simulation, which does not include the advanced chemistry and aerosol treatment of GU-WRF/Chem and cannot simulate the impacts of changing climate and emissions with the same level of detailed treatments. This study indicates that effective climate mitigation and emission control strategies are needed to prevent future health impact and ecosystem stress. Further, studies that are used to develop these strategies should use fully coupled models with sophisticated chemical and aerosol-interaction treatments that can provide a more realistic representation of the atmosphere.

Hoshyaripour, G., G. Brasseur, M. F. Andrade, M. Gavidia-Calderón, I. Bouarar, and R. Y. Ynoue (2016), Prediction of ground-level ozone concentration in São Paulo, Brazil: Deterministic versus statistic models, Atmospheric Environment, 145, 365375, doi:10.1016/j.atmosenv.2016.09.061.
Two state-of-the-art models (deterministic: Weather Research and Forecast model with Chemistry (WRF-Chem) and statistic: Artificial Neural Networks: (ANN)) are implemented to predict the ground-level ozone concentration in São Paulo (SP), Brazil. Two domains are set up for WRF-Chem simulations: a coarse domain (with 50 km horizontal resolution) including whole South America (D1) and a nested domain (with horizontal resolution of 10 km) including South Eastern Brazil (D2). To evaluate the spatial distribution of the chemical species, model results are compared to the Measurements of Pollution in The Troposphere (MOPITT) data, showing that the model satisfactorily predicts the CO concentrations in both D1 and D2. The model also reproduces the measurements made at three air quality monitoring stations in SP with the correlation coefficients of 0.74, 0.70, and 0.77 for O3 and 0.51, 0.48, and 0.57 for NOx. The input selection for ANN model is carried out using Forward Selection (FS) method. FS-ANN is then trained and validated using the data from two air quality monitoring stations, showing correlation coefficients of 0.84 and 0.75 for daily mean and 0.64 and 0.67 for daily peak ozone during the test stage. Then, both WRF-Chem and FS-ANN are deployed to forecast the daily mean and peak concentrations of ozone in two stations during 520 August 2012. Results show that WRF-Chem preforms better in predicting mean and peak ozone concentrations as well as in conducting mechanistic and sensitivity analysis. FS-ANN is only advantageous in predicting mean daily ozone concentrations considering its significantly lower computational costs and ease of development and implementation, compared to that of WRF-Chem.

Huijnen, V., M. J. Wooster, J. W. Kaiser, D. L. A. Gaveau, J. Flemming, M. Parrington, A. Inness, D. Murdiyarso, B. Main, and M. van Weele (2016), Fire carbon emissions over maritime southeast Asia in 2015 largest since 1997, Scientific Reports, 6, srep26886, doi:10.1038/srep26886.
In September and October 2015 widespread forest and peatland fires burned over large parts of maritime southeast Asia, most notably Indonesia, releasing large amounts of terrestrially-stored carbon into the atmosphere, primarily in the form of CO2, CO and CH4. With a mean emission rate of 11.3 Tg CO2 per day during Sept-Oct 2015, emissions from these fires exceeded the fossil fuel CO2 release rate of the European Union (EU28) (8.9 Tg CO2 per day). Although seasonal fires are a frequent occurrence in the human modified landscapes found in Indonesia, the extent of the 2015 fires was greatly inflated by an extended drought period associated with a strong El Niño. We estimate carbon emissions from the 2015 fires to be the largest seen in maritime southeast Asia since those associated with the record breaking El Niño of 1997. Compared to that event, a much better constrained regional total carbon emission estimate can be made for the 2015 fires through the use of present-day satellite observations of the fire’s radiative power output and atmospheric CO concentrations, processed using the modelling and assimilation framework of the Copernicus Atmosphere Monitoring Service (CAMS) and combined with unique in situ smoke measurements made on Kalimantan.

Koo, J.-H., J. Kim, J. Kim, H. Lee, Y. M. Noh, and Y. G. Lee (2016), Springtime trans-Pacific transport of Asian pollutants characterized by the Western Pacific (WP) pattern, Atmos. Environ., 147, 166177, doi:10.1016/j.atmosenv.2016.10.007.
Springtime trans-Pacific transport of Asian air pollutants has been investigated in many ways to figure out its mechanism. Based on the Western Pacific (WP) pattern, one of climate variabilities in the Northern Hemisphere known to be associated with the pattern of atmospheric circulation over the North Pacific Ocean, in this study, we characterize the pattern of springtime trans-Pacific transport using long-term satellite measurements and reanalysis datasets. A positive WP pattern is characterized by intensification of the dipole structure between the northern Aleutian Low and the southern Pacific High over the North Pacific. The TOMS/OMI Aerosol Index (Al) and MOPITT CO show the enhancement of Asian pollutant transport across the Pacific during periods of positive WP pattern, particularly between 40 and 50 degrees N. This enhancement is confirmed by high correlations of WP index with AI and CO between 40 and 50 degrees N. To evaluate the influence of the WP pattern, we examine several cases of trans-Pacific transport reported in previous research. Interestingly, most trans-Pacific transport cases are associated with the positive WP pattern. During the period of negative WP pattern, reinforced cyclonic wave breaking is consistently found over the western North Pacific, which obstructs zonal advection across the North Pacific. However, some cases show the trans-Pacific transport of CO in the period of negative WP pattern, implying that the WP pattern is more influential on the transport of particles mostly emitted near similar to 40 degrees N. This study reveals that the WP pattern can be utilized to diagnose the strength of air pollutant transport from East Asia to North America. (C) 2016 Elsevier Ltd. All rights reserved.

Liu, X.-Y., Y. Zhang, Q. Zhang, and K.-B. He (2016), Application of online-coupled WRF/Chem-MADRID in East Asia: Model evaluation and climatic effects of anthropogenic aerosols, Atmospheric Environment, 124, Part B, 321336, doi:10.1016/j.atmosenv.2015.03.052.
The online-coupled Weather Research and Forecasting model with Chemistry with the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (referred to as WRF/Chem-MADRID) is applied to simulate meteorological fields, air quality, and the direct and indirect effects of anthropogenic aerosols over East Asia in four months (January, April, July, and October) in 2008. Model evaluation against available surface and satellite measurements shows that despite some model biases, WRF/Chem-MADRID is able to reproduce reasonably well the spatial and seasonal variations of most meteorological fields and chemical concentrations. Large model biases for chemical concentrations are attributed to uncertainties in emissions and their spatial and vertical allocations, simulated meteorological fields, imperfectness of model representations of aerosol formation processes, uncertainties in the observations based on air pollution index, and the use of a coarse grid resolution. The results show that anthropogenic aerosols can reduce net shortwave flux at the surface by up to 40.557.2 W m−2, Temperature at 2-m by up to 0.50.8 °C, NO2 photolytic rates by up to 0.060.1 min−1 and the planetary boundary layer height by up to 83.6130.4 m. Anthropogenic aerosols contribute to the number concentrations of aerosols by up to 6.28.6 × 104 cm−3 and the surface cloud concentration nuclei at a supersaturation of 0.5% by up to 1.01.6 × 104 cm−3. They increase the column cloud droplet number concentrations by up to 3.611.7 × 108 cm−2 and cloud optical thickness by up to 19.833.2. However, anthropogenic aerosols decrease daily precipitation in most areas by up to 3.918.6 mm during the 4 months. These results indicate the importance of anthropogenic aerosols in modulating regional climate changes in East Asia through aerosol direct and indirect effects, as well as the need to further improve the performance of online-coupled models.

Lowry, D., M. E. Lanoiselle, R. E. Fisher, M. Martin, C. M. R. Fowler, J. L. France, I. Y. Hernandez-Paniagua, P. C. Novelli, S. Sriskantharajah, P. O’Brien, N. D. Rata, C. W. Holmes, Z. L. Fleming, K. C. Clemitshaw, G. Zazzeri, M. Pommier, C. A. McLinden, and E. G. Nisbet (2016), Marked long-term decline in ambient CO mixing ratio in SE England, 1997-2014: evidence of policy success in improving air quality, Sci Rep, 6, 25661, doi:10.1038/srep25661.
Atmospheric CO at Egham in SE England has shown a marked and progressive decline since 1997, following adoption of strict controls on emissions. The Egham site is uniquely positioned to allow both assessment and comparison of “clean Atlantic background” air and CO-enriched air downwind from the London conurbation. The decline is strongest (approximately 50 ppb per year) in the 1997-2003 period but continues post 2003. A “local CO increment” can be identified as the residual after subtraction of contemporary background Atlantic CO mixing ratios from measured values at Egham. This increment, which is primarily from regional sources (during anticyclonic or northerly winds) or from the European continent (with easterly air mass origins), has significant seasonality, but overall has declined steadily since 1997. On many days of the year CO measured at Egham is now not far above Atlantic background levels measured at Mace Head (Ireland). The results are consistent with MOPITT satellite observations and “bottom-up” inventory results. Comparison with urban and regional background CO mixing ratios in Hong Kong demonstrates the importance of regional, as opposed to local reduction of CO emission. The Egham record implies that controls on emissions subsequent to legislation have been extremely successful in the UK.

Mizzi, A. P., A. F. Arellano, D. P. Edwards, J. L. Anderson, and G. G. Pfister (2016), Assimilating compact phase space retrievals of atmospheric composition with WRF-Chem/DART: a regional chemical transport/ensemble Kalman filter data assimilation system, Geosci. Model Dev., 9(3), 965978, doi:10.5194/gmd-9-965-2016.
This paper introduces the Weather Research and Forecasting Model with chemistry/Data Assimilation Research Testbed (WRF-Chem/DART) chemical transport forecasting/ data assimilation system together with the assimilation of compact phase space retrievals of satellite-derived atmospheric composition products. WRF-Chem is a state-of-the-art chemical transport model. DART is a flexible software environment for researching ensemble data assimilation with different assimilation and forecast model options. DART’s primary assimilation tool is the ensemble adjustment Kalman filter. WRF-Chem/DART is applied to the assimilation of Terra/Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) trace gas retrieval profiles. Those CO observations are first assimilated as quasi-optimal retrievals (QORs). Our results show that assimilation of the CO retrievals (i) reduced WRF-Chem’s CO bias in retrieval and state space, and (ii) improved the CO forecast skill by reducing the Root Mean Square Error (RMSE) and increasing the Coefficient of Determination (R-2). Those CO forecast improvements were significant at the 95% level. Trace gas retrieval data sets contain (i) large amounts of data with limited information content per observation, (ii) error covariance cross-correlations, and (iii) contributions from the retrieval prior profile that should be removed before assimilation. Those characteristics present challenges to the assimilation of retrievals. This paper addresses those challenges by introducing the assimilation of compact phase space retrievals (CPSRs). CPSRs are obtained by preprocessing retrieval data sets with an algorithm that (i) compresses the retrieval data, (ii) diagonalizes the error covariance, and (iii) removes the retrieval prior profile contribution. Most modern ensemble assimilation algorithms can efficiently assimilate CPSRs. Our results show that assimilation of MOPITT CO CPSRs reduced the number of observations (and assimilation computation costs) by similar to 35 %, while providing CO forecast improvements comparable to or better than with the assimilation of MOPITT CO QORs.

Ojha, N., A. Pozzer, A. Rauthe-Schoech, A. K. Baker, J. Yoon, C. A. M. Brenninkmeijer, and J. Lelieveld (2016), Ozone and carbon monoxide over India during the summer monsoon: regional emissions and transport, Atmos. Chem. Phys., 16(5), 30133032, doi:10.5194/acp-16-3013-2016.
We compare in situ measurements of ozone (O-3) and carbon monoxide (CO) profiles from the CARIBIC program with the results from the regional chemistry transport model (WRF-Chem) to investigate the role of local and regional emissions and long-range transport over southern India during the summer monsoon of 2008. WRF-Chem successfully reproduces the general features of O-3 and CO distributions over the South Asian region. However, absolute CO concentrations in the lower troposphere are typically underestimated. Here we investigate the influence of local relative to remote emissions through sensitivity simulations. The influence of 50aEuro-% increased CO emissions over South Asia leads to a significant enhancement (upto 20aEuro-% in July) in upper tropospheric CO in the northern and central Indian regions. Over Chennai in southern India, this causes a 33aEuro-% increase in surface CO during June. However, the influence of enhanced local and regional emissions is found to be smaller (5aEuro-%) in the free troposphere over Chennai, except during September. Local to regional emissions are therefore suggested to play a minor role in the underestimation of CO by WRF-Chem during June-August. In the lower troposphere, a high pollution (O-3: 146.4 +/- 12.8, CO: 136.4 +/- 12.2aEuro-nmol mol(-1)) event (15 July 2008), not reproduced by the model, is shown to be due to transport of photochemically processed air masses from the boundary layer in southern India. A sensitivity simulation combined with backward trajectories indicates that long-range transport of CO to southern India is significantly underestimated, particularly in air masses from the west, i.e., from Central Africa. This study highlights the need for more aircraft-based measurements over India and adjacent regions and the improvement of global emission inventories.

Osman, M. K., D. W. Tarasick, J. Liu, O. Moeini, V. Thouret, V. E. Fioletov, M. Parrington, and P. Nedelec (2016), Carbon monoxide climatology derived from the trajectory mapping of global MOZAIC-IAGOS data, Atmos. Chem. Phys., 16(15), 1026310282, doi:10.5194/acp-16-10263-2016.
A three-dimensional gridded climatology of carbon monoxide (CO) has been developed by trajectory mapping of global MOZAIC-IAGOS in situ measurements from commercial aircraft data. CO measurements made during aircraft ascent and descent, comprising nearly 41 200 profiles at 148 airports worldwide from December 2001 to December 2012, are used. Forward and backward trajectories are calculated from meteorological reanalysis data in order to map the CO measurements to other locations and so to fill in the spatial domain. This domain-filling technique employs 15 800 000 calculated trajectories to map otherwise sparse MOZAIC-IAGOS data into a quasi-global field. The resulting trajectory-mapped CO data set is archived monthly from 2001 to 2012 on a grid of 5 degrees longitude x 5 degrees latitude x 1 km altitude, from the surface to 14 km altitude. The mapping product has been carefully evaluated, firstly by comparing maps constructed using only forward trajectories and using only backward trajectories. The two methods show similar global CO distribution patterns. The magnitude of their differences is most commonly 10% or less and found to be less than 30% for almost all cases. Secondly, the method has been validated by comparing profiles for individual airports with those produced by the mapping method when data from that site are excluded. While there are larger differences below 2 km, the two methods agree very well between 2 and 10 km with the magnitude of biases within 20 %. Finally, the mapping product is compared with global MOZAIC-IAGOS cruise-level data, which were not included in the trajectory-mapped data set, and with independent data from the NOAA aircraft flask sampling program. The trajectory-mapped MOZAIC-IAGOS CO values show generally good agreement with both independent data sets. Maps are also compared with version 6 data from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument. Both data sets clearly show major regional CO sources such as biomass burning in Central and southern Africa and anthropogenic emissions in eastern China. While the maps show similar features and patterns, and relative biases are small in the lowermost troposphere, we find differences of similar to 20% in CO volume mixing ratios between 500 and 300 hPa. These upper-tropospheric biases are not related to the mapping procedure, as almost identical differences are found with the original in situ MOZAIC-IAGOS data. The total CO trajectory-mapped MOZAIC-IAGOS column is also higher than the MOPITT CO total column by 12-16 %. The data set shows the seasonal CO cycle over different latitude bands and altitude ranges as well as long-term trends over different latitude bands. We observe a decline in CO over the northern hemispheric extratropics and the tropics consistent with that reported by previous studies using other data sources. We anticipate use of the trajectory-mapped MOZAIC-IAGOS CO data set as an a priori climatology for satellite retrieval and for air quality model validation and initialization.

Rakitin, V., N. Elansky, Y. Shtabkin, A. Skorokhod, E. Grechko, N. Pankratova, and A. Safronov (2016), Comparison results of MOPITT, AIRS and IASI data with ground-based spectroscopic measurements of CO and CH4 total contents, vol. 18, p. 1799. [online] Available from: .
A comparative analysis of satellite and ground-based spectroscopic  measurements of CO and CH4 total content (CO TC) in the atmosphere in the background and polluted conditions (stations of OIAP RAS and NDACC) for the 2010-2015 time-period. The significant correlation between satellite and ground-based CO TC data for all satellite sensors in background conditions was obtained. Also the empirical private transient relationships between satellite CO MOPITT v6 Joint, AIRS v6, IASI MeTop-A products and the data of solar-tracking ground-based spectrometers are analyzed. Significant correlation between satellite and ground-based data of CO TC was obtained for all satellite sensors if measurements were carried out over unpolluted areas (2010-2014). It was shown that for polluted areas IASI MetOp-A and AIRSv6 data underestimate the actual value of CO TC by the factor of 1.5÷ 2.8. The average correlation between satellite and ground-based data increased significantly for the case if the measurement days, when the height of the planetary boundary layer (PBL) was less than 400-500 meters, were excluded from the comparison. This result was obtained for all of the selected sensors and observational sites. To improve the representativeness of the satellite CO TC data for polluted areas it could be recommended to exclude the days with low height of the PBL from the analysis of spatio-temporal variations and subsequent data assimilation (as example for the CO emissions estimating from powerful surface sources). Best correlation (R2≥0.5) in diurnal CH4 TC with ground-based data was found for AIRS v6. This work has supported by the Russian Scientific Foundation under grant №14-47-00049 and partially by the Russian Foundation for Basic Research (grant № 13-05-41395).

Raman, A., A. F. Arellano, and A. Sorooshian (2016), Decreasing Aerosol Loading in the North American Monsoon Region, Atmosphere (Basel), 7(2), doi:10.3390/atmos7020024. [online] Available from: .
We examine the spatio-temporal variability of aerosol loading in the recent decade (20052014) over the North American Monsoon (NAM) region. Emerging patterns are characterized using aerosol optical depth (AOD) retrievals from the NASA Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) instrument along with a suite of satellite retrievals of atmospheric and land-surface properties. We selected 20 aerosol hotspots and classified them into fire, anthropogenic, dust, and NAM alley clusters based on the dominant driver influencing aerosol variability. We then analyzed multivariate statistics of associated anomalies during pre-, monsoon, and post-monsoon periods. Our results show a decrease in aerosol loading for the entire NAM region, confirming previous reports of a declining AOD trend over the continental United States. This is evident during pre-monsoon and monsoon for fire and anthropogenic clusters, which are associated with a decrease in the lower and upper quartile of fire counts and carbon monoxide, respectively. The overall pattern is obfuscated in the NAM alley, especially during monsoon and post-monsoon seasons. While the NAM alley is mostly affected by monsoon precipitation, the frequent occurrence of dust storms in the area modulates this trend. We find that aerosol loading in the dust cluster is associated with observed vegetation index and has only slightly decreased in the recent decade.

Saito, M., H.-S. Kim, A. Ito, T. Yokota, and S. Maksyutov (2016), Enhanced Methane Emissions during Amazonian Drought by Biomass Burning, PLoS One, 11(11), e0166039, doi:10.1371/journal.pone.0166039.
The Amazon is a significant source of atmospheric methane, but little is known about the source response to increasing drought severity and frequency. We investigated satellite observations of atmospheric column-averaged methane for the 2010 drought and subsequent 2011 wet year in the Amazon using an atmospheric inversion scheme. Our analysis indicates an increase in atmospheric methane over the southern Amazon region during the drought, representing an increase in annual emissions relative to the wet year. We attribute the increase to emissions from biomass burning driven by intense drought, combined with carbon monoxide showing seasonal variations corresponding to methane variations. We show that there is probably a strong correspondence between drought and methane emissions in the Amazon.

Sarkar, M., C. Venkataraman, S. Guttikunda, and P. Sadavarte (2016), Indian emissions of technology-linked NMVOCs with chemical speciation: An evaluation of the SAPRC99 mechanism with WRF-CAMx simulations, Atmospheric Environment, 134, 7083, doi:10.1016/j.atmosenv.2016.03.037.
Non-methane volatile organic compounds (NMVOCs) are important precursors to reactions producing tropospheric ozone and secondary organic aerosols. The present work uses a detailed technology-linked NMVOC emission database for India, along with a standard mapping method to measured NMVOC profiles, to develop speciated NMVOC emissions, which are aggregated into multiple chemical mechanisms used in chemical transport models. The fully speciated NMVOC emissions inventory with 423 constituent species, was regrouped into model-ready reactivity classes of the RADM2, SAPRC99 and CB-IV chemical mechanisms, and spatially distributed at 25 × 25 km2 resolution, using source-specific spatial proxies. Emissions were considered from four major sectors, i.e. industry, transport, agriculture and residential and from non-combustion activities (use of solvents and paints). It was found that residential cooking with biomass fuels, followed by agricultural residue burning in fields and on-road transport, were largest contributors to the highest reactivity group of NMVOC emissions from India. The emissions were evaluated using WRF-CAMx simulations, using the SAPRC99 photochemical mechanism, over India for contrasting months of April, July and October 2010. Modelled columnar abundance of NO2, CO and O3 agreed well with satellite observations both in magnitude and spatial distribution, in the three contrasting months. Evaluation of monthly and spatial differences between model predictions and observations indicates the need for further refinement of the spatial distribution of NOX emissions, spatio-temporal distribution of agricultural residue burning emissions.

Silver, J. D., J. H. Christensen, M. Kahnert, L. Robertson, P. J. Rayner, and J. Brandt (2016), Multi-species chemical data assimilation with the Danish Eulerian hemispheric model: system description and verification, J Atmos Chem, 73(3), 261302, doi:10.1007/s10874-015-9326-0.
Satellite retrievals of atmospheric composition provide a wealth of data on a global scale. These complement results from atmospheric chemistry-transport models (CTMs), and can be combined using data assimilation. We present two assimilation schemes coupled to the Danish Eulerian Hemispheric Model (DEHM), a three-dimensional, off-line CTM with full photochemistry: a variant on the ensemble Kalman filter and the three-dimensional variational scheme. The aim of this paper is to describe the two schemes and present an initial assessment of their impacts on model skill. Retrievals of multiple atmospheric trace gases are assimilated, namely: NO2 tropospheric column densities, CH4 total column densities, and partial column concentrations of O3, CO and CH4; these data are retrieved from four satellite sensors. Data for each species are assimilated independently of one another, and other species are only adjusted indirectly via the model’s chemistry and dynamics. Assimilation results are compared with measurements from surface monitoring stations and other satellite retrievals, and preliminary validation results are presented.Reference simulations (without assimilation) grossly underestimate surface CO concentrations, and both assimilation schemes eliminate this large and systematic model bias. The assimilation improves the spatial correlation of modelled CO with surface observations, and improves the spatial correlation between forecasts and retrievals for CO, NO2 and O3. Results for CH4 show a loss of skill due to a mismatch in model bias between two assimilated CH4 data-sets. Finally, we discuss differences in methodology and results between this paper and a recent study on multi-species chemical data assimilation. Joint optimisation of initial conditions and emission rates offers a promising direction for improving modelled boundary-layer concentrations.

Strode, S. A., H. M. Worden, M. Damon, A. R. Douglass, B. N. Duncan, L. K. Emmons, J.-F. Lamarque, M. Manyin, L. D. Oman, J. M. Rodriguez, S. E. Strahan, and S. Tilmes (2016), Interpreting space-based trends in carbon monoxide with multiple models, Atmos. Chem. Phys., 16(11), 72857294, doi:10.5194/acp-16-7285-2016.
We use a series of chemical transport model and chemistry climate model simulations to investigate the observed negative trends in MOPITT CO over several regions of the world, and to examine the consistency of time-dependent emission inventories with observations. We find that simulations driven by the MACCity inventory, used for the Chemistry Climate Modeling Initiative (CCMI), reproduce the negative trends in the CO column observed by MOPITT for 2000-2010 over the eastern United States and Europe. However, the simulations have positive trends over eastern China, in contrast to the negative trends observed by MOPITT. The model bias in CO, after applying MOPITT averaging kernels, contributes to the model-observation discrepancy in the trend over eastern China. This demonstrates that biases in a model’s average concentrations can influence the interpretation of the temporal trend compared to satellite observations. The total ozone column plays a role in determining the simulated tropospheric CO trends. A large positive anomaly in the simulated total ozone column in 2010 leads to a negative anomaly in OH and hence a positive anomaly in CO, contributing to the positive trend in simulated CO. These results demonstrate that accurately simulating variability in the ozone column is important for simulating and interpreting trends in CO.

Stroud, C. A., C. Zaganescu, J. Chen, C. A. McLinden, J. Zhang, and D. Wang (2016), Toxic volatile organic air pollutants across Canada: multi-year concentration trends, regional air quality modelling and source apportionment, J Atmos Chem, 73(2), 137164, doi:10.1007/s10874-015-9319-z.
A Unified Regional Air-quality Modelling System, AURAMS, was expanded to predict six toxic volatile organic compounds (VOCs) within a continental domain and two nested domains covering eastern and western Canada. The model predictions were evaluated against Environment Canada’s National Air Pollution Surveillance (NAPS) data set to assess the predictive capability of the model at daily and seasonal time scales. The predictions were also evaluated with satellite-derived column total maps for formaldehyde, carbon monoxide, and nitrogen dioxide. In general, the model showed fair to good predictive skill in terms of both correlation (R) and normalized mean bias (NMB) for benzene (R = 0.53 NMB = 26 %), formaldehyde (R = 0.73, NMB = −15 %) and acetaldehyde (R = 0.55, NMB = 29 %). For the other toxics VOCs, the model showed less predictive skill in the order 1,2,4-trimethylbenzene (R = 0.50, NMB = −41 %), 1,3-butadiene (R = 0.26, NMB = 40 %) and acrolein (R = 0.052, NMB = −51 %). The goal of this study was to apply an air quality model to assess the contribution of mobile sources to ambient levels of toxic VOCs at urban locations across Canada. The mobile source contribution varied in a complex manner for each species for different regions. For benzene and 1,2,4-trimethylbenzene, the mobile source contribution was in the range 4065 % for major Canadian cities. The model predicted considerably lower mobile source contributions for rural locations in the Canadian Prairies, where other area sources dominate, such as the petrochemical industry. Measured concentration trends in toxics are also presented from 2004 to 2010. The primary emitted toxics declined gradually (1316 % over 6 yr) whereas the toxic aldehydes showed no trend.

Te, Y., P. Jeseck, B. Franco, E. Mahieu, N. Jones, C. Paton-Walsh, D. T. Griffith, R. R. Buchholz, J. Hadji-Lazaro, D. Hurtmans, and C. Janssen (2016), Seasonal variability of surface and column carbon monoxide over the megacity Paris, high-altitude Jungfraujoch and Southern Hemispheric Wollongong stations, Atmos. Chem. Phys., 16(17), 1091110925, doi:10.5194/acp-16-10911-2016.
This paper studies the seasonal variation of surface and column CO at three different sites (Paris, Jungfraujoch and Wollongong), with an emphasis on establishing a link between the CO vertical distribution and the nature of CO emission sources. We find the first evidence of a time lag between surface and free tropospheric CO seasonal variations in the Northern Hemisphere. The CO seasonal variability obtained from the total columns and free tropospheric partial columns shows a maximum around March-April and a minimum around September-October in the Northern Hemisphere (Paris and Jungfraujoch). In the Southern Hemisphere (Wollongong) this seasonal variability is shifted by about 6 months. Satellite observations by the IASI-MetOp (Infrared Atmospheric Sounding Interferometer) and MOPITT (Measurements Of Pollution In The Troposphere) instruments confirm this seasonality. Ground-based FTIR (Fourier transform infrared) measurements provide useful complementary information due to good sensitivity in the boundary layer. In situ surface measurements of CO volume mixing ratios at the Paris and Jungfraujoch sites reveal a time lag of the near-surface seasonal variability of about 2 months with respect to the total column variability at the same sites. The chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model) is employed to interpret our observations. GEOS-Chem sensitivity runs identify the emission sources influencing the seasonal variation of CO. At both Paris and Jungfraujoch, the surface seasonality is mainly driven by anthropogenic emissions, while the total column seasonality is also controlled by air masses transported from distant sources. At Wollongong, where the CO seasonality is mainly affected by biomass burning, no time shift is observed between surface measurements and total column data.

Xia, Y., Y. Zhao, and C. P. Nielsen (2016), Benefits of China’s efforts in gaseous pollutant control indicated by the bottom-up emissions and satellite observations 20002014, Atmospheric Environment, 136, 4353, doi:10.1016/j.atmosenv.2016.04.013.
To evaluate the effectiveness of national air pollution control policies, the emissions of SO2, NOX, CO and CO2 in China are estimated using bottom-up methods for the most recent 15-year period (20002014). Vertical column densities (VCDs) from satellite observations are used to test the temporal and spatial patterns of emissions and to explore the ambient levels of gaseous pollutants across the country. The inter-annual trends in emissions and VCDs match well except for SO2. Such comparison is improved with an optimistic assumption in emission estimation that the emission standards for given industrial sources issued after 2010 have been fully enforced. Underestimation of emission abatement and enhanced atmospheric oxidization likely contribute to the discrepancy between SO2 emissions and VCDs. As suggested by VCDs and emissions estimated under the assumption of full implementation of emission standards, the control of SO2 in the 12th Five-Year Plan period (12th FYP, 20112015) is estimated to be more effective than that in the 11th FYP period (20062010), attributed to improved use of flue gas desulfurization in the power sector and implementation of new emission standards in key industrial sources. The opposite was true for CO, as energy efficiency improved more significantly from 2005 to 2010 due to closures of small industrial plants. Iron &amp; steel production is estimated to have had particularly strong influence on temporal and spatial patterns of CO. In contrast to fast growth before 2011 driven by increased coal consumption and limited controls, NOX emissions decreased from 2011 to 2014 due to the penetration of selective catalytic/non-catalytic reduction systems in the power sector. This led to reduced NO2 VCDs, particularly in relatively highly polluted areas such as the eastern China and Pearl River Delta regions. In developed areas, transportation is playing an increasingly important role in air pollution, as suggested by the increased ratio of NO2 to SO2 VCDs. For air quality in mega cities, the inter-annual trends in emissions and VCDs indicate that surrounding areas are more influential in NO2 level for Beijing than those for Shanghai.

Yin, Y., P. Ciais, F. Chevallier, G. R. van der Werf, T. Fanin, G. Broquet, H. Boesch, A. Cozic, D. Hauglustaine, S. Szopa, and Y. Wang (2016), Variability of fire carbon emissions in equatorial Asia and its nonlinear sensitivity to El Nino, Geophys. Res. Lett., 43(19), 1047210479, doi:10.1002/2016GL070971.
The large peatland carbon stocks in the land use change-affected areas of equatorial Asia are vulnerable to fire. Combining satellite observations of active fire, burned area, and atmospheric concentrations of combustion tracers with a Bayesian inversion, we estimated the amount and variability of fire carbon emissions in equatorial Asia over the period 1997-2015. Emissions in 2015 were of 0.510.17Pg carbonless than half of the emissions from the previous 1997 extreme El Nino, explained by a less acute water deficit. Fire severity could be empirically hindcasted from the cumulative water deficit with a lead time of 1 to 2months. Based on CMIP5 climate projections and an exponential empirical relationship found between fire carbon emissions and water deficit, we infer a total fire carbon loss ranging from 12 to 25Pg by 2100 which is a significant positive feedback to climate warming.

Zeb, N., M. Fahim Khokhar, R. Murtaza, A. Noreen, and T. Khalid (2016), Long-Term Changes of Tropospheric Trace Gases over Pakistan Derived From Multiple Satellite Instruments, vol. 41. [online] Available from: .
Air pollution is the expected key environmental issue of Pakistan in  coming years due to its ongoing rapid economic growth and this trend suggests only worst air quality over time. In 2014, World bank reported the Pakistan’s urban air quality among the most severe in the world and intimated the government to make improvement in air quality as a priority policy agenda. In addition it is recommended to strengthen the institutional and technical capacity of organizations responsible for air quality management. Therefore, the study is designed to put efforts in highlighting air quality issues. The study will provide first database for tropospheric trace gases over Pakistan. The study aims to analyse tropospheric concentrations of CO, TOC, NO2 and HCHO over Pakistan using multisensory data from January 2005 to January 2014. Spatio-temporal and seasonal variability of tropospheric trace gases is observed over the decade to explore long term trend. Hotspots are identified to see variation of species with latitude and to highlight possible sources of trace gases over the Pakistan. High concentrations of trace gases are mainly observed over the Punjab region, which may be attributed to its metropolitan importance. It is the major agricultural, industrialized and urbanized (nearly 60% of the Pakistan’s population) sector of the country. Overall significant decreasing trend of CO is identified by MOPITT with relative change of 12.4%. Tropospheric ozone column (TOC) showed insignificant increasing trend with temporal increase of 10.4% whereas NO2 exhibited a significant temporal increase of about 28%. For formaldehyde (HCHO), an increase of about 3.8% is calculated for SCIAMACHY data. Well defined seasonal cycles for these trace gases are observed over the whole study period. CO concentrations showed peak in winter months (November/December/January/February) and dip in the months of Summer/Monsoon (June/July/August). In spite of CO, TCO increases gradually in March and peaks in June (Summer/Monsoon). For NO2, the highest concentrations are observed during Winter and the lowest concentrations are found in Summer/Monsoon. Like TOC, the HCHO showed seasonal maxima during summer and minima during winter. The expected sources are the crop residue burning, biomass/fossil fuel burning for heating purposes, urbanization, industrialization and meterological variations. Further focus is made on exploring the association of trace gases in atmosphere and their source identification.

Zhang, L., H. Jiang, X. Lu, and J. Jin (2016a), Comparison analysis of global carbon monoxide concentration derived from SCIAMACHY, AIRS, and MOPITT, Int. J. Remote Sens., 37(21), 51555175, doi:10.1080/01431161.2016.1230282.
Observations of carbon monoxide (CO) retrieved from Scanning Imaging Absorption SpectroMeter for Atmospheric Chartography (SCIAMACHY), Measurement of Pollution in the Troposphere (MOPITT), and Atmospheric Infrared Sounder (AIRS) are compared in this article. To better validate the retrieved data from SCIAMCHY, AIRS, and MOPITT, six surface stations at different locations and with various elevations were chosen. The results show these three instruments can all reflect CO spatial distribution well and show same temporal variations of CO concentration as well as six surface station measurements. MOPITT and AIRS have similar retrieval results with correlation coefficients being mostly over 0.70, except for a sixth field station on Crozet Island. The three satellites all have the ability to monitor CO concentration change on land, but SCIAMCHY results show a relatively larger bias than MOPITT and AIRS in low CO concentration areas because of systematic error.

Zhang, Y., X. Zhang, L. Wang, Q. Zhang, F. Duan, and K. He (2016b), Application of WRF/Chem over East Asia: Part I. Model evaluation and intercomparison with MM5/CMAQ, Atmospheric Environment, 124, Part B, 285300, doi:10.1016/j.atmosenv.2015.07.022.
In this work, the application of the online-coupled Weather Research and Forecasting model with chemistry (WRF/Chem) version 3.3.1 is evaluated over East Asia for January, April, July, and October 2005 and compared with results from a previous application of an offline model system, i.e., the Mesoscale Model and Community Multiple Air Quality modeling system (MM5/CMAQ). The evaluation of WRF/Chem is performed using multiple observational datasets from satellites and surface networks in mainland China, Hong Kong, Taiwan, and Japan. WRF/Chem simulates well specific humidity (Q2) and downward longwave and shortwave radiation (GLW and GSW) with normalized mean biases (NMBs) within 24%, but shows moderate to large biases for temperature at 2-m (T2) (NMBs of −9.8% to 75.6%) and precipitation (NMBs of 11.492.7%) for some months, and wind speed at 10-m (WS10) (NMBs of 66.5101%), for all months, indicating some limitations in the YSU planetary boundary layer scheme, the Purdue Lin cloud microphysics, and the GrellDevenyi ensemble scheme. WRF/Chem can simulate the column abundances of gases reasonably well with NMBs within 30% for most months but moderately to significantly underpredicts the surface concentrations of major species at all sites in nearly all months with NMBs of −72% to −53.8% for CO, −99.4% to −61.7% for NOx, −84.2% to −44.5% for SO2, −63.9% to −25.2% for PM2.5, and −68.9% to 33.3% for PM10, and aerosol optical depth in all months except for October with NMBs of −38.7% to −16.2%. The model significantly overpredicts surface concentrations of O3 at most sites in nearly all months with NMBs of up to 160.3% and NO 3 - at the Tsinghua site in all months. Possible reasons for large underpredictions include underestimations in the anthropogenic emissions of CO, SO2, and primary aerosol, inappropriate vertical distributions of emissions of SO2 and NO2, uncertainties in upper boundary conditions (e.g., for O3 and CO), missing or inaccurate model representations (e.g., secondary organic aerosol formation, gas/particle partitioning, dust emissions, dry and wet deposition), and inaccurate meteorological fields (e.g., overpredictions in WS10 and precipitation, but underpredictions in T2), as well as the large uncertainties in satellite retrievals (e.g., for column SO2). Comparing to MM5, WRF generally gives worse performance in meteorological predictions, in particular, T2, WS10, GSW, GLW, and cloud fraction in all months, as well as Q2 and precipitation in January and October, due to limitations in the above physics schemes or parameterizations. Comparing to CMAQ, WRF/Chem performs better for surface CO, O3, and PM10 concentrations at most sites in most months, column CO and SO2 abundances, and AOD. It, however, gives poorer performance for surface NOx concentrations at most sites in most months, surface SO2 concentrations at all sites in all months, and column NO2 abundances in January and April. WRF/Chem also gives lower concentrations of most secondary PM and black carbon. Those differences in results are attributed to differences in simulated meteorology, gas-phase chemistry, aerosol thermodynamic and dynamic treatments, dust and sea salt emissions, and wet and dry deposition treatments in both models.

Zhang, Y., C. Hong, K. Yahya, Q. Li, Q. Zhang, and K. He (2016c), Comprehensive evaluation of multi-year real-time air quality forecasting using an online-coupled meteorology-chemistry model over southeastern United States, Atmospheric Environment, 138, 162182, doi:10.1016/j.atmosenv.2016.05.006.
An online-coupled meteorology-chemistry model, WRF/Chem-MADRID, has been deployed for real time air quality forecast (RT-AQF) in southeastern U.S. since 2009. A comprehensive evaluation of multi-year RT-AQF shows overall good performance for temperature and relative humidity at 2-m (T2, RH2), downward surface shortwave radiation (SWDOWN) and longwave radiation (LWDOWN), and cloud fraction (CF), ozone (O3) and fine particles (PM2.5) at surface, tropospheric ozone residuals (TOR) in O3 seasons (May-September), and column NO2 in winters (December-February). Moderate-to-large biases exist in wind speed at 10-m (WS10), precipitation (Precip), cloud optical depth (COT), ammonium (NH4+), sulfate (SO42−), and nitrate (NO3−) from the IMPROVE and SEARCH networks, organic carbon (OC) at IMPROVE, and elemental carbon (EC) and OC at SEARCH, aerosol optical depth (AOD) and column carbon monoxide (CO), sulfur dioxide (SO2), and formaldehyde (HCHO) in both O3 and winter seasons, column nitrogen dioxide (NO2) in O3 seasons, and TOR in winters. These biases indicate uncertainties in the boundary layer and cloud process treatments (e.g., surface roughness, microphysics cumulus parameterization), emissions (e.g., O3 and PM precursors, biogenic, mobile, and wildfire emissions), upper boundary conditions for all major gases and PM2.5 species, and chemistry and aerosol treatments (e.g., winter photochemistry, aerosol thermodynamics). The model shows overall good skills in reproducing the observed multi-year trends and inter-seasonal variability in meteorological and radiative variables such as T2, WS10, Precip, SWDOWN, and LWDOWN, and relatively well in reproducing the observed trends in surface O3 and PM2.5, but relatively poor in reproducing the observed column abundances of CO, NO2, SO2, HCHO, TOR, and AOD. The sensitivity simulations using satellite-constrained boundary conditions for O3 and CO show substantial improvement for both spatial distribution and domain-mean performance statistics. The model’s forecasting skills for air quality can be further enhanced through improving model inputs (e.g., anthropogenic emissions for urban areas and upper boundary conditions of chemical species), meteorological forecasts (e.g., WS10, Precip) and meteorologically-dependent emissions (e.g., biogenic and wildfire emissions), and model physics and chemical treatments (e.g., gas-phase chemistry in winter conditions, cloud processes and their interactions with radiation and aerosol).

Zhang, Y., J. He, S. Zhu, and B. Gantt (2016d), Sensitivity of simulated chemical concentrations and aerosol-meteorology interactions to aerosol treatments and biogenic organic emissions in WRF/Chem, J. Geophys. Res. Atmos., 2016JD024882, doi:10.1002/2016JD024882.
Coupled air quality and climate models can predict aerosol concentrations and properties, as well as aerosol direct and indirect effects that depend on aerosol chemistry and microphysics treatments. In this study, Weather Research and Forecasting with Chemistry (WRF/Chem) simulations are conducted over continental U.S. (CONUS) for January and July 2001 with the same gas-phase mechanism (CB05) but three aerosol modules (Modal Aerosol Dynamics Model for Europe/Secondary Organic Aerosol Model (MADE/SORGAM), Model for Simulating Aerosol Interactions and Chemistry (MOSAIC), and Model of Aerosol Dynamics, Reaction, Ionization and Dissolution (MADRID)) to examine the impacts of aerosol treatments on predictions of aerosols and their effects on cloud properties and radiation. The simulations with the three aerosol modules give similar domain mean predictions of surface PM2.5 concentrations but exhibit a strong spatial variation in magnitudes with large differences in eastern U.S. Large discrepancies are found in the predicted concentrations of sulfate and organic matter due to different treatments in secondary inorganic and secondary organic aerosol (SOA) formation. In particular, the nucleation calculation in MADE/SORGAM causes mass buildup of sulfate which results in much higher sulfate concentrations that those predicted by WRF/Chem with the other two aerosol modules. Different PM mass concentrations and size representations lead to differences in the predicted aerosol number concentrations. The above differences in PM concentrations lead to large differences in simulated condensation nuclei (CCN) and cloud properties in both months. The simulated ranges of domain mean are (1.914.3) × 109 m−3 and (1.45.4) × 109 m−3 for PM2.5 number concentration, (1.63.9) × 108 cm−2 and (1.93.9) × 108 cm−2 for CCN, 102.9208.2 cm−3 and 143.7202.2 cm−3 for column cloud droplet number concentration (CDNC), and 4.56.4 and 3.66.7 for cloud optical depths (COT) in January and July, respectively. The sensitivity simulation for July 2001 using online biogenic emissions increases isoprene concentrations but decreases terpene concentrations, leading to a domain mean increase in O3 (1.5 ppb) and a decrease in biogenic SOA (−0.07 µg m−3) and PM2.5 (−0.2 µg m−3). Anthropogenic emissions contribute to O3, biogenic SOA (BSOA), and PM2.5 concentrations by 38.0%, 44.2%, and 53.6% domain mean and by up to 78.5%, 89.7%, and 96.3%, respectively, indicating that a large fraction of BSOA is controllable through controlling atmospheric oxidant levels in CONUS. Anthropogenic emissions also contribute to a decrease in downward shortwave flux at ground surface (−5.8 W m−2), temperature at 2 m (−0.05°C), wind speed at 10 m (−0.02 m s−1), planetary boundary layer height (−6.6 m), and precipitation (−0.08 mm), as well as an increase in CCN (+5.7 × 10−7 cm−2), in-cloud CDNC (+40.4 cm−3), and COT (+0.6). This work indicates the need for an accurate representation of several aerosol processes such as SOA formation and aerosol-cloud interactions in simulating aerosol direct and indirect effects in the online-coupled models.


Andersson, E., M. Kahnert, and A. Devasthale (2015), Methodology for evaluating lateral boundary conditions in the regional chemical transport model MATCH (v5.5.0) using combined satellite and ground-based observations, Geosci. Model Dev., 8(11), 37473763, doi:10.5194/gmd-8-3747-2015.
Hemispheric transport of air pollutants can have a significant impact on regional air quality, as well as on the effect of air pollutants on regional climate. An accurate representation of hemispheric transport in regional chemical transport models (CTMs) depends on the specification of the lateral boundary conditions (LBCs). This study focuses on the methodology for evaluating LBCs of two moderately long-lived trace gases, carbon monoxide (CO) and ozone (O-3), for the European model domain and over a 7-year period, 2006-2012. The method is based on combining the use of satellite observations at the lateral boundary with the use of both satellite and in situ ground observations within the model domain. The LBCs are generated by the global European Monitoring and Evaluation Programme Meteorological Synthesizing Centre - West (EMEP MSC-W) model; they are evaluated at the lateral boundaries by comparison with satellite observations of the Terra-MOPITT (Measurements Of Pollution In The Troposphere) sensor (CO) and the Aura-OMI (Ozone Monitoring Instrument) sensor (O-3). The LBCs from the global model lie well within the satellite uncertainties for both CO and O-3. The biases increase below 700 hPa for both species. However, the satellite retrievals below this height are strongly influenced by the a priori data; hence, they are less reliable than at, e.g. 500 hPa. CO is, on average, underestimated by the global model, while O-3 tends to be overestimated during winter, and underestimated during summer. A regional CTM is run with (a) the validated monthly climatological LBCs from the global model; (b) dynamical LBCs from the global model; and (c) constant LBCs based on in situ ground observations near the domain boundary. The results are validated against independent satellite retrievals from the Aqua-AIRS (Atmospheric InfraRed Sounder) sensor at 500 hPa, and against in situ ground observations from the Global Atmospheric Watch (GAW) network. It is found that (i) the use of LBCs from the global model gives reliable in-domain results for O-3 and CO at 500 hPa. Taking AIRS retrievals as a reference, the use of these LBCs substantially improves spatial pattern correlations in the free troposphere as compared to results obtained with fixed LBCs based on ground observations. Also, the magnitude of the bias is reduced by the new LBCs for both trace gases. This demonstrates that the validation methodology based on using satellite observations at the domain boundary is sufficiently robust in the free troposphere. (ii) The impact of the LBCs on ground concentrations is significant only at locations in close proximity to the domain boundary. As the satellite data near the ground mainly reflect the a priori estimate used in the retrieval procedure, they are of little use for evaluating the effect of LBCs on ground concentrations. Rather, the evaluation of ground-level concentrations needs to rely on in situ ground observations. (iii) The improvements of dynamic over climatological LBCs become most apparent when using accumulated ozone over threshold 40 ppb (AOT40) as a metric. Also, when focusing on ground observations taken near the inflow boundary of the model domain, one finds that the use of dynamical LBCs yields a more accurate representation of the seasonal variation, as well as of the variability of the trace gas concentrations on shorter timescales.

Badia, A., and O. Jorba (2015), Gas-phase evaluation of the online NMMB/BSC-CTM model over Europe for 2010 in the framework of the AQMEII-Phase2 project, Atmospheric Environment, doi:10.1016/j.atmosenv.2014.05.055. [online] Available from: .
The Air Quality Model Evaluation International Initiative Phase2 aims to intercompare online coupled regional-scale models over North America and Europe. The NMMB/BSC Chemical Transport Model (NMMB/BSC-CTM) is a fully online integrated system for meso- to global-scale applications under development at the Barcelona Supercomputing Center. The NMMB/BSC-CTM is applied to Europe for the year 2010 in the framework of the AQMEII-Phase2 intercomparison exercise. This paper presents a spatial, temporal and vertical evaluation of the gas-phase model results. This is the first time that the model has been evaluated on a regional scale over a whole annual cycle. The model is compared with available ground-based monitoring stations for relevant reactive gases, ozonesondes, and OMI and MOPITT satellite retrievals of NO2 and CO. A comparative analysis of the present results and several European model evaluations is also presented here.  The seasonal cycle for O3, NO2, SO2 and CO is successfully reproduced by the model. The O3 daily mean and daily maximum correlations for the analysed period are r = 0.68 and r = 0.75, respectively. The OMI tropospheric NO2 column retrievals are well reproduced, capturing the most polluted areas over Europe throughout the whole year. Modelled SO2 and CO surface concentrations are generally underestimated, especially during the winter months. Two different vertical configurations of the model (24 and 48 vertical layers) are also analysed. Although model results are very similar, the simulation configured with 48 vertical layers provides better results regarding surface O3 concentrations during summer. Compared to previous model evaluations, the NMMB/BSC-CTM’s performance corresponds to state-of-the-art regional air quality models.

Barre, J., B. Gaubert, A. F. J. Arellano, H. M. Worden, D. P. Edwards, M. N. Deeter, J. L. Anderson, K. Raeder, N. Collins, S. Tilmes, G. Francois, C. Clerbaux, L. K. Emmons, G. G. Pfister, P.-F. Coheur, and D. Hurtmans (2015), Assessing the impacts of assimilating IASI and MOPITT CO retrievals using CESM-CAM-chem and DART, J. Geophys. Res.-Atmos., 120(19), doi:10.1002/2015JD023467.
We show the results and evaluation with independent measurements from assimilating both MOPITT (Measurements Of Pollution In The Troposphere) and IASI (Infrared Atmospheric Sounding Interferometer) retrieved profiles into the Community Earth System Model (CESM). We used the Data Assimilation Research Testbed ensemble Kalman filter technique, with the full atmospheric chemistry CESM component Community Atmospheric Model with Chemistry. We first discuss the methodology and evaluation of the current data assimilation system with coupled meteorology and chemistry data assimilation. The different capabilities of MOPITT and IASI retrievals are highlighted, with particular attention to instrument vertical sensitivity and coverage and how these impact the analyses. MOPITT and IASI CO retrievals mostly constrain the CO fields close to the main anthropogenic, biogenic, and biomass burning CO sources. In the case of IASI CO assimilation, we also observe constraints on CO far from the sources. During the simulation time period (June and July 2008), CO assimilation of both instruments strongly improves the atmospheric CO state as compared to independent observations, with the higher spatial coverage of IASI providing better results on the global scale. However, the enhanced sensitivity of multispectral MOPITT observations to near surface CO over the main source regions provides synergistic effects at regional scales.

Barré, J., D. Edwards, H. Worden, A. Da Silva, and W. Lahoz (2015), On the feasibility of monitoring carbon monoxide in the lower troposphere from a constellation of Northern Hemisphere geostationary satellites. (Part 1), Atmospheric Environment, 113, 6377, doi:10.1016/j.atmosenv.2015.04.069.
By the end of the current decade, there are plans to deploy several geostationary Earth orbit (GEO) satellite missions for atmospheric composition over North America, East Asia and Europe with additional missions proposed. Together, these present the possibility of a constellation of geostationary platforms to achieve continuous time-resolved high-density observations over continental domains for mapping pollutant sources and variability at diurnal and local scales. In this paper, we use a novel approach to sample a very high global resolution model (GEOS-5 at 7 km horizontal resolution) to produce a dataset of synthetic carbon monoxide pollution observations representative of those potentially obtainable from a GEO satellite constellation with predicted measurement sensitivities based on current remote sensing capabilities. Part 1 of this study focuses on the production of simulated synthetic measurements for air quality OSSEs (Observing System Simulation Experiments). We simulate carbon monoxide nadir retrievals using a technique that provides realistic measurements with very low computational cost. We discuss the sampling methodology: the projection of footprints and areas of regard for geostationary geometries over each of the North America, East Asia and Europe regions; the regression method to simulate measurement sensitivity; and the measurement error simulation. A detailed analysis of the simulated observation sensitivity is performed, and limitations of the method are discussed. We also describe impacts from clouds, showing that the efficiency of an instrument making atmospheric composition measurements on a geostationary platform is dependent on the dominant weather regime over a given region and the pixel size resolution. These results demonstrate the viability of the “instrument simulator” step for an OSSE to assess the performance of a constellation of geostationary satellites for air quality measurements. We describe the OSSE results in a follow up paper (Part 2 of this study).

Bhattacharjee, P. S., R. P. Singh, and P. Nedelec (2015), Vertical profiles of carbon monoxide and ozone from MOZAIC aircraft over Delhi, India during 2003-2005, Meteorol. Atmos. Phys., 127(2), 229240, doi:10.1007/s00703-014-0349-x.
The Indo-Gangetic Plains is one of the most densely populated regions in the world and associated with large anthropogenic pollutants. Aircraft measurements of two such pollutants, ozone (O-3) and carbon monoxide (CO) over Delhi, an urban location are analyzed to study monthly and seasonal variations. Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) vertical profile data during 2003-2005 are used in the present study. O-3 over Delhi exhibits a lower tropospheric (surface to 850 mb) high value during post-monsoon (October and November) and winter (December-February) seasons, upper tropospheric (above 400 mb) enhancement during pre-monsoon and a zone of high values in the mid-troposphere (700-400 mb) during monsoon. The anthropogenic emissions show high CO concentrations below 800 mb during winter and pre-monsoon seasons in addition to transported CO in the upper atmosphere during pre-monsoon. During winter season, convective activities are suppressed as a result O-3 and CO concentrations are higher near surface, while during summer season, surface air masses enhance levels of H2O, CO and other trace gases are lifted and subsequently mixed into the large scale circulation that enhance mixing ratios of many trace gases in the upper level anticyclones. MOZAIC observed vertical O-3 profiles are compared with three chemistry-climate coupled models from the Coupled Model Inter-comparison Project Phase5 (CMIP5) with interactive O-3 chemistry. All the models show good agreement with MOZAIC during pre-monsoon, with large biases during winter and monsoon seasons. Finally, monthly variations of MOZAIC observed CO show a good comparison with AIRS and MOPITT satellite data.

Bloom, A. A., J. Worden, Z. Jiang, H. Worden, T. Kurosu, C. Frankenberg, and D. Schimel (2015), Remote-sensing constraints on South America fire traits by Bayesian fusion of atmospheric and surface data, Geophys. Res. Lett., 42(4), 2014GL062584, doi:10.1002/2014GL062584.
Satellite observations reveal substantial burning during the 2007 and 2010 tropical South America fire season, with both years exhibiting similar total burned area. However, 2010 CO fire emissions, based on satellite CO concentration measurements, were substantially lower (−28%), despite the once-in-a-century drought in 2010. We use Bayesian inference with satellite measurements of CH4 and CO concentrations and burned area to quantify shifts in combustion characteristics in 2010 relative to 2007. We find an 88% probability in reduced combusted biomass density associated with the 2010 fires and an 82% probability of lower fire carbon losses in 2010 relative to 2007. Higher combustion efficiency was a smaller contributing factor to the reduced 2010 CO emissions. The reduction in combusted biomass density is consistent with a reduction (46%) in Global Ozone Monitoring Experiment 2 solar-induced fluorescence (a proxy for gross primary production) during the preceding months and a potential reduction in biomass (≤8.3%) due to repeat fires.

Choi, Y., and A. H. Souri (2015), Seasonal behavior and long-term trends of tropospheric ozone, its precursors and chemical conditions over Iran: A view from space, Atmospheric Environment, 106, 232240, doi:10.1016/j.atmosenv.2015.02.012.
To identify spatial and temporal variations over the Iranian region, this study analyzed tropospheric formaldehyde (HCHO) and nitrogen dioxide (NO2) columns from Ozone Monitoring Instrument (OMI), carbon monoxide (CO) columns from the Measurement of Pollution in the Troposphere (MOPITT), and tropospheric column O3 (TCO) from OMI/MLS (Microwave Limb Sounder) satellites from 2005 to 2012. The study discovered high levels of HCHO (∼12 × 1015 molec./cm2) from plant isoprene emissions in the air above parts of the northern forest of Iran during the summer and from the oxidation of HCHO precursors emitted from petrochemical industrial facilities and biomass burning in South West Iran. This study showed that maximum NO2 levels (∼18 × 1015 molec./cm2) were concentrated in urban cities, indicating the predominance of anthropogenic sources. The results indicate that maximum concentrations were found in the winter, mainly because of weaker local winds and higher heating fuel consumption, in addition to lower hydroxyl radicals (OH). The high CO concentrations (∼2 × 1018 molec./cm2) in the early spring were inferred to mainly originate from a strong continental air mass from anthropogenic CO “hotspots” including regions around Caspian Sea, Europe, and North America, although the external sources of CO were partly suppressed by the Arabian anticyclone and topographic barriers. Variations in the TCO were seen to peak during the summer (∼40 DU), due to intensive solar radiation and stratospheric sources. This study also examined long-term trends in TCO and its precursors over a period of eight years in five urban cities in Iran. To perform the analysis, we estimated seasonal changes and inter-seasonal variations using least-squares harmonic estimation (LS-HE), which reduced uncertainty in the trend by 515%. The results showed significant increases in the levels of HCHO (∼0.08 ± 0.06 × 1015 molec./cm2 yr−1), NO2 (∼0.08 ± 0.02 × 1015 molec./cm2 yr−1), and peak annual TCO (∼0.59 ± 0.56 DU yr−1) but decreases in minimum annual TCO (∼−0.42 ± 0.60 DU yr−1) caused by an increase in NO2 species and annual CO (∼−0.95 ± 0.41 × 1016 molec./cm2 yr−1) partly resulting from the transport of reduced CO. The time series of the HCHO/NO2 column ratio (a proxy for the chemical conditions) indicated that during the last decade, the cities of Tehran, Ahvaz, and Isfahan exhibited steady chemical conditions while Tabriz and Mashhad exhibited a change from NOx-saturated/mixed to more NOx-sensitive chemical conditions.

