Biogenic Secondary Organic Aerosols: Observations to Global Modeling,”

A workshop series to promote US/Nordic country collaboration of young scientists.


The goals of this workshop are 1) to establish improved research collaboration between observationalists and modelers to reduce the uncertainty in the impact of biogenic SOA on climate and 2) to foster US/Nordic collaboration in this important research area, especially among early career scientists. We plan to address this by gathering a group of early career researchers who are active in laboratory and field measurements, process modeling, regional modeling and global modeling of biogenic aerosols and their impact on climate. This group will meet twice during a two-year period for meetings that will be designed to both provide an overview of the broad range of issues confronting researchers as well as to identify areas of collaboration that would not have otherwise developed. In addition, the workshop series will encourage continued collaboration by providing seed money for research during the 2 year period of the program.


Among the largest uncertainties in understanding human impacts on climate is the impact of aerosols on the radiative balance directly and through cloud interactions (Houghton et al., 2001). This uncertainty is due to both our inability to understand or predict aerosol abundance and composition on a global scale, and uncertainties in the impact of these aerosols on clouds and climate. For this workshop we shall focus on one specific type of aerosol— biogenic secondary organic aerosols. Globally, secondary organic aerosol (SOA) from biogenic precursors surpasses those from anthropogenic sources (Seinfeld and Pandis, 1998). These organic particles have important impacts on climate through their direct interactions with radiation, as well as their ability to modulate cloud condensation nuclei numbers, and thus cloud properties and precipitation. These processes exert a substantial influence back upon the earth system through links to the terrestrial carbon and water cycles (e.g., precipitation regulates plant growth and thus emissions of organic compounds) (Barth et al., 2005).

The questions that currently confront researchers working in the fields of biogenic SOA and their impact on the earth system are numerous and multidisciplinary. For example, currently little is known about the mechanism by which particles form in the atmosphere by nucleation and subsequent growth by condensation and coagulation. Although biogenic aerosol have been observed to grow to a size that become important as cloud condensation nuclei, little is known about their ability to form cloud droplets or ice crystals (Andreae et al., 2002). It is hypothesized that some secondary organic aerosols are water soluble and readily act as cloud condensation nuclei, while others may inhibit production of cloud droplets, but may on the other hand be effective for heterogeneous ice crystal formation. Regional models are just beginning to incorporate the processes that are important in the formation, transformations, and loss pathways of biogenic aerosol. Yet global modelers are still struggling with the computational costs of incorporating these processes.

It is precisely this diverse set of challenges that motivates this workshop series. The subject matter, “Biogenic Secondary Organic Aerosols: Observations to Global Modeling,” is an area in which both US and Nordic scientists are at the forefront. In Nordic countries, recent modeling developments have ranged from basic nucleation theories to detailed aerosol dynamic / atmospheric chemistry models. Examples of these include parameterizations of atmospheric nucleation for the sulfuric acid/ammonia/water system (Napari et al., 2002) and cluster activation theory for nucleation that may arise from the condensation of organic species onto single sulfuric acid molecules (Kulmala et al., 2004). Their experimental accomplishments span well defined laboratory investigations to continuous field measurements (including the longest continuous period of measurements of biogenic aerosol at the SMEAR-II site in Hyytiälä, Finland; Dal Maso et al., 2005). Other examples of recent experimental accomplishments include the University of Helsinki group’s pioneering work in use of instrumentation for detecting ambient ionic clusters in the atmosphere for the study of new particle formation. The Stockholm University group has a strong background in conducting unique observations of aerosol characteristics and cloud properties from aircraft, ship as well as ground at various locations all over the globe. Emphasis has also been made on using measurements in combination with detailed aerosol and meteorological models to better understand aerosol formation on a regional scale as well as the impact of aerosol composition and concentration on cloud formation (e.g. Tunved 2006a; Ekman et al., 2006). From this research, it has recently been shown that European boreal forests are a substantial source of both aerosol mass and aerosol number, providing an aerosol population of 1000 to 2000 climatically active particles per cubic centimeter during late spring to early fall (Tunved et al., 2006b).

As a demonstration of the strength of this research in the Nordic countries, the Nordic Center for Excellence research unit on Biosphere - Aerosol - Cloud - Climate Interactions (BACCI) was recently formed to bring together an interdisciplinary team to the study of biogenic SOA and its impact of climate change and human health. Nordic scientists involved in this research unit are also key figures in international scientific organizations and networks like ICCP, IGAC and EMEP. The US is also leading research in this field. Parameterizations have been developed for the emissions of a variety of biogenic organic compounds, which have been combined with GIS data to provide global distributions of emissions. Instruments developed by US investigators include techniques to detect, size, and measure the composition of newly formed nanometer-sized aerosol. Instruments have also been developed to measure key parameters to assess the importance of aerosol as cloud condensation nuclei. Process, regional and global models are incorporating size-classified and chemically specified aerosol.

