Developing State-Wide Modeling Guidance for the Use ofAERMOD – A Workgroup's Experience

摘要

For over two decades, the Industrial Source Complex (ISC) dispersion model has been thernprimary model used to predict ambient air impacts from stationary sources, particularly in regardrnto regulatory considerations when permitting new or modified sources. Recent advances inrndispersion modeling theory and computational power have led to major improvements over thernISC model. These improvements resulted in the creation of a new type of modeling algorithmrnreferred to as the American Meteorological Society/U.S. Environmental Protection AgencyrnRegulatory Modeling System (AERMOD).rnThe U.S. Environmental Protection Agency (EPA) has proposed replacing ISC with thernAERMOD dispersion model for evaluating near-field impacts for regulatory purposes,rnanticipating adopting it as the standard model by the end of 2005 and phasing out ISC in 2006.rnThis action will have numerous implications for industrial facilities and regulators. AERMODrnrequires several additional geophysical meteorological input parameters that ISC does not utilize.rnMuch discussion has taken place as to how these parameters should be set, but little overallrnguidance exists to assist modelers in determining their values. To address this lack of guidance,rnLouisiana Department of Environmental Quality (LDEQ) formed a Modeling Workgroup tornevaluate issues with implementing AERMOD and to develop modeling guidelines for use withrnAERMOD within the state of Louisiana.rnWorkgroup members performed several hypothetical case studies to (1) evaluate AERMOD’srnbehavior in comparison with ISC, (2) compare use of on-site meteorological data to National Weather Service (NWS) data, and (3) determine AERMOD’s sensitivity to changes in inputrnland-use parameters. The results of these analyses are being used to develop modelingrnguidelines, including site-specific parameters required by AERMOD.rnThe paper summarizes the results of analyses performed by Workgroup members, as well asrnrecommendations made by the members. In addition, general differences between ISC andrnAERMOD are discussed, including processing times, land-use parameters, meteorology inputs,rnand treatment of terrain.