DIMETHYLSULFIDE CHEMISTRY IN THE REMOTE MARINE ATMOSPHERE - EVALUATION AND SENSITIVITY ANALYSIS OF AVAILABLE MECHANISMS

A box model of the marine boundary layer is used to simulate the oxida tion products of dimethylsulfide, including non-sea-salt (nss) sulfate , sulfur dioxide (SO2), methane sulfonic acid (MSA), dimethylsulfoxide (DMSO), methane sulfinic acid (MSEA), and dimethylsulfone (DMSO2), Th e gas phase oxidation schemes of Yin et al. [1990], Koga and Tanaka [1 993], Hertel et al. [1994], Pham et al. [1995], and Benkovitz et al. [ 1994] are compared with field measurements using nine scenarios. Heter ogeneous oxidation of SO2 in cloud droplets and sea-salt particles is also simulated. A sensitivity analysis is performed to evaluate which atmospheric parameters require the greatest attention in future field studies. Results indicate that the variations among the gas phase mech anisms are small with the parameterized mechanisms performing as accur ately as the comprehensive ones. Among the nine scenarios tested, nss- sulfate is predicted without bias. Predicted MSA and SO2 concentration s depend more on the gas phase mechanism, with the mechanisms tending to underpredict SO2 concentrations. Compared to differences in MSA and SO2 predictions, DMSO, MSEA, and DMSO2 predictions by the various mec hanisms are similar. Sulfate predictions are sensitive to the uncertai n parameterizations of heterogeneous processes. The interaction of the marine boundary layer with the free troposphere can explain much of t he discrepancy between the model predictions and measurements.