Contrasting physical mechanisms linking stratospheric polar vortex stretching events to cold Eurasia between autumn and late winter
Contrasting physical mechanisms linking stratospheric polar vortex stretching events to cold Eurasia between autumn and late winter
复制标题
DOI：
10.1007/s00382-023-07030-z
复制
发表时间：
2023-12
期刊：
影响因子：
4.6
通讯作者：
Chuntao Zou;Ruonan Zhang;Pengfei Zhang;Lei Wang;Ruhua Zhang
中科院分区：
文献类型：
--
作者：
Chuntao Zou;Ruonan Zhang;Pengfei Zhang;Lei Wang;Ruhua Zhang
平流层极涡（SPV）弱通常与北方半球的寒流有关。基于第五代ECMWF大气再分析和WACCM模式实验，我们使用K均值聚类分析提取了10月至2月平流层变化的纬向非对称模式，该模式涉及SPV的拉伸，从而导致北方半球中纬度地区的冷涌。秋季（11月至11月）和冬末（2月）SPV拉伸事件的影响和机制存在差异。10月，平流层环流的异常在SPV减弱后16-20天影响近地面。这有助于北大西洋涛动（NAO）向其负相位的转变，导致欧亚大陆北方上空的冷异常。第二次平流层-对流层耦合在31-40天期间与行星波-1的减弱共同加强了东亚大槽和西伯利亚高压，导致欧亚高纬地区的冷却。11月11-15日期间，波-1的向上传播受到抑制，这有利于北方欧洲上空的异常高压，从而通过平流层路径使欧洲降温，而21-30日期间，在东欧上空传播的波-2的减弱通过对流层路径加强了中纬度波列，这有利于中纬度东亚的低温。与此相反，晚冬SPV拉伸事件和伴随的11-25天的欧亚寒冷可能是由长期存在的欧洲高压异常同时驱动的，它增强了向上传播的对流层波进入平流层，从而有利于SPV拉伸。这表明，对流层路径，而不是平流层路径，在寒冷的欧亚大陆2月SPV拉伸事件后起主导作用。
The weak stratospheric polar vortex (SPV) is usually linked to Northern Hemisphere cold spells. Based on the fifth generation of ECMWF atmospheric reanalysis and WACCM model experiments, we use K-means cluster analysis to extract the zonally asymmetric pattern of October-February stratospheric variability, which involves a stretched SPV and hence leads to cold surges in Northern Hemispheric mid-latitudes. There are contrasting effects and mechanisms between autumn (October–November) and late winter (February) SPV stretching events. In October, anomalies in the stratospheric circulation affect the near-surface 16–20 days after the weakening of the SPV. This contributes to a shift in the North Atlantic Oscillation (NAO) towards its negative phase, leading to cold anomalies over northern Eurasia. Together with the weakening of planetary wave-1 during days 31–40, the second stratosphere–troposphere coupling strengthens the East Asian trough and the Siberian high, resulting in Eurasian high-latitude cooling. For November, the suppressed upward propagation of wave-1 during days 11–15 is conducive to anomalous high pressure over northern Europe and thereby European cooling through a stratospheric pathway, while for days 21–30, the weakening of propagating wave-2 over Eastern Europe intensifies the mid-latitude wave train through a tropospheric pathway, favorable for cold temperatures in mid-latitude East Asia. In contrast, the late winter SPV stretching events and the attendant Eurasian coldness during 11–25 days are likely to have been simultaneously driven by the long-lived European high anomaly, which enhanced the upward-propagating tropospheric waves into the stratosphere and thus favored SPV stretching. It indicates that the tropospheric pathway, rather than the stratospheric pathway, plays a dominant role in cold Eurasia following February SPV stretching events.