Baroclinic instabilities of the two-layer quasigeostrophic alpha model
File(s)
Published version
OA Location
Author(s)
Holm, DD
Wingate, BIA
Type
Journal Article
Abstract
The class of alpha models for turbulence may be derived by applying Lagrangian averaging to the exact fluid equations and then making a closure approximation based on Taylor’s hypothesis of frozen-in fluctuations. This derivation provides a closed expression for the unknown pseudomomentum in the generalized Lagrangian mean theory of Andrews and McIntyre. In the current study, the mean effects of turbulence on baroclinic instability are explored, as determined by the two-layer quasigeostrophic-alpha model in quasigeostrophic (QG) balance. The QG-alpha model is found to lower the critical wavenumber, reduce the bandwidth of instability, and preserve the value of forcing at onset in the baroclinic case. It also preserves the fundamental dependence of baroclinic instability on the gradient of the potential vorticity. These results encourage using the alpha-model approach—based on combining Lagrangian averaging with Taylor’s hypothesis closure approximations—in simulations of global ocean circulation, because this class of turbulence closure models allows Lagrangian-averaged effects of baroclinic instability to be simulated on a coarse mesh.
Date Issued
2005-07-01
Date Acceptance
2004-11-26
Citation
Journal of Physical Oceanography, 2005, 35 (7), pp.1287-1296
ISSN
0022-3670
Publisher
American Meteorological Society
Start Page
1287
End Page
1296
Journal / Book Title
Journal of Physical Oceanography
Volume
35
Issue
7
Copyright Statement
© Copyright 2005 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (http://www.copyright.com). Questions about permission to use materials for which AMS holds the copyright can also be directed to permissions@ametsoc.org. Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (http://www.ametsoc.org/CopyrightInformation).
Identifier
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Subjects
Science & Technology
Physical Sciences
Oceanography
CAMASSA-HOLM EQUATIONS
TURBULENCE
WAVES
FLOWS
Publication Status
Published
Date Publish Online
2005-07-01