Large sudden warming in the Southern Hemisphere

Abstract

LARGE and rapid temperature changes, ‘sudden warmings’, can occur in the stratosphere during winter¹. They are hemispheric-scale phenomena, and, until recently, were supposed to be much weaker in the Southern Hemisphere winter than in the Northern Hemisphere winter. But during July 1974 a warming occurred in the Southern Hemisphere which was more intense in the initial phase than any of the three very large warmings of the past four Northern Hemisphere winters. The relatively early date of this warming (most large warmings in the Southern Hemisphere occur after late August at the end of the winter), its failure to produce the large heating of the polar cap which normally occurs in the Northern Hemisphere after such intense initial activity, and the large associated cooling in the tropics and Northern Hemisphere are further reasons for regarding this as a significant event.