Local terrain-topography and thermal-properties influence on energy and mass balance of a snow cover

Abstract

AbstarctSnow’s interaction with the environment is an important area in environmental science, particularly as climatic conditions change. We consider the local influence at the slope or smaller scale. Near-surface properties drive the dynamic interface with the atmosphere and with surrounding terrain. While accounting for topography, complex interactions involving energy and mass transfer at the snow surface are considered, using a computer simulation (RadTherm/RT). Digital elevation maps are used to numerically fabricate terrain features and vegetation, while applying appropriate thermal properties to specified terrain types. Conduction, convection radiation and phase change (for dry snow) are considered. Particularly relevant to this study are longwave infrared and shortwave radiation, which in the model account for shadowing, multiple reflective and emissive contributions. An example of a north-facing 30˚, snow-covered clearing bounded by trees is examined using measured meteorological conditions. Applying the same weather conditions, the model is used to examine the difference if the trees are assumed bare or covered with snow. Results indicate that, for the conditions considered, when trees are covered with snow, the open slope is cooler and the snow mass loss is less. Spatial variability across the slope is also noted. Differences are largely due to topographic radiation exchange.