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Article
Article Type:
Research Article

Equilibration of Baroclinic Instability in Westward Flows

Timour Radko aDepartment of Oceanography, Naval Postgraduate School, Monterey, California

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James C. McWilliams bDepartment of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, California

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Georgi G. Sutyrin cGraduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island

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Online Publication:
28 Dec 2021
Print Publication:
01 Jan 2022
DOI:
https://doi.org/10.1175/JPO-D-21-0163.1
Page(s):
21–38
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Abstract

We explore the dynamics of baroclinic instability in westward flows using an asymptotic weakly nonlinear model. The proposed theory is based on the multilayer quasigeostrophic framework, which is reduced to a system governed by a single nonlinear prognostic equation for the upper layer. The dynamics of deeper layers are represented by linear diagnostic relations. A major role in the statistical equilibration of baroclinic instability is played by the latent zonally elongated modes. These structures form spontaneously in baroclinically unstable systems and effectively suppress the amplification of primary unstable modes. Special attention is given to the effects of bottom friction, which is shown to control both linear and nonlinear properties of baroclinic instability. The reduced-dynamics model is validated by a series of numerical simulations.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Timour Radko, tradko@nps.edu

Abstract

We explore the dynamics of baroclinic instability in westward flows using an asymptotic weakly nonlinear model. The proposed theory is based on the multilayer quasigeostrophic framework, which is reduced to a system governed by a single nonlinear prognostic equation for the upper layer. The dynamics of deeper layers are represented by linear diagnostic relations. A major role in the statistical equilibration of baroclinic instability is played by the latent zonally elongated modes. These structures form spontaneously in baroclinically unstable systems and effectively suppress the amplification of primary unstable modes. Special attention is given to the effects of bottom friction, which is shown to control both linear and nonlinear properties of baroclinic instability. The reduced-dynamics model is validated by a series of numerical simulations.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Timour Radko, tradko@nps.edu
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