Numerical modeling and simulation of thermo-hydrologic processes in frozen soils on the Qinghai-Tibet Plateau

Study region: The Qinghai-Tibetan Plateau (QTP) is the highest plateau in the world and has been recognized as the "Asia water tower". Frozen soils in China are mostly distributed on the QTP, which is considered as sentinels of global climate change. Study focus: Thermo-hydrologic (TH) processes in frozen soils are prominent for improving the mechanistic understanding of subsurface hydrology in QTP. In this paper, an in-house developed high-resolution cryo-hydrogeological model was implemented into an open-source, massively parallel computational fluid dynamics (CFD) software. Numerical simulations were subsequently conducted to improve the understanding of TH processes in north-and south-facing slopes of a valley in the upper reaches of the Heihe River Basin (uHRB) on the QTP. New hydrological insights for the region: The slope aspect has significant impacts on the temperature and moisture distributions in frozen soils in the uHRB on the QTP. The south-facing slope exhibited earlier thaw than the north-facing slope, as indicated by the soil temperature. Soil moisture and total water storage of the south-facing slope were both lower than those on the north-facing slope, demonstrating that the south-facing slope was drier in general. The south facing slope also had lower amount of ice water storage, which again proved that the south facing slope was warmer. The proposed model is expected to serve as a powerful tool for studying integrated hydrological processes and frozen soil-groundwater interactions in cold regions.