Spatio-temporal variation of evapotranspiration partitioning and its response to environmental factors in a semi-arid region of northern China

• Developed a PT-JPL model to simulate long-term actual evapotranspiration and its partitioning. • Validated the model’s simulation performance at both site-scale and regional-scale levels. • Investigated the key control parameters influencing evapotranspiration and its partitioning. Clarifying evapotranspiration (ET) and its partition within ecosystems can provide a basis for understanding the interaction between the atmosphere and ecosystems. The Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model was used to carry out long-term simulation of ET and transpiration/evapotranspiration (T/ET) in a typical semi-arid region of northern China named Hailar River basin. Then, the effectiveness of PT-JPL model was confirmed by multiscale validation, and the spatiotemporal variations and influencing factors of ET and T/ET were analyzed accordingly. The results showed that the PT-JPL model well reproduced the fluctuation and extreme value of ET at the site scale (k = 0.86, R 2 = 0.85). Compared with the GLEAM and GLDAS datasets, the spatial representativeness of ET and T/ET simulated by the PT-JPL model was the strongest, and their spatial uncertainty was only 22.75 mm and 0.05, respectively. The average annual ET and T/ET in the study area increased at a rate of 0.73 mm/year and 0.005/year from 1982 to 2020, respectively, and summer was the season with the highest average and variation trend of ET and T/ET. Moreover, ET and T/ET showed an obvious spatial difference of high in the east and low in the west, with the highest values concentrated in the eastern forest area and increasing at an average rate of 1.58 mm/year and 0.003/year, respectively. In addition, NDVI and land surface temperature were the most critical environmental factors affecting ET and T/ET changes on different underlying surfaces. It provides a good demonstration for acquiring long-term scale ET and its components, thereby helping humanity gain a deeper understanding of the interactions between the atmosphere and terrestrial ecosystems.