Details of the Conference organization

The 6th IGAC Conference was held in Bologna, Italy, from 13-17 September 1999 at the Conference Centre of the CNR Bologna Research Establishment. The Conference was sponsored jointly by IGAC, CNR's Institute for Atmospheric and Oceanic Sciences (ISAO), and the European Commission, DG XII-JRC. Three hundred and seventy-six scientists from 38 countries spanning 5 continents took part (Figures 1 and 2).

Figure 1. Distribution of participants in IGAC '99 among different regions of the world.	Figure 2. The 52 oral contributions divided by session and gender of the presenter.

The Conference was organized according to IGAC's three main foci:

• Biosphere-atmosphere interaction
• Atmospheric aerosols
• Atmospheric photooxidants

with the additional topic of:

• Atmospheric chemistry-climate interactions

The Conference format consisted of background review papers for each session presented by invited speakers, as well as contributed papers selected by the Conference Program Committee. A total of 54 oral papers was presented, including an opening lecture, "Atmospheric Chemistry: Developments During the Past Three Decades, and a Look Ahead", presented by Nobel laureate Paul J. Crutzen. John Miller, Head of the Environment Division of the World Meteorological Organisation, gave an invited lecture on the perspectives of the Global Atmosphere Watch program and its connections with IGAC. The majority of contributions were presented as posters, with a significant fraction of each afternoon devoted to poster sessions. These were always lively and well attended. A total of 298 posters were on display during the Conference, divided among the four above topics.

Session reports

Session 1: Biosphere-Atmosphere Interactions

(contributed by P. Ciccioli and A. Guenther)

A wide range of topics was presented in this session's oral and poster portions. The fundamental objective of the oral presentations was to assess the state of knowledge regarding exchanges of trace gases (mainly VOC, NOx, NH3, CO2, CH4) between the atmosphere and terrestrial and marine ecosystems and how these compounds play a fundamental role in global change through radiative forcing, ozone formation or acid deposition. Some oral presentations focused on methodological aspects related to flux determination by advanced techniques (such as micrometeorological methods, isotopic ratio analysis and inverse modeling). The possibilities afforded by these techniques were reviewed through critical analyses of recently collected data. Gaps to be filled in by ongoing and future research were clearly identified. Large emphasis was given to biogenic VOC due to their different photochemical ozone production potential and the possibility that they may act as a significant source of secondary aerosols. Presentations and discussions demonstrated that the role of biosphere-atmosphere interactions as a component of IGAC has expanded greatly in recent years from a few trace gases (CH4, N2O, isoprene, etc.) to a wide variety of compounds (acetaldehyde, acetone, toluene, selenium, NO, etc.). Another important direction has been a greater interaction between IGAC and other disciplines. Each of the other themes (aerosols, photooxidants, climate) had presentations that touched on the biosphere, which in turn had a number of presentations connected with the other three themes. Thus the biosphere work has advanced from being primarily studies of trace gas fluxes to investigations of the implications of these fluxes on atmospheric chemistry.

Session 2: Atmospheric Aerosols

(contributed by S. Fuzzi)

This session had the highest number of submitted contributions, an indication of this issue's increasing importance in the wider context of atmospheric chemistry. After spending much effort over the last decades on the study of gas phase processes, the role of multiphase processes in the atmosphere is now being fully recognized. The contributions at the Conference closely reflected the different areas of aerosol research: gas-to-particle conversion, aerosol–cloud interaction, aerosol source characterization, direct and indirect aerosol climate forcing. More than half of the presentations concerned field studies, while the rest were mainly modeling contributions, with only a few concerning laboratory studies. Efforts should be made in future conferences to involve a larger number of research groups from the laboratory community. Besides a majority of modeling and experimental contributions dealing with trends of aerosol concentrations and properties at different spatial scales, five subjects emerged as important components of international aerosol research: aerosol optical properties (mostly in relation to climate change), cloud processes, organic aerosol characterization and properties, mineral dust, biomass burning aerosol. These will certainly be the fields over the next few years where aerosol research will see major advancements. Also, at the time of the Conference the first important results of the ACE-2 experiment were being finalized for publication and several contributions were presented from this specific IGAC field campaign. A highly exciting future is to be expected for the whole field of multiphase atmospheric chemistry.

