Item: Local verification of the swiss avalanche bulletin
Title: Local verification of the swiss avalanche bulletin
Proceedings: Proceedings of the 1998 International Snow Science Workshop, Sunriver, Oregon
Authors: Stephan Harvey, Roland Meister, Swiss Federal Institute for Snow and Avalanche Research (SLF), Heiri Leuthold, Britta Allgower, University of Zurich, Department of Geography
Abstract: Verification is a difficult yet important part to improve avalanche forecasting. During winter 1996/97 verification activities took place for the area of Davos (approx. 200 km2). At ISSW '96 a prototype GIS-application LAWIPROG was presented to visualize the verbal avalanche bulletin of the Swiss Federal Institute for Snow and Avalanche Research (Davos). For evaluation of the verification LAWIPROG was used. All observed avalanches in the test area were recorded and classified. Moreover, mountain guides, ski patrol teams and private mountaineers were asked to report their observations concerning the snow pack and avalanche situation with a standardized questionnaire. The observed avalanches were introduced to the GIS-database and analyzed for spatial characteristics. All this information was combined in order to estimate the "real" avalanche danger in the form of a subjective verification. LAWIPROG was enhanced with functionalities to visualize the difference between the forecasted bulletin and the effective situation verified in-situ. For each bulletin a map was calculated which shows where the bulletin is either accurate, too high or too low. Additionally, the difference between bulletin and verification can be visualized using a circle diagram where variations in exposition and altitude are emphasized. Concerning only the overall hazard level, in the test area 88% of the days the bulletin and the verification matched. Tendencies in which aspects and at what altitudes the bulletin was either too low or too high can be recognized.
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Keywords: avalanche forecasting, geographic information systems (gis), verification, visualisation
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