Research On Potential Evapotranspiration And Drought Characteristics In The Tarim River Basin

Climate change is making droughts worse,especially in areas where water is short.The Tarim River basin is located in northwest China,Its ecological environment is fragile,which makes it sensitive to environmental change.Therefore,in the background of climate change,study the characteristics of potential evaporation and drought in this region of space-time evolution law has important significance.In this paper,We used data from 40 weather stations in this region to calculate it's temperature and precipitation,and then analyzed its temporal and spatial variation characteristics.Penman-Monteith formula was used to calculate ET₀,then we analyzed it's temporal and spatial variation characteristics and understand the effects of weather factors on it.On this basis,standardized precipitation evapotranspiration index(SPEI)was used to analyze the characteristics of drought in the basin based on run theory and wavelet analysis.Finally,the global Climate Model(GCMs)output from CMIP6 is used to predict the potential evapotranspiration and drought trends in the basin.Based on the above research,we drew the following conclusions:(1)At the annual and seasonal scales,the mean temperature of the basin fluctuated at a rate of 0.411?/10a since 1970,with the fastest rising rate in spring,followed the next is winter,the rest is summer and autumn.The annual precipitation change rate is8.41mm/a,precipitation changes most rapidly in summer,the second is spring,winter is the slowest.In terms of spatial pattern,annual temperature is high in the middle and low in the periphery,precipitation is low in the center and east,and high in the north and south.The temperature change rate is higher in the north and lower in the south,and the precipitation increase rate is higher in the west and lower in the northeast.(2)In terms of interannual variation,the annual average potential evapotranspiration in the basin decreased at a rate of 0.58mm/a from 1970 to 2019,and the stage change was characterized by a decrease at first and then an increase.Among the four seasons,the potential evapotranspiration showed an increasing trend in spring and winter,and the variation of evapotranspiration in the four seasons was similar to the inter-annual variation.,and the variation of evapotranspiration in the four seasons was similar to the inter-annual variation,which decreased first and then increased.At both annual and seasonal scales,ET₀is higher in the south and east.The variation of potential evapotranspiration is affected by many meteorological factors.(3)In terms of interannual variation,annual SPEI generally showed an increasing trend from 1970 to 2019,with an increasing rate of 0.01/a,and the stage variation showed an increase first and then a decrease.In terms of spatial pattern,SPEI was lower in the east and northwest of the basin.Not only annual drought duration but also drought intensity and drought extent all showed a decreasing trend.Drought duration showed a decreasing trend in summer and autumn,but showed a increasing trend in spring and winter.The drought intensity showed a increasing trend in autumn,but decreased in the other three seasons.The area of drought increased in winter and decreased in other seasons.In terms of spatial pattern,the drought intensity is higher in the eastern,but the drought frequency is lower than in the western.(4)Under the four Shared Socioeconomic Pathways(SSP)scenarios,From2020 to 2099,air temperature,precipitation and potential evapotranspiration showed an increasing trend,while SPEI showed a trend of decreasing.In terms of spatial distribution,the increase range of precipitation gradually decreased from southwest to northeast,while the average temperature gradually increased from southwest to northeast.The increase rate of potential evapotranspiration in northeast China was generally higher than that in southwest China,and gradually increased from southwest to northeast China.The variation range of SPEI under SSP5-8.5 was larger than that under other scenarios,and drought was the most serious.