Analysis on Spatial-temporal Variation Characteristics of the Precipitation in Four Provinces of the Northwest China

[Objective] The research aimed to analyze temporal-spatial change characteristics of the precipitation in four provinces of the Northwest China.[Method] Based on precipitation data at 113 ground observation stations in four provinces(Shaanxi,Gansu,Qinghai and Ningxia) of the Northwest China from 1961 to 2008,by using linear regression and Morlet wavelet transformation,spatial pattern change,change trend and period characteristic of the precipitation in the zone in 48 years were analyzed.[Result] Rainfall in four provinces of the Northwest China had obvious interannual and seasonal change characteristics.Annual,spring and autumn rainfalls all presented decline trends.Summer and winter rainfalls both had slight increase trends,but change trend wasn't obvious.Precipitation change in four provinces of the Northwest China had obvious regional difference.Increase amplitudes in Tanggula Mountains,Tsaidam Basin and east Qilian Mountains were obvious.Obvious decrease amplitudes existed in east Sichuan and south and north Shaanxi.Precipitation in east and west areas of the four provinces in Northwest China presented anti-phased change characteristics.Precipitation presented decrease trend in east and increase trend in most areas of west.Precipitation in the whole district,east district and west district generally had 3-5-year short period.It was main period.Precipitation also had 8-year and 15-year medium periods in some areas.Under different time scales,dry and wet alteration and mutation point had difference.[Conclusion] The research provided theoretical basis for climate change in Northwest China.