Analysis of precipitation and potential evapotranspiration in arid and semi arid area of China in recent 50 years

Based on the daily air temperature,air pressure,precipitation and other weather data of 169 weather stations in arid and semi arid area of China in recent 50 years,the annual precipitation and annual potential evapotranspiration of the growing season as well as the difference of them were calculated in this paper.The spatial variation,climate change,decadal variability,and the MK mutation testing were discussed.The results showed that overall,the differences of climate change between east part and west part of the arid and semi arid area of China in recent 50 years was significant.The precipitation was increasing while the potential evapotranspiration was reducing in northwest of China.The degree of drought and its change were very significant.The precipitation was reducing while the potential evapotranspiration was increasing in east of the arid and semi arid area of China,so was the degree of drought,but its change was not obvious.