Spatiotemporal pattern change of precipitation in Qinghai in the last 50 years

The variation characteristics and trend of annual and monthly precipitation in the past 50 years were analyzed based on the monthly precipitation of 32 stations during 1961-2010 in Qinghai province by using methods of linear trend analysis,Anomaly analysis and Mann-Kendall.The periodic oscillation and spatial distribution characteristics of precipitation variations were revealed by using power spectrum and GIS.The results showed that the variation trend of annual precipitation was slightly increasing in Qinghai during the 50 years,linear trend rate was 3.3 mm/(10a).The precipitation was mainly concentrated from May to September in the year,accounting for 86.1%,and the changes of positive and negative anomaly were also relatively large.It indicated that the decadal precipitation had obvious periodicity,and precipitation increased obviously in the 21st century.It revealed that annual and seasonal precipitation(except the winter) were on the rise in the past 20 years using Mann-Kendall method.The precipitation of Qinghai was under the distribution of north and west regions lack of precipitation while south and east regions abundant,and most of the region,linear trend rate of precipitation was above 1.5mm/(10a).Analysis of power spectrum showed that the quasi-periodic oscillation of precipitation was 2 years and 3-4 years.