Session 3: Atmospheric Photooxidants

(contributed by S.A. Penkett and H. Akimoto)

The session on photooxidants contained some very interesting presentations describing progress over the past decade towards understanding the behavior of ozone in the troposphere, much of it with an IGAC label. Papers were presented describing the situation in Europe, over the North Atlantic, over the Pacific, and in Asia. The coverage was therefore truly global. Highlights included the close agreement between predicted and measured fields of ozone and its precursors in pollution incidents, similarities in ozone seasonal behavior at many sites across the Northern Hemisphere, and the use of satellites to study detailed aspects of ozone production and dispersion in large pollution episodes. The change of the tropospheric ozone budget between 1860 and 1990 was discussed based on the new modeling results. Universal consensus now exists that most of the ozone observed in the troposphere is formed there by chemical processing rather than being transferred from the stratosphere. Though there have been many advancements in our understanding of sources and sinks of tropospheric ozone, revealed in both modeling studies and perhaps a more accurate estimate of emissions of precursor compounds into the atmosphere, significant areas of uncertainty remain. Both these features were highlighted in the invited papers, one of which was entitled, "Indications and Extent and Cause of Global Ozone Pollution", drawing attention to the extensive long-range transport of continental air pollution now taking place, and another entitled, "Tropospheric Chemistry of OH and Ozone: New Developments and Challenges," which showed that in the upper troposphere, at least, our understanding of the free radical chemistry is far from perfect. In particular, attention to the heterogeneous loss of HO2 and NO3 on aerosols was called for. The need for further research for a quantitative understanding of tropospheric photochemistry was clearly recognized during this session.

Session 4:Atmospheric Chemistry-Climate Interactions

(contributed by J. Fishman)

This session reflected the growing complexity of the problems related to atmospheric chemistry. The overview paper was presented by Dr. Jeff Kiehl of the National Center for Atmospheric Research (USA) and highlighted how climate processes might respond to changes in atmospheric composition. The hydrologic cycle and how it is impacted by the surrounding chemistry is an important link in relating the climate system to atmospheric chemical composition and behavior. In particular, changes in clouds and precipitation can alter aqueous phase chemistry and the wet removal of species. Conversely, changes in convective activity can alter the vertical transport of chemical species. Just as natural modes of variability exist for the climate system, such modes exist for the chemical state of the atmosphere. An example of this was discovered in INDOEX. Due to the ENSO mode of variability in atmospheric circulation, there were significant shifts in the chemistry and aerosol effects in this region. Papers in this session illustrated the challenge in atmospheric chemistry to extrapolate local measurements to the global scale, and then assess what impact such perturbations have on the earth-climate system. Several papers highlighted findings from field programs spanning diverse spatial and temporal scales in regions from the temperate North Atlantic to the tropical Indian Ocean. Within the vertical domain, it was seen from the papers that composition changes at the surface may not be as important as chemical perturbations induced from subsonic jet aircraft flying at typical tropopause altitudes. In addition, the effects of aerosol composition on radiative transfer have added a new complexity to the role of aerosols in perturbing the climate. Lastly, the point was made that other links between modes of variability impacting the chemical and climate states need to be considered, as is the case with the exploration of any new research frontier.

