ASR Atmospheric Chemistry

ACD Director's Message

The overall ACD objective is to foster improved understanding of chemical processes that affect the Earth's atmosphere. This is accomplished through interdisciplinary studies that probe the complex interactions between oceans, land, ecosystems, and the atmospheric interface they share. ACD serves the broader scientific community through model development, collaborative studies, implementation of aircraft instrumentation, and development of satellite data and instrumentation. ACD maintains a balance between theoretical and experimental research techniques while developing a hierarchy of numerical models to both interpret measurements and extend our understanding to future predictions.

ACD was involved in a large number of field studies during FY96 where many new instruments were successfully applied. Our new airborne OH/H2SO4/MSA instrument was flown for the first time on the Aerosol Characteristics Mission (ACE-I) and later in the Pacific Exploratory Measurements (PEM-Tropics) study with great success. This instrument provided the first aircraft measurements of OH and H2SO4 in the lower and mid troposphere and the first real-time measurements of gas phase MSA. Another new instrument, a two-channel spectroradiometer, was also constructed, calibrated, and flown on the NASA DC-8. Participation in the Vortex Ozone Transport Experiment (VOTE) and Tropical Ozone Transport Experiment (TOTE) investigated transport from the polar vortex to mid-latitude regions and possible heterogeneous processes. Participation in Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) focused on particle formation and aerosol chemical processes in cirrus clouds, wave clouds, and aircraft contrails. An airborne TDL system was developed and first deployed in the North Atlantic Regional Experiment (NARE) where aircraft measurements of HCHO were acquired as part of a suite of photochemically-related species and parameters to study O3 photochemistry and transport processes. A sensitive real-time selected ion chemical ionization mass spectrometric (SICIMS) measurement technique for HNO3 was also recently developed and field tested.

This was also the year for the first Stratosphere-Troposphere: Radiation, Aerosols, and Ozone (STERAO) field intensive where a combination of aircraft, radars, lightning interferometer, and ground based field mills were involved. A four channel chemiluminescence instrument was designed and built to fly on the WB-57F. We also developed a tunable diode laser (TDL) for STERAO to simultaneously measure CO and N2O and help distinguish between transport and chemical and physical transformations. Lower altitude regions were probed with the NOAA P-3 aircraft while the anvil region of the storms were probed with the University of North Dakota Citation jet. A variety of models from NOAA, NCAR's MMM Division, and the University of Maryland were used for storm prediction and analysis.

Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO) efforts included aircraft test flights, infrastructure development, and field measurements at a field site in the Northern Congo. Multiple visits to Africa resulted in the building of a road, setting up a field laboratory, constructing a 65-m tower through the forest canopy, and characterizing the forest landscape. Initial measurements of methane fluxes, VOC emissions from vegetation, and isoprene at the field site indicated that hydrocarbon fluxes from this site are lower than expected.

Modeling studies to develop and use a range of models, from the mesoscale to the global scale, have advanced considerably in the past year, including the implementation of detailed chemistry in the Climate System Model (CSM). In addition, research studies have focused on topics such as the impact of biomass burning on tropospheric ozone, effects of subsonic aircraft, and the increases in surface radiation and changes in tropospheric chemistry due to ozone depletion.

Development of satellite instrumentation and algorithm has also advanced together with concurrent scientific analyses. A range of questions relating to the database from the Upper Atmosphere Research Satellite (UARS) have been addressed, including development of algorithms to infer information about aerosol distributions that are critical for stratospheric chemistry.

Through this coordinated research and implementation approach, ACD continues to serve the scientific objectives of a variety of national and international programs of interest to the broad community, particularly the Global Tropospheric Chemistry Program (GTCP).

Table of Contents

FY 1996 Science Highlights

Educational Activities

FY 1996 Publications

Community Service

Staff, Visitors & Collaborators

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