Abstract: The values of spring East Asia north wind index were calculated based on the data of NCEP/NCAR reanalyzed monthly 500-hPa height field during the period from 1961 to 2010 and of monthly precipitation at 170 meteorological stations in Qinghai, Gansu and Shaanxi provinces and NingxiaHui Autonomous Region in the eastern region of northwest China. The history change of spring precipitation and the relationship between the decadal variation of East Asia north wind index and the spring precipitation in northwest China were analyzed. The results showed that, bordered by the Yellow River, precipitation was in an increase trend in the regions west from the Yellow River but a decrease trend in the regions east from the river. The precipitation decrease amplitude was significantly higher than the increase amplitude. Especially in recent 20 years, the precipitation decrease was more and more significant in the vast region east from the Yellow River, and the drought trend was obvious. Precipitation, however, was in an increased trend in south Qinghai Province and the Hexi Corridor in Gansu Province. The spring East Asia north wind increased gradually during this period, especially after the mid1990s. Further analysis showed that, when the spring East Asia north wind was strong, precipitation was decreased in most areas of the eastern region of northwest China except in south Qinghai Province. So it could be concluded that the abnormal strong spring East Asia north wind could cause a decrease of precipitation and an aggravation of drought in the regions east from the Yellow River.

Key words: northwest China, spring precipitation, drought trend, East Asia north wind index, correlation analysis