冬季西伯利亚高压的主要年际变化模态及其对东亚气温的影响

Interannual Variations of Siberian High during Boreal Winter and Its Influence on East Asian Temperature

选取40°N-60°N,80°E-120°E的区域作为西伯利亚高压的主要活动区域,利用NCEP/NCAR月均海平面气压再分析资料,对该区域西伯利亚高压(Siberian High,SH)从1979-2017年共38个冬季(12月至次年2月)进行经验正交函数分解(Empirical Orthogonal Function,EOF)。结果表明,第1模态为全区一致的变化,第2模态为南北气压的反相变化关系,第3模态为东西部气压的反相变化关系,并且3个模态的时间序列都存在显著的年际变化。进一步对相关的大气环流和东亚气温异常的分析表明,第1模态相联系的大气环流在地面表现为海陆气压差的改变,500 h Pa高度上东亚大槽强度的变化,200 h Pa纬向风场上温带急流、副热带急流强度的变化,SH负位相时,东亚偏暖,SH正位相时,东亚偏冷;第2模态与北极涛动(Arctic Oscillation,AO)和北大西洋涛动(North Atlantic Oscillation,NAO)的变化有密切关系,在高度场上表现为一个准正压的南北环状模态,SH北强南弱时,环流场类似AO正位相,温带急流减弱,东亚东北部偏暖,SH北弱南强时,东亚东北部偏冷;而与第3模态相联系的大气环流主要出现在欧亚大陆局部区域,与北大西洋涛动(NAO)也存在一定的关联,SH东强西弱时,东亚北部偏暖,西南部偏冷,SH东弱西强时,东亚北部偏冷,西南部偏暖。

The dominant interannual variations of Siberian high(SH)during Boreal Winter in north Asia region(40°N-60°N,80°E-120°E)are analyzed using empirical orthogonal function(EOF)decomposition based on NCEP/NCAR monthly mean sea level pressure data from 1979 to 2017.The results show that the first EOF mode present a uniform variation over the whole region,the second mode exhibit a north-south seesaw relationship in seal level pressure change,and the third mode show a west-east seesaw relationship.In addition,the principal component time series of the three dominant modes all indicate significant interannual changes.Further analysis of the relevant atmospheric circulation pattern and East Asian temperature anomaly associated with the first mode show that the atmospheric circulation is characterized by changes in sea-land pressure gradient and related changes in East Asian trough strength and subtropical jet intensity.When SH is in negative phase,East Asia is warmer than usual,on the contrary East Asia is colder when SH is in positive phase.The second mode of SH is closely related to changes in Arctic Oscillation(AO)and North Atlantic Oscillation(NAO),where the height field shows a quasi-positive pressure north-south annular mode.When SH is strong in the north and weak in the south,the circulation pattern is similar to the AO positive phase,weakened temperate jet stream lead to warmer condition in the northeastern part of East Asia,but when SH is weak in the south,the northeastern part of East Asia is colder.The atmospheric circulation associated with the third mode mainly occurs in the local area of Eurasia,and also has a certain relationship with the North Atlantic Oscillation(NAO).When SH is strong in the east and weak in the west,the east part of East Asia is warmer and the southwest part is colder.When SH is weak in the east and strong in the west,the northeastern part of East Asia is colder and the southwest part is warmer.