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contributor authorManney, G. L.
contributor authorZurek, R. W.
contributor authorO'Neill, A.
contributor authorSwinbank, R.
date accessioned2017-06-09T14:32:32Z
date available2017-06-09T14:32:32Z
date copyright1994/10/01
date issued1994
identifier issn0022-4928
identifier otherams-21289.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4157611
description abstractTrajectory calculations using horizontal winds from the U.K. Meteorological Office data assimilation system and vertical velocities from a radiation calculation are used to simulate the three-dimensional motion of air through the stratospheric polar vortex for Northern Hemisphere (NH) and Southern Hemisphere (SH) winters since the launch of the Upper Atmosphere Research Satellite. Throughout the winter, air from the upper stratosphere moves poleward and descends into the middle stratosphere. In the SH lower to middle stratosphere, strongest descent occurs near the edge of the polar vortex, with that edge defined by mixing characteristics. The NH shows a similar pattern in late winter, but in early winter strongest descent is near the center of the vortex, except when wave activity is particularly strong. Strong barriers to latitudinal mixing exist above about 420 K throughout the winter. Below this, the polar night jet is weak in early winter, so air descending below that level mixes between polar and middle latitudes. In late winter, parcels descend less and the polar night jet moves downward, so there is less latitudinal mixing. The degree of mixing in the lower stratosphere thus depends strongly on the position and evolution of the polar night jet and on the amount of descent experienced by the air parcels; these characteristics show considerable interannual variability in both hemispheres. The computed trajectories provide a three-dimensional picture of air motion during the final warming. Large tongues of air are drawn off the vortex and stretched into increasingly long and narrow tongues extending into low latitudes. This vortex erosion process proceeds more rapidly in the NH than in the SH. In the lower stratosphere, the majority of air parcels remain confined within a lingering region of strong potential vorticity gradients into December in the SH and April in the NH, well after the vortex breaks up in the midstratosphere.
publisherAmerican Meteorological Society
titleOn the Motion of Air through the Stratospheric Polar Vortex
typeJournal Paper
journal volume51
journal issue20
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/1520-0469(1994)051<2973:OTMOAT>2.0.CO;2
journal fristpage2973
journal lastpage2994
treeJournal of the Atmospheric Sciences:;1994:;Volume( 051 ):;issue: 020
contenttypeFulltext


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