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The structure of zonal jets in geostrophic turbulence

Published online by Cambridge University Press:  20 September 2012

Richard K. Scott  and
David G. Dritschel
Richard K. Scott*
Affiliation:
School of Mathematics and Statistics, University of St Andrews, St Andrews KY16 9SS, UK
David G. Dritschel
Affiliation:
School of Mathematics and Statistics, University of St Andrews, St Andrews KY16 9SS, UK
*
†Email address for correspondence: rks@mcs.st-and.ac.uk
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Abstract

The structure of zonal jets arising in forced-dissipative, two-dimensional turbulent flow on the -plane is investigated using high-resolution, long-time numerical integrations, with particular emphasis on the late-time distribution of potential vorticity. The structure of the jets is found to depend in a simple way on a single non-dimensional parameter, which may be conveniently expressed as the ratio , where and are two natural length scales arising in the problem; here may be taken as the r.m.s. velocity, is the background gradient of potential vorticity in the north–south direction, and is the rate of energy input by the forcing. It is shown that jet strength increases with , with the limiting case of the potential vorticity staircase, comprising a monotonic, piecewise-constant profile in the north–south direction, being approached for . At lower values, eddies created by the forcing become sufficiently intense to continually disrupt the steepening of potential vorticity gradients in the jet cores, preventing strong jets from developing. Although detailed features such as the regularity of jet spacing and intensity are found to depend on the spectral distribution of the forcing, the approach of the staircase limit with increasing is robust across a variety of different forcing types considered.

JFM classification

Geophysical and Geological Flows: Geostrophic turbulence Geophysical and Geological Flows: Quasi-geostrophic flows Mixing: Turbulent mixing
Type
Papers
Information
Journal of Fluid Mechanics , Volume 711 , 25 November 2012 , pp. 576 - 598
Copyright
Copyright © Cambridge University Press 2012

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