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Mean flows driven by weak eddies in rotating systems

Published online by Cambridge University Press:  19 April 2006

A. D. Mcewan ,
R. O. R. Y. Thompson  and
R. A. Plumb
A. D. Mcewan
Affiliation:
CSIRO Division of Atmospheric Physics, Aspendale, Victoria, 3195, Australia
R. O. R. Y. Thompson
Affiliation:
CSIRO Division of Atmospheric Physics, Aspendale, Victoria, 3195, Australia Present address: CSIRO Division of Fisheries & Oceanography, Cronulla, N.S.W. 2230, Australia.
R. A. Plumb
Affiliation:
CSIRO Division of Atmospheric Physics, Aspendale, Victoria, 3195, Australia
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Abstract

General relations are derived for the forcing of a mean zonal flow in a damped rotating barotropic system through the action of weak eddies. In particular it is found that if the eddies are forced at localized latitudes the induced motion away from these latitudes is likely to be counter to the rotation (i.e. ‘easterly’). Over the forcing latitude the mean motion is always westerly except when the forcing provides a sink of relative momentum. In the case when the background field is deformed topographically to generate eddies the divergence of the Reynolds stress is balanced at lowest order by a dynamic pressure drag, and the mean motion takes the direction of propagation of the forcing.

The relations are applied to a linearized Rossby wave field in a viscous fluid driven by a moving system of boundary sources and sinks or hills and hollows. The results are compared with laboratory experiments. All major predictions are confirmed qualitatively, but the discrepancies in detail indicate the influence of nonlinear effects other than those incorporated in the theory.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 99 , Issue 3 , 14 August 1980 , pp. 655 - 672
Copyright
© 1980 Cambridge University Press

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