Spatiotemporal Distribution Characteristics of Actual Evapotranspiration Over Long-Term Changes on the Mongolian Plateau

Evapotranspiration (ET) is of great significance for the ecological environment and water resource utilization in arid and semi-arid regions. The Mongolian Plateau, owing to drought, low rainfall, and extremely uneven distribution of water resources, has a typical temperate continental climate. A refined understanding of the spatiotemporal distribution of ET in this region will help in establishing regulatory strategies for climate change responses, regional livestock regulation, and grassland degradation suppression. In this study, meteorological station data, precipitation data, and the Penman-Monteith model were used to study the temporal and spatial distribution characteristics of actual ET over the Mongolian Plateau from 2011 to 2022. Results found that: (1) The spatial distribution of ET in the Mongolian Plateau showed a high trend in the north and east and a low trend in the middle and south. There was a significant difference in the regional annual ET, with the highest ET reaching over 500 mm and the lowest being only approximately 70 mm. (2) The annual ET values in 2013, 2018, and 2019 were relatively large, varying between 80 and 500 mm, and the overall ET of the Mongolian Plateau first decreased, then increased, and then decreased. (3) The temporal distribution exhibits a unimodal trend of increasing and then decreasing, with July being the turning point. May–September was a period of high ET, with the highest ET exceeding 100 mm. When vegetation coverage was high, precipitation was abundant, and the vegetation ET effect was strong. Winter was a period of low ET, with a maximum ET of approximately 10 mm in January and December; the ET for the month with the lowest value was approximately zero. The quantitative inversion method proposed in this study can provide method and data support for north and central Asia, and other large arid and semi-arid areas.