The contributions of different variables to elevation-dependent land surface temperature changes over the Tibetan Plateau and surrounding regions

The elevation-dependent surface warming (i.e., the surface temperature trend changes systematically with elevation, EDW) over the Tibetan Plateau (TP) largely affects the hydrological and ecological security in Asia. Although many physical mechanisms have been attributed to EDW, the relative importance of each mechanism remains unclear. Using land surface temperatures (LSTs) and other variables from the land component of the fifth generation of the European ReAnalysis product (ERA5-Land), we quantify the contributions of atmospheric and surface factors associated with the surface energy balance to LST changes at different elevations on the TP and its surrounding regions, and further explore the mechanisms of EDW. The results show that along with a positive EDW (enhanced high-elevation LST increases) up to approximately 4500 m, a negative EDW (reduced high-elevation LST increases) above 5000 m appeared in both daytime and nighttime and during all seasons. A cooling LST trend even occurred above 5200 m during daytime in summer. This negative EDW is mainly caused by the increased cloud cover fraction and evapotranspiration (heat storage) during daytime (nighttime) in summer, while in winter, it is mainly caused by the increased negative (decreased positive) contribution of heat storage during daytime (nighttime). Overall, EDW was controlled by atmospheric factors, while surface factors contributed variably and constrained or enhanced the LST changes depending on the season and time of day. In summer, cloud-radiation feedback and evapotranspiration processes are the main mechanisms controlling EDW, while in winter, snow/ice albedo feedback and the sensitivity of downward longwave radiation to the specific humidity are the main EDW mechanisms. Our results provide important insights into EDW over the TP.

Automated summary

This study investigates the mechanisms of surface warming over the Tibetan Plateau (TP) and finds that lower elevation areas exhibit enhanced high-elevation surface temperature increases, while higher elevation areas experience reduced increases. The results show that atmospheric factors, such as cloud-radiation feedback and evapotranspiration processes, are the main mechanisms controlling elevation-dependent surface warming in summer, while snow/ice albedo feedback and downward longwave radiation sensitivity to humidity play significant roles in winter.