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contributor authorJin, F-F.
date accessioned2017-06-09T16:28:34Z
date available2017-06-09T16:28:34Z
date copyright2010/06/01
date issued2009
identifier issn0022-4928
identifier otherams-68550.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4210120
description abstractSynoptic eddy?mean flow interaction has been recognized as one of the key sources for extratropical low-frequency variability. In this paper, the underlying dynamics of this interaction are examined from the perspective of a synoptic eddy-induced dynamic instability. To delineate this instability, a barotropic model is used that is linearized with respect to a stochastic basic flow prescribed with both climatologic-mean flow and synoptic eddy statistics. This linear model captures the dynamics of feedback between synoptic eddy and low-frequency flow through a dynamic closure that relates the anomalous eddy vorticity forcing to low-frequency flow anomalies. After reducing this dynamic closure to its fundamental components, this stability is elucidated with analytical results under the most idealized consideration of basic flow. It is shown that through systematic alteration of the synoptic eddy structures in the basic flow, a low-frequency planetary-scale perturbation generates anomalous eddy vorticity forcing positively proportional to the vorticity of the perturbation. Such a perturbation amplifies itself; the energy source for its growth comes from the reservoir residing in the basic synoptic eddy activity. Thus, the growth rate of the synoptic eddy-induced dynamic instability depends primarily on the kinetic energy level of the basic synoptic eddy activity. Moreover, this instability is scale selective with preference for zonal symmetric and asymmetric planetary-scale modes, whose meridional and zonal scales are roughly in the range of those of the observed leading low-frequency patterns. Analysis of this synoptic eddy-induced instability provides insight into the origin of extratropical low-frequency variability.
publisherAmerican Meteorological Society
titleEddy-Induced Instability for Low-Frequency Variability
typeJournal Paper
journal volume67
journal issue6
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/2009JAS3185.1
journal fristpage1947
journal lastpage1964
treeJournal of the Atmospheric Sciences:;2009:;Volume( 067 ):;issue: 006
contenttypeFulltext


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