Vertical dynamics of the stratospheric polar vortices during their anomalous strengthening in 2020
V.V. Zuev1, E.S. Savelieva1,2, V.L. Pravdin1, E.A. Sidorovski1
1Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
2A.M. Obukhov Institute of Atmospheric Physics Russian Academy of Sciences, Moscow, Russia
Keywords: stratospheric polar vortex, ozone depletion event, quasi-biennial oscillation, vortex area, wind speed at vortex edge
Abstract
Stratospheric polar vortices, which form over the polar regions in late autumn, are large-scale cyclonic formations whose stability in the winter-spring period determines the scale and depth of spring ozone depletion. Using the vortex delineation method based on ERA5 reanalysis data, we studied the features in the vertical dynamics of the Arctic and Antarctic polar vortices in 2020 during their anomalous strengthening, which was accompanied by deep and prolonged ozone depletion in the Arctic and Antarctic. In particular, we examined the synchronicity in temporal changes at different stratospheric levels. The polar vortex breakdown in 2020 was observed from late spring to early summer spreading from top to bottom over 1-2 months. The dynamics of the Arctic polar vortex showed three peaks of activity, spreading from the upper to the lower stratosphere within a month. The dynamics of the Antarctic polar vortex clearly showed one peak of activity spreading from the upper to the lower stratosphere over a period of 2 months. The anomalous duration of the western phase of the quasi-biennial oscillation in the middle stratosphere has been proposed as a possible reason for the unprecedented strengthening of the polar vortices in 2020. The results can be used to assess the risks of increasing ground-level UV-B radiation which is dangerous for the biosphere.
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