Three extreme cold events invaded China during the early winter period between December 2020 to mid-January 2021 and caused drastic temperature drops, setting new low-temperature records at many stations during 6?8 January 2021. These cold events occurred under background conditions of low Arctic sea ice extent and a La Ni?a event. This is somewhat expected since the coupled effect of large Arctic sea ice loss in autumn and sea surface temperature cooling in the tropical Pacific usually favors cold event occurrences in Eurasia. Further diagnosis reveals that the first cold event is related to the southward movement of the polar vortex and the second one is related to a continent-wide ridge, while both the southward polar vortex and the Asian blocking are crucial for the third event. Here, we evaluate the forecast skill for these three events utilizing the operational forecasts from the ECMWF model. We find that the third event had the highest predictability since it achieves the best skill in forecasting the East Asian cooling among the three events. Therefore, the predictability of these cold events, as well as their relationships with the atmospheric initial conditions, Arctic sea ice, and La Ni?a deserve further investigation.

Guokun DAI;Chunxiang LI;Zhe HAN;Dehai LUO;Yao YAO

Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences,Fudan University,Shanghai 200438,China;CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China

大气科学进展（英文版）

[1]Guokun DAI;Chunxiang LI;Zhe HAN;Dehai LUO;Yao YAO-.The Nature and Predictability of the East Asian Extreme Cold Events of 2020/21)[J].大气科学进展（英文版）,2022(04):566-575

Predictability

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