Deeter, M. N., D. P. Edwards, J. C. Gille, and H. M. Worden (2015), Information content of MOPITT CO profile retrievals: Temporal and geographical variability, J. Geophys. Res.-Atmos., 120(24), 1272312738, doi:10.1002/2015JD024024.
Satellite measurements of tropospheric carbon monoxide (CO) enable a wide array of applications including studies of air quality and pollution transport. The MOPITT (Measurements of Pollution in the Troposphere) instrument on the Earth Observing System Terra platform has been measuring CO concentrations globally since March 2000. As indicated by the Degrees of Freedom for Signal (DFS), the standard metric for trace-gas retrieval information content, MOPITT retrieval performance varies over a wide range. We show that both instrumental and geophysical effects yield significant geographical and temporal variability in MOPITT DFS values. Instrumental radiance uncertainties, which describe random errors (or “noise”) in the calibrated radiances, vary over long time scales (e.g., months to years) and vary between the four detector elements of MOPITT’s linear detector array. MOPITT retrieval performance depends on several factors including thermal contrast, fine-scale variability of surface properties, and CO loading. The relative importance of these various effects is highly variable, as demonstrated by analyses of monthly mean DFS values for the United States and the Amazon Basin. An understanding of the geographical and temporal variability of MOPITT retrieval performance is potentially valuable to data users seeking to limit the influence of the a priori through data filtering. To illustrate, it is demonstrated that calculated regional-average CO mixing ratios may be improved by excluding observations from a subset of pixels in MOPITT’s linear detector array.

Ding, K., J. Liu, A. Ding, Q. Liu, T. L. Zhao, J. Shi, Y. Han, H. Wang, and F. Jiang (2015a), Uplifting of carbon monoxide from biomass burning and anthropogenic sources to the free troposphere in East Asia, Atmos. Chem. Phys., 15(5), 28432866, doi:10.5194/acp-15-2843-2015.
East Asia has experienced rapid development with increasing carbon monoxide (CO) emission in the past decades. Therefore, uplifting CO from the boundary layer to the free troposphere in East Asia can have great implications on regional air quality around the world. It can also influence global climate due to the longer lifetime of CO at higher altitudes. In this study, three cases of high CO episodes in the East China Sea and the Sea of Japan from 2003 to 2005 are examined with spaceborne Measurements of Pollution in the Troposphere (MOPITT) data, in combination with aircraft measurements from the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program. High CO abundances of 300550 ppbv are observed in MOZAIC data in the free troposphere during these episodes. These are among the highest CO abundances documented at these altitudes. On average, such episodes with CO over 400 ppbv (in the 2003 and 2004 cases) and between 200 and 300 ppbv (in the 2005 case) may occur 25 and 1020% in time, respectively, in the respective altitudes over the region. Correspondingly, elevated CO is shown in MOPITT daytime data in the middle to upper troposphere in the 2003 case, in the lower to middle troposphere in the 2004 case, and in the upper troposphere in the 2005 case. Through analyses of the simulations from a chemical transport model GEOS-Chem and a trajectory dispersion model FLEXPART, we found different CO signatures in the elevated CO and distinct transport pathways and mechanisms for these cases. In the 2003 case, emissions from large forest fires near Lake Baikal dominated the elevated CO, which had been rapidly transported upward by a frontal system from the fire plumes. In the 2004 case, anthropogenic CO from the North China Plain experienced frontal lifting and mostly reached ~ 700 hPa near the East China Sea, while CO from biomass burning over Indochina experienced orographic lifting, lee-side-trough-induced convection, and frontal lifting through two separate transport pathways, leading to two distinct CO enhancements around 700 and 300 hPa. In the 2005 case, the observed CO of ~ 300 ppbv around 300 hPa originated from anthropogenic sources over the Sichuan Basin and the North China Plain and from forest fires over Indochina. The high CO was transported to such altitudes through strong frontal lifting, interacting with convection and orographic lifting. These cases show that topography affects vertical transport of CO in East Asia via different ways, including orographic uplifting over the Hengduan Mountains, assisting frontal lifting in the North China Plain, and facilitating convection in the Sichuan Basin. In particular, topography-induced lee-side troughs over Indochina led to strong convection that assisted CO uplifting to the upper troposphere. This study shows that the new daytime MOPITT near-infrared (NIR) and thermal-infrared (TIR) data (version 5 or above) have enhanced vertical sensitivity in the free troposphere and may help qualitative diagnosis of vertical transport processes in East Asia.

Ding, K., J. Liu, A. Ding, Q. Liu, T. L. Zhao, J. Shi, Y. Han, H. Wang, and F. Jiang (2015b), Uplifting of carbon monoxide from biomass burning and anthropogenic sources to the free troposphere in East Asia, Atmospheric Chemistry and Physics, 15(5), 28432866, doi:

Abstract. East Asia has experienced rapid development with increasing carbon monoxide (CO) emission in the past decades. Therefore, uplifting CO from the boundary layer to the free troposphere in East Asia can have great implications on regional air quality around the world. It can also influence global climate due to the longer lifetime of CO at higher altitudes. In this study, three cases of high CO episodes in the East China Sea and the Sea of Japan from 2003 to 2005 are examined with spaceborne Measurements of Pollution in the Troposphere (MOPITT) data, in combination with aircraft measurements from the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program. High CO abundances of 300550 ppbv are observed in MOZAIC data in the free troposphere during these episodes. These are among the highest CO abundances documented at these altitudes. On average, such episodes with CO over 400 ppbv (in the 2003 and 2004 cases) and between 200 and 300 ppbv (in the 2005 case) may occur 25 and 1020% in time, respectively, in the respective altitudes over the region. Correspondingly, elevated CO is shown in MOPITT daytime data in the middle to upper troposphere in the 2003 case, in the lower to middle troposphere in the 2004 case, and in the upper troposphere in the 2005 case. Through analyses of the simulations from a chemical transport model GEOS-Chem and a trajectory dispersion model FLEXPART, we found different CO signatures in the elevated CO and distinct transport pathways and mechanisms for these cases. In the 2003 case, emissions from large forest fires near Lake Baikal dominated the elevated CO, which had been rapidly transported upward by a frontal system from the fire plumes. In the 2004 case, anthropogenic CO from the North China Plain experienced frontal lifting and mostly reached ~ 700 hPa near the East China Sea, while CO from biomass burning over Indochina experienced orographic lifting, lee-side-trough-induced convection, and frontal lifting through two separate transport pathways, leading to two distinct CO enhancements around 700 and 300 hPa. In the 2005 case, the observed CO of ~ 300 ppbv around 300 hPa originated from anthropogenic sources over the Sichuan Basin and the North China Plain and from forest fires over Indochina. The high CO was transported to such altitudes through strong frontal lifting, interacting with convection and orographic lifting. These cases show that topography affects vertical transport of CO in East Asia via different ways, including orographic uplifting over the Hengduan Mountains, assisting frontal lifting in the North China Plain, and facilitating convection in the Sichuan Basin. In particular, topography-induced lee-side troughs over Indochina led to strong convection that assisted CO uplifting to the upper troposphere. This study shows that the new daytime MOPITT near-infrared (NIR) and thermal-infrared (TIR) data (version 5 or above) have enhanced vertical sensitivity in the free troposphere and may help qualitative diagnosis of vertical transport processes in East Asia.

Field, R. D., M. Luo, D. Kim, A. D. Del Genio, A. Voulgarakis, and J. Worden (2015), Sensitivity of simulated tropospheric CO to subgrid physics parameterization: A case study of Indonesian biomass burning emissions in 2006, J. Geophys. Res. Atmos., 120(22), 2015JD023402, doi:10.1002/2015JD023402.
Recent cumulus and turbulence parameterization changes to the NASA GISS ModelE2 have improved representation of the Madden-Julian Oscillation and low cloud distribution, but their effect on composition-related quantities is not known. In this study, we simulate the vertical transport of carbon monoxide (CO) from uncontrolled biomass burning in Indonesia in late 2006, during which uniquely high CO was detected in the upper troposphere. Two configurations of ModelE2, one without the changes (AR5) and one with the changes (AR5′), are used for an ensemble simulation of the transport of CO from the biomass burning. The simulation results are evaluated against new CO profiles retrieved jointly from the Aura Tropospheric Emission Spectrometer and the Microwave Limb Sounder. Modeled upper tropospheric CO using the AR5 physics was unrealistically high. The AR5′ physics suppress deep convection that reaches near the tropopause, reducing vertical transport of CO to the upper troposphere and bringing the model into better agreement with satellite CO. In this regard, the most important changes were related to the strength of entrainment of environmental air into the convective column, the strength of re-evaporation above cloud base, and a negative plume buoyancy threshold based on density temperature. This study illustrates how individual, noncomposition model changes can lead to significantly different modeled composition, which in this case improved agreement with satellite retrievals. This study also illuminates the potential usefulness of CO satellite observations in constraining unobservable processes in general circulation models.

George, M., C. Clerbaux, I. Bouarar, P.-F. Coheur, M. N. Deeter, D. P. Edwards, G. Francis, J. C. Gille, J. Hadji-Lazaro, D. Hurtmans, A. Inness, D. Mao, and H. M. Worden (2015), An examination of the long-term CO records from MOPITT and IASI: comparison of retrieval methodology, Atmos. Meas. Tech., 8(10), 43134328, doi:10.5194/amt-8-4313-2015.
Carbon monoxide (CO) is a key atmospheric compound that can be remotely sensed by satellite on the global scale. Fifteen years of continuous observations are now available from the MOPITT/Terra mission (2000 to present). Another 15 and more years of observations will be provided by the IASI/MetOp instrument series (2007-2023 >). In order to study long-term variability and trends, a homogeneous record is required, which is not straightforward as the retrieved quantities are instrument and processing dependent. The present study aims at evaluating the consistency between the CO products derived from the MOPITT and IASI missions, both for total columns and vertical profiles, during a 6-year overlap period (2008-2013). The analysis is performed by first comparing the available 2013 versions of the retrieval algorithms (v5T for MOPITT and v20100815 for IASI), and second using a dedicated reprocessing of MOPITT CO profiles and columns using the same a priori information as the IASI product. MOPITT total columns are generally slightly higher over land (bias ranging from 0 to 13 %) than IASI data. When IASI and MOPITT data are retrieved with the same a priori constraints, correlation coefficients are slightly improved. Large discrepancies (total column bias over 15 %) observed in the Northern Hemisphere during the winter months are reduced by a factor of 2 to 2.5. The detailed analysis of retrieved vertical profiles compared with collocated aircraft data from the MOZAIC-IAGOS network, illustrates the advantages and disadvantages of a constant vs. a variable a priori. On one hand, MOPITT agrees better with the aircraft profiles for observations with persisting high levels of CO throughout the year due to pollution or seasonal fire activity (because the climatology-based a priori is supposed to be closer to the real atmospheric state). On the other hand, IASI performs better when unexpected events leading to high levels of CO occur, due to a larger variability associated with the a priori.

Gonzi, S., P. I. Palmer, R. Paugam, M. Wooster, and M. N. Deeter (2015), Quantifying pyroconvective injection heights using observations of fire energy: sensitivity of spaceborne observations of carbon monoxide, Atmos. Chem. Phys., 15(8), 43394355, doi:10.5194/acp-15-4339-2015.
We use observations of active fire area and fire radiative power (FRP) from the NASA Moderate Resolution Imaging Spectroradiometers (MODIS), together with a parameterized plume rise model, to estimate biomass burning injection heights during 2006. We use these injection heights in the GEOS-Chem (Goddard Earth Observing System Chemistry) atmospheric chemistry transport model to vertically distribute biomass burning emissions of carbon monoxide (CO) and to study the resulting atmospheric distribution. For 2006, we use over half a million FRP and fire area observations as input to the plume rise model. We find that convective heat fluxes and active fire area typically lie in the range of 1-100 k W m(-2) and 0.001-100 ha, respectively, although in rare circumstances the convective heat flux can exceed 500 k W m(-2). The resulting injection heights have a skewed probability distribution with approximately 80% of the injections remaining within the local boundary layer (BL), with occasional injection height exceeding 8 km. We do not find a strong correlation between the FRP-inferred surface convective heat flux and the resulting injection height, with environmental conditions often acting as a barrier to rapid vertical mixing even where the convective heat flux and active fire area are large. We also do not find a robust relationship between the underlying burnt vegetation type and the injection height. We find that CO columns calculated using the MODIS-inferred injection height (MODISINJ) are typically -9 to +6% different to the control calculation in which emissions are emitted into the BL, with differences typically largest over the point of emission. After applying MOPITT (Measurement of Pollution in the Tropo-sphere) v5 scene-dependent averaging kernels we find that we are much less sensitive to our choice of injection height profile. The differences between the MOPITT and the model CO columns (max bias approximate to 50 %), due largely to uncertainties in emission inventories, are much larger than those introduced by the injection heights. We show that including a realistic diurnal variation in FRP (peaking in the afternoon) or accounting for subgrid-scale emission errors does not alter our main conclusions. Finally, we use a Bayesian maximum a posteriori approach constrained by MOPITT CO profiles to estimate the CO emissions but because of the inherent bias between model and MOPITT we find little impact on the resulting emission estimates. Studying the role of pyroconvection in the distribution of gases and particles in the atmosphere using global MOPITT CO observations (or any current spaceborne measurement of the atmosphere) is still associated with large errors, with the exception of a small subset of large fires and favourable environmental conditions, which will consequently lead to a bias in any analysis on a global scale.

ul-Haq, Z., A. D. Rana, M. Ali, K. Mahmood, S. Tariq, and Z. Qayyum (2015), Carbon monoxide (CO) emissions and its tropospheric variability over Pakistan using satellite-sensed data, Adv. Space Res., 56(4), 583595, doi:10.1016/j.asr.2015.04.026.
This study presents major anthropogenic sources of carbon monoxide (CO) in Pakistan and discusses the spatio-temporal variability of tropospheric CO over Pakistan and neighboring regions of Afghanistan, India and Iran for a period from 2003 to 2012 using satellite-sensed (AIRS/AMSU) data. The results show a large spatio-temporal variability of CO over the study region mostly associated with anthropogenic activities such as crop residue burning, vehicular transport, and electricity and energy generation, and local meteorology. The annual mean value of tropospheric CO is observed to be 115 +/- 2 ppbv that remains almost steady during the study period with decadal increase of only 2%. Due to more anthropogenic emissions of CO and its transport, the eastern zone shows a higher average value of 122 +/- 2 ppbv with 2.7% decadal increase than the western zone (111 +/- 3 ppbv with 1.4% decadal increase). Elevated concentrations of CO have been observed over the Indo-Gangetic Basin, Lahore, Karachi, and Delhi. During the study period large fluctuations in CO mean monthly values are found ranging from 99 ppbv to 131 ppbv. The fact that, in spite of a large increase in the CO emissions from 2003 to 2012, its average concentration remains almost stable indicates that a large scale regional transport contributes substantially to the tropospheric CO. Carbon monoxide concentrations exhibit a strong seasonal pattern with maximum amplitude in spring and minimum in autumn. July is found to have the highest decadal increasing trend of 13% followed by August at 8%, whereas May has the highest decreasing trend of -8% followed by November at -4.4%. (C) 2015 COSPAR. Published by Elsevier Ltd. All rights reserved.

He, J., Y. Zhang, T. Glotfelty, R. He, R. Bennartz, J. Rausch, and K. Sartelet (2015), Decadal simulation and comprehensive evaluation of CESM/CAM5.1 with advanced chemistry, aerosol microphysics, and aerosol-cloud interactions, J. Adv. Model. Earth Syst., n/a-n/a, doi:10.1002/2014MS000360.
Earth system models have been used for climate predictions in recent years due to their capabilities to include biogeochemical cycles, human impacts, as well as coupled and interactive representations of Earth system components (e.g., atmosphere, ocean, land, and sea ice). In this work, the Community Earth System Model (CESM) with advanced chemistry and aerosol treatments, referred to as CESM-NCSU, is applied for decadal (2001-2010) global climate predictions. A comprehensive evaluation is performed focusing on the atmospheric component- the Community Atmosphere Model version 5.1 (CAM5.1) by comparing simulation results with observations/reanalysis data and CESM ensemble simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5). The improved model can predict most meteorological and radiative variables relatively well with normalized mean biases (NMBs) of -14.1% to -9.7% and 0.7% to 10.8%, respectively, although temperature at 2-m (T2) is slightly underpredicted. Cloud variables such as cloud fraction (CF) and precipitating water vapor (PWV) are well predicted, with NMBs of -10.5% to 0.4%, whereas cloud condensation nuclei (CCN), cloud liquid water path (LWP), and cloud optical thickness (COT) are moderately-to-largely underpredicted, with NMBs of -82.2% to -31.2%, and cloud droplet number concentration (CDNC) is overpredictd by 26.7%. These biases indicate the limitations and uncertainties associated with cloud microphysics (e.g., resolved clouds and subgrid-scale cumulus clouds). Chemical concentrations over the continental U.S. (CONUS) (e.g., SO42-, Cl-, OC, and PM2.5) are reasonably well predicted with NMBs of -12.8% to -1.18%. Concentrations of SO2, SO42-, and PM10 are also reasonably well predicted over Europe with NMBs of -20.8% to -5.2%, so are predictions of SO2 concentrations over the East Asia with an NMB of -18.2%, and the tropospheric ozone residual (TOR) over the globe with an NMB of -3.5%. Most meteorological and radiative variables predicted by CESM-NCSU agree well overall with those predicted by CESM-CMIP5. The performance of LWP and AOD predicted by CESM-NCSU is better than that of CESM-CMIP5 in terms of model bias and correlation coefficients. Large biases for some chemical predictions can be attributed to uncertainties in the emissions of precursor gases (e.g., SO2, NH3, and NOx) and primary aerosols (black carbon and primary organic matter) as well as uncertainties in formulations of some model components (e.g., online dust and sea-salt emissions, secondary organic aerosol formation, and cloud microphysics). Comparisons of CESM simulation with baseline emissions and 20% of anthropogenic emissions from the baseline emissions indicate that anthropogenic gas and aerosol species can decrease downwelling shortwave radiation (FSDS) by 4.7 W m−2 (or by 2.9%) and increase SWCF by 3.2 W m−2 (or by 3.1%) in the global mean. This article is protected by copyright. All rights reserved.

Inness, A., A.-M. Blechschmidt, I. Bouarar, S. Chabrillat, M. Crepulja, R. J. Engelen, H. Eskes, J. Flemming, A. Gaudel, F. Hendrick, V. Huijnen, L. Jones, J. Kapsomenakis, E. Katragkou, A. Keppens, B. Langerock, M. de Maziere, D. Melas, M. Parrington, V. H. Peuch, M. Razinger, A. Richter, M. G. Schultz, M. Suttie, V. Thouret, M. Vrekoussis, A. Wagner, and C. Zerefos (2015), Data assimilation of satellite-retrieved ozone, carbon monoxide and nitrogen dioxide with ECMWF’s Composition-IFS, Atmos. Chem. Phys., 15(9), 52755303, doi:10.5194/acp-15-5275-2015.
Daily global analyses and 5-day forecasts are generated in the context of the European Monitoring Atmospheric Composition and Climate (MACC) project using an extended version of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The IFS now includes modules for chemistry, deposition and emission of reactive gases, aerosols, and greenhouse gases, and the 4-dimensional variational data assimilation scheme makes use of multiple satellite observations of atmospheric composition in addition to meteorological observations. This paper describes the data assimilation setup of the new Composition-IFS (C-IFS) with respect to reactive gases and validates analysis fields of ozone (O-3), carbon monoxide (CO), and nitrogen dioxide (NO2) for the year 2008 against independent observations and a control run without data assimilation. The largest improvement in CO by assimilation of Measurements of Pollution in the Troposphere (MOPITT) CO columns is seen in the lower troposphere of the Northern Hemisphere (NH) extratropics during winter, and during the South African biomass-burning season. The assimilation of several O-3 total column and stratospheric profile retrievals greatly improves the total column, stratospheric and upper tropospheric O-3 analysis fields relative to the control run. The impact on lower tropospheric ozone, which comes from the residual of the total column and stratospheric profile O-3 data, is smaller, but nevertheless there is some improvement particularly in the NH during winter and spring. The impact of the assimilation of tropospheric NO2 columns from the Ozone Monitoring Instrument (OMI) is small because of the short lifetime of NO2, suggesting that NO2 observations would be better used to adjust emissions instead of initial conditions. The results further indicate that the quality of the tropospheric analyses and of the stratospheric ozone analysis obtained with the C-IFS system has improved compared to the previous “coupled” model system of MACC.

Jena, C., S. D. Ghude, G. G. Pfister, D. M. Chate, R. Kumar, G. Beig, D. E. Surendran, S. Fadnavis, and D. M. Lal (2015), Influence of springtime biomass burning in South Asia on regional ozone (O3): A model based case study, Atmospheric Environment, 100, 3747, doi:10.1016/j.atmosenv.2014.10.027.
In this study, for the first time, the influence of springtime (MAM) biomass burning in South Asia on regional ozone (O3) distribution has been evaluated using a regional chemical transport model (WRF-Chem) and the Fire Inventory from NCAR (FINNv1). Model results are compared with satellite retrievals of tropospheric column amounts of carbon monoxide (CO) from MOPITT and nitrogen dioxide (NO2) from OMI. With daily varying emissions, the model captures reasonably well the satellite-derived temporal variations in CO and NO2 (index of agreement (R) for CO is 0.83 and for NO2 is 0.76), indicating the effectiveness of the model in estimating the overall fire impact on a regional scale. Simulated tropospheric NO2 concentration shows better agreement with the magnitude of observed NO2 when FINNv1 NOx emissions are reduced by a factor of 2.2 over the model domain. A clear increase in CO and NO2 levels over Burma (3560%), Central India (1530%), the Indo-Gangetic (1525%) region and the Bay of Bengal (1540%) are simulated with fire emissions. The model results are also used to quantify the net O3 production from fires. Calculated O3 productions are up to 4 ppb h−1 over inland and up to 0.1 ppb h−1 over marine regions respectively. Our model-based analysis yields average enhancement ratios ΔO3/ΔCO of 0.12 ppbv/ppbv and a total O3 production of about 3.5 Tg from South Asia during the spring season. The findings demonstrate that the springtime fire emissions in South Asia have a noticeable impact on the O3 in this region.

Jiang, Z., J. R. Worden, D. B. A. Jones, J.-T. Lin, W. W. Verstraeten, and D. K. Henze (2015a), Constraints on Asian ozone using Aura TES, OMI and Terra MOPITT, Atmos. Chem. Phys., 15(1), 99112, doi:10.5194/acp-15-99-2015.
Rapid industrialization in Asia in the last two decades has resulted in a significant increase in Asian ozone (O-3/precursor emissions with likely a corresponding increase in the export of O-3 and its precursors. However, the relationship between this increasing O-3, the chemical environment, O-3 production efficiency, and the partitioning between anthropogenic and natural precursors is unclear. In this work, we use satellite measurements of O-3, CO and NO2 from TES (Tropospheric Emission Spectrometer), MO-PITT (Measurement of Pollution In The Troposphere) and OMI (Ozone Monitoring Instrument) to quantify O-3 precursor emissions for 2006 and their impact on free tropospheric O-3 over northeastern Asia, where pollution is typically exported globally due to strong westerlies. Using the GEOS-Chem (Goddard Earth Observing System Chemistry) global chemical transport model, we test the modeled seasonal and interannual variation of O-3 based on prior and updated O-3 precursor emissions where the updated emissions of CO and NOx are based on satellite measurements of CO and NO2. We show that the observed TES O-3 variability and amount are consistent with the model for these updated emissions. However, there is little difference in the modeled ozone between the updated and prior emissions. For example, for the 2006 June time period, the prior and posterior NOx emissions were 14% different over China but the modeled ozone in the free troposphere was only 2.5% different. Using the ad-joint of GEOS-Chem we partition the relative contributions of natural and anthropogenic sources to free troposphere O-3 in this region. We find that the influence of lightning NOx in the summer is comparable to the contribution from surface emissions but smaller for other seasons. China is the primary contributor of anthropogenic CO, emissions and their export during the summer. While the posterior CO emissions improved the comparison between model and TES by 32%, on average, this change also had only a small effect on the free tropospheric ozone. Our results show that the influence of India and southeastern Asia emissions on O-3 pollution export to the northwestern Pacific is sizeable, comparable with Chinese emissions in winter, about 50% of Chinese emissions in spring and fall, and approximately 20% of the emissions in the summer.

Jiang, Z., D. B. A. Jones, J. Worden, H. M. Worden, D. K. Henze, and Y. X. Wang (2015b), Regional data assimilation of multi-spectral MOPITT observations of CO over North America, Atmos. Chem. Phys., 15(12), 68016814, doi:10.5194/acp-15-6801-2015.
Chemical transport models (CTMs) driven with high-resolution meteorological fields can better resolve small-scale processes, such as frontal lifting or deep convection, and thus improve the simulation and emission estimates of tropospheric trace gases. In this work, we explore the use of the GEOS-Chem four-dimensional variational (4D-Var) data assimilation system with the nested high-resolution version of the model (0.5A degrees x 0.67A degrees) to quantify North American CO emissions during the period of June 2004-May 2005. With optimized lateral boundary conditions, regional inversion analyses can reduce the sensitivity of the CO source estimates to errors in long-range transport and in the distributions of the hydroxyl radical (OH), the main sink for CO. To further limit the potential impact of discrepancies in chemical aging of air in the free troposphere, associated with errors in OH, we use surface-level multispectral MOPITT (Measurement of Pollution in The Troposphere) CO retrievals, which have greater sensitivity to CO near the surface and reduced sensitivity in the free troposphere, compared to previous versions of the retrievals. We estimate that the annual total anthropogenic CO emission from the contiguous US 48 states was 97 Tg CO, a 14 % increase from the 85 Tg CO in the a priori. This increase is mainly due to enhanced emissions around the Great Lakes region and along the west coast, relative to the a priori. Sensitivity analyses using different OH fields and lateral boundary conditions suggest a possible error, associated with local North American OH distribution, in these emission estimates of 20 % during summer 2004, when the CO lifetime is short. This 20 % OH-related error is 50 % smaller than the OH-related error previously estimated for North American CO emissions using a global inversion analysis. We believe that reducing this OH-related error further will require integrating additional observations to provide a strong constraint on the CO distribution across the domain. Despite these limitations, our results show the potential advantages of combining high-resolution regional inversion analyses with global analyses to better quantify regional CO source estimates.

Jiang, Z., D. B. A. Jones, H. M. Worden, and D. K. Henze (2015c), Sensitivity of top-down CO source estimates to the modeled vertical structure in atmospheric CO, Atmos. Chem. Phys., 15(3), 15211537, doi:10.5194/acp-15-1521-2015.
We assessed the sensitivity of regional CO source estimates to the modeled vertical CO distribution by assimilating multi-spectral MOPITT (Measurements of Pollution In The Troposphere) V5J CO retrievals with the GEOS-Chem model. We compared the source estimates obtained by assimilating the CO profiles and the surface layer retrievals from June 2004 to May 2005. Because the surface layer retrievals are less sensitive to CO in the free troposphere, it is expected that they should provide constraints in the CO source estimates that are less sensitive to the vertical structure of CO in the free troposphere. The inferred source estimates all suggest a reduction in CO emissions in the tropics and subtropics, and an increase in the extratropics over the a priori estimates. The tropical decreases were particularly pronounced for regions where the biogenic source of CO was dominant, suggesting an overestimate of the a priori isoprene source of CO in the model. We found that the differences between the regional source estimates inferred from the profile and surface layer retrievals for 20042005 were small, generally less than 10% for the main continental regions, except for estimates for southern Asia, North America, and Europe. Because of discrepancies in convective transport in the model, the CO source estimates for India and southeastern Asia inferred from the CO profiles were significantly higher than those estimated from the surface layer retrievals during JuneAugust 2004. On the other hand, the profile inversion underestimated the CO emissions from North America and Europe compared to the assimilation of the surface layer retrievals. We showed that vertical transport of air from the North American and European boundary layers is slower than from other continental regions, and thus air in the free troposphere from North America and Europe in the model is more chemically aged, which could explain the discrepancy between the source estimates inferred from the profile and surface layer retrievals. We also examined the impact of the OH distribution on the source estimates and found that the discrepancies between the source estimates obtained with two OH fields were larger when using the profile data, which is consistent with greater sensitivity to the more chemically aged air in the free troposphere. Our findings indicate that regional CO source estimates are sensitive to the vertical CO structure. They suggest that diagnostics to assess the age of air from the continental source regions should help interpret the results from CO source inversions. Our results also suggest that assimilating a broader range of composition measurements to provide better constraint on tropospheric OH and the biogenic sources of CO is essential for reliable quantification of the regional CO budget.

Kapsomenakis, J. (2015), Data assimilation of satellite retrieved ozone, carbon monoxide and nitrogen dioxide with ECMWF&#39;s Composition-IFS, Atmospheric Chemistry and Physics Discussions, 15, doi:doi:10.5194/acpd-15-4265-2015. [online] Available from: .
Daily global analyses and 5day forecasts are generated in the context of the EuropeanMonitoring Atmospheric Composition and Climate (MACC) project using an extendedversion of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). IFS now includes modules for chemistry, deposition and emission of reactive gases, aerosols, and greenhouse gases, and the4-dimensional variational data assimilation scheme makes use of multiple satellite observations of atmospheric composition in addition to meteorological observations. This paper describes the data assimilation setup of the new Composition-IFS (C-IFS) withrespect to reactive gases and validates analysis fields of ozone (O3), carbon monoxide (CO), and nitrogen dioxide (NO2) for the year 2008 against independent observationsand a control run without data assimilation. The largest improvement in CO by as-similation of MOPITT CO columns is seen in the lower troposphere of the NorthernHemisphere (NH) Extratropics during winter, and during the South African biomassburning season. The assimilation of several O3 total column and stratospheric profile retrievals greatly improves the total column, stratospheric and upper tropospheric O3 analysis fields relative to the control run. The impact on lower tropospheric ozone,which comes from the residual of the total column and stratospheric profile O3 data,is smaller, but nevertheless there is some improvement particularly in the NH duringwinter and spring. The impact of the assimilation of OMI tropospheric NO2 columns is small because of the short lifetime of NO2, suggesting that NO2 observations would bebetter used to adjust emissions instead of initial conditions. The results further indicatethat the quality of the tropospheric analyses and of the stratospheric ozone analysis ob-tained with the C-IFS system has improved compared to the previous “coupled” modelsystem of MACC.

Mandal, T. K., S. K. Peshin, C. Sharma, P. K. Gupta, R. Raj, and S. K. Sharma (2015), Study of surface ozone at Port Blair, India, a remote marine station in the Bay of Bengal, J. Atmos. Sol.-Terr. Phys., 129, 142152, doi:10.1016/j.jastp.2015.04.010.
This paper presents seasonal variation of surface ozone monitored continuously at site of the meteorological observatory at Port Blair, a maritime site of the Bay of Bengal for the period of August, 2005-March, 2007. Present observation depicts the characteristics of surface ozone at the remote marine site and the long range transport of pollutants from three different sides i.e., Indian Subcontinent, South East Asia and Indian Ocean. Very high ozone mixing ratio (similar to 70-80 ppbv) is occasionally observed during March and November at this site. A campaign mode of observation of trace gases (surface ozone, CO, NOR, CO2), aerosol concentration and its size, UV radiation at Port Blair was made to understand the role of transport on pollutants during March 16-26, 2002. During this period of observation, a near zero surface ozone of different time scales (few hours) has been observed several times during the period of midnight to early morning. Simultaneously NOx (NO+NO2) (similar to 40 ppbv) and carbon monoxide was observed very high (300-600 ppbv) during this period. Source of this high pollutant are not expected at this remote marine sites although wind patterns, 7-days isentropic back Trajectory analysis and MATCH Model output suggest that polluted air mass has come from eastern side of Indian subcontinent. (C) 2015 Elsevier Ltd. All rights reserved.

Marć, M., M. Tobiszewski, B. Zabiegała, M. de la Guardia, and J. Namieśnik (2015), Current air quality analytics and monitoring: A review, Analytica Chimica Acta, 853, 116126, doi:10.1016/j.aca.2014.10.018.
This review summarizes the different tools and concepts that are commonly applied in air quality monitoring. The monitoring of atmosphere is extremely important as the air quality is an important problem for large communities. Main requirements for analytical devices used for monitoring include a long period of autonomic operation and portability. These instruments, however, are often characterized by poor analytical performance. Monitoring networks are the most common tools used for monitoring, so large-scale monitoring programmes are summarized here. Biomonitoring, as a cheap and convenient alternative to traditional sample collection, is becoming more and more popular, although its main drawback is the lack of standard procedures. Telemonitoring is another approach to air monitoring, which offers some interesting opportunities, such as ease of coverage of large or remote areas, constituting a complementary approach to traditional strategies; however, it requires huge costs.

Marey, H. S., Z. Hashisho, L. Fu, and J. Gille (2015), Spatial and temporal variation in CO over Alberta using measurements from satellites, aircraft, and ground stations, Atmos. Chem. Phys., 15(7), 38933908, doi:10.5194/acp-15-3893-2015.
Alberta is Canada’s largest oil producer, and its oil sands deposits comprise 30% of the world’s oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO) levels over Alberta. The multispectral product that uses both near-infrared (NIR) and the thermal-infrared (TIR) radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT) is examined for the 12-year period from 2002 to 2013. The Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations in forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System) aircraft CO profiles (April 2009-December 2011) are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons: summer and spring. Distinct seasonal patterns of CO at the urban sites (Edmonton and Calgary) point to the strong influence of traffic. Meteorological parameters play an important role in the CO spatial distribution at various pressure levels. Northern Alberta shows a stronger upward lifting motion which leads to larger CO total column values, while the poor dispersion in central and southern Alberta exacerbates the surface CO pollution. Interannual variations in satellite data depict a slightly decreasing trend for both regions, while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO vertical averages and MOZAIC/IAGOS aircraft profiles were in good agreement within the standard deviations at all pressure levels. There is consistency between the time evolution of high-CO episodes monitored by satellite and ground measurements and the fire frequency peak time, which implies that biomass burning has affected the tropospheric CO distribution in northern Alberta. These findings have further demonstrated the potential use of the MOPITT V5 multispectral (NIR + TIR) product for assessing a complicated surface process.

Miyazaki, K., H. J. Eskes, and K. Sudo (2015), A tropospheric chemistry reanalysis for the years 2005-2012 based on an assimilation of OMI, MLS, TES, and MOPITT satellite data, Atmos. Chem. Phys., 15(14), 83158348, doi:10.5194/acp-15-8315-2015.
We present the results from an 8-year tropospheric chemistry reanalysis for the period 2005-2012 obtained by assimilating multiple data sets from the OMI, MLS, TES, and MOPITT satellite instruments. The reanalysis calculation was conducted using a global chemical transport model and an ensemble Kalman filter technique that simultaneously optimises the chemical concentrations of various species and emissions of several precursors. The optimisation of both the concentration and the emission fields is an efficient method to correct the entire tropospheric profile and its year-to-year variations, and to adjust various tracers chemically linked to the species assimilated. Comparisons against independent aircraft, satellite, and ozonesonde observations demonstrate the quality of the analysed O-3, NO2, and CO concentrations on regional and global scales and for both seasonal and year-to-year variations from the lower troposphere to the lower stratosphere. The data assimilation statistics imply persistent reduction of model error and improved representation of emission variability, but they also show that discontinuities in the availability of the measurements lead to a degradation of the reanalysis. The decrease in the number of assimilated measurements increased the ozonesonde-minus-analysis difference after 2010 and caused spurious variations in the estimated emissions. The Northern/Southern Hemisphere OH ratio was modified considerably due to the multiple-species assimilation and became closer to an observational estimate, which played an important role in propagating observational information among various chemical fields and affected the emission estimates. The consistent concentration and emission products provide unique information on year-to-year variations in the atmospheric environment.

Penning de Vries, M. J. M., S. Beirle, C. Hörmann, J. W. Kaiser, P. Stammes, L. G. Tilstra, O. N. E. Tuinder, and T. Wagner (2015), A global aerosol classification algorithm incorporating multiple satellite data sets of aerosol and trace gas abundances, Atmospheric Chemistry and Physics, 15(18), 1059710618, doi:

Abstract. Detecting the optical properties of aerosols using passive satellite-borne measurements alone is a difficult task due to the broadband effect of aerosols on the measured spectra and the influences of surface and cloud reflection. We present another approach to determine aerosol type, namely by studying the relationship of aerosol optical depth (AOD) with trace gas abundance, aerosol absorption, and mean aerosol size. Our new Global Aerosol Classification Algorithm, GACA, examines relationships between aerosol properties (AOD and extinction Ångström exponent from the Moderate Resolution Imaging Spectroradiometer (MODIS), UV Aerosol Index from the second Global Ozone Monitoring Experiment, GOME-2) and trace gas column densities (NO2, HCHO, SO2 from GOME-2, and CO from MOPITT, the Measurements of Pollution in the Troposphere instrument) on a monthly mean basis. First, aerosol types are separated based on size (Ångström exponent) and absorption (UV Aerosol Index), then the dominating sources are identified based on mean trace gas columns and their correlation with AOD. In this way, global maps of dominant aerosol type and main source type are constructed for each season and compared with maps of aerosol composition from the global MACC (Monitoring Atmospheric Composition and Climate) model. Although GACA cannot correctly characterize transported or mixed aerosols, GACA and MACC show good agreement regarding the global seasonal cycle, particularly for urban/industrial aerosols. The seasonal cycles of both aerosol type and source are also studied in more detail for selected 5° &times; 5° regions. Again, good agreement between GACA and MACC is found for all regions, but some systematic differences become apparent: the variability of aerosol composition (yearly and/or seasonal) is often not well captured by MACC, the amount of mineral dust outside of the dust belt appears to be overestimated, and the abundance of secondary organic aerosols is underestimated in comparison with GACA. Whereas the presented study is of exploratory nature, we show that the developed algorithm is well suited to evaluate climate and atmospheric composition models by including aerosol type and source obtained from measurements into the comparison, instead of focusing on a single parameter, e.g., AOD. The approach could be adapted to constrain the mix of aerosol types during the process of a combined data assimilation of aerosol and trace gas observations.

Rakitin, V. S. S. (2015), Results of comparison of satellite and ground-based spectroscopic CO, CH 4, and CO 2 columns measurements, Optika atmosfery i okeana, 28(9), 816824, doi:10.15372/AOO20150907.
A significant amount of satellite and ground data of the CO, CO 2, CH 4 total content in the atmosphere in 2010-2013 was collected, organized and analyzed. Transition relations between satellite and ground-based data on the content of impurities investigated in different measuring points (stations NDACC/GAW, as well as the OIAP RAS stations) with different spatial and temporal resolutions has been obtained. High correlation of diurnal satellite CO contents, products of AIRS v6 ( R 2 = 0.48-0.96), IASI MetOp-A ( R 2 = 0.25-0.86) and MOPITT v6 Joint ( R 2 = 0.30-0.83), averaging 1° x 1°, with the ground data of solar spectrometers was established for background conditions. In the case of high pollution of the mixing layer, a significant underestimation of CO total content (from 1.7 to 4.7 times, depending on the sensor, and the spatial point of observation) was seen. Representative transition relations and correlation coefficients ( R 2 ≥ 0.5) between the average daily data on CH 4 and ground data diffraction spectrometers IAP RAS and Fourier spectrometers of GAW stations were obtained only for sensor AIRS. The best correlation with ground data on CO 2 ( R 2 = 0.25 for diurnal values, averaging 1° x 1°) was obtained for the sensor IASI. Diurnal CH 4 total contents of sensor IASI MetOp-A poorly correlated with ground-based data as well as AIRS data.

Surendran, D. E., S. D. Ghude, G. Beig, L. K. Emmons, C. Jena, R. Kumar, G. G. Pfister, and D. M. Chate (2015), Air quality simulation over South Asia using Hemispheric Transport of Air Pollution version-2 (HTAP-v2) emission inventory and Model for Ozone and Related chemical Tracers (MOZART-4), Atmos. Environ., 122, 357372, doi:10.1016/j.atmosenv.2015.08.023.
This study presents the distribution of tropospheric ozone and related species for South Asia using the Model for Ozone and Related chemical Tracers (MOZART-4) and Hemispheric Transport of Air Pollution version-2 (HTAP-v2) emission inventory. The model present-day simulated ozone (O-3), carbon monoxide (CO) and nitrogen dioxide (NO2) are evaluated against surface-based, balloon-borne and satellite-based (MOPITT and OMI) observations. The model systematically overestimates surface O-3 mixing ratios (range of mean bias about: 1-30 ppbv) at different ground-based measurement sites in India. Comparison between simulated and observed vertical profiles of ozone shows a positive bias from the surface up to 600 hPa and a negative bias above 600 hPa. The simulated seasonal variation in surface CO mixing ratio is consistent with the surface observations, but has a negative bias of about 50-200 ppb which can be attributed to a large part to the coarse model resolution. In contrast to the surface evaluation, the model shows a positive bias of about 15-20 x 10(17) molecules/cm(2) over South Asia when compared to satellite derived CO columns from the MOPITT instrument. The model also overestimates OMI retrieved tropospheric column NO2 abundance by about 100-250 x 10(13) molecules/cm(2). A response to 20% reduction in all anthropogenic emissions over South Asia shows a decrease in the anuual mean O-3 mixing ratios by about 3-12 ppb, CO by about 10-80 ppb and NOx by about 3-6 ppb at the surface level. During summer monsoon, O-3 mixing ratios at 200 hPa show a decrease of about 6-12 ppb over South Asia and about 1-4 ppb over the remote northern hemispheric western Pacific region. (C) 2015 Elsevier Ltd. All rights reserved.

Wang, K., K. Yahya, Y. Zhang, C. Hogrefe, G. Pouliot, C. Knote, A. Hodzic, R. San Jose, J. L. Perez, P. Jiménez-Guerrero, R. Baro, P. Makar, and R. Bennartz (2015), A multi-model assessment for the 2006 and 2010 simulations under the Air Quality Model Evaluation International Initiative (AQMEII) Phase 2 over North America: Part II. Evaluation of column variable predictions using satellite data, Atmospheric Environment, 115, 587603, doi:10.1016/j.atmosenv.2014.07.044.
Within the context of the Air Quality Model Evaluation International Initiative Phase 2 (AQMEII2) project, this part II paper performs a multi-model assessment of major column abundances of gases, radiation, aerosol, and cloud variables for 2006 and 2010 simulations with three online-coupled air quality models over the North America using available satellite data. It also provides the first comparative assessment of the capabilities of the current generation of online-coupled models in simulating column variables. Despite the use of different model configurations and meteorological initial and boundary conditions, most simulations show comparable model performance for many variables. The evaluation results show an excellent agreement between all simulations and satellite-derived radiation variables including downward surface solar radiation, longwave radiation, and top-of-atmospheric outgoing longwave radiation, as well as precipitable water vapor with domain-average normalized mean biases (NMBs) of typically less than 5% and correlation coefficient (R) typically more than 0.9. Most simulations perform well for column-integrated abundance of CO with domain-average NMBs of −9.4% to −2.2% in 2006 and −12.1% to 4.6% in 2010 and from reasonably well to fair for column NO2, HCHO, and SO2, with domain-average NMBs of −37.7% to 2.1%, −27.3% to 59.2%, and 16.1% to 114.2% in 2006, respectively, and, 12.9% to 102.1%, −25.0% to 87.6%, −65.2% to 7.4% in 2010, respectively. R values are high for CO and NO2 typically between 0.85 and 0.9 (i.e., R2 of 0.70.8). Tropospheric ozone residuals are overpredicted by all simulations due to overestimates of ozone profiles from boundary conditions. Model performance for cloud-related variables is mixed and generally worse compared to gases and radiation variables. Cloud fraction (CF) is well reproduced by most simulations. Other aerosol/cloud related variables such as aerosol optical depth (AOD), cloud optical thickness, cloud liquid water path, cloud condensation nuclei, and cloud droplet number concentration (CDNC) are moderately to largely underpredicted by most simulations, due to underpredictions of aerosol loadings and also indicating high uncertainties associated with the current model treatments of aerosolcloud interactions and the need for further model development. Negative correlations are found for AOD for most simulations due to large negative biases over the western part of the domain. Inter-model discrepancies also exist for a few variables such as column abundances of HCHO and SO2 and CDNC due likely to different chemical mechanisms, biogenic emissions, and treatments of aerosol indirect effects. Most simulations can also capture the inter-annual trend observed by satellites between 2006 and 2010 for several variables such as column abundance of NO2, AOD, CF, and CDNC. Results shown in this work provide the important benchmark for future online-couple air quality model development.

Whaley, C. H., K. Strong, D. B. A. Jones, T. W. Walker, Z. Jiang, D. K. Henze, M. A. Cooke, C. A. McLinden, R. L. Mittermeier, M. Pommier, and P. F. Fogal (2015), Toronto area ozone: Long-term measurements and modeled sources of poor air quality events, J. Geophys. Res. Atmos., 120(21), 2014JD022984, doi:10.1002/2014JD022984.
The University of Toronto Atmospheric Observatory and Environment Canada’s Centre for Atmospheric Research Experiments each has over a decade of ground-based Fourier transform infrared (FTIR) spectroscopy measurements in southern Ontario. We present the Toronto area FTIR time series from 2002 to 2013 of two tropospheric trace gasesozone and carbon monoxidealong with surface in situ measurements taken by government monitoring programs. We interpret their variability with the GEOS-Chem chemical transport model and determine the atmospheric conditions that cause pollution events in the time series. Our analysis includes a regionally tagged O3 model of the 20042007 time period, which quantifies the geographical contributions to Toronto area O3. The important emission types for 15 pollution events are then determined with a high-resolution adjoint model. Toronto O3, during pollution events, is most sensitive to southern Ontario and U.S. fossil fuel NOx emissions and natural isoprene emissions. The sources of Toronto pollution events are found to be highly variable, and this is demonstrated in four case studies representing local, short-, middle-, and long-range transport scenarios. This suggests that continental-scale emission reductions could improve air quality in the Toronto region. We also find that abnormally high temperatures and high-pressure systems are common to all pollution events studied, suggesting that climate change may impact Toronto O3. Finally, we quantitatively compare the sensitivity of the surface and column measurements to anthropogenic NOx emissions and show that they are remarkably similar. This work thus demonstrates the usefulness of FTIR measurements in an urban area to assess air quality.

Yahya, K., J. He, and Y. Zhang (2015), Multiyear applications of WRF/Chem over continental U.S.: Model evaluation, variation trend, and impacts of boundary conditions, J. Geophys. Res. Atmos., 120(24), 2015JD023819, doi:10.1002/2015JD023819.
Multiyear applications of an online-coupled meteorology-chemistry model allow an assessment of the variation trends in simulated meteorology, air quality, and their interactions to changes in emissions and meteorology, as well as the impacts of initial and boundary conditions (ICONs/BCONs) on simulated aerosol-cloud-radiation interactions over a period of time. In this work, the Weather Research and Forecasting model with Chemistry version 3.4.1 (WRF/Chem v. 3.4.1) with the 2005 Carbon Bond mechanism coupled with the Volatility Basis Set module for secondary organic aerosol formation (WRF/Chem-CB05-VBS) is applied for multiple years (2001, 2006, and 2010) over continental U.S. This work also examines the changes in simulated air quality and meteorology due to changes in emissions and meteorology and the model’s capability in reproducing the observed variation trends in species concentrations from 2001 to 2010. In addition, the impacts of the chemical ICONs/BCONs on model predictions are analyzed. ICONs/BCONs are downscaled from two global models, the modified Community Earth System Model/Community Atmosphere model version 5.1 (CESM/CAM v5.1) and the Monitoring Atmospheric Composition and Climate model (MACC). The evaluation of WRF/Chem-CB05-VBS simulations with the CESM ICONs/BCONs for 2001, 2006, and 2010 shows that temperature at 2 m (T2) is underpredicted for all three years likely due to inaccuracies in soil moisture and soil temperature, resulting in biases in surface relative humidity, wind speed, and precipitation. With the exception of cloud fraction, other aerosol-cloud variables including aerosol optical depth, cloud droplet number concentration, and cloud optical thickness are underpredicted for all three years, resulting in overpredictions of radiation variables. The model performs well for O3 and particulate matter with diameter less than or equal to 2.5 (PM2.5) for all three years comparable to other studies from literature. The model is able to reproduce observed annual average trends in O3 and PM2.5 concentrations from 2001 to 2006 and from 2006 to 2010 but is less skillful in simulating their observed seasonal trends. The 2006 and 2010 results using CESM and MACC ICONs/BCONs are compared to analyze the impact of ICONs/BCONs on model performance and their feedbacks to aerosol, clouds, and radiation. Comparing to the simulations with MACC ICONs/BCONs, the simulations with the CESM ICONs/BCONs improve the performance of O3 mixing ratios (e.g., the normalized mean bias for maximum 8 h O3 is reduced from −17% to −1% in 2010), PM2.5 in 2010, and sulfate in 2006 (despite a slightly larger normalized mean bias for PM2.5 in 2006). The impacts of different ICONs/BCONs on simulated aerosol-cloud-radiation variables are not negligible, with larger impacts in 2006 compared to 2010.

Yin, Y., F. Chevallier, P. Ciais, G. Broquet, A. Fortems-Cheiney, I. Pison, and M. Saunois (2015), Decadal trends in global CO emissions as seen by MOPITT, Atmos. Chem. Phys., 15(23), 1343313451, doi:10.5194/acp-15-13433-2015.
Negative trends of carbon monoxide (CO) concentrations are observed in the recent decade by both surface measurements and satellite retrievals over many regions of the globe, but they are not well explained by current emission inventories. Here, we analyse the observed CO concentration decline with an atmospheric inversion that simultaneously optimizes the two main CO sources (surface emissions and atmospheric hydrocarbon oxidations) and the main CO sink (atmospheric hydroxyl radical OH oxidation). Satellite CO column retrievals from Measurements of Pollution in the Troposphere (MOPITT), version 6, and surface observations of methane and methyl chloroform mole fractions are assimilated jointly for the period covering 2002-2011. Compared to the model simulation prescribed with prior emission inventories, trends in the optimized CO concentrations show better agreement with that of independent surface in situ measurements. At the global scale, the atmospheric inversion primarily interprets the CO concentration decline as a decrease in the CO emissions (-2.3% yr(-1)), more than twice the negative trend estimated by the prior emission inventories (-1.0% yr(-1)). The spatial distribution of the inferred decrease in CO emissions indicates contributions from western Europe (-4.0% yr(-1)), the United States (-4.6% yr(-1)) and East Asia (-1.2% yr(-1)), where anthropogenic fuel combustion generally dominates the overall CO emissions, and also from Australia (-5.3% yr(-1)), the Indo-China Peninsula (-5.6% yr(-1)), Indonesia (-6.7% yr(-1)), and South America (-3% yr(-1)), where CO emissions are mostly due to biomass burning. In contradiction with the bottom-up inventories that report an increase of 2% yr(-1) over China during the study period, a significant emission decrease of 1.1% yr(-1) is inferred by the inversion. A large decrease in CO emission factors due to technology improvements would outweigh the increase in carbon fuel combustions and may explain this decrease. Independent satellite formaldehyde (CH2O) column retrievals confirm the absence of large-scale trends in the atmospheric source of CO. However, it should be noted that the CH2O retrievals are not assimilated and OH concentrations are optimized at a very large scale in this study.

Zeng, G., J. E. Williams, J. A. Fisher, L. K. Emmons, N. B. Jones, O. Morgenstern, J. Robinson, D. Smale, C. Paton-Walsh, and D. W. T. Griffith (2015), Multi-model simulation of CO and HCHO in the Southern Hemisphere: comparison with observations and impact of biogenic emissions, Atmospheric Chemistry and Physics, 15(13), 72177245, doi:
We investigate the impact of biogenic emissions on carbon monoxide (CO) and formaldehyde (HCHO) in the Southern Hemisphere (SH), with simulations using two different biogenic emission inventories for isoprene and monoterpenes. Results from four atmospheric chemistry models are compared to continuous long-term ground-based CO and HCHO column measurements at the SH Network for the Detection of Atmospheric Composition Change (NDACC) sites, the satellite measurement of tropospheric CO columns from the Measurement of Pollution in the Troposphere (MOPITT), and in situ surface CO measurements from across the SH, representing a subset of the National Oceanic and Atmospheric Administration’s Global Monitoring Division (NOAA GMD) network. Simulated mean model CO using the Model of Emissions of Gases and Aerosols from Nature (v2.1) computed in the frame work of the Land Community Model (CLM-MEGANv2.1) inventory is in better agreement with both column and surface observations than simulations adopting the emission inventory generated from the LPJ-GUESS dynamical vegetation model framework, which markedly underestimate measured column and surface CO at most sites. Differences in biogenic emissions cause large differences in CO in the source regions which propagate to the remote SH. Significant inter-model differences exist in modelled column and surface CO, and secondary production of CO dominates these inter-model differences, due mainly to differences in the models’ oxidation schemes for volatile organic compounds, predominantly isoprene oxidation. While biogenic emissions are a significant factor in modelling SH CO, inter-model differences pose an additional challenge to constrain these emissions. Corresponding comparisons of HCHO columns at two SH mid-latitude sites reveal that all models significantly underestimate the observed values by approximately a factor of 2. There is a much smaller impact on HCHO of the significantly different biogenic emissions in remote regions, compared to the source regions. Decreased biogenic emissions cause decreased CO export to remote regions, which leads to increased OH; this in turn results in increased HCHO production through methane oxidation. In agreement with earlier studies, we corroborate that significant HCHO sources are likely missing in the models in the remote SH.

Zhang, Y., X. Zhang, K. Wang, J. He, L. R. Leung, J. Fan, and A. Nenes (2015), Incorporating an advanced aerosol activation parameterization into WRF-CAM5: Model evaluation and parameterization intercomparison, J. Geophys. Res. Atmos., 120(14), 2014JD023051, doi:10.1002/2014JD023051.
Aerosol activation into cloud droplets is an important process that governs aerosol indirect effects. The advanced treatment of aerosol activation by Fountoukis and Nenes (2005) and its recent updates, collectively called the FN series, have been incorporated into a newly developed regional coupled climate-air quality model based on the Weather Research and Forecasting model with the physics package of the Community Atmosphere Model version 5 (WRF-CAM5) to simulate aerosol-cloud interactions in both resolved and convective clouds. The model is applied to East Asia for two full years of 2005 and 2010. A comprehensive model evaluation is performed for model predictions of meteorological, radiative, and cloud variables, chemical concentrations, and column mass abundances against satellite data and surface observations from air quality monitoring sites across East Asia. The model performs overall well for major meteorological variables including near-surface temperature, specific humidity, wind speed, precipitation, cloud fraction, precipitable water, downward shortwave and longwave radiation, and column mass abundances of CO, SO2, NO2, HCHO, and O3 in terms of both magnitudes and spatial distributions. Larger biases exist in the predictions of surface concentrations of CO and NOx at all sites and SO2, O3, PM2.5, and PM10 concentrations at some sites, aerosol optical depth, cloud condensation nuclei over ocean, cloud droplet number concentration (CDNC), cloud liquid and ice water path, and cloud optical thickness. Compared with the default Abdul-Razzack Ghan (2000) parameterization, simulations with the FN series produce ~107113% higher CDNC, with half of the difference attributable to the higher aerosol activation fraction by the FN series and the remaining half due to feedbacks in subsequent cloud microphysical processes. With the higher CDNC, the FN series are more skillful in simulating cloud water path, cloud optical thickness, downward shortwave radiation, shortwave cloud forcing, and precipitation. The model evaluation identifies several areas of improvements including emissions and their vertical allocation as well as model formulations such as aerosol formation, cloud droplet nucleation, and ice nucleation.


