ADVANCED ATMOSPHERIC MODELING FOR EMERGENCY RESPONSE

Atmospheric transport and diffusion models are an important part of em ergency response systems for industrial facilities that have the poten tial to release significant quantities of toxic or radioactive materia l into the atmosphere. An advanced atmospheric transport and diffusion modeling system for emergency response and environmental applications , based upon a three-dimensional mesoscale model, has been developed f or the U.S. Department of Energy's Savannah River Site so that complex , time-dependent flow fields not explicitly measured can be routinely simulated. To overcome some of the current computational demands of me soscale models, two operational procedures for the advanced atmospheri c transport and diffusion modeling system are described including 1) a semiprognostic calculation to produce high-resolution wind fields for local pollutant transport in the vicinity of the Savannah River Site and 2) a fully prognostic calculation to produce a regional wind field encompassing the southeastern United States for larger-scale pollutan t problems. Local and regional observations and large-scale model outp ut are used by the mesoscale model for the initial conditions, lateral boundary conditions, and four-dimensional data assimilation procedure . This paper describes the current status of the modeling system and p resents two case studies demonstrating the capabilities of both modes of operation. While the results from the case studies shown in this pa per are preliminary and certainly not definitive, they do suggest that the mesoscale model has the potential for improving the prognostic ca pabilities of atmospheric modeling for emergency response at the Savan nah River Site. Long-term model evaluation will be required to determi ne under what conditions significant forecast errors exist.