Item: Analysis of weak layer avalanche activity in the columbia mountains, british columbia, canada
Title: Analysis of weak layer avalanche activity in the columbia mountains, british columbia, canada
Proceedings: 2002 International Snow Science Workshop, Penticton, British Columbia
Authors: Pascal Hageli and David M. McClung, Atmospheric Science Program, The University of British Columbia, Vancouver B.C., Canada
Abstract: This study uses avalanche observations to characterize the spatial characteristics and temporal avalanche activity patterns on persistent weak layers. The study is situated in the Columbia Mountains in Western Canada, a mountain range with a transitional snow climate. The data was provided by Canadian Mountain Holidays, which operates 11 individual helicopter-skiing operations in this area, covering a total area of 20,000 km2. The analysis shows that early season faceted snow layers and surface hoar weak layers are the main concern in this area. About 16% of the natural avalanche activity is on these persistent weak layers, and 28% when skier/helicopter triggered avalanches are included. It is shown that persistent weak layers with significant avalanche activity are generally widespread. While surface hoar layers seem to have fairly well defined avalanche cycles for about 2 to 3 weeks after their burial, faceted snow layers are active more sporadically throughout the entire season. The results of the analysis are promising for the development of a new statistical model for forecasting avalanche activity specifically on persistent weak layers. This has been a weak point of the currently used statistical models, which are mainly based on meteorological variables and, as a consequence, work best for new snow instabilities. An additional aspect of this work is that, for the first time, it allows the characterization of the avalanche climate of an area on the basis of actual avalanche observations. All previous studies have only used weather observations for their climate type definition.
Keywords: persistent weak layers, avalanche climate, avalanche forecasting
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