Atmospheric Water Vapor Budget and Its Long‐Term Trend Over the Tibetan Plateau

Abstract

AbstractThe rapid warming and consequent retreat of glaciers across the Tibetan Plateau (TP) have given rise to the debate on the ability of the atmospheric water supply to alleviate the depletion of surface water storage. We investigate long‐term changes in atmospheric water vapor balance across the TP using 40‐year fifth generation European Centre for Medium‐Range Weather Forecasts (ECMWF) (ERA5) reanalysis. Precipitation, water vapor convergence, and evaporation generally maintain an equilibrium but with different long‐term variation trends: 0.68, −0.18, and 0.69 mm/a, respectively. Results suggest the inability of the water vapor arriving from outside the TP to effectively replenish the surface water storage. Despite of huge changes in atmospheric water vapor balance during summer, the risk of water storage depletion is brought by other three seasons, especially the autumn. The climatology and long‐term trends of water vapor balance exhibit strong variation across the regions of TP. The surrounding areas of Yarlung Zangbo Grand Canyon experience sharp decrease in water vapor convergence, thus reducing precipitation. Moreover, increasing evaporation is expected to severely loss of surface water storage. For the Three Rivers Source Region with no significant changes in total precipitations, decrease in water transported from outside of TP overlaps increase in evaporation results in the possible depletion of surface water storage. Brahmaputra basin, inner TP, and Qilian Mountain exhibit significant wetting trends due to increases in both convergence of water vapor flux and evaporation. Above regional and seasonal characteristics of water vapor, balances across the TP are attributed by inhomogeneous variation of atmospheric heat source and complex changes of atmospheric circulations.