Impact of Climate Change on Reference Crop Evapotranspiration in Chuxiong City, Yunnan Province

In order to explicit the impact of climate change on reference crop evapotranspiration (ET0), using Penman-Monteith formula and the monthly meteorological data from years of 1961 to 2010 in Chuxiong City, ET0 and its two sub-items (radiation item (ETrad) and aerodynamics item (ETaero)) were calculated. Based on correlation analysis and multiple regression analysis methods, the impact of climate change on ET0, ETrad and ETaero were analyzed. The results show that in recent 50 years, the annual average temperature has increased; relative humidity and sunshine hours have declined, while the wind velocity appeared stable slight fluctuations at first, then significantly decreased and then a sudden rise and fluctuations in high-value. ETrad presented a significantly decreasing trend, while ETaero has a significantly increasing trend, and ET0 has no significant increase or decrease trend under the joint action of its two items. The order of the meteorological factors affecting ET0, from strong to weak, is annual average wind speed, sunshine hours, relative humidity and wind speed.