Abstract
Abstract. Strong perturbations of the Arctic stratosphere during the winter 2002/2003 by planetary waves led to enhanced stretching and folding of the vortex. On two occasions the vortex in the lower stratosphere split into two secondary vortices that re-merged after some days. As a result of these strong disturbances the role of transport in and out of the vortex was stronger than usual. An advection and mixing simulation with the Chemical Lagrangian Model of the Stratosphere (CLaMS) utilising a suite of inert tracers tagging the original position of the air masses has been carried out. The results show a variety of synoptic and small scale features in the vicinity of the vortex boundary, especially long filaments peeling off the vortex edge and being slowly mixed into the mid latitude environment. The vortex folding events, followed by re-merging of different parts of the vortex led to strong filamentation of the vortex interior. During January, February, and March 2003 flights of the Russian high-altitude aircraft Geophysica were performed in order to probe the vortex, filaments and in one case the merging zone between the secondary vortices. Comparisons between CLaMS results and observations obtained from the Geophysica flights show in general good agreement. Several areas affected by both transport and strong mixing could be identified, allowing explanation of many of the structures observed during the flights. Furthermore, the CLaMS simulations allow for a quantification of the air mass exchange between mid latitudes and the vortex interior. The simulation suggests that after the formation of the vortex was completed, its interior remaind relatively undisturbed. Only during the two re-merging events were substantial amounts of extra-vortex air transported into the polar vortex. When in March the vortex starts weakening additional influence from lower latitudes becomes apparent in the model results. In the lower stratosphere export of vortex air leads only to a fraction of about 5% polar air in mid latitudes by the end of March. An upper limit for the contribution of ozone depleted vortex air on mid-latitude ozone loss is derived, indicating that the maximum final impact of dilution is on the order of 50%.
Highlights
The Arctic polar vortex in 2002/2003 was unusual in so far as low temperatures, below the threshold for Polar Stratospheric Cloud (PSC) formation, chlorine activation and ozone loss occurred very early already in mid December 2002 (Tilmes et al, 2003a; Goutail et al, 2005)
We use the Chemical Lagrangian Model of the Stratosphere (CLaMS) (McKenna et al, 2002b,a; Konopka et al, 2004, 2007) for a numerical simulation focusing on dynamical aspects like advection and mixing for this unusual Arctic winter episode
The Arctic winter 2002/2003 showed an unusual dynamical situation with strong planetary wave activity leading to perturbations of the polar vortex
Summary
The Arctic polar vortex in 2002/2003 was unusual in so far as low temperatures, below the threshold for Polar Stratospheric Cloud (PSC) formation, chlorine activation and ozone loss occurred very early already in mid December 2002 (Tilmes et al, 2003a; Goutail et al, 2005). Morgenstern et al (2003) proposed a method to quantify air mass origin using the SLIMCAT model and applied it to trace the transport of former polar vortex air into midlatitudes during and after the breakdown of the polar vortex In this way they were able to diagnose the substantial meteorological differences between the Arctic winters 1999/2000 and 2000/2001, where the vortex 1999/2000 was extremely long-lived leading to the production of vortex “fossils” that remain noticeable until early June 2000, whereas the dilution of vortex air in mid-latitudes in 2000/2001 was much faster. As long as significant and not too inhomogeneous chlorine activation prevails within the polar vortex and under daylight conditions, the contribution of vortex air to the probed air masses can be identified qualitatively by elevated ClO levels This was the case throughout the EUPLEX and ENVISAT Arctic Validation campaigns the signal gets weaker towards the end of the winter as chlorine becomes increasingly deactivated. The results of the simulation utilizing the suite of inert tracers will be used to quantify the effects of transport and mixing on the composition of the polar vortex and the midlatitudes
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