A numerical study of process complexity in permafrost-dominated regions
Abstract. Numerical modeling of permafrost requires adequate representation of atmospheric and surface processes, a reasonable parameter estimation strategy, and site-specific model development. The three main research objectives of the study are: (i) to propose a methodology that determines the required level of surface process complexity of permafrost models, (ii) to design and compare different conceptual numerical models of increasing surface process complexity, and (iii) to calibrate and validate the numerical models setup at the Yakou catchment on the Qinghai-Tibet Plateau. Three cases with varying top boundary conditions have been established: (i) Case 1: Dirichlet thermal boundary condition of measured surface temperature at 0.0 m. (ii) Case 2: Surface water and energy balance without snow. (iii) Case 3: Surface water and energy balance with snow. The calibration was carried out by coupling the Advanced Terrestrial Simulator (Numerical model) and PEST (Calibration tool). Simulation results showed that (i) Permeability and Van Genuchten alpha of peat and mineral were highly sensitive. (ii) The thawing of permafrost was not adequately represented by considering only subsurface processes. (iii) Liquid precipitation aided in increasing the rate of permafrost degradation. (iv) Deposition of snow insulated the subsurface during the thaw initiation period. We have successfully established a pseudo-1-D model at the Yakou catchment in the Qinghai-Tibet Plateau. A novel methodology is proposed to assess the surface process level complexity in permafrost-dominated regions. The numerical model can be used to determine the impacts of climate change on permafrost degradation.
Model code and software
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