Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21. These events open a new window to detect possible underlying physical processes. The analysis here indicates that the occurrences of the three events resulted from integrated effects of a concurrence of anomalous thermal conditions in three oceans and interactive Arctic-lower latitude atmospheric circulation processes, which were linked and influenced by one major sudden stratospheric warming (SSW). The North Atlantic warm blob initiated an increased poleward transient eddy heat flux, reducing the Barents-Kara seas sea ice over a warmed ocean and disrupting the stratospheric polar vortex (SPV) to induce the major SSW. The Rossby wave trains excited by the North Atlantic warm blob and the tropical Pacific La Nina interacted with the Arctic tropospheric circulation anomalies or the tropospheric polar vortex to provide dynamic settings, steering cold polar air outbreaks. The long memory of the retreated sea ice with the underlying warm ocean and the amplified tropospheric blocking highs from the midlatitudes to the Arctic intermittently fueled the increased transient eddy heat flux to sustain the SSW over a long time period. The displaced or split SPV centers associated with the SSW played crucial roles in substantially intensifying the tropospheric circulation anomalies and moving the jet stream to the far south to cause cold air outbreaks to a rarely observed extreme state. The results have significant implications for increasing prediction skill and improving policy decision making to enhance resilience in "One Health, One Future".

Xiangdong ZHANG;Yunfei FU;Zhe HAN;James E.OVERLAND;Annette RINKE;Han TANG;Timo VIHMA;Muyin WANG

Univeristy of Alaska Fairbanks,Fairbanks,AK 99775,USA;University of Science and Technology of China,Hefei 230026,China;Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China;NOAA/Pacific Marine Environmental Laboratory,Seattle,WA 98115,USA;Alfred Wegener Institute,Helmholtz Center for Polar and Marine Research,14401 Potsdam,Germany;Finnish Meteorological Institute,FI-00101 Helsinki,Finland;University of Washington,Seattle,WA 98105,USA

大气科学进展（英文版）

[1]Xiangdong ZHANG;Yunfei FU;Zhe HAN;James E.OVERLAND;Annette RINKE;Han TANG;Timo VIHMA;Muyin WANG-.Extreme Cold Events from East Asia to North America in Winter 2020/21: Comparisons, Causes, and Future Implications)[J].大气科学进展（英文版）,2022(04):553-565

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