Item: Spatially predicting surface hoar crystal size in sparse forests using shading in satellite imagery
Title: Spatially predicting surface hoar crystal size in sparse forests using shading in satellite imagery
Proceedings: International Snow Science Workshop, Davos 2009, Proceedings
Authors: Cora Shea and Bruce Jamieson, Department of Geoscience, University of Calgary, Canada, Department of Civil Engineering, University of Calgary, Canada
Abstract: Surface hoar size and location can help predict avalanche trigger points after burial. This paper presents an empirical model to predict the size of surface hoar at the small scale, i.e. less than 10 m, in sparsely forested areas. The model is based on 288 point samples of surface hoar crystals, and uses greyscale values in satellite imagery to map its predictions over a 40-to-100 m scale from a single point observation. When verified in a different surface hoar formation cycle, at a different location and aspect, with crystals sized to more than 7 mm, the model predicted the correct size to within 2 mm of actual size, for 70 percent of the 47 verification points. We present the physical basis for this model through night time surface temperature measurements and sky view photograph masks obtained with a wide angle lens. Beyond helping to describe the small scale variance of surface hoar in commonly skied areas of sparse trees in North America, it confirms processes that drive surface hoar formation anywhere. And although potentially applicable only to areas with trees and weather similar to those examined here, this work demonstrates that with the right conditions surface hoar size can be spatially predicted with reasonable accuracy.
Keywords: spatial variability, surface hoar, mapping, prediction, satellite imagery
Digital Abstract Not Available