MODELING OF SNOW MELTING AND UNIFORM WETTING FRONT MIGRATION IN A LAYERED SUBFREEZING SNOWPACK

A method of modeling freeze-thaw cycles of naturally deposited snowpac ks is presented. The model involves the Stefan condition as an indepen dent governing equation on the exterior moving boundary to calculate s nowpack thinning, flow of water through a variably saturated layered p orous medium as described by the Richards equation, and heat conductio n with a phase change. The heat conduction problem was treated in two ways. Local heat conduction between a snow grain and its surrounding w ater film was treated by using a simple energy balance. Global heat co nduction with a phase change (the Stefan problem) was introduced to ca lculate the space-time temperature distribution. In order to handle mu ltiple interior moving boundaries, a specific form of the enthalpy for mulation was used for heat conduction with a phase change. Changing ma terial properties were considered according to the calculated meltwate r refreezing.