Note: / The purpose of this study was to develop and evaluate a numerical model for simulating the influence of seasonal snow cover on the ground thermal regime.The physical processes occurring within the snow pack and underlying ground, as well as at the surface, are reviewed from the viewpoint of their eventual inclusion in a practical numerical model. A finite difference heat conduction model suitable for long-term studies of the snow-ground thermal interaction is presented. This model incorporates a numerical prediction of density and temperature profiles within an evolving snow cover. Phase change within the ground is treated by a new numerical method which has important computational advantages over older methods.[...] / Cette etude avait pour but Ie developpement et l'evaluation d'un modele numerique pour la simulation de l'influence du manteau neigeux saisonier sur Ie regime thermique du sol.Les processus physiques rencontres dans Ie manteau neigeux et Ie sol sous-jacent ainsi quIa l'interface air-surface sont discutes et passes en revue dans l'optique restreinte de leur eventuelle inclusion dans un modele numerique. On presente ensuite un modele a conduction en differences finies qui convient pour les etudes de l'interaction thermique neige-sol a long terme. Le modele inclut un calcul numerique de l'evolution temporelle des profiles de densite et de temperature du manteau neigeux. Les changements de phase dans Ie sol sont traites par une nouvelle technique numerique avantageuse pour Ie calcul.[...]

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Forested watersheds in western North America are subject to significant change from natural and anthropogenic disturbance, including wildfire. Forest canopy changes have subsequent impacts on sub-canopy snow processes. A simple, process-based point energy balance model was developed to quantify differences in energy balance characteristics between a burned and a healthy forest stand. Potential model uncertainties were identified using sensitivity analyses. Simulated snowmelt accurately recreated measured snowmelt, providing confidence in the model’s ability to simulate energy balance processes in subcanopy environments where wind redistribution and sublimation are not major drivers of the local snowmelt energy balance. In the burned stand, sub-canopy snow accumulation was greater but melted more rapidly than in the healthy stand. The removal of forest canopy resulted in more energy available for snowmelt, including higher short-wave and lower long-wave radiation, and increased turbulent fluxes. Burned stands should be considered a separate land cover type in larger scale watershed models. / xii, 129 leaves : ill,, map ; 29 cm