ATM-9320778 McElroy This research project is aimed at addressing key issues in stratospheric and tropospheric chemistry. For the stratosphere, (1) field observations will be used to test and refine our understanding of the role of heterogenous processes on the chemistry of the lower stratosphere; (2) diagnostic models will be developed and applied to elucidate the chemical and dynamical mechanisms responsible for long-term trends in the ozone, with particular attention to global effects of volcanic aerosols; and (3) the role of denitrification will be examined as the controlling influence on loss of ozone in polar regions, as part of a strategy to clarify differences between ozone loss in the Arctic and Antarctic. For the troposphere, the PI proposes to: (1) data for short-lived species from recent field expeditions will be used to test and improve photochemical mechanisms; (2) to test the distribution of hydroxyl radical in a global three-dimensional Chemical Tracer Model (CTM) will be tested using observations of carbon 14 labeled carbon monoxide; (3) the CTM will be used to test inventory of sources for carbon monoxide, a key species regulating hydroxyl radical concentrations, taking advantage of new data for carbon 13 labeled carbon monoxide and carbon 18 labeled carbon monoxide and including additional studies of ethylene and acetylene and (4) the CTM will also be used to investigate changes in the oxidizing power of the troposphere from 1950 to the present.
