The Extreme Major Stratospheric sudden Warming of January 2009

In mid-January 2009 North Polar temperatures at 10 hPa rapidly increased from 200 K to about 265 K in only a few days. Such extreme temperature increases are known as stratospheric sudden warmings. At the same time that the polar temperature was increasing, the zonal mean zonal wind decreased from 70 m/s to about -30 m/s. This extreme event was caused by the upward propagation of a very large planetary wave 2 – as evidenced by the Eliassen-Palm flux vector. The event was preceded by the development of a large planetary wave 2 in the upper troposphere during both the December and January period. In this presentation we will review the overall changes in both the stratosphere and troposphere from the polar region to the tropics. We will also contrast this extreme event with other large events from the meteorological record.