AN INTEGRATED AIR-POLLUTION MODELING SYSTEM FOR URBAN AND REGIONAL SCALES .1. STRUCTURE AND PERFORMANCE

A new three-dimensional air pollution modeling system is described for urban and regional air quality studies. The system includes four majo r components: a meteorological model, a tracer transport code, a chemi cal and aerosol microphysical model, and a radiative transfer code. Th e meteorological model solves the equations of fluid dynamics and ther modynamics over complex terrain and incorporates physical processes su ch as turbulent diffusion, water vapor condensation and precipitation, solar and infrared radiative transfer, and ground surface processes. The tracer transport code computes the dispersion of gases and aerosol s throughout the atmosphere, including the effects of emission sources , and dry and wet deposition. The chemistry/aerosol model treats coupl ed gas-phase photochemistry and aerosol microphysics and chemistry. Ae rosol processes include nucleation, coagulation, condensational growth , evaporation, sedimentation, chemical equilibrium and aqueous chemist ry. A detailed radiative transfer code is attached to the dynamical an d chemical models. Absorption and scattering by gases and aerosols are explicitly treated to define photodissociation rates, heating and coo ling profiles, and boundary layer visibilities. The integrated modelin g system, which is referred to as the surface meteorology and ozone ge neration (SMOG) model, is shown to be a powerful tool for studying cou pled dynamical, chemical, and microphysical processes on urban and reg ional scales.