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Barotropic instability of the Bickley jet

Published online by Cambridge University Press:  26 April 2006

S. A. Maslowe
Affiliation:
Department of Mathematics, McGill University, Montreal, P.Q. H3A 2K6, Canada

Abstract

The linear stability of the zonal shear flow $\overline{u} = - \sec h^2 y$ is investigated in the framework of the beta-plane approximation. This retrograde jet is known to be more unstable than its eastward-propagating counterpart and has some surprising characteristics. First, this is a rare example of a flow in which barotropically unstable modes occur that do not have a critical point. Secondly, singular neutral modes exist in which the critical point occurs at the centre of the jet, where $\overline{u}^{\prime}_{\rm c}=0 $. It is shown in this paper that such singular modes form part of the stability boundary both for the varicose mode and also for the radiating sinuous mode.

Type
Research Article
Copyright
© 1991 Cambridge University Press

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