Quantifying the Eddy Feedback and the Persistence of the Zonal Index in an Idealized Atmospheric Model
Name
Chen-2009-Quantifying the Eddy.pdf
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Author(s)
Chen, Gang R.
Plumb, R. Alan
Date Issued
December 2009
Journal
Journal of the Atmospheric Sciences
Publisher
American Meteorological Society
Citation
Chen, Gang, R. Alan Plumb, 2009: Quantifying the Eddy Feedback and the Persistence of the Zonal Index in an Idealized Atmospheric Model. J. Atmos. Sci., 66, 3707-3720 © 2010 American Meteorological Society
Version
Final published version
Abstract
An idealized atmospheric model is employed to quantify the strength of the eddy feedback and the persistence of the zonal index. The strength of the surface frictional damping on the zonal index is varied, and an external zonal momentum forcing is included to compensate for the momentum change associated with the friction change such that the climatological jet latitude and shape are unchanged.
The model can generate a nearly identical climatology and leading mode of the zonal mean zonal wind for different frictional damping rates, except when the jet undergoes a regime transition. For those experiments without a regime transition, as the surface friction is increased, the strength of eddy feedback is enhanced but the zonal index becomes less persistent. A simple feedback model suggests that the e-folding decorrelation time scale of the zonal index can be determined by the frictional damping rate and the strength of eddy feedback. The strength of eddy feedback is found to be related to the instantaneous vertical wind shears near the surface controlled by the frictional damping. Furthermore, the climate response to an external zonal torque is proportional to the decorrelation time scale, although the simple prediction used here overestimates the climate response by a factor of 2.
Subjects
feedback
eddies
climate models
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1175/2009jas3165.1