Amnuaylojaroen, T., M. C. Barth, L. K. Emmons, G. R. Carmichael, J. Kreasuwun, S. Prasitwattanaseree, and S. Chantara (2014), Effect of different emission inventories on modeled ozone and carbon monoxide in Southeast Asia, Atmospheric Chemistry and Physics, 14(23), 1298313012, doi:10.5194/acp-14-12983-2014.
In order to improve our understanding of air quality in Southeast Asia, the anthropogenic emissions inventory must be well represented. In this work, we apply different anthropogenic emission inventories in the Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.3 using Model for Ozone and Related Chemical Tracers (MOZART) gas-phase chemistry and Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) aerosols to examine the differences in predicted carbon monoxide (CO) and ozone (O3) surface mixing ratios for Southeast Asia in March and December 2008. The anthropogenic emission inventories include the Reanalysis of the TROpospheric chemical composition (RETRO), the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), the MACCity emissions (adapted from the Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment projects), the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS) emissions, and a combination of MACCity and SEAC4RS emissions. Biomass-burning emissions are from the Fire Inventory from the National Center for Atmospheric Research (NCAR) (FINNv1) model. WRF-Chem reasonably predicts the 2 m temperature, 10 m wind, and precipitation. In general, surface CO is underpredicted by WRF-Chem while surface O3 is overpredicted. The NO2 tropospheric column predicted by WRF-Chem has the same magnitude as observations, but tends to underpredict the NO2 column over the equatorial ocean and near Indonesia. Simulations using different anthropogenic emissions produce only a slight variability of O3 and CO mixing ratios, while biomass-burning emissions add more variability. The different anthropogenic emissions differ by up to 30 % in CO emissions, but O3 and CO mixing ratios averaged over the land areas of the model domain differ by ∼ 4.5 % and ∼ 8 %, respectively, among the simulations. Biomass-burning emissions create a substantial increase for both O3 and CO by ∼ 29 % and ∼ 16 %, respectively, when comparing the March biomass-burning period to the December period with low biomass-burning emissions. The simulations show that none of the anthropogenic emission inventories are better than the others for predicting O3 surface mixing ratios. However, the simulations with different anthropogenic emission inventories do differ in their predictions of CO surface mixing ratios producing variations of ∼ 30 % for March and 1020 % for December at Thai surface monitoring sites.

Anderson, D. C., C. P. Loughner, G. Diskin, A. Weinheimer, T. P. Canty, R. J. Salawitch, H. M. Worden, A. Fried, T. Mikoviny, A. Wisthaler, and R. R. Dickerson (2014), Measured and modeled CO and NOy in DISCOVER-AQ: An evaluation of emissions and chemistry over the eastern US, Atmospheric Environment, 96, 7887, doi:10.1016/j.atmosenv.2014.07.004.
Data collected during the 2011 DISCOVER-AQ field campaign in the Baltimore Washington region were used to evaluate CO and NOx emissions in the National Emissions Inventory (NEI). The average emissions ratio for the region was seen to be 11.2 ± 1.2 mol CO/mol NOx, 21% higher than that predicted by the NEI. Comparisons between in situ and remote observations and CMAQ model output show agreement in CO emissions of 15 ± 11% while NOx emissions are overestimated by 5170% in Maryland. Satellite observations of CO by MOPITT show agreement with the Community Multiscale Air Quality (CMAQ) model within 3% over most of the eastern United States. CMAQ NOy mixing ratios were a factor of two higher than observations and result from a combination of errors in emissions and PAN and alkyl nitrate chemistry, as shown by comparison of three CMAQ model runs. Point source NOx emissions are monitored and agree with modeled emissions within 1% on a monthly basis. Because of this accuracy and the NEI assertion that approximately 3/4 of emissions in the Baltimore Washington region are from mobile sources, the MOVES model’s treatment of emissions from aging vehicles should be investigated; the NEI overestimate of NOx emissions could indicate that engines produce less NOx and catalytic converters degrade more slowly than assumed by MOVES2010. The recently released 2011 NEI has an even lower CO/NOx emissions ratio than the projection used in this study; it overestimates NOx emissions by an even larger margin. The implications of these findings for US air quality policy are that NOx concentrations near areas of heavy traffic are overestimated and ozone production rates in these locations are slower than models indicate. Results also indicate that ambient ozone concentrations will respond more efficiently to NOx emissions controls but additional sources may need to be targeted for reductions.

Boynard, A., C. Clerbaux, L. Clarisse, S. Safieddine, M. Pommier, M. Van Damme, S. Bauduin, C. Oudot, J. Hadji-Lazaro, D. Hurtmans, and P.-F. Coheur (2014), First simultaneous space measurements of atmospheric pollutants in the boundary layer from IASI: A case study in the North China Plain, Geophys. Res. Lett., 41(2), 645651, doi:10.1002/2013GL058333.
In this paper we investigate a severe pollution episode that occurred in Beijing, Tianjin, and the Hebei province in January 2013. The episode was caused by the combination of anthropogenic emissions and a high-pressure system that trapped pollutants in the boundary layer. Using IASI (Infrared Atmospheric Sounding Interferometer) satellite measurements, high concentrations of key trace gases such as carbon monoxide (CO), sulfur dioxide (SO2), and ammonia (NH3) along with ammonium sulfate aerosol ((NH4)2SO4) are found. We show that IASI is able to detect boundary layer pollution in case of large negative thermal contrast combined with high levels of pollution. Our findings demonstrate that anthropogenic key pollutants, such as CO and SO2, can be monitored by IASI in the North China Plain during wintertime in support of air quality evaluation and management.

Castellanos, P., K. F. Boersma, and G. R. van der Werf (2014), Satellite observations indicate substantial spatiotemporal variability in biomass burning NOx emission factors for South America, Atmos. Chem. Phys., 14(8), 39293943, doi:10.5194/acp-14-3929-2014.
Biomass burning is an important contributor to global total emissions of NOx (NO+NO2). Generally bottom-up fire emissions models calculate NOx emissions by multiplying fuel consumption estimates with static biome-specific emission factors, defined in units of grams of NO per kilogram of dry matter consumed. Emission factors are a significant source of uncertainty in bottom-up fire emissions modeling because relatively few observations are available to characterize the large spatial and temporal variability of burning conditions. In this paper we use NO2 tropospheric column observations from the Ozone Monitoring Instrument (OMI) from the year 2005 over South America to calculate monthly NOx emission factors for four fire types: deforestation, savanna/grassland, woodland, and agricultural waste burning. In general, the spatial patterns in NOx emission factors calculated in this work are consistent with emission factors derived from in situ measurements from the region but are more variable than published biome-specific global average emission factors widely used in bottom-up fire emissions inventories such as the Global Fire Emissions Database (GFED). Satellite-based NOx emission factors also indicate substantial temporal variability in burning conditions. Overall, we found that deforestation fires have the lowest NOx emission factors, on average 30% lower than the emission factors used in GFED v3. Agricultural fire NOx emission factors were the highest, on average a factor of 1.8 higher than GFED v3 values. For savanna, woodland, and deforestation fires, early dry season NOx emission factors were a factor of ~1.52 higher than late dry season emission factors. A minimum in the NOx emission factor seasonal cycle for deforestation fires occurred in August, the time period of severe drought in South America in 2005, supporting the hypothesis that prolonged dry spells may lead to an increase in the contribution of smoldering combustion from large-diameter fuels, offsetting the higher combustion efficiency of dryer fine fuels. We evaluated the OMI-derived NOx emission factors with SCIAMACHY NO2 tropospheric column observations and found improved model performance in regions dominated by fire emissions.

Deeter, M. N., S. Martínez-Alonso, D. P. Edwards, L. K. Emmons, J. C. Gille, H. M. Worden, C. Sweeney, J. V. Pittman, B. C. Daube, and S. C. Wofsy (2014), The MOPITT Version 6 product: algorithm enhancements and validation, Atmos. Meas. Tech., 7(11), 36233632, doi:10.5194/amt-7-3623-2014.
The Measurements of Pollution in the Troposphere (MOPITT) Version 6 (V6) product for carbon monoxide (CO) incorporates several enhancements which will benefit many users of MOPITT data. V6 algorithm improvements are described in detail, and V6 validation results are presented. First, a geolocation bias related to the orientation of the MOPITT instrument relative to the TERRA platform was characterized and eliminated. Second, the variable a priori for CO concentrations for V6 is based on simulations performed with the chemical transport model Community Atmosphere Model with Chemistry (CAM-chem) for the years 20002009 instead of the model-derived climatology for 19972004 used for V5. Third, meteorological fields required for V6 retrieval processing are extracted from the MERRA (Modern-Era Retrospective Analysis For Research And Applications) reanalysis. Finally, a significant latitude-dependent retrieval bias in the upper troposphere in Version 5 products has been substantially reduced.

Duncan, B. N., A. I. Prados, L. N. Lamsal, Y. Liu, D. G. Streets, P. Gupta, E. Hilsenrath, R. A. Kahn, J. E. Nielsen, A. J. Beyersdorf, S. P. Burton, A. M. Fiore, J. Fishman, D. K. Henze, C. A. Hostetler, N. A. Krotkov, P. Lee, M. Lin, S. Pawson, G. Pfister, K. E. Pickering, R. B. Pierce, Y. Yoshida, and L. D. Ziemba (2014), Satellite data of atmospheric pollution for U.S. air quality applications: Examples of applications, summary of data end-user resources, answers to FAQs, and common mistakes to avoid, Atmospheric Environment, 94, 647662, doi:10.1016/j.atmosenv.2014.05.061.
Satellite data of atmospheric pollutants are becoming more widely used in the decision-making and environmental management activities of public, private sector and non-profit organizations. They are employed for estimating emissions, tracking pollutant plumes, supporting air quality forecasting activities, providing evidence for “exceptional event” declarations, monitoring regional long-term trends, and evaluating air quality model output. However, many air quality managers are not taking full advantage of the data for these applications nor has the full potential of satellite data for air quality applications been realized. A key barrier is the inherent difficulties associated with accessing, processing, and properly interpreting observational data. A degree of technical skill is required on the part of the data end-user, which is often problematic for air quality agencies with limited resources. Therefore, we 1) review the primary uses of satellite data for air quality applications, 2) provide some background information on satellite capabilities for measuring pollutants, 3) discuss the many resources available to the end-user for accessing, processing, and visualizing the data, and 4) provide answers to common questions in plain language.

El Amraoui, L., J.-L. Attie, P. Ricaud, W. A. Lahoz, A. Piacentini, V.-H. Peuch, J. X. Warner, R. Abida, J. Barre, and R. Zbinden (2014), Tropospheric CO vertical profiles deduced from total columns using data assimilation: methodology and validation, Atmos. Meas. Tech., 7(9), 30353057, doi:10.5194/amt-7-3035-2014.
This paper presents a validation of a method to derive the vertical profile of carbon monoxide (CO) from its total column using data assimilation. We choose version 3 of MOPITT CO total columns to validate the proposed method. MOPITT products have the advantage of providing both the vertical profiles and the total columns of CO. Furthermore, this version has been extensively validated by comparison with many independent data sets, and has been used in many scientific studies. The first step of the paper consists in the specification of the observation errors based on the chi-square (chi(2)) test. The observations have been binned according to three types: over land during daytime, over land during night-time, and over sea. Their respective errors using the chi(2) metric have been found to be 8, 11 and 7 %. In the second step, the CO total columns, with their specified errors, are used within the assimilation system to estimate the vertical profiles. These are compared to the retrieved profiles of MOPITT V3 at global and regional scales. Generally, the two data sets show similar patterns and good agreement at both scales. Nevertheless, total column analyses slightly overestimate CO concentrations compared to MOPITT observations. The mean bias between both data sets is +15 and +12% at 700 and 250 hPa, respectively. In the third step, the assimilation of total column has been compared to the assimilation of MOPITT vertical profiles. The differences between both analyses are very small. In terms longitude-latitude maps, the mean bias between the two data sets is +6 and +8% at the pressure levels 700 and 200 hPa, respectively. In terms of zonal means, the CO distribution is similar for both analyses, with a mean bias which does not exceed 12 %. Finally, the two analyses have been validated using independent observations from the aircraft-based MOZAIC program in terms of vertical profiles over eight airports. Over most airports, both analyses agree well with aircraft profiles. For more than 50% of recorded measurements, the difference between the analyses and MOZAIC does not exceed 5 ppbv (parts per billion by volume).

Gambacorta, A., C. Barnet, W. Wolf, T. King, E. Maddy, L. Strow, X. Xiong, N. Nalli, and M. Goldberg (2014), An Experiment Using High Spectral Resolution CrIS Measurements for Atmospheric Trace Gases: Carbon Monoxide Retrieval Impact Study, IEEE Geoscience and Remote Sensing Letters, 11(9), 16391643, doi:10.1109/LGRS.2014.2303641.
We perform a demonstration experiment using the National Oceanic Atmospheric Administration Unique Cross-track Infrared Sounder (CrIS)/Advanced Technology Microwave Sounder Processing System to assess the improvement on trace gas retrievals upon switching to high spectral resolution CrIS radiance measurements (0.625 cm-1). The focus of this study is carbon monoxide retrievals. The experimental high spectral resolution CO retrievals show a remarkable improvement, of almost up to one order of magnitude in the degree of freedom of the signal, with respect to the low-resolution mode. Furthermore, high-resolution CO retrievals show similar skill with respect to existing CO operational products from the Atmospheric InfraRed Sounder, Atmospheric Sounder Interferometer, and Measurements of Pollution In The Troposphere instruments, both in terms of spatial variability and degrees of freedom. The results of this research provide evidence to support the need for high spectral resolution CrIS measurements. This is a fundamental prerequisite in guaranteeing continuity to the CO afternoon orbit monitoring as part of a multisatellite uniformly integrated long-term data record of atmospheric trace gases.

Girach, I. A., and P. R. Nair (2014a), Carbon monoxide over Indian region as observed by MOPITT, Atmospheric Environment, 99, 599609, doi:10.1016/j.atmosenv.2014.10.019.
A comprehensive study has been carried out on tropospheric carbon monoxide (CO) over the Indian land mass and surrounding oceanic region using the CO retrievals from MOPITT (Measurements of Pollution in the Troposphere) for a period of ∼14 years (20002014). The lower-tropospheric CO maximises during winter and shows a broad minimum during summer-monsoon over most of the regions, but with regionally varying seasonal amplitudes. Tropospheric column CO also exhibits a seasonal pattern similar to lower-tropospheric CO. But the upper-tropospheric CO shows an opposite seasonal pattern which peaks during summer monsoon. Columnar CO showed strong positive correlation with fire counts over west, east and north-east India, indicating the dominant role of biomass burning in controlling the seasonal variation of CO. The lower-tropospheric and columnar CO showed decreasing trend of 2.03.4 ppb year−1 (1.12.0% year−1) and 6.013.6 × 1015 molecules cm−2 year−1 (0.30.6% year−1) respectively over most of the regions. However, over many land regions trend in columnar CO is not significant. Most strikingly, the upper tropospheric CO showed increasing trend of 1.42.4 ppb year−1 (1.83.2% year−1). The analysis of biases in the estimated trends due to temporal changes in the MOPITT averaging kernels shows that magnitude of the realistic trend may change depending upon the bias but the sign (positive or negative) of trend remains the same. The decreasing trend in lower tropospheric and columnar CO could be attributed partly to increase in lower tropospheric water vapour and/or tropospheric ozone. The strengthening of convective activity, uplifting the CO to higher altitudes, could be a reason for increasing trend in the upper-tropospheric CO.

Girach, I. A., and P. R. Nair (2014b), On the vertical distribution of carbon monoxide over Bay of Bengal during winter: Role of water vapour and vertical updrafts, Journal of Atmospheric and Solar-Terrestrial Physics, 117, 3147, doi:10.1016/j.jastp.2014.05.003.
The differences in the spatial pattern of column carbon monoxide (CO) and in-situ measured near-surface CO over Bay of Bengal (BoB) during winter were examined in the light of vertical distribution of CO as retrieved from MOPITT (Measurements Of Pollution In The Troposphere) on board Terra spacecraft. The column CO showed relatively high values over southern-BoB whereas the near-surface CO showed low mixing ratio indicating the existence of significant amount of CO at higher altitudes. The vertical profiles of CO over the BoB region retrieved from MOPITT exhibit a high altitude peak around ~9 km altitude region. The role of water vapour and convective activity/vertical updrafts in establishing the observed vertical profile of CO was investigated. It is found that CO got uplifted to the higher altitude due to updrafts and water vapour caused depletion of CO at lower altitudes which appeared as an apparent high in CO mixing ratio at higher altitude relative to that over lower altitude. The role of water vapour in the destruction of CO was confirmed by box model simulations. Airmass back-trajectory analysis showed that the long range transport from lower troposphere/boundary layer was also partially responsible for higher mixing ratios at higher altitude. In addition, a comparison of in-situ measured near-surface CO and those retrieved from MOPITT using retrieval algorithm Versions 4 and 5 showed that the points of discrepancy have reduced in the Version 5. Biomass burning and anthropogenic activities taking place over the Myanmar landmass was found to be responsible for the hot spots of near-surface-CO over the northeast-BoB.

Gonzi, S., P. I. Palmer, R. Paugam, M. Wooster, and M. N. Deeter (2014), Quantifying pyroconvective injection heights using observations of fire  energy: sensitivity of space-borne observations of carbon monoxide, Atmos. Chem. Phys. Discuss., 14(16), 2254722585, doi:10.5194/acpd-14-22547-2014.
We use observations of fire size and fire radiative power (FRP) from the NASA Moderate-Resolution Imaging Spectroradiometers (MODIS), together with a parameterized plume rise model, to estimate biomass burning injection heights during 2006.  We use these injection heights in the GEOS-Chem atmospheric chemistry transport  model to  vertically distribute biomass burning emissions of carbon monoxide (CO) and to study the resulting atmospheric distribution. For 2006, we use over half a million FRP and fire size observations as input to the plume rise model.  We find that convective heat fluxes and actual fire sizes typically lie in the range of 1100 kW m−2 and 0.001100 ha, respectively, although in rare circumstances the convective heat flux can exceed 500 kW m−2.  The resulting injection heights have a skewed probability distribution  with approximately 80% of injections remaining within the local boundary layer (BL), with occasional injection height exceeding 8 km. We do not find a strong correlation between the FRP-inferred surface convective heat flux and the  resulting injection height, with environmental conditions often acting as a barrier to rapid vertical mixing even where the convective heat flux and  actual fire size are large. We also do not find a robust relationship between the underlying burnt vegetation type and the injection height. We find that CO columns calculated using the MODIS-inferred injection height (MODIS-inj) are typically  −9+6% different to the control calculation in which emissions are emitted into the BL, with differences typically largest over the point of emission. After applying MOPITT v5 scene-dependent averaging kernels we find that we are much less sensitive to our choice of injection height profile.  The differences between the MOPITT and the model CO columns (max bias ≈ 50%), due largely to uncertainties in emission inventories, are much larger than those introduced by the injection heights. We show that including a realistic diurnal variation in FRP (peaking in the afternoon) or accounting for subgrid-scale emission errors does not alter our main conclusions. Finally, we use a Bayesian maximum a posteriori approach constrained by MOPITT CO profiles to estimate the CO emissions but because of the inherent bias between model and MOPITT  we find little impact on the resulting emission estimates. Studying the role of pyroconvection in distributing gases and particles in the atmosphere using global MOPITT CO observations (or any current space-borne measurement of the atmosphere) is still associated with large errors,  with the exception of a small subset of large fires and favourable environmental conditions, which will consequently lead to a bias in any analysis on a global scale.

Henderson, B. H., F. Akhtar, H. O. T. Pye, S. L. Napelenok, and W. T. Hutzell (2014), A database and tool for boundary conditions for regional air quality modeling: description and evaluation, Geosci. Model Dev., 7(1), 339360, doi:10.5194/gmd-7-339-2014.
Transported air pollutants receive increasing attention as regulations tighten and global concentrations increase. The need to represent international transport in regional air quality assessments requires improved representation of boundary concentrations. Currently available observations are too sparse vertically to provide boundary information, particularly for ozone precursors, but global simulations can be used to generate spatially and temporally varying lateral boundary conditions (LBC). This study presents a public database of global simulations designed and evaluated for use as LBC for air quality models (AQMs). The database covers the contiguous United States (CONUS) for the years 20012010 and contains hourly varying concentrations of ozone, aerosols, and their precursors. The database is complemented by a tool for configuring the global results as inputs to regional scale models (e.g., Community Multiscale Air Quality or Comprehensive Air quality Model with extensions). This study also presents an example application based on the CONUS domain, which is evaluated against satellite retrieved ozone and carbon monoxide vertical profiles. The results show performance is largely within uncertainty estimates for ozone from the Ozone Monitoring Instrument and carbon monoxide from the Measurements Of Pollution In The Troposphere (MOPITT), but there were some notable biases compared with Tropospheric Emission Spectrometer (TES) ozone. Compared with TES, our ozone predictions are high-biased in the upper troposphere, particularly in the south during January. This publication documents the global simulation database, the tool for conversion to LBC, and the evaluation of concentrations on the boundaries. This documentation is intended to support applications that require representation of long-range transport of air pollutants.

de Laat, A. T. J., I. Aben, M. Deeter, P. Nédélec, H. Eskes, J.-L. Attié, P. Ricaud, R. Abida, L. El Amraoui, and J. Landgraf (2014), Validation of nine years of MOPITT V5 NIR using MOZAIC/IAGOS measurements: biases and long-term stability, Atmos. Meas. Tech., 7(11), 37833799, doi:10.5194/amt-7-3783-2014.
Validation results from a comparison between Measurement Of Pollution In The Troposphere (MOPITT) V5 Near InfraRed (NIR) carbon monoxide (CO) total column measurements and Measurement of Ozone and Water Vapour on Airbus in-service Aircraft (MOZAIC)/In-Service Aircraft for a Global Observing System (IAGOS) aircraft measurements are presented. A good agreement is found between MOPITT and MOZAIC/IAGOS measurements, consistent with results from earlier studies using different validation data and despite large variability in MOPITT CO total columns along the spatial footprint of the MOZAIC/IAGOS measurements. Validation results improve when taking the large spatial footprint of the MOZAIC/IAGOS data into account. No statistically significant drift was detected in the validation results over the period 20022010 at global, continental and local (airport) scales. Furthermore, for those situations where MOZAIC/IAGOS measurements differed from the MOPITT a priori, the MOPITT measurements clearly outperformed the MOPITT a priori data, indicating that MOPITT NIR retrievals add value to the MOPITT a priori. Results from a high spatial resolution simulation of the chemistry-transport model MOCAGE (MOdèle de Chimie Atmosphérique à Grande Echelle) showed that the most likely explanation for the large MOPITT variability along the MOZAIC-IAGOS profile flight path is related to spatio-temporal CO variability, which should be kept in mind when using MOZAIC/IAGOS profile measurements for validating satellite nadir observations.

Laken, B. A., and T. Shahbaz (2014), Satellite-Detected Carbon Monoxide Pollution during 20002012: Examining Global Trends and also Regional Anthropogenic Periods over China, the EU and the USA, Climate, 2(1), 116, doi:10.3390/cli2010001.
In this paper, we test if any statistically significant periodicities are detectable in carbon monoxide emissions over China, the European Union, and the United States of America. To do this, we performed a period analysis using 10 years of daily-averaged data, from the Measurements Of Pollution In The Troposphere (MOPITT) instrument. Besides a seasonal period, we found no clearly detectable periods at any timescale with the exception of a strong signal at 2.28 days. This period was observed over all tested regions and persisted when larger (hemisphere-wide) regions were considered. However, rather than resulting from a physical variation in carbon monoxide, it resulted from day-to-day changes in the area covered by MOPITT on-board its polar-orbiting satellite platform. We also examined linear trends over the dataset, and found that MOPITT identifies several centers of increasing carbon monoxide concentrationthe largest being over Chinaalthough globally MOPITT reports a significant decrease in carbon monoxide has occurred over the past decade.

Liu, C., S. Beirle, T. Butler, P. Hoor, C. Frankenberg, P. Jöckel, M. Penning de Vries, U. Platt, A. Pozzer, M. G. Lawrence, J. Lelieveld, H. Tost, and T. Wagner (2014), Profile information on CO from SCIAMACHY observations using cloud slicing and comparison with model simulations, Atmos. Chem. Phys., 14(3), 17171732, doi:10.5194/acp-14-1717-2014.
We apply a cloud slicing technique (CST), originally developed for Total Ozone Mapping Spectrometer (TOMS) ozone observations, to CO vertical column densities retrieved from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). CST makes use of the shielding effect of clouds and combines trace gas column measurements of cloudy pixels with different cloud heights to retrieve fractional columns aloft. Here we determine seasonal mean tropospheric CO profiles at a vertical resolution of about 1 km, which is much finer than what can be obtained from thermal infrared (IR) instruments. However, since both the atmospheric CO profiles and the effective cloud heights depend systematically on meteorology, and in addition part of the retrieved signal originates from the clear part of the satellite ground pixel, the profiles retrieved from the CST have to be interpreted with care. We compare the seasonal mean SCIAMACHY CO profiles with the output from two atmospheric models sampled in the same way as the satellite observations. We find in general good agreement of the spatial patterns, but systematic differences in the absolute values are observed in both hemispheres (more strongly in the Northern Hemisphere), indicating that the source strengths in the emission inventories are probably underestimated.

Mallik, C., and S. Lal (2014), Seasonal characteristics of SO2, NO2, and CO emissions in and around the Indo-Gangetic Plain, Environ Monit Assess, 186(2), 12951310, doi:10.1007/s10661-013-3458-y.
Anthropogenic emissions of sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) exert significant influence on local and regional atmospheric chemistry. Temporal and spatial variability of these gases are investigated using surface measurements by the Central Pollution Control Board (India) during 2005-2009 over six urban locations in and around the Indo-Gangetic Plain (IGP) and supported using the satellite measurements of these gases. The stations chosen are Jodhpur (west of IGP), Delhi (central IGP), Kolkata and Durgapur (eastern IGP), Guwahati (east of IGP), and Nagpur (south of IGP). Among the stations studied, SO2 concentrations are found to be the highest over Kolkata megacity. Elevated levels of NO2 occur over the IGP stations of Durgapur, Kolkata, and Delhi. Columnar NO2 values are also found to be elevated over these regions during winter due to high surface concentrations while columnar SO2 values show a monsoon maximum. Elevated columnar CO over Guwahati during pre-monsoon are attributed to biomass burning. Statistically significant correlations between columnar NO2 and surface NO2 obtained for Delhi, Kolkata, and Durgapur along with very low SO2 to NO2 ratios (≤0.2) indicate fossil fuel combustion from mobile sources as major contributors to the ambient air over these regions.

Martínez-Alonso, S., M. N. Deeter, H. M. Worden, J. C. Gille, L. K. Emmons, L. L. Pan, M. Park, G. L. Manney, P. F. Bernath, C. D. Boone, K. A. Walker, F. Kolonjari, S. C. Wofsy, J. Pittman, and B. C. Daube (2014), Comparison of Upper Tropospheric Carbon Monoxide from MOPITT, ACE-FTS, and HIPPO-QCLS, J. Geophys. Res. Atmos., 2014JD022397, doi:10.1002/2014JD022397.
Products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument are regularly validated using in situ airborne measurements. However, few of these measurements reach into the upper troposphere, thus hindering MOPITT validation in that region. Here we evaluate upper tropospheric (~500 hPa to the tropopause) MOPITT CO profiles by comparing them to satellite Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) retrievals and to measurements from the High-performance Instrumented Airborne Platform for Environmental Research Pole to Pole Observations (HIPPO) Quantum Cascade Laser Spectrometer (QCLS). Direct comparison of co-located v5 MOPITT thermal-infrared-only retrievals, v3.0 ACE-FTS retrievals, and HIPPO-QCLS measurements show a slight positive MOPITT CO bias within its 10% accuracy requirement with respect to the other two datasets. Direct comparison of co-located ACE-FTS and HIPPO-QCLS measurements results in a small number of samples, due to the large disparity in sampling pattern and density of these datasets. Thus, two additional indirect techniques for comparison of non-coincident datasets have been applied: tracer-tracer (CO-O3) correlation analysis and analysis of profiles in tropopause coordinates. These techniques suggest a negative bias of ACE-FTS with respect to HIPPO-QCLS; this could be caused by differences in resolution (horizontal, vertical) or by deficiencies in the ACE-FTS CO retrievals below ~20 km of altitude, among others. We also investigate the temporal stability of MOPITT and ACE-FTS data, which provide unique global CO records and are thus important in climate analysis. Our results indicate that the relative bias between the two datasets has remained generally stable during the 20042010 period.

Miyazaki, K., H. J. Eskes, K. Sudo, and C. Zhang (2014), Global lightning NOx production estimated by an assimilation of multiple satellite data sets, Atmos. Chem. Phys., 14(7), 32773305, doi:10.5194/acp-14-3277-2014.
The global source of lightning-produced NOx (LNOx) is estimated by assimilating observations of NO2, O3, HNO3, and CO measured by multiple satellite measurements into a chemical transport model. Included are observations from the Ozone Monitoring Instrument (OMI), Microwave Limb Sounder (MLS), Tropospheric Emission Spectrometer (TES), and Measurements of Pollution in the Troposphere (MOPITT) instruments. The assimilation of multiple chemical data sets with different vertical sensitivity profiles provides comprehensive constraints on the global LNOx source while improving the representations of the entire chemical system affecting atmospheric NOx, including surface emissions and inflows from the stratosphere. The annual global LNOx source amount and NO production efficiency are estimated at 6.3 Tg N yr−1 and 310 mol NO flash−1, respectively. Sensitivity studies with perturbed satellite data sets, model and data assimilation settings lead to an error estimate of about  1.4 Tg N yr−1 on this global LNOx source. These estimates are significantly different from those estimated from a parameter inversion that optimizes only the LNOx source from NO2 observations alone, which may lead to an overestimate of the source adjustment. The total LNOx source is predominantly corrected by the assimilation of OMI NO2 observations, while TES and MLS observations add important constraints on the vertical source profile. The results indicate that the widely used lightning parameterization based on the C-shape assumption underestimates the source in the upper troposphere and overestimates the peak source height by up to about 1 km over land and the tropical western Pacific. Adjustments are larger over ocean than over land, suggesting that the cloud height dependence is too weak over the ocean in the Price and Rind (1992) approach. The significantly improved agreement between the analyzed ozone fields and independent observations gives confidence in the performance of the LNOx source estimation.

Pan, X. L., Y. Kanaya, Z. F. Wang, X. Tang, M. Takigawa, P. Pakpong, F. Taketani, and H. Akimoto (2014), Using Bayesian optimization method and FLEXPART tracer model to evaluate, Environ. Sci. Pollut. Res., 21(5), 38733879, doi:10.1007/s11356-013-2317-2.
Carbon monoxide (CO) is of great interest as a restriction factor for pollutants related to incomplete combustions. This study attempted to evaluate CO emission in East China using the analytical Bayesian inverse method and observations at Mount Hua in springtime. The mixing ratio of CO at the receptor was calculated using 5-day source-receptor relationship (SRR) simulated by a Lagrangian Particle Dispersion Model (FLEXPART) and CO emission flux. The stability of the inversion solution was evaluated on the basis of repeated random sampling simulations. The inversion results demonstrated that there were two city cluster regions (the Beijing-Tianjin-Hebei region and the low reaches of the Yangtze River Delta) where the difference between a priori (Intercontinental Chemical Transport Experiment-Phase B, INTEX-B) and a posteriori was statistically significant and the a priori might underestimate the CO emission flux by 37 %. A correction factor (a posteriori/a priori) of 1.26 was suggested for CO emission in China in spring. The spatial distribution and magnitude of the CO emission flux were comparable to the latest regional emission inventory in Asia (REAS2.0). Nevertheless, further evaluation is still necessary in view of the larger uncertainties for both the analytical inversion and the bottom-up statistical approaches.

Penrod, A., Y. Zhang, K. Wang, S.-Y. Wu, and L. R. Leung (2014), Impacts of future climate and emission changes on U.S. air quality, Atmospheric Environment, 89, 533547, doi:10.1016/j.atmosenv.2014.01.001.
Changes in climate and emissions will affect future air quality. In this work, simulations of regional air quality during current (20012005) and future (20262030) winter and summer are conducted with the newly released CMAQ version 5.0 to examine the impacts of simulated future climate and anthropogenic emission projections on air quality over the U.S. Current meteorological and chemical predictions are evaluated against observations to assess the model’s capability in reproducing the seasonal differences. WRF and CMAQ capture the overall observational spatial patterns and seasonal differences. Biases in model predictions are attributed to uncertainties in emissions, boundary conditions, and limitations in model physical and chemical treatments as well as the use of a coarse grid resolution. Increased temperatures (up to 3.18 °C) and decreased ventilation (up to 157 m in planetary boundary layer height) are found in both future winter and summer, with more prominent changes in winter. Increases in future temperatures result in increased isoprene and terpene emissions in winter and summer, driving the increase in maximum 8-h average O3 (up to 5.0 ppb) over the eastern U.S. in winter while decreases in NOx emissions drive the decrease in O3 over most of the U.S. in summer. Future PM2.5 concentrations in winter and summer and many of its components decrease due to decreases in primary anthropogenic emissions and the concentrations of secondary anthropogenic pollutants as well as increased precipitation in winter. Future winter and summer dry and wet deposition fluxes are spatially variable and increase with decreasing surface resistance and precipitation, respectively. They decrease with a decrease in ambient particulate concentrations. Anthropogenic emissions play a more important role in summer than in winter for future O3 and PM2.5 levels, with a dominance of the effects of significant emission reductions over those of climate change on future PM2.5 levels.

Pommrich, R., R. Müller, J.-U. Grooß, P. Konopka, F. Ploeger, B. Vogel, M. Tao, C. M. Hoppe, G. Günther, N. Spelten, L. Hoffmann, H.-C. Pumphrey, S. Viciani, F. D’Amato, C. M. Volk, P. Hoor, H. Schlager, and M. Riese (2014), Tropical troposphere to stratosphere transport of carbon monoxide and long-lived trace species in the Chemical Lagrangian Model of the Stratosphere (CLaMS), Geosci. Model Dev., 7(6), 28952916, doi:10.5194/gmd-7-2895-2014.
Variations in the mixing ratio of trace gases of tropospheric origin entering the stratosphere in the tropics are of interest for assessing both troposphere to stratosphere transport fluxes in the tropics and the impact of these transport fluxes on the composition of the tropical lower stratosphere.  Anomaly patterns of carbon monoxide (CO) and long-lived tracers in the lower tropical stratosphere allow conclusions about the rate and the variability of tropical upwelling to be drawn.  Here, we present a simplified chemistry scheme for the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the simulation, at comparatively low numerical cost, of CO, ozone, and long-lived trace substances (CH4, N2O, CCl3F (CFC-11), CCl2F2 (CFC-12), and CO2) in the lower tropical stratosphere.  For the long-lived trace substances, the boundary conditions at the surface are prescribed based on ground-based measurements in the lowest model level.  The boundary condition for CO in the lower troposphere (below about 4 km) is deduced from MOPITT measurements. Due to the lack of a specific representation of mixing and convective uplift in the troposphere in this model version, enhanced CO values, in particular those resulting from convective outflow are underestimated. However, in the tropical tropopause layer and the lower tropical stratosphere, there is relatively good agreement of simulated CO with in situ measurements (with the exception of the TROCCINOX campaign, where CO in the simulation is biased low ≈1015 ppbv).  Further, the model results (and therefore also the ERA-Interim winds, on which the transport in the model is based) are of sufficient quality to describe large scale anomaly patterns of CO in the lower stratosphere.  In particular, the zonally averaged tropical CO anomaly patterns (the so called “tape recorder” patterns) simulated by this model version of CLaMS are in good agreement with observations, although the simulations show a too rapid upwelling compared to observations as a consequence of the overestimated vertical velocities in the ERA-Interim reanalysis data set.  Moreover, the simulated tropical anomaly patterns of N2O are in good agreement with observations. In the simulations, anomaly patterns of CH4 and CFC-11 were found to be very similar to those of N2O; for all long-lived tracers, positive anomalies are simulated because of the enhanced tropical upwelling in the easterly shear phase of the quasi-biennial oscillation.

Rosenfeld, D., M. O. Andreae, A. Asmi, M. Chin, G. de Leeuw, D. P. Donovan, R. Kahn, S. Kinne, N. Kivekäs, M. Kulmala, W. Lau, K. S. Schmidt, T. Suni, T. Wagner, M. Wild, and J. Quaas (2014), Global observations of aerosol-cloud-precipitation-climate interactions, Rev. Geophys., 2013RG000441, doi:10.1002/2013RG000441.
Cloud drop condensation nuclei (CCN) and ice nuclei (IN) particles determine to a large extent cloud microstructure and, consequently, cloud albedo and the dynamic response of clouds to aerosol-induced changes to precipitation. This can modify the reflected solar radiation and the thermal radiation emitted to space. Measurements of tropospheric CCN and IN over large areas have not been possible and can be only roughly approximated from satellite-sensor-based estimates of optical properties of aerosols. Our lack of ability to measure both CCN and cloud updrafts precludes disentangling the effects of meteorology from those of aerosols and represents the largest component in our uncertainty in anthropogenic climate forcing. Ways to improve the retrieval accuracy include multiangle and multipolarimetric passive measurements of the optical signal and multispectral lidar polarimetric measurements. Indirect methods include proxies of trace gases, as retrieved by hyperspectral sensors. Perhaps the most promising emerging direction is retrieving the CCN properties by simultaneously retrieving convective cloud drop number concentrations and updraft speeds, which amounts to using clouds as natural CCN chambers. These satellite observations have to be constrained by in situ observations of aerosol-cloud-precipitation-climate (ACPC) interactions, which in turn constrain a hierarchy of model simulations of ACPC. Since the essence of a general circulation model is an accurate quantification of the energy and mass fluxes in all forms between the surface, atmosphere and outer space, a route to progress is proposed here in the form of a series of box flux closure experiments in the various climate regimes. A roadmap is provided for quantifying the ACPC interactions and thereby reducing the uncertainty in anthropogenic climate forcing.

Safronov, A. N., E. V. Fokeeva, V. S. Rakitin, E. I. Grechko, and R. A. Shumsky (2014), Severe Wildfires Near Moscow, Russia in 2010: Modeling of Carbon Monoxide Pollution and Comparisons with Observations, Remote Sens., 7(1), 395429, doi:10.3390/rs70100395.
The spatial and temporal distributions of the carbon monoxide (CO) concentration were calculated with the Regional Atmospheric Modeling System and Hybrid Particle and Concentration Transport model (RAMS/HYPACT) in the provinces near Moscow during the abnormally hot summer of 2010. The forest, steppe and meadow hot spots were defined by the satellite data MCD14ML (MODIS Terra and Aqua satellite data). The calculations indicated that the surface CO concentrations from the model were two times less than the experimental data obtained from the Moscow State University (MSU) station and Zvenigorod Scientific Station (ZSS). Conversely, the total column CO concentrations obtained from the model were two to three times larger than the experimental values obtained from the Obukhov Institute of Atmospheric Physics (OIAP) and ZSS stations. The vertical transfer of pollutants was overestimated. Tentatively, it could be assumed that an aerosol influence in the model calculations is a reason for the overestimation. The comparisons between the wind speed, temperature and humidity profiles calculated in the model with the data from the standard balloon sounding exhibited good agreement. The CO total column data of the Measurements of Pollution in the Troposphere (MOPITTv5 NIR and TIR/NIR) obtained from the OIAP and ZSS stations appear more realistic than do the MOPITTv4 data. However, the surface MOPITT values of CO concentration for Moscow have the large distinction from the ground measurements. A careful proposal regarding satellite orbit optimization was made, which could improve future spectrometric measurements, such as the MOPITT, Atmospheric Infrared Sounder (AIRS) and Infrared Atmospheric Sounding Interferometer (IASI) measurements.

Srivastava, S. (2014), MOPITT total column CO over the Indian Subcontinent: Spatial variability and long term trend, in ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, vol. XL8, pp. 323327, Copernicus GmbH. [online] Available from: .

Abstract. Total column carbon monoxide (CO) concentration obtained from MOPITT (Measurement Of Pollution In The Troposphere) have been analyzed over the Indian subcontinent for a period of March, 2000 to December, 2010. Average monthly variation of columnar CO is investigated over the eastern and western coasts of India (latitude > 18&deg;N). The columnar CO concentration is found to be larger over the east coast than the west coast. The higher columnar CO concentrations (2.3&ndash;2.8 x 1018 molec/cm2) occur during November to April months over both the coastal regions. The lower columnar CO concentrations (1.6&ndash;1.7 x 1018 molec/cm2) occur during July-August months over these coastal regions when air blows from the Bay of Bengal towards the east coast and from the Arabian Sea towards the west coast. The latitudinal variations of ten year averaged columnar CO are also investigated over the eastern and western coastlines of India (23.5&deg;N to 8.5&deg;N). The latitudinal gradient is stronger over the eastern coast (3.2 x 1016 molec/cm2/&deg;N) with respect to the western coast (8.6 x 1015 molec/cm2/&deg;N) due to injection of highly polluted air mass from the Indo-Gangetic Plain over the northern part of Bay of Bengal. In order to investigate the source of pollution, variation of columnar CO concentration over the 11 polluted cities situated in the Indo-Gangetic plain has been examined. Columnar CO concentrations are found to be significantly higher over the southeast Indo-Gangetic plain and show a linear decreasing tendency from southeast to northwest cities. The maximum columnar CO concentration is observed over Patna (~ 2.48 x 1018 molec/cm2) and minimum over Multan (~ 2.19 x 1018 molec/cm2). This indicates that south-eastern part of Indo-Gangetic plain is mainly contributing towards enhancement in columnar CO concentration over the eastern coast. Columnar CO concentration showed an increasing trend during 2000 to 2010 over all the 11 cities. This increasing tendency is stronger over the cities situated in the southeast part of Indo-Gangetic plain.

Stein, O., M. G. Schultz, I. Bouarar, H. Clark, V. Huijnen, A. Gaudel, M. George, and C. Clerbaux (2014), On the wintertime low bias of Northern Hemisphere carbon monoxide found in global model simulations, Atmos. Chem. Phys., 14(17), 92959316, doi:10.5194/acp-14-9295-2014.
Despite the developments in the global modelling of chemistry and of the parameterization of the physical processes, carbon monoxide (CO) concentrations remain underestimated during Northern Hemisphere (NH) winter by most state-of-the-art chemistry transport models. The consequential model bias can in principle originate from either an underestimation of CO sources or an overestimation of its sinks. We address both the role of surface sources and sinks with a series of MOZART (Model for Ozone And Related Tracers) model sensitivity studies for the year 2008 and compare our results to observational data from ground-based stations, satellite observations, and vertical profiles from measurements on passenger aircraft. In our base case simulation using MACCity (Monitoring Atmospheric Composition and Climate project) anthropogenic emissions, the near-surface CO mixing ratios are underestimated in the Northern Hemisphere by more than 20 ppb from December to April, with the largest bias of up to 75 ppb over Europe in January. An increase in global biomass burning or biogenic emissions of CO or volatile organic compounds (VOCs) is not able to reduce the annual course of the model bias and yields concentrations over the Southern Hemisphere which are too high. Raising global annual anthropogenic emissions with a simple scaling factor results in overestimations of surface mixing ratios in most regions all year round. Instead, our results indicate that anthropogenic CO and, possibly, VOC emissions in the MACCity inventory are too low for the industrialized countries only during winter and spring. Reasonable agreement with observations can only be achieved if the CO emissions are adjusted seasonally with regionally varying scaling factors. A part of the model bias could also be eliminated by exchanging the original resistance-type dry deposition scheme with a parameterization for CO uptake by oxidation from soil bacteria and microbes, which reduces the boreal winter dry deposition fluxes. The best match to surface observations, satellite retrievals, and aircraft observations was achieved when the modified dry deposition scheme was combined with increased wintertime road traffic emissions over Europe and North America (factors up to 4.5 and 2, respectively). One reason for the apparent underestimation of emissions may be an exaggerated downward trend in the Representative Concentration Pathway (RCP) 8.5 scenario in these regions between 2000 and 2010, as this scenario was used to extrapolate the MACCity emissions from their base year 2000. This factor is potentially amplified by a lack of knowledge about the seasonality of emissions. A methane lifetime of 9.7 yr for our basic model and 9.8 yr for the optimized simulation agrees well with current estimates of global OH, but we cannot fully exclude a potential effect from errors in the geographical and seasonal distribution of OH concentrations on the modelled CO.

Sukitpaneenit, M., and N. T. K. Oanh (2014), Satellite monitoring for carbon monoxide and particulate matter during forest fire episodes in Northern Thailand, Environ. Monit. Assess., 186(4), 24952504, doi:10.1007/s10661-013-3556-x.
This study explored the use of satellite data to monitor carbon monoxide (CO) and particulate matter (PM) in Northern Thailand during the dry season when forest fires are known to be an important cause of air pollution. Satellite data, including Measurement of Pollution in the Troposphere (MOPITT) CO, Moderate Resolution Imaging Spectroradiometer aerosol optical depth (MODIS AOD), and MODIS fire hotspots, were analyzed with air pollution data measured at nine automatic air quality monitoring stations in the study area for February-April months of 2008-2010. The correlation analysis showed that daily CO and PM with size below 10 mu m (PM10) were associated with the forest fire hotspot counts, especially in the rural areas with the maximum correlation coefficient (R) of 0.59 for CO and 0.65 for PM10. The correlations between MODIS AOD and PM10, between MOPITT CO and CO, and between MODIS AOD and MOPITT CO were also analyzed, confirming the association between these variables. Two forest fire episodes were selected, and the dispersion of pollution plumes was studied using the MOPITT CO total column and MODIS AOD data, together with the surface wind vectors. The results showed consistency between the plume dispersion, locations of dense hotspots, ground monitoring data, and prevalent winds. The satellite data were shown to be useful in monitoring the regional transport of forest fire plumes.

Wang, K., Y. Zhang, K. Yahya, S.-Y. Wu, and G. Grell (2014), Implementation and Initial Application of New Chemistry-Aerosol Options in WRF/Chem for Simulating Secondary Organic Aerosols and Aerosol Indirect Effects for Regional Air Quality, Atmospheric Environment, doi:10.1016/j.atmosenv.2014.12.007. [online] Available from: .
Atmospheric aerosols play important roles in affecting regional meteorology and air quality through aerosol direct and indirect effects. Two new chemistry-aerosol options have been developed in WRF/Chem v3.4.1 by incorporating the 2005 Carbon Bond (CB05) mechanism and coupling it with the existing aerosol module MADE with SORGAM and VBS modules for simulating secondary organic aerosol (SOA), aqueous-phase chemistry in both large scale and convective clouds, and aerosol feedback processes (hereafter CB05-MADE/SORGAM and CB05-MADE/VBS). As part of the Air Quality Model Evaluation International Initiative (AQMEII) Phase II model intercomparison that focuses on online-coupled meteorology and chemistry models, WRF/Chem with the two new options is applied to an area over North America for July 2006 episode. The simulations with both options can reproduce reasonably well most of the observed meteorological variables, chemical concentrations, and aerosol/cloud properties. Compared to CB05-MADE/SORGAM, CB05-MADE/VBS greatly improves the model performance for organic carbon (OC) and PM2.5, reducing NMBs from -81.2% to -13.1% and from -26.1% to -15.6%, respectively. Sensitivity simulations show that the aerosol indirect effects (including aqueous-phase chemistry) can reduce the net surface solar radiation by up to 53 W m-2 with a domainwide mean of 12 W m-2 through affecting cloud formation and radiation scattering and reflection by increasing cloud cover, which in turn reduce the surface temperature, NO2 photolytic rate, and planetary boundary layer height by up to 0.3 °C, 3.7 min-1, and 64 m, respectively. The changes of those meteorological variables further impact the air quality through the complex chemistry-aerosol-cloud-radiation interactions by reducing O3 mixing ratios by up to 5.0 ppb. The results of this work demonstrate the importance of aerosol indirect effects on the regional climate and air quality. For comparison, the impacts of aerosol direct effects on both regional meteorology and air quality are much lower with the reduction on net surface solar radiation only by up to 17 W m-2 and O3 only by up to 1.4 ppb, which indicates the importance and necessity to accurately represent the aerosol indirect effects in the online-couple regional models.

Worden, H. M., M. N. Deeter, D. P. Edwards, J. Gille, J. Drummond, L. K. Emmons, G. Francis, and S. Martínez-Alonso (2014), 13 years of MOPITT operations: lessons from MOPITT retrieval algorithm development, Ann. Geophys., 56(0), doi:10.4401/ag-6330. [online] Available from:
The Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra platform has now acquired over thirteen years of global tropospheric carbon monoxide (CO) observations, forming the longest satellite record for an important pollutant. MOPITT products are routinely exploited for characterizing CO sources and for analyzing air quality. For retrieving CO concentrations in the lower troposphere, MOPITT is equipped with both thermal-infrared and near-infrared channels.

Yoon, J., and A. Pozzer (2014), Model-simulated trend of surface carbon monoxide for the 20012010 decade, Atmos. Chem. Phys., 14(19), 1046510482, doi:10.5194/acp-14-10465-2014.
We present decadal trend estimates of surface carbon monoxide (CO) simulated using the atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC; ECHAM5 and MESSy stand for fifth-generation European Centre Hamburg general circulation model and Modular Earth Submodel System, respectively) based on the emission scenarios Representative Concentration Pathways (RCP) 8.5 for anthropogenic activity and Global Fire Emissions Database (GFED) v3.1 for biomass burning from 2001 through 2010. The spatial distribution of the modeled surface CO is evaluated with monthly data from the Measurements Of Pollution In The Troposphere (MOPITT) thermal infrared product. The global means of correlation coefficient and relative bias for the decade 20012010 are 0.95 and −4.29%, respectively. We also find a reasonable correlation (R = 0.78) between the trends of EMAC surface CO and full 10-year monthly records from ground-based observation (World Data Centre for Greenhouse Gases, WDCGG). Over western Europe, eastern USA, and northern Australia, the significant decreases in EMAC surface CO are estimated at −35.5 ± 5.8, −59.6 ± 9.1, and −13.7 ± 9.5 ppbv decade−1, respectively. In contrast, the surface CO increases by +8.9 ± 4.8 ppbv decade−1 over southern Asia. A high correlation (R = 0.92) between the changes in EMAC-simulated surface CO and total emission flux shows that the significant regional trends are attributed to the changes in primary and direct emissions from both anthropogenic activity and biomass burning.

Yumimoto, K., I. Uno, and S. Itahashi (2014), Long-term inverse modeling of Chinese CO emission from satellite observations, Environ. Pollut., 195, 308318, doi:10.1016/j.envpol.2014.07.026.
Carbon monoxide (CO) emissions in China in 2005-2010 were estimated by inversion, using the Green’s function method from vertical CO profiles derived from MOPITT Version 5 satellite data and a tagged CO simulation, and validated with independent in situ observations from the World Data Centre for Greenhouse Gases. Modeling with a posteriori emission successfully reproduced CO outflow from the continent to the East China Sea, Sea of Japan, and Japanese islands during winter and spring, and compensated for underestimates in central and eastern China in summer. A posteriori emissions showed large seasonal variations in which December and March emissions were on average 23% larger than August emissions, consistent with other studies. Estimated Chinese CO emissions were 184.4, 173.1, 184.6, 158.4, 157.4, and 157.3 Tg/year for 2005-2010, respectively. The decrease after 2007 is partly attributed to Chinese socioeconomic conditions and improved combustion efficiency. (C) 2014 Elsevier Ltd. All rights reserved.

Zoogman, P., D. J. Jacob, K. Chance, H. M. Worden, D. P. Edwards, and L. Zhang (2014), Improved monitoring of surface ozone by joint assimilation of geostationary satellite observations of ozone and CO, Atmospheric Environment, 84, 254261, doi:10.1016/j.atmosenv.2013.11.048.
Future geostationary satellite observations of tropospheric ozone aim to improve monitoring of surface ozone air quality. However, ozone retrievals from space have limited sensitivity in the lower troposphere (boundary layer). Data assimilation in a chemical transport model can propagate the information from the satellite observations to provide useful constraints on surface ozone. This may be aided by correlated satellite observations of carbon monoxide (CO), for which boundary layer sensitivity is easier to achieve. We examine the potential of concurrent geostationary observations of ozone and CO to improve constraints on surface ozone air quality through exploitation of ozoneCO model error correlations in a joint data assimilation framework. The hypothesis is that model transport errors diagnosed for CO provide information on corresponding errors in ozone. A paired-model analysis of ozoneCO error correlations in the boundary layer over North America in summer indicates positive error correlations in continental outflow but negative regional-scale error correlations over land, the latter reflecting opposite sensitivities of ozone and CO to boundary layer depth. Aircraft observations from the ICARTT campaign are consistent with this pattern but also indicate strong positive error correlations in fine-scale pollution plumes. We develop a joint ozoneCO data assimilation system and apply it to a regional-scale Observing System Simulation Experiment (OSSE) of the planned NASA GEO-CAPE geostationary mission over North America. We find substantial benefit from joint ozoneCO data assimilation in informing US ozone air quality if the instrument sensitivity for CO in the boundary layer is greater than that for ozone. A high-quality geostationary measurement of CO could potentially relax the requirements for boundary layer sensitivity of the ozone measurement. This is contingent on accurate characterization of ozoneCO error correlations. A finer-resolution data assimilation system resolving the urban scale would need to account for the change in sign of the ozoneCO error correlations between urban pollution plumes and the regional atmosphere.


Barré, J., L. El Amraoui, P. Ricaud, W. A. Lahoz, J.-L. Attié, V.-H. Peuch, B. Josse, and V. Marécal (2013), Diagnosing the transition layer at extratropical latitudes using MLS O3 and MOPITT CO analyses, Atmos. Chem. Phys., 13(14), 72257240, doi:10.5194/acp-13-7225-2013.
The behavior of the extratropical transition layer (ExTL) is investigated using a chemistry transport model (CTM) and analyses derived from assimilation of MLS (Microwave Limb Sounder) O-3 and MOPITT (Measurements Of Pollution In The Troposphere) CO data. We firstly focus on a stratosphere-troposphere exchange (STE) case study that occurred on 15 August 2007 over the British Isles (50 degrees N, 10 degrees W). We evaluate the effect of data assimilation on the O-3-CO correlations. It is shown that data assimilation disrupts the relationship in the transition region. When MLS O-3 is assimilated, CO and O-3 values are not consistent between each other, leading to unphysical correlations at the STE location. When MLS O-3 and MOPITT CO assimilated fields are taken into account in the diagnostics the relationship happens to be more physical. We then use O-3-CO correlations to quantify the effect of data assimilation on the height and depth of the ExTL. When the free-model run O-3 and CO fields are used in the diagnostics, the ExTL distribution is found 1.1 km above the thermal tropopause and is 2.6 km wide (2 sigma). MOPITT CO analyses only slightly sharpen (by -0.02 km) and lower (by -0.2 km) the ExTL distribution. MLS O-3 analyses provide an expansion (by +0.9 km) of the ExTL distribution, suggesting a more intense O-3 mixing. However, the MLS O-3 analyses ExTL distribution shows a maximum close to the thermal tropopause and a mean location closer to the thermal tropopause (+0.45 km). When MLS O-3 and MOPITT CO analyses are used together, the ExTL shows a mean location that is the closest to the thermal tropopause (+0.16 km). We also extend the study at the global scale on 15 August 2007 and for the month of August 2007. MOPITT CO analyses still show a narrower chemical transition between stratosphere and troposphere than the free-model run. MLS O-3 analyses move the ExTL toward the troposphere and broaden it. When MLS O-3 analyses and MOPITT CO analyses are used together, the ExTL matches the thermal tropopause poleward of 50 degrees.

