ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-8-6501-2008 Increased UV radiation due to polar ozone chemical depletion and vortex occurrences at southern sub-polar latitudes in the period (1997–2005) Pazmino A. F. 1 2 Godin-Beekmann S. 1 Luccini E. A. 3 4 Piacentini R. D. 3 5 Quel E. J. 6 Hauchecorne A. 2 UPMC Univ. Paris 06, UMR 7620, Service d'Aéronomie, 75005, Paris, France Université Versailles St-Quentin, CNRS, UPMC, Service d'Aéronomie, Route Forestière de Verrières, 91370 Verrières-le-Buisson, France Inst. de Física Rosario (CONICET – Universidad Nacional de Rosario), Rosario, Argentina Facultad de Química e Ingeniería "Fray Rogelio Bacon", Universidad Católica Argentina, Rosario, Argentina Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, Rosario, Argentina CEILAP (CITEFA-CONICET), Villa Martelli, Argentina 04 04 2008 8 2 6501 6537 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/8/6501/2008/acpd-8-6501-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/8/6501/2008/acpd-8-6501-2008.pdf

The variability of total ozone and UV radiation from Total Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997–2005 period. The analysis of vortex occurrences showed high interannual variability in the 40° S–60° S latitude band with a longitudinal asymmetry showing the largest frequencies over the 90° W–90° E region. The impact of vortex occurrences on UV radiation and ozone in clear sky conditions was determined from the comparison between the measurements inside the vortex and a climatology obtained from data outside the vortex over the studied period. Clear sky conditions were determined from TOMS reflectivity data. For measurements outside the vortex, clear sky conditions were selected for reflectivity values lower than 7.5%, while for measurements inside the vortex, a relaxed threshold was determined from statistically similar UV values as a function of reflectivity. UV changes and ozone differences from the climatology were analyzed in the 40° S–50° S and 50° S–60° S latitude bands during the spring period (September to November). The largest UV increases and ozone decreases, reaching 200% and 65%, respectively, were found in the 50° S–60° S latitude band in September and October. The heterogeneous ozone loss during vortex occurrences was estimated using a chemical transport model. The largest impact of vortex occurrences was found in October with mean UV increase, total ozone decrease and accumulated ozone loss in the 350 K–650 K range of respectively 47%, 32% and 63%. The region close to South America is the most affected by the Antarctic ozone depletion due to the combined effect of large number of vortex occurrences, lower cloud cover and large ozone decrease. This region would be the most vulnerable in case of cloud cover decrease linked to climate change, due to more frequent occurrence of ozone poor air masses during austral spring.

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