The Qinghai-Tibet Plateau,also known asChinas water tower,has undergone a series of changes in the water-heat balance in its alpine meadows,which are attributed to global climate change.Therefore,it is vital to examine the effects of climate change on the hydrological processes on the plateau by analyzing the relationship between evapotranspiration and meteorological factors.In the present study,based on automatically observed meteorological data from 2011-2016,random forest analysis was applied to quantitatively evaluate the relative importance of seven major meteorological factors(e.g.,net radiation,temperature,apor pressure deficit,rainfall,wind speed,relative humidity,and sunshine hours)on the reference evapotranspiration(ET0) to explore the key meteorological factors affecting variation in ET0.In addition,the seasonal and interannual variation in ET0 from 2011-2016 were also analyzed.The results show that 1)at the seasonal scale,ET0 could be characterized by a unimodal relationship that increases from January to July,with the maximum value occurring in July(132.48 mm),then decreases from July to December.At the interannual scale,the ET0 increased significantly from 2011-2016 with an average of 1 023.03 m~2)The net radiation was the most important factor affecting the annual variation in ET0,followed by vapor pressure deficit,maximum air temperature,sunshine hours,and mean air temperature.The impact of meteorological factors on the growing season ET0 was ranked in the following order:net radiation>sunshine hours>vapor pressure deficit>maximum air temperature;rainfall,wind speed,minimum air temperature,and mean air temperature had little impact.The impact of meteorological factors on the non-growing season ET0 was ranked in the following order:net radiation>vapor pressure deficit>wind speed>maximum air temperature>mean air temperature;relative humidity,sunshine hours,rainfall,and the minimum air temperature had little impact.Our results indicated that the ET0 of an alpine Kobresia meadowin the northern Qinghai-Tibet Plateau was dominated by net radiation.Moreover,the maximum air temperature had stronger effects on the ET0 than did mean air temperature or minimum air temperature,which could provide a new insight for the appropriate management of plateau water resources.