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A three-dimensional regional modeling study of the impact of clouds on sulfate...

Kittaka, C., B. Pierce, J. Crawford, M. Hitchman, D. R. Johnson, G. Tripoli, M. Chin, A. R. Bandy, R. Weber, R. Talbot, and B. E. Anderson (2004), A three-dimensional regional modeling study of the impact of clouds on sulfate distributions during TRACE-P, J. Geophys. Res., 109, D15S11, doi:10.1029/2003JD004353.

The University of Wisconsin Nonhydrostatic Modeling System (UWNMS) is combined with an aqueous sulfur chemistry module to simulate the sulfate transport in east Asia during the Transport and Chemical Evolution Over the Pacific (TRACE-P) period. The simulated results are compared with in situ and satellite measurements collected during the TRACE-P period. The comparisons showed overestimates of sulfate mixing ratios by 20% between 1 and 6 km and underestimates by 30% near the surface and by 50% above 6 km. The comparisons of the sulfate mixing ratios between the simulation and the measurements for a case study of a convective system showed an excellent agreement in the background sulfate mixing ratios. The simulated sulfate mixing ratios in cloudy regions, however, were underestimated by a factor of 2. Volumeintegrated sulfate mass in the model domain is calculated. Significant amounts of sulfate (volume-integrated mass 1.5 × 106 to 7.5 × 106 kg) are released into air after being produced in clouds through the oxidation of sulfur dioxide by hydrogen peroxide. Instantaneous sulfate mass within clouds varies from 0.2 × 106 to 3.5 × 106 kg. Sulfate mass removed through precipitation is in the ranges between 0.01 × 106 and 1.8 × 106 kg. Sulfate mass in ice clouds was 2 orders of magnitude smaller than that in liquid clouds. This study shows that the sulfate input to the atmosphere exceeds the sulfate removed from the atmosphere through precipitation in the east Asian region during the TRACE-P. Consequently, east Asia in spring can be an important source region of sulfate and thus can offset the sulfate loss through precipitation scavenging in other regions of the globe.

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Tropospheric Composition Program (TCP)