Laboratory Studies of Cloud Microphysical and Chemical Phenomena Involving Ice

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Atmospheric trace chemicals interact with cloud and surface ice in complicated and ill-defined ways. With the recognition that future efforts to model the atmosphere-earth system will rely increasingly on basic knowledge about such interactions, a series of laboratory experiments is to be carried out under this research project. The sorption and chemical reactivity of several trace gases (SO2, H2O2, O3, HNO3, HCl, CH4, and NO) on ice will be investigated with gas chromatography frontal analysis over a broad range of temperatures (about -90oC to -20C). The kinetic and thermodynamic data will elucidate the molecular- scale mechanisms of incorporation and reaction and help to identify the factors controlling the reactivity of atmospheric trace gases that come in contact with ice. Other experimentation will be performed with a recently developed continuous-flow cloud chamber in order to measure the ability of ice growing in supercooled clouds to acquire particulate matter and retain volatile gases. Simple cloud models will be used to ensure that the findings of the laboratory experimentation are relevant to microphysical and chemical phenomena in atmospheric clouds.