Abstract:Adaptation evaluation for reference evapotranspiration (ET0) methods can obtain simplified calculation methods of ET0 under the conditions of lacking meteorological data and increase the accuracy with the lack of meteorological data in the large area. To obtain the best calculation methods and assess its adaptability, Yunnan Province was divided into three regions, including the mountain plateau and high mountain water abundance region in western and southwestern of Yunnan ([KG-*4]Ⅰ[KG-*4]), the mountain plateau and river valley water middle region in northwestern and northeastern of Yunnan ([KG-*4]Ⅱ[KG-*4]) and the plateau water middle and shortage region in central and northern of Yunnan ([KG-*4]Ⅲ[KG-*4]), and the daily ET0 was calculated in 36 stations from 1958 to 2013. Ten kinds of methods, such as FAO 56 Penman—Monteith, Hargreaves—Samani, Irmark—Allen, Pristley—Taylor, Makkink, 1948 Penman, Penman—Van Bavel, Turc, FAO 24 Radiation and Jensen—Haise, were used to calculate the daily ET0 of each station of Yunnan Province. Penman—Monteith method was used as the standard method to calculate the daily ET0 because of its accuracy, and the precision of other methods was evaluated by the linear regression coefficient, the daily relative root mean square error, the mean bias error and the coefficient of Nash—Sutcliffe. The results showed that 1948—Penman method had the strongest applicability and the highest calculation accuracy, and Radiation FAO 24 method and Jensen—Haise method had large error. Among all the methods, Hargreaves—Samani method was the best one in region Ⅰ, and 1948—Penman method was the most appropriate from January to June while Priestley—Taylor method was the most suitable from July to December of each year for regions Ⅱ and Ⅲ. In the spatial distribution of relative error, the relative error of Hargreaves—Samani method, Irmark—Allen method and Priestley—Taylor method was below 20%, so the three methods were appropriate for region I, and the relative error of Priestley—Taylor method and 1948—Penman method was in the range of 0~20%, as the minimum in regions Ⅱ and Ⅲ, and the relative error of Irmark—Allen method was small in region Ⅱ. When reference crop evapotranspiration was calculated in Yunnan Province, as a consequence, 1948—Penman method was recommended in the whole region, Hargreaves—Saman method was recommended in mountain plateau and high mountain water abundance region in western and southwestern of Yunnan, Priestley—Taylor method was recommended in mountain plateau and river valley water middle region in northwestern and northeastern of Yunnan.
