Analysis of the change characteristics and the weather effect mechanism of reference evapotranspiration in Manasi oasis

Based on the meteorological data of the four weather stations in Manasi oasis from 1961 to 2005, daily reference evapotranspiration (ET0) was calculated by the Penman-Montieth formula, the characteristics and trend of ET0 with yearly, seasonal and monthly value were analyzed, and the main factors affected ET0 were discussed with statistic method also. The results show that the ET0 in Manasi oasis is decreased slightly over the past 45 years in Muosuowan, Paotai, Wulanwusu weather stations and Shihezi was reverse. The ET0 in July and August is the highest and that of in December and January is the lowest in the year. The sequences of the main factors affected ET0 are wind velocity (U2), sunshine time (Ta), average temperature (Ta) and relative humidity (H) in three weather stations and another station is Ta, Ta, U2, H.