Analysis of effects of climate change on reference evapotranspiration on the Loess Plateau in recent 50 years

To study the reason of soil desiccation and variation characteristics of vegetation evapotranspiration in the loess plateau. Based on the meteorological data collected from five meteorological stations in recent 50 years in the loess plateau, the reference crop evapotranspiration (ET0) was calculated with the Penman-Monteith equation. The change characteristics of daily, monthly and annual ET0 were analyzed respectively. The correlation of average temperature, maximum temperature, minimum temperature, sunshine hours, wind speed and average relative humidity with ET0 were analyzed. The results show that there is a very significant correlation between the daily, monthly ET0 and temperature and sunshine hours, respectively. Both highest daily and monthly average ET0 appear in June, respectively. Both daily and monthly average ET0 curves have single peak, respectively, the and distribution of daily and monthly ET0 are consistent with the variation of season changes. Apart from the significant decreasing trend of annual ET0 in Xi'an and Xining, there were no significant changes in Yan'an, Yuling and Lanzhou, meanwhile, the ET0 show increasing trend since 1980s except Xining.