Abstract
A persistent strong cold surge occurred in East Asia in late January 2018, causing mean near-surface air temperature in China to hit the second lowest since 1984. Moreover, the daily mean air temperature remained persistently negative for more than 20 days. Here, we find that a synergistic effect of double blockings in Western Europe and North America plays an important accelerating role in the rapid phase transition of Arctic Oscillation and an amplifying role in the strength of cold air preceding to the cold surge outbreaks by the use of an isentropic potential vorticity analysis. In mid-January, an Atlantic mid-latitude anticyclone merged with Western Europe blocking, which led to a strengthening of the blocking. Simultaneously, the Pacific-North American blocking was also significantly strengthened. The two blockings synchronously deeply stretched towards the Arctic, which resulted in, on the one hand, warm and moist air of the Pacific and the Atlantic being excessively transported into the Arctic, and on the other hand, the polar vortex being split and cold air being squeezed southwards and accumulating extensively on the West Siberian Plain. After the breakdown of the double blocking pattern, which lasted for about 10 days, the record-breaking cold surge broke out in East Asia. It was discovered that the synergistic effect of double blockings extending into the Arctic, which is conducive to extreme cold events, has been rapidly increasing in recent years.
Highlights
In the context of global warming, Arctic temperatures have increased rapidly and Arctic sea ice continues to melt [1,2,3]
It was discovered that the synergistic effect of double blockings extending into the Arctic, which is conducive to extreme cold events, has been rapidly increasing in recent years
When the Ural blocking shows a quasi-steady characteristic, cold air is continuously conveyed to the mid-latitude continent under the guidance of the blocking, which is conducive to cold extremes in Eurasia [21,22,23]
Summary
In the context of global warming, Arctic temperatures have increased rapidly and Arctic sea ice continues to melt [1,2,3]. The frequency of extreme cold in the mid-latitudes of the northern hemisphere is increasing, especially in Eurasia [4,5,6]. The main reasons for cold extremes in Eurasia are reported as Arctic circulation changes (such as Arctic Oscillation (AO)) [7,8], sea ice melting [9,10,11,12], Arctic warming [6,13,14,15], tropical driving [16], and Eurasian snow cover anomalies [7,17,18].
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