Land-surface hydrological processes in the permafrost region of the eastern Tibetan Plateau

In order to examine and record the effects of permafrost on hydrological processes in the cryosphere, the hydrology of the ground surface layer was investigated in the permafrost region of the eastern Tibetan Plateau. Water budget components in the surface layer were calculated on a daily basis. Variability in the water budget components, and its causes, was investigated on both seasonal and daily bases. The results showed that coupling of the thaw-frost cycle to seasonality in precipitation is the principal control of hydrological processes in the upper 2 m of the soil. When the ground surface begins to thaw, from the surface down, the concentration of melt water within a thin surface layer leads to a rapid increase in evaporation, then a slight decrease occurs in the continuous permafrost region as the wet soil zone moves downward. An analysis of seasonal variation in the water budget components demonstrated that the dominant water cycling arises from the processes of precipitation and evaporation that are typical in this region. The freeze-thaw cycle, which affects seasonal soil moisture, water storage, evaporation, and the mobilization of water through the soil and vegetation during the summer monsoon season, is a dominant feature of the land-surface hydrology in the permafrost region of the eastern Tibetan Plateau.