Trends and attribution analysis of modelled evapotranspiration on the Tibetan Plateau

Evapotranspiration (ET) is an important part of the hydrological cycle, significantly influencing water distribution, energy cycle, and plant growth. In the context of global warming and acceleration of the water cycle, it is of great significance to analyse the trend and attribution of ET on the Tibetan Plateau (TP), which is most a sensitive and vulnerable area of the world. In this article, ET products, obtained from the improved Penman-Monteith-Leuning model with 1 km spatial resolution and 8 days temporal resolution, were used to investigate the trend and attribution of modelled ET and its components on the TP during the 2003-2017 period. The modelling results show the ET, soil evaporation (E), and vegetation transpiration (T) present a highly similar spatial pattern, with a distinct decreasing gradient from the humid southeastern areas to the arid northwestern areas of the plateau. In terms of its components, E (269 mm yr(-1)) contributes about 70% of ET (385 mm yr(-1)), especially in the northwestern region. Although the relationship between ET and elevation is not clear, the results showed that E increased with elevation, while T exhibited the opposite trend. At the same time, approximately 80% of the grids showed an increasing trend (increasing at a rate of 4.7 mm yr(-1)), mainly concentrated in the southeastern area, where the increased ET in forests and alpine meadows was the most obvious. Variations of modelled ET on the TP is distinguished into energy-restricted and water-restricted regions, corresponding respectively to the eastern region affected by temperature, and the western region controlled by soil moisture. The results of the present study can greatly improve our understanding of the hydrological cycle and the ability to manage water resources on the TP within the context of global climate change.

Automated summary

This study investigated the trend and attribution of evapotranspiration (ET) on the Tibetan Plateau (TP) using ET products obtained from a model. The results showed that ET, soil evaporation (E), and vegetation transpiration (T) presented a similar spatial pattern, with E contributing the most to ET. Additionally, the variations of modelled ET on the TP were distinguished into energy-restricted and water-restricted regions.