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Sensitivity of a simple atmospheric model to changing surface friction with implications for seasonal prediction.

Authors :
Wicker, Wolfgang
Greatbatch, Richard J.
Claus, Martin
Source :
Quarterly Journal of the Royal Meteorological Society; Jan2022, Vol. 148 Issue 742, p199-213, 15p
Publication Year :
2022

Abstract

An ensemble of idealized experiments with the simplified general circulation model PUMA is used to analyze the response to reduced surface friction, that is a strengthening of the eddy‐driven jet, a weakening of the Eulerian mean overturning, and a suppression of baroclinic instability. The suppression of baroclinic instability is caused by an effect called the barotropic governor by which increased horizontal shear restricts the ability of baroclinic disturbances to convert available potential energy into kinetic energy. This governor effect ensures that the residual circulation and Eliassen–Palm flux (EP flux) divergence are largely invariant to the surface friction parameter despite the connection between surface friction, the Eulerian mean overturning, and the eddy‐momentum flux. The suppression of instability leads to an increase in persistence measured by the period of peak variance on synoptic time‐scales and a strengthened signal‐to‐noise ratio on seasonal time‐scales. These findings suggest that the signal‐to‐noise paradox seen in the context of seasonal prediction can be caused by excess mechanical damping in atmospheric prediction systems inhibiting the barotropic governor effect. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00359009
Volume :
148
Issue :
742
Database :
Complementary Index
Journal :
Quarterly Journal of the Royal Meteorological Society
Publication Type :
Academic Journal
Accession number :
155060172
Full Text :
https://doi.org/10.1002/qj.4200