Land-Atmosphere Interactions Partially Offset the Accelerated Tibetan Plateau Water Cycle through Dynamical Processes

The Tibetan Plateau (TP) has become wetter and warmer during the past four decades, which leads to an adjustment in the surface energy budget, characterized by enhanced surface latent heat and weakened surface sensible heat. However, the impacts of these surface energy changes on climate are unclear. In this study, we investigate the atmo-spheric response to the altered surface energy budget in the monsoon season over the TP using regional climate simula-tions. The inhibited surface sensible heating weakens the thermal effect of the TP, which further suppresses low-level convergence and upper-level divergence, thereby weakening the water vapor flux convergence over the plateau. The weak-ening of low-level air humidity by this dynamical response exceeds the supply from the enhanced surface evaporation, causing decreased precipitation (decreasing more in the wet eastern plateau and less in the dry west). Further analyses show that the precipitation frequency increases mainly for light precipitation while decreasing for heavy precipitation. It is thus demonstrated that on the TP, land surface energy-atmosphere interactions can mitigate the rate of precipitation in-crease, suppress the increase in frequency of heavy precipitation, and weaken the east-west contrast in precipitation amount, through a dynamical mechanism. Overall, land-atmosphere interactions on the TP exert negative feedback to par-tially offset the accelerated plateau water cycle under a changing climate.

Automated summary

The Tibetan Plateau has experienced increased warmth and precipitation over the past four decades, resulting in changes to the surface energy budget. This study investigates the atmospheric response to these changes using regional climate simulations. It is found that the weakened surface sensible heating reduces thermal effects, leading to decreased water vapor convergence and ultimately decreased precipitation. Furthermore, the frequency of light precipitation increases while heavy precipitation decreases. Overall, land-atmosphere interactions on the Tibetan Plateau have a negative feedback effect on the water cycle, partially offsetting the impacts of climate change.