||Computer Sciences Corp., Research Triangle Park, NC. ;National Oceanic and Atmospheric Administration, Research Triangle Park, NC. Atmospheric Sciences Modeling Div. ;Environmental Protection Agency, Research Triangle Park, NC. Atmospheric Research and Exposure Assessment Lab.
A research and development effort to improve certain physical processes simulated in the Urban Airshed Model (UAM) processor and model programs, and to update the computer software is described. The UAM is an Eulerian photochemical grid model designed to simulate the relevant physical and chemical processes leading to ozone formation over urban-scale domains. An important task is the development of a comprehensive, meteorological processor program capable of generating several model input data files. Key modules include algorithms for computing the three-dimensional wind, temperature, and water vapor fields, surface energy budget fluxes, mixing heights, vertical eddy exchange coefficients, three-dimensional photolysis rates, and pollutant deposition velocities. The UAM model code has been updated to accept the meteorological processor data files and has been consolidated due to the removal of computational routines for dry deposition and exchange coefficients. Test runs to verify the correct implementation of code changes and to assess the impacts of new methods on predicated concentrations are described. The evaluation plans for the upgraded modeling system and an intercomparison of results with the regulatory UAM model using the Southern California Air Quality field measurements are also outlined.