Use of meteorological models as input to regional and mesoscale air quality models — limitations and strengths

The importance of meteorological variability and uncertainty is described and discussed in the context of dispersion and chemistry of air pollution. Synoptic, mesoscale, and turbulent scales are defined in relation to pollution dilution. Spatial variability effects due, for example, to synoptic baroclinicity, propagating synoptic and mesoscale features, and surface-forced atmospheric circulations are described. Temporal variability resulting from diurnal and seasonal effects are discussed and examples presented. Among the questions addressed is the importance of differential advection relative to horizontal diffusion at different space and time scales. The concept of delayed diffusion is presented. Among the conclusions is that regulating agencies such as the EPA and NPS have generally not taken sufficient advantage of regional and mesoscale meteorological model-generated wind and turbulence fields, nor used the limits on the accuracy of these models to provide an upper limit to the skill of air quality models. Part of this failure is due to thepoor communication by scientific researchers, of model capabilities and limits to the agencies and other users of meteorological model output as part of air quality assessments.