Precipitation characteristics in Flood season in Shanxi Province

Based on observed daily precipitation data of 65 observation stations in Shanxi from 1960 to 2005,variable characteristics of precipitation and daily storm rainfall in main flood season were analysised.Results showed that mail flood season of Shanxi Province is from the first 10 days of July to the middle of August.Mean annual variable trend is in the range of 0.1mm--30mm every 10a.Main flood season precipitation of Shanxi is still decreasing,but frequency of storm is raising after the 21 century.Main flood season precipitation of Shanxi and occurrence of rain storm show positive correlation with the strength of monsoon.The correlation analysis of main flood season precipitation and 500hPa geopotential height of July and August show that when west pacific ocean subtropical anticyclone is strong the precipitation in the region between lake Bai and Inner Mongolia is abnormal lack,and when middle latitude circulation appears high,main flood season precipitation in east and low west Shanxi is abundant.