2021/2022年东亚大陆冬季前暖后冷的环流差异及其成因

Atmospheric circulation difference between warm in early winter and cold in late winter of 2021/2022 over East Asia continent and its causes

2021/2022年冬季东亚大陆地区整体以偏冷为主,气温季节内变化显著,前冬(2021年12月1日—2022年1月26日)气温偏高,后冬(2022年1月28日—2月24日)气温偏低;气温变化的空间差异较大,呈现出显著的北暖南冷特征,尤其在冷时段,南部地区气温偏低幅度比北部地区大1℃左右.本文利用逐日中国观测站点资料和NCEP/NCAR、ERA5等再分析资料分析了2021/2022年冬季东亚大陆前暖后冷的可能原因,发现与冬季气候密切相关的西伯利亚高压、东亚冬季风、平流层极涡、高原高度场、西太平洋副热带高压、东亚高空西风急流、北半球平流层环状模(NAM)等大尺度环流系统均发生了显著的转折性变化,直接导致了东亚大陆冬季前暖后冷的季节变化,但乌拉尔山高压在冷暖时段的变化差异并不明显.另外,赤道中东太平洋冷海温和北大西洋暖海温在后冬的加强变化通过对大气环流的强迫影响,对2022/2021年后冬冷时段冷空气的加强和低温冷事件的发生起到了十分重要的作用.

The surface air temperature(SAT)in East Asia continent was lower than normal in winter 2021/2022,but it displayed significantly intraseasonal variability with warmer in early winter(from December 1,2021 to January 26,2022)and cooler in late winter(from January 28 to February 24,2022).Moreover,the spatial distribution of SAT anomalies showed a characteristics of northern warm and southern cold over East Asia continent.Especially,the SAT anomaly in the southern region was approximate 1℃lower than that in the northern region during in the cold period.In this study,the differences of atmospheric circulation and their possible reasons in winter 2021/2022 are investigated based on the daily station data from CMA and atmospheric reanalysis data from NCEP/NCAR and ERA5.The results show that the SAT variability over East Asia continent is closely related to some key atmospheric circulation systems,including the Siberian high(SH),the East Asian winter monsoon(EAWM),the stratospheric polar vortex,the geopotential height(GHT)in plateau,the Western Pacific subtropical high(WPSH),the westerly jet at upper troposphere in East Asia,and the northern hemisphere annular model(NAM)at stratosphere.The transitional changes of the above atmospheric circulation systems are mainly responsible for the transition from cold to warm in East Asia continent in winter 2021/2022.It should be mentioned that the difference of the Ural Mountain high(UH)between the warm and cold period is no significant.In addition,the cold sea surface temperature(SST)in the tropical central-eastern Pacific and the warm SST in the North Atlantic play a very important role in the strengthening of cold wave and the occurrence of cold events through the forced influence on the atmospheric circulation during cold period in winter 2022/2021.