Calle, A., P. Salvador, and F. González-Alonso (2013), Study of the impact of wildfire emissions, through MOPITT total CO column, at different spatial scales, International Journal of Remote Sensing, 34(910), 33973415, doi:10.1080/01431161.2012.716534.
The estimation of total carbon monoxide (CO) column has been identified as essential to improve our understanding of its role in the global climate system. The Earth Observing System (EOS) Science Steering Committee and the World Meteorological Organization (WMO) has suggested that a satellite-borne CO sensor, which would operate for extended periods, would be useful for that task. Measurements of Pollution in the Troposphere (MOPITT), on board the Terra spacecraft, is a correlation radiometer for estimating CO vertical profiles and total CO column in the lower atmosphere, through the thermal radiance received in the 4.7 μm spectral region. One of the main sources of CO in the atmosphere is the fires and global biomass-burning emissions that are produced when combustion is not complete, especially in the smouldering phase. This article presents a methodology based on a Fourier technique and spatial analysis in order to estimate the total CO column contribution of wildfires at three different spatial scales. First, in a seasonal study, a Mediterranean country (Spain) is selected, and the main regions affected by fire during four years in the summer season are analysed. Second, in order to estimate CO emissions at a local scale, a large fire (in Spain) and a cluster of fires (in North China) are selected. Third, for a global study at large scale and for comparing with CO and carbon dioxide (CO2) data from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), locations in North China, equatorial Africa, and Amazonia are selected. Results obtained show that MOPITT data are suitable to assess and to discriminate CO emissions at local spatial scales. Finally, a qualitative agreement between CO behaviour obtained by MOPITT and CO and CO2 obtained by SCIAMACHY is found.

Cheng, L., B. Wen-Guang, Z. Xing-Ying, and Z. Peng (2013), An improvement of retrieving carbon monoxide from SCIAMACHY Part I: with respect to the instrumental issues, Chinese J. Geophys.-Chinese Ed., 56(3), 758769, doi:10.6038/cjg20130305.
SCIAMACHY on board the European ENVISAT satellite is the only one spectrometer, which could quantitatively determine the total column densities of the greenhouse gases CO2, CH4, as well as of CO from near-infrared spectral band. Compared to other thermal infrared satellite (MOPITT, IASI, AIRS, etc.), SCIAMACHY is more sensitive to low atmosphere where the strong source are located. However, the CO retrieval turned out not only to be a challenging task from a spectroscopic point of view, but also complicated by a serious instrument issue, the ice layer deposit on the SCIAMACHY near-infrared channels. This deposit ice layer yields systematic biases on SCIAMACHY CO VCD measurements, which are up to 100% and not only depend on location, but also vary with time. The accurate correction is essential, since inaccurate corrections will lead to a wrong interpretation of the results. Currently, there are several correction methods. developed by different groups, but no consistent time series could be retrieved so far. In this paper, similar correction procedures are developed and validated at first. In addition to the existing correction methods, a completely new correction method is then developed. To validate the new SCIAMACHY CO product, we compare it with the independent ground based FTIR measurements. After the correction, the agreement of the seasonal patterns greatly improves; the relative differences between the two dataset reduce from 60% to less than 5%, which make the precisely satellite measurements possible. The results not only could improve our knowledge of the sources and sinks, but most importantly, also could help government formulate carbon reduction rules, effectively reduce the greenhouse effect.

Deeter, M. N., S. Martínez-Alonso, D. P. Edwards, L. K. Emmons, J. C. Gille, H. M. Worden, J. V. Pittman, B. C. Daube, and S. C. Wofsy (2013), Validation of MOPITT Version 5 thermal-infrared, near-infrared, and multispectral carbon monoxide profile retrievals for 20002011, Journal of Geophysical Research: Atmospheres, n/a-n/a, doi:10.1002/jgrd.50272.
Validation results are reported for the MOPITT (Measurements of Pollution in the Troposphere) “Version 5” (V5) product for tropospheric carbon monoxide (CO) and are compared to results for the “Version 4” product. The V5 retrieval algorithm introduces (1) a method for reducing retrieval bias drift associated with long-term instrumental degradation, (2) a more exact representation of the effects of random errors in the radiances and, for the first time, (3) the use of MOPITT’s near-infrared (NIR) radiances to complement the thermal-infrared (TIR) radiances. Exploiting TIR and NIR radiances together facilitates retrievals of CO in the lowermost troposphere. V5 retrieval products based (1) solely on TIR measurements, (2) solely on NIR measurements and (3) on both TIR and NIR measurements are separately validated and analyzed. Actual retrieved CO profiles and total columns are compared with equivalent retrievals based on in situ measurements from (1) routine NOAA aircraft sampling mainly over North America and (2) the “HIAPER Pole to Pole Observations” (HIPPO) field campaign. Particular attention is focused on the long-term stability and geographical uniformity of the retrieval errors. Results for the retrieved total column clearly indicate reduced temporal bias drift in the V5 products compared to the V4 product, and do not exhibit a positive bias in the Southern Hemisphere, which is evident in the V4 product.

He, H., J. W. Stehr, J. C. Hains, D. J. Krask, B. G. Doddridge, K. Y. Vinnikov, T. P. Canty, K. M. Hosley, R. J. Salawitch, H. M. Worden, and R. R. Dickerson (2013), Trends in emissions and concentrations of air pollutants in the lower troposphere in the Baltimore/Washington airshed from 1997 to 2011, Atmos. Chem. Phys., 13(15), 78597874, doi:10.5194/acp-13-7859-2013.
Trends in the composition of the lower atmosphere (01500 m altitude) and surface air quality over the Baltimore/Washington area and surrounding states were investigated for the period from 1997 to 2011. We examined emissions of ozone precursors from monitors and inventories as well as ambient ground-level and aircraft measurements to characterize trends in air pollution. The US EPA Continuous Emissions Monitoring System (CEMS) program reported substantial decreases in emission of summertime nitrogen oxides (NOx) from power plants, up to ∼80% in the mid-Atlantic States. These large reductions in emission of NOx are reflected in a sharp decrease of ground-level concentrations of NOx starting around 2003. The decreasing trend of tropospheric column CO observed by aircraft is ∼0.8 Dobson unit (DU) per year, corresponding to ∼35 ppbv yr−1 in the lower troposphere (the surface to 1500 m above ground level). Satellite observations of long-term, near-surface CO show a ∼40% decrease over western Maryland between 2000 and 2011; the same magnitude is indicated by aircraft measurements above these regions upwind of the Baltimore/Washington airshed. With decreasing emissions of ozone precursors, the ground-level ozone in the Baltimore/Washington area shows a 0.6 ppbv yr−1 decrease in the past 15 yr. Since photochemical production of ozone is substantially influenced by ambient temperature, we introduce the climate penalty factor (CPF) into the trend analysis of long-term aircraft measurements. After compensating for inter-annual variations in temperature, historical aircraft measurements indicate that the daily net production of tropospheric ozone over the Baltimore/Washington area decreased from ∼20 ppbv day−1 in the late 1990s to ∼7 ppbv day−1 in the early 2010s during ozone season. A decrease in the long-term column ozone is observed as ∼0.2 DU yr−1 in the lowest 1500 m, corresponding to an improvement of ∼1.3 ppbv yr−1. Our aircraft measurements were conducted on days when severe ozone pollution was forecasted, and these results represent the decreasing trend in high ozone events over the past 15 yr. Back trajectory cluster analysis demonstrates that emissions of air pollutants from Ohio and Pennsylvania through Maryland influence the column abundances of downwind ozone in the lower atmosphere. The trends in air pollutants reveal the success of regulations implemented over the past decades and the importance of region-wide emission controls in the eastern United States.

Huang, M., K. W. Bowman, G. R. Carmichael, R. Bradley Pierce, H. M. Worden, M. Luo, O. R. Cooper, I. B. Pollack, T. B. Ryerson, and S. S. Brown (2013a), Impact of Southern California anthropogenic emissions on ozone pollution in the mountain states: Model analysis and observational evidence from space, Journal of Geophysical Research: Atmospheres, 118(22), 12,784-12,803, doi:10.1002/2013JD020205.
The impact of Southern California (SoCal) anthropogenic emissions on ozone (O3) in the mountain states in May 2010 is studied using the Sulfur Transport and Deposition Model. We identified two to six major transport events from SoCal to different subregions in the mountain states, with transport times of 02 days indicated by trajectories, time-lag correlations, and forward/adjoint sensitivities. Based on forward sensitivity analysis, the contributions from SoCal anthropogenic emissions to the monthly mean daily maximum 8 h average (MDA8) surface O3 in the mountain states decrease with distance from SoCal, and they range from <1 ppbv (in Wyoming) to 15 ppbv (in western Arizona). These contributions show medium (>0.6) to strong (>0.8) positive correlations with the modeled total surface MDA8 O3. For the most strongly affected states of Arizona and New Mexico, these contributions have median values of 3, 2, 5, and 15 ppbv when the total surface MDA8 O3 exceeded thresholds of 60, 65, 70, and 75 ppbv, respectively. Surface MDA8 O3 values in SoCal show strong nonlinear responses to varied magnitudes of perturbation (e.g., ±50% and 100%) in SoCal anthropogenic emissions and weak nonlinear responses in the mountain states. Case studies show that different scales of transport (e.g., trans-Pacific, stratospheric intrusions, and interstate) can be dynamically and chemically coupled and simultaneously affect O3 in the mountain states when the meteorological conditions are favorable. During some of these strong transport periods, the contributions of SoCal anthropogenic emissions to hourly O3 in the mountain states can exceed 20 ppbv, close to the magnitude during a summer event reported by Langford et al. (2010). Satellite observations from the Tropospheric Emission Spectrometer and the Measurements of Pollution in the Troposphere multispectral retrievals qualitatively demonstrate large and interstate scales of transport, respectively. Suggestions are made for future satellite missions to measure O3 with improved spatial coverage, temporal frequency, and near-surface sensitivity to provide better observational constraints on interstate pollution transport studies.

Huang, X., X.-X. Huang, T.-J. Wang, B.-L. Zhuang, S. Li, M. Xie, Y. Han, X.-Q. Yang, J.-N. Sun, A.-J. Ding, and C.-B. Fu (2013b), Observation and analysis of urban upper atmospheric carbon monoxide in Nanjing, China Environmental Science, 33(9), 15771584.
Using the continuous measurements of carbon monoxide (CO) at Urban Atmospheric Environment Observation Station (32 degree 03’20"N, 118 degree 46’32"E) of Nanjing University from January to December 2011, the concentration characteristics of CO was investigated. Backward trajectory and cluster analysis were used to isolate air masses reaching Nanjing with different chemical characteristics. The satellite data from MOPITT was used to analyze vertical distribution of CO at Nanjing. Studies revealed that the annual mean concentration of CO was (757.5 plus or minus 410.5) x 10 super(-9). CO exhibited significant diurnal variation with the peak around 8:00am and the trough around 16:00pm. Diurnal variations in four seasons were different, which was the largest in spring and the smallest in summer. As to weekly variation of CO, the highest concentration occurred on Friday. There was an obviously seasonal cycle of CO, with maximum in January and minimum in June. Backward trajectories arriving at Nanjing were divided into 6categories using HYSPLIT4model and cluster technique. The results indicated that CO level in the air masses from south of Jiangsu Province, Zhejiang Province and Shanghai City was the highest. The air masses from Siberian Plateau, fast transport to Nanjing, were the cleanest. The vertical variation of CO in summer was different from that in other three seasons at Nanjing. Compared with the ground-based observation, retrieved CO concentration near surface was significantly lower.

Inness, A., F. Baier, A. Benedetti, I. Bouarar, S. Chabrillat, H. Clark, C. Clerbaux, P. Coheur, R. J. Engelen, Q. Errera, J. Flemming, M. George, C. Granier, J. Hadji-Lazaro, V. Huijnen, D. Hurtmans, L. Jones, J. W. Kaiser, J. Kapsomenakis, K. Lefever, J. Leitao, M. Razinger, A. Richter, M. G. Schultz, A. J. Simmons, M. Suttie, O. Stein, J.-N. Thepaut, V. Thouret, M. Vrekoussis, and C. Zerefos (2013), The MACC reanalysis: an 8 yr data set of atmospheric composition, Atmos. Chem. Phys., 13(8), 40734109, doi:10.5194/acp-13-4073-2013.
An eight-year long reanalysis of atmospheric composition data covering the period 2003-2010 was constructed as part of the FP7-funded Monitoring Atmospheric Composition and Climate project by assimilating satellite data into a global model and data assimilation system. This reanalysis provides fields of chemically reactive gases, namely carbon monoxide, ozone, nitrogen oxides, and formaldehyde, as well as aerosols and greenhouse gases globally at a horizontal resolution of about 80 km for both the troposphere and the stratosphere. This paper describes the assimilation system for the reactive gases and presents validation results for the reactive gas analysis fields to document the data set and to give a first indication of its quality. Tropospheric CO values from the MACC reanalysis are on average 10-20% lower than routine observations from commercial aircrafts over airports through most of the troposphere, and have larger negative biases in the boundary layer at urban sites affected by air pollution, possibly due to an underestimation of CO or precursor emissions. Stratospheric ozone fields from the MACC reanalysis agree with ozonesondes and ACE-FTS data to within +/-10% in most seasons and regions. In the troposphere the reanalysis shows biases of -5% to +10% with respect to ozonesondes and aircraft data in the extratropics, but has larger negative biases in the tropics. Area-averaged total column ozone agrees with ozone fields from a multi-sensor reanalysis data set to within a few percent. NO2 fields from the reanalysis show the right seasonality over polluted urban areas of the NH and over tropical biomass burning areas, but underestimate wintertime NO2 maxima over anthropogenic pollution regions and overestimate NO2 in northern and southern Africa during the tropical biomass burning seasons. Tropospheric HCHO is well simulated in the MACC re-analysis even though no satellite data are assimilated. It shows good agreement with independent SCIAMACHY retrievals over regions dominated by biogenic emissions with some anthropogenic input, such as the eastern US and China, and also over African regions influenced by biogenic sources and biomass burning.

Jiang, Z., D. B. A. Jones, H. M. Worden, M. N. Deeter, D. K. Henze, J. Worden, K. W. Bowman, C. a. M. Brenninkmeijer, and T. J. Schuck (2013), Impact of model errors in convective transport on CO source estimates inferred from MOPITT CO retrievals, Journal of Geophysical Research: Atmospheres, 118(4), 20732083, doi:10.1002/jgrd.50216.
Estimates of surface fluxes of carbon monoxide (CO) inferred from remote sensing observations or free tropospheric trace gas measurements using global chemical transport models can have significant uncertainties because of discrepancies in the vertical transport in the models, which make it challenging to unequivocally relate the observations back to the surface fluxes in the models. The new Measurement of Pollution in the Troposphere (MOPITT) version 5 retrievals provide greater sensitivity to lower tropospheric CO over land relative to the previous versions and are, therefore, useful for evaluating vertical transport in models. We have assimilated the new MOPITT CO retrievals, using the Goddard Earth Observing System (GEOS)-Chem model, to study the influence of vertical transport errors on inferred CO sources. We compared the source estimates obtained by assimilating the CO profiles, the column amounts, and the surface level retrievals for JuneAugust 2006. The three different inversions produced large differences in the source estimates in regions of convection and strong CO emissions. The inversion using the CO profiles suggested an 85% increase in emissions in India/Southeast Asia, which exacerbated the model bias in the lower and middle troposphere, whereas using the surface level retrievals produced a 37% decrease in Indian/Southeast Asian emissions, which exacerbated the underestimate of CO in the upper troposphere. Globally, the inversion with the surface retrievals suggested a 22% reduction in emissions from the a priori estimate of 161 Tg CO/month (from combustion and the oxidation of biogenic volatile organic compounds), averaged in JuneAugust 2006. The analysis results were validated with independent surface CO measurements from NOAA Global Monitoring Division (GMD) network and upper troposphere CO measurements from the Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrumented Container (CARIBIC). We found that the inversion with the surface retrievals agreed best with surface CO data but produced the largest discrepancy with the CARIBIC aircraft data in the upper troposphere, suggesting the influence of vertical transport errors in the model. Our results show that the comparison of the a posteriori CO distributions obtained from the inversions using the surface and profile retrievals provides a means of characterizing the potential impact of the vertical transport biases on the source estimates and the CO distribution.

Kumar, R., M. Naja, G. G. Pfister, M. C. Barth, and G. P. Brasseur (2013), Source attribution of carbon monoxide in India and surrounding regions during wintertime, Journal of Geophysical Research: Atmospheres, 118(4), 19811995, doi:10.1002/jgrd.50134.
This study presents a CO source contribution analysis for the atmosphere of South Asia during JanuaryFebruary 2008. The approach includes into the Weather Research and Forecasting Model with Chemistry 11 CO tracers, which track CO from different source types and regions. The comparison of model results with Measurement of Pollution in the Troposphere CO retrievals shows that the model reproduces the spatial, vertical, and temporal distributions of Measurement of Pollution in the Troposphere retrievals fairly well, but generally overestimates CO retrievals in the lower troposphere. CO mixing ratios averaged over the model domain at the surface, in the planetary boundary layer, and the free troposphere are estimated as 321 ± 291, 280 ± 208, and 125 ± 27 ppbv, respectively. Model results show that wintertime CO in the boundary layer and free troposphere over India is mostly due to anthropogenic emissions and to CO inflow. In the boundary layer, the contribution from anthropogenic sources dominates (4090%), while in the free troposphere the main contribution is due to CO inflow from the lateral boundaries (5090%). Over the Arabian Sea and the Bay of Bengal, 4351% of surface CO mixing ratios come from the Indian subcontinent and 4957% from regions outside of South Asia. The anthropogenic sources in the Indo-Gangetic Plain region are found to contribute, on average, 42% and 76% to anthropogenic surface CO over the Arabian Sea and the Bay of Bengal, respectively. The anthropogenic emissions from western and southern India contribute 49% to anthropogenic surface CO over the Arabian Sea. Anthropogenic emissions contribute only up to 40% over Burma where biomass burning plays a more important role. Regional transport contributes significantly to total anthropogenic CO over southern India (41%), Burma (49%), and even exceeds the contribution from local sources in western India (58%).

Lalitaporn, P., G. Kurata, Y. Matsuoka, N. Thongboonchoo, and V. Surapipith (2013), Long-term analysis of NO2, CO, and AOD seasonal variability using satellite observations over Asia and intercomparison with emission inventories and model, Air Qual Atmos Health, 6(4), 655672, doi:10.1007/s11869-013-0205-z.
Long-term analysis of tropospheric nitrogen dioxide (NO2) columns retrieved from GOME, SCIAMACHY, OMI and GOME-2 satellites, carbon monoxide (CO) columns from MOPITT satellite, and aerosol optical depths (AODs) from MODIS satellite was performed for Southeast Asian countries including Japan and China during 19962012. The results show that significant increasing levels of tropospheric NO2 columns can be clearly observed during the study period, especially above the eastern regions of China. The cities located in different latitude zones present the seasonal cycle of NO2 columns, CO columns, and AODs differently. For the cities located around mid-latitude zone, the maximum levels of NO2 and CO columns can be observed in the winter (NovemberMarch) and the minimum in the summer (JuneSeptember). On the contrary, the maximum levels for the cities near Equator zone are revealed in dry season (JuneOctober). In the case of AODs, the maximum peaks normally occur during biomass burning season. Ground monitoring concentrations of NO2, CO, and PM10 were also comparably analyzed with satellite NO2 columns, CO columns, and AODs, respectively. Anthropogenic and biomass burning emissions were derived to investigate the consistency with satellite retrievals. The results show that satellite observations are able to capture the trend and seasonal variability of the emissions and ground concentrations. The model simulations were conducted using CMAQ model. Generally, simulated model results agree well with those retrieved from satellite measurements for spatial distribution and seasonal pattern. However, the modeled results underestimate satellite data probably due to the inaccuracy in emission inventories, the inaccuracy of spatial and temporal allocations, and the uncertainties in the satellite retrievals.

van Leeuwen, T. T., W. Peters, M. C. Krol, and G. R. van der Werf (2013), Dynamic biomass burning emission factors and their impact on atmospheric CO mixing ratios, Journal of Geophysical Research: Atmospheres, n/a-n/a, doi:10.1002/jgrd.50478.
Biomass burning is a major source of trace gases and aerosols, influencing atmospheric chemistry and climate. To quantitatively assess its impact, an accurate representation of fire emissions is crucial for the atmospheric modeling community. So far, most studies rely on static emission factors (EF) which convert estimates of dry matter burned to trace gas and aerosol emissions. These EFs are often based on the arithmetic mean of field measurements stratified by biome, neglecting the variability in time and space. Here we present global carbon monoxide (CO) emission estimates from fires based on six EF scenarios with different spatial and temporal variability, using dry matter emission estimates from the Global Fire Emissions Database (GFED). We used the TM5 model to transport these different bottom-up estimates in the atmosphere and found that including spatial and temporal variability in EFs impacted CO mixing ratios substantially. Most scenarios estimated higher CO mixing ratios (up to 40% more CO from fires during the burning season) over boreal regions compared to the GFED standard run, while a decrease ( 15%) was estimated over the continent of Africa. A comparison to atmospheric CO observations showed differences of 1020 ppb between the scenarios and systematic deviations from local observations. Although temporal correlations of specific EF scenarios improved for certain regions, an overall “best” set of EFs could not be selected. Our results provide a new set of emission estimates that can be used for sensitivity analyses and highlight the importance of better understanding spatial and temporal variability in EFs for atmospheric studies in general and specifically when using CO or aerosols concentration measurements to top-down constrain fire carbon emissions.

Lin, Y. C., C. Y. Lin, P. H. Lin, G. Engling, Y. C. Lin, Y. Y. Lan, C. W. June Chang, T. H. Kuo, W. T. Hsu, and C. C. Ting (2013), Influence of Southeast Asian biomass burning on ozone and carbon monoxide over subtropical Taiwan, Atmospheric Environment, 64, 358365, doi:10.1016/j.atmosenv.2012.09.050.
Surface ozone (O3) and carbon monoxide (CO) mixing ratios were measured at Mei-Feng (24.05 °N, 120.10 °E, 2269 m above sea level) remote mountain site between March 2009 and September 2010 to investigate the impact of regional pollution on O3 and CO. The results showed that the maximum values of both O3 and CO were found in the springtime. Backward trajectory analysis, combined with MODIS fire spots suggested that the enhanced O3 and CO in springtime could be attributed to biomass burning (BB) activities over Southeast (SE) Asia. Thirteen BB events were identified by backward trajectory analysis, MODIS fires, NCEP weather data sets and CO concentrations. Good correlation between O3 and CO was found during the BB plumes. Using the linear regression, the slope (ΔO3/ΔCO) was calculated to be 0.18 ± 0.08 (mean ± 1σ). This value was in agreement with that of 0.2 observed over the west Pacific region during the TRACE-P campaign, but was higher than those (0.110.14) of Canadian and Siberian fires. Moreover, significant enhanced O3 productivity was also found in aged BB plumes and that mixed with urban emissions from SE coastal China. To assess the net influence of SE Asian BB, the air masses from SE Asia and SE China were divided in two groups: those that passed over the fire regions (PF) and those that did not (NP). The result showed that the maximum differences between PF and NP were estimated in March with 8 ppb for O3 and 45 ppb for CO, respectively, accounting for 23% of both CO and O3 levels at Mei-Feng. Although uncertainties existed in the estimations, the significant discrepancies of O3 and CO in the two air groups suggested the air pollutants emitted by SE Asian BB could be transported and influence the air quality over subtropical Taiwan in springtime.

Liu, C., S. Beirle, T. Butler, P. Hoor, C. Frankenberg, P. Jöckel, M. Penning de Vries, U. Platt, A. Pozzer, M. G. Lawrence, J. Lelieveld, H. Tost, and T. Wagner (2013), CO profiles from SCIAMACHY observations using cloud slicing and comparison with model simulations, Atmospheric Chemistry and Physics Discussions, 13(5), 1165911688, doi:10.5194/acpd-13-11659-2013.
We apply a cloud slicing technique (CST), originally developed for Total Ozone Mapping Spectrometer (TOMS) ozone observations, to CO vertical column densities retrieved from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). CST makes use of the shielding effect of clouds and combines trace gas column measurements of cloudy pixels with different cloud heights to retrieve fractional columns aloft. Here we determine seasonal mean tropospheric CO profiles at a vertical resolution of 1 km, which is much finer than what can be obtained from thermal IR instruments. However, since both the atmospheric CO profiles and the effective cloud heights depend systematically on meteorology, the profiles retrieved from the CST have to be interpreted with care. We compare the seasonal mean SCIAMACHY CO profiles with the output from two atmospheric models sampled in the same way as the satellite observations. We find systematic differences both in the absolute values and vertical and horizontal gradients. The results indicate that vertical (re)distributions of emissions and their strengths are not well represented in the models. It seems likely that deep convective transport is underestimated.

Mallik, C., S. Lal, S. Venkataramani, M. Naja, and N. Ojha (2013), Variability in ozone and its precursors over the Bay of Bengal during post monsoon: Transport and emission effects, Journal of Geophysical Research: Atmospheres, 118(17), 10,190-10,209, doi:10.1002/jgrd.50764.
Simultaneous measurements of O3, CO, NOx, CH4, and light nonmethane hydrocarbons were made over the Bay of Bengal (BoB) during 28 October to 17 November 2010 to study the role of chemistry and dynamics. The measurements revealed large variability in O3 (11 to 60 ppbv) and CO (45 to 260 ppbv). Estimated south to north latitudinal gradients in O3 (3.95 ppbv/°) and CO (16.56 ppbv/°) were significantly higher than those observed during earlier campaigns. Hybrid Single-Particle Lagrangian Integrated Trajectory simulated back air trajectories were used to classify these measurements into pollution plumes from nearby sources (India-Bangladesh region and Southeast Asia), influenced by long-range transport and pristine marine air from the Indian Ocean. Interspecies correlations were used to identify emission signatures in these air masses, e.g., chemical proxies suggested influence of biofuel/biomass burning in NE-BoB and E-BoB air masses. Principle component analysis indicated contributions of ship emissions to NOx levels over the BoB. Influences of fire from the Myanmar and Thailand regions are shown to be the potential contributor to enhanced CO levels (>250 ppbv) over the BoB during 1415 November. Diurnal variations in surface O3 revealed effects of advection, entrainment, and photochemistry. A chemical box model simulated the photochemical buildup in O3 in polluted air masses and daytime destruction in pristine oceanic air masses.

Miyazaki, K., and H. Eskes (2013), Constraints on surface NOx emissions by assimilating satellite observations of multiple species, Geophysical Research Letters, 40(17), 47454750, doi:10.1002/grl.50894.
Surface NOx emissions are estimated by a combined assimilation of satellite observations of NO2, CO, O3, and HNO3 with a global chemical transport model. The assimilation of measurements for species other than NO2 provides additional constraints on the NOx emissions by adjusting the concentrations of the species affecting the NOx chemistry and leads to changes in the regional monthly-mean emissions of −58 to +32% and the annual total emissions of −16 to +3%. These large changes highlight that uncertainties in the model chemistry impact the quality of the emission estimates. In the inversion from NO2 observations only, NOx analysis increments occur closer to the surface. Because of the shorter residence time, larger emissions increments are required compared to the multiple species assimilation. Validation against independent observations and comparisons with the recent Regional Emission inventory in Asia version 2.1 emissions shows that the multiple species assimilation improves the chemical consistency including the relation between concentrations and the estimated emissions.

Naik, V., A. Voulgarakis, A. M. Fiore, L. W. Horowitz, J.-F. Lamarque, M. Lin, M. J. Prather, P. J. Young, D. Bergmann, P. J. Cameron-Smith, I. Cionni, W. J. Collins, S. B. Dalsøren, R. Doherty, V. Eyring, G. Faluvegi, G. A. Folberth, B. Josse, Y. H. Lee, I. A. MacKenzie, T. Nagashima, T. P. C. van Noije, D. A. Plummer, M. Righi, S. T. Rumbold, R. Skeie, D. T. Shindell, D. S. Stevenson, S. Strode, K. Sudo, S. Szopa, and G. Zeng (2013), Preindustrial to present-day changes in tropospheric hydroxyl radical and methane lifetime from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), Atmos. Chem. Phys., 13(10), 52775298, doi:10.5194/acp-13-5277-2013.
We have analysed time-slice simulations from 17 global models, participating in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), to explore changes in present-day (2000) hydroxyl radical (OH) concentration and methane (CH4) lifetime relative to preindustrial times (1850) and to 1980. A comparison of modeled and observation-derived methane and methyl chloroform lifetimes suggests that the present-day global multimodel mean OH concentration is overestimated by 5 to 10% but is within the range of uncertainties. The models consistently simulate higher OH concentrations in the Northern Hemisphere (NH) compared with the Southern Hemisphere (SH) for the present-day (2000; inter-hemispheric ratios of 1.13 to 1.42), in contrast to observation-based approaches which generally indicate higher OH in the SH although uncertainties are large. Evaluation of simulated carbon monoxide (CO) concentrations, the primary sink for OH, against ground-based and satellite observations suggests low biases in the NH that may contribute to the high northsouth OH asymmetry in the models. The models vary widely in their regional distribution of present-day OH concentrations (up to 34 %). Despite large regional changes, the multi-model global mean (mass-weighted) OH concentration changes little over the past 150 yr, due to concurrent increases in factors that enhance OH (humidity, tropospheric ozone, nitrogen oxide (NOx) emissions, and UV radiation due to decreases in stratospheric ozone), compensated by increases in OH sinks (methane abundance, carbon monoxide and non-methane volatile organic carbon (NMVOC) emissions). The large inter-model diversity in the sign and magnitude of preindustrial to present-day OH changes (ranging from a decrease of 12.7% to an increase of 14.6 %) indicate that uncertainty remains in our understanding of the long-term trends in OH and methane lifetime. We show that this diversity is largely explained by the different ratio of the change in global mean tropospheric CO and NOx burdens (1CO/1NOx, approximately represents changes in OH sinks versus changes in OH sources) in the models, pointing to a need for better constraints on natural precursor emissions and on the chemical mechanisms in the current generation of chemistry-climate models. For the 1980 to 2000 period, we find that climate warming and a slight increase in mean OH (3.5±2.2 %) leads to a 4.3±1.9% decrease in the methane lifetime. Analysing sensitivity simulations performed by 10 models, we find that preindustrial to presentday climate change decreased the methane lifetime by about four months, representing a negative feedback on the climate system. Further, we analysed attribution experiments performed by a subset of models relative to 2000 conditions with only one precursor at a time set to 1860 levels. We find that global mean OH increased by 46.4±12.2% in response to preindustrial to present-day anthropogenic NOx emission increases, and decreased by 17.3±2.3 %, 7.6±1.5 %, and 3.1±3.0% due to methane burden, and anthropogenic CO, and NMVOC emissions increases, respectively.

Nair, P. R., L. M. David, S. Aryasree, and K. Susan George (2013), Distribution of ozone in the marine boundary layer of Arabian Sea prior to monsoon: Prevailing airmass and effect of aerosols, Atmospheric Environment, 74, 1828, doi:10.1016/j.atmosenv.2013.02.049.
Surface ozone (O3) measurements were carried out in the marine environment of the Arabian Sea (AS) during the premonsoon months, AprilMay 2006, as part of the Integrated Campaign for Aerosols, gases and Radiation Budget. The O3 mixing ratio over the AS varied in the range ∼322 ppb with a mean of 13.5 ± 2 ppb. Comparatively high mixing ratios were observed over the southern AS and close to the coast. The spatial pattern did not show any evidence of transport from nearby landmass or in situ photochemistry. Longitudinally separated narrow regions of low and high O3 were seen over the southern AS. The role of aerosols in modifying the O3 concentration was examined based on the co-located measurement of aerosol mass loading, number density, size distribution and optical depth. The O3 mixing ratio showed positive correlation with aerosol loading. Over high O3 regions, large particle concentration showed significant enhancement. The role of chloride ion in depleting O3 was also investigated. The observed spatial features were compared with those measured during the earlier cruises conducted in different seasons and over various oceanic regions. A comparison has been made with the measurements over the Bay of Bengal during the same cruise.

Park, K., L. K. Emmons, Z. Wang, and J. E. Mak (2013), Large interannual variations in nonmethane volatile organic compound emissions based on measurements of carbon monoxide, Geophysical Research Letters, 40(1), 221226, doi:10.1029/2012GL052303.
We present source estimates of atmospheric carbon monoxide from nonmethane volatile organic compound (NMVOC) oxidation during a period of 8 years (19972004) using a Bayesian inversion analysis. The optimized global NMVOC-derived CO source strength indicates a change of a factor of 2 between the 19971998 strong El Niño and subsequent La Niña conditions. For comparison, the average 8 year interannual variability (IAV) is 18%. The variation of NMVOC-derived CO is closely correlated with the Oceanic Niño Index (ONI) and surface temperature. A time-lagged correlation analysis between ONI and NMVOC-derived CO inventory indicated El Niño/Southern Oscillation leads the Northern Hemisphere (NH) NMVOC-derived CO production by about 3 months earlier than the Southern Hemisphere’s (SH). The SH NMVOC-derived CO was positively correlated with the lagged-ONI (r = 0.57), while the temperature change barely influenced SH NMVOC-derived CO (r = 0.01). In the NH, temperature was more robustly correlated with NMVOC-derived CO (r = 0.58) than the lagged-ONI (r = 0.35). In particular, the extra-tropical temperature showed a strong correlation (r = 0.90) with the NH NMVOC-derived CO and suggested its primary role in controlling the interannual variability of the NH NMVOC-derived CO.

Pechony, O., D. T. Shindell, and G. Faluvegi (2013), Direct top-down estimates of biomass burning CO emissions using TES and MOPITT versus bottom-up GFED inventory, Journal of Geophysical Research: Atmospheres, n/a-n/a, doi:10.1002/jgrd.50624.
In this study, we utilize near-simultaneous observations from two sets of multiple satellite sensors to segregate Tropospheric Emission Spectrometer (TES) and Measurements of Pollution in the Troposphere (MOPITT) CO observations over active fire sources from those made over clear background. Hence, we obtain direct estimates of biomass burning CO emissions without invoking inverse modeling as in traditional top-down methods. We find considerable differences between Global Fire Emissions Database (GFED) versions 2.1 and 3.1 and satellite-based emission estimates in many regions. Both inventories appear to greatly underestimate South and Southeast Asia emissions, for example. On global scales, however, CO emissions in both inventories and in the MOPITT-based analysis agree reasonably well, with the largest bias (30%) found in the Northern Hemisphere spring. In the Southern Hemisphere, there is a one-month shift between the GFED and MOPITT-based fire emissions peak. Afternoon tropical fire emissions retrieved from TES are about two times higher than the morning MOPITT retrievals. This appears to be both a real difference due to the diurnal fire activity variations, and a bias due to the scarcity of TES data.

Pommier, M., C. A. McLinden, and M. Deeter (2013), Relative changes in CO emissions over megacities based on observations from space, Geophysical Research Letters, 40(14), 37663771, doi:10.1002/grl.50704.
Urban areas are large sources of several air pollutants, with carbon monoxide (CO) among the largest. Yet measurement from space of their CO emissions remains elusive due to its long lifetime. Here we introduce a new method of estimating relative changes in CO emissions over megacities. A new multichannel Measurements of Pollution in the Troposphere (MOPITT) CO data product, offering improved sensitivity to the boundary layer, is used to estimate this relative change over eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo, and Delhi. By combining MOPITT observations with wind information from a meteorological reanalysis, changes in the CO upwind-downwind difference are used as a proxy for changes in emissions. Most locations show a clear reduction in CO emission between 20002003 and 20042008, reaching −43% over Tehran and −47% over Baghdad. There is a contrasted agreement between these results and the MACCity and Emission Database for Global Atmospheric Research v4.2 inventories.

R’Honi, Y., L. Clarisse, C. Clerbaux, D. Hurtmans, V. Duflot, S. Turquety, Y. Ngadi, and P.-F. Coheur (2013), Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildfires, Atmos. Chem. Phys., 13(8), 41714181, doi:10.5194/acp-13-4171-2013.
In July 2010, several hundred forest and peat fires broke out across central Russia during its hottest summer on record. Here, we analyze these wildfires using observations of the Infrared Atmospheric Sounding Interferometer (IASI). Carbon monoxide (CO), ammonia (NH3) and formic acid (HCOOH) total columns are presented for the year 2010. Maximum total columns were found to be one order (for CO and HCOOH) and two orders (for NH3) of magnitude larger than typical background values. The temporal evolution of NH3 and HCOOH enhancement ratios relative to CO are presented. Evidence of secondary formation of HCOOH is found, with enhancement ratios exceeding reported emission ratios in fresh plumes. We estimate the total emitted masses for the period JulyAugust 2010 over the center of western Russia; they are 1933 Tg (CO), 0.72.6 Tg (NH3) and 0.93.9 Tg (HCOOH). For NH3 and HCOOH, these quantities are comparable to what is emitted in the course of a whole year by all extratropical forest fires.

Sahu, L. K., V. Sheel, M. Kajino, S. S. Gunthe, V. Thouret, P. Nedelec, and H. G. Smit (2013), Characteristics of tropospheric ozone variability over an urban site in Southeast Asia: A study based on MOZAIC and MOZART vertical profiles, Journal of Geophysical Research: Atmospheres, 118(15), 87298747, doi:10.1002/jgrd.50662.
The Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) profiles of O3 and CO were analyzed to study their variation in the troposphere over Bangkok. Mixing ratios of O3 and CO were enhanced in planetary boundary layer (PBL) being highest in winter followed by summer and wet seasons. The daytime profiles of O3 show higher values compared to nighttime observations in PBL region, but little differences were observed in the free troposphere. The decreasing mixing ratios of O3 in the lower and upper troposphere were associated with shallow and deep convections, respectively. Back trajectory and fire count data indicate that the seasonal variations in trace gases were caused mainly by the regional shift in long-range transport and biomass-burning patterns. In wet season, flow of oceanic air and negligible presence of local biomass burning resulted in lowest O3 and CO, while their high levels in dry season were due to extensive biomass burning and transport of continental air masses. The Model for Ozone and Related Chemical Tracers (MOZART) underestimated both O3 and CO in the PBL region but overestimated these in the free troposphere. Simulations of O3 and CO also show the daytime/nighttime differences but do not capture several key features observed in the vertical distributions. The observed and simulated values of O3 and CO during SeptemberNovember 2006 were significantly higher than the same period of 2005. The year-to-year differences were mainly due to El Niño-led extensive fires in Indonesia during 2006 but normal condition during 2005.

Shim, C., J. Lee, and Y. Wang (2013), Effect of continental sources and sinks on the seasonal and latitudinal gradient of atmospheric carbon dioxide over East Asia, Atmospheric Environment, 79, 853860, doi:10.1016/j.atmosenv.2013.07.055.
Abstract Here we demonstrate the sharp seasonal and latitudinal gradient of atmospheric CO2 over East Asia, where there are relatively few ground-based observations. The Greenhouse gases Observing SATellite (GOSAT) column-averaged dry air CO2 mole fraction (xCO2) retrieved by NASA’s Atmospheric CO2 Observations from Space (ACOS) (20092011) program and GEOS-Chem nested-grid CO2 results are used. The strong anthropogenic emissions mainly from China and intensive vegetation uptake from northeastern Asia lead to a clear seasonal change of the xCO2 between spring maximum and summer minimum (&gt;10 ppm). In particular, the steep latitudinal gradient of summer time xCO2 by 35 ppm in the vicinity of the Korean Peninsula (32°N-44°N) is likely attributed to the large difference in CO2 fluxes among industry/cities, northeastern forests and the northwest Pacific region. This study represents the current progress to understand sub-continental scale atmospheric CO2 variabilities with recent satellite retrievals and nested-grid modeling.

Shindell, D. T., O. Pechony, A. Voulgarakis, G. Faluvegi, L. Nazarenko, J.-F. Lamarque, K. Bowman, G. Milly, B. Kovari, R. Ruedy, and G. A. Schmidt (2013), Interactive ozone and methane chemistry in GISS-E2 historical and future climate simulations, Atmos. Chem. Phys., 13(5), 26532689, doi:10.5194/acp-13-2653-2013.
Changes in climate and emissions will affect future air quality. In this work, simulations of regional air quality during current (20012005) and future (20262030) winter and summer are conducted with the newly released CMAQ version 5.0 to examine the impacts of simulated future climate and anthropogenic emission projections on air quality over the U.S. Current meteorological and chemical predictions are evaluated against observations to assess the model’s capability in reproducing the seasonal differences. WRF and CMAQ capture the overall observational spatial patterns and seasonal differences. Biases in model predictions are attributed to uncertainties in emissions, boundary conditions, and limitations in model physical and chemical treatments as well as the use of a coarse grid resolution. Increased temperatures (up to 3.18 °C) and decreased ventilation (up to 157 m in planetary boundary layer height) are found in both future winter and summer, with more prominent changes in winter. Increases in future temperatures result in increased isoprene and terpene emissions in winter and summer, driving the increase in maximum 8-h average O3 (up to 5.0 ppb) over the eastern U.S. in winter while decreases in NOx emissions drive the decrease in O3 over most of the U.S. in summer. Future PM2.5 concentrations in winter and summer and many of its components decrease due to decreases in primary anthropogenic emissions and the concentrations of secondary anthropogenic pollutants as well as increased precipitation in winter. Future winter and summer dry and wet deposition fluxes are spatially variable and increase with decreasing surface resistance and precipitation, respectively. They decrease with a decrease in ambient particulate concentrations. Anthropogenic emissions play a more important role in summer than in winter for future O3 and PM2.5 levels, with a dominance of the effects of significant emission reductions over those of climate change on future PM2.5 levels.

Silva, S. J., A. F. Arellano, and H. M. Worden (2013), Toward anthropogenic combustion emission constraints from space-based analysis of urban CO2/CO sensitivity, Geophysical Research Letters, 40(18), 49714976, doi:10.1002/grl.50954.
We explore the value of multispectral CO retrievals from NASA/Terra Measurement of Pollution In The Troposphere (MOPITT v5), along with Atmospheric CO2 Observations from Space (ACOSv2.9) CO2 retrievals from the Japan Aerospace Exploration Agency Greenhouse Gases Observing Satellite (GOSAT), for characterizing emissions from anthropogenic combustion. We use these satellite retrievals to analyze observed CO2/CO enhancement ratios (ΔCO2/ΔCO) over megacities. Since CO is coemitted with CO2 in anthropogenic combustion, the observed ΔCO2/ΔCO characterizes the general trend in combustion activity. Our analyses show patterns in ΔCO2/ΔCO that correspond well with the developed/developing status of megacities, and ΔCO2/ΔCO that agree well with available literature and emission inventories to approximately 20%. Comparisons with ΔCO2/ΔCO derived from Total Carbon Column Observing Network measurements show similar agreement, where some of the differences in observed ΔCO2/ΔCO are due to representativeness and limited GOSAT data. Our results imply potential constraints in anthropogenic combustion from GOSAT/MOPITT, particularly in augmenting our carbon monitoring systems.

Sitnov, S. A., and I. I. Mokhov (2013), Water-vapor content in the atmosphere over European Russia during the summer 2010 fires, Izv. Atmos. Ocean. Phys., 49(4), 380394, doi:10.1134/S0001433813040099.
We study the water vapor (WV) content over European Russia (ER) during the period of forest and peatbog fires in JulyAugust 2010 using total column water vapor observations from MODIS instruments (both Aqua and Terra platforms) as well as aerological data and NCEP/NCAR reanalysis. It is found that the spatial distribution of total column water vapor (TCWV) over ER in this period was anomalous, with the WV excess in the north of the territory and its deficit in the south of ER. The relationship between WV variations, atmospheric dynamics and the fire situation is analyzed. Along with the processes of the WV advection and evaporation we evaluate the contribution of pyrogenic emission of WV in spatial-temporal evolution of WV over ER during wildfires. The changes of water vapor at different heights in the troposphere and stratosphere are investigated. The results of a comparative analysis of WV contents during the periods of summertime atmospheric blockings in 1972 and 2010 are also presented. The near-infrared total-column precipitable water MODIS products (L3) are validated by upper-air radiosonde data.

Srivastava, S., and V. Sheel (2013), Study of tropospheric CO and O3 enhancement episode over Indonesia during Autumn 2006 using the Model for Ozone and Related chemical Tracers (MOZART-4), Atmospheric Environment, 67, 5362, doi:10.1016/j.atmosenv.2012.09.067.
An intense biomass burning event occurred over Indonesia in Autumn of 2006. We study the impact of this event on the free tropospheric abundances of carbon monoxide (CO) and ozone (O3) using MOPITT (Measurements of Pollution In The Troposphere) observations, ozonesonde measurements and 3D chemistry transport model MOZART (Model for Ozone and Related chemical Tracers). MOPITT observations showed an episode of enhanced CO in the free troposphere over the Indonesian region during OctoberNovember 2006. This feature is reproduced well by MOZART. The model mass diagnostics identifies the source of enhanced CO mixing ratio in the free troposphere (100250 ppbv) as due to convective processes. The implication of the fire plume on the vertical distribution of O3 over Kuala Lumpur has been studied. The tropospheric O3 increased over this location by 1025 ppbv during Autumn 2006 as compared to Autumn 2005 and 2007. The MOZART model simulation significantly underestimated this tropospheric O3 enhancement. The model is run both with and without Indonesian biomass burning emissions to estimate the contribution of fire emission in CO and O3 enhancement. Biomass burning emission is found to be responsible for an average increase in CO by 104 ± 56 ppbv and O3 by 5 ± 1 ppbv from surface to 100 hPa range. The model results also showed that biomass burning and El Niño related dynamical changes both contributed (∼4 ppbv12 ppbv) to the observed increase in tropospheric O3 over the Indonesian region during Autumn 2006.

Streets, D. G., T. Canty, G. R. Carmichael, B. de Foy, R. R. Dickerson, B. N. Duncan, D. P. Edwards, J. A. Haynes, D. K. Henze, M. R. Houyoux, D. J. Jacob, N. A. Krotkov, L. N. Lamsal, Y. Liu, Z. Lu, R. V. Martin, G. G. Pfister, R. W. Pinder, R. J. Salawitch, and K. J. Wecht (2013), Emissions estimation from satellite retrievals: A review of current capability, Atmospheric Environment, 77, 10111042, doi:10.1016/j.atmosenv.2013.05.051.
Abstract Since the mid-1990s a new generation of Earth-observing satellites has been able to detect tropospheric air pollution at increasingly high spatial and temporal resolution. Most primary emitted species can be measured by one or more of the instruments. This review article addresses the question of how well we can relate the satellite measurements to quantification of primary emissions and what advances are needed to improve the usability of the measurements by U.S. air quality managers. Built on a comprehensive literature review and comprising input by both satellite experts and emission inventory specialists, the review identifies several targets that seem promising: large point sources of NOx and SO2, species that are difficult to measure by other means (NH3 and CH4, for example), area sources that cannot easily be quantified by traditional bottom-up methods (such as unconventional oil and gas extraction, shipping, biomass burning, and biogenic sources), and the temporal variation of emissions (seasonal, diurnal, episodic). Techniques that enhance the usefulness of current retrievals (data assimilation, oversampling, multi-species retrievals, improved vertical profiles, etc.) are discussed. Finally, we point out the value of having new geostationary satellites like GEO-CAPE and TEMPO over North America that could provide measurements at high spatial (few km) and temporal (hourly) resolution.

Strode, S. A., and S. Pawson (2013), Detection of carbon monoxide trends in the presence of interannual variability, Journal of Geophysical Research: Atmospheres, 118(21), 12,257-12,273, doi:10.1002/2013JD020258.
Trends in fossil fuel emissions are a major driver of changes in atmospheric CO, but detection of trends in CO from anthropogenic sources is complicated by the presence of large interannual variability (IAV) in biomass burning. We use a multiyear model simulation of CO with year-specific biomass burning to predict the number of years needed to detect the impact of changes in Asian anthropogenic emissions on downwind regions. Our study includes two cases for changing anthropogenic emissions: a stepwise change of 15% and a linear trend of 3% yr−1. We first examine how well the model reproduces the observed IAV of CO over the North Pacific, since this variability impacts the time needed to detect significant anthropogenic trends. The modeled IAV over the North Pacific correlates well with that seen from the Measurements of Pollution in the Troposphere (MOPITT) instrument but underestimates the magnitude of the variability. The model predicts that a 3% yr−1 trend in Asian anthropogenic emissions would lead to a statistically significant trend in CO surface concentration in the western United States within 12 years, and accounting for Siberian boreal biomass-burning emissions greatly reduces the number of years needed for trend detection. Combining the modeled trend with the observed MOPITT variability at 500 hPa, we estimate that the 3% yr−1 trend could be detectable in satellite observations over Asia in approximately a decade. Our predicted timescales for trend detection highlight the importance of long-term measurements of CO from satellites.

Uno, I., K. Yumimoto, T. Ohara, and J.-I. Kurokawa (2013a), Analysis of long-term variation in CO concentration and emission source contribution based on a tagged transport model, Journal of Japan Society for Atmospheric Environment/Taiki Kankyo Gakkaishi, 48(3), 133139, doi:
We studied Asian scale CO source-receptor (S-R) relationship from 2004-2011 based on the tagged CO tracer model. GEOS Chem (Version 9-1-1) was used with a high-resolution Asian domain (0.5[ring] x 0.667[ring] resolution) which was 1-way nested into the global domain. Ten tagged regions were set within the Asian region. The REAS2.0 emission inventory was used as the Asian anthropogenic emission. The model results were compared with 6 ground base station and MOPITT satellite retrieval data. The model results showed clear year-by-year variations, and showed a reasonable agreement with the observations. For the observation sites within the Asian domain, the impact from the Chinese CO emission was dominant and we successfully summarized the relationship between the CO emission from the tagged regions and corresponding CO contribution from each receptor site. It was found that the long-term CO variations were controlled both from Asian and global emission source changes, and also significantly by the year-to-year meteorological conditions (outflow efficiency from China). We also showed that the contribution from non-Asian emissions was also especially important in the springtime that was underestimated by the model simulation.

Uno, I., K. Yumimoto, T. Ohara, and J.-I. Kurokawa (2013b), Asian Scale Source-Receptor Analysis based on Tagged CO Transport Model, Journal of Japan Society for Atmospheric Environment/Taiki Kankyo Gakkaishi, 48(3), 123132, doi:
We studied Asian scale source-receptor (S-R) relationship based on the tagged CO tracer model. GEOS Chem (Version 9-1-1) was used with a high-resolution Asian domain (0.5[ring] x .667[ring] resolution) 1-way nested to the global domain. A ten-tagged region was set in the Asian region. The model results showed a good agreement with the surface CO measurements (Yonaguni (YON), Ryori (RYO) and Minami-Torishima (MNM)) and the MOPITT satellite CO measurement. Intermittent CO peaks were well simulated during the winter to spring seasons both at YON and RYO, and its daily averaged concentration ranged from 200 - 300 ppbv. Numerical model also showed low summertime CO concentration below 100 ppbv. The annual averaged CO concentration over the Central-East China (CEC) region reached 500 ppbv. A S-R analysis showed that more than 80 % of the CO was coming from Chinese domestic emissions in that region. The fraction of CO due to the Chinese emission was 50% over the Korea and 35 - 40 % over the Japan region. An analysis of the seasonal variation indicated that the CO originated from China mainly dominated in the winter-spring seasons, while the non-Asian source and natural VOC origin CO showed a relatively high fraction in the summer season.

Vadrevu, K. P., L. Giglio, and C. Justice (2013), Satellite based analysis of firecarbon monoxide relationships from forest and agricultural residue burning (20032011), Atmospheric Environment, 64, 179191, doi:10.1016/j.atmosenv.2012.09.055.
Carbon monoxide (CO) is an important greenhouse gas that is emitted during the incomplete combustion of biomass burning. In this study, we assessed the Measurements Of Pollution In the Troposphere (MOPITT) CO retrievals from two different biomass burning regions, fires in the evergreen forests of Northeast India and agriculture residue fires, Punjab, India. We analyzed long-term trends (20032011) in CO retrievals and fireCO relationships including CO profiles at nine different atmospheric levels. Over a ten year period, the mean monthly CO for Northeast India ranged from 140.86 ppmv (−1σ) to 348.85 ppbv (+1σ) with a mean CO of 244.85 ppbv. We observed a clear increase in CO signal from February to March followed by a decrease in May coinciding with the fire signal. In Punjab, the mean monthly CO ranged from 158.21 ppbv (−1σ) to 286.40 ppbv (+1σ) with a mean CO of 222.30 ppbv. Comparison of mean CO during the peak fire months suggested relatively higher CO (439.06 ppbv) during March (evergreen forest burning) than October (194.83 ppbv) agricultural residue burning. We found MODIS fire radiative power (FRP) as a stronger predictor of surface CO signal than the fire counts in the evergreen forest fires. The segmented regression model fitted using nine years of FRPCO data was useful in finding the FRP threshold impact on CO concentrations in the evergreen forests. To explain the low correlation between fires and MOPITT CO signal from the agricultural residue fires, we used the CALIPSO data to infer the smoke plume heights. Results suggested an average smoke plume height of 2.2 km during the peak biomass burning month from agricultural fires, compared to 4.61 km from evergreen forest fires. Overall, the MODIS FRP and CALIPSO data were useful in understanding the MOPITT CO sensitivity to fires.

Worden, H. M., D. P. Edwards, M. N. Deeter, D. Fu, S. S. Kulawik, J. R. Worden, and A. Arellano (2013a), Averaging kernel prediction from atmospheric and surface state parameters based on multiple regression for nadir-viewing satellite measurements of carbon monoxide and ozone, Atmos. Meas. Tech., 6(7), 16331646, doi:10.5194/amt-6-1633-2013.
A current obstacle to the observation system simulation experiments (OSSEs) used to quantify the potential performance of future atmospheric composition remote sensing systems is a computationally efficient method to define the scene-dependent vertical sensitivity of measurements as expressed by the retrieval averaging kernels (AKs). We present a method for the efficient prediction of AKs for multispectral retrievals of carbon monoxide (CO) and ozone (O-3) based on actual retrievals from MOPITT (Measurements Of Pollution In The Troposphere) on the Earth Observing System (EOS)-Terra satellite and TES (Tropospheric Emission Spectrometer) and OMI (Ozone Monitoring Instrument) on EOS-Aura, respectively. This employs a multiple regression approach for deriving scene-dependent AKs using predictors based on state parameters such as the thermal contrast between the surface and lower atmospheric layers, trace gas volume mixing ratios (VMRs), solar zenith angle, water vapor amount, etc. We first compute the singular value decomposition (SVD) for individual cloud-free AKs and retain the first three ranked singular vectors in order to fit the most significant orthogonal components of the AK in the subsequent multiple regression on a training set of retrieval cases. The resulting fit coefficients are applied to the predictors from a different test set of test retrievals cased to reconstruct predicted AKs, which can then be evaluated against the true retrieval AKs from the test set. By comparing the VMR profile adjustment resulting from the use of the predicted vs. true AKs, we quantify the CO and O-3 VMR profile errors associated with the use of the predicted AKs compared to the true AKs that might be obtained from a computationally expensive full retrieval calculation as part of an OSSE. Similarly, we estimate the errors in CO and O-3 VMRs from using a single regional average AK to represent all retrievals, which has been a common approximation in chemical OSSEs performed to date. For both CO and O-3 in the lower troposphere, we find a significant reduction in error when using the predicted AKs as compared to a single average AK. This study examined data from the continental United States (CONUS) for 2006, but the approach could be applied to other regions and times.

Worden, H. M., M. N. Deeter, C. Frankenberg, M. George, F. Nichitiu, J. Worden, I. Aben, K. W. Bowman, C. Clerbaux, P. F. Coheur, A. T. J. de Laat, R. Detweiler, J. R. Drummond, D. P. Edwards, J. C. Gille, D. Hurtmans, M. Luo, S. Martínez-Alonso, S. Massie, G. Pfister, and J. X. Warner (2013b), Decadal record of satellite carbon monoxide observations, Atmos. Chem. Phys., 13(2), 837850, doi:10.5194/acp-13-837-2013.
Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ~ −1 % yr−1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.

