Climatic Characteristics of Rainfall and Rainy Days during the Last 35 Years over the Qinghai-Xizang Plateau

By using the daily rainy days and rainfall data of 49 stations in 1971-2005 over the Qinghai-Xizang Plateau,the trends of the annual and seasonal rainfall and rainy days are analyzed.The result shows that the trend of the annual rainfall and rainy days increases remarkably in most parts of Tibet,but the trend decreases in most parts of Qinghai.The rainy days are decreasing and the rainfall is increasing in summer half year over the Qinghai-Xizang Plateau,which indicates that the rainfall is centralizing more and more and the rainy intensity has increased.In winter half year,the rainy days and rainfall increase.In summer half year,the spit(0.1-4.9 mm) rainy days decrease,but the rainfall increases.And the rainy days and rainfall of spit and moderate rain(5.0-9.9 mm) increase,the rainy days and rainfall of heavy rain decrease.In winter half year,the rainy days and rainfall of light snow,moderate snow and heavy snow have an increasing trend,while the trend of storm is not obvious.