Abstract: This study was based on the daily observation data of 19 meteorological stations in the Tarim basin during the crop growing season from 2000 to 2019. The FAO-56PM formula was used to calculate the daily ET0 of each station. The sensitivity coefficient, ArcGIS inverse distance weight interpolation, climate trend rate and Mann-Kendall nonparametric test were used to analyze the spatiotemporal variation and the sensitivity of ET0 to key meteorological factors. The results indicate that: (1) during the past 20 years, the daily mean values of ET0 in the crop growing season are generally lower in the north and higher in the south of the Tarim basin. The daily mean values of ET0 in the crop growing season were 5.84mm⋅d⁻¹ in June, 5.73mm⋅d⁻¹ in July, 5.29mm⋅d⁻¹ in May, 4.95mm⋅d⁻¹ in August, 4.23mm⋅d⁻¹ in April, 3.65mm⋅d⁻¹ in September and 2.17 mm⋅d⁻¹ in October, respectively. The climate tendency rates of the daily mean value of ET0 were −0.09, 0.24, 0.11, −0.07, 0.16, 0.07 and 0.08mm⋅10y⁻¹, respectively. These rates were dominated by negative dip rates in the middle and west of the basin, and positive dip rates in the east of the basin; (2) During the crop growing season, relative humidity increased and wind speed at 2m decreased by each month. Sunshine duration firstly increased and then decreased. Minimum temperature and maximum temperature showed an inverted U-shaped distribution, and both reached their maximum values in July. The change of relative humidity was dominated by negative trend rates. The change of wind speed at 2m and minimum temperature were dominated by positive trend rates, while the trend rate of sunshine duration and maximum temperature had no obvious trend; and (3) During the crop growing season, the sensitivity of ET0 to the key meteorological factors in the Tarim basin were: maximum temperature > relative humidity > sunshine duration > wind speed at 2m > minimum temperature. The sensitivity of ET0 to the minimum temperature was negligible, while the sensitivity to other meteorological factors were high. ET0 is most sensitive in July to the minimum and maximum temperature, while most sensitive in October to relative humidity, in April to wind speed at 2m and in August to sunshine duration, respectively. The spatial distribution of absolute values of ET0 sensitivity coefficient to relative humidity decreased from north to south. The sensitivity coefficient to wind speed at 2m and maximum temperature were the highest in the center of the Taklimakan Desert. There is no obvious trend of sunshine duration. The minimum temperature decreased from west to east of the basin.

Key words: The Tarim basin, Reference crop evapotranspiration, Penman-Monteith equation, Spatiotemporal variation, Sensitive analysis