Simulation of alpine snow distributions in the northern Colorado Rocky Mountains using a numerical snow-transport model

Fall 1999.Also issued as author's thesis (M.S.) -- Colorado State University, 1999.Includes bibliographical references.Two methodologies for simulating winter snow distributions in alpine terrain are presented. First, a numerical snow-transport model (SnowTran-3D) is driven from direct meteorological observations, and second, SnowTran-3D is driven from a regional atmospheric model (ClimRAMS). In each case the simulated snow distributions are compared to observed snow depth transects within two alpine sites in the Northern Colorado Rocky Mountains, Rocky Mountain National Park, and Medicine Bow Mountains. The atmospheric conditions at these sites are characterized by persistent westerly winds with average speeds of 13 m/s, which is significantly greater than the threshold for snow transport (approximately 5 m/s). Consequently, snow redistribution by wind is the dominate component in this environment. Drift features in these areas form around rocks, alpine vegetation, and small and large topographic variations. The model successfully simulated the large-scale snow drifts, but due to the relatively coarse resolution of the vegetation and topographic data inputs (30 m), the model was unable to reproduce some of the smaller scale snow drift features. The model built large drifts in the upper regions of the east facing cirques in Rocky Mountain National Park, in regions where large perennial snow fields are observed. The model results support the theory that snow transport by wind is an important factor in sustaining these snow fields.Sponsored by NOAA grant number NA67RJ0152