18 Mar 2024

User Guidelines on Catchment Hydrological Modeling with Soil Thermal Dynamics in Gridded Surface Subsurface Hydrologic Analysis (GSSHA)

Abstract: Climate warming is expected to degrade permafrost in many regions of the world. Degradation of permafrost has the potential to affect soil thermal, hydrological, and vegetation regimes. Projections of long-term effects of climate warming on high latitude ecosystems require a coupled representation of soil thermal state and hydrological dynamics. Such a coupled framework was developed to explicitly simulate the soil moisture effects of soil thermal conductivity and heat capacity and its effects on hydrological response. In the coupled framework, the Geophysical Institute Permafrost Laboratory (GIPL) model is coupled with the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. The new permafrost heat transfer in GSSHA is computed with the GIPL scheme that simulates soil temperature dynamics and the depth of seasonal freezing and thawing by numerically solving a one-dimensional quasilinear heat equation with phase change. All the GIPL input and output parameters and the state variables are set up to be consistent with the GSSHA input-output format and grid distribution data input requirements. Test-case simulated results showed that freezing temperatures reduced soil storage capacity, thereby producing higher peak and lower base flow. The report details the functions and format of required input variables and cards, as a guideline, in GSSHA hydrothermal analysis of frozen soils in permafrost active areas.