Climate change trend and its effects on reference evapotranspiration at Linhe Station, Hetao Irrigation District

Linhe National Meteorological Station, a representative weather station in the Hetao Irrigation District of China, was selected as the research site for the present study. Changes in climatic variables and reference evapotranspiration（ET;）(estimated by the Penman-Monteith method) were detected using Mann-Kendall tests and Sen’s slope estimator, respectively. The authors analyzed the relationship between the ET;change and each climatic variable’s change. From 1954 to 2012, the air temperature showed a significant increasing trend, whereas relative humidity and wind speed decreased dramatically. These changes resulted in a slight increase in ET;. The radiative component of total ET;increased from 50% to 57%, indicating that this component made a greater contribution to the increase in total ET;than the aerodynamic component, especially during the crop growing season（from April to October）. The sensitivity analysis showed that ET;in Hetao is most sensitive to mean daily air temperature（11.8%）, followed by wind speed（-7.3%） and relative humidity（4.8%）. Changes in sunshine duration had only a minor effect on ET;over the past 59 years.