In the first half of winter 2020/21, China has experienced an extremely cold period across both northern and southern regions, with record-breaking low temperatures set in many stations of China. Meanwhile, a moderate La Ni?a event which exceeded both oceanic and atmospheric thresholds began in August 2020 and in a few months developed into its mature phase, just prior to the 2020/21 winter. In this report, the mid?high-latitude large-scale atmospheric circulation anomalies in the Northern Hemisphere, which were forced by the negative phase of Arctic Oscillation, a strengthened Siberian High, an intensified Ural High and a deepened East Asian Trough, are considered to be the direct reason for the frequent cold surges in winter 2020/21. At the same time, the synergistic effect of the warm Arctic and the cold tropical Pacific (La Ni?a) provided an indispensable background, at a hemispheric scale, to intensify the atmospheric circulation anomalies in middle-to-high latitudes. In the end, a most recent La Ni?a prediction is provided and the on-coming evolution of climate is discussed for the remaining part of the 2020/21 winter for the purpose of future decision-making and early warning.

International Center for Climate and Environment Science(ICCES),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China;Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science& Technology,Nanjing 210044,China;National Climate Center,Beijing 100081,China;University of Chinese Academy of Sciences,Beijing 100049,China;Department of Atmospheric and Oceanic Sciences& Institute of Atmospheric Sciences,Fudan University,Shanghai 200438,China;Beijing Municipal Climate Center,Beijing 100089,China

[1]Fei ZHENG;Yuan YUAN;Yihui DING;Kexin LI;Xianghui FANG;Yuheng ZHAO;Yue SUN;Jiang ZHU;Zongjian KE;Ji WANG;Xiaolong JIA-.The 2020/21 Extremely Cold Winter in China Influenced by the Synergistic Effect of La Ni?a and Warm Arctic)[J].大气科学进展（英文版）,2022(04):546-552

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