Transport and Transformation of Sulfur compounds over East Asia during the TRACE-P and ACE-Asia Campaigns

On the basis of recently estimated emission inventory for East Asia with a resolution of 1x1, the transport and chemical transformation of sulfur compounds over East Asia during the period of February 22 through May 4, 2001, was investigated by using the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system with meteorological fields calculated by the Regional Atmospheric Modeling System (RAMS). For evaluating the model performance simulated concentrations of sulfur dioxide (SO2) and aerosol sulfate (SO4 ) were compared with the observations on the ground level at four remote sites in Japan and on board of aircraft and vessel during TRACE-P (the Transport and Chemical Evolution over the Pacific) and ACE-Asia (Asian Pacific Regional Aerosol Characterization Experiment) field campaigns, and it was found that the model reproduces many of the important features in the observations, including horizontal and vertical gradients. The SO2 and SO4 2concentrations show pronounced variations in time and space, with SO2 and SO4 2behaving differently due to the interplay of chemical conversion, removal and transport processes. Analysis of model results shows that emission was the dominant term in regulating the SO2 spatial distribution, while conversion of SO2 to SO4 2in the gas phase and the aqueous phase and wet removal were the primary factors that control SO4 2amounts. The gas phase and the aqueous phase have the same importance in oxidizing SO2, and about 42%