The influence of vapor pressure deficit changes on global terrestrial evapotranspiration

Vapor pressure deficit (VPD) has been widely recognized as a key driver of uncertainty in future global evapotranspiration ( E ) trends. Accurately characterizing the spatiotemporal dynamics of VPD and elucidating its influence on terrestrial E are critical for understanding land–atmosphere water and energy feedback processes under climate warming. However, previous studies have largely focused on the physiological regulation of plant transpiration ( E t ) at the leaf or canopy scale, leaving the quantitative understanding of VPD– E interactions at the global scale incomplete. By integrating multi-source remote sensing products and reanalysis datasets, this study quantitatively evaluates the role of VPD in regulating global terrestrial E variability. The main findings are as follows: (1) Approximately 60.7 % of global land area exhibits positive apparent sensitivity of E to VPD, with a global mean sensitivity of 293.3±62.3 mm hPa −1 , and stronger responses observed in warm and humid regions. (2) VPD is positively correlated with E t overall, particularly in mid-to-high latitudes of the Northern Hemisphere, whereas its correlation with bare soil evaporation ( E b ) is weaker and tends to be negative in water-limited regions. (3) The VPD– E relationship exhibits a pronounced aridity-dependent threshold, which decreases progressively from arid (1.90 kPa) and semi-arid (1.46 kPa) regions to semi-humid (0.49 kPa) and humid (0.47 kPa) regions. Further path analysis reveals that VPD regulates E through interconnected pathways involving atmospheric demand, soil moisture, vegetation physiology, and energy supply, with an overall negative net effect on E . This study clarifies the dominant pathways and regional heterogeneity of VPD– E interactions at the global scale, providing quantitative constraints for predicting the response of the terrestrial water cycle to increasing atmospheric aridity.