Best poster awards

Four distinguished scientists (one for each session) had the task of selecting the best posters by young scientists (under 35 years old). The reviewers reported that the selection was not easy, since many posters were well prepared and contained new and very interesting results. At the end, the four selected posters were:

Session 1: Biosphere-Atmosphere Interactions

Scientist: Xu Xiaobin, Institute for Meteorology and Geophysics, J.–W. Goethe Univ., Germany

Poster title: Measurement of the exchange of COS and CS2 between the atmosphere and a forest using the relaxed eddy accumulation technique

Co-authors: H. Bingemer and U. Schmidt

Session 2: Atmospheric Aerosols

Scientist: Alena Kubatova, University of Antwerp, Dept. of Pharmaceutical Sciences, Belgium

Poster title: Carbonaceous aerosol characterization in the Amazon basin, Brazil

Co-authors: R. Vermeylen, M. Claeys, J. Cafmeyer,
W. Maenhaut, G. Roberts and P. Artaxo

Session 3: Atmospheric Photo-Oxidants

Scientist: Katja Riedel, Alfred-Wegener-Institute for Polar and Marine Research, Germany

Poster title: Variability of peroxides and formaldehyde in the Antarctic troposphere

Co-authors: R. Weller and O. Schrems

Session 4: Atmos. Chemistry-Climate Interactions

Scientist: Myke Zachariasse, Royal Netherlands Meteorological Institute, The Netherlands

Poster title: The influence of large-scale transport on the vertical ozone distribution over the Indian Ocean during the 1998 winter monsoon

Co-authors: P.F.J. van Velthoven, H.G.J. Smit & T. Mandall

It is worth noting that three of the four young scientists awarded prizes for best posters are women. All winners received a certificate and mementos.

The future of atmospheric chemistry

Roughly ten years have passed since the IGAC project was initiated by the Commission on Atmospheric Chemistry and Global Pollution (CACGP) and adopted as a Core Project of the International Geosphere–Biosphere Programme (IGBP). Presently the IGAC community is engaged in an integration and synthesis review to assess progress over the last decade. During the Conference a discussion was initiated of the future direction of global atmospheric chemistry research. Two panel discussions were organized, the first led by Hajime Akimoto and Leonard Barrie (President and Vice-President, respectively, of CACGP) and the second by Guy Brasseur (Chair of the IGAC Scientific Steering Committee). Leading scientists were asked to summarize their opinions before the floor was opened for discussion. Some major items were recognized as important gaps in knowledge to which renewed research efforts should be devoted in the future. A summary of these future needs for research in the field of atmospheric chemistry is given below.

Enhanced observation capability (for process study and trend detection)

• Satellites for troposphere constituents
• Networks (including vertical profiles and ancillary meteorological data)
• Instrument development (e.g., sensitive, robust devices to measure NH3, NO2, real time VOC, size-distributed particle properties, etc., including chemical sondes)
• Standardization and QC/QA internationally
• Data processing, interpretation and archiving

Atmospheric chemistry–cloud interactions

• Chemical controls on cloud processes
• Cloud impact on chemistry
• Gas-surface heterogeneous processes (involving ice, aerosols and Earth's surface)
• Gas-particle conversion
• Physico-chemical equilibria
• Reaction mechanisms/kinetics
• Near-tropopause studies

Troposphere/stratosphere exchange

• Chemistry in upper troposphere/lower stratosphere
  Regional emphasis
• Atmospheric chemistry in tropics & sub-tropic
• Continental effluent interaction with marine systems
• Eurasia
• Boreal Forest
• Role of urban complexes in regional/global chemistry
• Atmospheric chemistry–climate feedbacks

Carbon cycle and changing atmospheric chemistry

• Ozone tropospheric budget
• Aerosols
• Organic chemistry of the troposphere
• Education and communication

Final remarks

Participants unanimously expressed their pleasure at having been part of the IGAC Conference in Bologna. Several elements contributed to this appreciation: the high level of the presentations and posters, as well as the good organization and the kindness, warmth and efficiency of the Conference staff led by Mrs. Maria Teresa Tibaldi. Bologna was found to be a city rich in history and art. The city's cuisine was mentioned in several messages received by the Conference Organization. The 50 kg IGAC cake for the Conference dinner surely helped in this regard!

The IGAC '99 web page will be kept active for some time: new information on publication of the proceedings, updates, and a picture gallery can be found there.