Worden, J., K. Wecht, C. Frankenberg, M. Alvarado, K. Bowman, E. Kort, S. Kulawik, M. Lee, V. Payne, and H. Worden (2013c), CH4 and CO distributions over tropical fires during October 2006 as observed by the Aura TES satellite instrument and modeled by GEOS-Chem, Atmos. Chem. Phys., 13(7), 36793692, doi:10.5194/acp-13-3679-2013.
Tropical fires represent a highly uncertain source of atmospheric methane (CH4) because of the variability of fire emissions and the dependency of the fire CH4 emission factors (g kg−1 dry matter burned) on fuel type and combustion phase. In this paper we use new observations of CH4 and CO in the free troposphere from the Aura Tropospheric Emission Sounder (TES) satellite instrument to place constraints on the role of tropical fire emissions versus microbial production (e.g. in wetlands and livestock) during the (October) 2006 El Niño, a time of significant fire emissions from Indonesia. We first compare the global CH4 distributions from TES using the GEOS-Chem model. We find a mean bias between the observations and model of 26.3 ppb CH4 that is independent of latitude between 50° S and 80° N, consistent with previous validation studies of TES CH4 retrievals using aircraft measurements. The slope of the distribution of CH4 versus CO as observed by TES and modeled by GEOS-Chem is consistent (within the TES observation error) for air parcels over the Indonesian peat fires, South America, and Africa. The CH4 and CO distributions are correlated between R = 0.42 and R = 0.46, with these correlations primarily limited by the TES random error. Over Indonesia, the observed slope of 0.13 (ppb ppb−1) ±0.01, as compared to a modeled slope of 0.153 (ppb ppb−1) ±0.005 and an emission ratio used within the GEOS-Chem model of approximately 0.11 (ppb ppb−1), indicates that most of the observed methane enhancement originated from the fire. Slopes of 0.47 (ppb ppb−1) ±0.04 and 0.44 (ppb ppb−1) ±0.03 over South America and Africa show that the methane in the observed air parcels primarily came from microbial-generated emissions. Sensitivity studies using GEOS-Chem show that part of the observed correlation for the Indonesian observations and most of the observed correlations over South America and Africa are a result of transport and mixing of the fire and nearby microbial-generated emissions into the observed air parcels. Differences between observed and modeled CH4 distributions over South America and southern Africa indicate that the magnitude of the methane emissions for this time period are inconsistent with observations even if the relative distribution of fire versus biotic emissions are consistent. This study shows the potential for estimation of CH4 emissions over tropical regions using joint satellite observations of CH4 and CO.

Worden, J., Z. Jiang, D. B. A. Jones, M. Alvarado, K. Bowman, C. Frankenberg, E. A. Kort, S. S. Kulawik, M. Lee, J. Liu, V. Payne, K. Wecht, and H. Worden (2013d), El Niño, the 2006 Indonesian peat fires, and the distribution of atmospheric methane, Geophysical Research Letters, 40(18), 49384943, doi:10.1002/grl.50937.
Dry conditions from a moderate El Niño during the fall of 2006 resulted in enhanced burning in Indonesia with fire emissions of CO approximately 46 times larger than the prior year. Here we use new tropospheric methane and CO data from the Aura Tropospheric Emission Spectrometer and new CO profile measurements from the Terra Measurements of Pollution in the Troposphere (MOPITT) satellite instruments with the Goddard Earth Observing System (GEOS)-Chem model to estimate methane emissions of 4.25 ± 0.75 Tg for OctoberNovember 2006 from these fires. Errors in convective parameterization in GEOS-Chem, evaluated by comparing MOPITT and GEOS-Chem CO profiles, are the primary uncertainty of the emissions estimate. The El Niño related Indonesian fires increased the tropical distribution of atmospheric methane relative to 2005, indicating that tropical biomass burning can compensate for expected decreases in tropical wetland methane emissions from reduced rainfall during El Niño as found in previous studies.

Yoon, J., A. Pozzer, P. Hoor, D. Y. Chang, S. Beirle, T. Wagner, S. Schloegl, J. Lelieveld, and H. M. Worden (2013), Technical Note: Temporal change in averaging kernels as a source of uncertainty in trend estimates of carbon monoxide retrieved from MOPITT, Atmos. Chem. Phys., 13(22), 1130711316, doi:10.5194/acp-13-11307-2013.
It is now possible to monitor the global and long-term trends of trace gases that are important to atmospheric chemistry, climate, and air quality with satellite data records that span more than a decade. However, many of the remote sensing techniques used by satellite instruments produce measurements that have variable sensitivity to the vertical profiles of atmospheric gases. In the case of constrained retrievals like optimal estimation, this leads to a varying amount of a priori information in the retrieval and is represented by an averaging kernel. In this study, we investigate to what extent such trends can be biased by temporal changes of averaging kernels used in the retrieval algorithm. In particular, the surface carbon monoxide data retrieved from the Measurements Of Pollution In The Troposphere (MOPITT) instrument from 2001 to 2010 were analysed. As a practical example based on the MOPITT data, we show that if the true atmospheric mixing ratio is continuously 50% higher or lower than the a priori state, the temporal change of the averaging kernel at the surface level gives rise to an artificial trend in retrieved surface carbon monoxide, ranging from −10.71 to +13.21 ppbv yr−1 (−5.68 to +8.84% yr−1) depending on location. Therefore, in the case of surface (or near-surface level) CO derived from MOPITT, the AKs trends multiplied by the difference between true and a priori states must be quantified in order to estimate trend biases.

Zbinden, R. M., V. Thouret, P. Ricaud, F. Carminati, J.-P. Cammas, and P. Nédélec (2013), Climatology of pure tropospheric profiles and column contents of ozone and carbon monoxide using MOZAIC in the mid-northern  latitudes (24° N to 50° N) from 1994 to 2009, Atmos. Chem. Phys., 13(24), 1236312388, doi:10.5194/acp-13-12363-2013.
The objective of this paper is to deliver the most accurate ozone (O3) and carbon monoxide (CO) climatology for the pure troposphere only, i.e. exclusively from the ground to the dynamical tropopause on an individual profile basis. The results (profiles and columns) are derived solely from the Measurements of OZone and water vapour by in-service Alrbus airCraft programme (MOZAIC) over 15 years (19942009). The study, focused on the northern mid-latitudes [2450° N] and [119° W140° E], includes more than 40 000 profiles over 11 sites to give a quasi-global zonal picture. Considering all the sites, the pure tropospheric column peak-to-peak seasonal cycle ranges are 23.743.2 DU for O3 and 1.76.9 × 10 18 molecules cm−2 for CO. The maxima of the seasonal cycles are not in phase, occurring in FebruaryApril for CO and MayJuly for O3. The phase shift is related to the photochemistry and OH removal efficiencies. The purely tropospheric seasonal profiles are characterized by a typical autumnwinter/springsummer O3 dichotomy (except in Los Angeles, Eastmed a cluster of Cairo and Tel Aviv and the regions impacted by the summer monsoon) and a summerautumn/winterspring CO dichotomy. We revisit the boundary-layer, mid-tropospheric (MT) and upper-tropospheric (UT) partial columns using a~new monthly varying MT ceiling. Interestingly, the seasonal cycle maximum of the UT partial columns is shifted from summer to spring for O3 and to very early spring for CO. Conversely, the MT maximum is shifted from spring to summer and is associated with a summer (winter) MT thickening (thinning). Lastly, the pure tropospheric seasonal cycles derived from our analysis are consistent with the cycles derived from spaceborne measurements, the correlation coefficients being r=0.60.9 for O3 and r>0.9 for CO. The cycles observed from space are nevertheless greater than MOZAIC for O3 (by 918 DU) and smaller for CO (up to 1 × 10 18 molecules cm−2). The larger winter O3 difference between the two data sets suggests probable stratospheric contamination in satellite data due to the tropopause position. The study underlines the importance of rigorously discriminating between the stratospheric and tropospheric reservoirs and avoiding use of a~monthly averaged tropopause position without this strict discrimination in order to assess the pure O3 and CO tropospheric trends.

Zhou, D., A. Ding, H. Mao, C. Fu, T. Wang, L. Y. Chan, K. Ding, Y. Zhang, J. Liu, A. Lu, and N. Hao (2013), Impacts of the East Asian monsoon on lower tropospheric ozone over coastal South China, Environ. Res. Lett., 8(4), 044011, doi:10.1088/1748-9326/8/4/044011.
The impact of the East Asian monsoon (EAM) on climatology and interannual variability of tropospheric ozone (O3) over the coastal South China was investigated by analyzing 11 years of ozonesonde data over Hong Kong with the aid of Lagrangian dispersion modeling of carbon monoxide and calculation of an EAM index. It was found that the seasonal cycle of O3 in the lower troposphere is highly related to the EAM over the study region. Ozone enhancements in the free troposphere are associated with the monsoon-induced transport of pollutants of continental anthropogenic and biomass burning origins. Lower tropospheric O3 levels showed high interannual variability, with an annual averaged amplitude up to 61% of averaged concentrations in the boundary layer (01 km altitudes) and 49% below 3 km altitude. In spring and autumn, the interannual variability in boundary layer O3 levels was predominately influenced by the EAM intensity, with high O3 mixing ratios associated with northeasterly circulation anomalies.


August, T., D. Klaes, P. Schlüssel, T. Hultberg, M. Crapeau, A. Arriaga, A. O’Carroll, D. Coppens, R. Munro, and X. Calbet (2012), IASI on Metop-A: Operational Level 2 retrievals after five years in orbit, Journal of Quantitative Spectroscopy and Radiative Transfer, 113(11), 13401371, doi:10.1016/j.jqsrt.2012.02.028.
Geophysical parameters from the IASI instrument on Metop-A are essential products provided from EUMETSAT’s Central Facility in near real time. They include vertical profiles of temperature and humidity, related cloud information, surface emissivity and temperature, and atmospheric composition parameters (CO, ozone and several other trace gases). As compared to previous operational processor versions, the latest processor version 5 delivers significant improvements in retrieval performance for most major products. These include improvements to cloud properties products, cloud detection (with a positive impact on the knowledge of the sea surface temperature, SST), the temperature profile (especially in the mid and upper troposphere), and ozone and carbon monoxide total columns. This paper provides a comprehensive summary of the processing algorithms, the latest scientific developments, and the related validation studies and activities. It concludes with a discussion of the future outlook.

Boynard, A., G. G. Pfister, and D. P. Edwards (2012), Boundary layer versus free tropospheric CO budget and variability over the United States during summertime, Journal of Geophysical Research: Atmospheres, 117(D4), n/a-n/a, doi:10.1029/2011JD016416.
The regional Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.2 is used to analyze the carbon monoxide (CO) budget and spatiotemporal variability over the United States in summer 2008. CO tracers for different emission sources are used to separate the modeled CO fields into the contributions from individual sources (pollution inflow to the model domain, chemical production within the model domain, and local emissions by type). The implementation of tagged CO tracers into WRF-Chem constitutes an innovative aspect of this work. We evaluate WRF-Chem CO concentrations using aircraft, satellite, and surface observations. The model reproduces fairly well the observed CO concentrations for the entire altitude range but tends to underestimate fire emissions and overestimate anthropogenic sources and CO from pollution inflow. Evaluation results also show that the model gives a good representation of background CO mixing ratios with mean biases better than ∼15 ppbv in the free troposphere (FT) and less than 20 ppbv toward the surface. The analysis of the CO budget over the contiguous United States shows that at the surface, CO from inflow is the dominant source, with a mean relative contribution of 63 ± 19%. Anthropogenic and photochemically produced CO contribute to surface CO to a lesser extent (18 ± 14% and 14 ± 8%, respectively). The average contribution from fire emissions to surface CO during the period examined is small (2 ± 5%) but can have a large impact in certain regions and times. Similar trends are found in the planetary boundary layer (PBL). In the FT, the average CO relative contributions are estimated as 84 ± 12% for CO from inflow, 5 ± 4% for anthropogenic CO, 9 ± 7% for photochemically produced CO, and 1 ± 5% for CO from fires. Using WRF-Chem simulations, we also examine the representation of surface and PBL CO concentration variability that would be captured by current near infrared (NIR) and thermal infrared (TIR) satellite observations. We find that CO total columns are impacted by variability in the lowermost troposphere (LMT) at the ∼10% level, indicating limited sensitivity for air quality applications. The same is generally true for the FT CO column obtained from TIR measurements, although this does provide a good measure for capturing the pollution inflow variability and is therefore valuable in providing initial and boundary conditions to constrain regional models. We further analyze the situations under which the LMT concentrations obtained from recently demonstrated multispectral (NIR + TIR) observations capture the surface CO variability.

Deeter, M. N., H. M. Worden, D. P. Edwards, J. C. Gille, and A. E. Andrews (2012), Evaluation of MOPITT retrievals of lower-tropospheric carbon monoxide over the United States, Journal of Geophysical Research: Atmospheres, 117(D13), n/a-n/a, doi:10.1029/2012JD017553.
The new Version 5 MOPITT (Measurements of Pollution in the Troposphere) product for carbon monoxide (CO) is the first satellite product to exploit simultaneous near-infrared and thermal-infrared observations to enhance retrieval sensitivity in the lower troposphere. This feature is important to air quality analyses and studies of CO sources. However, because of the influence of both thermal contrast and geophysical noise, the retrieval characteristics for this new multispectral product are highly variable. New V5 products for surface-level CO concentrations have been evaluated over the contiguous United States using both in situ vertical profiles and NOAA ground-based “Tall Tower” measurements. Validation results based on the in situ profiles indicate that retrieval biases are on the order of a few percent. However, direct comparisons with the Tall Tower measurements demonstrate that smoothing error, which depends on both the retrieval averaging kernels and CO variability in the lower troposphere, exhibits significant geographical and seasonal variability.

Drori, R., U. Dayan, D. P. Edwards, L. K. Emmons, and C. Erlick (2012), Attributing and quantifying carbon monoxide sources affecting the Eastern Mediterranean: a combined satellite, modelling, and synoptic analysis study, Atmos. Chem. Phys., 12(2), 10671082, doi:10.5194/acp-12-1067-2012.
Pollutants from global sources are known to affect the Eastern Mediterranean Shore (EMS). However, there has been no previous study explicitly locating the European sources, characterizing their transport pathways, and quantifying their contribution to local concentrations in the EMS. In the current study, spatially tagged carbon monoxide was used as a tracer for pollutant transport from Europe to the EMS over five consecutive years (2003-2007) using the global chemical transport model MOZART-4. The model results were compared against NOAA/GMD ground station data and remotely sensed data from the Terra/MOPITT satellite and found to agree well on monthly basis but do not agree on daily basis. On synoptic scale, there is agreement between MOZART and GMD during July to August. A budget analysis reveals the role of CO from hydrocarbon oxidation on CO concentration during summer. European anthropogenic emissions were found to significantly influence EM surface concentrations, while European biomass burning (BB) emissions were found to have only a small impact on EM surface concentrations. Over the five simulated years, only two European biomass burning episodes contributed more than 10 ppb to surface CO concentrations in the EM. CO enhancement in the EM during the summer was attributed to synoptic conditions prone to favorable transport from Turkey and Eastern Europe towards the EM rather than increased emissions. We attribute the apparently misleading association between CO emitted from European BB and CO enhancements over the EM to typical summer synoptic conditions caused by the lingering of an anticyclone positioned over the Western and Central Mediterranean Basin that lead to forest fires in the area. Combined with a barometric trough over the eastern part of the Mediterranean Basin, this generates a prevailing transport of air masses from Eastern Europe to the EMS. Synoptic scale variations are shown to change the transport pathways from Europe towards the EMS having an overall small affect. CO concentration over the EMS can be describe as having 3 components: the seasonal cycle, the cycle of CO produced from hydrocarbon oxidation and a synoptic variation.

Fortems-Cheiney, A., F. Chevallier, I. Pison, P. Bousquet, M. Saunois, S. Szopa, C. Cressot, T. P. Kurosu, K. Chance, and A. Fried (2012), The formaldehyde budget as seen by a global-scale multi-constraint and multi-species inversion system, Atmos. Chem. Phys., 12(15), 66996721, doi:10.5194/acp-12-6699-2012.
For the first time, carbon monoxide (CO) and formaldehyde (HCHO) satellite retrievals are used together with methane (CH4) and methyl choloroform (CH3CCl3 or MCF) surface measurements in an advanced inversion system. The CO and HCHO are respectively from the MOPITT and OMI instruments. The multi-species and multi-satellite dataset inversion is done for the 2005-2010 period. The robustness of our results is evaluated by comparing our posterior-modeled concentrations with several sets of independent measurements of atmospheric mixing ratios. The inversion leads to significant changes from the prior to the posterior, in terms of magnitude and seasonality of the CO and CH4 surface fluxes and of the HCHO production by non-methane volatile organic compounds (NMVOC). The latter is significantly decreased, indicating an overestimation of the biogenic NMVOC emissions, such as isoprene, in the GEIA inventory. CO and CH4 surface emissions are increased by the inversion, from 1037 to 1394 TgCO and from 489 to 529 TgCH(4) on average for the 2005-2010 period. CH4 emissions present significant interannual variability and a joint CO-CH4 fluxes analysis reveals that tropical biomass burning probably played a role in the recent increase of atmospheric methane.

Herron-Thorpe, F. L., G. H. Mount, L. K. Emmons, B. K. Lamb, S. H. Chung, and J. K. Vaughan (2012), Regional air-quality forecasting for the Pacific Northwest using MOPITT/TERRA assimilated carbon monoxide MOZART-4 forecasts as a near real-time boundary condition, Atmos. Chem. Phys., 12(12), 56035615, doi:10.5194/acp-12-5603-2012.
Results from a regional air quality forecast model, AIRPACT-3, were compared to AIRS carbon monoxide column densities for the spring of 2010 over the Pacific Northwest. AIRPACT-3 column densities showed high correlation (R > 0.9) but were significantly biased (similar to 25%) with consistent under-predictions for spring months when there is significant transport from Asia. The AIRPACT-3 CO bias relative to AIRS was eliminated by incorporating dynamic boundary conditions derived from NCAR’s MOZART forecasts with assimilated MOPITT carbon monoxide. Changes in ozone-related boundary conditions derived from MOZART forecasts are also discussed and found to affect background levels by +/- 10 ppb but not found to significantly affect peak ozone surface concentrations.

Hooghiemstra, P. B., M. C. Krol, P. Bergamaschi, A. T. J. de Laat, G. R. van der Werf, P. C. Novelli, M. N. Deeter, I. Aben, and T. Röckmann (2012a), Comparing optimized CO emission estimates using MOPITT or NOAA surface network observations, Journal of Geophysical Research: Atmospheres, 117(D6), n/a-n/a, doi:10.1029/2011JD017043.
This paper compares two global inversions to estimate carbon monoxide (CO) emissions for 2004. Either surface flask observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) or CO total columns from the Measurement of Pollution in the Troposphere (MOPITT) instrument are assimilated in a 4D-Var framework. Inferred emission estimates from the two inversions are consistent over the Northern Hemisphere (NH). For example, both inversions increase anthropogenic CO emissions over Europe (from 46 to 94 Tg CO/yr) and Asia (from 222 to 420 Tg CO/yr). In the Southern Hemisphere (SH), three important findings are reported. First, due to their different vertical sensitivity, the stations-only inversion increases SH biomass burning emissions by 108 Tg CO/yr more than the MOPITT-only inversion. Conversely, the MOPITT-only inversion results in SH natural emissions (mainly CO from oxidation of NMVOCs) that are 185 Tg CO/yr higher compared to the stations-only inversion. Second, MOPITT-only derived biomass burning emissions are reduced with respect to the prior which is in contrast to previous (inverse) modeling studies. Finally, MOPITT derived total emissions are significantly higher for South America and Africa compared to the stations-only inversion. This is likely due to a positive bias in the MOPITT V4 product. This bias is also apparent from validation with surface stations and ground-truth FTIR columns. Our results show that a combined inversion is promising in the NH. However, implementation of a satellite bias correction scheme is essential to combine both observational data sets in the SH.

Hooghiemstra, P. B., M. C. Krol, T. T. van Leeuwen, G. R. van der Werf, P. C. Novelli, M. N. Deeter, I. Aben, and T. Röckmann (2012b), Interannual variability of carbon monoxide emission estimates over South America from 2006 to 2010, Journal of Geophysical Research: Atmospheres, 117(D15), n/a-n/a, doi:10.1029/2012JD017758.
We present the first inverse modeling study to estimate CO emissions constrained by both surface and satellite observations. Our 4D-Var system assimilates National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) surface and Measurements Of Pollution In The Troposphere (MOPITT) satellite observations jointly by fitting a bias correction scheme. This approach leads to the identification of a positive bias of maximum 5 ppb in MOPITT column-averaged CO mixing ratios in the remote Southern Hemisphere (SH). The 4D-Var system is used to estimate CO emissions over South America in the period 20062010 and to analyze the interannual variability (IAV) of these emissions. We infer robust, high spatial resolution CO emission estimates that show slightly smaller IAV due to fires compared to the Global Fire Emissions Database (GFED3) prior emissions. South American dry season (August and September) biomass burning emission estimates amount to 60, 92, 42, 16 and 93 Tg CO/yr for 2006 to 2010, respectively. Moreover, CO emissions probably associated with pre-harvest burning of sugar cane plantations in São Paulo state are underestimated in current inventories by 50100%. We conclude that climatic conditions (such as the widespread drought in 2010) seem the most likely cause for the IAV in biomass burning CO emissions. However, socio-economic factors (such as the growing global demand for soy, beef and sugar cane ethanol) and associated deforestation fires, are also likely as drivers for the IAV of CO emissions, but are difficult to link directly to CO emissions.

Huijnen, V., J. Flemming, J. W. Kaiser, A. Inness, J. Leitão, A. Heil, H. J. Eskes, M. G. Schultz, A. Benedetti, J. Hadji-Lazaro, G. Dufour, and M. Eremenko (2012), Hindcast experiments of tropospheric composition during the summer 2010  fires over western Russia, Atmos. Chem. Phys., 12(9), 43414364, doi:10.5194/acp-12-4341-2012.
The severe wildfires in western Russia during July-August 2010 coincided with a strong heat wave and led to large emissions of aerosols and trace gases such as carbon monoxide (CO), hydrocarbons and nitrogen oxides into the troposphere. This extreme event is used to evaluate the ability of the global MACC (Monitoring Atmospheric Composition and Climate) atmospheric composition forecasting system to provide analyses of large-scale pollution episodes and to test the respective influence of a priori emission information and data assimilation on the results. Daily 4-day hindcasts were conducted using assimilated aerosol optical depth (AOD), CO, nitrogen dioxide (NO2) and ozone (O-3) data from a range of satellite instruments. Daily fire emissions were used from the Global Fire Assimilation System (GFAS) version 1.0, derived from satellite fire radiative power retrievals. The impact of accurate wildfire emissions is dominant on the composition in the boundary layer, whereas the assimilation system influences concentrations throughout the troposphere, reflecting the vertical sensitivity of the satellite instruments. The application of the daily fire emissions reduces the area-average mean bias by 63% (for CO), 60% (O-3) and 75% (NO2) during the first 24 h with respect to independent satellite observations, compared to a reference simulation with a multi-annual mean climatology of biomass burning emissions. When initial tracer concentrations are further constrained by data assimilation, biases are reduced by 87, 67 and 90%. The forecast accuracy, quantified by the mean bias up to 96 h lead time, was best for all compounds when using both the GFAS emissions and assimilation. The model simulations suggest an indirect positive impact of O-3 and CO assimilation on hindcasts of NO2 via changes in the oxidizing capacity. However, the quality of local hindcasts was strongly dependent on the assumptions made for forecasted fire emissions. This was well visible from a relatively poor forecast accuracy quantified by the root mean square error, as well as the temporal correlation with respect to ground-based CO total column data and AOD. This calls for a more advanced method to forecast fire emissions than the currently adopted persistency approach. The combined analysis of fire radiative power observations, multiple trace gas and aerosol satellite observations, as provided by the MACC system, results in a detailed quantitative description of the impact of major fires on atmospheric composition, and demonstrate the capabilities for the real-time analysis and forecasts of large-scale fire events.

Kumar, R., M. Naja, G. G. Pfister, M. C. Barth, C. Wiedinmyer, and G. P. Brasseur (2012), Simulations over South Asia using the Weather Research and Forecasting  model with Chemistry (WRF-Chem): chemistry evaluation and initial  results, Geosci. Model Dev., 5(3), 619648, doi:10.5194/gmd-5-619-2012.
This study presents annual simulations of tropospheric ozone and related species made for the first time using the WRF-Chem model over South Asia for the year 2008. The model-simulated ozone, CO, and NOx are evaluated against ground-based, balloon-borne and satellite-borne (TES, OMI and MOPITT) observations. The comparison of model results with surface ozone observations from seven sites and CO and NOx observations from three sites indicate the model’s ability in reproducing seasonal variations of ozone and CO, but show some differences in NOx. The modeled vertical ozone distribution agrees well with the ozone soundings data from two Indian sites. The vertical distributions of TES ozone and MOPITT CO are generally well reproduced, but the model underestimates TES ozone, OMI tropospheric column NO2 and MOPITT total column CO retrievals during all the months, except MOPITT retrievals during August-January and OMI retrievals during winter. Largest differences between modeled and satellite-retrieved quantities are found during spring when intense biomass burning activity occurs in this region. The evaluation results indicate large uncertainties in anthropogenic and biomass burning emission estimates, especially for NOx. The model results indicate clear regional differences in the seasonality of surface ozone over South Asia, with estimated net ozone production during daytime (1130-1530 h) over inland regions of 0-5 ppbv h(-1) during all seasons and of 0-2 ppbv h(-1) over marine regions during outflow periods. The model results indicate that ozone production in this region is mostly NOx-limited. This study shows that WRF-Chem model captures many important features of the observations and gives confidence to using the model for understanding the spatio-temporal variability of ozone over South Asia. However, improvements of South Asian emission inventories and simulations at finer model resolution, especially over the complex Himalayan terrain in northern India, are also essential for accurately simulating ozone in this region.

Martinez-Alonso, S., M. N. Deeter, H. M. Worden, C. Clerbaux, D. Mao, and J. C. Gille (2012), First satellite identification of volcanic carbon monoxide, Geophys. Res. Lett., 39, doi:10.1029/2012GL053275.
Volcanic degassing produces abundant H2O and CO2, as well as SO2, HCl, H2S, S-2, H-2, HF, CO, and SiF4. Volcanic SO2, HCl, and H2S have been detected from satellites in the past; the remaining species are analyzed in situ or using airborne instruments, with all the consequent limitations in safety and sampling, and at elevated costs. We report identification of high CO concentrations consistent with a volcanic origin (the 2010 Eyjafjallajokull and 2011 Grimsvotn eruptions in Iceland) in data from the Measurements of Pollution in the Troposphere instrument (MOPITT) onboard EOS/Terra. The high CO values coincide spatially and temporally with ash plumes emanating from the eruptive centers, with elevated SO2 and aerosol optical thickness, as well as with high CO values in data from the Infrared Atmospheric Sounding Interferometer (IASI), onboard MetOp-A. CO has a positive indirect radiative forcing; climate models currently do not account for volcanic CO emissions. Given global volcanic CO2 emissions between 130 and 440 Tg/year and volcanic CO: CO2 ratios from the literature, we estimate that average global volcanic CO emissions may be on the order of similar to 5.5 Tg/year, equivalent to the CO emissions caused by combined fossil fuel and biofuel combustion in Australia. Citation: Martinez-Alonso, S., M. N. Deeter, H. M. Worden, C. Clerbaux, D. Mao, and J. C. Gille (2012), First satellite identification of volcanic carbon monoxide, Geophys. Res. Lett., 39, L21809, doi:10.1029/2012GL053275.

Miyazaki, K., H. J. Eskes, K. Sudo, M. Takigawa, M. van Weele, and K. F. Boersma (2012), Simultaneous assimilation of satellite NO2, O3, CO, and HNO3 data for the analysis of tropospheric chemical composition and emissions, Atmos. Chem. Phys., 12(20), 95459579, doi:10.5194/acp-12-9545-2012.
We have developed an advanced chemical data assimilation system to combine observations of chemical compounds from multiple satellites. NO2, O3, CO, and HNO3 measurements from the Ozone Monitoring Instrument (OMI), Tropospheric Emission Spectrometer (TES), Measurement of Pollution in the Troposphere (MOPITT), and Microwave Limb Sounder (MLS) satellite instruments are assimilated into the global chemical transport model CHASER for the years 20062007. The CHASER data assimilation system (CHASER-DAS), based on the local ensemble transform Kalman filter technique, simultaneously optimizes the chemical species, as well as the emissions of O3 precursors, while taking their chemical feedbacks into account. With the available datasets, an improved description of the chemical feedbacks can be obtained, especially related to the NOx-CO-OH-O3 set of chemical reactions. Comparisons against independent satellite, aircraft, and ozonesonde data show that the data assimilation results in substantial improvements for various chemical compounds. These improvements include a reduced negative tropospheric NO2 column bias (by 4085%), a reduced negative CO bias in the Northern Hemisphere (by 4090%), and a reduced positive O3 bias in the middle and upper troposphere (from 3040% to within 10%). These changes are related to increased tropospheric OH concentrations by 515% in the tropics and the Southern Hemisphere in July. Observing System Experiments (OSEs) have been conducted to quantify the relative importance of each data set on constraining the emissions and concentrations. The OSEs confirm that the assimilation of individual data sets results in a strong influence on both assimilated and non-assimilated species through the inter-species error correlation and the chemical coupling described by the model. The simultaneous adjustment of the emissions and concentrations is a powerful approach to correcting the tropospheric ozone budget and profile analyses.

Moore, D. P., J. J. Remedios, and A. M. Waterfall (2012), Global distributions of acetone in the upper troposphere from MIPAS spectra, Atmos. Chem. Phys., 12(2), 757768, doi:10.5194/acp-12-757-2012.
This study reports the first global measurements of acetone (C3H6O) in the upper troposphere (UT). Profiles were obtained between 9 km and 15 km from measurements made by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard Envisat in August 2003. Errors per profile are lower than 40 % between 180 hPa and 350 hPa. We report strong hemispheric differences in the acetone volume mixing ratios (VMRs), with average concentrations highest in the Northern Hemisphere (NH) mid-latitude UT, between 1000 pptv and 1600 pptv with maxima up to 2300 pptv. Our results show a strong enhancement of acetone relative to CO, particularly over Europe (7 pptv ppbv−1), confirming aircraft studies. Ten-day backward trajectories from these high European values show strong contributions from air flows over North America (56 %) and 25 % from Southernmost Asia. Enhanced acetone is also observed over Greenland, Siberia and biomass burning regions of Africa. Zonal distributions show that acetone VMRs decrease rapidly with increasing altitude (decreasing pressure), particularly in the NH. Poleward of 45° S, acetone VMRs remain fairly consistent with average VMRs between 400 pptv and 500 pptv. In 5-day averages at 9 km, NH VMRs poleward of 45° N are consistently higher than Southern Hemisphere observations poleward of 45° S, by between 750 pptv and 1100 pptv. The results show a clear influence of mid-latitude and transport processes on the acetone summertime distribution.

Morgenstern, O., G. Zeng, S. W. Wood, J. Robinson, D. Smale, C. Paton-Walsh, N. B. Jones, and D. W. T. Griffith (2012), Long-range correlations in Fourier transform infrared, satellite, and  modeled CO in the Southern Hemisphere, J. Geophys. Res.-Atmos., 117, doi:10.1029/2012JD017639.
We use Fourier transform infrared ground-based measurements and satellite and model data to assess long-range correlations in tropospheric carbon monoxide. We find that CO columns measured in New Zealand correlate well with those measured in Antarctica, if a transport-related lag is taken into account. The model suggests that this long-range correlation is part of a mode of anomalous CO comprising almost the whole southern extratropics, which is linked to biomass burning in the southern continents. No such mode is modeled for the Northern Hemisphere. The area of long-range correlations maximizes for the southern subtropical Pacific, which is identified as an advantageous location for a hypothetical new measurement station. The satellite data (produced by the Measurements of Pollution in the Troposphere (MOPITT) instrument) partially confirm these findings but with generally reduced correlations. In particular, the satellite data suggest no long-range correlation at high latitudes. This is partially explained in terms of retrieval limitations and partially reflects a model deficiency.

Parrington, M., P. I. Palmer, D. K. Henze, D. W. Tarasick, E. J. Hyer, R. C. Owen, D. Helmig, C. Clerbaux, K. W. Bowman, M. N. Deeter, E. M. Barratt, P.-F. Coheur, D. Hurtmans, Z. Jiang, M. George, and J. R. Worden (2012), The influence of boreal biomass burning emissions on the distribution of tropospheric ozone over North America and the North Atlantic during 2010, Atmos. Chem. Phys., 12(4), 20772098, doi:10.5194/acp-12-2077-2012.
We have analysed the sensitivity of the tropospheric ozone distribution over North America and the North Atlantic to boreal biomass burning emissions during the summer of 2010 using the GEOS-Chem 3-D global tropospheric chemical transport model and observations from in situ and satellite instruments. We show that the model ozone distribution is consistent with observations from the Pico Mountain Observatory in the Azores, ozonesondes across Canada, and the Tropospheric Emission Spectrometer (TES) and Infrared Atmospheric Sounding Instrument (IASI) satellite instruments. Mean biases between the model and observed ozone mixing ratio in the free troposphere were less than 10 ppbv. We used the adjoint of GEOS-Chemto show the model ozone distribution in the free troposphere over Maritime Canada is largely sensitive to NOx emissions from biomass burning sources in Central Canada, lightning sources in the central US, and anthropogenic sources in the eastern US and southeastern Canada. We also used the adjoint of GEOS-Chem to evaluate the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory through assimilation of CO observations from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument. The CO inversion showed that, on average, the FLAMBE emissions needed to be reduced to 89% of their original values, with scaling factors ranging from 12% to 102 %, to fit the MOPITT observations in the boreal regions. Applying the CO scaling factors to all species emitted from boreal biomass burning sources led to a decrease of the model tropospheric distributions of CO, PAN, and NOx by as much as -20 ppbv, -50 pptv, and -20 pptv respectively. The modification of the biomass burning emission estimates reduced the model ozone distribution by approximately -3 ppbv (-8%) and on average improved the agreement of the model ozone distribution compared to the observations throughout the free troposphere, reducing the mean model bias from 5.5 to 4.0 ppbv for the Pico Mountain Observatory, 3.0 to 0.9 ppbv for ozonesondes, 2.0 to 0.9 ppbv for TES, and 2.8 to 1.4 ppbv for IASI.

Pozzer, A., P. Zimmermann, U. M. Doering, J. van Aardenne, H. Tost, F. Dentener, G. Janssens-Maenhout, and J. Lelieveld (2012), Effects of business-as-usual anthropogenic emissions on air quality, Atmos. Chem. Phys., 12(15), 69156937, doi:10.5194/acp-12-6915-2012.
The atmospheric chemistry general circulation model EMAC has been used to estimate the impact of anthropogenic emission changes on global and regional air quality in recent and future years (2005, 2010, 2025 and 2050). The emission scenario assumes that population and economic growth largely determine energy and food consumption and consequent pollution sources with the current technologies (“business as usual”). This scenario is chosen to show the effects of not implementing legislation to prevent additional climate change and growing air pollution, other than what is in place for the base year 2005, representing a pessimistic (but plausible) future.  By comparing with recent observations, it is shown that the model reproduces the main features of regional air pollution distributions though with some imprecisions inherent to the coarse horizontal resolution (similar to 100 km) and simplified bottom-up emission input.  To identify possible future hot spots of poor air quality, a multi pollutant index (MPI), suited for global model output, has been applied. It appears that East and South Asia and the Middle East represent such hotspots due to very high pollutant concentrations, while a general increase of MPIs is observed in all populated regions in the Northern Hemisphere. In East Asia a range of pollutant gases and fine particulate matter (PM2.5) is projected to reach very high levels from 2005 onward, while in South Asia air pollution, including ozone, will grow rapidly towards the middle of the century. Around the Persian Gulf, where natural PM2.5 concentrations are already high (desert dust), ozone levels are expected to increase strongly.  The population weighted MPI (PW-MPI), which combines demographic and pollutant concentration projections, shows that a rapidly increasing number of people worldwide will experience reduced air quality during the first half of the 21st century. Following this business as usual scenario, it is projected that air quality for the global average citizen in 2050 would be almost comparable to that for the average citizen in East Asia in the year 2005, which underscores the need to pursue emission reductions.

Safronov, A. N., E. V. Fokeeva, V. S. Rakitin, L. N. Yurganov, and E. I. Grechko (2012), Carbon monoxide emissions in summer 2010 in the central part of the Russian Plain and estimation of their uncertainties with the use of different land-cover maps, Izv. Atmos. Ocean. Phys., 48(9), 925940, doi:10.1134/S0001433812090150.
This study is devoted to estimation of carbon monoxide (CO) emissions during the wildfires of the anomalously hot 2010 summer in the central part of the Russian Plain. CO emissions from the forest wildfires have been estimated with use of the Active Fires (AF) (MODIS MCD14ML) and Burned Areas (BA) (MODIS MCD45) methods for AVHRR/UDM, Global Land Cover 2000 (GLC 2000), GlobCover, and MCD12Q1 vegetation maps. A comparison of the vegetation maps and investigation of forest structure dynamics for the period from 2005 to 2009 have been carried out. It is shown that the major uncertainties during the estimation of CO in decreasing order are the following: distinctions in emission-calculation methods, differences in the vegetation maps used, differences in satellite data from Terra and Aqua, and the insufficient registration of forest structure dynamics. For additional comparison of estimations obtained by an independent method with the use of orbital (MOPITT, AIRS, and IASI) and ground-based (Moscow and Zvenigorod) spectroscopic measurements of CO content were presented.

Srivastava, S., S. Lal, S. Venkataramani, S. Gupta, and V. Sheel (2012), Surface distributions of O3, CO and hydrocarbons over the Bay of Bengal and the Arabian Sea during pre-monsoon season, Atmospheric Environment, 47, 459467, doi:10.1016/j.atmosenv.2011.10.023.
Mixing ratios of ozone (O3), carbon monoxide (CO), methane (CH4) and few light non methane hydrocarbons (NMHCs) were measured on board the ocean research vessel Sagar Kanya over the Bay of Bengal and the Arabian Sea during the spring of 2006 as a part of an Integrated Campaign for Aerosol, gases and Radiation Budget (ICARB). North-westerly winds prevailing during this period transport large amount of anthropogenic pollutants from the Indo-Gangetic Plain (IGP) to the northern part of Bay of Bengal. The south-westerly and north-westerly winds carried cleaner marine air having lower abundance of pollutants over the southern Bay of Bengal and Arabian Sea. Ozone, CH4, CO, ethane and n-butane are found to be well correlated with each other over the northern Bay of Bengal indicating their common co-located sources. The latitudinal gradients of these species are found to be significant (O3 ∼ 5.4 ppbv deg−1, CH4 ∼ 5.3 ppbv deg−1, CO ∼ 10 ppbv deg−1, ethane ∼ 93.2 pptv deg−1 and n-butane ∼ 59.7 pptv deg−1) over this region. Surprisingly, and in contrast to over the Bay of Bengal, the mixing ratios of these trace gases over the Arabian Sea are found comparatively higher over the southern region than over the northern region leading to negative latitudinal gradients. The short lived species with oceanic sources like ethene and propene show large variability and higher mixing ratios over southern parts of both the marine regions. These observations are compared with previous measurements made over these marine regions and the results obtained from the 3D MOZART chemistry transport model. The present study shows that the two marine regions adjacent to the Indian subcontinent are completely different from the perspective of surface level distributions of these species.

Su, M., Y. Lin, X. Fan, L. Peng, and C. Zhao (2012), Impacts of global emissions of CO, NO x , and CH4 on China tropospheric hydroxyl free radicals, Adv. Atmos. Sci., 29(4), 838854, doi:10.1007/s00376-012-1229-2.
Using the global chemistry and transport model MOZART, the simulated distributions of tropospheric hydroxyl free radicals (OH) over China and its sensitivities to global emissions of carbon monoxide (CO), nitrogen oxide (NO x ), and methane (CH4) were investigated in this study. Due to various distributions of OH sources and sinks, the concentrations of tropospheric OH in east China are much greater than in west China. The contribution of NO + perhydroxyl radical (HO2) reaction to OH production in east China is more pronounced than that in west China, and because of the higher reaction activity of non-methane volatile organic compounds (NMVOCs), the contributions to OH loss by NMVOCs exceed those of CO and take the dominant position in summer. The results of the sensitivity runs show a significant increase of tropospheric OH in east China from 1990 to 2000, and the trend continues. The positive effect of double emissions of NO x on OH is partly offset by the contrary effect of increased CO and CH4 emissions: the double emissions of NO x will cause an increase of OH of 18.1%30.1%, while the increases of CO and CH4 will cause a decrease of OH of 12.2%20.8% and 0.3%3.0%, respectively. In turn, the lifetimes of CH4, CO, and NO x will increase by 0.3%3.1% with regard to double emissions of CH4, 13.9%26.3% to double emissions of CO and decrease by 15.3%23.2% to double emissions of NO x .

Vidot, J., J. Landgraf, O. P. Hasekamp, A. Butz, A. Galli, P. Tol, and I. Aben (2012), Carbon monoxide from shortwave infrared reflectance measurements: A new  retrieval approach for clear sky and partially cloudy atmospheres, Remote Sens. Environ., 120, 255266, doi:10.1016/j.rse.2011.09.032.
The GMES atmospheric services include global and European air quality monitoring and forecasting which require near real time delivery of atmospheric CO abundances. To achieve this, a numerically efficient retrieval approach for operational data processing is needed to derive CO column densities from shortwave infrared measurements in the 2.3 mu m band of the Sentinel 5 missions and its Precursor mission. The expected performance of both spectrometers will allow for clear-sky CO column retrievals over land with a precision of <= 10% and an overall accuracy of <= 15% even for background CO abundance and low surface reflection in the shortwave infrared spectral range. In this context, we present a new algorithm approach of the retrieval of CO from shortwave infrared measurements in clear sky and partially cloudy atmospheres over land and ocean surfaces. The algorithm employs simplified radiative transfer, where the model atmosphere is separated in a clear sky part, and a part which is bounded below by an elevated Lambertian reflector to account for atmospheric scattering by clouds and aerosols. Within the inversion scheme, Tikhonov regularization is used to determine, for each individual measurement, not only the vertically integrated CO column density and its retrieval error, but also the column averaging kernel. For the retrieval, a prior estimate of methane abundance is used to characterize the light path by retrieving effective cloud parameters from the shortwave infrared band itself. A performance analysis shows that, for a single cloud layer in the middle and lower troposphere, the bias on the CO retrieval due to the Lambertian cloud model is less than 2-3%. The effect of boundary layer aerosols can also be treated with similar accuracy. In contrast, the presence of elevated dust plumes above bright surfaces or a single layer cirrus cloud causes significant errors and, in these cases, a reasonably low retrieval bias can only be achieved for an optical depth in the shortwave infrared spectral range lower than 0.4. Another relevant error source for the CO retrieval algorithm is given by the prior uncertainty of methane. It is found that a 5% uncertainty in the methane column density causes biases of 3-9% on the retrieved CO column, depending on cloud fraction. (C) 2012 Elsevier Inc. All rights reserved.

Worden, H. M., Y. Cheng, G. Pfister, G. R. Carmichael, Q. Zhang, D. G. Streets, M. Deeter, D. P. Edwards, J. C. Gille, and J. R. Worden (2012), Satellite-based estimates of reduced CO and CO2 emissions due to traffic  restrictions during the 2008 Beijing Olympics, Geophys. Res. Lett., 39, L14802, doi:10.1029/2012GL052395.
During the 2008 Olympics, the Chinese government made a significant effort to improve air quality in Beijing, including restrictions on traffic. Here we estimate the reductions in carbon monoxide (CO) and carbon dioxide (CO2) emissions resulting from the control measures on Beijing transportation. Using MOPITT (Measurements Of Pollution In The Troposphere) multispectral satellite observations of near-surface CO along with WRF-Chem (Weather Research and Forecasting model with Chemistry) simulations for Beijing during August, 2007 and 2008, we estimate changes in CO due to meteorology and transportation sector emissions. Applying a reported CO/CO2 emission ratio for fossil fuels, we find the corresponding reduction in CO2, 60 +/- 36 Gg[CO2]/day. As compared to emission scenarios being considered for the IPCC AR5 (Intergovernmental Panel on Climate Change, 5th Assessment Report), this result suggests that urban traffic controls on the Beijing Olympics scale could play a significant role in meeting target reductions for global CO2 emissions. Citation: Worden, H.M., Y. Cheng, G. Pfister, G.R. Carmichael, Q. Zhang, D.G. Streets, M. Deeter, D.P. Edwards, J.C. Gille, and J.R. Worden (2012), Satellite-based estimates of reduced CO and CO2 emissions due to traffic restrictions during the 2008 Beijing Olympics, Geophys. Res. Lett., 39, L14802, doi:10.1029/2012GL052395.

Yumimoto, K., and I. Uno (2012), Inverse Estimate of Long-Term CO Emission in China between 2005-2010 with Green’s Function Method, Journal of Japan Society for Atmospheric Environment/Taiki Kankyo Gakkaishi, 47(4), 162172.
Carbon monoxide (CO) emission amounts in China are inversely optimized with Green’s functions method, CO vertical profile measurements from MOPITT satellite instrument, and the GEOS-Chem chemical transport model (CTM) for the recent 6 years (2005 - 2010). Observations from surface sites (JMA and NOAA/GMD) are used for independent validation of a posteriori emissions. Model simulations with a posteriori emissions successfully reproduce the CO outflows from China to East China Sea and the Japanese archipelago in winter and spring, and compensate the under-estimates over the central eastern China region, considerably. A posteriori emissions in China exhibit significant seasonal variation in which the seasonal peak and bottom are found in winter-spring and summer, respectively. The CO emission in March is on average 54 % higher than in August. This seasonal cycle is consistent with other recent studies. Chinese CO sources obtained by the inversion are 164.5, 171.5, 180.8, 160.3, 152.5, and 156.1 Tg/year for 2005-2010, respectively, presenting inter-annual variations due to socioeconomic conditions (e.g., controls on pollutant emissions by the 2008 Beijing Olympic game and the global depression in 2009).

Zhang, Y., Y. Chen, G. Sarwar, and K. Schere (2012), Impact of gas-phase mechanisms on Weather Research Forecasting Model with Chemistry (WRF/Chem) predictions: Mechanism implementation and comparative evaluation, Journal of Geophysical Research: Atmospheres, 117(D1), doi:10.1029/2011JD015775. [online] Available from: .
Gas-phase mechanisms provide important oxidant and gaseous precursors for secondary aerosol formation. Different gas-phase mechanisms may lead to different predictions of gases, aerosols, and aerosol direct and indirect effects. In this study, WRF/Chem-MADRID simulations are conducted over the continental United States for July 2001, with three different gas-phase mechanisms, a default one (i.e., CBM-Z) and two newly implemented ones (i.e., CB05 and SAPRC-99). Simulation results are evaluated against available surface observations, satellite data, and reanalysis data. The model with these three gas-phase mechanisms gives similar predictions of most meteorological variables in terms of spatial distribution and statistics, but large differences exist in shortwave radiation and temperature and relative humidity at 2 m at individual sites under cloudy conditions, indicating the importance of aerosol semi-direct and indirect effects on these variables. Large biases exist in the simulated wind speed at 10 m, cloud water path, cloud optical thickness, and precipitation, due to uncertainties in current cloud microphysics and surface layer parameterizations. Simulations with all three gas-phase mechanisms well reproduce surface concentrations of O3, CO, NO2, and PM2.5, and column NO2. Larger biases exist in the surface concentrations of nitrate and organic matter (OM) and in the spatial distribution of column CO, tropospheric ozone residual, and aerosol optical depth, due to uncertainties in primary OM emissions, limitations in model representations of chemical transport, and radiative processes. Different gas-phase mechanisms lead to different predictions of mass concentrations of O3 (up to 5 ppb), PM2.5 (up to 0.5 μg m−3), secondary inorganic PM2.5 species (up to 1.1 μg m−3), organic PM (up to 1.8 μg m−3), and number concentration of PM2.5 (up to 2 × 104 cm−3). Differences in aerosol mass and number concentrations further lead to sizeable differences in simulated cloud condensation nuclei (CCN) and cloud droplet number concentration (CDNC) due to the feedback mechanisms among H2SO4 vapor, PM2.5 number, CCN, and CDNC through gas-phase chemistry, new particle formation via homogeneous nucleation, aerosol growth, and aerosol activation by cloud droplets. This study illustrates the important impact of gas-phase mechanisms on chemical and aerosol predictions, their subsequent effects on meteorological predictions, and a need for an accurate representation of such feedbacks through various atmospheric processes in the model. The online-coupled models that simulate feedbacks between meteorological variables and chemical species may provide more accurate representations of the real atmosphere for regulatory applications and can be applied to simulate chemistry-climate feedbacks over a longer period of time.

Zhao, Y., C. P. Nielsen, M. B. McElroy, L. Zhang, and J. Zhang (2012), CO emissions in China: Uncertainties and implications of improved energy efficiency and emission control, Atmospheric Environment, 49, 103113, doi:10.1016/j.atmosenv.2011.12.015.
A bottom-up methodology and an improved database of emission factors combining the latest domestic field measurements are developed to estimate the emissions of anthropogenic CO from China at national and provincial levels. The CO emission factors for major economic sectors declined to varying degrees from 2005 to 2009, attributed to improved energy efficiency and/or emission control regulations. Total national CO emissions are estimated at 173 Tg for 2005 and have been relatively stable for subsequent years, despite fast growth of energy consumption and industrial production. While industry and transportation sources dominated CO emissions in developed eastern and north-central China, residential combustion played a much greater role in the less developed western provinces. The uncertainties of national Chinese CO emissions are quantified using Monte Carlo simulation at -20% to +45% (95% confidence interval). Due to poor understanding of emission factors and activity levels for combustion of solid fuels, the largest uncertainties are found for emissions from the residential sector. The trends of bottom-up emissions compare reasonably to satellite observation of CO columns and to ground observations of CO2-CO correlation slopes. The increase in the ratio for emissions of CO2 relative to CO suggests that China has successfully improved combustion efficiencies across its economy in recent years, consistent with national policies to improve energy efficiency and to control criteria air pollutants.


Bouarar, I., K. S. Law, M. Pham, C. Liousse, H. Schlager, T. Hamburger, C. E. Reeves, J.-P. Cammas, P. Nédéléc, S. Szopa, F. Ravegnani, S. Viciani, F. D’Amato, A. Ulanovsky, and A. Richter (2011), Emission sources contributing to tropospheric ozone over Equatorial Africa during the summer monsoon, Atmos. Chem. Phys., 11(24), 1339513419, doi:10.5194/acp-11-13395-2011.
A global chemistry-climate model LMDz_INCA is used to investigate the contribution of African and Asian emissions to tropospheric ozone over Central and West Africa during the summer monsoon. The model results show that ozone in this region is most sensitive to lightning NOx and to Central African biomass burning emissions. However, other emission categories also contribute significantly to regional ozone. The maximum ozone changes due to lightning NOx occur in the upper troposphere between 400 hPa and 200 hPa over West Africa and downwind over the Atlantic Ocean. Biomass burning emissions mainly influence ozone in the lower and middle troposphere over Central Africa, and downwind due to westward transport. Biogenic emissions of volatile organic compounds, which can be uplifted from the lower troposphere to higher altitudes by the deep convection that occurs over West Africa during the monsoon season, lead to maximum ozone changes in the lower stratosphere region. Soil NOx emissions over the Sahel region make a significant contribution to ozone in the lower troposphere. In addition, convective uplift of these emissions and subsequent ozone production are also an important source of ozone in the upper troposphere over West Africa. Concerning African anthropogenic emissions, they only make a small contribution to ozone compared to the other emission categories. The model results indicate that most ozone changes due to African emissions occur downwind, especially over the Atlantic Ocean, far from the emission regions. The import of Asian emissions also makes a considerable contribution to ozone concentrations above 150 hPa and has to be taken into account in studies of the ozone budget over Africa. Using IPCC AR5 (Intergovernmental Panel on Climate Change; Fifth Assessment Report) estimates of anthropogenic emissions for 2030 over Africa and Asia, model calculations show larger changes in ozone over Africa due to growth in Asian emissions compared to African emissions over the next 20 yr.

Choi, Ji Hye, 한경만, 이소진, and 송철한 (2011a), Comparison of CO Profile and Total CO Columns Simulated from CMAQ with MOPITT Observation, 한국대기환경학회 학술대회논문집, 290290.
Choi, Ji Hye, 한경만, 이소진, and 송철한 (2011b), Comparison of Total CO Columns Simulated from Regional CTM with MOPITT Satellite Data, 한국대기환경학회 학술대회논문집, 336336.

Deeter, M. N., H. M. Worden, J. C. Gille, D. P. Edwards, D. Mao, and J. R. Drummond (2011), MOPITT multispectral CO retrievals: Origins and effects of geophysical radiance errors, Journal of Geophysical Research: Atmospheres, 116(D15), n/a-n/a, doi:10.1029/2011JD015703.
An obstacle to the simultaneous use of near-infrared (NIR) and thermal infrared (TIR) observations from the Measurements of Pollution in the Troposphere (MOPITT) instrument has been a lack of understanding of NIR radiance errors. Retrieval uncertainties produced by optimal estimation-based retrieval algorithms used for satellite instruments like MOPITT are only meaningful if radiance error statistics are accurately quantified in the measurement error covariance matrix. MOPITT’s gas correlation radiometers are subject to a unique form of “geophysical noise” due to the combined effects of (1) translational motion of the instrumental field of view during a single observation and (2) fine-scale spatial variability of surface radiative properties. We describe and demonstrate a new method for quantifying this source of error for each observation. Both TIR and NIR radiance errors due to this effect are highly variable, especially over land, but are qualitatively consistent with the variability of Moderate Resolution Imaging Spectroradiometer radiances in similar spectral bands. In addition, retrieval algorithm modifications are described which adjust the trade-off between smoothing error and retrieval noise within the optimal estimation framework. These modifications are necessary to fully exploit the information in MOPITT’s NIR channels. A case study based on MOPITT observations over Minnesota demonstrates significant improvement in retrieval performance as the result of the retrieval algorithm modifications.

Fokeeva, E. V., A. N. Safronov, V. S. Rakitin, L. N. Yurganov, E. I. Grechko, and R. A. Shumskii (2011), Investigation of the 2010 July-August fires impact on carbon monoxide  atmospheric pollution in Moscow and its outskirts, estimating of  emissions, Izv. Atmos. Ocean. Phys., 47(6), 682698, doi:10.1134/S0001433811060041.
We investigate the air pollution in the central European part of Russia during the 2010 summer fires. The results of ground-based (Institute of Atmospheric Physics (IAP), Moscow State University (MSU), and Zvenigorod Scientific Station (ZSS)) and satellite (MOPITT, AIRS, of Terra and Aqua satellites) measurements of the total content and concentration of carbon monoxide (CO), as well as MODIS data on the spatial and temporal distribution of forest and peat fires obtained from Terra and Aqua satellites, are presented. A comparison between similar situations in 2010 and 2002 revealed the causes of higher pollution levels in 2010. The use of trajectory analysis, detailed space imagery, and model calculations made it possible to reveal the location of peat fires and their contribution to the air pollution over the Moscow megalopolis. Fireemission estimates were obtained using two independent methods.

Fortems-Cheiney, A., F. Chevallier, I. Pison, P. Bousquet, S. Szopa, M. N. Deeter, and C. Clerbaux (2011), Ten years of CO emissions as seen from Measurements of Pollution in the Troposphere (MOPITT), Journal of Geophysical Research (Atmospheres), 116(d15), 5304, doi:10.1029/2010JD014416.
The Measurements of Pollution in the Troposphere (MOPITT) retrievals are used as top-down constraints in an inversion for global CO emissions, for the past 10 years (from March 2000 to December 2009), at 8 day and 3.75° × 2.75° (longitude, latitude) resolution. The method updates a standard prior inventory and yields large increments in terms of annual regional budgets and seasonality. Our validation strategy consists in comparing our posterior-modeled concentrations with several sets of independent measurements: surface measurements, aircraft, and satellite. The posterior emissions, with a global 10 year average of 1430 TgCO/yr, are 37% higher than the prior ones, built from the EDGAR 3.2 and the GFEDv2 inventories (1038 TgCO/yr on average). In addition, they present some significant seasonal variations in the Northern Hemisphere that are not present in our prior nor in others’ major inventories. Our results also exhibit some large interannual variability due to biomass burning emissions, climate, and socioeconomic factors; CO emissions range from 1504 TgCO (in 2007) to 1318 TgCO (in 2009).

