Investigation of the effect of the quasi biennial oscillation on the southern polar vortex

Abstract

Features of the southern hemisphere stratospheric winter vortex since the launch of UARS in 1991 are examined and compared. In particular, indicators of polar vortex strength and planetary wave activity are investigated using UKMO correlative dynamical data for evidence of modulation by the quasi-biennial oscillation (QBO) in the equatorial stratospheric wind. Despite relatively invariant planetary wave amplitudes at the tropopause, the amplitude of waves at middle stratospheric levels varied greatly each year, with particular contrast between the greatest activity in 1992 and the least activity in 1993. These corresponded respectively with a weaker vortex showing early break-up, and a stronger, more persistent, vortex.