The significant accomplishments of both US and Nordic scientists in the field has resulted in some collaboration between the two groups, such as in the field of observations and modeling of new particle formation in a boreal forest setting. One area that can benefit from additional collaboration is the incorporation of field and laboratory measurements in regional and global models. This requires a two-way communication so that the modelers are developing parameterizations that use up-to-date measurement results, and the observationalists are measuring quantities that reduce uncertainties in the models. Both US and Nordic scientists working in these areas will benefit from the workshop series.

The planned workshop will also interact with the existing programs in the International Polar Year (IPY) in several ways. First of all, it will engage US scientists to collaborate with scientists in Nordic countries, who tend to focus on polar issues due to their geographic location. For example, much of the measurement of the new aerosol formation from biogenic organics occurs in Finland, because of the strong group of Markku Kulmala. This will then improve the human infrastructure dedicated to understanding polar regions, one of the goals of the IPY ( Secondly, climate change in the polar regions is most intense. Biogenic emissions of secondary organic aerosol precursors are likely to change with changing vegetation in a warmer polar region. Thus, understanding the impact of these aerosols on climate has a special importance in the polar regions.

Recent meetings related to biogenic SOA.

To date, no meetings have been held with the specific objectives of fostering the interactions of early career scientists across the disciplines that define research in biogenic SOA / climate interactions. The most pertinent meetings to date have been lead by the Integrated Land Ecosystem – Atmosphere Processes Study (iLEAPS), a 10 year land-atmosphere core project of the International Geosphere-Biosphere Programme (IGBP):

1. “Formation and Growth of Secondary Atmospheric Aerosols” in Hyytiälä, Finland, 15-17 August 2005. Sponsored by iLEAPS/IGAC/SOLAS/ACCENT/BACCI. Topics that were covered included atmospheric chemistry behind new particle formation, processes in the biosphere related to atmospheric aerosol formation, nucleation, hygroscopic aerosol growth, instrumentation developments, meteorology behind atmospheric aerosol formation, global models, and biosphere-aerosol-cloud-climate interactions.

2. “First iLEAPS Science Conference” in Boulder, CO, USA, 21 – 25 January 2006. Topics included: 1) Land-atmosphere exchange of reactive and long-lived compounds: Key interactions and feedbacks in the Earth System; 2) Feedbacks between land biota, aerosols, and atmospheric composition in the climate system; 3) Feedbacks and teleconnections in the land surface, vegetation, water, and atmosphere system; 4) Material and energy transfer in the soil, canopy, and boundary layer system: Measurements and modeling; 5) Modeling of land-atmosphere interactions: Towards the Earth System approach


The key objective of the workshop series is to foster long term collaboration between early career scientists working in this field. Therefore the proposed structure will feature a group of about 20 young investigators, who will gather twice in a two-year period. In addition, each meeting will include 3 senior scientists (from US and Nordic countries) to provide mentorship to the participants and provide an opportunity for the early career scientists to meet and interact with their senior counterparts.

Chairs and committee

The organizing committee for this series of workshops will be comprised of a small group of early career scientists, which represent both US and Nordic countries as well as the broad range of disciplines that comprise the field of biogenic SOA. Individual members are Michael Boy (NCAR), Annica Ekman ( Stockholm University), Merete Bilde (University of Copenhagen), Natalie Mahowald (NCAR), Christine Wiedinmyer (NCAR), Jim Smith (NCAR), as well as senior scientist Markku Kulmala (University of Helsinki). Michael Boy is a Project Officer in iLEAPS and the organizer of the First iLEAPS Science Conference. He is an expert in the process scale modeling of secondary organic aerosols and is currently a post-doc at NCAR with close affiliations with the Kulmala group at Helsinki University. Annica Ekman is young scientist at Stockholm University who is an expert on regional scale modeling of aerosol/climate interactions. Merete Bilde, from the chemistry department at the University of Copenhagen, is an expert on aerosol/cloud interactions. Natalie Mahowald is a scientist at NCAR who is active in the incorporation of aerosols in the NCAR Community Climate System Model. Christine Wiedinmyer is a scientist at NCAR with expertise on emissions modeling and regional and global scale biosphere/atmosphere interactions. Jim Smith is a scientist at NCAR with expertise in the measurement of the physico-chemical properties of atmospheric nanoparticles (with sizes from 4 – 100 nm). Markku Kulmala is an internationally-renown researcher in the field of new particle formation by nucleation, and the head of the BACCI research unit within the Nordic Center for Excellence.

Locations and probable dates

The workshop series will consist of two meetings, each lasting one week and separated by one year. The first meeting will be held in Hyytiälä, Finland, during the Summer of 2007. The second meeting will be in Sweden, approximately 1 year later. The reason for two meetings is to not just generate new ideas on how to conduct research, but to follow-up on these ideas with some real research actions in the intervening time period.

Recruitment of meeting participants

Both meetings will be attended by the same group of 10 Nordic and 10 US early career scientists, as well as 3 senior scientists. Participants will be chosen by the organizing committee from the applicant pool. In order to broaden the applicant pool, we will advertise in appropriate journals (such as EOS) and institutions (e.g. UCAR member institutions and Nordic country universities). The selection process will adhere to the following guidelines:

  1. A special emphasis will be placed on the selection of junior researchers, here defined as individuals who are currently pursuing graduate research as well as those who are within 6 years of their PhD.

