ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH GΓΆttingen, Germany 10.5194/acp-9-7901-2009 A new transport mechanism of biomass burning from Indochina as identified by modeling studies Lin C.-Y. 1 Hsu H.-m. 2 Lee Y. H. 2 Kuo C. H. 3 Sheng Y.-F. 1 Chu D. A. 4 Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan National Center for Atmospheric Research, Boulder, Colorado, USA Department of Geology, Chinese Culture University, Taipei, Taiwan Goddard Earth Sciences and Technology Center, NASA, Greenbelt, Maryland, USA 21 10 2009 9 20 7901 7911 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/9/7901/2009/acp-9-7901-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/7901/2009/acp-9-7901-2009.pdf

Biomass burning in the Indochina Peninsula (Indochina) is one of the important ozone sources in the low troposphere over East Asia in springtime. Moderate Resolution Imaging Spectroradiometer (MODIS) data show that 20 000 or more active fire detections occurred annually in spring only from 2000 to 2007. In our tracer modeling study, we identify a new mechanism transporting the tracer over Indochina that is significantly different from the vertical transport mechanism over the equatorial areas such as Indonesia and Malaysia. Simulation results demonstrate that the leeside troughs over Indochina play a dominant role in the uplift of the tracer below 3 km, and that the strong westerlies prevailing above 3 km transport the tracer. These fundamental mechanisms have a major impact on the air quality downwind from Indochina over East Asia. The climatological importance of such a leeside trough is also discussed.

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