Viscous Nongeostrophic Baroclinic InstabilitySource: Journal of the Atmospheric Sciences:;1986:;Volume( 043 ):;issue: 004::page 329DOI: 10.1175/1520-0469(1986)043<0329:VNBI>2.0.CO;2Publisher: American Meteorological Society
Abstract: Calculations have been performed of the (linear) stability of a baroclinic flow to three-dimensional perturbations. Both the simple Eady basic state and the rotating Hadley cell of Antar and Fowlis are considered. The independent influences of the Richardson (Ri), thermal Rossby (baroclinicity), Ekman, and Prandtl numbers are examined, as well as the influences of the angle of orientation of the horizontal wave vector and the wavelength. It is shown that if the wavelength is allowed to vary freely, disturbances of the Eady type are preferred (i.e., have greatest growth rate) unless Ri and Ekman numbers are small enough and the thermal Rossby number is large enough. In the latter case, disturbances whose angles of orientation are almost symmetric and whose wavelengths are mesoscale are preferred. If, on the other hand, the wavelength is fixed at a mesoscale size, only the symmetric and almost symmetric modes have growth. By allowing the wave vector orientation to deviate from purely symmetric, we note that the region of instability (i.e., critical Ri) is increased, the extent of which is greater for longer wavelength. For Prandtl number = 1, permitting the angle to be nonsymmetric demonstrates the existence of two maxima in growth rate at opposite angles of orientation and with very different energetics. For Prandtl number far enough from one and for large enough dissipation, only one of these two modes has positive growth rates. Growing oscillatory modes were found for some cases.
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contributor author | Miller, Timothy L. | |
contributor author | Antar, Basil N. | |
date accessioned | 2017-06-09T14:26:15Z | |
date available | 2017-06-09T14:26:15Z | |
date copyright | 1986/02/01 | |
date issued | 1986 | |
identifier issn | 0022-4928 | |
identifier other | ams-19232.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4155326 | |
description abstract | Calculations have been performed of the (linear) stability of a baroclinic flow to three-dimensional perturbations. Both the simple Eady basic state and the rotating Hadley cell of Antar and Fowlis are considered. The independent influences of the Richardson (Ri), thermal Rossby (baroclinicity), Ekman, and Prandtl numbers are examined, as well as the influences of the angle of orientation of the horizontal wave vector and the wavelength. It is shown that if the wavelength is allowed to vary freely, disturbances of the Eady type are preferred (i.e., have greatest growth rate) unless Ri and Ekman numbers are small enough and the thermal Rossby number is large enough. In the latter case, disturbances whose angles of orientation are almost symmetric and whose wavelengths are mesoscale are preferred. If, on the other hand, the wavelength is fixed at a mesoscale size, only the symmetric and almost symmetric modes have growth. By allowing the wave vector orientation to deviate from purely symmetric, we note that the region of instability (i.e., critical Ri) is increased, the extent of which is greater for longer wavelength. For Prandtl number = 1, permitting the angle to be nonsymmetric demonstrates the existence of two maxima in growth rate at opposite angles of orientation and with very different energetics. For Prandtl number far enough from one and for large enough dissipation, only one of these two modes has positive growth rates. Growing oscillatory modes were found for some cases. | |
publisher | American Meteorological Society | |
title | Viscous Nongeostrophic Baroclinic Instability | |
type | Journal Paper | |
journal volume | 43 | |
journal issue | 4 | |
journal title | Journal of the Atmospheric Sciences | |
identifier doi | 10.1175/1520-0469(1986)043<0329:VNBI>2.0.CO;2 | |
journal fristpage | 329 | |
journal lastpage | 338 | |
tree | Journal of the Atmospheric Sciences:;1986:;Volume( 043 ):;issue: 004 | |
contenttype | Fulltext |