Evolution of the intensity and duration of the Southern Hemisphere stratospheric polar vortex edge for the period 1979–2020

Abstract. The intensity and position of the Southern Hemisphere stratospheric polar vortex edge is evaluated as a function equivalent latitude over period 1979–2020 on three isentropic levels (475, 550, 675 K) from ECMWF ERA-Interim reanalysis. study also includes an analysis onset breakup dates vortex, which are determined wind thresholds (e.g., 15.2, 20, 25 m s−1) along edge. stronger in late winter, during September–October–November, with strongest occurring later at lowermost level. During same period, we observe lower variability position. A long-term increase break-up date observed 1979–1999, linked to ozone hole. decrease related s−1 threshold 475 K this period. solar cycle extent quasi-biennial oscillation (QBO) El Niño–Southern Oscillation (ENSO) modulate interannual evolution strength dates. longer duration minimum (minSC) years, QBO ENSO further modulating influence, especially 550 K: west (wQBO) phases, difference between for minSC maxSC years smaller than east (eQBO) phases. lasts maxSC/wQBO maxSC/eQBO years. has weaker impact but somewhat cold phases both