Lagrangian Similarity Modeling of Vertical Diffusion from a Ground-Level Source

Thomas W. Hors Atmospheric Sciences Department, Battelle/Pacific Northwest Laboratories, Richland, WA 99352

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Abstract

The crosswind-integrated concentrations of a diffusing tracer were calculated from Lagrangian similarity theory and compared to field data at distances from 50–3200 m downwind of the ground-level tracer sources. The agreement between theory and data is good, supporting the usefulness of Lagrangian similarity theory for the prediction of ground-level concentrations to a dimensionless downwind distance of at least x/Z0=2×105. The comparison also demonstrates that 1) the eddy diffusivity of passive contaminants corresponds more closely to that of heat than that of momentum and 2) the effect of atmospheric stability on the ground-level concentrations may be closely predicted by altering the vertical scale of the diffusion without changing the form of the vertical distribution.

Abstract

The crosswind-integrated concentrations of a diffusing tracer were calculated from Lagrangian similarity theory and compared to field data at distances from 50–3200 m downwind of the ground-level tracer sources. The agreement between theory and data is good, supporting the usefulness of Lagrangian similarity theory for the prediction of ground-level concentrations to a dimensionless downwind distance of at least x/Z0=2×105. The comparison also demonstrates that 1) the eddy diffusivity of passive contaminants corresponds more closely to that of heat than that of momentum and 2) the effect of atmospheric stability on the ground-level concentrations may be closely predicted by altering the vertical scale of the diffusion without changing the form of the vertical distribution.

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