2020/2021年冬季中国北方一次寒潮天气过程与北极增暖的可能联系
Possible Link between a Cold Wave Weather Process in Northern China during the Winter of 2020/2021 and Arctic Warming

2020年12月29日~2021年1月7日，华北、华东和中南北部出现了寒潮天气过程和入冬以来的气温新低，多个机场出现大风和降雪天气，对运行产生了一定影响。寒潮发生时，对流层中层乌拉尔山阻塞高压偏强，贝加尔湖以东横槽维持，对流层低层西伯利亚高压和阿留申低压均偏强，以上环流形势均有利于引导高纬度冷空气向南输送。当东亚偏冷时，北极地区却呈现明显暖异常，当北极偏暖发生时，中高纬度阻塞高压容易增强，同时使西伯利亚高压增强，进一步导致寒潮发生；此外，“北正南负”的厚度异常形势使北半球中高纬厚度经向梯度减小，减小的厚度经向梯度导致欧亚大陆中纬度地区纬向西风变弱，减弱的纬向西风使东亚大槽和欧亚阻塞高压增强，即欧亚大陆中高纬环流的经向气压梯度增大，便于冷空气向南输送，有利于寒潮发生。
From December 29, 2020, to January 7, 2021, a cold wave weather process occurred in North China, East China, and the central and southern parts of China, with the lowest temperatures since the beginning of winter. Strong winds and snowfall occurred at many airports, which had a certain impact on operations. When the cold wave occurred, the Ural blocking high in the middle troposphere was relatively strong, the transverse trough east of Lake Baikal persisted, and both the Siberian high and the Aleutian low in the lower troposphere were relatively strong. The above circulation patterns were all conducive to guiding the cold air from high latitudes to move southward. When East Asia was relatively cold, the Arctic region showed an obvious warm anomaly. When the Arctic warming occurred, the blocking high in the mid-high latitudes was likely to intensify, and at the same time, the Siberian high was strengthened, further leading to the occurrence of the cold wave. In addition, the thickness anomaly pattern of “positive in the north and negative in the south” reduced the meridional gradient of the thickness in the mid-high latitudes of the Northern Hemisphere. The reduced meridional gradient of the thickness led to the weakening of the westerly winds in the mid-latitudes of Eurasia. The weakened westerly winds enhanced the East Asian trough and the Eurasian blocking high, that is, the meridional pressure gradient of the mid-high latitude circulation in Eurasia increased, which facilitated the southward transport of cold air and was conducive to the occurrence of the cold wave.