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

Wicker, Wolfgang , Greatbatch, Richard John and Claus, Martin (2022) Sensitivity of a simple atmospheric model to changing surface friction with implications for seasonal prediction. Open Access Quarterly Journal of the Royal Meteorological Society, 148 (742, Part A). pp. 199-213. DOI 10.1002/qj.4200.

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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.

Document Type: Article
Keywords: atmosphere; barotropic governor; persistence; PUMA; signal-to-noise paradox; surface friction
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-OD Ocean Dynamics
Main POF Topic: PT2: Ocean and Cryosphere
Refereed: Yes
Open Access Journal?: No
Publisher: Royal Meteorological Society
Date Deposited: 18 Nov 2021 13:05
Last Modified: 07 Feb 2024 15:38
URI: https://oceanrep.geomar.de/id/eprint/54437

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