||Environmental Protection Agency, Research Triangle Park, NC. National Exposure Research Lab. ;National Oceanic and Atmospheric Administration, Research Triangle Park, NC. Atmospheric Sciences Modeling Div. ;MCNC, Research Triangle Park, NC. North Carolina Supercomputing Center.
The key science characteristics and science process modules of the Models-3/CMAQ are discussed with respect to the terms in the governing atmospheric conservation equation. The authors also demonstrated the modular functionality of the CMAQ science process codes by comparing results with different numerical algorithms for a regional scale air quality simulation. The Models-3/CMAQ system achieves multipollutant and multiscale capability by combining several distinct modeling techniques. First, the authors recast the governing atmospheric diffusion equation in a generalized coordinate system to accommodate many different meteorological coordinates and assumptions on atmosphere. Second, CMAQ uses a nesting capability to refine grid resolutions to apply to the small-scale air quality problem. Third, a Plume-in-Grid module allows the computation of subgrid scale plume-scale dispersion and reactions. Finally, the multi-pollutant capacity is provided by a generalized mechanism chemistry reader, generalized mechanism chemistry reader, generalized chemistry solvers, linked aqueous reaction processor, and aerosol modules.