Ghude, S. D., S. H. Kulkarni, P. S. Kulkarni, V. P. Kanawade, S. Fadnavis, S. Pokhrel, C. Jena, G. Beig, and D. Bortoli (2011a), Anomalous low tropospheric column ozone over Eastern India during the severe drought event of monsoon 2002: a case study, Environ Sci Pollut Res, 18(8), 14421455, doi:10.1007/s11356-011-0506-4.
Background, aim, and scope The present study is an attempt to examine some of the probable causes of the unusually low tropospheric column ozone observed over eastern India during the exceptional drought event in July 2002. Method We examined horizontal wind and omega (vertical velocity) anomalies over the Indian region to understand the large-scale dynamical processes which prevailed in July 2002. We also examined anomalies in tropospheric carbon monoxide (CO), an important ozone precursor, and observed low CO mixing ratio in the free troposphere in 2002 over eastern India. Results and discussion It was found that instead of a normal large-scale ascent, the air was descending in the middle and lower troposphere over a vast part of India. This configuration was apparently responsible for the less convective upwelling of precursors and likely caused less photochemical ozone formation in the free troposphere over eastern India in July 2002. Conclusion The insight gained from this case study will hopefully provide a better understanding of the process controlling the distribution of the tropospheric ozone over the Indian region.

Ghude, S. D., G. Beig, P. S. Kulkarni, V. P. Kanawade, S. Fadnavis, J. J. Remedios, and S. H. Kulkarni (2011b), Regional CO pollution over the Indian-subcontinent and various transport  pathways as observed by MOPITT, Int. J. Remote Sens., 32(21), 61336148, doi:10.1080/01431161.2010.507796.
We used day-side Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) retrievals (2000-2007) to examine the regional CO emission and its transport pathways during the summer/winter monsoon, with a specific focus on the Indian-subcontinent. It is observed that MOPITT CO retrievals at 850 hPa level in general show large scale features of CO emission in India, as reflected in the bottom-up inventory. In particular, high CO mixing ratios over the eastern north-eastern part of India, along the Indo-Gangetic (IG) region, and low CO mixing ratios over central India are generally captured from the MOPITT data. A strong plume with enhanced CO mixing ratios at 350 hPa is observed during the summer monsoon, demonstrating large scale vertical transport of the boundary layer CO from the Indian region into the upper troposphere. During winter outflow CO from the Indian region is found to be transported over the Arabian Sea and Bay of Bengal and reaches up to Saudi Arabia and north-eastern Africa. It is observed that emissions from Southeast Asia and the eastern north-eastern Indian region have the greatest impact over the Bay of Bengal and the eastern Indian Ocean, while emissions from the rest of India dominate over the Arabian Sea and the western Indian Ocean.

Gonzi, S., L. Feng, and P. I. Palmer (2011), Seasonal cycle of emissions of CO inferred from MOPITT profiles of CO: Sensitivity to pyroconvection and profile retrieval assumptions, Geophysical Research Letters, 38(8), n/a-n/a, doi:10.1029/2011GL046789.
We estimate monthly continental-scale CO emissions for 2006 by optimally fitting prior emissions used by the GEOS-Chem chemistry transport model to retrieved profile measurements of CO from the Measurement Of Pollution In The Troposphere (MOPITT) satellite instrument. We focus on the range of emission estimates obtained by using different versions of the MOPITT profile data, and by better describing enhanced vertical mixing of emissions from wildfires. We find that annual posterior CO emissions estimates for 2006 range from 1003 to 1180 Tg CO, within the range of prior estimates (1243 ± 617 Tg CO). We generally find larger differences in posterior CO emissions from using different versions of the MOPITT data than from improving the description of wildfires, with the exception of fires over Indonesia. Posterior emissions over regions with wildfires have a large seasonal cycle, as expected, which can be substantially different from prior emission estimates. We find GFEDv2 prior emissions underestimate the duration of the biomass burning season for North Africa by as much as 1 month. We also find posterior emissions over Indonesia are a factor of 2 higher than prior emissions (83 ± 42 Tg CO) in 2006 due to widespread fires during JulyDecember. Posterior emissions over Canada during 2006 are a factor of 23 higher than prior emissions (9 ± 4.6 Tg CO). We also find a seasonal cycle of CO emissions over North America and Europe, in agreement with previous studies, which is not described by prior emissions.

Hao, N., P. Valks, D. Loyola, Y. F. Cheng, and W. Zimmer (2011), Space-based measurements of air quality during the World Expo 2010 in Shanghai, Environ. Res. Lett., 6(4), 044004, doi:10.1088/1748-9326/6/4/044004.
During the World Exposition 2010 (Expo, from May to October), emission control measures were implemented in Shanghai and surrounding areas to improve the air quality. To evaluate the effect of these measures, we use the tropospheric NO2 column, aerosol optical thickness (AOT) and CO concentration observations from the satellite instruments GOME-2, MODIS and MOPITT, respectively. The analysis shows about 8% and 14% reductions of tropospheric NO2 columns and AOT respectively over Shanghai during the Expo period, compared to the past three years. A 12% reduction of CO concentration at 700 hPa over Shanghai and surrounding areas is found during the Expo period. On the other hand, the satellite measurements show increases of NO2 by 20% and AOT by 23% over Shanghai urban areas after the Expo (November 2010April 2011), when the short-term emission control measures were lifted. Our study indicates that the air quality measures were effective in Shanghai and surrounding provinces during the Expo period.

Hooghiemstra, P. B., M. C. Krol, J. F. Meirink, P. Bergamaschi, G. R. van der Werf, P. C. Novelli, I. Aben, and T. Röckmann (2011), Optimizing global CO emission estimates using a four-dimensional variational data assimilation system and surface network observations, Atmos. Chem. Phys., 11(10), 47054723, doi:10.5194/acp-11-4705-2011.
We apply a four-dimensional variational (4D-VAR) data assimilation system to optimize carbon monoxide (CO) emissions for 2003 and 2004 and to reduce the uncertainty of emission estimates from individual sources using the chemistry transport model TM5. The system is designed to assimilate large (satellite) datasets, but in the current study only a limited amount of surface network observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) is used to test the 4D-VAR system. By design, the system is capable to adjust the emissions in such a way that the posterior simulation reproduces background CO mixing ratios and large-scale pollution events at background stations. Uncertainty reduction up to 60% in yearly emissions is observed over well-constrained regions and the inferred emissions compare well with recent studies for 2004. However, with the limited amount of data from the surface network, the system becomes data sparse resulting in a large solution space. Sensitivity studies have shown that model uncertainties (e. g., vertical distribution of biomass burning emissions and the OH field) and the prior inventories used, influence the inferred emission estimates. Also, since the observations only constrain total CO emissions, the 4D-VAR system has difficulties in separating anthropogenic and biogenic sources in particular. The inferred emissions are validated with NOAA aircraft data over North America and the agreement is significantly improved from the prior to posterior simulation. Validation with the Measurements Of Pollution In The Troposphere (MOPITT) instrument version 4 (V4) shows a slight improved agreement over the well-constrained Northern Hemisphere and in the tropics (except for the African continent). However, the model simulation with posterior emissions underestimates MOPITT CO total columns on the remote Southern Hemisphere (SH) by about 10 %. This is caused by a reduction in SH CO sources mainly due to surface stations on the high southern latitudes.

Illingworth, S. M., J. J. Remedios, H. Boesch, S.-P. Ho, D. P. Edwards, P. I. Palmer, and S. Gonzi (2011), A comparison of OEM CO retrievals from the IASI and MOPITT instruments, Atmospheric Measurement Techniques, 4, 775793, doi:10.5194/amt-4-775-2011.
Observations of atmospheric carbon monoxide (CO) can only be made on continental and global scales by remote sensing instruments situated in space. One such instrument is the Infrared Atmospheric Sounding Interferometer (IASI), producing spectrally resolved, top-of-atmosphere radiance measurements from which CO vertical layers and total columns can be retrieved. This paper presents a technique for intercomparisons of satellite data with low vertical resolution. The example in the paper also generates the first intercomparison between an IASI CO data set, in this case that produced by the University of Leicester IASI Retrieval Scheme (ULIRS), and the V3 and V4 operationally retrieved CO products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument. The comparison is performed for a localised region of Africa, primarily for an ocean day-time configuration, in order to develop the technique for instrument intercomparison in a region with well defined a priori. By comparing both the standard data and a special version of MOPITT data retrieved using the ULIRS a priori for CO, it is shown that standard intercomparisons of CO are strongly affected by the differing a priori data of the retrievals, and by the differing sensitivities of the two instruments. In particular, the differing a priori profiles for MOPITT V3 and V4 data result in systematic retrieved profile changes as expected. An application of averaging kernels is used to derive a difference quantity which is much less affected by smoothing error, and hence more sensitive to systematic error. These conclusions are confirmed by simulations with model profiles for the same region. This technique is used to show that for the data that has been processed the systematic bias between MOPITT V4 and ULIRS IASI data, at MOPITT vertical resolution, is less than 7 % for the comparison data set, and on average appears to be less than 4 %. The results of this study indicate that intercomparisons of satellite data sets with low vertical resolution should ideally be performed with: retrievals using a common a priori appropriate to the geographic region studied; the application of averaging kernels to compute difference quantities with reduced a priori influence; and a comparison with simulated differences using model profiles for the target gas in the region.

Ito, A. (2011), Mega fire emissions in Siberia: potential supply of bioavailable iron  from forests to the ocean, Biogeosciences, 8(6), 16791697, doi:10.5194/bg-8-1679-2011.
Significant amounts of carbon and nutrients are released to the atmosphere due to large fires in forests. Characterization of the spatial distribution and temporal variation of the intense fire emissions is crucial for assessing the atmospheric loadings of trace gases and aerosols. This paper discusses issues of the representation of forest fires in the estimation of emissions and the application to an atmospheric chemistry transport model (CTM). The potential contribution of forest fires to the deposition of bioavailable iron (Fe) into the ocean is highlighted, with a focus on mega fires in eastern Siberia.  Satellite products of burned area, active fire, and land cover are used to estimate biomass burning emissions in conjunction with a biogeochemical model. Satellite-derived plume height from MISR is used for the injection height of boreal forest fire emissions. This methodology is applied to quantify fire emission rates in each three-dimensional grid location in the high latitude Northern Hemisphere (>30 degrees N latitude) over a 5-yr period from 2001 to 2005. There is large interannual variation in forest burned area during 2001-2005 (13-49 x 10(3) km(2) yr(-1)) which results in a corresponding variation in the annual emissions of carbon monoxide (CO) (14-81 Tg CO yr(-1)). Satellite observations of CO column from MOPITT are used to evaluate the model performance in simulating the spatial distribution and temporal variation of the fire emissions. The model results for CO enhancements due to eastern Siberian fires are in good agreement with MOPITT observations. These validation results suggest that the model using emission rates estimated in this work is able to describe the interannual changes in CO due to intense forest fires.  Bioavailable iron is derived from atmospheric processing of relatively insoluble iron from desert sources by anthropogenic pollutants (mainly sulfuric acid formed from oxidation of SO(2)) and from direct emissions of soluble iron from combustion sources. Emission scenarios for IPCC AR5 report (Intergovernmental Panel on Climate Change; Fifth Assessment Report) suggest that anthropogenic SO(2) emissions are suppressed in the future to improve air quality. In future warmer and drier climate, severe fire years such as 2003 may become more frequent in boreal regions. The fire emission rates estimated in this study are applied to the aerosol chemistry transport model to examine the relative importance of biomass burning sources of soluble iron compared to those from dust sources. The model reveals that extreme fire events contribute to a significant deposition of soluble iron (20-40 %) to downwind regions over the western North Pacific Ocean, compared to the dust sources with no atmospheric processing by acidic species. These results suggest that the supply of nutrients from large forest fires plays a role as a negative biosphere-climate feedback with regards to the ocean fertilization.

Jiang, Z., D. B. A. Jones, M. Kopacz, J. Liu, D. K. Henze, and C. Heald (2011), Quantifying the impact of model errors on top-down estimates of carbon monoxide emissions using satellite observations, J. Geophys. Res.-Atmos., 116(D15), doi:10.1029/2010JD015282. [online] Available from: .
We conduct inverse analyses of atmospheric CO, using the GEOS-Chem model and observations from the Measurement of Pollution in the Troposphere satellite instrument, to quantify the potential contribution of systematic model errors on top-down source estimates of CO. We assess how the specification of the source of CO from the oxidation of biogenic nonmethane volatile organic compounds (NMVOCs) in the inversion impacts the top-down estimates. Our results show that when the NMVOC source of CO is comparable to or larger than the combustion source, optimizing the CO from NMVOC emissions on larger spatial scales than the combustion emissions could result in significant overadjustment for the a posteriori CO emissions and could lead to negative sources of CO, such as we found for the top-down South American emissions in June. We quantify the impact of aggregation errors on the source estimates, associated with conducting the inversion at a lower resolution than the atmospheric model. We find that aggregating the emissions across spatial scales in which the a priori error in the emissions changes sign could introduce biases exceeding 20% in the flux estimates since the inversion cannot correct the a priori error by uniformly scaling the emissions across the region. We also use the GEOS-3 and GEOS-4 meteorological fields in GEOS-Chem to examine the impact of discrepancies in atmospheric transport and in the atmospheric OH distribution on the source estimates. We find that the differences in the OH distribution and transport fields associated with the GEOS-3 and GEOS-4 products introduce comparably large differences of as much as 20% in the source estimates. Our results indicate that mitigating systematic model error is critical for improving the accuracy of the inferred source estimates.

Kanakidou, M., N. Mihalopoulos, T. Kindap, U. Im, M. Vrekoussis, E. Gerasopoulos, E. Dermitzaki, A. Unal, M. Koçak, K. Markakis, D. Melas, G. Kouvarakis, A. F. Youssef, A. Richter, N. Hatzianastassiou, A. Hilboll, F. Ebojie, F. Wittrock, C. von Savigny, J. P. Burrows, A. Ladstaetter-Weissenmayer, and H. Moubasher (2011), Megacities as hot spots of air pollution in the East Mediterranean, Atmospheric Environment, 45(6), 12231235, doi:10.1016/j.atmosenv.2010.11.048.
This paper provides a comprehensive overview of the actual knowledge on the atmospheric pollution sources, transport, transformation and levels in the East Mediterranean. It focuses both on the background atmosphere and on the similarities and differences between the urban areas that exhibited important urbanization the past years: the two megacities Istanbul, Cairo and the Athens extended area. Ground-based observations are combined with satellite data and atmospheric modeling. The overall evaluation pointed out that long and regional range transport of natural and anthropogenic pollution sources have about similar importance with local sources for the background air pollution levels in the area.

Kaskaoutis, D. G., S. K. Kharol, N. Sifakis, P. T. Nastos, A. R. Sharma, K. V. S. Badarinath, and H. D. Kambezidis (2011), Satellite monitoring of the biomass-burning aerosols during the wildfires of August 2007 in Greece: Climate implications, Atmospheric Environment, 45(3), 716726, doi:10.1016/j.atmosenv.2010.09.043.
Biomass burning and associated emissions of aerosols into the atmosphere play a vital role in atmospheric composition and climate change. During summer of 2007, Greece faced the worst natural disaster recorded in recent decades in terms of human losses, number of fire outbreaks and extent of the estimated burned area (more than 12% of the total forested areas in Greece). The present study aims at analyzing the impact of these fire events in western Peloponnese on atmospheric aerosol concentrations using satellite data. MODIS-derived Aerosol Optical Depth (AOD), effective radius, Ångström exponent, mass concentration, cloud-condensation nuclei (CCN) and OMI Aerosol Index (AI), single scattering albedo, absorption and extinction optical depths were analyzed. MODIS data showed smoke plumes traversing thousands of kilometers southwards influencing the central Mediterranean as well as the north African coastal regions. These thick smoke plumes dramatically affected AOD and aerosol-mass concentrations over the region and altered the microphysical aerosol properties, such as the effective radius and absorption coefficient. Model calculations suggested that the shortwave radiation at the ground was reduced by ∼50 Wm2, while that at the top of the atmosphere was reduced by ∼20 Wm2 resulting in atmospheric heating of ∼30 Wm2 over the areas affected by the smoke plumes.

Konovalov, I. B., M. Beekmann, I. N. Kuznetsova, A. Yurova, and A. M. Zvyagintsev (2011), Atmospheric impacts of the 2010 Russian wildfires: integrating modelling and measurements of an extreme air pollution episode in the Moscow region, Atmos. Chem. Phys., 11(19), 1003110056, doi:10.5194/acp-11-10031-2011.
Numerous wildfires provoked by an unprecedented intensive heat wave caused continuous episodes of extreme air pollution in several Russian cities and densely populated regions, including the Moscow region. This paper analyzes the evolution of the surface concentrations of CO, PM10 and ozone over the Moscow region during the 2010 heat wave by integrating available ground based and satellite measurements with results of a mesoscale model. The CHIMERE chemistry transport model is used and modified to include the wildfire emissions of primary pollutants and the shielding effect of smoke aerosols on photolysis. The wildfire emissions are derived from satellite measurements of the fire radiative power and are optimized by assimilating data of ground measurements of carbon monoxide (CO) and particulate matter (PM10) into the model. It is demonstrated that the optimized simulations reproduce independent observations, which were withheld during the optimisation procedure, quite adequately (specifically, the correlation coefficient of daily time series of CO and PM10 exceeds 0.8) and that inclusion of the fire emissions into the model significantly improves its performance. The model results show that wildfires are the principal factor causing the observed air pollution episode associated with the extremely high levels of daily mean CO and PM10 concentrations (up to 10 mg m-3 and 700 μg m-3 in the averages over available monitoring sites, respectively), although accumulation of anthropogenic pollution was also favoured by a stagnant meteorological situation. Indeed, ozone concentrations were simulated to be episodically very large (>400 μg m-3) even when fire emissions were omitted in the model. It was found that fire emissions increased ozone production by providing precursors for ozone formation (mainly VOC), but also inhibited the photochemistry by absorbing and scattering solar radiation. In contrast, diagnostic model runs indicate that ozone concentrations could reach very high values even without fire emissions which provide ”fuel” for ozone formation, but, at the same time, inhibit it as a result of absorption and scattering of solar radiation by smoke aerosols. A comparison of MOPITT CO measurements and corresponding simulations indicates that the observed episodes of extreme air pollution in Moscow were only a part of a very strong perturbation of the atmospheric composition, caused by wildfires, over European Russia. It is estimated that 2010 fires in this region emitted ∼10 Tg CO, thus more than 85% of the total annual anthropogenic CO emissions. About 30% of total CO fire emissions in European Russia are identified as emissions from peat fires.

Li, L., and Y. Liu (2011), Space-borne and ground observations of the characteristics of CO pollution in Beijing, 20002010, Atmospheric Environment, 45(14), 23672372, doi:10.1016/j.atmosenv.2011.02.026.
Both the long-term and short-term variability of carbon monoxide (CO) pollution in Beijing metropolitan area, China are studied with 11 years of MOPITT observations and 10 years of ground measurements. The impact of the 2008 Beijing Olympic Games on regional air quality is also examined. MOPITT CO columns exhibit different temporal patterns from ground CO concentration measurements. MOPITT CO column in August has gradually increased from 2000 to 2007, even though ground level CO concentrations have significantly decreased due to continued local air pollution control effort. Both CO columns and ground CO concentrations were reduced due to strict albeit temporary emissions control measures from July to September 2008 to support the Beijing Olympic Games. However, the reduction of total CO columns (∼13%) was less pronounced than ground CO concentration (∼44%), indicating that local emission control effort was partially offset by the continuously deteriorating regional air quality. In addition, MOPITT CO mixing ratio profiles indicate a significant regional pattern at higher altitudes. CO total columns after 2008 show an overall increasing trend, in contrast to the decreasing trend observed in ground measurements.

Liu, C., S. Beirle, T. Butler, J. Liu, P. Hoor, P. Jöckel, M. Penning de Vries, A. Pozzer, C. Frankenberg, M. G. Lawrence, J. Lelieveld, U. Platt, and T. Wagner (2011), Application of SCIAMACHY and MOPITT CO total column measurements to evaluate model results over biomass burning regions and Eastern China, Atmos. Chem. Phys., 11(12), 60836114, doi:10.5194/acp-11-6083-2011.
We developed a new CO vertical column density product from near IR observations of the SCIAMACHY instrument onboard ENVISAT. For the correction of a temporally and spatially variable offset of the CO vertical column densities we apply a normalisation procedure based on coincident MOPITT (version 4) observations over the oceans. The resulting normalised SCIAMACHY CO data is well suited for the investigation of the CO distribution over continents, where important emission sources are located. We use only SCIAMACHY observations for effective cloud fractions below 20 %. Since the remaining effects of clouds can still be large (up to 100 %), we applied a cloud correction scheme which explicitly considers the cloud fraction, cloud top height and surface albedo of individual observations. The normalisation procedure using MOPITT data and the cloud correction substantially improve the agreement with independent data sets. We compared our new SCIAMACHY CO data set, and also observations from the MOPITT instrument, to the results from three global atmospheric chemistry models (MATCH, EMAC at low and high resolution, and GEOS-Chem); the focus of this comparison is on regions with strong CO emissions (from biomass burning or anthropogenic sources). The comparison indicates that over most of these regions the seasonal cycle is generally captured well but the simulated CO vertical column densities are systematically smaller than those from the satellite observations, in particular with respect to SCIAMACHY observations. Because SCIAMACHY is more sensitive to the lowest part of the atmosphere compared to MOPITT, this indicates that especially close to the surface the model simulations systematically underestimate the true atmospheric CO concentrations, probably caused by an underestimation of CO emissions by current emission inventories. For some biomass burning regions, however, such as Central Africa in July-August, model results are also found to be higher than the satellite observations.

McMillan, W. W., K. D. Evans, C. D. Barnet, E. S. Maddy, G. W. Sachse, and G. S. Diskin (2011), Validating the AIRS Version 5 CO Retrieval With DACOM In Situ  Measurements During INTEX-A and -B, IEEE Trans. Geosci. Remote Sensing, 49(7), 28022813, doi:10.1109/TGRS.2011.2106505.
Herein we provide a description of the atmospheric infrared sounder (AIRS) version 5 (v5) carbon monoxide (CO) retrieval algorithm and its validation with the DACOM in situ measurements during the INTEX-A and -B campaigns. All standard and support products in the AIRS v5 CO retrieval algorithm are documented. Building on prior publications, we describe the convolution of in situ measurements with the AIRS v5 CO averaging kernel and first-guess CO profile as required for proper validation. Validation is accomplished through comparison of AIRS CO retrievals with convolved in situ CO profiles acquired during the NASA Intercontinental Chemical Transport Experiments (INTEX) in 2004 and 2006. From 143 profiles in the northern mid-latitudes during these two experiments, we find AIRS v5 CO retrievals are biased high by 6%-10% between 900 and 300 hPa with a root-mean-square error of 8%-12%. No significant differences were found between validation using spiral profiles coincident with AIRS overpasses and in-transit profiles under the satellite track but up to 13 h off in time. Similarly, no significant differences in validation results were found for ocean versus land, day versus night, or with respect to retrieved cloud top pressure or cloud fraction.

Mu, M., J. T. Randerson, G. R. van der Werf, L. Giglio, P. Kasibhatla, D. Morton, G. J. Collatz, R. S. DeFries, E. J. Hyer, E. M. Prins, D. W. T. Griffith, D. Wunch, G. C. Toon, V. Sherlock, and P. O. Wennberg (2011), Daily and 3-hourly variability in global fire emissions and consequences for atmospheric model predictions of carbon monoxide, Journal of Geophysical Research: Atmospheres, 116(D24), n/a-n/a, doi:10.1029/2011JD016245.
Attribution of the causes of atmospheric trace gas and aerosol variability often requires the use of high resolution time series of anthropogenic and natural emissions inventories. Here we developed an approach for representing synoptic- and diurnal-scale temporal variability in fire emissions for the Global Fire Emissions Database version 3 (GFED3). We disaggregated monthly GFED3 emissions during 20032009 to a daily time step using Moderate Resolution Imaging Spectroradiometer (MODIS)-derived measurements of active fires from Terra and Aqua satellites. In parallel, mean diurnal cycles were constructed from Geostationary Operational Environmental Satellite (GOES) Wildfire Automated Biomass Burning Algorithm (WF_ABBA) active fire observations. Daily variability in fires varied considerably across different biomes, with short but intense periods of daily emissions in boreal ecosystems and lower intensity (but more continuous) periods of burning in savannas. These patterns were consistent with earlier field and modeling work characterizing fire behavior dynamics in different ecosystems. On diurnal timescales, our analysis of the GOES WF_ABBA active fires indicated that fires in savannas, grasslands, and croplands occurred earlier in the day as compared to fires in nearby forests. Comparison with Total Carbon Column Observing Network (TCCON) and Measurements of Pollution in the Troposphere (MOPITT) column CO observations provided evidence that including daily variability in emissions moderately improved atmospheric model simulations, particularly during the fire season and near regions with high levels of biomass burning. The high temporal resolution estimates of fire emissions developed here may ultimately reduce uncertainties related to fire contributions to atmospheric trace gases and aerosols. Important future directions include reconciling top-down and bottom up estimates of fire radiative power and integrating burned area and active fire time series from multiple satellite sensors to improve daily emissions estimates.

Mukherjee, C., P. S. Kasibhatla, and M. West (2011), Bayesian statistical modeling of spatially correlated error structure in atmospheric tracer inverse analysis, Atmos. Chem. Phys., 11(11), 53655382, doi:10.5194/acp-11-5365-2011.
We present and discuss the use of Bayesian modeling and computational methods for atmospheric chemistry inverse analyses that incorporate evaluation of spatial structure in model-data residuals. Motivated by problems of refining bottom-up estimates of source/sink fluxes of trace gas and aerosols based on satellite retrievals of atmospheric chemical concentrations, we address the need for formal modeling of spatial residual error structure in global scale inversion models. We do this using analytically and computationally tractable conditional autoregressive (CAR) spatial models as components of a global inversion framework. We develop Markov chain Monte Carlo methods to explore and fit these spatial structures in an overall statistical framework that simultaneously estimates source fluxes. Additional aspects of the study extend the statistical framework to utilize priors on source fluxes in a physically realistic manner, and to formally address and deal with missing data in satellite retrievals. We demonstrate the analysis in the context of inferring carbon monoxide (CO) sources constrained by satellite retrievals of column CO from the Measurement of Pollution in the Troposphere (MOPITT) instrument on the TERRA satellite, paying special attention to evaluating performance of the inverse approach using various statistical diagnostic metrics. This is developed using synthetic data generated to resemble MOPITT data to define a proof-of-concept and model assessment, and then in analysis of real MOPITT data. These studies demonstrate the ability of these simple spatial models to substantially improve over standard non-spatial models in terms of statistical fit, ability to recover sources in synthetic examples, and predictive match with real data.

Nair, P. R., L. M. David, I. A. Girach, and K. Susan George (2011), Ozone in the marine boundary layer of Bay of Bengal during post-winter period: Spatial pattern and role of meteorology, Atmospheric Environment, 45(27), 46714681, doi:10.1016/j.atmosenv.2011.05.040.
Ozone measurements were carried out in the marine environment of the Bay of Bengal during the post-winter months of MarchApril 2006, as part of the Integrated Campaign for Aerosols, gases and Radiation Budget. The ozone mixing ratio was found to be high over the northern/head BoB with a mean value of 27 ± 3 ppb and minimum over the mid-BoB with 12 ± 3 ppb. The spatial distribution was closely associated with the airflow pattern, airmass back trajectories and the boundary layer height. In this marine environment, meteorology, in particular, the water vapour content also played a significant role in governing the diurnal pattern of ozone in addition to photochemistry. Vertical transport is also partially responsible for the high ozone over the head BoB. The diurnal patterns were simulated using the chemical box model. The spatial map of marine boundary layer ozone was compared with that of tropospheric column ozone, NO2 and CO.

Nara, H., H. Tanimoto, Y. Nojiri, H. Mukai, J. Zeng, Y. Tohjima, and T. Machida (2011a), CO emissions from biomass burning in South-east Asia in the 2006 El Nino  year: shipboard and AIRS satellite observations, Environ. Chem., 8(2), 213223, doi:10.1071/EN10113.
Biomass burning is often associated with climate oscillations. For example, biomass burning in South-east Asia is strongly linked to El Nino-southern oscillation activity. During October and November of the 2006 El Nino year, a substantial increase in CO mixing ratios was detected over the Western tropical Pacific Ocean by shipboard observations routinely operated between Japan and Australia and New Zealand. Combining in-situ measurements, satellite observations, and an air trajectory model simulation, two high CO episodes were identified originating from biomass burning in Borneo, Sumatra, New Guinea, and Northern Australia. Between 15 degrees N and the Equator, marked CO enhancements were encountered associated with a significant correlation between CO and CO(2) and between CO and O(3). The Delta CO/Delta CO(2) ratio observed in the fire plume was considerably high (171 ppbv ppmv(-1)), suggesting substantial contributions from peat soil burning in Indonesia. In contrast, the Delta O(3)/Delta CO ratio was only 0.05 ppbv ppbv (1), indicating that net photochemical production of O(3) in the plume was negligible during long-range transport in the lower troposphere over the Western tropical North Pacific.

Nara, H., H. Tanimoto, Y. Nojiri, H. Mukai, T. Machida, and Y. Tohjima (2011b), Onboard measurement system of atmospheric carbon monoxide in the Pacific by voluntary observing ships, Atmospheric Measurement Techniques Discussions, doi:doi:10.5194/amtd-4-4505-2011. [online] Available from: .
Long-term monitoring of carbon monoxide (CO) mixing ratios in the atmosphere overthe Pacific Ocean is being carried out on commercial cargo vessels participating in theNational Institute for Environmental Studies Voluntary Observing Ships program. Theprogram provides a regular platform for measurement of atmospheric CO along four cruising routes: from Japan to Oceania, from Japan to the United States, from Japanto Canada, and from Japan to Southeast Asia. Flask samples are collected during ev-ery cruise for subsequent analysis in the laboratory, and in 2005, continuous shipboardCO measurements were initiated on three of the routes. Here, we describe the systemwe developed for onboard measurement of CO mixing ratios with a commercially available gas filter correlation CO analyzer. The fully automated system measures CO inambient air, and the detector sensitivity and background signals are calibrated by ref-erencing the measurements to a CO-in-air standard gas (∼1ppmv) and to CO-free airscrubbed with a catalyst, respectively. We examined the artificial production of CO inthe high-pressure working gas standards (CO balanced with purified air at ppmv levels) during storage by referencing the measurements to CO standard gases maintained asour primary scale before and after use on the ships. The onboard performance ofthe continuous CO measurement system was evaluated by comparing its data withdata from laboratory analyses of flask samples using gas chromatography with a re-duction gas detector. The reasonably good consistency between the two independent measurement methods demonstrated the good performance of both methods over thecourse of 35 yr. The continuous measurement system was more useful than the flasksampling method for regionally polluted air masses, which were often encountered onSoutheast Asian cruises.

Ott, L., S. Pawson, and J. Bacmeister (2011), An analysis of the impact of convective parameter sensitivity on simulated global atmospheric CO distributions, Journal of Geophysical Research: Atmospheres, 116(D21), n/a-n/a, doi:10.1029/2011JD016077.
In an effort to better understand how uncertainty in simulated convection propagates into simulations of global trace gas distributions, we have constructed an eight-member ensemble of simulations using NASA’s Goddard Earth Observing System Version 5 (GEOS-5) general circulation model (GCM). The ensemble was created by perturbing parameters in the model’s moist physics schemes found to strongly influence the magnitude of convective mass flux. Globally, ensemble spreads in column CO are typically small (less than 4% of the mean column value) and, in many areas, are not significantly different from internal model variability. The largest ensemble spreads are found near source regions and outflow pathways. At the majority of remote surface monitoring sites, the annual mean ensemble spread is less than 5%, indicating that these locations, which are often the basis of inversion studies, are relatively insensitive to uncertainty in the representation of convection. We also examine in greater detail two simulations in which the magnitude of convective mass flux is significantly altered. Changes to convective parameters strongly influence grid-scale vertical and turbulent transport processes in addition to convective mass flux. Despite large differences in the magnitude of convective mass fluxes, this compensating behavior by other model processes results in comparable atmospheric residence times in the two simulations and largely similar global CO distributions. The results indicate that convective mass flux is strongly related to other vertical transport processes in a GCM and cannot be viewed as entirely separate. Future studies of the role of convective transport need to consider the relationship between convective and total mass flux.

Parker, R. J., J. J. Remedios, D. P. Moore, and V. P. Kanawade (2011), Acetylene C2H 2 retrievals from MIPAS data and  regions of enhanced upper tropospheric concentrations in August 2003, Atmos. Chem. Phys., 11(19), 1024310257, doi:10.5194/acp-11-10243-2011.
Acetylene (C2H2) volume mixing ratios (VMRs) have been successfully retrieved from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) Level 1B radiances during August 2003, providing the first global map of such data and ratios to CO in the literature. The data presented here contain most information between 300 hPa and 100 hPa with systematic errors less than 10% at the upper levels. Random errors per point are less than 15% at lower levels and are closer to 30% at 100 hPa.

Pfister, G. G., J. Avise, C. Wiedinmyer, D. P. Edwards, L. K. Emmons, G. D. Diskin, J. Podolske, and A. Wisthaler (2011), CO source contribution analysis for California during ARCTAS-CARB, Atmos. Chem. Phys., 11(15), 75157532, doi:10.5194/acp-11-7515-2011.
Air pollution is of concern in many parts of California and is impacted by both local emissions and also by pollution inflow from the North Pacific Ocean. In this study, we use the regional chemical transport model WRF-Chem V3.2 together with the global Model for OZone and Related Chemical Tracers to examine the CO budget over California. We include model CO tracers for different emission sources in the models, which allow estimation of the relative importance of local sources versus pollution inflow on the distribution of CO at the surface and in the free troposphere. The focus of our study is on the 15 June-15 July 2008 time period, which coincides with the aircraft deployment of the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission over California. Model simulations are evaluated using these aircraft observations as well as satellite retrievals and surface observations of CO. Evaluation results show that the model overall predicts the observed CO fields well, but points towards an underestimate of CO from the fires in Northern California, which had a strong influence during the study period, and towards a slight overestimate of CO from pollution inflow and local anthropogenic sources. The analysis of the CO budget over California reveals that inflow of CO explains on average 99 +/- 11 ppbV of surface CO during the study period, compared to 61 +/- 95 ppbV for local anthropogenic direct emissions of CO and 84 +/- 194 ppbV for fires. In the free troposphere, the average CO contributions are estimated as 96 +/- 7 ppbV for CO inflow, 8 +/- 9 ppbV for CO from local anthropogenic sources and 18 +/- 13 ppbV for CO from fires. Accounting for the low bias in the CO fire emission inventory, the fire impact during the study period might have been up to a factor 4 higher than the given estimates.

Pommrich, R., R. Müller, J.-U. Grooß, P. Konopka, G. Günther, H.-C. Pumphrey, S. Viciani, F. D’Amato, and M. Riese (2011), Carbon monoxide as a tracer for tropical troposphere to stratosphere transport in the Chemical Lagrangian Model of the Stratosphere (CLaMS), Geoscientific Model Development Discussions, 4(2), 11851211, doi:10.5194/gmdd-4-1185-2011.
Variations in the mixing ratio of trace gases of tropospheric origin entering the stratosphere in the tropics are of interest for assessing both troposphere to stratosphere transport fluxes in the tropics and the impact on the composition of the tropical lower stratosphere of quasi-horizontal in-mixing into the tropical tropopause layer from the mid-latitude stratosphere. Here, we present a simplified chemistry scheme for the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the simulation, at comparatively low numerical cost, of CO, ozone, and long-lived trace substances (CH4, N2O, CCl3F, and CO2) in the lower tropical stratosphere. The boundary conditions at the ground are represented for the long-lived trace substances CH4, N2O, CCl3F, and CO2 based on ground-based measurements. The boundary condition for CO in the free troposphere is deduced from MOPITT measurements. We find that the zonally averaged tropical CO anomaly patterns simulated by this model version of CLaMS are in good agreement with observations. The introduction of a new scheme in the ECMWF integrated forecast system (Tompkins et al., 2007) for the ice supersaturation after September 2006, results in a somewhat less good agreement between observed and simulated CO patterns in the tropical lower stratosphere after this date.

Retnamayi, A., M. K. Ganapathy, and S. T. Santha (2011), Anomalous Variations in Atmospheric Carbon Monoxide Associated with the Tsunami, Asian Journal of Atmospheric Environment, 5(1), 4755, doi:10.5572/ajae.2011.5.1.047.
Anomalous Variations in Atmospheric Carbon Monoxide Associated with the Tsunami Carbon monoxide;Tsunami;Mixing ratio;Back trajectory;Enhancement; Variations in ambient atmospheric carbon monoxide(CO) observed at an inland mining site in the Indo-Gangetic plains, Jaduguda ($22^{circ}38’N$, $86^{circ}21’E$, 122m MSL, ~75 km away from the coast of the Bay of Bengal) during the Tsunami of 26 December 2004 were monitored. CO mixing ratio over this site was measured using a non-dispersive infrared analyzer (Monitor Europe Model 9830 B). Back trajectory analysis data obtained using NOAA Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model was also used for this study. Variations in CO mixing ratio at a coastal site, Thiruvananthapuram ($8^{circ}29’N$, $76^{circ}57’E$, located ~2 km from the Arabian Sea coast) have also been investigated using CO data retrieved from the Measurement Of Pollution In The Troposphere (MOPITT) instrument. Ground-based measurements indicated abnormal variations in CO mixing ratio at Jaduguda from 25 December 2004 evening (previous day of the Tsunami). MOPITT CO data showed an enhancement in CO mixing ratio over Thiruvananthapuram on the Tsunami day. Back trajectory analyses over Thiruvananthapuram and Jaduguda for a period of 10 days from $21^{st}$ to $30^{th}$ December 2004 depicted that there were unusual vertical movements of air from high altitudes from 25 December 2004 evening. CO as well as the back trajectory analyses data showed that the variations in the wind regimes and consequently wind driven transport are the most probable reasons for the enhancement in CO observed at Jaduguda and Thiruvananthapuram during the Tsunami.

Sikder, H. A., J. Suthawaree, S. Kato, and Y. Kajii (2011), Surface ozone and carbon monoxide levels observed at Oki, Japan: regional air pollution trends in East Asia, J. Environ. Manage., 92(3), 953959, doi:10.1016/j.jenvman.2010.10.062.
Simultaneous ground-based measurements of ozone and carbon monoxide were performed at Oki, Japan, from January 2001 to September 2002 in order to investigate the O(3) and CO characteristics and their distributions. The observations revealed that O(3) and CO concentrations were maximum in springtime and minimum in the summer. The monthly averaged concentrations of O(3) and CO were 60 and 234 ppb in spring and 23 and 106 ppb in summer, respectively. Based on direction, 5-day isentropic backward trajectory analysis was carried out to determine the transport path of air masses, preceding their arrival at Oki. Comparison between classified results from present work and results from the year 1994-1996 was carried out. The O(3) and CO concentration results of classified air masses in our analysis show similar concentration trends to previous findings; highest in the WNW/W, lowest in N/NE and medium levels in NW. Moreover, O(3) levels are higher and CO levels are lower in the present study in all categories.

Sitnov, S. A. (2011a), Aerosol optical thickness and the total carbon monoxide content over the  European Russia territory in the 2010 summer period of mass fires:  Interrelation between the variation in pollutants and meteorological  parameters, Izv. Atmos. Ocean. Phys., 47(6), 714728, doi:10.1134/S0001433811060156.
The spatial and temporal variabilities of the aerosol optical thickness (AOT) and the total carbon monoxide content (CO) in the period of development and weakening of mass forest and peatbog fires in the European Russia territory (ERT) in the summer of 2010 are investigated from data of the AOT and CO satellite observations. The intensities of aerosol and CO emissions in the period of mass fires and the ratio of the emission factors of aerosol particles and CO are estimated on the basis of calculations of the smoke and CO masses over the ERT. The interrelation between variations in the levels of the regional pollution by combustion products and the variability of meteorological parameters is investigated. Various aspects of the manifestation of radiation effects of aerosols are discussed. The synchronization of weekly signals of the AOT, CO, and meteorological parameters in the period of mass fires is noted.

Sitnov, S. A. (2011b), Analysis of satellite observations of aerosol optical properties and gaseous species over Central District of Russian Federation in the period of abnormally high, summer temperature and mass wild fires in 2010, Optika Atmosfery i Okeana, 24(7), 572581.
The optical properties of aerosol ( tau sub(0.55), omega sub(o.50), and absorbing aerosol index) and the contents of atmospheric gaseous species (CO, NO sub(2), SO sub(2), CH sub(2)O, O sub(3), H sub(2)O), obtained with the help of the satellite instruments MODIS, MOPITT, and OMI over the territory of the central region of Russian Federation (52-59 degree N, 29-45 degree E) in the period from April till September 2010 are analyzed. Abnormal increasing of temperature and the changes in atmospheric composition due to the forest and peatbog fires are clearly revealed in the interrelated changes of most of the atmospheric parameters. In the period from the middle of July till August, 7, the regionally averaged value of tau 0.55 was icreased more than by 20 times (from 0.09 to 2.12) and the CO total column was increased more than twice (from 1.9 times 10 super(18) to 4.0 times 10 super(18) molec. times cm super(-2)), while in July-August the tropospheric NO sub(2) content in 2010 was 65% higher than in 2009. The spatial-temporal evolution of aerosol characteristics and gaseous species before, during, and after mass wild fires is studied, as well as radiation effects of smoke are analyzed.

Sitnov, S. A. (2011c), Satellite monitoring of atmospheric gaseous species and optical characteristics of atmospheric aerosol over the European part of Russia in AprilSeptember 2010, Dokl. Earth Sc., 437(1), 368373, doi:10.1134/S1028334X11030081.
The results of satellite monitoring of carbon monoxide (CO₂), nitrogen dioxide (NO₂), formaldehyde (HCNO), water vapor (H₂O), and ozone (O₃), aerosol optical thickness (AOT) and Angström parameter (α) over the European part of Russia in April-September 2010 are presented. The interrelation between the changes of various atmospheric parameters and spatial distributions of atmospheric pollutants during the development of regional weather anomaly and the beginning of massive wildfires that led to smog in the region is analyzed.

Tilmes, S., L. K. Emmons, K. S. Law, G. Ancellet, H. Schlager, J.-D. Paris, H. E. Fuelberg, D. G. Streets, C. Wiedinmyer, G. S. Diskin, Y. Kondo, J. Holloway, J. P. Schwarz, J. R. Spackman, T. Campos, P. Nédélec, and M. V. Panchenko (2011), Source contributions to Northern Hemisphere CO and black carbon during spring and summer 2008 from POLARCAT and START08/preHIPPO observations and MOZART-4, Atmospheric Chemistry and Physics Discussions, 11(2), 59355983, doi:10.5194/acpd-11-5935-2011.
Anthropogenic pollution and wildfires are main producers of carbon monoxide (CO) and black carbon (BC) in the Northern Hemisphere. High concentrations of these compounds are transported into the Arctic troposphere, influencing the ecosystem in high northern latitudes and the global climate. The global chemical transport model MOZART-4 is used to quantify the seasonal evolution of the contribution of CO and BC from different source regions in spring and summer 2008 by tagging their emissions. Aircraft observations from the POLARCAT experiments, in particular NASA ARCTAS, NOAA ARCPAC, POLARCAT-France, DLR GRACE and YAK-AEROSIB, as well as the NSF START08/preHIPPO experiments during Spring-Summer 2008 are combined to quantify the representation of simulated tracer characteristics in anthropogenic and fire plumes. In general, the model reproduces CO and BC well. Based on aircraft measurements and FLEXPART back-trajectories, the altitude contribution of emissions coming from different source regions is well captured in the model. Uncertainties of the MOZART-4 model are identified by comparing the data with model results on the flight tracks and using MOPITT satellite observations. Anthropogenic emissions are underestimated by about 10% in high northern latitudes in spring, and shortcomings exist in simulating fire plumes. The remote impact of East-Siberian fire emissions is underestimated for spring, whereas the impact of Southeast Asian fire emissions to mid-latitude CO values is overestimated by the model. In summer, mid-latitude CO values agree well between model and observations, whereas summer high latitude East-Siberian fire emissions in the model are overestimated by 20% in comparison to observations in the region. On the other hand, CO concentrations are underestimated by about 30% over Alaska and Canada at altitudes above 4 km. BC values are overestimated by the model at altitudes above 4 km in summer. Based on MOZART-4, with tagged CO and BC tracers, anthropogenic emissions of Asia, Europe and the US have the largest contribution to the CO and BC in mid- and high latitudes in spring and summer. Southeast Asian, Chinese and Indian fires have a large impact on CO pollution in spring in low latitudes with a maximum between 20° and 30°, whereas Siberian fires contribute largely to the pollution in high latitudes, up to 10% in spring and up to 30% in summer. The largest contributions to BC values in high latitudes are from anthropogenic emissions (about 70%). CO and BC have larger mass loadings in April than in July, as a result of photochemistry and dynamics.

Xu, W. Y., C. S. Zhao, L. Ran, Z. Z. Deng, P. F. Liu, N. Ma, W. L. Lin, X. B. Xu, P. Yan, X. He, J. Yu, W. D. Liang, and L. L. Chen (2011), Characteristics of pollutants and their correlation to meteorological conditions at a suburban site in the North China Plain, Atmos. Chem. Phys., 11(9), 43534369, doi:10.5194/acp-11-4353-2011.
North China Plain (NCP) is one of the most densely populated regions in China and has experienced enormous economic growth in the past decades. Its regional trace gas pollution has also become one of the top environmental concerns in China. Measurements of surface trace gases, including O sub(3), NO sub(x), SO sub(2) and CO were carried out within the HaChi (Haze in China) project at Wuqing Meteorology Station, located between 2 mega-cities (Beijing and Tianjin) in the NCP, from 9 July 2009 to 21 January 2010. Detailed statistical analyses were made in order to provide information on the levels of the measured air pollutants and their characteristics. Gaseous air pollutant concentrations were also studied together with meteorological data and satellite data to help us better understand the causes of the observed variations in the trace gases during the field campaign. In comparison to measurements from other rural and background stations in the NCP, relatively high concentrations were detected in Wuqing, presumably due to regional mixing and transport of pollutants. Local meteorology had deterministic impacts on air pollution levels, which have to be accounted for when evaluating other effects on pollutant concentrations. Trace gas concentrations showed strong dependence on wind, providing information on regional pollution characteristics. O sub(3) mixing ratio also showed clear dependencies on temperature and relative humidity.

Yurganov, L. N., V. Rakitin, A. Dzhola, T. August, E. Fokeeva, M. George, G. Gorchakov, E. Grechko, S. Hannon, A. Karpov, L. Ott, E. Semutnikova, R. Shumsky, and L. Strow (2011), Satellite- and ground-based CO total column observations over 2010 Russian fires: accuracy of top-down estimates based on thermal IR satellite data, Atmos. Chem. Phys., 11(15), 79257942, doi:10.5194/acp-11-7925-2011.
CO total column data are presented from three space sounders and two ground-based spectrometers in Moscow and its suburbs during the forest and peat fires that occurred in Central Russia in July-August 2010. Also presented are ground-based in situ CO measurements. The Moscow area was strongly impacted by the CO plume from these fires. Concurrent satellite- and ground-based observations were used to quantify the errors of CO top-down emission estimates. On certain days, CO total columns retrieved from the data of the space-based sounders were 2-3 times less than those obtained from the ground-based sun-tracking spectrometers. The depth of the polluted layer over Moscow was estimated using total column measurements compared with CO volume mixing ratios in the surface layer and on the TV tower and found to be around 360 m. The missing CO that is the average difference between the CO total column accurately determined by the ground spectrometers and that retrieved by AIRS, MOPITT, and IASI was determined for the Moscow area between 1.6 and 3.3 × 1018 molec cm-2. These values were extrapolated onto the entire plume; subsequently, the CO burden (total mass) over Russia during the fire event was corrected. A top-down estimate of the total emitted CO, obtained by a simple mass balance model increased by 40-100 % for different sensors due to this correction. Final assessments of total CO emitted by Russian wildfires obtained from different sounders are between 34 and 40 Tg CO during July-August 2010.

Zhang, Y. (2011), Mean global and regional distributions of MOPITT carbon monoxide during 20002009 and during ENSO, Atmospheric Environment, 45(6), 13471358, doi:10.1016/j.atmosenv.2010.11.044.
The MOPITT (Measurements Of Pollution In The Troposphere) CO measurements over a 10-year period (20002009) reveal consistently positive trends on the order of 0.130.19 × 1016 mol cm−2 per month in CO total column concentrations over the entire globe and the hemispheres. Two maxima in globally averaged CO concentrations are identified: one in April and one in October, with two minima in July and December. These maxima and minima are attributable to the respective maxima and minima in CO concentrations over the Northern and Southern Hemispheres. Over the Tropics, maximum and minimum CO concentrations are noted in October and June, respectively, due primarily to biomass burning.  During El Niño DJF (DecemberJanuaryFebruary) and JJA (JuneJulyAugust), predominantly positive anomalies in CO total column are noted over the entire globe except for the high latitudes of both hemispheres and the central part of the South America where negative anomalies are identified. La Niña DJF and JJA are largely opposite to El Niño DJF and JJA in CO total column anomalies. Negative (positive) anomalies in CO total column tend to be associated with wet (dry) anomalies in precipitation over the major polluted areas during ENSO. It is suggested that changes in the atmospheric circulations during ENSO either enhance or weaken precipitation systems with the associated precipitation modulating CO total column. The correspondence between anomalies in CO total column and anomalies in Terra MODIS fire pixels during ENSO is rather poor over many parts of the world.


Arellano, A. F., P. G. Hess, D. P. Edwards, and D. Baumgardner (2010), Constraints on black carbon aerosol distribution from Measurement of Pollution in the Troposphere (MOPITT) CO, Geophysical Research Letters, 37(17), 17801, doi:10.1029/2010GL044416.
We present an approach to constrain simulated atmospheric black carbon (BC) using carbon monoxide (CO) observations. The approach uses: (1) the Community Atmosphere Model with Chemistry to simulate the evolution of BC and CO within an ensemble of model simulations; (2) satellite CO retrievals from the MOPITT/Terra instrument to assimilate observed CO into these simulations; (3) the derived sensitivity of BC to CO within these simulations to correct the simulated BC distributions. We demonstrate the performance of this approach through model experiments with and without the BC corrections during the period coinciding with the Intercontinental Chemical Transport Experiment (INTEX-B). Our results show significant improvements (∼50%) in median BC profiles using constraints from MOPITT, based on comparisons with INTEX-B measurements. We find that assimilating MOPITT CO provides considerable impact on simulated BC concentrations, especially over source regions. This approach offers an opportunity to augment our current ability to predict BC distributions.

Beirle, S., H. Huntrieser, and T. Wagner (2010), Direct satellite observation of lightning-produced NOx, Atmos. Chem. Phys., 10(22), 1096510986, doi:10.5194/acp-10-10965-2010.
Lightning is an important source of NO sub(x) in the free troposphere, especially in the tropics, with strong impact on ozone production. However, estimates of lightning NO sub(x) (LNO sub(x)) production efficiency (LNO sub(x) per flash) are still quite uncertain. In this study we present a systematic analysis of NO sub(2) column densities from SCIAMACHY measurements over active thunderstorms, as detected by the World-Wide Lightning Location Network (WWLLN), where the WWLLN detection efficiency was estimated using the flash climatology of the satellite lightning sensors LIS/OTD. Only events with high lightning activity are considered, where corrected WWLLN flash rate densities inside the satellite pixel within the last hour are above 1 /km super(2)/h. For typical SCIAMACHY ground pixels of 30 60 km super(2), this threshold corresponds to 1800 flashes over the last hour, which, for literature estimates of lightning NO sub(x) production, should result in clearly enhanced NO sub(2) column densities. From 2004-2008, we find 287 coincidences of SCIAMACHY measurements and high WWLLN flash rate densities. For some of these events, a clear enhancement of column densities of NO sub(2) could be observed, indeed. But overall, the measured column densities are below the expected values by more than one order of magnitude, and in most of the cases, no enhanced NO sub(2) could be found at all. Our results are in contradiction to the currently accepted range of LNO sub(x) production per flash of 15 (2-40)10 super(25) molec/flash. This probably partly results from the specific conditions for the events under investigation, i.e. events of high lightning activity in the morning (local time) and mostly (for 162 out of 287 events) over ocean. Within the detected coincidences, the highest NO sub(2) column densities were observed around the US Eastcoast. This might be partly due to interference with ground sources of NO sub(x) being uplifted by the convective systems. However, it could also indicate that flashes in this region are particularly productive. We conclude that current estimates of LNO sub(x) production might be biased high for two reasons. First, we observe a high variability of NO sub(2) for coincident lightning events. This high variability can easily cause a publication bias, since studies reporting on high NO sub(x) production have likely been published, while studies finding no or low amounts of NO sub(x) might have been rejected as errorneous or not significant. Second, many estimates of LNO sub(x) production in literature have been performed over the US, which is probably not representative for global lightning.

Bian, H., M. Chin, S. R. Kawa, H. Yu, T. Diehl, and T. Kucsera (2010), Multiscale carbon monoxide and aerosol correlations from satellite measurements and the GOCART model: Implication for emissions and atmospheric evolution, Journal of Geophysical Research: Atmospheres, 115(D7), n/a-n/a, doi:10.1029/2009JD012781.
Regional correlations of CO and aerosol on different time scales provide information on their sources, lifetimes, and transport pathways. We examine regional and global column CO and fine-mode aerosol optical depth (AODf) correlations from daily to seasonal scales using 7 years (20002006) of satellite observations from the Measurement of Pollution in the Troposphere and the Moderate Resolution Imaging Spectroradiometer and model simulations from the Goddard Chemistry Aerosol Radiative Transport model. Our analyses indicate that, globally, column CO and AODf have similar spatial distributions due to their common source locations, although CO is more spatially dispersed because of its longer lifetime. However, temporal CO-AODf correlations differ substantially over different timescales and different regions. On daily to synoptic scales CO and AODf have a positive correlation over the industrial and biomass burning source regions owing to the covariance of emissions and coherent dynamic transport. No such correlation is seen in remote regions because of the diverging influence of mixing and chemical processes during longer-range transport. On the seasonal scale in the Northern Hemisphere, CO and AODf are out of phase by 24 months. This phase lag is caused by photochemical production of sulfate, which is the major component of fine-mode aerosol in the Northern Hemisphere, and photochemical destruction of CO in reaction with OH (both at maximum in the summer and at minimum in the winter), together with the seasonality of fine-mode dust, which peaks in the boreal spring season. In the Southern Hemisphere tropics and subtropics, however, CO and AODf are generally in-phase because the variability is dominated by direct release from biomass burning emissions.

Choi, Y., G. Osterman, A. Eldering, Y. Wang, and E. Edgerton (2010), Understanding the contributions of anthropogenic and biogenic sources to CO enhancements and outflow observed over North America and the western Atlantic Ocean by TES and MOPITT, Atmospheric Environment, 44(16), 20332042, doi:10.1016/j.atmosenv.2010.01.029.
We investigate the effects of anthropogenic and biogenic sources on tropospheric CO enhancements and outflow over North America and the Atlantic during July August 2006, the 3rd warmest summer on record. The analysis is performed using the 3D Regional chEmical trAnsport Model (REAM), satellite data from TES on the Aura satellite, MOPITT on the Terra satellite and surface monitor data from the SEARCH network. The satellite measurements of CO provide insight into the location of regional CO enhancements along with the ability to resolve vertical features. Satellite and surface monitor data are used to compare with REAM, illustrating model’s ability to reproduce observed CO concentrations. The REAM model used in this study features CO emissions reduced by 50% from the 1999 EPA NEI and biogenic VOC emissions scaled by EPA-observed isoprene concentrations (20% reduction). The REAM simulations show large variations in surface CO, lower tropospheric CO and column CO, which are also observed by the surface observations and satellite data. Over the US, during July August 2006, the model estimates monthly CO production from anthropogenic sources (5.3 and 51 Tg CO) is generally larger than biogenic sources (4.3 and 3.5 Tg CO). However, the model shows that for very warm days, biogenic sources produce as much CO as anthropogenic sources, a result of increased biogenic production due to warmer temperatures. The satellite data show CO outflow occurs along the East Coast of the US and Canada in July and is more broadly distributed over the Atlantic in August. REAM results show the longitudinally exported CO enhancements from anthropogenic sources (3.3 and 3.9 Tg CO) are larger than biogenic sources (2 8 and 2.7 Tg CO) along the eastern boundary of REAM for July August 2006 We show that when compared with the impacts of both sources on increasing tropospheric CO exports, the relative Impacts in August are greater than in July because of preferable outflow transport (C) 2010 Elsevier Ltd. All rights reserved.

