Evaluation of a K-Model Formulated in Terms of Monin-Obukhov Similarity with the Results from the Prairie Grass Experiments
A K-model describing the dispersion of a passive substance was formulated in terms of Monin-Obukhov similarity theory, and then solved numerically for the case of the release of a passive substance from a point-source at ground-level. An extensive analysis was undertaken to evaluate this numerical model. To do this, we applied the widely used set of dispersion data for ground-level sources that was obtained during the Prairie Grass experiments. We simulated these dispersion experiments. Since SO2, which was used as tracer, is known to deposit on the ground, also the effect of deposition of the tracer was investigated. The simulations showed that the vertical concentration profile is greatly affected by deposition. At a height of 1.5 m, where the measurements were made, the effect is still weak 50 m from the source, but 800 m downwind the deposition causes a decrease in the concentration by about a factor of 2. When consideration is given to the effect of deposition, the numerical solution of the diffusion equation yields excellent agreement with the measurements of the crosswind-integrated ground-level concentrations for both the 200 m and 800 m distance. Indeed, at 800 m the predictions are consistent with measurements even into the convective regime, where the use of K-models becomes dubious.
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