HR: 09:30h
AN: A31D-06 INVITED     [Abstracts]
TI: The stratospheric polar vortex: evolving perspectives
AU: * Plumb, R A
EM: rap@rossby.mit.edu
AF: Massachusetts Institute of technology, Room 54-1712 77 Massachusetts Ave, Cambridge, MA 01824 United States
AB: The discovery of dramatic Antarctic ozone depletion occurred at a time of rapid change in our understanding of stratospheric dynamics. The existence of the polar vortex, encircled by the polar night jet, had been well known for some time, as had the planetary scale Rossby waves that so dominate stratospheric meteorology. But, 25 years ago, the concepts of Rossby wave breaking, and of the "surf zone" and the sharpness of its boundaries at the vortex edge and in the subtropics, were relatively new, and the role of these waves in the driving of the mean diabatic circulation was not fully appreciated. While the local importance of gravity wave drag in the mesosphere was recognized by that time, its impact in the stratosphere was by no means clear. For a time, it was thought by many that the "ozone hole" was produced by anomalous polar upwelling, whose existence seemed to be demanded by observations of widespread, anomalously low temperatures in high southern latitudes in spring, which (at first) did not appear to be a consequence of depleted ozone. In the event, of course, chemical observations provided overwhelming support for the chemical depletion theory, while tracer observations, as well as revised radiative calculations, undermined the case for polar upwelling. The demands of stratospheric chemistry have always required that dynamical understanding of the stratosphere should extend beyond traditional meteorology to include questions of the transport of chemical species. Stratospheric transport has many facets, of which one - the impermeability of the vortex edge - was brought into focus by the appearance of the ozone hole and the need to understand the degree to which vortex air is isolated from its environment. The issue was controversial for a time, but analyses of tracer observations have confirmed expectations based on dynamical theory and on modeling studies that the isolation is strong, except during major vortex disturbances. Interest in polar vortex dynamics has included the remote effects on the vortex of the QBO in the tropical stratosphere, and of gravity wave drag and solar cycle influences at higher altitudes. In turn, there is accumulating evidence that variability in the polar vortices has remote effects at lower altitudes, manifested via the "annular mode" signals in the troposphere. Such issues raise questions about the interconnections between the troposphere, stratosphere and mesosphere, and about whether it makes sense, for example, to follow what used to be the conventional view and to regard stratospheric planetary waves and their impacts as being slaved to tropospheric meteorology. Amongst many of lines of evidence, no proximate tropospheric cause has been identified for the unprecedented Antarctic major warming of September 2002.
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3362 Stratosphere/troposphere interactions
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005