Seminar

Abstract

Strong variations of the wintertime stratospheric polar vortex affect mid-latitude surface weather, providing a source of sub-seasonal to seasonal predictive skill. The polar vortex weakens when large-scale atmospheric waves break in the stratosphere, leading to rapid deceleration and occasionally a complete reversal of the vortex (an event called a sudden stratospheric warming or SSW). I will highlight a new database of these events, the SSW Compendium.

Although forecast models cannot predict the occurrence of SSWs more than 10 days out, it is possible that predictive information could be gained through identification of longer scale processes that impacts SSWs, such as the El Niño-Southern Oscillation (ENSO). During El Niño, SSWs occur more often, and the polar vortex tends to weaken in late winter. We investigate whether models that are able to capture the relationship between El Niño and the stratospheric polar vortex have higher seasonal predictive skill of Northern Hemisphere winter climate. A brief discussion of the 2015-2016 El Niño winter and its impacts on the polar vortex will be given.