Air and water quality modeling system: application to the Los Angeles metropolitan area

This paper describes a comprehensive modeling framework of the urban air and water environment.  The framework is composed of air chemistry (CIT), meteorology (RAMS and HOTMAC), stormwater runoff and quality (SWMM), and receiving-water quality (WASP) computer codes.  In this paper we describe the development of the urban air and water modeling framework, demonstrate its application to several simplified problems in the urban environment that require multi-disciplinary modeling, and investigate the issues and problems associated with data needs, model linkage, and model uncertainty.  The linked modeling system is applied to the transport of nitrogen species through air and water pathways in the greater Los Angeles metropolitan region.  We have simulated the meteorological flow fields, air chemistry and deposition processes, rain events, urban runoff and stormwater transport, pollutant loading and receiving-water chemistry. We will present estimates of nitrogen mass fluxes to the Santa Monica Bay from depositional runoff and deposition directly to the bay.  The framework is shown to be effective for evaluating the effects of air quality management policy on water quality management.