Rotating tongues (Protrudences) of ozone- poor air in the Antarctic ozone hole, sweeping over lower latitudes : signatures in ground-based Dobson data

Abstract

Using data from ground-based Dobson spectrophotometers, the evolution of Antarctic ozone holes during the southern springs of 1992, 1993, 1994 and 1995 was studied, At the South Pole, the evolution was mostly smooth, steady decrease up to about September end and a steady recovery up to about December end, At latitudes near 65°5, the ozone levels at different latitudes and longitudes showed fluctuations compatible with passing of a noncircular (oval) vortex boundary, (edge, rotating tongue), with a rotation period of 15-20 days, However, often there were depletions in-between, extending to lower latitudes up to ~30°S, indicating corrugations in the oval boundary with effects equivalent to those of more than one rotating tongue, There were other short- spaced (5-8 days) depletions, not necessarily simultaneous at different latitudes in the same longitude, and more copious at lower latitudes, probably indicating the effects of synoptic disturbances on total ozone through tropopause pressure changes and/or ozone mini-holes caused by anticyclonic tropospheric forcing under the southern polar vortex.