Premium
A random walk model of dispersion in turbulent flows and its application to dispersion in a valley
Author(s) -
Thomson D. J.
Publication year - 1986
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711247213
Subject(s) - turbulence , dispersion (optics) , atmospheric dispersion modeling , random walk , flow (mathematics) , meteorology , tracer , mechanics , environmental science , ground level , geology , atmospheric sciences , physics , mathematics , statistics , optics , chemistry , engineering , architectural engineering , air pollution , ground floor , organic chemistry , nuclear physics
A random walk model of the dispersion of a passive tracer in a general three‐dimensional turbulent flow is developed. The model is used to simulate dispersion in the Sirhowy valley, South Wales. The results show encouraging agreement with the experimentally measured concentrations, which are generally much lower than those typical of dispersion over flat ground. The simulations show that, for releases from the summit on the upwind side of the valley, the low ground‐level concentrations in the valley are primarily a result of the mean flow and not the high turbulence levels in the valley. The simulations have been unable to explain the differences observed between experiments which were carried out in similar conditions; it is possible that the differences are simply a result of the inherent variability in the dispersion. The simulations have enabled estimates of a., and oz to be made; these quantities are difficult to obtain from the experimental data because of the lack of sufficient elevated samplers and the large horizontal area covered by the cloud.