Arctic polar vortex dynamics during winters 2014/2015 and 2020/2021

Abstract

The dynamic barrier of the polar vortex contributes to lowering the temperature inside the vortex in the lower stratosphere and prevents the penetration of air masses into the vortex. The presence of a dynamic barrier during winter is one of the criteria determining the possibility of ozone depletion from late winter to spring. We considered the dynamics of the Arctic polar vortex in the winters of 2014/2015 and 2020/2021 at the 50, 30 and 10 hPa levels by the vortex delineation method using the geopotential. In early January 2015 and 2021, sudden stratospheric warmings were recorded as a result of the splitting (4 January 2015) and the significant displacement (5 January 2021) of the polar vortex. In both cases, the weakening of the dynamic barrier of the polar vortex was observed. The polar vortex is characterized by the presence of a dynamic barrier, when the wind speed along the entire edge of the vortex is more than 20, 24 and 30 m/s at the 50, 30 and 10 hPa levels, respectively. A decrease in the average wind speed along the vortex edge below 30, 36 and 45 m/s, at the 50, 30 and 10 hPa levels, respectively, usually indicates a local decrease in the wind speed below 20, 24 and 30 m/s at these levels, i.e., indirectly indicates a weakening of the dynamic barrier.