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Publication . Article . 1996

An objective determination of the polar vortex using Ertel's potential vorticity

Eric R. Nash; Paul A. Newman; Joan E. Rosenfield; Mark R. Schoeberl;
Open Access
Published: 01 Apr 1996 Journal: Journal of Geophysical Research: Atmospheres, volume 101, pages 9,471-9,478 (issn: 0148-0227, Copyright policy )
Publisher: American Geophysical Union (AGU)
Abstract

We have developed objective criteria for choosing the location of the northern hemisphere polar vortex boundary region and the onset and breakup dates of the vortex. By determining the distribution of Ertel's potential vorticity (Epv) on equivalent latitudes, we define the vortex edge as the location of maximum gradient of Epv constrained by the location of the maximum wind jet calculated along Epv isolines. We define the vortex boundary region to be at the local maximum convex and concave curvature in the Epv distribution surrounding the edge. We have determined that the onset and breakup dates of the vortex on the 450 K isentropic surface occur when the maximum wind speed calculated along Epv isolines rises above and falls below approximately 15.2 m s -1 . We use 1992-1993 as a test case to study the onset and breakup periods, and we find that the increase of polar vortex Epv values is associated with the dominance of the term in the potential vorticity equation involving the movement of air through the surface due to the diabatic circulation. We also find that the decrease is associated with the dominance of the term involving radiatively induced changes in the stability of the atmosphere.

Subjects by Vocabulary

Microsoft Academic Graph classification: Geophysics Polar vortex Equivalent latitude Diabatic Breakup Tourbillon Geometry Vorticity Potential vorticity Vortex Physics

arXiv: Condensed Matter::Superconductivity

Subjects

Paleontology, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Atmospheric Science, Earth-Surface Processes, Geochemistry and Petrology, Soil Science, Water Science and Technology, Ecology, Aquatic Science, Forestry, Oceanography, Geophysics

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