Abstract:

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.

Key words: Midsummer precipitation, Atmospheric circulation, Western Pacific Subtropical High (WPSH)