Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 2 6 2002 10.5194/acpd-2-2489-2002 http://www.atmos-chem-phys-discuss.net/2/2489/2002/ http://www.atmos-chem-phys-discuss.net/2/2489/2002/acpd-2-2489-2002.html http://www.atmos-chem-phys-discuss.net/2/2489/2002/acpd-2-2489-2002.pdf 2489 2506 2002-12-16 The impact of mid-latitude intrusions into the polar vortex on ozone loss estimates J.-U. Grooß R. Müller Institut für Chemie und Dynamik der Geosphäre I: Stratosphäre (ICG-I), Forschungszentrum Jülich, Jülich, Germany Current stratospheric chemical model simulations underestimate substantially the large ozone loss rates that are derived for the Arctic from ozone sondes for January of some years. Until now, no explanation for this discrepancy has been found. Here, we examine the influence of intrusions of mid-latitude air into the polar vortex on these ozone loss estimates. This study focuses on the winter 1991/92. It is based on simulations performed with the Chemical Lagrangian Model of the Stratosphere (CLaMS). The simulations for January 1992 show that the intrusions induce a reduction of vortex average ozone mixing ratio corresponding to a systematic offset of the ozone loss rate of about 12 ppb per day. Further, the results of the Match method are influenced by the intrusions, since the intruded air masses are deformed and reach dimensions below the Match radius. From our calculations we deduce a systematic offset of the Match ozone loss rate by about 10 ppb/day, which may explain about 28% of the published discrepancy between Match and box model simulations for the winter 1991/92.