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A presentation to the IGAC community on the "Joint SPARC-IGAC Climate-Chemistry Initiative"

A.R. Ravishankara, NOAA, Boulder, USA (ravi@noaa.gov)

An evening session was organised to present the joint SPARC-IGAC Climate-Chemistry initiative to the IGAC community during the recent 7th Scientific Conference of IGAC (and the 10th conference of IAMAS's CACGP). This symposium was called "Atmospheric chemistry within the Earth System: From Regional Pollution to Global Climate Change" held in Crete, Greece, during September 18-25, 2002. The special session was organised with the generous help and support of M. Kanakidou , the chair of the local organizing committee of the Symposium.

Nearly 100 people attended this session. The aim was to present to the community the need for bringing scientists working in this area together under the joint umbrella of SPARC and IGAC and to receive the response of the community to this joint effort. A.R. Ravishankara (SPARC SSG member and the SPARC lead for this initiative) and S. Liu (Co-chair elect of IGAC and the IGAC lead for this initiative) organised this session.

The session started with a short presentation of the science behind the climate-chemistry interactions and the need for a joint venture (see Figure) by A.R. Ravishankara.

He listed the following topics of possible mutual interest to IGAC and SPARC. This list was produced by the 14 participants of a small Discussion Session organised in Zurich earlier in 2002 and hosted by T. Peter (see previous SPARC Newsletter N°19).

1. The role of aerosols in chemistry, climate, and their interactions. The processing of aerosol in the atmosphere and their impact on chemistry and climate. Understanding and representing microphysical processes in numerical models.
2. The role of convection (both deep and warm) in controlling the water vapour abundance and redistribution of chemical constituents.
3. The role of tropical tropopause layer (TTL) in climate-chemistry interactions.
4. The extent and role of stratosphere-troposphere exchange (STE) in controlling the abundances of ozone and other species in the UT and lower stratosphere. Specifically, an accurate quantification of the STE contribution to tropospheric and upper-tropospheric ozone budget (which is likely to be a function of time and location).
5. The state of radiative transfer codes in calculating heating rates and photolysis rates.
6. The use of tracers and their variabilities in observations and in models to identify and diagnose roles and contributions of processes. An assessment of the role of inter-annual variability in the circulation patterns affecting the distribution of chemical constituents in the stratosphere and troposphere.
7. The role of lightning in the production and distribution of nitrogen oxides.
8. Determination of the fundamental parameters in kinetics, heterogeneous chemistry (specifically aerosols and ice in UT), photolytic processes, spectroscopy, and optical properties via laboratory studies. This is an on going as joint activity between SPARC and IGAC.
9. Satellite observations of trace species and meteorological parameters in the troposphere and lower stratosphere, assimilation of satellite observations, evaluation of models by using satellite data.

This presentation was followed by seven short invited presentations on topics noted next to their names:

1. J. Fishman GTOP
2. J. Burrows Satellites and what they can do
3. P. Crutzen Black Carbon and other topics
4. U. Platt Nitrogen oxides
5. J. Lelieveld Ozone & Other topics
6. L. Barrie Ice and surfaces
7. S. Liu A few concluding thoughts

There was some interesting discussion of the science by the participants. It was clear that there was a great deal of enthusiasm for this joint initiative and it was summed up by P. Crutzen's comment- "It is about time!" It was also clear that not all the research topics of interest to SPARC would also be high priority for IGAC and vice-versa. Based on the discussion, it was clear that a joint workshop was needed to further explore the contents of the joint initiative. This workshop will be held in the south of France on April 2-6, 2003, just prior to the joint EGS-AGU meeting. It is anticipated that a white paper on the highest priority research in the area of climate-chemistry interactions will emerge from this workshop and the following discussions.