Diagnostic and Process-Oriented Modeling Studies of the Tropospheric Cycles of S, N and Ozone

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9617378 Chameides This project consists of two separate but related investigations which focus on changes in the oxidative capacity of the atmosphere and to chemically-induced climate change. The first research activity will be the diagnostic analysis and modeling of datasets collected in sixteen flights over the Southern Ocean during the Southern Hemisphere Marine Aerosol Characterization Experiment (ACE-1). This experiment was carried out to better understand the chemical and physical processes that control the formation and climate-changing properties of atmospheric aerosols. Specific investigations planned using this portion of the ACE-1 dataset include: (i) testing of HxOy photochemical theory, (ii) assessment of tropospheric ozone photochemistry, (iii) estimates of ammonia oxidation and its role as a source of NOx, and (iv) investigations of gas phase sulfur chemistry and speciation and its gas-to-particle conversion. An added benefit of this study will be the development of a merged dataset of the relevant airborne measurements from ACE-1 as well as the modeling products, which will be made available to the international scientific community. The second major investigation will be a process-oriented modeling study designed to assess the coupled gas- and aqueous-phase chemistry of deliquescent mineral aerosols within the continental boundary layer. Specifically, the viability of aqueous phase oxidation within these particles as a sink of atmospheric sulfur dioxide and a source of particulate sulfate will be investigated. Initially, a generalized description for an internally-mixed coarse aerosol of crustal origin, based on data from the southern United States and from northern China, will be adopted. These descriptions will then be used to characterize the deliquescent characteristics of mineral aerosols at high relative humidity. An existing multi-phase atmospheric photochemical model will be used to elucidate the coupled gas- and aqueous-phase chemistry of these systems. Results from this study will be used to assess the role of mineral aerosols in the atmospheric sulfur budget within a global context using a 3-dimensional Chemical Transport Model developed at the Pacific Northwest Laboratory.