Tropical SST role on the anomalous SH polar vortex of 2002

The response of the Southern Hemisphere (SH) polar atmosphere to the tropical Sea Surface Temperature (SST) during the winter-spring season of 2002 is studied by using a General Circulation Model (GCM). The SH stratospheric winter of 2002 was particularly unusual. Characterized by a weaker than normal vortex during all the season, it registered, during the end of September, the first major Stratospheric Sudden Warming (SSW) yet observed in the SH. This type of event is unexpected in the SH and the “preconditioning” of the polar vortex, starting at the beginning of the winter, has been supposed to be crucial. Model results show a primary role played by the peculiar tropical SST of 2002 on the development of the Antarctic dynamics, through a teleconnection mechanism, starting during May with a signal at middle latitudes that progressively invests higher latitudes producing a destabilizing effect on the polar vortex during spring.