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Cynthia S. Atherton Lawrence Livermore National Laboratory 7000 East Avenue Livermore, CA 94550 Tel: 925-422-1825 email: atherton2@llnl.gov This project will use IMPACT (Integrated Massively Parallel Atmospheric Chemical Transport model), a global, three-dimensional chemistry-transport-deposition model (Rotman et al., 2004). The model simulates the emissions, advection, diffusion, wet scavenging (rainout, washout, and re-evaporation), dry deposition, convection, gravitational settling, photolysis and chemical reactions governing gaseous and aerosol species. IMPACT’s domain, the troposphere, stratosphere, and the climatically critical tropopause region, requires roughly 100 species and 300 photochemical reactions. The IMPACT model is “driven” by meteorological information from either a general circulation model (GCM) or actual assimilated meteorological data. Using general circulation model meteorology allows us to examine climatologically average atmospheres (past, present, future). Using assimilated meteorological data allows us to compare model results directly with field campaign measurements for a particular time period. The model has been run at horizontal grid resolutions of 1˚ x 1˚, 2˚x 2.5˚, and 4˚ x 5˚ (latitude x longitude) with 25 to 55 vertical levels. Currently IMPACT predicts the distributions of five major aerosols components (sulfate, organic carbon, black carbon, dust, and seasalt), with the sixth component, nitrate, to be added shortly (Chuang et al., 2002b). IMPACT includes a radiation package that includes shortwave, near-IR, and longwave radiation (Grant et al., 1997; Grant et al., 1999), as well as parameterizations of aerosol optical properties to calculate the direct radiative forcing and heating/cooling rates by aerosols and greenhouse gases. In addition, parameterizations of drop concentrations have been implemented to calculate the first indirect aerosol effect (Chuang et al., 1997, 2002a). An aerosol microphysics sectional based module (Zhang and Wexler, 2002) is being implemented into the IMPACT model that will allow more realistic simulations of aerosol size distributions and mixing. [back to ASP ST Membership] |