Interannual Variability of the 500 mb Zonal Mean Flow in the Southern Hemisphere

Abstract

Abstract An analysis has been made of the means and variability of the 500 mb field in the Southern Hemisphere, with accent on the zonal means of geopotential height and westerly wind. Long-term means for May 1972-January 1978 are significantly different from previous analyses and reveal very large and significant trends in geopotential height, especially over Antarctica. Standard deviations of zonal winds and heights are larger than in the Northern Hemisphere and, in contrast to the Northern Hemisphere, are lowest in winter. Temporal variations in the zonal mean component of the flow are very pronounced and some aspects of the very anomalous flow in December 1976 are documented. Interannual variations show a remarkable quasi-biennial fluctuation in the zonal mean fields with a systematic progression of the anomalies from low to high latitudes. These are correlated with the quasi-biennial oscillation in the equatorial stratosphere.