Dynamic characteristics of the stratospheric polar vortices

Abstract

The dynamic characteristics of the stratospheric polar vortices at levels from 100 to 1 hPa (minimum vortex area, minimum mean wind speed along the vortex edge, and minimum wind speed at which there is a dynamic barrier), obtained using the vortex delineation method with geopotential based on ERA5 reanalysis data, presented for the first time. Seasonal changes and average winter vertical profiles of the vortex area, mean wind speed along the vortex edge, and mean temperature inside the vortex for the Antarctic and Arctic polar vortices were obtained. The average daily probability of weakening of the dynamic barrier along the vortex edge in winter was determined based on data for 1979–2021 over the Arctic and Antarctic. It is shown that the lowest probability of weakening of the dynamic barrier (and possible breakdown of the polar vortex) in winter can be traced at levels from 30 to 3 hPa and reaches less than 50% in the Arctic and less than 1% in the Antarctic. At the 50 hPa level, the probability of weakening of the dynamic barrier is 53.7% in the Arctic and 1.4% in the Antarctic.