Study on change of relative humidity in semiarid region under global climate change

To reveal the semiarid regions of the air relative humidity changes under global climate change,linear regression analysis,multiple linear correlation analysis,and the Mann-Kendall test are used to study on the relative humidity,temperature,precipitation and wind speed data of the five sites in the western Jilin Province from 1953 to 2002.The results show that:the past 50 years,change trend of the annual average and seasonal relative humidity is fluctuant decreasing,and it is not significant;however,in September and October,change trend of the average relative humidity is significant decreasing.The changes of the relative humidity is the double-peak curve type in a year,the maximum relative humidity is in the August,the second largest relative humidity is in the January,the minimum appears in the April,and the smaller one is in October.The relative humidity of the summer and autumn is higher,but the relative humidity of the spring and winter is smaller.Changes of the temperature and precipitation are the main factor to relative humidity change,and the wind speed also plays certain role.Changes of temperature and wind speed are positive correlated with relative humidity change and change of precipitation is negative correlated with relative humidity change.