ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-1961-2011 Forecasts and assimilation experiments of the Antarctic ozone hole 2008 Flemming J. 1 Inness A. 1 Jones L. 1 Eskes H. J. 2 Huijnen V. 2 Schultz M. G. 3 Stein O. 3 Cariolle D. 4 5 Kinnison D. 6 Brasseur G. 6 European Centre for Medium-Range Weather Forecasts, Reading, UK Royal Dutch Meteorological Institute, De Bilt, The Netherlands Research Center Jülich, IEK-8: Troposphere, Jülich, Germany Météo-France, Toulouse, France Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique, Toulouse, CNRS URA 1875, France National Centre for Atmospheric Research, Boulder, Colorado, USA 03 03 2011 11 5 1961 1977 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/11/1961/2011/acp-11-1961-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/1961/2011/acp-11-1961-2011.pdf

The 2008 Antarctic ozone hole was one of the largest and most long-lived in recent years. Predictions of the ozone hole were made in near-real time (NRT) and hindcast mode with the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The forecasts were carried out both with and without assimilation of satellite observations from multiple instruments to provide more realistic initial conditions. Three different chemistry schemes were applied for the description of stratospheric ozone chemistry: (i) a linearization of the ozone chemistry, (ii) the stratospheric chemical mechanism of the Model of Ozone and Related Chemical Tracers, version 3, (MOZART-3) and (iii) the relaxation to climatology as implemented in the Transport Model, version 5, (TM5). The IFS uses the latter two schemes by means of a two-way coupled system. Without assimilation, the forecasts showed model-specific shortcomings in predicting start time, extent and duration of the ozone hole. The assimilation of satellite observations from the Microwave Limb Sounder (MLS), the Ozone Monitoring Instrument (OMI), the Solar Backscattering Ultraviolet radiometer (SBUV-2) and the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) led to a significant improvement of the forecasts when compared with total columns and vertical profiles from ozone sondes. The combined assimilation of observations from multiple instruments helped to overcome limitations of the ultraviolet (UV) sensors at low solar elevation over Antarctica. The assimilation of data from MLS was crucial to obtain a good agreement with the observed ozone profiles both in the polar stratosphere and troposphere. The ozone analyses by the three model configurations were very similar despite the different underlying chemistry schemes. Using ozone analyses as initial conditions had a very beneficial but variable effect on the predictability of the ozone hole over 15 days. The initialized forecasts with the MOZART-3 chemistry produced the best predictions of the increasing ozone hole whereas the linear scheme showed the best results during the ozonehole closure.

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