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Circumpolar vortex studies using MSU temperature data

Date

1996-10

Authors

Reasor, Paul D., author
Montgomery, Michael T., author

Journal Title

Journal ISSN

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Abstract

Irreversible mixing associated with breaking planetary waves at the edge of the circumpolar vortex exerts a westward force on the atmosphere. The tendency of this wave forcing is to decelerate the polar right jet and warm the polar regions of the stratosphere. While the tendency is opposed by an induced Eulerian-mean circulation, it is observed that substantial reductions in jet strength and departures from radiative equilibrium still occur. In the steady-state limit the departures from radiative balance at any level may be accounted for by the total wave forcing above that level. The wave forcing, and hence vortex strength, varies from year to year in a biennial fashion, suggesting a link with the equatorially-confined quasi-biennial oscillation (QBO) (Tung and Yang, 1994). These ideas will be explored in the context of a seasonal and interannual study of the austral circumpolar vortex using brightness temperature data from the Microwave Sounding Unit (MSU). Observations of the seasonal evolution of the vortex are presented along with direct and indirect evidence of wave forcing. A 50-mb vortex circulation index derived from the MSU is shown to qualitatively correlate with the phase of the QBO in some years. It is concluded, however, that the effects of wave forcing may be too weak in the lower stratosphere to consistently observe a QBO signal at high latitudes.

Description

October 1996.
Also issued as Paul D. Reasor's thesis (M.S.) -- Colorado State University, 1996.

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Subject

Polar vortex
Rossby waves

Citation

Associated Publications