RESEARCH ON THE FEATURES OF SUMMER RAINFALL IN NORTHEAST CHINA

By using the monthly averaged upper-air reanalysis data of NCEP and the monthly precipitation data of 160 stations over China, analysis is made on the summer circulation and rainfall patterns in Northeast China. The results indicate that there exists obvious difference in circulation between wet and dry years in Northeast China in summer and the circulation pattern of the summer in 1998 was similar to that of the wet year. The development of the Okhotsk blocking high was the main reason of the heavy precipitation in the Songhuajiang River and the Nenjiang River basins. The enhancement of moisture flux convergence in lower layers of troposphere is a favorable condition for rainfall in Northeast China. It is also found that there exists closely positive correlation between the polar vortex intensity index in December or winter and the precipitation in Northwest China in the subsequent August or summer, which can be regarded as a signal for the precipitation in Northeast China.