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Introduction
The ozone depletion has aroused the scientific over the last two decades. The concern about this issue is growing in the last years because of deeper Antarctic ozone losses and increasing vortex areas reaching populated regions in South America. In the Antarctic stratosphere a strong vortex forms in autumn, isolating the polar air from the surrounding mid-latitudes regions from April to the end of November. The low temperatures reached in this region allow the formation of polar stratospheric clouds (PSCs) and the initiation of heterogeneous chemical reactions inducing a rapid ozone decline in spring.
This paper is focused on the study of the Antarctic ozone depletion as observed at the Marambio station, located at 64.2 S, 56.7 W, in the period 1997-1999. The polar vortex position with respect to the Marambio station is studied in the equivalent latitude potential temperature quasi-conservative space which can be assimilated to an approximate vortex-following coordinate [McIntyre, 1980]. In this way, our analysis is free from adiabatical vertical motions and from the frictionless motions of the vortex on isentropic surfaces. A statistical study of the vortex occurrences above the station is performed for different isentropic levels and according to the season. The position of Marambio in time is classified in inner, edge and outer situations. Thereafter, the total ozone seasonal variability is studied and correlated with the position of the station with respect to the polar vortex. The total ozone data are taken from TOMS and the 475 K isentropic level is used to determine the equivalent latitude of the station for total ozone measurements. The analysis of the ozone variability as a function of potential temperature is performed qualitatively because of the poorer statistics of the ozone profiles database at Marambio obtained from ground based ozonesondes measurements. In the last part of this work, a comparison of the ozone depletion observed at Ushuaia [Pazmiño et al., 2000], the southern populated area from mid-latitudes (54.9 S, 68.3 W) and at the high latitude Marambio station.
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