Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 5 5 2005 10.5194/acp-5-1399-2005 http://www.atmos-chem-phys.net/5/1399/2005/ http://www.atmos-chem-phys.net/5/1399/2005/acp-5-1399-2005.html http://www.atmos-chem-phys.net/5/1399/2005/acp-5-1399-2005.pdf 1399 1407 2005-06-10 Evolution of stratospheric ozone during winter 2002/2003 as observed by a ground-based millimetre wave radiometer at Kiruna, Sweden U. Raffalski G. Hochschild G. Kopp J. Urban Swedish Institute of Space Physics, Kiruna, Sweden Institute of Meteorology and Climate Research, Forschungszentrum Karlsruhe and Universität Karlsruhe, Germany Observatoire Aquitain des Sciences de l’Univers, L3AB, Floirac, France now at: Radio and Space Science Department, Chalmers University of Technology, Sweden We present ozone measurements from the millimetre wave radiometer installed at the Swedish Institute of Space Physics (Institutet f&#246;r rymdfysik, IRF) in Kiruna (67.8&deg; N, 20.4&deg; E, 420&nbsp;m asl). Nearly continuous operation in the winter of 2002/2003 allows us to give an overview of ozone evolution in the stratosphere between 15 and 55&nbsp;km. <P style="line-height: 20px;"> In this study we present a detailed analysis of the Arctic winter 2002/2003. By means of a methodology using equivalent latitudes we investigate the meteorological processes in the stratosphere during the entire winter/spring period. During the course of the winter strong mixing into the vortex took place in the middle and upper stratosphere as a result of three minor and one major warming event, but no evidence was found for significant mixing in the lower stratosphere. <P style="line-height: 20px;"> Ozone depletion in the lower stratosphere during this winter was estimated by measurements on those days when Kiruna was well inside the Arctic polar vortex. The days were carefully chosen using a definition of the vortex edge based on equivalent latitudes. At the 475&nbsp;K isentropic level a cumulative ozone loss of about 0.5&nbsp;ppmv was found starting in January and lasting until mid-March. The early ozone loss is probably a result of the very cold temperatures in the lower stratosphere in December and the geographical extension of the vortex to lower latitudes where solar irradiation started photochemical ozone loss in the pre-processed air. <P style="line-height: 20px;"> In order to correct for dynamic effects of the ozone variation due to diabatic subsidence of air masses inside the vortex, we used N<sub>2</sub>O measurements from the Odin satellite for the same time period. The derived ozone loss in the lower stratosphere between mid-December and mid-March varies between 1.1&plusmn;0.1 ppmv on the 150&nbsp;ppbv N<sub>2</sub>O isopleth and 1.7&plusmn;0.1&nbsp;ppmv on the 50&nbsp;ppbv N<sub>2</sub>O isopleth.