ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-5-139-2005 Three-dimensional model study of the Arctic ozone loss in 2002/2003 and comparison with 1999/2000 and 2003/2004 Feng W. 1 Chipperfield M. P. 1 Davies S. 1 Sen B. 2 Toon G. 2 Blavier J. F. 2 Webster C. R. 2 Volk C. M. 3 Ulanovsky A. 4 Ravegnani F. 5 von der Gathen P. 6 Jost H. 7 Richard E. C. 8 Claude H. 9 Institute for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK NASA Jet Propulsion Laboratory, Pasadena, CA, USA J. W. Goethe University Frankfurt, Germany Central Aerological Observatory (CAO), Moscow, Russia Institute of Atmospheric Sciences and Climate (ISAC), Italian National Research Council, Bologna, Italy Alfred Wegener Institute, Potsdam, Germany NASA Ames, Moffett Field, CA, USA Aeronomy Laboratory, NOAA, Boulder, CO, USA Deutscher Wetterdienst, Germany 21 01 2005 5 1 139 152 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/5/139/2005/acp-5-139-2005.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/139/2005/acp-5-139-2005.pdf

We have used the SLIMCAT 3-D off-line chemical transport model (CTM) to quantify the Arctic chemical ozone loss in the year 2002/2003 and compare it with similar calculations for the winters 1999/2000 and 2003/2004. Recent changes to the CTM have improved the model's ability to reproduce polar chemical and dynamical processes. The updated CTM uses &sigma;-&theta; as a vertical coordinate which allows it to extend down to the surface. The CTM has a detailed stratospheric chemistry scheme and now includes a simple NAT-based denitrification scheme in the stratosphere. <P style="line-height: 20px;"> In the model runs presented here the model was forced by ECMWF ERA40 and operational analyses. The model used 24 levels extending from the surface to ~55km and a horizontal resolution of either 7.5&deg; x 7.5&deg; or 2.8&deg; x 2.8&deg;. Two different radiation schemes, MIDRAD and the CCM scheme, were used to diagnose the vertical motion in the stratosphere. Based on tracer observations from balloons and aircraft, the more sophisticated CCM scheme gives a better representation of the vertical transport in this model which includes the troposphere. The higher resolution model generally produces larger chemical O<sub>3</sub> depletion, which agrees better with observations. <P style="line-height: 20px;"> The CTM results show that very early chemical ozone loss occurred in December 2002 due to extremely low temperatures and early chlorine activation in the lower stratosphere. Thus, chemical loss in this winter started earlier than in the other two winters studied here. In 2002/2003 the local polar ozone loss in the lower stratosphere was ~40% before the stratospheric final warming. Larger ozone loss occurred in the cold year 1999/2000 which had a persistently cold and stable vortex during most of the winter. For this winter the current model, at a resolution of 2.8&deg; x 2.8&deg;, can reproduce the observed loss of over 70% locally. In the warm and more disturbed winter 2003/2004 the chemical O<sub>3</sub> loss was generally much smaller, except above 620K where large losses occurred due to a period of very low minimum temperatures at these altitudes.