The influence of vapor pressure deficit changes on global terrestrial evapotranspiration

Abstract. Vapor pressure deficit (VPD) is increasingly recognized as the primary driver of uncertainty in future global evapotranspiration (E) trends. Accurately characterizing the spatiotemporal dynamics of VPD and clarifying its mechanisms of influence on terrestrial E are crucial for improving water-use efficiency, optimizing ecosystem structure and function, and addressing the challenges of global climate change. Previous studies, however, have largely concentrated on the physiological regulation of vegetation transpiration (Et) at the micro scale. Here, we integrate multi-source remote sensing products and reanalysis datasets spanning 1981–2020 to quantitatively disentangle the contributions of VPD to E and assess its role in shaping global terrestrial evapotranspiration. Our results demonstrate that: (1) across 60.7 % of the global land surface, E increased with rising VPD, while in arid regions with limited soil moisture the effect was generally weak; (2) VPD regulates E primarily by modulating Et, with elevated VPD directly enhancing transpiration; (3) the regulation of E by VPD exhibits a clear climatic gradient: arid zones (1.31 kPa) > humid zones (0.32 kPa), and the tropical (0.79 kPa) > temperate (0.68 kPa) > cold (0.28 kPa) > polar (0.07 kPa). By elucidating the dominant pathways and regional heterogeneity of VPD–E interactions at the global scale, this study strengthens the mechanistic understanding of the coupled warming–atmospheric aridity–water flux system. These findings provide quantitative constraints for predicting terrestrial water-cycle changes under global warming and offer scientific evidence to support targeted climate adaptation strategies worldwide.