Abstract:  Based on the monthly mean air temperature and precipitation from 71 meteorological stations in Northeast China from 1961 to 2009, the drought tendency from May to September were analyzed using standardized precipitation index (SPI) and relative moisture index. The results indicate that the drought tendency from May to September is obvious in most of Northeast China regions except in the north of Daxing’anling region, in the southwest of Heilongjiang province and in the boundary between the east of Jinlin province and Heilongjiang province. The phenomena of drought and moisture alternations exists periodic oscillations with a cycle of 22-24 years in Northeast China. There are four drought and moisture alternations in the recent 49 years, and abrupt changes appeared in 1976 and 1996. Meanwhile, drought areas in Northeast China are in an increasing trend in the recent 49 years in terms of drought ranges. Compared with the drought situation before 1996, the increasing amplitude of affected crop area for drought disaster is the largest in Jilin province after 1996, then in Liaoning province, and the smallest in Heilongjiang province. It is more realistic to use SPI and relative moisture index as the drought assessment index in Northeast China. In terms of drought frequency, the area with large values concentrates in the west of Northeast China, especially in Qiqihar and Daqing in Heilongjiang province, Baicheng in Jilin province and Chaoyang in Liaoning province. The frequency of drought and extreme drought is lower from 1981 to 1990 and higher from 2001 to 2009, and the frequency of increased amplitude of extreme drought is higher than that of the normal drought.

Key words: Standardized precipitation index (SPI), Relative moisture index, Drought tendency, Northeast China region