Item: Plume Formation in Powder Snow Avalanches
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Title: Plume Formation in Powder Snow Avalanches
Proceedings: International Snow Science Workshop Grenoble – Chamonix Mont-Blanc - October 07-11, 2013
Authors:
- Perry Bartelt [ WSL Institute for Snow and Avalanche Research, SLF, Davos, Switzerland ]
- Yves Bühler [ WSL Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland ]
- Othmar Buser [ WSL Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland ]
- Christian Ginzler [ WSL Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland ]
Date: 2013-10-07
Abstract: A long-standing problem in avalanche science is to model the formation and propagation of icedust clouds that accompany fast moving dry snow flowing avalanches. Since the winter of 2002/2003 photogrammetric measurements of snow avalanche clouds have been performed at the Vallée de la Sionne test site. Synchronized images acquired from two different viewing angles allow the construction of three-dimensional powder cloud surface models. Between 2003 and 2006 seven avalanches with initiation volumes over 50’000 m3 were recorded. Plume heights reached over 100 m and the avalanches entrained up to 10 million m3 of air. Using high resolution laser scans of the terrain it was possible to investigate the formation and development of the powder clouds as a function of terrain and avalanche speed, thereby gaining valuable information concerning the flow dynamics. The plumes form continuously at the avalanche front and then diffuse slowly. Using isolated plumes as markers, we calculate the travel distance between the point of initiation and the final suspension height. The upward velocity appears to be divided into a high-velocity, forced expulsion stage and a slower diffusion stage. Segregation effects are also visible as packets of extruded mass are thrown upwards and then descend, leaving an ice-dust suspension hanging in the air. Lateral spreading speeds are significantly slower than the front propagation. Furthermore, there is also definite terrain influence as plume formation appears to be concentrated at gullies and extreme changes in slope angle.
Language of Article: English
Presenters: Unknown
Keywords: avalanche dynamics, powder snow avalanches, plume formation, ice-dust cloud, blowout height, suspension layer
Page Number(s): 576-582
Subjects: powder avalanche snow avalanche dynamics ice-dust clouds
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Digital Abstract Not Available
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