Soil moisture and atmospheric dryness govern regional controls of land–atmosphere water and heat fluxes on the Tibetan Plateau

Water and heat flux exchanges over the Tibetan Plateau strongly affect Asian and global climate, yet sparse observations leave their controlling mechanisms poorly understood. Using eddy-covariance data from 19 sites, we identify the controls on latent (LE) and sensible (H) heat fluxes and evaluate flux products. The results reveal regional contrasts in the controls on LE: in humid regions, LE is primarily driven by net radiation (Rn); in semi-humid regions, higher shallow volumetric water content (shallow VWC) shifts LE from water-limited to energy-limited; and in arid and semi-arid regions, shallow VWC and vapor pressure deficit (VPD) jointly regulate LE. These contrasts arise from changes in how surface conductance (Gs) responds to shallow VWC and VPD: in arid and semi-arid regions, higher shallow VWC enhances the sensitivity of Gs to VPD and increases the reference conductance (Gs_ref), whereas higher VPD rapidly reduces Gs and thereby suppresses LE. Biases in flux products stem from inaccurate representation of these key control processes.