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2. Data

Long term ozone changes over Marambio, Antarctic peninsula (64.2°S, 57.7°W) have been studied using Dobson spectrophotometer total column measurements for the period of 1987-1999, and ozone mixing ratios at 435 K, 475 K and 550 K isentropic surfaces from ozone sonde measurements for 1990-1999. A classification of Marambios situation in relation to the polar vortex has been made using the potential vorticity and potential vorticity gradient analysis. Three classes have been selected: (i) inside vortex, (ii) outside of vortex and (iii) at the edge of vortex. The method is compared with some generally used other methods, and it seems that the method used in this study gives good results. The classification for November, and for December is characterised by the fact that the vortex is normally in a state of breakdown during these months. During May, June and July there is markedly less data available than during the other months. Eleven year (1957-67) means of total ozone at Argentine Islands (AI) (400 km SW from Marambio) are used as a pre-depletion reference.

A twofold procedure for the ozone sonde data quality assurance has been applied. First the ozone and temperature profiles were inspected visually to detect any obvious failures and anomalous spikes. After removal of the erroneous data the total ozone integrated from the profile was compared to spectrophotometric total ozone from the same day. On the basis of visual and quality check 55 out of total 436 ozone soundings were rejected. The data itself and a more detailed description of the data treatment procedure can be found in ozone.fmi.fi anonymous ftp-server from the /pub/Marambio directory.

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