Unusual stratospheric transport and mixing during the 2002 Antarctic winter

Abstract

Unusually large planetary wave activity in the 2002 Antarctic winter stratosphere weakened and warmed the polar vortex. Three minor warmings during August and early September preceded a late-September major warming when the middle stratospheric zonal winds reversed to easterly and the polar temperature increased by an additional 25 K. Polar Ozone and Aerosol Measurement (POAM III) ozone data at high southern latitudes show unusually large variability in 2002 compared to previous POAM III years (1998-2001). Analyses of air parcel transport indicate this variability is caused by large-scale isentropic transport. Diagnostics of transport and mixing show that during the major warming the lower stratospheric vortex remained intact, while the middle stratospheric vortex split into two pieces; one piece rapidly mixed with extravortex air, while the other returned to the pole as a much weaker and smaller vortex.