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ANALYSIS AND MODELING OF URBAN DISPERSION EXPERIMENTS IN DAYTIME AND NIGHTTIME ATMOSPHERE

Predictions of air pollutant dispersion over urban areas is a challenging problem because of the complexity of the topography, the number of physical factors governing the phenomenon, and their inherent uncertainty. We focus on the mean concentration field at ground level, which is a fundamental risk assessment factor. In general, the consensus is that the maximum ground-level mean concentration C as a function of the alongwind distance from the source x decays according to a C ∝ x−2 power law. Robins and Cheng (2003) present an empirical relationship establishing an upper bound to the observed concentrations: