The Basic Characteristics Of Precipitation Over Northeast China And Its Relationship With Atmosphere And SST In The Pacific

Northeast China(NEC) is China’s major grain production bases, and summer is the main growing season of crops in NEC, precipitation is also concentrated in this season. So we think precipitation and its distribution is one of the factors that affect food production in NEC. In this paper we use the daily precipitation data of122stations in NEC, the NCEP/NCAR reanalyzed grid data and the NOAA monthly sea surface temperature data, all these data are all from1961to2010. With climatological statistics analysis and variability diagnosis methods of Empirical Orthogonal Function (EOF), Singular Value Decomposition (SVD), composite analysis and linear correlation analysis, the basic characteristics of summer precipitation over NEC were investigated through a month-to-month analysis from June to August, and the type of precipitation in NEC are studied. On that basis, the relationship between different rainfall pattern and atmosphere circulation, sea surface temperature in the north Pacific over the same period and the previous winter and spring are discussed. The conclusions are as follows:(1) In June, July and August, the precipitation of the NEC can be divided into two categories and four small classes, precipitation of NEC can be divided into consistent rainfall pattern (more rainfall pattern, less rainfall pattern) and south-north anti-phase rainfall pattern (southern rainfall pattern, northern rainfall pattern) in June and August, while divided into consistent rainfall pattern(more rainfall pattern, less rainfall pattern) and east-west anti-phase rainfall pattern (eastern rainfall pattern, western rainfall pattern) in July.(2) There are significantly different distribution characteristics for different rainfall pattern of each month (June, July and August). The precipitation of NEC in June are mainly affected by the Northeast Cold Vortex, which is positively correlated with precipitation over NEC, especially the precipitation in the northern of NEC. The south-north anti-phase rainfall pattern is closely related to the abnormal of the Okhotsk blocking high; as the location of Western Pacific Subtropical High is to the west and north, the precipitation appeared to increase in July and August. The wave train transmitted along the upper westerly jet stream mainly causes the precipitation over the entire NEC in July and August to be much more. And the appearance of EAP pattern suggest that east-west anti-phase rainfall pattern will occur in July and south-north anti-phase rainfall pattern will occur in August. Notably, the east-west anti-phase rainfall pattern is more likely to occur in July while the consistent rainfall pattern is more likely to appear in August.(3) Through the analysis of the relationship between precipitation for different rainfall patterns over each month and the north Pacific SST, We can draw the following conclusions. When the rainfall over the entire northeast is under(above) normal in June, the SST of the Gulf of Alaska is warm(cold) anomaly, and this cold anomaly continues to decline from early winter to early spring; When there is more (less) rainfall in the west and less (more) rainfall in the east of NEC, the SST of Yellow Sea, Bohai Sea China and the Kuroshio Extension sea temperature is cold (warm) anomaly, and the intensity of this cold (warm) anomaly has been strengthened from early winter to early spring. In July, when La Nina (El Nino) signals appear in the equatorial Pacific, there will be more rainfall over entire Northeast in the following year of July. On the other hand, when the Western Pacific sea’s cold (warm) water phase gradually strengthen from early winter to early spring, there will be more rainfall in the west (east) of the Northeast China in the next year of July. In August, there will be more rainfall over the entire Northeast when the equator Middle East Pacific warm (cold) water phase decreased. And there will be more rainfall in the North (South) of the Northeast China when the SST of the equator Middle East Pacific changes from cold (warm) anomaly to warm (cold) anomaly as the season transform from early winter to early spring.