Publication: Changes in polar stratospheric temperature climatology in relation to stratospheric sudden warming occurrence
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2012-11-22
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American Geophysical Union
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Abstract
Stratospheric Sudden Warmings (SSWs) strongly affect the polar stratosphere during winter months mainly in the Northern Hemisphere. The intraseasonal distribution and type of SSWs for the 1958-1979 and 1979-2002 periods in ERA-40 and NCEP-NCAR reanalyses reveal differences. In the pre-satellite era, most events occur in January and are vortex splits. In the post-satellite era, the distribution is bimodal (peaking in December and February), and shows more displacement events. The difference in the seasonal distribution of SSWs leads to changes in the climatological state of stratospheric temperatures, with differences up to 5.9 K at 10 hPa and 3.6 K at 20 hPa in February between pre- and post-1979 periods. We find that the temperature evolution at 20 hPa is in better qualitative agreement with theoretical expectations than at 10 hPa. Hence, 10 hPa may be affected more strongly by artifacts related with satellite data assimilation, which have, however, limited impact on identification of SSWs.
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We thank the Stratospheric Research Group of the FUB for preparing the stratospheric data. This research was supported by the Ministry of Economy and Competitivity of Spain under project TRODIM (CGL2007-65891-C02 and CGL2008-05968-C02-01). MGE was funded by FPI grant (BES-2008-005310). We are grateful to two referees for their helpful comments.