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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de Haan's home page. last update: 4 Oct 2000 - PdH