Claeyman, M., J.-L. Attié, L. El Amraoui, D. Cariolle, V.-H. Peuch, H. Teyssèdre, B. Josse, P. Ricaud, S. Massart, A. Piacentini, J.-P. Cammas, N. J. Livesey, H. C. Pumphrey, and D. P. Edwards (2010), A linear CO chemistry parameterization in a chemistry-transport model: evaluation and application to data assimilation, Atmos. Chem. Phys., 10(13), 60976115, doi:10.5194/acp-10-6097-2010.
This paper presents an evaluation of a new linear parameterization valid for the troposphere and the stratosphere, based on a first order approximation of the carbon monoxide (CO) continuity equation. This linear scheme (hereinafter noted LINCO) has been implemented in the 3-D Chemical Transport Model (CTM) MOCAGE (MOdele de Chimie Atmospherique Grande Echelle). First, a one and a half years of LINCO simulation has been compared to output obtained from a detailed chemical scheme output. The mean differences between both schemes are about +/- 25 ppbv (part per billion by volume) or 15% in the troposphere and +/- 10 ppbv or 100% in the stratosphere. Second, LINCO has been compared to diverse observations from satellite instruments covering the troposphere (Measurements Of Pollution In The Troposphere: MOPITT) and the stratosphere (Microwave Limb Sounder: MLS) and also from aircraft (Measurements of ozone and water vapour by Airbus in-service aircraft: MOZAIC programme) mostly flying in the upper troposphere and lower stratosphere (UTLS). In the troposphere, the LINCO seasonal variations as well as the vertical and horizontal distributions are quite close to MOPITT CO observations. However, a bias of similar to -40 ppbv is observed at 700 hPa between LINCO and MOPITT. In the stratosphere, MLS and LINCO present similar large-scale patterns, except over the poles where the CO concentration is underestimated by the model. In the UTLS, LINCO presents small biases less than 2% compared to independent MOZAIC profiles. Third, we assimilated MOPITT CO using a variational 3D-FGAT (First Guess at Appropriate Time) method in conjunction with MOCAGE for a long run of one and a half years. The data assimilation greatly improves the vertical CO distribution in the troposphere from 700 to 350 hPa compared to independent MOZAIC profiles. At 146 hPa, the assimilated CO distribution is also improved compared to MLS observations by reducing the bias up to a factor of 2 in the tropics. This study confirms that the linear scheme is able to simulate reasonably well the CO distribution in the troposphere and in the lower stratosphere. Therefore, the low computing cost of the linear scheme opens new perspectives to make free runs and CO data assimilation runs at high resolution and over periods of several years.

Clerbaux, C., S. Turquety, and P. Coheur (2010), Infrared remote sensing of atmospheric composition and air quality: Towards operational applications, Comptes Rendus Geoscience, 342(4), 349356, doi:10.1016/j.crte.2009.09.010.
Atmospheric remote sensing from satellites is an essential component of the observational strategy deployed to monitor atmospheric pollution and changing composition. During this decade, remote sensors using the thermal infrared (TIR) spectral range have demonstrated their ability to sound the troposphere and provide global distribution for some of the key atmospheric species. This article illustrates three operational applications made possible with the IASI instrument onboard the European satellite MetOp, which opens new perspectives for routine observation of the evolution of atmospheric composition from space. Résumé La télédétection par satellite est une composante essentielle de la stratégie d’observation déployée pour surveiller la pollution atmosphérique et l’évolution de l’atmosphère. Au cours de cette décennie, les sondeurs embarqués qui utilisent la région spectrale de l’infrarouge thermique pour sonder la troposphère ont démontré leur capacité à fournir des distributions globales pour quelques-unes des principales espèces atmosphériques. Cet article illustre trois applications opérationnelles rendues possible grâce à l’instrument IASI à bord du satellite européen MetOp, qui ouvrent de nouvelles perspectives pour l’observation systématique de l’évolution de la composition atmosphérique depuis l’espace.

Deeter, M. N., D. P. Edwards, J. C. Gille, L. K. Emmons, G. Francis, S.-P. Ho, D. Mao, D. Masters, H. Worden, J. R. Drummond, and P. C. Novelli (2010), The MOPITT version 4 CO product: Algorithm enhancements, validation, and  long-term stability, J. Geophys. Res.-Atmos., 115(D7), doi:10.1029/2009JD013005. [online] Available from: .
Vertical profiles of carbon monoxide (CO) concentration and corresponding total column values derived from measurements made by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument are now being processed operationally with the “version 4” (V4) retrieval algorithm. This algorithm exploits the results of analyses of in situ data, chemical transport modeling, and radiative transfer modeling in the MOPITT postlaunch era. Improvements in the V4 product are evident in both clean and polluted conditions. The new products are validated using CO in situ measurements acquired from aircraft from 2000 to 2007. As determined by both retrieval simulations and observations, retrieval bias drift is typically about 1 ppbv/yr for levels in the middle troposphere and about 2 ppbv/yr in the upper troposphere. Retrieval simulations indicate that observed bias drift may be the result of gradual on-orbit changes in the instrument’s modulation cell parameters.

Drummond, J. R., J. Zou, F. Nichitiu, J. Kar, R. Deschambaut, and J. Hackett (2010), A review of 9-year performance and operation of the MOPITT instrument, Advances in Space Research, 45(6), 760774, doi:10.1016/j.asr.2009.11.019.
The MOPITT (Measurements of Pollution in the Troposphere) instrument has provided more than nine years of global carbon monoxide (CO) measurements on a continuous basis since its launch aboard the Terra Spacecraft on December 18th, 1999. This paper gives an overview of the core sub-system performance and major issues of the in-flight instrument over the mission period. Some of the instrument anomalies are also discussed. The major successes are: (1) the concept of using a combination of correlation systems such as Length Modulated Cells (LMCs) and Pressure Modulated Cells (PMCs) to retrieve CO profiles in the troposphere; (2) the redundant design in the instrumentation which was crucial for coping with unexpected in-flight anomalies and for continuing the mission in the case of component failure; (3) the thermal environment on orbit that is so stable that some calibration procedures are not necessary; and (4) the recent production of CO total column retrieved from the MOPITT 2.3 μm channel.

Duflot, V., B. Dils, J. L. Baray, M. D. Mazière, J. L. Attié, G. Vanhaelewyn, C. Senten, C. Vigouroux, G. Clain, and R. Delmas (2010), Analysis of the origin of the distribution of CO in the subtropical southern Indian Ocean in 2007, Journal of Geophysical Research: Atmospheres, 115(D22), doi:10.1029/2010JD013994. [online] Available from: .
We show carbon monoxide (CO) distributions at different vertical levels over the subtropical southern Indian Ocean, analyzing an observation campaign using Fourier transform infrared (FTIR) solar absorption spectrometry performed in 2007 at Reunion Island (21°S, 55°E). The CO pollution levels detected by the FTIR measurements during the campaign show a doubling of the CO total columns during the Southern Hemisphere biomass burning season. Using correlative data from the Measurement of Pollution in the Troposphere instrument and back trajectories analyses, we show that the potential primary sources for CO throughout the troposphere in 2007 are southern Africa (JuneAugust) and South America (SeptemberOctober). A secondary potential contribution from Southeast Asia and Indonesia-Malaysia was identified in the upper troposphere, especially in July and September. We examine the relation between the Asian monsoon anticyclone seasonal cycle and this result. We also investigate the relative contribution of different areas across the globe to the CO concentration in the subtropical southern Indian Ocean in 2007 using backward simulations combining the Lagrangian model FLEXPART 6.2, the Global Fire Emissions Database (GFEDv2.1) and the Emission Database for Global Atmospheric Research (EDGARv3.2-FT2000). We confirm the predominance of the African and South American contributions in the CO concentration in the southern subtropical Indian Ocean below 11 km. We show that CO transported from Australia makes only a small contribution to the total CO concentration observed over Reunion Island, and that the long-range transport of CO coming from Southeast Asia and Indonesia-Malaysia is important, especially from June until September in the upper troposphere.

El Amraoui, L., J.-L. Attié, N. Semane, M. Claeyman, V.-H. Peuch, J. Warner, P. Ricaud, J.-P. Cammas, A. Piacentini, B. Josse, D. Cariolle, S. Massart, and H. Bencherif (2010), Midlatitude stratosphere troposphere exchange as diagnosed by MLS O3 and MOPITT CO assimilated fields, Atmos. Chem. Phys., 10(5), 21752194, doi:10.5194/acp-10-2175-2010.
This paper presents a comprehensive characterization of a very deep stratospheric intrusion which occurred over the British Isles on 15 August 2007. The signature of this event is diagnosed using ozonesonde measurements over Lerwick, UK (60.14° N, 1.19° W) and is also well characterized using meteorological analyses from the global operational weather prediction model of Météo-France, ARPEGE. Modelled as well as assimilated fields of both ozone (O3) and carbon monoxide (CO) have been used in order to better document this event. O3 and CO from Aura/MLS and Terra/MOPITT instruments, respectively, are assimilated into the three-dimensional chemical transport model MOCAGE of Météo-France using a variational 3-D-FGAT (First Guess at Appropriate Time) method. The validation of O3 and CO assimilated fields is done using self-consistency diagnostics and by comparison with independent observations such as MOZAIC (O3 and CO), AIRS (CO) and OMI (O3). It particularly shows in the upper troposphere and lower stratosphere region that the assimilated fields are closer to MOZAIC than the free model run. The O3 bias between MOZAIC and the analyses is -11.5 ppbv with a RMS of 22.4 ppbv and a correlation coefficient of 0.93, whereas between MOZAIC and the free model run, the corresponding values are 33 ppbv, 38.5 ppbv and 0.83, respectively. In the same way, for CO, the bias, RMS and correlation coefficient between MOZAIC and the analyses are -3.16 ppbv, 13 ppbv and 0.79, respectively, whereas between MOZAIC and the free model they are 6.3 ppbv, 16.6 ppbv and 0.71, respectively. The paper also presents a demonstration of the capability of O3 and CO assimilated fields to better describe a stratosphere-troposphere exchange (STE) event in comparison with the free run modelled O3 and CO fields. Although the assimilation of MLS data improves the distribution of O3 above the tropopause compared to the free model run, it is not sufficient to reproduce the STE event well. Assimilated MOPITT CO allows a better qualitative description of the stratospheric intrusion event. The MOPITT CO analyses appear more promising than the MLS O3 analyses in terms of their ability to capture a deep STE event. Therefore, the results of this study open the perspectives for using MOPITT CO in the STE studies.

Elguindi, N., H. Clark, C. Ordóñez, V. Thouret, J. Flemming, O. Stein, V. Huijnen, P. Moinat, A. Inness, V.-H. Peuch, A. Stohl, S. Turquety, G. Athier, J.-P. Cammas, and M. Schultz (2010), Current status of the ability of the GEMS/MACC models to reproduce the tropospheric CO vertical distribution as measured by MOZAIC, Geoscientific Model Development, 3, 501518, doi:10.5194/gmd-3-501-2010.
Vertical profiles of CO taken from the MOZAIC aircraft database are used to globally evaluate the performance of the GEMS/MACC models, including the ECMWF-Integrated Forecasting System (IFS) model coupled to the CTM MOZART-3 with 4DVAR data assimilation for the year 2004. This study provides a unique opportunity to compare the performance of three offline CTMs (MOZART-3, MOCAGE and TM5) driven by the same meteorology as well as one coupled atmosphere/CTM model run with data assimilation, enabling us to assess the potential gain brought by the combination of online transport and the 4DVAR chemical satellite data assimilation. First we present a global analysis of observed CO seasonal averages and interannual variability for the years 2002-2007. Results show that despite the intense boreal forest fires that occurred during the summer in Alaska and Canada, the year 2004 had comparably lower tropospheric CO concentrations. Next we present a validation of CO estimates produced by the MACC models for 2004, including an assessment of their ability to transport pollutants originating from the Alaskan/Canadian wildfires. In general, all the models tend to underestimate CO. The coupled model and the CTMs perform best in Europe and the US where biases range from 0 to -25% in the free troposphere and from 0 to -50% in the surface and boundary layers (BL). Using the 4DVAR technique to assimilate MOPITT V4 CO significantly reduces biases by up to 50% in most regions. However none of the models, even the IFS-MOZART-3 coupled model with assimilation, are able to reproduce well the CO plumes originating from the Alaskan/Canadian wildfires at downwind locations in the eastern US and Europe. Sensitivity tests reveal that deficiencies in the fire emissions inventory and injection height play a role.

Emmons, L. K., S. Walters, P. G. Hess, J.-F. Lamarque, G. G. Pfister, D. Fillmore, C. Granier, A. Guenther, D. Kinnison, T. Laepple, J. Orlando, X. Tie, G. Tyndall, C. Wiedinmyer, S. L. Baughcum, and S. Kloster (2010), Description and evaluation of the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4), Geoscientific Model Development, 3(1), 4367, doi:10.5194/gmd-3-43-2010.
The Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) is an offline global chemical transport model particularly suited for studies of the troposphere. The updates of the model from its previous version MOZART-2 are described, including an expansion of the chemical mechanism to include more detailed hydrocarbon chemistry and bulk aerosols. Online calculations of a number of processes, such as dry deposition, emissions of isoprene and monoterpenes and photolysis frequencies, are now included. Results from an eight-year simulation (20002007) are presented and evaluated. The MOZART-4 source code and standard input files are available for download from the NCAR Community Data Portal (

Ghude, S. D., P. S. Kulkarni, G. Beig, S. L. Jain, and B. C. Arya (2010), Global distribution of tropospheric ozone and its precursors: a view from space, Int. J. Remote Sens., 31(2), 485495, doi:10.1080/01431160902893519.
Satellite-borne tropospheric ozone measurements obtained from the tropospheric ozone residual (TOR) method, CO from the MOPITT (at 850 hPa level) measurements and NO(2) from the SCIAMACHY measurements for the three-year period 2003-2005 have been utilized to examine the distribution of the pollutant sources and long-range transport on a global scale. Elevated tropospheric ozone columns have been observed over regions of high NO2 and CO concentrations in the northern and southern hemispheres. High levels of the tropospheric ozone column have been observed below about 5 degrees S in the vicinity of the biomass burning regions and extend from continents out over the Atlantic during October. The seasonal distribution of tropospheric O(3) and its precursors in the southern hemisphere shows the strong correlation with the seasonal variation of biomass burning in Africa and South America. Northern hemisphere summer shows the widespread ozone and CO pollution throughout the middle latitudes. The inter-hemispheric gradient of ozone and CO found to be decreased during October. Large-scale transport of the ozone and CO over the Atlantic and Pacific Oceans has been clearly identified. Strong intercontinental transport has been observed to occur from west to east along with the mid-latitude winds in the northern hemisphere.

Imran Asatar, G., and P. R. Nair (2010), Spatial distribution of near-surface CO over bay of Bengal during winter: role of transport, Journal of Atmospheric and Solar-Terrestrial Physics, 72(17), 12411250, doi:10.1016/j.jastp.2010.07.025.
As part of Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB), cruise-based measurements of near-surface CO were carried out over Bay of Bengal (BoB) covering the latitudelongitude sector 3.5°N21.0°N and 76.0°E98.0°E, during winter months of December 2008 to January 2009. These in-situ measured CO mixing ratio varied in the range of 80480 ppbv over this marine environment with the distinct spatial pattern. The highest mixing ratios were measured over southeast-BoB with mean value of 379±58 ppbv. CO mixing ratios were high over north-BoB compared to southern BoB. These in-situ measurements were compared with the satellite-measured surface CO obtained from Measurements of Pollution in the Troposphere (MOPITT) onboard TERRA and found to be in good agreement over most of the regions, except at southeast-BoB. Surface CO and column CO from MOPITT data showed a similar spatial pattern. Based on the analysis of airmass back-trajectories, satellite-based spatial map of CO distribution over Asian region and Potential Source Contribution Function analysis, different pathways of transport of CO were identified. Transport from northern landmass as well as from south-east Asia has a significant influence in the spatial variation of CO over BoB. Winter-time mixing ratio of CO was found to be higher compared to those measured during other campaigns conducted during FebruaryMarch 1999, 2001 (pre-monsoon) and SeptemberOctober, 2002 (post-monsoon).

In, H.-J., and Y. P. Kim (2010), Estimation of the aerosol optical thickness distribution in the Northeast Asian forest fire episode in May 2003: Possible missing emissions, Atmospheric Research, 98(2), 261273, doi:10.1016/j.atmosres.2010.09.009.
During the study of the enhancement of aerosol optical thickness (AOT) which was derived by Community Multi-scale Air Quality (CMAQ) model for an active forest fire episode in Northeast Asia for May 2003 (In et al., 2009), it was found that CMAQ underestimated and overestimated AOT sporadically compared to the multiple satellite observations. Based on the AERONET surface AOT observation result, the WMO Global Telecommunications System (GTS) SYNOP system smoke/fire reports, and surface aerosol concentration data in Korea, it was found that these errors were resulted from missing of biomass burning emissions and coarse aerosols originating from soil. An inconsistency between surface observed and CMAQ estimate AOT and MODIS hot spot detects was found, which suggests that accuracy of MODIS fire products needs to be assessed in East Russian, China, and Korea in order to utilize them for national scale fire management in the region. The implement of origin and transport process of wind blown dust in current CMAQ is necessary to extend CMAQ capability in Northeast Asia.

Jacob, D. J., J. H. Crawford, H. Maring, A. D. Clarke, J. E. Dibb, L. K. Emmons, R. A. Ferrare, C. A. Hostetler, P. B. Russell, H. B. Singh, A. M. Thompson, G. E. Shaw, E. McCauley, J. R. Pederson, and J. A. Fisher (2010), The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission: design, execution, and first results, Atmos. Chem. Phys., 10(11), 51915212, doi:10.5194/acp-10-5191-2010.
The NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission was conducted in two 3-week deployments based in Alaska (April 2008) and western Canada (JuneJuly 2008). Its goal was to better understand the factors driving current changes in Arctic atmospheric composition and climate, including (1) influx of mid-latitude pollution, (2) boreal forest fires, (3) aerosol radiative forcing, and (4) chemical processes. The JuneJuly deployment was preceded by one week of flights over California (ARCTAS-CARB) focused on (1) improving state emission inventories for greenhouse gases and aerosols, (2) providing observations to test and improve models of ozone and aerosol pollution. ARCTAS involved three aircraft: a DC-8 with a detailed chemical payload, a P-3 with an extensive aerosol and radiometric payload, and a B-200 with aerosol remote sensing instrumentation. The aircraft data augmented satellite observations of Arctic atmospheric composition, in particular from the NASA A-Train. The spring phase (ARCTAS-A) revealed pervasive Asian pollution throughout the Arctic as well as significant European pollution below 2 km. Unusually large Siberian fires in April 2008 caused high concentrations of carbonaceous aerosols and also affected ozone. Satellite observations of BrO column hotspots were found not to be related to Arctic boundary layer events but instead to tropopause depressions, suggesting the presence of elevated inorganic bromine (510 pptv) in the lower stratosphere. Fresh fire plumes from Canada and California sampled during the summer phase (ARCTAS-B) indicated low NOx emission factors from the fires, rapid conversion of NOx to PAN, no significant secondary aerosol production, and no significant ozone enhancements except when mixed with urban pollution.

Kar, J., M. N. Deeter, J. Fishman, Z. Liu, A. Omar, J. K. Creilson, C. R. Trepte, M. A. Vaughan, and D. M. Winker (2010), Wintertime pollution over the Eastern Indo-Gangetic Plains as observed from MOPITT, CALIPSO and tropospheric ozone residual data, Atmos. Chem. Phys., 10(24), 1227312283, doi:10.5194/acp-10-12273-2010.
A large wintertime increase in pollutants has been observed over the eastern parts of the Indo Gangetic Plains. We use improved version 4 carbon monoxide (CO) retrievals from the Measurements of Pollution in the Troposphere (MOPITT) along with latest version 3 aerosol data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar instrument and the tropospheric ozone residual products to characterize this pollution pool. The feature is seen primarily in the lower troposphere from about November to February with strong concomitant increases in CO and aerosol optical depth (AOD). The signature of the feature is also observed in tropospheric ozone column data. The height resolved aerosol data from CALIPSO confirm the trapping of the pollution pool at the lowest altitudes. The observations indicate that MOPITT can capture this low altitude phenomenon even in winter conditions as indicated by the averaging kernels.

Kopacz, M., D. J. Jacob, J. A. Fisher, J. A. Logan, L. Zhang, I. A. Megretskaia, R. M. Yantosca, K. Singh, D. K. Henze, J. P. Burrows, M. Buchwitz, I. Khlystova, W. W. McMillan, J. C. Gille, D. P. Edwards, A. Eldering, V. Thouret, and P. Nedelec (2010), Global estimates of CO sources with high resolution by adjoint inversion of multiple satellite datasets (MOPITT, AIRS, SCIAMACHY, TES), Atmos. Chem. Phys., 10(3), 855876, doi:10.5194/acp-10-855-2010.
We combine CO column measurements from the MOPITT, AIRS, SCIAMACHY, and TES satellite instruments in a full-year (May 2004-April 2005) global inversion of CO sources at 4°×5° spatial resolution and monthly temporal resolution. The inversion uses the GEOS-Chem chemical transport model (CTM) and its adjoint applied to MOPITT, AIRS, and SCIAMACHY. Observations from TES, surface sites (NOAA/GMD), and aircraft (MOZAIC) are used for evaluation of the a posteriori solution. Using GEOS-Chem as a common intercomparison platform shows global consistency between the different satellite datasets and with the in situ data. Differences can be largely explained by different averaging kernels and a priori information. The global CO emission from combustion as constrained in the inversion is 1350 Tg a-1. This is much higher than current bottom-up emission inventories. A large fraction of the correction results from a seasonal underestimate of CO sources at northern mid-latitudes in winter and suggests a larger-than-expected CO source from vehicle cold starts and residential heating. Implementing this seasonal variation of emissions solves the long-standing problem of models underestimating CO in the northern extratropics in winter-spring. A posteriori emissions also indicate a general underestimation of biomass burning in the GFED2 inventory. However, the tropical biomass burning constraints are not quantitatively consistent across the different datasets.

de Laat, A. T. J., A. M. S. Gloudemans, I. Aben, and H. Schrijver (2010a), Global evaluation of SCIAMACHY and MOPITT carbon monoxide column differences for 20042005, Journal of Geophysical Research: Atmospheres, 115(D6), n/a-n/a, doi:10.1029/2009JD012698.
This paper presents a detailed global comparison of Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) and Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) column measurements for the years 2004 and 2005. Qualitatively, spatiotemporal variations of SCIAMACHY and MOPITT are similar. Quantitative comparisons have been performed taking the effects of instrument noise errors, vertical sensitivities via the averaging kernel and a priori, different spatiotemporal sampling and clouds into account using simulated CO profiles from the TM4 model. SCIAMACHY and MOPITT CO columns are similar over tropical, subtropical, and Northern Hemisphere oceans as well as over boreal regions where SCIAMACHY and MOPITT agree to within 10% or 2 × 1017 molecules/cm2. The short-wave infrared SCIAMACHY observations also provide information about lower tropospheric CO in Arctic and subarctic regions north of 60°N, where the MOPITT sensitivity is strongly reduced. South of 45°S, SCIAMACHY CO columns are 35 × 1017 molecules/cm2 smaller than MOPITT CO columns. Approximately 1.5 × 1017 molecules/cm2 (∼10%) of this difference is attributed to a bias in the SCIAMACHY CO columns, which is currently under investigation. The remaining difference is possibly related to MOPITT biases in this region. In the transition from oceans to dry desert regions, MOPITT CO total columns show a rapid increase of approximately 3 × 1017 molecules/cm2 (∼15%). While MOPITT and SCIAMACHY agree over oceans, MOPITT is approximately 5 × 1017 molecules/cm2 (∼25%) larger than SCIAMACHY results over dry land regions. The origin of this bias needs further investigation.

de Laat, A. T. J., A. M. S. Gloudemans, H. Schrijver, I. Aben, Y. Nagahama, K. Suzuki, E. Mahieu, N. B. Jones, C. Paton-Walsh, N. M. Deutscher, D. W. T. Griffith, M. De Mazière, R. L. Mittermeier, H. Fast, J. Notholt, M. Palm, T. Hawat, T. Blumenstock, F. Hase, M. Schneider, C. Rinsland, A. V. Dzhola, E. I. Grechko, A. M. Poberovskii, M. V. Makarova, J. Mellqvist, A. Strandberg, R. Sussmann, T. Borsdorff, and M. Rettinger (2010b), Validation of five years (2003-2007) of SCIAMACHY CO total column measurements using ground-based spectrometer observations, Atmospheric Measurement Techniques, 3(5), 14571471, doi:10.5194/amt-3-1457-2010.
This paper presents a validation study of SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum Likelihood Method (IMLM) algorithm using ground-based spectrometer observations from twenty surface stations for the five year time period of 2003-2007. Overall we find a good agreement between SCIAMACHY and ground-based observations for both mean values as well as seasonal variations. For high-latitude Northern Hemisphere stations absolute differences between SCIAMACHY and ground-based measurements are close to or fall within the SCIAMACHY CO 2 sigma precision of 0.2 x 10(18) molecules/cm(2) (similar to 10%) indicating that SCIAMACHY can observe CO accurately at high Northern Hemisphere latitudes. For Northern Hemisphere mid-latitude stations the validation is complicated due to the vicinity of emission sources for almost all stations, leading to higher ground-based measurements compared to SCIAMACHY CO within its typical sampling area of 8 degrees x 8 degrees. Comparisons with Northern Hemisphere mountain stations are hampered by elevation effects. After accounting for these effects, the validation provides satisfactory results. At Southern Hemisphere mid-to high latitudes SCIAMACHY is systematically lower than the ground-based measurements for 2003 and 2004, but for 2005 and later years the differences between SCIAMACHY and ground-based measurements fall within the SCIAMACHY precision. The 2003-2004 bias is consistent with previously reported results although its origin remains under investigation. No other systematic spatial or temporal biases could be identified based on the validation presented in this paper. Validation results are robust with regard to the choices of the instrument-noise error filter, sampling area, and time averaging required for the validation of SCIAMACHY CO total column measurements. Finally, our results show that the spatial coverage of the ground-based measurements available for the validation of the 2003-2007 SCIAMACHY CO columns is sub-optimal for validation purposes, and that the recent and ongoing expansion of the ground-based network by carefully selecting new locations may be very beneficial for SCIAMACHY CO and other satellite trace gas measurements validation efforts.

Lin, C.-Y., C.-C. Chang, C. Y. Chan, C. H. Kuo, W.-C. Chen, D. A. Chu, and S. C. Liu (2010a), Characteristics of springtime profiles and sources of ozone in the low troposphere over northern Taiwan, Atmospheric Environment, 44(2), 182193, doi:10.1016/j.atmosenv.2009.10.020.
To quantify the possible sources of the high ambient ozone concentration in the low troposphere over Taiwan, ozone sounding data from a two-year intensive field measurement program conducted in April and early May of 2004 and 2005 in northern Taiwan has been examined. We found that the vertical ozone distributions and occurrence of enhanced ozone in the lower troposphere (below 6 km) mainly resulted from (1)Type NE: the long-range transport of ozone controlled by the prevailing northeasterly winds below 2 km, (2)Type LO: the local photochemical ozone production process, and (3)Type SW: the strong southwest/westerly winds aloft (26 km). In the boundary layer (BL), where Asian continental outflow prevails, the average profile for type NE is characterized by a peak ozone concentration of nearly 65 ppb at about 1500 m altitude. For type LO, high ozone concentration with an average ozone concentration greater than 80 ppb was also found in the BL in the case of stagnant atmospheric and sunny weather conditions dominated. For type SW, significant ozone enhancement with average ozone concentration of 7085 ppb was found at around 4 km altitude. It is about 10 ppb greater than that of the types NE and LO at the same troposphere layer owing to the contribution of the biomass burning over Indochina. Due to Taiwan’s unique geographic location, the complex interaction of these ozone features in the BL and aloft, especially features associated with northeasterly and south/southwesterly winds, have resulted in complex characteristics of ozone distributions in the lower troposphere over northern Taiwan.

Lin, Y. C., C. Y. Lin, and W. T. Hsu (2010b), Observations of carbon monoxide mixing ratios at a mountain site in central Taiwan during the Asian biomass burning season, Atmospheric Research, 95(23), 270278, doi:10.1016/j.atmosres.2009.10.006.
Carbon monoxide (CO) mixing ratios were observed from 30 January to 7 April 2008 at Mt. Lulin (23.51°N, 120.92°E, 2862 m asl) in central Taiwan to investigate characteristics of CO during biomass burning periods. During the sampling campaign, the average mixing ratio of CO was 234 ± 63 ppb with higher levels observed in March. The elevated CO in March can, on the basis of backward trajectories and satellite fire spots analyses, possibly be attributed to biomass burning activities in the Asian continent. Significant diurnal variations of CO mixing ratios were observed at the remote site. The higher CO levels in the afternoon were influenced by the transport of boundary layer pollution to the site during daytime upslope flow. Backward trajectory analysis showed that air masses mainly originated from India (ID), the Indochina Peninsula (IP) and South Coastal China (SC), which together accounted for 85% of the total trajectories. Higher mixing ratios of CO were found in the ID, IP, and SC categories, indicating significant impacts of anthropogenic emissions on the Pacific region. Furthermore, the air parcels were divided into two categories, those that passed over the fire regions and those that did not. The result showed that the average difference of CO levels between the two categories was approximately 79 ppb, suggesting that Asian biomass burning plays an important role in CO levels at this remote site during the springtime.

Longo, K. M., S. R. Freitas, M. O. Andreae, A. Setzer, E. Prins, and P. Artaxo (2010), The Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) Part 2: Model sensitivity to the biomass burning inventories, Atmos. Chem. Phys., 10(13), 57855795, doi:10.5194/acp-10-5785-2010.
We describe an estimation technique for biomass burning emissions in South America based on a combination of remote-sensing fire products and field observations, the Brazilian Biomass Burning Emission Model (3BEM). For each fire pixel detected by remote sensing, the mass of the emitted tracer is calculated based on field observations of fire properties related to the type of vegetation burning. The burnt area is estimated from the instantaneous fire size retrieved by remote sensing, when available, or from statistical properties of the burn scars. The sources are then spatially and temporally distributed and assimilated daily by the Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) in order to perform the prognosis of related tracer concentrations. Three other biomass burning inventories, including GFEDv2 and EDGAR, are simultaneously used to compare the emission strength in terms of the resultant tracer distribution. We also assess the effect of using the daily time resolution of fire emissions by including runs with monthly-averaged emissions. We evaluate the performance of the model using the different emission estimation techniques by comparing the model results with direct measurements of carbon monoxide both near-surface and airborne, as well as remote sensing derived products. The model results obtained using the 3BEM methodology of estimation introduced in this paper show relatively good agreement with the direct measurements and MOPITT data product, suggesting the reliability of the model at local to regional scales.

Luo, M., C. Boxe, J. Jiang, R. Nassar, and N. Livesey (2010), Interpretation of Aura satellite observations of CO and aerosol index related to the December 2006 Australia fires, Remote Sensing of Environment, 114(12), 28532862, doi:10.1016/j.rse.2010.07.003.
Enhanced carbon monoxide (CO) in the upper troposphere (UT) is shown by nearly collocated Tropospheric Emission Spectrometer (TES) and Microwave Limb Sounder (MLS) measurements near and down-wind from the known wildfire region of SE Australia from December 12th19th, 2006. Enhanced ultraviolet (UV) aerosol index (AI) derived from the Ozone Monitoring Instrument (OMI) measurements correlates with these high CO concentrations. The Hybrid Single Particle Langrangian Integrated Trajectory (HYSPLIT) model back trajectories trace selected air parcels, where TES observes enhanced CO in the upper and lower troposphere, to the SE Australia fire region as their initial location. Simultaneously, they show a lack of vertical advection along their tracks. TES retrieved CO vertical profiles in the higher and lower southern latitudes are examined together with the averaging kernels and show that TES CO retrievals are most sensitive at approximately 300400 hPa. The enhanced CO observed by TES in the upper (215 hPa) and lower (681 hPa) troposphere are, therefore, influenced by mid-tropospheric CO. GEOS-Chem model simulations with an 8-day emission inventory, as the wildfire source over Australia, are sampled to the TES/MLS observation times and locations. These simulations only show CO enhancements in the lower troposphere near and down-wind from the wildfire region of SE Australia with drastic underestimates of UT CO plumes. Although CloudSat along-track ice-water content curtains are examined to see whether possible vertical convection events can explain the high UT CO values, sparse observations of collocated Aura CO and CloudSat along-track ice-water content measurements for the single event precludes any conclusive correlation. Vertical convection that uplifts the fire-induced CO (i.e., most notably referred to as pyro-cumulonimbus (pyroCb)) may provide an explanation for the incongruence between these simulations and the TES/MLS observations of enhanced CO in the UT.

Mieville, A., C. Granier, C. Liousse, B. Guillaume, F. Mouillot, J.-F. Lamarque, J.-M. Grégoire, and G. Pétron (2010), Emissions of gases and particles from biomass burning during the 20th century using satellite data and an historical reconstruction, Atmospheric Environment, 44(11), 14691477, doi:10.1016/j.atmosenv.2010.01.011.
A new dataset of emissions of trace gases and particles resulting from biomass burning has been developed for the historical and the recent period (19002005). The purpose of this work is to provide a consistent gridded emissions dataset of atmospheric chemical species from 1900 to 2005 for chemistry-climate simulations. The inventory is built in two steps. First, fire emissions are estimated for the recent period (19972005) using satellite products (GBA2000 burnt areas and ATSR fire hotspots); the temporal and spatial distribution of the CO2 emissions for the 19972005 period is estimated through a calibration of ATSR fire hotspots. The historical inventory, covering the 19002000 period on a decadal basis, is derived from the historical reconstruction of burned areas from Mouillot and Field (2005). The historical emissions estimates are forced, for each main ecosystem, to agree with the recent inventory estimates, ensuring consistency between past and recent emissions. The methodology used for estimating the fire emissions is discussed, together with the time evolution of biomass burning emissions during the 20th century, first at the global scale and then for specific regions. The results are compared with the distributions provided by other inventories and results of inverse modeling studies.

Moon, Y.-S., and J. R. Drummond (2010), Enhancement of Ozone and Carbon Monoxide Associated with Upper Cut-off Low during Springtime in East Asia, Journal of Korean Society for Atmospheric Environment, 26(5), 475489, doi:10.5572/KOSAE.2010.26.5.475.
Enhancement of Ozone and Carbon Monoxide Associated with Upper Cut-off Low during Springtime in East Asia Total column density of CO;Total column amounts of ozone;Upper cut-off low;Vortex anomalies;Catalytic chemical reaction; In order to verify the enhancement of ozone and carbon monoxide (CO) during springtime in East Asia, we investigated weather conditions and data from remote sensors, air quality models, and air quality monitors. These include the geopotential height archived from the final (FNL) meteorological field, the potential vorticity and the wind velocity simulated by the Meteorological Mesoscale Model 5 (MM5), the back trajectory estimated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the total column amount of ozone and the aerosol index retrieved from the Total Ozone Mapping Spectrometer (TOMS), the total column density of CO retrieved from the Measurement of Pollution in the Troposphere (MOPITT), and the concentration of ozone and CO simulated by the Model for Ozone and Related Chemical Tracers (MOZART). In particular, the total column density of CO, which mightoriginate from the combustion of fossil fuels and the burning of biomass in China, increased in East Asia during spring 2000. In addition, the enhancement of total column amounts of ozone and CO appeared to be associated with both the upper cut-off low near 500 hPa and the frontogenesis of a surface cyclone during a weak Asian dust event. At the same time, high concentrations of ozone and CO on the Earth’s surface were shown at the Seoul air quality monitoring site, located at the surface frontogenesis in Korea. It was clear that the ozone was invaded by the downward stretched vortex anomalies, which included the ozone-rich airflow, during movement and development of the cut-off low, and then there was the catalytic photochemical reaction of ozone precursors on the Earth’s surface during the day. In addition, air pollutants such as CO and aerosol were tracked along both the cyclone vortex and the strong westerly as shown at the back trajectory in Seoul and Busan, respectively. Consequently, the maxima of ozone and CO between the two areas showed up differently because of the time lag between those gases, including their catalytic photochemical reactions together with the invasion from the upper troposphere, as well as the path of their transport from China during the weak Asian dust event.

Nam, J., Y. Wang, C. Luo, and D. A. Chu (2010), Trans-Pacific transport of Asian dust and CO: accumulation of biomass burning CO in the subtropics and dipole structure of transport, Atmos. Chem. Phys., 10(7), 32973308, doi:10.5194/acp-10-3297-2010.
In May 2003, both MODIS aerosol optical depth (AOD) and carbon monoxide (CO) measurements from MOPITT show significant trans-Pacific transport to North America. We apply the global chemical transport model, GEOS-Chem, to analyze the main features of the long-range transport events. Enhancements of MOPITT CO over the tropical Pacific are much broader than MODIS AOD enhancements. We find in model simulations that a major fraction of the CO enhancements in the subtropics in May is due to biomass burning in Southeast Asia in April. Biomass burning CO was recirculated into the subtropical high-pressure system and lingered for a much longer period than aerosols transported at higher latitudes. Simulated AOD enhancements are due to a combination of dust, sulfate, and organic and elemental carbons. Dust contribution dominates the AOD enhancements in early May. Model results indicate that dust transport takes place at higher altitude than the other aerosols. MODIS observations indicate a bias in model simulated pathway of dust transport in one out of the three cases analyzed. Sensitivities of dust transport pathways are analyzed in the model. The dipole structure of transport, consisting of the Aleutian Low to the north and the Pacific High to the south, over the Pacific is found to be a key factor. The placement of the dipole structure relative to model parameters such as up-stream wind field and source location may lead to the high sensitivity of simulated transport pathways.

Ordóñez, C., N. Elguindi, O. Stein, V. Huijnen, J. Flemming, A. Inness, H. Flentje, E. Katragkou, P. Moinat, V.-H. Peuch, A. Segers, V. Thouret, G. Athier, M. van Weele, C. S. Zerefos, J.-P. Cammas, and M. G. Schultz (2010), Global model simulations of air pollution during the 2003 European heat wave, Atmos. Chem. Phys., 10(2), 789815, doi:10.5194/acp-10-789-2010.
Three global Chemistry Transport Models - MOZART, MOCAGE, and TM5 - as well as MOZART coupled to the IFS meteorological model including assimilation of ozone (O3) and carbon monoxide (CO) satellite column retrievals, have been compared to surface measurements and MOZAIC vertical profiles in the troposphere over Western/Central Europe for summer 2003. The models reproduce the meteorological features and enhancement of pollution during the period 2-14 August, but not fully the ozone and CO mixing ratios measured during that episode. Modified normalised mean biases are around -25% (except ∼5% for MOCAGE) in the case of ozone and from -80% to -30% for CO in the boundary layer above Frankfurt. The coupling and assimilation of CO columns from MOPITT overcomes some of the deficiencies in the treatment of transport, chemistry and emissions in MOZART, reducing the negative biases to around 20%. The high reactivity and small dry deposition velocities in MOCAGE seem to be responsible for the overestimation of O3 in this model. Results from sensitivity simulations indicate that an increase of the horizontal resolution to around 1°×1° and potential uncertainties in European anthropogenic emissions or in long-range transport of pollution cannot completely account for the underestimation of CO and O3 found for most models. A process-oriented TM5 sensitivity simulation where soil wetness was reduced results in a decrease in dry deposition fluxes and a subsequent ozone increase larger than the ozone changes due to the previous sensitivity runs. However this latest simulation still underestimates ozone during the heat wave and overestimates it outside that period. Most probably, a combination of the mentioned factors together with underrepresented biogenic emissions in the models, uncertainties in the modelling of vertical/horizontal transport processes in the proximity of the boundary layer as well as limitations of the chemistry schemes are responsible for the underestimation of ozone (overestimation in the case of MOCAGE) and CO found in the models during this extreme pollution event.

Pfister, G. G., L. K. Emmons, D. P. Edwards, A. Arellano, G Sachse, and T. Campos (2010), Variability of springtime transpacific pollution transport during 20002006: the INTEX-B mission in the context of previous years, Atmos. Chem. Phys., 10(3), 13451359, doi:10.5194/acp-10-1345-2010.
We analyze the transport of pollution across the Pacific during the NASA INTEX-B (Intercontinental Chemical Transport Experiment Part B) campaign in spring 2006 and examine how this year compares to the time period for 2000 through 2006. In addition to aircraft measurements of carbon monoxide (CO) collected during INTEX-B, we include in this study multi-year satellite retrievals of CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument and simulations from the chemistry transport model MOZART-4. Model tracers are used to examine the contributions of different source regions and source types to pollution levels over the Pacific. Additional modeling studies are performed to separate the impacts of inter-annual variability in meteorology and dynamics from changes in source strength. Interannual variability in the tropospheric CO burden over the Pacific and the US as estimated from the MOPITT data range up to 7% and a somewhat smaller estimate (5%) is derived from the model. When keeping the emissions in the model constant between years, the year-to-year changes are reduced (2%), but show that in addition to changes in emissions, variable meteorological conditions also impact transpacific pollution transport. We estimate that about 1/3 of the variability in the tropospheric CO loading over the contiguous US is explained by changes in emissions and about 2/3 by changes in meteorology and transport. Biomass burning sources are found to be a larger driver for inter-annual variability in the CO loading compared to fossil and biofuel sources or photochemical CO production even though their absolute contributions are smaller. Source contribution analysis shows that the aircraft sampling during INTEX-B was fairly representative of the larger scale region, but with a slight bias towards higher influence from Asian contributions.

Reeves, C. E., P. Formenti, C. Afif, G. Ancellet, J.-L. Attié, J. Bechara, A. Borbon, F. Cairo, H. Coe, S. Crumeyrolle, F. Fierli, C. Flamant, L. Gomes, T. Hamburger, C. Jambert, K. S. Law, C. Mari, R. L. Jones, A. Matsuki, M. I. Mead, J. Methven, G. P. Mills, A. Minikin, J. G. Murphy, J. K. Nielsen, D. E. Oram, D. J. Parker, A. Richter, H. Schlager, A. Schwarzenboeck, and V. Thouret (2010), Chemical and aerosol characterisation of the troposphere over West Africa during the monsoon period as part of AMMA, Atmos. Chem. Phys., 10(16), 75757601, doi:10.5194/acp-10-7575-2010.
During June, July and August 2006 five aircraft took part in a campaign over West Africa to observe the aerosol content and chemical composition of the troposphere and lower stratosphere as part of the African Monsoon Multidisciplinary Analysis (AMMA) project. These are the first such measurements in this region during the monsoon period. In addition to providing an overview of the tropospheric composition, this paper provides a description of the measurement strategy (flights performed, instrumental payloads, wing-tip to wing-tip comparisons) and points to some of the important findings discussed in more detail in other papers in this special issue.  The ozone data exhibits an “S” shaped vertical profile which appears to result from significant losses in the lower troposphere due to rapid deposition to forested areas and photochemical destruction in the moist monsoon air, and convective uplift of ozone-poor air to the upper troposphere. This profile is disturbed, particularly in the south of the region, by the intrusions in the lower and middle troposphere of air from the southern hemisphere impacted by biomass burning. Comparisons with longer term data sets suggest the impact of these intrusions on West Africa in 2006 was greater than in other recent wet seasons. There is evidence for net photochemical production of ozone in these biomass burning plumes as well as in urban plumes, in particular that from Lagos, convective outflow in the upper troposphere and in boundary layer air affected by nitrogen oxide emissions from recently wetted soils. This latter effect, along with enhanced deposition to the forested areas, contributes to a latitudinal gradient of ozone in the lower troposphere. Biogenic volatile organic compounds are also important in defining the composition both for the boundary layer and upper tropospheric convective outflow.  Mineral dust was found to be the most abundant and ubiquitous aerosol type in the atmosphere over Western Africa. Data collected within AMMA indicate that injection of dust to altitudes favourable for long-range transport (i.e. in the upper Sahelian planetary boundary layer) can occur behind the leading edge of mesoscale convective system (MCS) cold-pools. Research within AMMA also provides the first estimates of secondary organic aerosols across the West African Sahel and have shown that organic mass loadings vary between 0 and 2 μg m−3 with a median concentration of 1.07 μg m−3. The vertical distribution of nucleation mode particle concentrations reveals that significant and fairly strong particle formation events did occur for a considerable fraction of measurement time above 8 km (and only there). Very low concentrations were observed in general in the fresh outflow of active MCSs, likely as the result of efficient wet removal of aerosol particles due to heavy precipitation inside the convective cells of the MCSs. This wet removal initially affects all particle size ranges as clearly shown by all measurements in the vicinity of MCSs.

Sharma, Anu Rani, Shailesh Kumar Kharol, K. V. S. Badarinath, and Darshan Singh (2010), Impact of agriculture crop residue burning on atmospheric aerosol loading a study over Punjab State, India, Ann. Geophys., 28(2), 367379, doi:10.5194/angeo-28-367-2010.
The present study deals with the impact of agriculture crop residue burning on aerosol properties during October 2006 and 2007 over Punjab State, India using ground based measurements and multi-satellite data. Spectral aerosol optical depth (AOD) and Ångström exponent (α) values exhibited larger day to day variation during crop residue burning period. The monthly mean Ångström exponent “α” and turbidity parameter “β” values during October 2007 were 1.31±0.31 and 0.36±0.21, respectively. The higher values of “α” and “β” suggest turbid atmospheric conditions with increase in fine mode aerosols over the region during crop residue burning period. AURA-OMI derived Aerosol Index (AI) and Nitrogen dioxide (NO2) showed higher values over the study region during October 2007 compared to October 2006 suggesting enhanced atmospheric pollution associated with agriculture crop residue burning.

Singh, R. P., J. Senthil Kumar, J. Zlotnicki, and M. Kafatos (2010), Satellite detection of carbon monoxide emission prior to the Gujarat earthquake of 26 January 2001, Applied Geochemistry, 25(4), 580585, doi:10.1016/j.apgeochem.2010.01.014.
NOAA AVHRR images have clearly shown anomalous changes in land surface temperature associated with earthquakes in the past two decades. Soon after the Gujarat earthquake of January 26, 2001, an anomalous increase in land surface temperature was inferred from MODIS satellite data a few days prior to the main earthquake event. The cause of such an anomalous change in surface temperature prior to the earthquake is attributed to many probable phenomena, but no definite cause has been identified. In the present study, changes of a complementary nature were found of land surface temperature associated with the emission of CO from the epicentral region. The observed changes on land and atmosphere associated with the Gujarat earthquake of 26 January, 2001, show the existence of strong coupling between land, atmosphere and ionosphere.

Srivastava, S., S. Lal, D. B. Subrahamanyam, S. Gupta, S. Venkataramani, and T. A. Rajesh (2010), Seasonal variability in mixed layer height and its impact on trace gas distribution over a tropical urban site: Ahmedabad, Atmospheric Research, 96(1), 7987, doi:10.1016/j.atmosres.2009.11.015.
Altitude profiles of virtual potential temperature (θv) and specific humidity (q) derived from meteorological data obtained from balloon-borne radiosonde ascents are used to investigate the seasonal variations in mixed layer height over Ahmedabad (23.03°N, 72.54°E), an urban site located on the western part of India. A total of 82 balloon ascents were conducted fortnightly in the morning hours during a period of about four years spanning from April 2003 to July 2007. Analysis of the vertical profiles of θv and q reveals a systematic seasonal variability in the mixed layer height (MLH), showing the decreasing trend from summermonsoon to winter season. The MLH is observed to be maximum (∼ 1170 m) in summermonsoon while a minimum (∼ 160 m) is observed during the winter months. In general, the mixed layer height was found to be highly variant during pre-monsoon and summermonsoon seasons. This variability is observed to be comparatively lower in the post-monsoon and winter months. Effects of MLH have been investigated on the variations in surface ozone and MOPITT derived surface and vertical distributions of CO. The reverse trend is observed in surface ozone and CO with mixed layer seasonal variability. The impact of MLH over CO vertical distributions is observed up to an altitude of 34 km.

Stroppiana, D., P. A. Brivio, J.-M. Grégoire, C. Liousse, B. Guillaume, C. Granier, A. Mieville, M. Chin, and G. Pétron (2010), Comparison of global inventories of CO emissions from biomass burning derived from remotely sensed data, Atmos. Chem. Phys., 10(24), 1217312189, doi:10.5194/acp-10-12173-2010.
We compare five global inventories of monthly CO emissions named VGT, ATSR, MODIS, GFED3 and MOPITT based on remotely sensed active fires and/or burned area products for the year 2003. The objective is to highlight similarities and differences by focusing on the geographical and temporal distribution and on the emissions for three broad land cover classes (forest, savanna/grassland and agriculture). Globally, CO emissions for the year 2003 range between 365 Tg CO (GFED3) and 1422 Tg CO (VGT). Despite the large uncertainty in the total amounts, some common spatial patterns typical of biomass burning can be identified in the boreal forests of Siberia, in agricultural areas of Eastern Europe and Russia and in savanna ecosystems of South America, Africa and Australia. Regionally, the largest difference in terms of total amounts (CV > 100%) and seasonality is observed at the northernmost latitudes, especially in North America and Siberia where VGT appears to overestimate the area affected by fires. On the contrary, Africa shows the best agreement both in terms of total annual amounts (CV = 31%) and of seasonality despite some overestimation of emissions from forest and agriculture observed in the MODIS inventory. In Africa VGT provides the most reliable seasonality. Looking at the broad land cover types, the range of contribution to the global emissions of CO is 64-74%, 23-32% and 3-4% for forest, savanna/grassland and agriculture, respectively. These results suggest that there is still large uncertainty in global estimates of emissions and it increases if the comparison is carried by out taking into account the temporal (month) and spatial (0.5° × 0.5° cell) dimensions. Besides the area affected by fires, also vegetation characteristics and conditions at the time of burning should also be accurately parameterized since they can greatly influence the global estimates of CO emissions.

Warner, J. X., Z. Wei, L. L. Strow, C. D. Barnet, L. C. Sparling, G. Diskin, and G. Sachse (2010), Improved agreement of AIRS tropospheric carbon monoxide products with other EOS sensors using optimal estimation retrievals, Atmos. Chem. Phys., 10(19), 95219533, doi:10.5194/acp-10-9521-2010.
We present in this paper an alternative retrieval algorithm for the Atmospheric Infrared Sounder (AIRS) tropospheric Carbon Monoxide (CO) products using the Optimal Estimation (OE) technique, which is different from the AIRS operational algorithm. The primary objective for this study was to compare AIRS CO, as well as the other retrieval properties such as the Averaging Kernels (AKs), the Degrees of Freedom for Signal (DOFS), and the error covariance matrix, against the Tropospheric Emission Spectrometer (TES) and the Measurement of Pollution in the Troposphere (MOPITT) CO, which were also derived using the OE technique. We also demonstrate that AIRS OE CO results are much more realistic than AIRS V5 operational CO, especially in the lower troposphere and in the Southern Hemisphere (SH). These products are validated with in situ profiles obtained by the Differential Absorption Carbon Monoxide Measurements (DACOM), which took place as part of NASA’s Intercontinental Chemical Transport Experiment (INTEX-B) field mission that was conducted over the northern Pacific in Spring 2006. To demonstrate the differences existing in the current operational products we first show a detailed direct comparison between AIRS V5 and TES operational V3 CO for the global datasets from December 2005 to July 2008. We then present global CO comparisons between AIRS OE, TES V3, and MOPITT V4 at selected pressure levels as well as for the total column amounts. We conclude that the tropospheric CO retrievals from AIRS OE and TES V3 agree to within 510 ppbv or 5% on average globally and throughout the free troposphere. The agreements in total column CO amounts between AIRS OE and MOPITT V4 have improved significantly compared to AIRS V5 with global relative RMS differences now being 12.7%.

Worden, H. M., M. N. Deeter, D. P. Edwards, J. C. Gille, J. R. Drummond, and P. Nédélec (2010), Observations of near-surface carbon monoxide from space using MOPITT multispectral retrievals, Journal of Geophysical Research (Atmospheres), 115(d14), 18314, doi:10.1029/2010JD014242.
Using both thermal infrared (TIR) and near infrared (NIR) channels of MOPITT (Measurements of Pollution in the Troposphere) on EOS-Terra, we demonstrate the first coincident multispectral retrievals of carbon monoxide (CO) from space. Exploiting both TIR and NIR channels has been possible due to recent progress in characterizing NIR channel radiance errors. This has allowed us to trade off sensitivity to near surface CO for larger random errors in the combined retrieval. By examining retrieval diagnostics such as DFS (degrees of freedom for signal) and averaging kernels for the multispectral retrieval (TIR + NIR) as compared to the TIR-only retrieval, we find that adding the NIR channel to the retrieval significantly increases sensitivity to CO, especially near the surface, but with high spatial variability due to surface albedo variations. The cases with the largest increases in DFS are over regions with low thermal contrast between the surface and lower atmosphere. In the tropics (23.4°S-23.4°N), the fraction of daytime land cases with at least 0.4 DFS in the surface layer (surface to 800 hPa) is 20% for TIR-only retrievals compared to 59% for multispectral retrievals. Vertical resolution for the surface layer is also improved, in some cases from around 6 km for TIR-only to roughly 1 km for TIR + NIR. Since we apply a single a priori CO profile (unlike MOPITT V4) and error covariance in all the retrievals reported here, these increases are due solely to the addition of the NIR channel. Enhanced sensitivity to near surface CO is especially evident in a case study for central/east Asia where source regions for urban areas with high population density are clearly identifiable. Although these retrievals are still a research product and require further validation and scientific evaluation, they demonstrate the increased sensitivity to CO in the lowermost troposphere that can be obtained from multispectral MOPITT data.

Yurganov, L., W. McMillan, E. Grechko, and A. Dzhola (2010), Analysis of global and regional CO burdens measured from space between 2000 and 2009 and validated by ground-based solar tracking spectrometers, Atmos. Chem. Phys., 10(8), 34793494, doi:10.5194/acp-10-3479-2010.
Interannual variations in AIRS and MOPITT retrieved CO burdens are validated, corrected, and compared with CO emissions from wild fires from the Global Fire Emission Dataset (GFED2) inventory. Validation of daily mean CO total column (TC) retrievals from MOPITT version 3 and AIRS version 5 is performed through comparisons with archived TC data from the Network for Detection of Atmospheric Composition Change (NDACC) ground-based Fourier Transform Spectrometers (FTS) between March 2000 and December 2007. MOPITT V3 retrievals exhibit an increasing temporal bias with a rate of 1.4-1.8% per year; thus far, AIRS retrievals appear to be more stable. For the lowest CO values in the Southern Hemisphere (SH), AIRS TC retrievals overestimate FTS TC by 20%. MOPITT’s bias and standard deviation do not depend on CO TC absolute values. Empirical corrections are derived for AIRS and MOPITT retrievals based on the observed annually averaged bias versus the FTS TC. Recently published MOPITT V4 is found to be in a good agreement with MOPITT V3 corrected by us (with exception of 2000-2001 period). With these corrections, CO burdens from AIRS V5 and MOPITT V3 (as well as MOPITT V4) come into good agreement in the mid-latitudes of the Northern Hemisphere (NH) and in the tropical belt. In the SH, agreement between AIRS and MOPITT CO burdens is better for the larger CO TC in austral winter and worse in austral summer when CO TC are smaller. Before July 2008, all variations in retrieved CO burden can be explained by changes in fire emissions. After July 2008, global and tropical CO burdens decreased until October before recovering by the beginning of 2009. The NH CO burden also decreased but reached a minimum in January 2009 before starting to recover. The decrease in tropical CO burdens is explained by lower than usual fire emissions in South America and Indonesia. This decrease in tropical emissions also accounts for most of the change in the global CO burden. However, no such diminution of NH biomass burning is indicated by GFED2. Thus, the CO burden decrease in the NH could result from a combination of lower fossil fuel emissions during the global economic recession and transport of CO-poor air from the tropics. More extensive modeling will be required to fully resolve this issue.

