REGIONAL PHOTOCHEMICAL AIR-QUALITY MODELING - MODEL FORMULATIONS, HISTORY, AND STATE OF THE SCIENCE

Regional air quality models have been used for scientific investigatio n of trace species dynamics for over two decades and are now beginning to take a central position in air quality management. In particular, they have been used for studying the transport and fate of atmospheric acids, photochemical oxidants (e.g. ozone), and more recently, aeroso ls. Such models are based on numerically solving the mass conservation equations for a chemically interacting system of species and are appl ied to horizontal domains of 1000s of kms. Primary applications includ e assessing the response of pollutant concentrations to emissions cont rols, quantifying the flux of pollutants across and out of a region, a nd understanding the impact of specific processes on pollutant concent rations.