A comparative study of the major sudden stratospheric warmings in the Arctic winters 2003/2004–2009/2010

Abstract

We present an analysis of the major sudden stratospheric warmings (SSWs) in the Arctic winters 2003/04–2009/10. There were 6 major SSWs (major warmings [MWs]) in 6 out of the 7 winters, in which the MWs of 2003/04, 2005/06, and 2008/09 were in January and those of 2006/07, 2007/08, and 2009/10 were in February. Although the winter 2009/10 was relatively cold from mid-December to mid-January, strong wave 1 activity led to a MW in early February, for which the largest momentum flux among the winters was estimated at 60° N/10 hPa, about 450 m2 s−2. The strongest MW, however, was observed in 2008/09 and the weakest in 2006/07. The MW in 2008/09 was triggered by intense wave 2 activity and was a vortex split event. In contrast, strong wave 1 activity led to the MWs of other winters and were vortex displacement events. Large amounts of Eliassen-Palm (EP) and wave 1/2 EP fluxes (about 2–4 ×105 kg s−2) are estimated shortly before the MWs at 100 hPa averaged over 45–75° N in all winters, suggesting profound tropospheric forcing for the MWs. We observe an increase in the occurrence of MWs (~1.1 MWs/winter) in recent years (1998/99–2009/10), as there were 13 MWs in the 12 Arctic winters, although the long-term average (1957/58–2009/10) of the frequency stays around its historical value (~0.7 MWs/winter), consistent with the findings of previous studies. An analysis of the chemical ozone loss in the past 17 Arctic winters (1993/94–2009/10) suggests that the loss is inversely proportional to the intensity and timing of MWs in each winter, where early (December–January) MWs lead to minimal ozone loss. Therefore, this high frequency of MWs in recent Arctic winters has significant implications for stratospheric ozone trends in the northern hemisphere.