Analysis Of Interdecadal And Interannual Variations Of Summer Rainfall Anomaly In Northeast China And Its Mechanism

The temporal and spatial variations of summer precipitation anomaly in Northeast China(NESPA) are studied, and its relations with contemporary circulation anomalies over North Pacific(NP) and SST departure of Pacific on the interdecadal and interannual scale are discussed by means of harmonic analysis, REOF and SVD. The results show that: 1) NESPA is no visible relation to precipitation in other areas of China (besides east of North China), so it is worth researching as alone region. 2) In the recent 50 years, wetting or drying trend isn't obvious, while alternate flood/drought features exist. The importance of the interdecadal variation is similarly equal to that of interannual change in NESPA variance constitution. 3) NESPA is divided into 6 regions, and interdecadal variation is more significant in southeast than in northwest area. 4) During either interdecadal or interannual period, the strong(weak) stage of the North-east Asian summer monsoon(NEASM) is with respect to the positive(negative) phase of NESPA. In addition, NP subtropical high is closely related to NESPA at the interannual scale. 5) Interdecadally, with lower and higher SST in the middle of NP and tropical east Pacific(TP) respectively, NEASM becomes weak, and vice versa. Interannually, with lower and higher SST in the middle of NP and TP respectively, NP subtropical high becomes weak and is on the southern side of normal, and vice versa.