Temporal-spatial Distributions and Recent Changes of Precipitation in the Northern Slopes of the Qilian Mountains
Zhu Shousen and Wang Qiang(Lanzhou Institute of Glaciology and Geocryology, Chinese Academy of Sciences, 730000)
Analysis of temporal-spatial distributions of annual precipitation in northern slopes of the Qilian Mountains indicates that the annual precipitation has a relationship with altitude expressed by a non-linear equation, that is, Y = A+BIln(X), where X is altitude (m), Y is precipitation (mm), and A and B are constants. It also indicates that the annual precipitation increases with altitude, and the annual precipitation decreases from east to west of the mountains. However, changes of precipitation with altitude are not identical. Two zones, one of which lies at 2 000 m a.s.l. and another is at above 4 000 m a.s.l., have higher increase rates of precipitation. Analysis of recent changes in annual precipitation shows that there are a positive anomaly period and a negative anomaly period in the mountainous areas in recent 40 years, while two positive and two negative anomaly periods in the piedmont plain areas in recent 50 years.