Evaluation of Parameterization Schemes for Matric Potential in Frozen Soil in Land Surface Models: A Modeling Perspective

Abstract

AbstractSoil matric potential (SMP) is an important variable in land surface models (LSMs) for regulating soil hydrological processes and highly influenced by soil ice in frozen ground. In this study, four SMP parameterization schemes that incorporate different effects of soil pore ice were separately integrated into the Simultaneous Heat and Water (SHAW) model and evaluated for their ability to simulate heat and water transport at a permafrost monitoring site at the Tanggula Mountain Pass on the inner Qinghai‐Tibet Plateau based on the same data and model settings. The schemes differed in their treatment of pore ice effects, including effective porosity and cryosuction. An identifiability analysis of SMP‐related parameters for each scheme was performed, based on 1,000‐fold random parameter sampling. The scheme that considered both effects performed best, accurately simulating both soil moisture content and temperature in the active layer. The schemes that considered only one effect of pore ice showed limitations, with the effective porosity scheme underestimating unfrozen water content and the cryosuction scheme seriously overestimating it, and both schemes leading to large discrepancies in simulated soil temperature. The scheme that ignored both effects performed better than the partially considered schemes due to a compensating effect of reduced effective porosity and increased cryosuction in the presence of pore ice, but not as well as the scheme that considered both effects, particularly in simulating soil temperature during freezing periods and estimating unfrozen water content near the mid‐depth of the active layer.