Possible Linkage Between Winter Extreme Low Temperature Over Western-Central China and Autumn Sea Ice Loss

摘要

Based on reanalysis datasets and sea-ice sensitivity experiments, this study has pointed out that the autumn sea ice loss in East Siberian-Chukchi-Beaufort (EsCB) Seas significantly increases the frequency of winter extreme low temperature over western-central China. Autumn sea ice loss warms the troposphere and generates anticyclonic anomaly over the Arctic region 1 month later. Under the effects of synoptic eddy-mean flow interaction and anomalous upward propagated planetary wave 2, the Arctic anticyclonic anomaly strengthens and develops toward Greenland-Northern Europe, accompanied by a weakened stratospheric polar vortex. In winter, following intra-seasonal downward propagation of stratospheric anomalies, the Northern European positive geopotential height anomalies enhance and expand downstream within 7 days, favoring Arctic cold air east of Novaya Zemlya southward (the hyperpolar path) accumulating in Siberia around Lake Baikal. In the subsequent 2-3 days, these cold anomalies rapidly intrude western-central China and induce abrupt sharp cooling, thus more frequent extreme low temperature there. In contrast, the role of autumn Barents-Kara (BK) sea ice loss exhibits quite different features, mainly favoring northwestern, northeastern and eastern China to experience increased frequency of extreme low temperature in winter.