Understanding the Mass, Momentum and Energy Transfer in the Frozen Soil with Three Levels of Model Complexities
Abstract. Frozen ground covers vast area of earth surface and has its important ecohydrological implications for high latitude and high altitude regions under changing climate. However, it is challenging to characterize the simultaneous transfer of mass and energy in frozen soils. Within the modeling framework of STEMMUS (Simultaneous Transfer of Mass, Momentum and Energy in Unsaturated Soil), the model complexity of soil heat and mass transfer varies from uncoupled, to coupled heat and mass
... ed heat and mass transfer, and further to the explicit consideration of airflow (termed as unCPLD, CPLD, and CPLD-AIR, respectively). The impact of different model complexities on understanding the mass, momentum and energy transfer in frozen soil were investigated. The model performance in simulating water and heat transfer and surface latent heat flux was tested on a typical Tibetan Plateau meadow. Results indicate that the CPLD model considerably improved the simulation of soil moisture, temperature and latent heat flux. The analyses of heat budget reveal that the improvement of soil temperature simulations by CPLD model is ascribed to its physical consideration of vapor flow and thermal effect on water flow, with the former mainly functions above the evaporative front and the latter dominates below the evaporative front. The contribution of airflow-induced water and heat transport to the total mass and energy fluxes is negligible. Nevertheless, given the explicit consideration of airflow, vapor flow transfer and its effect on heat transfer were enhanced during the freezing-thawing transition period.