1National Institute of Water and Atmospheric Research, Lauder, New Zealand
2Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, New Jersey, USA
3Service d'Aeronomie du CNRS, Institut Pierre-Simon Laplace, Paris, France
4Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Wessling, Germany
5Max Planck Institut für Meteorologie, Hamburg, Germany
6Laboratoire de Meteorologie Dynamique, Paris, France
7Istituto Nazionale di Geofisica e Vulcanologia, Italy
8Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna, Italy
9Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland
10PMOD/WRC, Dorfstrasse 33, 7260, Davos Dorf, Switzerland
*now at: the Department of Applied Environmental Science, Stockholm University, Sweden
Received: 17 Sep 2008 – Published in Atmos. Chem. Phys. Discuss.: 01 Dec 2008 – Published: 03 Sep 2009
Abstract. While chemistry-climate models are able to reproduce many characteristics of the global total column ozone field and its long-term evolution, they have fared less well in simulating the commonly used diagnostic of the area of the Antarctic ozone hole i.e. the area within the 220 Dobson Unit (DU) contour. Two possible reasons for this are: (1) the underlying Global Climate Model (GCM) does not correctly simulate the size of the polar vortex, and (2) the stratospheric chemistry scheme incorporated into the GCM, and/or the model dynamics, results in systematic biases in the total column ozone fields such that the 220 DU contour is no longer appropriate for delineating the edge of the ozone hole. Both causes are examined here with a view to developing ozone hole area diagnostics that better suit measurement-model inter-comparisons. The interplay between the shape of the meridional mixing barrier at the edge of the vortex and the meridional gradients in total column ozone across the vortex edge is investigated in measurements and in 5 chemistry-climate models (CCMs). Analysis of the simulation of the polar vortex in the CCMs shows that the first of the two possible causes does play a role in some models. This in turn affects the ability of the models to simulate the large observed meridional gradients in total column ozone. The second of the two causes also strongly affects the ability of the CCMs to track the observed size of the ozone hole. It is shown that by applying a common algorithm to the CCMs for selecting a delineating threshold unique to each model, a more appropriate diagnostic of ozone hole area can be generated that shows better agreement with that derived from observations.
Struthers, H., Bodeker, G. E., Austin, J., Bekki, S., Cionni, I., Dameris, M., Giorgetta, M. A., Grewe, V., Lefèvre, F., Lott, F., Manzini, E., Peter, T., Rozanov, E., and Schraner, M.: The simulation of the Antarctic ozone hole by chemistry-climate models, Atmos. Chem. Phys., 9, 6363-6376, doi:10.5194/acp-9-6363-2009, 2009.