吉林省盛夏降水季内变化特征及大气环流分析

利用1961—2017年吉林省46个地面气象观测站点降水月数据及NCEP/NCAR全球月平均位势高度场、风场再分析资料，采用EOF、SEOF、滑动相关、回归分析及合成分析等方法研究了近57 a吉林省盛夏7月、8月降水的基本特征，季内差异及其大气环流异常特征。结果表明：吉林省盛夏7月、8月降水在空间上以全区一致型为主，整个吉林省均表现为正（负）异常；吉林省7月、8月降水在1986—2004年基本呈现反位相变化，即7月多（少），8月少（多）；2005—2017年两个月份呈现同位相变化，即7月少（多），8月少（多）；反位相年中7月降水与北美东西遥相关（NAEW）及东亚太平洋相关（EAP）有关，8月降水与欧亚遥相关（EU）有关，同位相年中7月、8月降水与副热带高压强度和位置异常有关；吉林省盛夏降水同西太平洋副热带高压有着密切关系，反位相年高、低值年副热带高压的东西位置差异显著，同位相年期间副热带高压异常西伸北进、面积增大。

Seasonal variation of midsummer precipitation anomaly in Jilin province and its related atmospheric circulation characteristics

Based on the average monthly precipitation data from 46 meteorological stations in Jilin province and the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) monthly reanalysis data, the seasonal variation of midsummer precipitation in Jilin province and its atmospheric circulation characteristics during recent 57 years were studied using the methods such as empirical orthogonal function (EOF), season-reliant EOF (SEOF), sliding correlation, regression analysis and compose analysis.The results show that the spatial pattern of precipitation in July and August is mainly consistent across the whole region.The whole region shows a positive (negative) anomaly.From 1986 to 2004, the precipitation in July and August in Jilin province demonstrates an anti-phase change, that is, more (less) in July and less (more) in August.During 2005-2017, the precipitation in July and August shows the same phase change.For out-of-phase years, the circulation anomaly is mainly related to the North American East/West (NAEW) and East Asian/Pacific (EAP) in July, while it is related to the Eurasian (EU) teleconnection pattern in August.For in-of-phase years, the pattern of circulation anomaly is similar to the position variation and intensity of the Western Pacific Subtropical High (WPSH).Meanwhile, it is closely related the variation of the WPSH in July and August and the intraseasonal variation.In out-of-phase years, there is a significant difference in the WPSH east-west position between the high-value year and the low-value year.For in-of-phase years, the WPSH anomaly extends westward and northward.