The Loess Plateau is an important ecological conservation area, which is sensitive to climate change, located in China. It is also an important ecological governance area. Ecological restoration projects in the Loess Plateau are related to the sustainable development of the Yellow River Basin and national ecological security. Moisture is the main factor that restricts vegetation restoration in the Loess Plateau. Therefore, the variation of water resources has a direct impact on agricultural production, ecological construction, and sustainable development of the social economy in this region. In the study area water resources are relatively scarce, and evaporation is an important hydrological factor. It is necessary to study pan evaporation variations and their influence factors to provide information for ecological construction, agricultural production, and water management in the Loess Plateau. In this study, pan evaporation, temperature, wind speed, precipitation, relative humidity, and water pressure data collected from 61 weather stations were used to analyze the characteristics of pan evaporation variation and its influence factors in the Loess Plateau from 1960 to 2018, through the Mann-Kendall test, cumulative anomaly, and linear trend methods. At the same time, the related driving factors were evaluated with multiple regression analysis. The results indicate that annual evaporation in the Loess Plateau showed an obvious decreasing trend at a rate of -6 mm·(10a)-1 in the last 59 years, but it increased after the year 2000. In the study area, two turning points and three stage changes were identified: Pan evaporation decreased between 1960 and 1974, and from 1975 to 1996, while it increased from 1997 to 2018. In addition, pan evaporation showed a decreasing trend in spring, summer, and autumn, and an increasing trend in winter. Spatially, the overall and local changes in pan evaporation were not synchronized: regions I, II, V, and VI showed an increasing trend, while the Guanzhong Plain and Shanxi Loess Plateau showed a decreasing trend. The decrease in average wind speed, sunshine hours, and the increase in water vapor pressure were important factors for the decrease in pan evaporation. The main factors responsible for this reduction were the decrease of wind speed and sunshine hours, and the increase of water vapor. In spring and autumn, the wind speed played a major role in the variation of pan evaporation, and the main influence factors in summer were precipitation, water vapor pressure, and in winter was temperature. In light of the future global warming scenarios, the variation of evaporation has become a common concern for global climate change, particularly as the decline in pan evaporation has now been reported in many regions of the world. Evaporation is an important component of the thermal balance and water budget on the Earth surface, and it is directly affected by both land use and climate change. The research on evaporation variation will help us understand the dynamics of climate change and clarify the characteristics of the water cycle in the Loess Plateau.
