Stratospheric Polar Vortices


A prominent feature of Earth's stratosphere (10-50km) are cyclonic vortices which form over the winter poles. These vortices play an important in the coupling between the troposphere and stratosphere (e.g., Arctic Oscillation) and in ozone depletion (e.g., Antarctic Ozone Hole).

The structure and evolution of the Antarctic polar vortex in 1996 is shown in the animation of Potential vorticity (PV) from UKMO analyses Courtesy of Sean Winkler's web site. The vortex can also be seen in maps of trace constituents, e.g., animation below of CRISTA measurements of nitrous oxide mixing ratios at a pressure-altitude 10 hPa (about 30 km) From Michael McIntyre's web site.
Further illustrations of the Antarctic polar vortices can be seen in images of column-integrated ozone. The image below shows total ozone in October 1991, as measured by the TOMS instrument, with very low values (the "ozone hole") confined within the Antartic polar vortex. The isolation of air inside the vortex is highlighted in the image below which shows measurements of four different constituents from UARS satellite. There is a large difference in all constituents between inside and outside the vortex (black curves show the vortex edge region defined using potential vorticity).

The impact of the vortex on the Antarctic Ozone Hole was clearly illustrated in September 2002, when large scale wave activity split the polar vortex, and ozone hole, into two sections. The image below contrasts the ozone hole between September 2001 and 2002.

High resolution trajectory calculation show fine scale structure around the polar vortex and the transport of vortex air into the middle latitudes, as illustrated below. The reality of the fine scale features in such calculations has been verifed by comparisons with aircraft observations. Courtesy of Eugene Cordero.