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The role of wind shear in horizontal diffusion of ambient particles
Author(s) -
Smith F. B.
Publication year - 1965
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.49709138906
Subject(s) - shear (geology) , wind shear , eddy diffusion , plume , geology , diffusion , atmosphere (unit) , mechanics , displacement (psychology) , wind speed , meteorology , turbulence , atmospheric sciences , geometry , physics , mathematics , petrology , psychology , psychotherapist , thermodynamics
A change in the wind vector with height can have a very marked effect on the diffusion of tracers. Corrsin (1953), Saffman (1962) and Högström (1964) have shown that at large distances from the source of a tracer the horizontal spread of the cloud varies with time t like t 3/2 , provided the velocity shear is maintained over a sufficient depth of the atmosphere. Their result is extended in two ways, firstly to all values of t , and secondly by taking into account the correlation between horizontal and vertical eddy velocities. The most significant result of the latter effect is to reduce the displacement of the plume at any level in the direction of the shear. At small times of travel, it is shown that the relative spread is actually less in the presence of shear than predicted by the conventional ‘Taylor’ method.