Analysis of aircraft and satellite measurements from the intercontinental chemical transport experiment (INTEX-B) to quantify long-range transport of East Asian Sulfur to Canada

A. van Donkelaar (1) , R. V. Martin (1, 2) , W. R. Leaitch (3) , A. M. Macdonald (3) , T. W. Walker (1, 4) , D. G. Streets (5) , Q. Zang (5) , E. Dunlea (6) , J. L. Jimenez (6) , J. E. Dibb (7) , G. Huley (8) , R. Weber (8) , M. O. Andreae (9)

1 Department of Physics and Atmospheric Science [Halifax]
2 CfA - Harvard-Smithsonian Center for Astrophysics
3 Science and Technology Branch
4 Dept. of Physics
5 Decision and Information Sciences Division
6 Department of Chemistry and Biochemistry
7 EOS Climate Change Research Center [Durham]
8 School of Earth and Atmospheric Sciences [Atlanta]
9 Biogeochemistry Department [Mainz]

We interpret a suite of satellite, aircraft, and ground-based measurements over the North Pacific Ocean and western North America during April?May 2006 as part of the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign to understand the implications of long-range transport of East Asian emissions to North America. The Canadian component of INTEX-B included 33 vertical profiles from a Cessna 207 aircraft equipped with an aerosol mass spectrometer. Long-range transport of organic aerosols was insignificant. Measured sulfate plumes in the free troposphere over British Columbia exceeded 1 ?g/m³. We update the global anthropogenic emission inventory in a chemical transport model (GEOS-Chem) and use it to interpret the observations. Trends in Aerosol Optical Depth (AOD) retrieved from two satellite instruments (MISR and MODIS) for 2000?2006 are analyzed with GEOS-Chem to estimate an annual growth in Chinese sulfur emissions of 6.2% and 9.6%, respectively. Analysis of aircraft sulfate measurements from the NASA DC-8 over the central Pacific, the NSF C-130 over the east Pacific and the Cessna over British Columbia indicates most Asian sulfate over the ocean is in the lower free troposphere (800?600 hPa), with a decrease in pressure toward land due to orographic effects. We calculate that 63% of the measured sulfate at 600 hPa over British Columbia is due to East Asian sources. Simulation of INTEX-B and May 1985 aircraft measurements off the northwest coast of the United States reveals a 2.4?3.4 fold increase in the relative contribution of East Asian sulfate to the total burden. Campaign-average simulations indicate anthropogenic East Asian sulfur emissions increase mean springtime sulfate in Western Canada at the surface by 0.14?0.19 ?g/m³ (~30%) and account for 40% of the overall regional sulfate burden between 1 and 5 km. Mean measured daily surface sulfate concentrations taken in the Vancouver area increase by 0.27 ?g/m³ per 10% increase in the simulated fraction of Asian sulfate, suggesting current East Asian emissions degrade local air quality.

Domaines: Océan, Atmosphère

A. van Donkelaar, R. V. Martin, W. R. Leaitch, A. M. Macdonald, T. W. Walker, et al.. Analysis of aircraft and satellite measurements from the intercontinental chemical transport experiment (INTEX-B) to quantify long-range transport of East Asian Sulfur to Canada. Atmospheric Chemistry and Physics Discussions, 2008, 8 (1), pp.4017-4057. ⟨hal-00303994⟩