The study on influence factors of hanjiang river basin of reference crop evapotranspiration change and its spatio-temporal change

Based on the daily meteorological data of 12 meteorological stations in Hanjiang River Basin from 1961 to 2013, Penman-Monteith formula is used to calculate the reference crop evapotranspiration (ET0), and the spatial characteristics of ET0 in Hanjiang River Basin and its influencing factors are analyzed by Mann-Kendall test, Kring interpolation, Pearson correlation analysis and sensitivity coefficient. The results show:(1) During the past 53 years, Hanjiang River Basin average annual ET0 is 1121.96mm；overall is decreased； the rate is 0.39 mm/a and the abrupt change of evapotranspiration in 1967. The annual change of the whole basin ET0 is obvious；the largest contribution is in summer, accounting for 37% of the year, compared with the provinces；the average annual ET0 in Guangdong is the most, while Jiangxi is the least. (2) In space, the Hanjiang River Basin ET0 presents from the distribution pattern of decreasing from the southeast to the northwest；the source area of Hanjiang upstream Meijiang, Hanjiang River Delta and Meitanhe basin is obviously high value area. The Ningjiang, Tingjiang upstream region ET0 value is relatively low；the seasonal ET0 space pattern is similar to the annual ET0 level value distribution. (3) ET0 of relative humidity is negatively sensitive, on average temperature, sunshine time number and average wind speed for is sensitive and evapotranspiration of climate factor sensitivity size sorting: relative humidity>temperature>sunshine number>average wind speed. (4) The main reason for the change of ET0 in this area is the decrease of wind speed, and the relative humidity is the second. This article may provide the basis of river basin water cycle research, and can provide the reference for regional water resources evaluation and management.