ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-5-2981-2005 UV radiation below an Arctic vortex with severe ozone depletion Knudsen B. M. 1 Jønch-Sørensen H. 1 Eriksen P. 1 Johnsen B. J. 2 Bodeker G. E. 3 Danish Meteorological Institute, Copenhagen, Denmark Norwegian Radiation Protection Authority, Oslo, Norway National Institute of Water and Atmospheric Research, Lauder, New Zealand 07 11 2005 5 11 2981 2987 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.net/5/2981/2005/acp-5-2981-2005.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/2981/2005/acp-5-2981-2005.pdf

The erythemally weighted (UV) irradiance below the severely depleted Arctic vortices in spring 1996 and 1997 were substantially elevated. On average the UV increased 36 and 33% relative to the 1979-1981 mean assuming clear skies from day 80-100 in 1996 and 1997, respectively. On clear sky days large regions of the Arctic experienced maximum UV increases exceeding 70 and 50% on single days in 1996 and 1997, respectively. A minor fraction of these increases are not anthropogenic and have a dynamical origin as seen by comparison to 1982, when hardly any ozone depletion is expected.