The American Meteorological Society conducted a scientific review of a set of six urban diffusion models. TRC Environmental Consultants, Inc. calculated and tabulated a uniform set of statistics for all the models. The report consists of a summary and copies of the three independent model reviews conducted to evaluate the models. General conclusions included: (1) all of the six models are very similar to each other and represent simple approximations of the urban diffusion situations in a given time period with no horizontal variability of the boundary layer structure or depth; (2) none of the models can be considered state-of-the-art since a great deal has been learned about the planetary boundary layer that could be incorporated into such models; (3) the models all use an all or nothing approach to plume penetration; either the plume penetrates the elevated inversion and is lost to the computation or it is completely trapped; and (4) the four annual models all produced good estimates of the observed concentrations, while, of the short-term models, TEM-8A seriously overpredicted at night and RAM seriously underpredicts during the day.

"EPA-600/3-84-089." "Cooperative agreement no. 810297-01." "August 1984." Includes bibliographical references.