Higher warming rate in global arid regions driven by decreased ecosystem latent heat under rising vapor pressure deficit from 1981 to 2022

Abstract

The vapor pressure deficit (VPD), an indicator of atmospheric dryness, is a critical environmental factor influencing terrestrial ecosystem evapotranspiration (ET), with the energy required for ET being supplied by latent heat flux (LE). VPD significantly affects regional and global climate systems by altering surface energy allocation. Under ongoing global warming, VPD is expected to increase continuously, amplifying its climatic impact. In this study, we systematically quantify the responses of ecosystem LE to VPD across different climatic zones using global eddy covariance observations and remote sensing-based modeling. The observational data reveal that LE decreases with rising VPD in arid regions, partly due to limited soil moisture, whereas LE increases in humid regions. Using an improved Remote Sensing-Penman Monteith (RS-PM) model, we estimate global LE from 1981 to 2022, and the modeled trends corroborate the observed spatial patterns: declining LE in arid regions and rising LE in humid zones. This finding corresponds with the divergent warming trends, with greater temperature increases in arid regions linked to a higher proportion of net radiation converted to sensible heat, thereby intensifying local warming. Our results comprehensively characterize the differential LE-VPD relationships under varying climatic conditions by integrating multi-source observations, advancing the understanding of local climate changes driven by LE. These findings are crucial for understanding the varying temperature trends between arid and humid regions.