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

中文翻译：

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1979-2020年南半球平流层极涡边缘强度和持续时间的演变

摘要。南半球平流层极涡边缘的强度和位置是根据 ECMWF ERA-Interim 再分析在 1979-2020 年期间在三个等熵水平（475 K、550 K 和 675 K）上作为等效纬度的函数进行评估的。该研究还包括对极地涡旋开始和破裂日期的分析，这些日期由风阈值（例如 15.2 ms ^-1、20 ms ^-1和 25 ms ^-1) 沿涡旋边缘。9月-10月-11月的冬末涡边缘更强，强度最强的时期出现在最低水平。在同一时期观察到边缘位置的较低可变性。在 1979 年至 1999 年期间观察到涡流边缘强度和破裂日期的长期增加，这与臭氧空洞的增加有关。与 25 ms ^-1相关的涡旋起始日期的长期减少在此期间还在 475 K 处观察到风阈值。太阳活动周期以及在较低程度上的准双年振荡 (QBO) 和厄尔尼诺南方涛动 (ENSO) 调节涡旋边缘强度和涡旋破裂日期的年际演化。在太阳极小期 (minSC) 年观察到更强的涡旋边缘和更长的涡旋持续时间，QBO 和 ENSO 进一步调节了太阳循环的影响，尤其是在 475 K 和 550 K：在西 QBO (wQBO) 阶段，涡旋边缘之间的差异minSC 和 maxSC 年的强度小于 East QBO (eQBO) 阶段。与 maxSC/eQBO 年相比，maxSC/wQBO 年的极涡边缘更强且持续时间更长。ENSO 的影响较弱，但在 minSC 和 maxSC 年的冷 ENSO 阶段，涡流边缘稍强。