A 2-D FINITE-ELEMENT METHOD FOR WATER INFILTRATION IN A SUBFREEZING SNOWPACK WITH A MOVING SURFACE BOUNDARY DURING MELTING

The Galerkin finite element method was applied to solve the equations governing the physical processes of snowmelting and infiltration of me ltwater in a subfreezing snowpack. The numerical model formulation is presented. The solution domain was discretized into 3-node triangular elements. However, the snowpack melting was calculated by 2-node linea r elements accompanied by the corresponding 4-node quadrilateral eleme nts along the melting surface within the same meshing system. Equation s which govern the surface melting, the water flow, the local and the global heat conductions were coupled and solved within the same time s tep. The nodes on the moving snow surface were allowed to move to allo w for the snowpack thinning during melting. The hydraulic and thermal properties of snow were updated based on the snow bulk density change due to meltwater refreezing. Various simulations were presented and co mpared for the purpose of identifying dominant effects of the physical system under complex snowmelting scenarios. The model is able to simu late the growth of thin ice crusts near the snowpack surface. The sens itivity analysis shows that the cold content of snow is the major infl uencing factor which controls the space-time behavior of water infiltr ation in a subfreezing snowpack.