A Study of the Zonally Asymmetric Tropospheric Forcing of the Austral

Vortex Splitting During September 2002.

Dieter Peters*, Pawel Vargin** and Heiner Kornich***

* Leibniz-Institut fur Atmospharenphysik an der Universitat Rostock, Kuhlungsborn, Germany

** Central Aerological Observatory, Dolgoprudny, Moscow region, Russia

*** Department of Meteorology, Stockholm University, Sweden

Tellus (Journal of Geophysical Society of Sweden), 59A, p.384–394, 2007;

Abstract.

In September 2002, the first observed austral major warming was mainly characterized by a

polar vortex splitting in the middle and upper stratosphere together with an ozone hole

splitting. From our synoptic investigation based on ECMWF analyses, we establish the

hypothesis that lower tropospheric processes at polar latitudes are primary responsible for the

vortex splitting. Over the coastline of Antarctica two regions occurred, one over the Ross shelf ice and

the other over the Weddell shelf ice, where an enlarged tropospheric wave-activity generation in

connection with an anticyclonic anomaly took place. The wave-activity flux was eastward and

upward into the stratosphere, and was linked with an increasing ultra-long wave 2, which

could be the primary reason for the vortex splitting in the stratosphere. In the troposphere, two

Rossby wave trains have been identified which contribute mainly to the maintenance of the

anticyclonic anomalies over both wave-activity generation regions.