Estimation and spatiotemporal analysis of actual evapotranspiration over Qinghai-Tibet Plateau using an Alpine Grassland-Adapted Priestley-Taylor model.

• An improved PT model based on shortwave infrared soil moisture index. • The PT-SIMI model rectifies ET underestimation in alpine grassland of the QTP. • The average ET over the QTP from 2011 to 2020 remains relatively stable at 478 mm/year. • Air temperature primarily drives ET over water bodies, grasslands and forests. • Soil moisture exerts a pronounced influence on ET in bareland and grassland. Evapotranspiration (ET) is a crucial process in the land water cycle, energy balance, and carbon cycle, making it essential for understanding ecosystem health and climate change. The Qinghai-Tibet Plateau (QTP) is a vital contributor to the global water cycle and ecosystem, and its water resources and ecological environment are of great significance to the development and survival of Asia. To accurately estimate ET on the QTP, this paper proposes an improved Priestley-Taylor (PT) model based on shortwave infrared soil moisture index (SIMI). The model is applied to estimate ET on the QTP from 2011 to 2020, allowing for a comprehensive spatiotemporal analysis. The findings indicate that, (1) The PT-SIMI model has higher estimation accuracy than both the Modified Satellite-Based Priestley-Taylor (MS-PT) model and the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model at most sites, particularly in alpine grasslands sites, and demonstrates a greater sensitivity in capturing changes in soil moisture; (2) the spatial distribution of ET on the QTP demonstrates a declining pattern from southeast to northwest; (3) the average ET from 2011 to 2020 remains relatively stable at 478 mm/year; (4) notable spatial variations in ET are observed across the plateau, with noticeable upward trends observed in the central and western regions, while the south central region experiencing a decreasing trend. This study provides valuable insights into the water cycle and ecological environment of the QTP and its findings can support sustainable development in the region. [ABSTRACT FROM AUTHOR]