Changes in Precipitation in Northwest China Over the Last 54 Years

In this study,the changes in the precipitation anomaly,rain days and precipitation intensity in northwest China over the last 54 years were calculated and analyzed using the daily precipitation data observed at 166 meteorological stations in 5 provinces in northwest China.The results of the study were as follows:(1) Annual precipitation in northwest China has been decreasing for the last 54 years,but its positive anomaly years are almost equal to its negative anomaly years.The range of inter-annual precipitation change is high,the annual rain days are obviously reduced,and the precipitation intensity is increasing slightly;(2) Spring precipitation is in an increasing trend,its positive anomaly years are fewer than its negative anomaly years,and both rain days and precipitation intensity are in an increasing trend;(3) The change in summer precipitation is not distinct,its positive anomaly years are almost equal to its negative anomaly years,and the changes in rain days and precipitation intensity during summer are similar to the annual changes;(4) Autumn precipitation is in a distinct decreasing trend,its positive anomaly years are fewer than its negative anomaly years,the rain days are obviously decreased,and the precipitation intensity is in a slight increasing trend;(5) Winter precipitation is obviously increased,its positive anomaly years are fewer than its negative anomaly years,the number of rain or snowy days are slightly increased,and the precipitation intensity is in an increasing trend.