A numerical model for surface energy balance and thermal regime of the active layer and permafrost containing unfrozen water

Abstract

This paper describes a surface energy balance approach-based one-dimensional heat transfer model for estimating surface energy balance components and the thermal regime of soil. The surface energy balance equation was used to estimate the upper boundary temperature conditions for thermal conduction calculations and to calculate surface heat fluxes. The influence of unfrozen water on the thermal properties of soils was accounted for in the heat transfer model. The effect of snow was included in the model by extending the heat conduction solution into the snow layer and computing the surface heat balance components and the snow surface temperature. The model was driven by meteorological data collected at Barrow, AK, and was validated against the observed ground temperatures at Barrow. The results show good agreement between the simulated and the measured soil temperatures at depths of 0.01, 0.29, 0.50, and 1.0 m. When snow cover was present, snow surface temperatures were colder than ground surface temperatures and air temperatures, with mean temperature differences of −5.36 and −1.55 °C, respectively. We conclude that the model presented in this study can be used to calculate the surface energy balance components, simulate the ground temperatures, and investigate the impact of seasonal snow cover on the thermal regime of the active layer and permafrost containing unfrozen water with a quite reasonable accuracy. Snow density, which determines the snow thermal conductivity, volumetric heat capacity, and albedo in this model, can strongly affect the performance of this model.