TURBULENT DIFFUSION OF INSTANTANEOUS CLOUDS IN THE ATMOSPHERIC SURFACE LAYER: MEASUREMENTS AND COMPARISON WITH LAGRANGIAN SIMILARITY THEORY

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Authors
  1. Yee, E.
Corporate Authors
Defence Research Establishment Suffield, Ralston ALTA (CAN)
Abstract
The structure in a dispersing cloud, obtained from the sudden release of contaminant into the atmospheric surface layer, is experimentally investigated. An adequate number of controlled repeat releases (realizations) has been performed for each set of atmospheric conditions to allow ensemble averages of various functions of the cloud concentration to be obtained. The normalized ensemble-mean concentration and concentration variance crosswind profiles wer found to exhibit a self-similar Gaussian form. The evolution of the normalized lateral cloud width and of the normalized cloud centroid ensemble-mean concentration and concentration variance with travel time from the source is investigated. The results of teh statistical analysis are compared to predictions of puff dispersion in the constant stress layer obtained from Lagrangian similarity theory. Finally, an examination of the transport equation for the concentration variance shows that the rate of decay of the ensemble-mean concentration and root-mean-square concentration is equal in the turbulent-convective regime of cloud development, which in turn implies that the fluctuation intensity (i.e. standard deviation of concentration divided by mean concentration) remains constant within this regime of development.
Keywords
Atmospheric dispersion models
Report Number
DRES-OL-98-004 — Reprint
Date of publication
25 Feb 1998
Number of Pages
18
Reprinted from
Elsevier Physics Letters, vol A, no 242, 1998, p 51-62
DSTKIM No
98-02458
CANDIS No
509354
Format(s):
Hardcopy;Document Image stored on Optical Disk

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