UBC Theses and Dissertations
Ski piste heat budget : a case study at the Whistler ski resort, British Columbia, Canada Howard, Rosemary
Accurately calculating snow-surface temperature and liquid-water content for a groomed and compacted ski run, known as a ski piste, is crucial to the preparation of fast skis for alpine racing. This dissertation case study focuses on modelling the above variables for a clear-sky intensive observation period in February 2010. An automated weather station collected relevant meteorological data at a point on a ski piste in Whistler, BC, Canada, known as RC Whistler. The radiation budget is fundamental to this problem, and is affected by tall trees dominating the local horizon. Tree temperature was measured using an infrared camera to estimate thermal emissions. This data, along with calculations of sky downwelling longwave radiation by a radiative transfer model, was input to a new model created for this research. Longwave radiation contributions from trees and sky were weighted by their view factors, which had been calculated from a theodolite survey. Model output is total downwelling longwave radiation at the snow surface for RC Whistler, under clear skies. Downwelling solar radiation penetrates the snowpack, while the surface itself undergoes infrared cooling, resulting in a substantial temperature gradient just beneath the snow surface. A new one-dimensional numerical Lagrangian snowpack model has been written, solving the heat-, liquid-water-, and ice-budget equations to calculate the snow-surface temperature. Meteorological measurements from the clear-sky intensive observation period are prescribed as boundary conditions. Model components and parameters are validated and chosen with idealized model runs. In addition to natural atmospheric processes occurring at and just above the snow surface, human factors were considered. These are frequent skiers compacting the snowpack, and grooming snowcats that churn the top layer of the snowpack and work to increase the snow density and hardness, usually once daily. These effects are simulated in the numerical model. The model successfully simulates snow-surface temperature for the RC Whistler clear-sky intensive observation period. This exploratory investigation indicates that the model shows promise. It is a starting point for a more sophisticated version, incorporating complex boundary conditions such as precipitation and cloudiness, and later being driven by numerical weather prediction output.
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