AERMOD: Further Analysis of Evaluation Results

AERMOD is an advanced plume model that EPA is proposing for general regulatory use, replacing the Industrial Source Complex model. The model incorporates updated treatments of the boundary layer theory, understanding of turbulence and dispersion, and includes handling of terrain interactions. Previous papers have presented an overview of AERMOD’s evaluation results on 10 diverse databases. This paper analyzes the evaluation results in more detail, as described below.

Aside from model evaluation results presented as robust highest concentration statistics and quantile-quantile plots, it is important to understand other aspects of the behavior of the models being evaluated. This paper presents results obtained from an analysis of residual plots and conditions associated with the highest several predicted and observed concentration estimates. It indicates how the models that were evaluated compare with observations and each other as a function of stability, distance, wind speed, mixing height, and other important modeling parameters. The results will show areas in which AERMOD has exhibited improvements over existing modeling techniques, and other areas that may need additional study.