Variation Characteristics and Influence Factors of Potential Evapotranspiration in Aksu Region

Potential evapotranspiration（ET0） is the key factor to evaluate the dry-wet conditions. In this paper, based on the daily meteorological data of six climatic stations in Aksu region from 1961 to 2016, ET0 of each station is calculated by utilizing Penman-Monteith formula. Also, spatial and temporal trends of ET0 are analyzed. The correlation analysis is used to study the influence of each climatic factor to ET0 Result indicated that ET0 increased from the south to the north in the study region. Also, ET0 in the eastern and western region were higher than those of central and southern region. The annual average ET0 in study region was 1 049 mm in recent 60 years; ET0 in summer was the highest in all four seasons, with the average of 457 mm, ET0 in winter was the lowest in four seasons, with the average of 55 mm. Changes in ET0 both in annual and seasonal in study region showed a decreasing trend in the early 60 years. Furthermore, ET0 in summer had decreased obviously, with the rate of 5.85 mm/10 a, while ET0 in winter had decreased with relatively small rate（0.69 mm/10 a）From 1995 to 2015, the annual and seasonal ET0 showed an increasing trend Results from MK model showed that the abrupt deceasing change of ET0 in Aksu region occurred in1981. The correlation analysis showed that ET0 in Aksu region was correlated with annual sunshine duration and wind speeds positively, and they were correlated with relative humidity negatively.