北极高压通过阻塞高压对中国冬季冷空气的影响

The influence of the Arctic High on winter cold air in China

利用二维阻塞高压指数和人工识别方法对1979-2020年冬季欧亚地区的阻塞高压单独出现和伴有北极高压同时出现的事件进行研究,分析阻塞事件中北极高压的基本特征及其对中国冬季冷空气的影响.结果表明,当北极高压与阻塞高压同时出现并同位相连通时,高压中心主要位于新地岛附近,乌拉尔山地区发生的阻塞事件较贝加尔湖地区更多;阻塞高压事件的发生频次在1月最高,在1990s明显少于其他年代.21世纪以来,总阻塞事件中伴有北极高压的比例大幅提高,约为40%.北极高压通过阻塞高压影响中国冬季冷空气时,欧亚地区的对流层为高纬度异常增暖、中纬度异常偏冷的空间分布;中纬度地区西风减弱而副热带急流加强,反气旋式Rossby波破碎的发生增强了欧亚地区的位涡环流,北极高压得以维持和发展,在500 hPa形成较稳定的“两槽一脊”流型,高压中心位置偏北且较强.该环流形势有利于地面西伯利亚高压的生成和发展,其位置偏北、偏东,影响范围较大,冷空气以偏东路径侵入中国,使东北地区较早受到影响.

Based on the two-dimensional indices of atmospheric blocking and manual identification method,the events of the blocking high(BH) alone and BH together with the Arctic High(AH) in the Eurasian region in the winter of 1979-2020 were studied.And the basic characteristics of AH in blocking events and its influence on cold air in winter in China were analyzed.The results showed that,when AH was connected with BH,the high pressure center was mainly located near Novaya Zemlya,and there were more blocking events in the Ural Mountains than in the Baikal Lake.The frequency of blocking events was the highest in January,and significantly lower in the 1990s than in other decades.Since beginning of the 21st century,the proportion of total blocking events accompanied by AH had increased significantly,by about 40%.When AH affected the winter cold air in China through BH,the troposphere in Eurasia was abnormally warm in high latitudes and abnormally cold in mid-latitudes.The westerly wind in the mid-latitude region weakened and the subtropical jet strengthened.The occurrence of the anticyclonic Rossby wave breaking enhanced the potential vorticity circulation in Eurasia,and AH was maintained and developed.A relatively stable"two troughs and one ridge"flow pattern was formed at 500 hPa,and the center of the high pressure was northerly and stronger.This circulation was conducive to the formation and development of surface Siberian high,which was located north and east,and the influence range was large.The cold air invaded China in an east path and the northeast region was affected earlier.