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The animation below (which has been kindly made available to me by Joseph S. Scire from Earth Tech, Inc.) shows the ground level concentration for a unity source. The only difference between the right panel (the Lagrangian puff model CALPUFF) and the left panel (the ISC model) is the effect of causality, i.e. the puff model "knows" the history of the puffs, and advects them with the changing wind field, instead of assuming stationary (i.e. infinite in time) conditions for each time step as Gaussian plume models do. Source configuration, turbulence parameterizations and meteorology are identical for both models. The last slide depicts the 24-hr-average. It can be clearly seen that the ISC ground concentration plot is dominated by 1-hour-plumes "shot" towards infinitity, although the pollutants in reality often could not even possibly have reached some of those locations where ISC predicts high concentrations.

Replay the movie.

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