Statistical evaluation of centerline concentration estimates by atmospheric dispersion models

Abstract: Within the American Society for Testing and Materials (ASTM) a Standard Practice (Z6849Z ) is being developed to provide an objective statistical procedure for comparing air quality simulation modeling results with tracer field data. The practice is limited to steady-state local-scale transport from isolated point sources in simple terrain. Evaluation data having similar external conditions are grouped together, and comparisons are made of the model’s ability to replicate without bias the average of the centerline maximum concentrations for each group. Centerline concentrations measured during three field studies are compared with estimates from three steady-state plume models (ISC, HPDM, and AERMOD). These results combined with those presented in Irwin and Rosu (1998) provide a complete examination of the draft ASTM Standard Practice under development. It is concluded that the evaluation methodology is capable of objectively discerning differences in skill between models in their ability to estimate the centerline maximum concentration.