Latitudinal Extension of Cooling and Upwelling Signals Associated with Stratospheric Sudden Warmings

Abstract

Using two kinds of reanalysis data, this study explores latitudinal (southward) extension of cooling and upwelling signals in the stratosphere associated with major stratospheric sudden warmings (SSWs) in Northern winter. A composite analysis of SSWs reveals that the cooling and upwelling signals do extend to Southern mid-latitudes exceeding about 30°S. A further examination on event-to-event variability shows that the SSW-associated cooling in the equatorial stratosphere tends to be stronger when strong wave driving extends more equatorward to subtropical latitudes. Such changes to the wave driving are notable for several cases in horizontal patterns of planetary wave breaking.