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The response of a zonally symmetric atmosphere to subtropical thermal forcing - Threshold behaviorWe consider the response of a zonally symmetric atmosphere to a thermal forcing that is localized in the subtropics. Specifically, the equilibrium temperature distribution has a local subtropical peak and is flat elsewhere, including at the equator. On the basis of inviscid steady-state theory, it is argued that the response to such forcing is one of two distinct types. Below a threshold forcing, the atmosphere adopts a steady state of thermal equilibrium with no meridional flow. With supercritical forcing, this state breaks down and a strong meridional circulation is predicted. The threshold forcing value is that at which the absolute vorticity of the zonal flow (in gradient balance with the equilibrium temperatures) vanishes at the upper boundary. These inviscid predictions are tested in a zonally symmetric numerical model; while the model viscosity shifts the threshold and otherwise modifies the response, the threshold is clearly evident in the model behavior.
Document ID
19930028341
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Plumb, R. A.
(MIT Cambridge, MA, United States)
Hou, Arthur Y.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 15, 2013
Publication Date
October 1, 1992
Publication Information
Publication: Journal of the Atmospheric Sciences
Volume: 49
Issue: 19
ISSN: 0022-4928
Subject Category
Meteorology And Climatology
Accession Number
93A12338
Distribution Limits
Public
Copyright
Other

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