摘要
Sudden stratospheric warmings(SSWs)are extreme cases of stratospheric polar vortex weakening[1].They are termed minor when a reversal of the stratospheric meridional temperature gradient in the subpolar region at 10 hPa and poleward of 60occurs,or major when this is accompanied by a complete reversal of the stratospheric circumpolar westerly jet[2].Although SSWs occur in both hemispheres,major SSWs are usually observed in the Northern Hemisphere,with a frequency of approximately six per decade.In contrast,only one major SSW has been recorded in the Southern Hemisphere,which occurred in 2002[3].
平流层爆发性增温(SSW)是指极区平流层的气温在几天内升高40~50°C,并伴随绕极西风急流减弱或崩溃的现象.SSW通常发生在北极地区,在南极很少出现,以往仅观测到1988年和2002年的两次事件.2019年9月,南极地区发生了一次罕见的SSW事件,出现了有观测记录以来最剧烈的极区升温和仅次于2002年的绕极西风急流减速,并造成了有观测记录以来面积最小的南极臭氧洞.对比分析表明,这3次SSW事件均出现在平流层准两年振荡的东风位相,并且前期都在南美洲附近的对流层出现了持续性的大气阻塞环流异常;阻塞环流加强了气候态的行星波,使行星波向平流层传播的波动能量显著加强,进而通过波流相互作用减弱绕极西风急流,从而导致SSW发生.这一结果强调了南美洲附近的大气阻塞在南极SSW事件发生中的作用,为理解南极SSW事件的特征和成因提供了难得的样本和科学证据.
作者
Xiaocen Shen
Lin Wang
Scott Osprey
沈小岑;王林;Scott Osprey(Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences;College of Earth and Planetary Sciences, University of Chinese Academy of Sciences;Atmospheric, Oceanic and Planetary Physics, University of Oxford;National Centre for Atmospheric Science, University of Oxford)
基金
supported by the National Key Research&Development Program of China(2018YFC1506003)
the National Natural Science Foundation of China(41925020,41721004)
supported by the Natural Environment Research Council(NE/P006779/1,NE/N018001/1)。
