Intercontinental Transport and Chemical Transformation (ITCT)

1. Intercontinental Transport and Chemical Transformation (ITCT) An Activity of the International Global Atmospheric Chemistry Project (IGAC) Today (briefly): • The inception of ITCT • Preliminary findings (the scientific basis of ITCT) • The principle science questions • The strategy and tools • Outline of planned research (More detailed presentations at this meeting)

2. Inception of ITCT The International Global Atmospheric Chemistry (IGAC)project was established (1988) to investigate the impact of chemistry on global climate change. (ozone and aerosols) Tokyo Workshop (March 16-17, 2000, Frontier Research Systems for Global Change). Steering committee formed; white paper accepted by IGAC; ITCT steering committee met (June 6 -7) and outlined a science plan. ITCT was formulated with the recognition that climate change had regional as well as global dimensions and ozone and aerosols had air quality, as well as, climate change implications.

3. The Northern Hemisphere Focus of ITCT: Focus on shorter-lived pollutants; ozone, aerosols. Much of the anthropogenic sources are in the Northern Hemisphere. For short-lived species, the ITCZ represents a line of demarcation that separates the world into two unique chemical zones; the Northern, where most of the land is, and the Southern, which is dominated by water. Since compounds are short-lived, most of the impact is in the Northern Hemisphere. The public concern with the chemical aspects of these species is strongly involved with air-quality (human and ecosystem impacts as opposed to climate). ITCT will try to address both regional climate and air-quality concerns. White papers available.

4. PRELIMINARY FINDINGS The Scientific Basis of ITCT from a Transatlantic Perspective (c.f., Parrish and Jacob this afternoon)

5. Large Amounts of Ozone Are Transported to the Remote Troposphere There is a strong seasonal variation in the anthropogenic influence on the tropospheric O3 budget. Ozone mixing ratio (ppbv) (Parrish et al.)

6. Layers provide an effective mechanism for the transport of continental pollution to mid and upper troposphere of the North Atlantic (Angevine et al.). Transport enhanced by fronts. Layers can be dominated by anthropogenic pollution or by stratospheric O3 (c.f., Stohl et al.). Identification of controlling meteorology (Topics described in posters: Cooper, McCaffery and McKeen.)

7. NOx controls photochemical O3 formation over the North Atlantic Emissions from forest fires influence air-quality on a hemispheric scale. √ CO (Wotawa and Trainer) CO (ppbv) O3, NOx (McKeen et al.) √ ? Aerosols Year (Parrish)

8. FUTURE PLANS (Science Questions, Approach, Plans ITCT from a Transatlantic Perspective)

9. THE PRINCIPAL SCIENCE QUESTIONS What are the export fluxes of oxidants, aerosols, and their precursors from the Northern Hemisphere continents to the global atmosphere? What is the ultimate fate of these substances exported to the global atmosphere? What are the impacts of intercontinental transport in the Northern Hemisphere on surface air quality? What are the impacts of changing emissions on regional and global atmospheric chemistry, composition, and climate? What are the impacts of climate variability on regional and global atmospheric chemistry and composition?

10. In order to quantify intercontinental transport and chemical transformation observations and models must be integrated. Source/sink inventories Assimilated meteorological data Chemical and aerosol processes INTERCONTINENTAL TRANSPORT: CONCENTRATIONS AND FLUXES Agreement with reasonable uncertainty THE STRATEGY AND TOOLS SATELLITE OBSERVATIONS Global and continuous but few species, low resolution Question - HOW 3-D CHEMICAL TRACER MODELS SURFACE OBSERVATIONS high resolution but spatially limited AIRCRAFT OBSERVATIONS High resolution, targeted flights provide critical snapshots for model testing

11. Transpacific 2001 - 2002: APARE (ACE and TRACE) interpretation. 2002 - :North American inflow experiment, scooping study and interpretation. Planning further inflow out flow experiments. • Transatlantic • 1997 - 2001: NARE interpretation. • 2001 - 2003: Development of Azores sampling site to add to measurements at other locations. 3. 2002 - : Planning future inflow/outflow experiments. Trans-Eurasian • Establishment of Chinese and Russian sites and/or platforms. • Planning European outflow and Asian inflow experiments. Exchange with Polar and Tropical Regions • Mid-latitude industrial emissions. • Boreal, tropical biomass burning. OUTLINE OF PLANNED RESEARCH