山西省秋季降水的时空变化特征及成因分析

Analysis of Spatial-temporal Variation Characteristics and Causes of Precipitation over Shanxi Province in Autumn

利用山西省1961-2021年秋季降水资料、NCEP/NCAR再分析资料和海温资料,分析山西省秋季降水的时空变化特征。结果表明:山西省秋季降水在20世纪70年代中期前偏多,之后减少,21世纪00年代中期又开始增多。进一步从大气环流角度探讨这种年代际变化的成因可知,在降水偏多时期,200 hPa纬向风场东亚西风急流位置偏北,有利于山西地区上升运动增强;500 hPa位势高度场上欧亚大陆上空呈现出显著的正-负-正异常分布,有利于高纬冷空气向南爆发;850 hPa风场有利于低纬水汽向山西输送,在这样的高低空环流配置下,有利于山西省降水增加。同时山西省秋季降水量与海温异常存在密切关系,当前期3-5月北太平洋中部海温偏高,热带中东太平洋海温偏低时,山西省南部秋季降水易偏多。

Based on autumn precipitation data from 1961 to 2021 in Shanxi Province,NCEP/NCAR reanalysis data,and sea surface temperature data,the spatial-temporal variation characteristics and cause diagnosis of autumn precipitation in Shanxi Province were analyzed and discussed by using EOF analysis,correlation analysis and regression analysis.The results show that the autumn precipitation in Shanxi Province was relatively high before the mid-1970s,but decreased afterwards,and began to increase again in the mid-2000s.Further exploration of the causes of this interdecadal variation from the perspective of atmospheric circulation reveals that,during periods of excessive precipitation,the 200 hPa latitudinal wind field is located in the north of the East Asian westerly jet,which is beneficial for enhancing the upward movement in Shanxi;The 500 hPa geopotential height field exhibits a significant“+-+”anomaly distribution in the Europe and Asia region,which is conducive to the southward eruption of high latitude cold air;The 850 hPa wind field is conducive to the transport of low latitude water vapor to Shanxi,and under such high and low altitude circulation configuration,it is conducive to an increase in precipitation in Shanxi.At the same time,there is a close relationship between autumn precipitation and sea surface temperature anomaly in Shanxi.When the sea surface temperature in the central North Pacific is higher and in the tropical Middle East Pacific is lower from March to May,the autumn precipitation in the southern part of Shanxi is prone to behigher.