Abstract: In this study, the values of reference daily crop evapotranspiration were calculated using the PenmanMonteith model based on the daily meteorological data observed by 7 meteorological stations on the east and west sides of the Liupanshan Mountain in Pingliang City, Gansu Province during the period from 1965 to 2010. The seasonal and annual values of reference crop evapotranspiration were analyzed using the MannKendall nonparametric method. The results are as follows: ① The average of reference crop evapotranspiration in Pingliang City varied in a range of 890-1 142 mm during the period of 1965-2010. The minimum occurred in the southeast and the maximum in the east of Pingliang City. The maximum value of reference crop evapotranspiration in Pingliang occurred in summer, it was followed by that in spring and autumn, and the minimum occurred in winter; ② The annual reference crop evapotranspiration was significantly decreased at most meteorological stations in Pingliang in last 46 years; ③ Wind speed and sunshine duration were the main climatic factors affecting the seasonal change of reference crop evapotranspiration in Pingliang, especially wind speed.

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