Both the Antarctic and Arctic polar stratospheres are occupied with giant cyclonic vortices in their winter seasons [1].These vortices are bounded by strong westerly winds, i.e., the polar night jets.Air within the stratospheric polar vortices is thus relatively isolated from the extratropical stratosphere.Because of the isolation and the lack of solar radiation during the polar night season,air within the stratospheric vortices is extremely cold.However,beyond these common features, the Antarctic and Arctic stratospheric vortices have significant differences.The Antarctic stratospheric vortex is usually stable and persists to late November.In contrast, the Arctic vortex can be either broken up or pushed out of the polar cap by strong planetary-scale waves, during which air temperatures within the Arctic stratosphere increase by 40-60 K within a week [1].This phenomenon is called stratospheric sudden warming (SSW), which occurs once every two years on average in the Arctic stratosphere.Stratospheric air is also much colder in the Antarctic than in the Arctic.For example, the climatological polar mean lowest temperature at 50 hPa in the Antarctic vortex is about-90 ℃ (averaged over 1979-2019), while it is about-68 ℃ in the Arctic [2].