  2. A key element of the selection process will be ethnic and gender diversity of the participants. A key element of this in the US is making sure the applicant pool is diverse enough. We will ensure this by using email lists and addresses from the ASP and SOARS programs at NCAR, which have been very successful in recruiting a diverse applicant pool.

  3. An additional criterion will be the representation of the diverse range of research activities in this field biogenic SOA. This includes laboratory and field measurements and modeling activities ranging from process models to canopy and regional scales to global scales.

  4. Senior scientist participants will also be selected by the committee, and will be selected based on technical expertise as well as their willingness and ability to mentor early career scientists.

Visitor opportunity

In addition, we foresee having an additional ~40$k that will be used for travel money for research by the participants. This money can be requested by the US early career scientists involved in the workshops, and is intended to facilitate the collaboration initiated during the workshops. The money can cover travel expenses to visit their Nordic country collaborators, as well as limited related expenses (supplies, phone calls, etc.). Requests for funding will be reviewed by the organizing committee. Preference will be given for visits for scientists with no other funding resources for these collaborations.

Broader impacts

The goals of the workshop series are to push research forward on an important topic in climate change: impact of aerosols on climate and to foster collaboration between US and Nordic young scientists. Because of the follow-up meetings and availability of seed funding for additional collaborative visits, this series should result in activities that significantly improve our understanding and research on biogenic secondary aerosol interaction with climate.

A white paper on future science directions will be produced from the first meeting, which will be submitted to a journal such as EOS. The goal of these meetings to seed collaborative work across fields and geography that would then be supported by participants’ respective countries, and get into the regular peer-reviewed literature..

The expected impact is substantial new research collaboration on a vital climate change research topic between US and Nordic scientists. We hope that the program will include young scientists from NCAR as well as from the wider university audience.

In order to evaluate whether this program has been successful, we will track collaborations and papers that are initiated as part of this workshop series. For example, the selected participants will be asked to submit a list of their current collaborations and papers, and after the 2 year program, we will ask them to submit a list of their new collaborations and papers, and asked to indicate which papers were influenced by this program. We hope to dramatically increase the collaborations between countries.


Andreae, M. O., Artaxo P., Brandao C., Carswell F., Ciccioli P., da Costa A., Culf A. et al., 2002: Biogeochemical cycling of carbon, water, energy, trace gases and aerosols in Amazonia: The LBA-EUSTACH experiments, J. Geophys. Res., 107, D20, doi: 10.1029/2001JD000524.

Barth, M, McFadden, J., Sun, J., Wiedinmyer, C., Chuang, P., Collins, D., Griffin, R., Hannigan, M., Karl, T., Kim, S., Lasher-Trapp, S., Levis, S., Litvak, M., Mahowald, N., Moore, K., Nandi, S., Nemitz, E., Nenes, A., Potosnak, M., Raymond, T.M., Smith, J., Stroud, C. and Still, C., 2005: The coupling between land ecosystems and the atmospheric hydrological cycle, Bull. Amer. Meteor. Soc., 86(12), 1738-1742.

Dal Maso, M., M. Kulmala, I. Riipinen, R. Wagner, T. Hussein, P. P. Aalto, and K. E. J. Lehtinen, 2005: Formation and growth of fresh atmospheric aerosols: eight years of aerosol size distribution data from SMEAR II, Hyytiala, Finland. Boreal Environment Research, 10, 323-336.

Ekman, A., Wang, C., Ström, J., Krejci, R., 2006: Explicit simulation of aerosol physics in a cloud-resolving model: Aerosol Transport and Processing in the Free Troposphere. Journal of the Atmospheric Sciences, 63, 682–696.

Kulmala, M., Kerminen V. M., Anttila T., Laaksonen A., and O'Dowd C. D., 2004: Organic aerosol formation via sulphate cluster activation. Journal of Geophysical Research-Atmospheres, 109.

Napari, I., M. Noppel, H. Vehkamaki, and M. Kulmala, 2002: Parametrization of ternary nucleation rates for H2SO4-NH3-H2O vapors. Journal of Geophysical Research-Atmospheres, 107.

Tunved P., Korhonen H., Ström J., Hansson H.C., Lehtinen K.E.J., Kulmala M., 2006a: Is nucleation capable of explaining observed aerosol integral number increase during southerly transport over Scandinavia? Tellus, 58, 129-140.

Seinfeld, J. H. and S. N. Pandis, 1998: Atmospheric Chemistry and Physics. John Wiley and Sons.

Tunved P., Hansson H.C., Kerminen V.M., Ström J., Dal Maso M., Lihavainen H., Viisanen Y., Aalto P.P., Komppula M., Kulmala M., 2006b: High natural aerosol loading over boreal forests. Science, 312, 261-263.

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Last update: April 16, 2007.