Zhang, Y., X.-Y. Wen, and C. J. Jang (2010a), Simulating chemistryaerosolcloudradiationclimate feedbacks over the continental U.S. using the online-coupled Weather Research Forecasting Model with chemistry (WRF/Chem), Atmospheric Environment, 44(29), 35683582, doi:10.1016/j.atmosenv.2010.05.056.
The chemistryaerosolcloudradiationclimate feedbacks are simulated using WRF/Chem over the continental U.S. in January and July 2001. Aerosols can reduce incoming solar radiation by up to −9% in January and −16% in July and 2-m temperatures by up to 0.16 °C in January and 0.37 °C in July over most of the continental U.S. The NO2 photolysis rates decrease in July by up to −8% over the central and eastern U.S. where aerosol concentrations are high but increase by up to 7% over the western U.S. in July and up to 13% over the entire domain in January. Planetary boundary layer (PBL) height reduces by up to −23% in January and −24% in July. Temperatures and wind speeds in July in big cities such as Atlanta and New York City reduce at/near surface but increase at higher altitudes. The changes in PBL height, temperatures, and wind speed indicate a more stable atmospheric stability of the PBL and further exacerbate air pollution over areas where air pollution is already severe. Aerosols can increase cloud optical depths in big cities in July, and can lead to 5005000 cm−3 cloud condensation nuclei (CCN) at a supersaturation of 1% over most land areas and 10500 cm−3 CCN over ocean in both months with higher values over most areas in July than in January, particularly in the eastern U.S. The total column cloud droplet number concentrations are up to 4.9 × 106 cm−2 in January and up to 11.8 × 106 cm−2 in July, with higher values over regions with high CCN concentrations and sufficient cloud coverage. Aerosols can reduce daily precipitation by up to 1.1 mm day−1 in January and 19.4 mm day−1 in July thus the wet removal rates over most of the land areas due to the formation of small CCNs, but they can increase precipitation over regions with the formation of large/giant CCN. These results indicate potential importance of the aerosol feedbacks and an urgent need for their accurate representations in current atmospheric models to reduce uncertainties associated with climate change predictions.

Zhang, Y., S. C. Olsen, and M. K. Dubey (2010b), WRF/Chem simulated springtime impact of rising Asian emissions on air quality over the U.S., Atmospheric Environment, 44(24), 27992812, doi:10.1016/j.atmosenv.2010.05.003.
This paper examines the impact of tripled anthropogenic emissions from China and India over the base level (gaseous species and carbonaceous aerosols for 2000) on air quality over the U.S. using the WRF/Chem (Weather Research and Forecasting Chemistry) model at 1° resolution. WRF/Chem is a state-of-the-science, fully coupled chemistry and meteorology system suitable for simulating the transport and dispersion of pollutants and their impacts. The analyses in this work were focused on MAM (March, April and May). The simulations indicate an extensive area of elevated pollutant concentrations spanning from the Arabian Sea to the Northern Pacific and to the Northern Atlantic. MAM mean contributions from the tripled Asian emissions over the U.S. are found to be: 612 ppbv for CO, 1.02.5 ppbv for O3, and 0.61.6 μg m−3 for PM2.5 on a daily basis.

Zhao, C., Y. Wang, Q. Yang, R. Fu, D. Cunnold, and Y. Choi (2010), Impact of East Asian summer monsoon on the air quality over China: View from space, Journal of Geophysical Research: Atmospheres, 115(D9), doi:10.1029/2009JD012745. [online] Available from: .
Tropospheric O3 columns retrieved from Ozone Monitoring Instrument and Microwave Limb Sounder measurements, CO columns retrieved from Measurements of Pollution in the Troposphere, and tropospheric O3 and CO concentrations retrieved from the Tropospheric Emission Spectrometer from May to August in 2006 are analyzed using the Regional Chemical and Transport Model to investigate the impact of the East Asian summer monsoon on the air quality over China. The observed and simulated migrations of O3 and CO are in good agreement, demonstrating that the summer monsoon significantly affects the air quality over southeastern China, and this influence extends to central East China from June to July. Enhancements of CO and O3 over southeastern China disappear after the onset of the summer monsoon and reemerge in August after the monsoon wanes. The premonsoon high O3 concentrations over southern China are due to photochemical production from pollutant emissions and the O3 transport from the stratosphere. In the summer monsoon season, the O3 concentrations are relatively low over monsoon-affected regions because of the transport of marine air masses and weak photochemical activity. We find that the monsoon system strongly modulates the pollution problem over a large portion of East China in summer, depending on its strength and tempo-spatial extension. Model results also suggest that transport from the stratosphere and long-range transport from East China and South/central Asia all make significant contributions to O3 enhancements over West China. Satellite observations provide valuable information for investigating the monsoon impact on air quality, particularly for the regions with limited in situ measurements.


Badarinath, K. V. S., S. K. Kharol, A. R. Sharma, and V. Krishna Prasad (2009), Analysis of aerosol and carbon monoxide characteristics over Arabian Sea during crop residue burning period in the Indo-Gangetic Plains using multi-satellite remote sensing datasets, Journal of Atmospheric and Solar-Terrestrial Physics, 71(12), 12671276, doi:10.1016/j.jastp.2009.04.004.
In this study, we have used multi-satellite data to retrieve aerosol loadings and carbon monoxide (CO) pollution over the Arabian Sea, caused due to anthropogenic activities over the Indo-Gangetic Plains (IGP) in India. Relatively high aerosol and CO loadings during 914 November 2007 over Arabian Sea were attributed to crop residues burning in the IGP and fireworks during Diwali festival. Aerosol index (AI) obtained from ozone monitoring instrument (OMI) and CO from measurements of pollution in the troposphere instrument (MOPITT). CO showed higher values over the Arabian Sea suggesting long-range transport of anthropogenic aerosols and trace gases from the continental to Arabian Sea region.

Bowman, K. W., D. B. A. Jones, J. A. Logan, H. Worden, F. Boersma, R. Chang, S. Kulawik, G. Osterman, P. Hamer, and J. Worden (2009), The zonal structure of tropical O3 and CO as observed by the Tropospheric Emission Spectrometer in November 2004 Part 2: Impact of surface emissions  on O3 and its precursors, Atmos. Chem. Phys., 9(11), 35633582, doi:10.5194/acp-9-3563-2009.
The impact of surface emissions on the zonal structure of tropical tropospheric ozone and carbon monoxide is investigated for November 2004 using satellite observations, in-situ measurements, and chemical transport models in conjunction with inverse-estimated surface emissions.Vertical ozone profiles from the Tropospheric Emission Spectrometer (TES) and ozone sonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network show elevated concentrations of ozone over Indonesia and Australia (60-70 ppb) in the lower troposphere against the backdrop of the well-known zonal ”wave-one” pattern with ozone concentrations of (70-80 ppb) centered over the Atlantic . Observational evidence from TES CO vertical profiles and Ozone Monitoring Instrument (OMI) NO2 columns point to regional surface emissions as an important contributor to the elevated ozone over Indonesia. This contribution is investigated with the GEOS-Chem chemistry and transport model using surface emission estimates derived from an optimal inverse model, which was constrained by TES and Measurements Of Pollution In The Troposphere (MOPITT) CO profiles (Jones et al., 2009). These a posteriori estimates, which were over a factor of 2 greater than climatological emissions, reduced differences between GEOS-Chem and TES ozone observations by 30-40% over Indonesia. The response of the free tropospheric chemical state to the changes in these emissions is investigated for ozone, CO, NOx, and PAN. Model simulations indicate that ozone over Indonesian/Australian is sensitive to regional changes in surface emissions of NOx but relatively insensitive to lightning NOx. Over sub-equatorial Africa and South America, free tropospheric NOx was reduced in response to increased surface emissions potentially muting ozone production.

Chen, D., Y. Wang, M. B. McElroy, K. He, R. M. Yantosca, and P. Le Sager (2009a), Regional CO pollution and export in China simulated by the high-resolution nested-grid GEOS-Chem model, Atmos. Chem. Phys., 9(11), 38253839, doi:10.5194/acp-9-3825-2009.
An updated version of the nested-grid GEOS-Chem model is developed allowing for higher horizontal (0.5 degree 0.667 degree ) resolution as compared to global models. CO transport over a heavily polluted region, the Beijing-Tianjin-Hebei (BTH) city cluster in China, and the pattern of outflow from East China in summertime are investigated. Comparison of the nested-grid with global models indicates that the fine-resolution nested-grid model is capable of resolving individual cities with high associated emission intensities. The nested-grid model indicates the presence of a high CO column density over the Sichuan Basin in summer, attributable to the low-level stationary vortex associated with the Basin’s topographical features. The nested-grid model provides good agreement also with measurements from a suburban monitoring site in Beijing during summer 2005. Tagged CO simulation results suggest that regional emissions make significant contributions to elevated CO levels over Beijing on polluted days and that the southeastward moving cyclones bringing northwest winds to Beijing are the key meteorological mechanisms responsible for dispersion of pollution over Beijing in summer. Overall CO fluxes to the NW Pacific from Asia are found to decrease by a factor of 3-4 from spring to summer. Much of the seasonal change is driven by decreasing fluxes from India and Southeast Asia in summer, while fluxes from East China are only 30% lower in summer than in spring. Compared to spring, summertime outflow from Chinese source regions is strongest at higher latitudes (north of 35 degree N). The deeper convection in summer transporting CO to higher altitudes where export is more efficient is largely responsible for enhanced export in summer.

Chen, Y., Q. Li, J. T. Randerson, E. A. Lyons, R. A. Kahn, D. L. Nelson, and D. J. Diner (2009b), The sensitivity of CO and aerosol transport to the temporal and vertical distribution of North American boreal fire emissions, Atmos. Chem. Phys., 9(17), 65596580, doi:10.5194/acp-9-6559-2009.
Forest fires in Alaska and western Canada represent important sources of aerosols and trace gases in North America. Among the largest uncertainties when modeling forest fire effects are the timing and injection height of biomass burning emissions. Here we simulate CO and aerosols over North America during the 2004 fire season, using the GEOS-Chem chemical transport model. We apply different temporal distributions and injection height profiles to the biomass burning emissions, and compare model results with satellite-, aircraft-, and ground-based measurements. We find that averaged over the fire season, the use of finer temporal resolved biomass burning emissions usually decreases CO and aerosol concentrations near the fire source region, and often enhances long-range transport. Among the individual temporal constraints, switching from monthly to 8-day time intervals for emissions has the largest effect on CO and aerosol distributions, and shows better agreement with measured day-to-day variability. Injection height substantially modifies the surface concentrations and vertical profiles of pollutants near the source region. Compared with CO, the simulation of black carbon aerosol is more sensitive to the temporal and injection height distribution of emissions. The use of MISR-derived injection heights improves agreement with surface aerosol measurements near the fire source. Our results indicate that the discrepancies between model simulations and MOPITT CO measurements near the Hudson Bay can not be attributed solely to the representation of injection height within the model. Frequent occurrence of strong convection in North America during summer tends to limit the influence of injection height parameterizations of fire emissions in Alaska and western Canada with respect to CO and aerosol distributions over eastern North America.

Chevallier, F., A. Fortems, P. Bousquet, I. Pison, S. Szopa, M. Devaux, and D. A. Hauglustaine (2009), African CO emissions between years 2000 and 2006 as estimated from MOPITT observations, Biogeosciences, 6(1), 103111, doi:10.5194/bg-6-103-2009.
The space-time variations of the carbon budget at the Earth’s surface are highly variable and quantifying them represents a major scientific challenge. One strategy consists in inferring the carbon surface fluxes from the atmospheric concentrations. An inversion scheme for the hydrocarbon oxidation chain, that includes CO and CH(4), is presented here with a focus on the African continent. It is based on a variational principle. The multi-tracer system has been built as an extension of a system initially developed for CO(2) and includes a new simplified non-linear chemistry module. Individual in situ measurements of methyl-chloroform and individual retrievals of CO concentrations from the Measurements Of Pollution In The Troposphere (MOPITT) space-born instrument have been processed by the new system for the period 2000-2006 to infer the time series of CO emissions at the resolution of 2.5 degrees x 3.75 degrees (latitude, longitude). It is shown that the analysed concentrations improve the fit to five independent surface measurement stations located in or near Africa by up to 28% compared to standard inventories, which confirms that significant information about CO emissions can be obtained from MOPITT data. In practice, the inversion reduces the amplitude and the interannual variability of the seasonal cycle in the northern part of Africa, with a longer burning season. In the southern part, the inversion mainly shifts the emission peak by one month later in the season, consistent with previously-published inversion results.

Deeter, M. N., D. P. Edwards, J. C. Gille, and J. R. Drummond (2009), CO retrievals based on MOPITT near-infrared observations, Journal of Geophysical Research (Atmospheres), 114(d13), 4303, doi:10.1029/2008JD010872.
We report the first retrieval results of tropospheric carbon monoxide (CO) exclusively using near-infrared (NIR) radiances in the 2.3 μm CO overtone band observed by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. For daytime overpasses over land, such observations complement MOPITT’s thermal infrared (TIR) observations in the 4.7 μm CO fundamental band, especially for constraining the CO total column. Retrievals are performed in an optimal estimation framework in which effective radiance errors due to geophysical sources are estimated empirically. The new NIR-based retrievals are evaluated through comparisons with both the standard TIR-based MOPITT CO product and CO profile measurements.

Ding, A., T. Wang, L. Xue, J. Gao, A. Stohl, H. Lei, D. Jin, Y. Ren, X. Wang, X. Wei, Y. Qi, J. Liu, and X. Zhang (2009), Transport of north China air pollution by midlatitude cyclones: Case study of aircraft measurements in summer 2007, Journal of Geophysical Research: Atmospheres, 114(D8), n/a-n/a, doi:10.1029/2008JD011023.
Warm conveyor belts (WCBs) and frontal activity play important roles in the long-range transport of air pollutants by lifting them from the planetary boundary layer (PBL) into the free troposphere (FT) in midlatitudes. In summer 2007, an aircraft study was carried out in northeast (NE) China in order to understand the role of midlatitude cyclones in air pollution transport in north and east China in warm seasons. During a flight on 27 June, high concentrations of ozone and related trace gases were observed, with maximum concentrations (O3 ∼ 140 ppbv, SO2 ∼ 14.6 ppbv, CO ∼ 1185 ppbv) recorded at an altitude of 2.6 km. In this paper we present a detailed analysis of this flight. The mesoscale meteorological model Weather Research and Forecasting (WRF) and a Lagrangian dispersion model called FLEXPART were used to aid the diagnostic analysis of the atmospheric dynamic structure and the understanding of the transport characteristics of regional and local air pollution. The flight took place in a region adjacent to a warm front associated with a weak cyclone in north China. The aircraft sampled both the WCB and warm air frontal zone of the cyclone. The simulations show that the observed high air pollution in the FT mostly originated from the North China Plain, especially the megacities Beijing and Tianjin. Their plumes were vented by a stagnant front, probably through, in part, topographic lifting by the mountains in the north, and then were quickly transported in the FT to the study region. Trajectory analysis and satellite data suggest that the observed air masses were further lifted by the WCB into the middle and upper troposphere and were exported from Asia toward North America and the Arctic.

Edwards, D. P., A. F. Arellano, and M. N. Deeter (2009), A satellite observation system simulation experiment for carbon monoxide  in the lowermost troposphere, J. Geophys. Res.-Atmos., 114, doi:10.1029/2008JD011375.
We demonstrate the feasibility of using observing system simulation experiment (OSSE) studies to help define quantitative trace gas measurement requirements for satellite missions and to evaluate the expected performance of proposed observing strategies. The 2007 U. S. National Research Council Decadal Survey calls for a geostationary (GEO) satellite mission for atmospheric composition and air quality applications (Geostationary Coastal and Air Pollution Events Mission (GEO-CAPE)). The requirement includes a multispectral (near-infrared and thermal infrared) measurement of carbon monoxide (CO) at high spatiotemporal resolution with information on lowermost troposphere concentration. We present an OSSE to assess the improvement in surface CO characterization that would result from the addition of a GEO-CAPE CO measurement to current low Earth orbit (LEO) thermal infrared-only measurements. We construct instrument simulators for these two measurement scenarios and study the case of July 2004 when wildfires in Alaska and Canada led to significant CO pollution over the contiguous United States. Compared to a control experiment, an ensemble-based data assimilation of simulated satellite observations in a global model leads to improvements in both the surface CO distributions and the time evolution of CO profiles at locations affected by wildfire plumes and by urban emissions. In all cases, an experiment with the GEO-CAPE CO measurement scenario (overall model skill of 0.84) performed considerably better than the experiment with the current LEO/thermal infrared measurement (skill of 0.58) and the control (skill of 0.07). This demonstrates the advantages of increased sampling from GEO and enhanced measurement sensitivity to the lowermost troposphere with a multispectral retrieval.

Emmons, L. K., D. P. Edwards, M. N. Deeter, J. C. Gille, T. Campos, P. Nédélec, P. Novelli, and G. Sachse (2009), Measurements of Pollution In The Troposphere (MOPITT) validation through 2006, Atmos. Chem. Phys., 9(5), 17951803, doi:10.5194/acp-9-1795-2009.
Comparisons of aircraft measurements of carbon monoxide (CO) to the retrievals of CO using observations from the Measurements of Pollution in The Troposphere (MOPITT) instrument onboard the Terra satellite are presented. Observations made as part of the NASA INTEX-B and NSF MIRAGE field campaigns during March-May 2006 are used to validate the MOPITT CO retrievals, along with routine samples from 2001 through 2006 from NOAA and the MOZAIC measurements from commercial aircraft. A significant positive bias, around 20% for total column CO, in MOPITT CO was found in the comparison to in situ measurements during 2006. Comparisons to the long-term records of measurements from NOAA and MOZAIC revealed an increasing bias in the V3 MOPITT CO retrievals over time. The impact of an instrumental drift is illustrated through retrieval simulations.

Fortems-Cheiney, A., F. Chevallier, I. Pison, P. Bousquet, C. Carouge, C. Clerbaux, P.-F. Coheur, M. George, D. Hurtmans, and S. Szopa (2009), On the capability of IASI measurements to inform about CO surface emissions, Atmos. Chem. Phys., 9(22), 87358743, doi:10.5194/acp-9-8735-2009.
Between July and November 2008, simultaneous observations were conducted by several orbiting instruments that monitor carbon monoxide in the atmosphere, among them the Infrared Atmospheric Sounding Instrument (IASI) and Measurements Of Pollution In The Troposphere (MOPITT). In this paper, the concentration retrievals at about 700 hPa from these two instruments are successively used in a variational Bayesian system to infer the global distribution of CO emissions. Starting from a global emission budget of 479 Tg for the considered period, the posterior estimate of CO emissions using IASI retrievals gives a total of 643 Tg, which is in close agreement with the budget calculated with version 3 of the MOPITT data (649 Tg). The regional totals are also broadly consistent between the two inversions. Even though our theoretical error budget indicates that IASI constrains the emissions slightly less than MOPITT, because of lesser sensitivity in the lower troposphere, these first results indicate that IASI may play a major role in the quantification of the emissions of CO.

Freitas, S. R., K. M. Longo, M. A. F. Silva Dias, R. Chatfield, P. Silva Dias, P. Artaxo, M. O. Andreae, G. Grell, L. F. Rodrigues, A. Fazenda, and J. Panetta (2009), The Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) Part 1: Model description and evaluation, Atmos. Chem. Phys., 9(8), 28432861, doi:10.5194/acp-9-2843-2009.
We introduce the Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS). CATT-BRAMS is an on-line transport model fully consistent with the simulated atmospheric dynamics. Emission sources from biomass burning and urban-industrial-vehicular activities for trace gases and from biomass burning aerosol particles are obtained from several published datasets and remote sensing information. The tracer and aerosol mass concentration prognostics include the effects of sub-grid scale turbulence in the planetary boundary layer, convective transport by shallow and deep moist convection, wet and dry deposition, and plume rise associated with vegetation fires in addition to the grid scale transport. The radiation parameterization takes into account the interaction between the simulated biomass burning aerosol particles and short and long wave radiation. The atmospheric model BRAMS is based on the Regional Atmospheric Modeling System (RAMS), with several improvements associated with cumulus convection representation, soil moisture initialization and surface scheme tuned for the tropics, among others. In this paper the CATT-BRAMS model is used to simulate carbon monoxide and particulate material (PM2.5) surface fluxes and atmospheric transport during the 2002 LBA field campaigns, conducted during the transition from the dry to wet season in the southwest Amazon Basin. Model evaluation is addressed with comparisons between model results and near surface, radiosondes and airborne measurements performed during the field campaign, as well as remote sensing derived products. We show the matching of emissions strengths to observed carbon monoxide in the LBA campaign. A relatively good comparison to the MOPITT data, in spite of the fact that MOPITT a priori assumptions imply several difficulties, is also obtained.

George, M., C. Clerbaux, D. Hurtmans, S. Turquety, P.-F. Coheur, M. Pommier, J. Hadji-Lazaro, D. P. Edwards, H. Worden, M. Luo, C. Rinsland, and W. McMillan (2009), Carbon monoxide distributions from the IASI/METOP mission: evaluation with other space-borne remote sensors, Atmos. Chem. Phys., 9(21), 83178330, doi:10.5194/acp-9-8317-2009.
The Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellite measures carbon monoxide (CO) on a global scale, twice a day. CO total columns and vertical profiles are retrieved in near real time from the nadir radiance spectra measured by the instrument in the thermal infrared (TIR) spectral range. This paper describes the measurement vertical sensitivity and provides a first assessment of the capabilities of IASI to measure CO distributions. On the global scale, 0.8 to 2.4 independent pieces of information are available for the retrieval. At mid latitudes, the information ranges between 1.5 and 2, which enables the lower and upper troposphere to be distinguished, especially when thermal contrast is significant. Global distributions of column CO are evaluated with correlative observations available from other nadir looking TIR missions currently in operation: the Measurements of Pollution in the Troposphere (MOPITT) onboard TERRA, the Atmospheric Infrared Sounder (AIRS) onboard AQUA and the Tropospheric Emission Spectrometer (TES) onboard AURA. The IASI CO columns are compared with MOPITT, AIRS and TES CO columns, adjusted with the a priori, for three different months: August 2008, November 2008 and February 2009. On average, total column discrepancies of about 7% are found between IASI and the three other sounders in the Northern Hemisphere and in the equatorial region. However when strong CO concentrations are present, such as during fire events, these discrepancies can climb as high as 17%. Instrument specifications of IASI versus other missions are also discussed.

Glatthor, N., T. von Clarmann, G. P. Stiller, B. Funke, M. E. Koukouli, H. Fischer, U. Grabowski, M. Höpfner, S. Kellmann, and A. Linden (2009), Large-scale upper tropospheric pollution observed by MIPAS HCN and C2H6 global distributions, Atmos. Chem. Phys., 9(24), 96199634, doi:10.5194/acp-9-9619-2009.
We present global upper tropospheric HCN and C2H6 amounts derived from MIPAS/ENVISAT limb emission spectra. HCN and C2H6 are retrieved in the spectral regions 715.5-782.7 cm-1 and 811.5-835.7 cm-1, respectively. The datasets consist of 54 days between September 2003 and March 2004. This period covers the peak and decline of the southern hemispheric biomass burning period and some months thereafter. HCN is a nearly unambiguous tracer of biomass burning with an assumed tropospheric lifetime of several months. Indeed, the most significant feature in the MIPAS HCN dataset is an upper tropospheric plume of enhanced values caused by southern hemispheric biomass burning, which in September and October 2003 extended from tropical South America over Africa, Australia to the Southern Pacific. The spatial extent of this plume agrees well with the MOPITT CO distribution of September 2003. Further there is good agreement with the shapes and mixing ratios of the southern hemispheric HCN and C2H6 fields measured by the ACE experiment between September and November 2005. The MIPAS HCN plume extended from the lowermost observation height of 8 km up to about 16 km altitude, with maximum values of 500-600 pptv in October 2003. It was still clearly visible in December 2003, but had strongly decreased by March 2004, confirming the assumed tropospheric lifetime. The main sources of C2H6 are production and transmission of fossil fuels, followed by biofuel use and biomass burning. The C2H6 distribution also clearly reflected the southern hemispheric biomass burning plume and its seasonal variation, with maximum amounts of 600-700 pptv. Generally there was good spatial overlap between the southern hemispheric distributions of both pollution tracers, except for the region between Peru and the mid-Pacific. Here C2H6was considerably enhanced, whereas the HCN amounts were low. Backward trajectory calculations suggested that industrial pollution was responsible for the elevated C2H6 concentration in these particular air masses. Except for the Asian monsoon anticyclone in September 2003, there were only comparably small regions of enhanced HCN in the Northern Hemisphere. However, C2H6 showed an equally strong northern hemispheric signal between the equator and low midlatitudes, persisting over the whole observation period. Backward trajectory calculations for air masses from this region also point to industrial sources of this pollution. Generally, C2H6/HCN ratios between 1 and 1.5 indicate biomass burning and ratios larger than 1.5 industrial pollution. However, in March 2004 ratios of up to 2 were also found in some regions of the former southern biomass burning plume.

Gloudemans, A. M. S., A. T. J. de Laat, H. Schrijver, I. Aben, J. F. Meirink, and G. R. van der Werf (2009), SCIAMACHY CO over land and oceans: 20032007 interannual variability, Atmos. Chem. Phys., 9(11), 37993813, doi:10.5194/acp-9-3799-2009.
We present a new method to obtain accurate SCIAMACHY CO columns over clouded ocean scenes. Based on an improved version of the Iterative Maximum Likelihood Method (IMLM) retrieval algorithm, we now have retrieved five years of data over both land and clouded ocean scenes between 2003 and 2007. The ocean-cloud method uses the CH4 columns retrieved simultaneously with the CO columns to determine the cloud top height. The CH4 cloud top height is in good agreement with the FRESCO+ cloud top height determined from UV-VIS oxygen-A band measurements, providing confidence that the CH4 cloud top height is a good diagnostic of the cloud top height over (partially) clouded ocean scenes. The CO measurements over clouded ocean scenes have been compared with collocated modeled CO columns over the same clouds and agree well. Using clouded ocean scenes quadruples the number of useful CO measurements compared to land-only measurements.

Ho, S.-P., D. P. Edwards, J. C. Gille, M. Luo, G. B. Osterman, S. S. Kulawik, and H. Worden (2009), A global comparison of carbon monoxide profiles and column amounts from Tropospheric Emission Spectrometer (TES) and Measurements of Pollution in the Troposphere (MOPITT), Journal of Geophysical Research: Atmospheres, 114(D21), n/a-n/a, doi:10.1029/2009JD012242.
In this study, we compare carbon monoxide (CO) products from the Measurements of Pollution in the Troposphere (MOPITT) and Tropospheric Emission Spectrometer (TES) and investigate the possible causes of the differences between retrievals for these two data sets. Direct comparisons of CO retrievals for July 2006 show that TES CO concentrations are consistently biased lower than those of MOPITT by 25 ppbv near the surface and by 20 ppbv at 150 hPa, primarily due to different a priori profiles and covariance matrices used in the TES and MOPITT CO retrievals. To reduce the effects of different a priori constraints, we apply TES a priori profiles and covariance matrices to a modified MOPITT retrieval algorithm. The mean TES-MOPITT CO difference decreases from −25 to −10 ppbv near the surface. To further account for retrieval smoothing errors due to different TES and MOPITT averaging kernels, TES averaging kernels are used to smooth MOPITT CO profiles to derive TES-equivalent CO profiles. Compared to these, TES CO profiles are biased 1 ppbv lower near the surface and 49 ppbv lower in the troposphere, and the mean absolute TES and TES-equivalent CO column difference is less than 6.5%. The mean TES and MOPITT CO differences due to smoothing errors are close to zero, and the remaining bias is primarily due to the combined effects of radiance biases, forward model errors, and the spatial and temporal mismatches of TES and MOPITT pixels.

Isaksen, I. S. A., C. Granier, G. Myhre, T. K. Berntsen, S. B. Dalsøren, M. Gauss, Z. Klimont, R. Benestad, P. Bousquet, W. Collins, T. Cox, V. Eyring, D. Fowler, S. Fuzzi, P. Jöckel, P. Laj, U. Lohmann, M. Maione, P. Monks, A. S. H. Prevot, F. Raes, A. Richter, B. Rognerud, M. Schulz, D. Shindell, D. S. Stevenson, T. Storelvmo, W.-C. Wang, M. van Weele, M. Wild, and D. Wuebbles (2009), Atmospheric composition change: ClimateChemistry interactions, Atmospheric Environment, 43(33), 51385192, doi:10.1016/j.atmosenv.2009.08.003.
Chemically active climate compounds are either primary compounds like methane (CH4), removed by oxidation in the atmosphere, or secondary compounds like ozone (O3), sulfate and organic aerosols, both formed and removed in the atmosphere. Man-induced climatechemistry interaction is a two-way process: Emissions of pollutants change the atmospheric composition contributing to climate change through the aforementioned climate components, and climate change, through changes in temperature, dynamics, the hydrological cycle, atmospheric stability, and biosphere-atmosphere interactions, affects the atmospheric composition and oxidation processes in the troposphere. Here we present progress in our understanding of processes of importance for climatechemistry interactions, and their contributions to changes in atmospheric composition and climate forcing. A key factor is the oxidation potential involving compounds like O3 and the hydroxyl radical (OH). Reported studies represent both current and future changes. Reported results include new estimates of radiative forcing based on extensive model studies of chemically active climate compounds like O3, and of particles inducing both direct and indirect effects. Through EU projects like ACCENT, QUANTIFY, and the AeroCom project, extensive studies on regional and sector-wise differences in the impact on atmospheric distribution are performed. Studies have shown that land-based emissions have a different effect on climate than ship and aircraft emissions, and different measures are needed to reduce the climate impact. Several areas where climate change can affect the tropospheric oxidation process and the chemical composition are identified. This can take place through enhanced stratospherictropospheric exchange of ozone, more frequent periods with stable conditions favoring pollution build up over industrial areas, enhanced temperature induced biogenic emissions, methane releases from permafrost thawing, and enhanced concentration through reduced biospheric uptake. During the last 510 years, new observational data have been made available and used for model validation and the study of atmospheric processes. Although there are significant uncertainties in the modeling of composition changes, access to new observational data has improved modeling capability. Emission scenarios for the coming decades have a large uncertainty range, in particular with respect to regional trends, leading to a significant uncertainty range in estimated regional composition changes and climate impact.

Jones, D. B. A., K. W. Bowman, J. A. Logan, C. L. Heald, J. Liu, M. Luo, J. Worden, and J. Drummond (2009), The zonal structure of tropical O3 and CO as observed by the Tropospheric Emission Spectrometer in November 2004 Part 1: Inverse modeling of CO emissions, Atmos. Chem. Phys., 9(11), 35473562, doi:10.5194/acp-9-3547-2009.
We conduct an inverse modeling analysis of measurements of atmospheric CO from the TES and MOPITT satellite instruments using the GEOS-Chem global chemical transport model to quantify emissions of CO in the tropics in November 2004. We also assess the consistency of the information provided by TES and MOPITT on surface emissions of CO. We focus on the tropics in November 2004, during the biomass burning season., because TES observations of CO and O-3 and MOPITT observations of CO reveal significantly greater abundances of these gases than simulated by the GEOS-Chem model during that period. We find that both datasets suggest substantially greater emissions of CO from sub-equatorial Africa and the Indonesian/Australian re-ion than in the climatological emissions in the model. The a posteriori emissions from sub-equatorial Africa based on TES and MOPITT data were 173 Tg CO/yr and 184 Tg CO/yr, respectively, compared to the a priori of 95 Tg CO/yr. In the Indonesian/Australian region, the a posteriori emissions inferred from TES and MOPITT data were 155 Tg CO/yr and 185 Tg CO/yr, respectively, whereas the a priori was 69 Tg CO/yr. The differences between the a posteriori emission estimates obtained from the two datasets are generally less than 20%. The a posteriori emissions significantly improve the simulated distribution of CO, however, large regional residuals remain, and are likely due to systematic errors in the analysis. Reducing these residuals and improving the accuracy of top-down emission estimates will require better characterization of systematic errors in the observations and the model (chemistry and transport).

Khlystova, I., M. Buchwitz, J. P. Burrows, H. Bovensmann, and D. Fowler (2009), Carbon monoxide spatial gradients over source regions as observed by  SCIAMACHY: A case study for the United Kingdom, Adv. Space Res., 43(6), 923929, doi:10.1016/j.asr.2008.10.012.
Carbon monoxide (CO) is an important air pollutant whose emissions and atmospheric concentrations need to be monitored. The measurements of the SCIAMACHY instrument oil ENVISAT are sensitive to CO concentration changes at all atmospheric altitude levels including the boundary layer. The SCIAMACHY CO measurements therefore contain information on CO emissions. Until now no studies have been published where the SCIAMACHY CO measurements have been used to quantify CO emissions by applying, for example, inverse modelling approaches. Here we report about a step in this direction. We have analysed three years of CO columns to investigate if spatial gradients resulting from United Kingdom (UK) CO emissions can be observed from space. The UK is an interesting target area because the UK is a relatively well isolated CO source region. Oil the other hand, the UK is not the easiest target as its emissions are only moderate and because the surrounding water has low reflectivity in the 2.3 mu m spectral region used for CO retrieval. We determined horizontal CO gradients from seasonally and yearly averaged CO during 2003-2005 over the UK taking into account daily wind fields. We show that the measured CO longitudinal (downwind) gradients have the expected order of magnitude. The estimated 2 sigma error of the gradients depends on time period and applied filtering criteria (e.g., land only, cloud free) and is typically 10-20% of the total column. The gradients are barely statistically significant within the 2 sigma error margin. This is mainly because of the relatively high noise of the SCIAMACHY CO measurements in combination with a quite low number of measurements (similar to 100) mainly due to cloud cover. (C) 2008 COSPAR. Published by Elsevier Ltd. All rights reserved.

Kopacz, M., D. J. Jacob, D. K. Henze, C. L. Heald, D. G. Streets, and Q. Zhang (2009), Comparison of adjoint and analytical Bayesian inversion methods for constraining Asian sources of carbon monoxide using satellite (MOPITT) measurements of CO columns, Journal of Geophysical Research (Atmospheres), 114(d13), 4305, doi:10.1029/2007JD009264.
We apply the adjoint of an atmospheric chemical transport model (GEOS-Chem CTM) to constrain Asian sources of carbon monoxide (CO) with 2° × 2.5° spatial resolution using Measurement of Pollution in the Troposphere (MOPITT) satellite observations of CO columns in February-April 2001. Results are compared to the more common analytical method for solving the same Bayesian inverse problem and applied to the same data set. The analytical method is more exact but because of computational limitations it can only constrain emissions over coarse regions. We find that the correction factors to the a priori CO emission inventory from the adjoint inversion are generally consistent with those of the analytical inversion when averaged over the large regions of the latter. The adjoint solution reveals fine-scale variability (cities, political boundaries) that the analytical inversion cannot resolve, for example, in the Indian subcontinent or between Korea and Japan, and some of that variability is of opposite sign which points to large aggregation errors in the analytical solution. Upward correction factors to Chinese emissions from the prior inventory are largest in central and eastern China, consistent with a recent bottom-up revision of that inventory, although the revised inventory also sees the need for upward corrections in southern China where the adjoint and analytical inversions call for downward correction. Correction factors for biomass burning emissions derived from the adjoint and analytical inversions are consistent with a recent bottom-up inventory on the basis of MODIS satellite fire data.

Pison, I., P. Bousquet, F. Chevallier, S. Szopa, and D. Hauglustaine (2009), Multi-species inversion of CH4, CO and H2 emissions from surface measurements, Atmos. Chem. Phys., 9(14), 52815297, doi:10.5194/acp-9-5281-2009.
In order to study the spatial and temporal variations of the emissions of greenhouse gases and of their precursors, we developed a data assimilation system and applied it to infer emissions of CH4, CO and H-2 for one year. It is based on an atmospheric chemical transport model and on a simplified scheme for the oxidation chain of hydrocarbons, including methane, formaldehyde, carbon monoxide and molecular hydrogen together with methyl chloroform. The methodology is exposed and a first attempt at evaluating the inverted fluxes is made. Inversions of the emission fluxes of CO, CH4 and H-2 and concentrations of HCHO and OH were performed for the year 2004, using surface concentration measurements of CO, CH4, H-2 and CH3CCl3 as constraints. Independent data from ship and aircraft measurements and satellite retrievals are used to evaluate the results. The total emitted mass of CO is 30% higher after the inversion, due to increased fluxes by up to 35% in the Northern Hemisphere. The spatial distribution of emissions of CH4 is modified by a decrease of fluxes in boreal areas up to 60%. The comparison between mono- and multi-species inversions shows that the results are close at a global scale but may significantly differ at a regional scale because of the interactions between the various tracers during the inversion.

Reidmiller, D. R., D. A. Jaffe, D. Chand, S. Strode, P. Swartzendruber, G. M. Wolfe, and J. A. Thornton (2009), Interannual variability of long-range transport as seen at the Mt. Bachelor observatory, Atmos. Chem. Phys., 9(2), 557572, doi:10.5194/acp-9-557-2009.
Interannual variations in background tropospheric trace gases (such as carbon monoxide, CO) are largely driven by variations in emissions (especially wildfires) and transport pathways. Understanding this variability is essential to quantify the intercontinental contribution to US air quality. We investigate the interannual variability of long-range transport of Asian pollutants to the Northeast Pacific via measurements from the Mt. Bachelor Observatory (MBO: 43.98° N, 121.69° W; 2.7 km a.s.l.) and GEOS-Chem chemical transport model simulations in spring 2005 vs. the INTEX-B campaign during spring 2006. Measurements of CO at MBO were significantly enhanced during spring 2005 relative to the same time in 2006 (the INTEX-B study period); a decline in monthly mean CO of 41 ppbv was observed between April 2005 and April 2006. A backtrajectory-based meteorological index shows that long-range transport of CO from the heavily industrialized region of East Asia was significantly greater in early spring 2005 than in 2006. In addition, spring 2005 was an anomalously strong biomass burning season in Southeast Asia. Data presented by Yurganov et al. (2008) using MOPITT satellite retrievals from this area reveal an average CO burden anomaly (referenced to March 2000-February 2002 mean values) between October 2004 through April 2005 of 2.6 Tg CO vs. 0.6 Tg CO for the same period a year later. The Naval Research Laboratory’s global aerosol transport model, as well as winds from NCEP reanalysis, show that emissions from these fires were efficiently transported to MBO throughout April 2005. Asian dust transport, however, was substantially greater in 2006 than 2005, particularly in May. Monthly mean aerosol light scattering coefficient at 532 nm (σsp) at MBO more than doubled from 2.7 Mm-1 in May 2005 to 6.2 Mm-1 in May 2006. We also evaluate CO interannual variability throughout the western US via Earth System Research Laboratory ground site data and throughout the Northern Hemisphere via MOPITT and TES satellite observations. Both in the Northeast Pacific and on larger scales, we reveal a significant decrease (from 2-21%) in springtime maximum CO between 2005 and 2006, evident in all platforms and the GEOS-Chem model. We attribute this to (a) anomalously strong biomass burning in Southeast Asia during winter 2004 through spring 2005, and (b) the transport pattern in March and April 2006 which limited the inflow of Asian pollution to the lower free troposphere over western North America.

Shukla, B. P. and Ajai (2009), Retrieval of Carbon monoxide profiles over Indian region using MOPITT data, Atmospheric Environment, 43(2223), 34723480, doi:10.1016/j.atmosenv.2009.04.037.
Vertical profiles of carbon monoxide (CO) over the Indian region have scarcely been monitored. Satellite sensor, Measurement Of Pollution In The Troposphere (MOPITT) provides profiles of CO using a global retrieval scheme, which converts measured radiances to CO mixing ratios. In this study we have developed a regional retrieval scheme, valid over the Indian region, which employs Line-By-Line (LBL) calculations over a tropical model atmosphere to generate a Look-Up-Table (LUT) forward model function and uses a regional a priori dataset of CO along with seasonally variable emissivity to invert the MOPITT radiances to CO profiles. This baseline study provides an approach to optimizing retrievals for specific regional applications. A case study was carried out over a forest fire prone region in Northern India from February to April 2005 to validate the retrieval algorithm. The results are in agreement with the fire maps generated from MODerate resolution Imaging Spectro-radiometer (MODIS). The shape of the CO profiles over the region matches quite well with the vertical structure of CO during the INDOEX campaign, especially during the polluted month of April. Inter-comparisons with the MOPITT data product indicate some discrepancies in the lower troposphere, especially during the forest fire season. Future studies with in-situ measurements may be able to diagnose these disparities.

Stremme, W., I. Ortega, and M. Grutter (2009), Using ground-based solar and lunar infrared spectroscopy to study the diurnal trend of carbon monoxide in the Mexico City boundary layer, Atmos. Chem. Phys., 9(20), 80618078, doi:10.5194/acp-9-8061-2009.
Carbon monoxide (CO) is an important pollutant in urban agglomerations. Quantifying the total burden of this pollutant in a megacity is challenging because not only its surface concentration but also its vertical dispersion present different behaviours and high variability. The diurnal trend of columnar CO in the boundary layer of Mexico City has been measured during various days with ground-based infrared absorption spectroscopy. Daytime CO total columns are retrieved from solar spectra and for the first time, nocturnal CO total columns using moonlight have been retrieved within a megacity. The measurements were taken at the Universidad Nacional Autonoma de Mexico (UNAM) campus located in Mexico City (19.33 degree N, 99.18 degree W, 2260 m a.s.l.) from October 2007 until February 2008 with a Fourier-transform infrared spectrometer at 0.5 cm super(− 1) resolution. The atmospheric CO background column was measured from the high altitude site Altzomoni (19.12 degree N, 98.65 degree W, 4010 m a.s.l.) located 60 km southeast of Mexico City. The total CO column within the city presents large variations. Fresh CO emissions at the surface, the transport of cleaner or more polluted air masses within the field-of-view of the instrument and other processes contribute to this variability. The mean background value above the boundary mixing layer was found to be (8.4 plus or minus 0.5)10 super(17) molecules/cm super(2), while inside the city, the late morning mean on weekdays and Sundays was found to be (2.73 plus or minus 0.41)10 super(18) molecules/cm super(2) and (2.04 plus or minus 0.57)10 super(18) molecules/cm super(2), respectively. Continuous CO column retrieval during the day and night (when available), in conjunction with surface CO measurements, allow for a reconstruction of the effective mixing layer height. The limitations from this simplified approach, as well as the potential of using continuous column measurements in order to derive top-down CO emissions from a large urban area, are discussed. Also, further monitoring will provide more insight in daily and weekly emission patterns and a usable database for the quantitative validation of CO from satellite observations in a megacity.

Tangborn, A., I. Stajner, M. Buchwitz, I. Khlystova, S. Pawson, J. Burrows, R. Hudman, and P. Nedelec (2009), Assimilation of SCIAMACHY total column CO observations: Global and regional analysis of data impact, J. Geophys. Res.-Atmos., 114(D7), n/a-n/a, doi:10.1029/2008JD010781.
Carbon monoxide (CO) total column observations from the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) on board Envisat-1 are assimilated into the Global Modeling and Assimilation Office constituent assimilation system for the period 1 April to 20 December 2004. The impact of the assimilation on CO distribution is evaluated using independent surface flask observations from the National Oceanic and Atmospheric Administration (NOAA)/ESRL global cooperative air sampling network and Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) in situ CO profiles. Assimilation of SCIAMACHY data improves agreement of CO assimilation with both of these data sets on both global and regional scales compared to the free-running model. Regional comparisons with MOZAIC profiles made in western Europe, the northeastern United States, and the Arabian Peninsula show improvements at all three locations in the free troposphere and into the boundary layer over Arabia and the northeastern United States. Comparisons with NOAA Earth System Research Laboratory data improve at about two thirds of the surface observation sites. The systematic model errors related to the uncertainty of CO surface sources and the chemistry of CO losses are investigated through experiments with increased surface CO emissions over the Arabian Peninsula and/or globally reduced hydroxyl radical (OH) concentrations. Both model changes decrease mean CO errors at all altitudes in comparison to MOZAIC data over Dubai and Abu Dhabi. In contrast, errors in the assimilated CO are reduced by the increased emissions for pressures ≥800 hPa and by the reduced OH for pressures ≤600 hPa. Our analysis suggests that CO emissions over Dubai in 2004 are more than double those in the 1998 emissions inventory.

Turquety, S., D. Hurtmans, J. Hadji-Lazaro, P.-F. Coheur, C. Clerbaux, D. Josset, and C. Tsamalis (2009), Tracking the emission and transport of pollution from wildfires using the IASI CO retrievals: analysis of the summer 2007 Greek fires, Atmos. Chem. Phys., 9(14), 48974913, doi:10.5194/acp-9-4897-2009.
In this paper, we analyze the performance of the Infrared Atmospheric Sounding Interferometer (IASI), launched in October 2006 on board METOP-A, for the monitoring of carbon monoxide (CO) during extreme fire events, focusing on the record-breaking fires which devastated thousands of square kilometers of forest in Greece during the last week (23-30) of August 2007. After an assessment of the quality of the profiles retrieved using the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, the information provided on fire emissions and subsequent pollution outflow is discussed. Large CO plumes were observed above the Mediterranean Basin and North Africa, with total CO columns exceeding 24x10(18) molecules/cm(2) and absolute volume mixing ratios up to 4 ppmv on the 25 August. Up to 30x10(18) molecules/cm(2) and 22 ppmv in the lower troposphere are retrieved close to the fires above the Peloponnese, but with larger uncertainty. The average root-mean-square (RMS) difference between simulated and observed spectra is close to the estimated radiometric noise level, slightly increasing (by similar to 14%) in the fresh fire plumes. CO profiles are retrieved with a vertical resolution of about 8 km, with similar to 1.7 pieces of independent information on the vertical in the region considered and a maximum sensitivity in the free troposphere (similar to 4-5 km). Using the integrated total amount, the increase in CO burden due to these fires is estimated to 0.321 Tg, similar to 40% of the total annual anthropogenic emissions in Greece. The patterns of these CO enhancements are in good agreement with the aerosol optical depth (AOD) retrieved from the MODIS measurements, highlighting a rapid transport of trace gases and aerosols across the Mediterranean Basin (less than one day). While the coarse vertical resolution will not allow the location of the exact plume height, the large CO enhancements observed in the lower troposphere are consistent with the maximum aerosol backscatter coefficient at similar to 2 km detected by the CALIPSO lidar in space (CALIOP).


Clerbaux, C., D. P. Edwards, M. Deeter, L. Emmons, J.-F. Lamarque, X. X. Tie, S. T. Massie, and J. Gille (2008a), Carbon monoxide pollution from cities and urban areas observed by the Terra/MOPITT mission, Geophysical Research Letters, 35(3), n/a-n/a, doi:10.1029/2007GL032300.
Carbon monoxide (CO) is a key species for tracking pollution plumes. The Measurement Of Pollution in The Troposphere (MOPITT) mission onboard the Terra satellite has already provided 7.5 years of CO atmospheric concentration measurements around the globe. Limited sensitivity to the boundary layer is well known to be a weakness of nadir looking thermal infrared sounders. This paper investigates the possibility of using the MOPITT surface measurements to detect CO emitted by cities and urban centers. By selecting the data and averaging them over long time periods, we demonstrate that the CO pollution arising from the large cities and urban areas can be distinguished from the background transported pollution. The more favorable observations are obtained during daytime and at locations where the thermal contrast (temperature gradient) between the surface and lower atmosphere is significant.

Clerbaux, C., M. George, S. Turquety, K. A. Walker, B. Barret, P. Bernath, C. Boone, T. Borsdorff, J. P. Cammas, V. Catoire, M. Coffey, P.-F. Coheur, M. Deeter, M. De Mazière, J. Drummond, P. Duchatelet, E. Dupuy, R. de Zafra, F. Eddounia, D. P. Edwards, L. Emmons, B. Funke, J. Gille, D. W. T. Griffith, J. Hannigan, F. Hase, M. Höpfner, N. Jones, A. Kagawa, Y. Kasai, I. Kramer, E. Le Flochmoën, N. J. Livesey, M. López-Puertas, M. Luo, E. Mahieu, D. Murtagh, P. Nédélec, A. Pazmino, H. Pumphrey, P. Ricaud, C. P. Rinsland, C. Robert, M. Schneider, C. Senten, G. Stiller, A. Strandberg, K. Strong, R. Sussmann, V. Thouret, J. Urban, and A. Wiacek (2008b), CO measurements from the ACE-FTS satellite instrument: data analysis and validation using ground-based, airborne and spaceborne observations, Atmos. Chem. Phys., 8(9), 25692594, doi:10.5194/acp-8-2569-2008.
The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS). This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006). We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane) observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES) as well as limb-viewing remote sensors (MIPAS, SMR and MLS) were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above). These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (812 km), than 30% in the lower stratosphere (1230 km), and than 25% from 30 to 100 km.

Fishman, J., J. A. Al-Saadi, J. K. Creilson, K. W. Bowman, J. P. Burrows, A. Richter, K. V. Chance, D. P. Edwards, R. V. Martin, G. A. Morris, R. B. Pierce, J. R. Ziemke, T. K. Schaack, and A. M. Thompson (2008), Remote Sensing of Tropospheric Pollution from Space, Bulletin of the American Meteorological Society, 89(6), 805821.
Geostationary satellite observations of chemically reactive trace gases will provide uniqueinsight into the evolution and extent of air pollution with the temporal resolution necessaryto address air quality on a daily basis.

Guan, H., R. B. Chatfield, S. R. Freitas, R. W. Bergstrom, and K. M. Longo (2008), Modeling the effect of plume-rise on the transport of carbon monoxide over Africa with NCAR CAM, Atmos. Chem. Phys., 8(22), 68016812, doi:10.5194/acp-8-6801-2008.
We investigated the effects of fire-induced plume-rise on the simulation of carbon monoxide (CO) over Africa and its export during SAFARI 2000 using the NCAR Community Atmosphere Model (CAM) with a CO tracer and a plume-rise parameterization scheme. The plume-rise parameterization scheme simulates the consequences of strong buoyancy of hot gases emitted from biomass burning, including both dry and cloud-associated (pyro-cumulus) lofting. The current implementation of the plume-rise parameterization scheme into the global model provides an opportunity to examine the effect of plume-rise on long-range transport. The CAM simulation with the plume-rise parameterization scheme seems to show a substantial improvement of the agreements between the modeled and aircraft-measured vertical distribution of CO over Southern Africa biomass-burning area. The plume-rise mechanism plays a crucial role in lofting biomass-burning pollutants to the middle troposphere. In the presence of deep convection we found that the plume-rise mechanism results in a decrease of CO concentration in the upper troposphere. The plume-rise depletes the boundary layer, and thus leaves lower concentrations of CO to be lofted by the deep convection process. The effect of the plume-rise on free troposphere CO concentration is more important for the source area (short-distance transport) than for remote areas (long-distance transport). A budget analysis of CO burden over Southern Africa reveals the plume-rise process to have a similar impact as the chemical production of CO by OH and CH4. In addition, the plume-rise process has an minor impact on the regional export. These results further confirm and extend previous findings in a regional model study. Effective lofting of large concentration of CO by the plume-rise mechanism also has implications for local air quality forecasting in areas affected by other fire-related pollutants.

Henne, S., J. Klausen, W. Junkermann, J. M. Kariuki, J. O. Aseyo, and B. Buchmann (2008), Representativeness and climatology of carbon monoxide and ozone at the global GAW station Mt. Kenya in equatorial Africa, Atmos. Chem. Phys., 8(12), 31193139, doi:10.5194/acp-8-3119-2008.
The tropics strongly influence the global atmospheric chemistry budget. However, continuous in-situ observations of trace gases are rare especially in equatorial Africa. The WMO Global Atmosphere Watch (GAW) programme aimed to close this gap with the installation of the Mt. Kenya (MKN) baseline station. Here, the first continuous measurements of carbon monoxide (CO) and ozone (O3) at this site covering the period June 2002 to June 2006 are presented. The representativeness of the site was investigated by means of statistical data analysis, air mass trajectory clustering, interpretation of biomass burning variability and evaluation of O3-CO relationships. Because of its location in eastern equatorial Africa, the site was rarely directly influenced by biomass burning emissions, making it suitable for background observations. Located at 3678m above sea level the night-time (21:0004:00 UTC) measurements of CO and O3 were in general representative of the free troposphere, while day-time measurements were influenced by atmospheric boundary layer air. Increased night-time concentrations were observed in 25% of all nights and associated with residual layers of increased CO and water vapour in the free troposphere. Six representative flow regimes towards Mt. Kenya were determined: eastern Africa (21% of the time), Arabian Peninsula and Pakistan (16%), northern Africa free tropospheric (6%), northern Indian Ocean and India (17%), south-eastern Africa (18%) and southern India Ocean (21%) flow regimes. The seasonal alternation of these flow regimes was determined by the monsoon circulation and caused a distinct semi-annual cycle of CO with maxima during February (primary) and August (secondary, annually variable) and with minima in April (primary) and November (secondary, annually variable). O3 showed a weaker annual cycle with a minimum in November and a broad sum- Correspondence to: S. Henne ( mer maximum. Inter-annual variations were explained with differences in southern African biomass burning and transport towards MKN. Although biomass burning had little direct influence on the measurements at MKN it introduces inter-annual variability in the background concentrations of the southern hemisphere that subsequently reaches Kenya. The measurements atMKN were representative of air masses with little photochemical activity as indicated by weak O3- CO correlations, underlining the baseline character of the site. Inter-comparison of O3 at MKN with sounding data from Nairobi revealed a positive offset of the sounding data, most likely due to additional photochemical production of O3 in the Nairobi city plume. Future extensions of the measurement programme will provide better understanding of the atmospheric chemistry of this globally important region.

Kaminski, J. W., L. Neary, J. Struzewska, J. C. McConnell, A. Lupu, J. Jarosz, K. Toyota, S. L. Gong, J. Côté, X. Liu, K. Chance, and A. Richter (2008), GEM-AQ, an on-line global multiscale chemical weather modelling system: model description and evaluation of gas phase chemistry processes, Atmos. Chem. Phys., 8(12), 32553281, doi:10.5194/acp-8-3255-2008.
Tropospheric chemistry and air quality processes were implemented on-line in the Global Environmental Multiscale weather prediction model. The integrated model, GEM-AQ, was developed as a platform to investigate chemical weather at scales from global to urban. The current chemical mechanism is comprised of 50 gas-phase species, 116 chemical and 19 photolysis reactions, and is complemented by a sectional aerosol module with 5 aerosols types. All tracers are advected using the semi-Lagrangian scheme native to GEM. The vertical transport includes parameterized subgrid-scale turbulence and large scale deep convection. Dry deposition is included as a flux boundary condition in the vertical diffusion equation. Wet deposition of gas-phase species is treated in a simplified way, and only below-cloud scavenging is considered. The emissions used include yearly-averaged anthropogenic, and monthly-averaged biogenic, ocean, soil, and biomass burning emission fluxes, as well as NOx from lightning. In order to evaluate the ability to simulate seasonal variations and regional distributions of trace gases such as ozone, nitrogen dioxide and carbon monoxide, the model was run for a period of five years (2001-2005) on a global uniform 1.5 degrees x 1.5 degrees horizontal resolution domain and 28 hybrid levels extending up to 10 hPa. Model results were compared with observations from satellites, aircraft measurement campaigns and balloon sondes. We find that GEM-AQ is able to capture the spatial details of the chemical fields in the middle and lower troposphere. The modelled ozone consistently shows good agreement with observations, except over tropical oceans. The comparison of carbon monoxide and nitrogen dioxide with satellite measurements emphasizes the need for more accurate, year-specific emissions fluxes for biomass burning and anthropogenic sources. Other species also compare well with available observations.

Kar, J., D. B. A. Jones, J. R. Drummond, J. L. Attié, J. Liu, J. Zou, F. Nichitiu, M. D. Seymour, D. P. Edwards, M. N. Deeter, J. C. Gille, and A. Richter (2008), Measurement of low-altitude CO over the Indian subcontinent by MOPITT, Journal of Geophysical Research (Atmospheres), 113(d12), 16307, doi:10