H2SO4 Chemistry in the Stratosphere

Abstract:

Climate-chemistry models (e.g. Whole Atmosphere Community Climate Model (WACCM)) require an accurate representation of stratospheric processes including gas-phase sulfur chemistry. For background conditions, H₂SO₄formation occurs through a sequence of reactions starting with OCS and SO₂ sulfur precursors, primarily. The sulfur chemistry mechanism currently used in climate-chemistry coupled models contains limited chemical processing of H₂SO₄, i.e., UV photolysis is the only gas-phase loss process. However, reaction with radical species, such as O(³P), OH, O(¹D), and Cl atoms are likely to occur, although experimental data for these reactions are not currently available. In this study, theoretical methods will be applied to estimate the rate coefficients for these reactions. In addition, the possible role of the H₂SO₄-H₂O adduct will be examined. The impact of these reactions on sulfur partitioning in the stratosphere will be evaluated using WACCM.