Some approaches to modeling phase change in freezing solis

Abstract

Phase change effects associated with freezing soils dominate the thermal state of the soil regime. Furthermore, freezing of soil water influences the soil moisture regime by providing a moisture sink which tends to draw mobile soil moisture to freezing fronts. Consequently, it is critical to general purpose models that soil water phase change effects and the interrelated problem of estimating the moisture sink effects (i.e., conversion of liquid water to ice) be accurately modeled. The choice of such a model will not only influence the precision of simulated temperatures and water contents in a freezing soil, but also have a significant impact on computational efficiency. A review of several current models that assume unfrozen water content is functionally related to subfreezing temperatures indicate that within a freezing soil the soil water flow model and heat transport model parameters are restricted in spatial gradients according to the spatial gradient of modeled unfrozen water content. A freezing soil model based on the concept of isothermal phase change of soil water is proposed as an alternative approach.