Item: Examining the Drivers That Control the Spatial Variability of Surface Hoar and Near-Surface Facets
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Title: Examining the Drivers That Control the Spatial Variability of Surface Hoar and Near-Surface Facets
Proceedings: Proceedings, 2012 International Snow Science Workshop, Anchorage, Alaska
Authors:
- Jordy Hendrikx [ Snow and Avalanche Laboratory, Montana State University, Bozeman, Montana, USA ]
- Tom Leonard [ Yellowstone Club Ski Patrol, Big Sky, MT, USA ]
- Irene Henninger [ Yellowstone Club Ski Patrol, Big Sky, MT, USA ]
- Doug McCabe [ Yellowstone Club Ski Patrol, Big Sky, MT, USA ]
- Ian Hoyer [ Yellowstone Club Ski Patrol, Big Sky, MT, USA ] [ Snow and Avalanche Laboratory, Montana State University, Bozeman, Montana, USA ]
Date: 2012
Abstract: Surface hoar and near-surface facets, once buried, often produce a persistent weak layer that is a common instability problem in the snow pack in SW Montana and many other areas around the world. It is relatively well understood that aspect plays an important role in the location of the growth, and survival of these grain forms, due to the unequal distribution of incoming radiation. However, this alone does not completely explain the complex and often confusing pattern of these grains forms throughout the landscape at larger spatial scales. In this paper we make a preliminary analysis of the spatial variability of near-surface facets and surface hoar, using data from a detailed case study located at the Yellowstone Club in southwestern Montana. We examine paired snowpack and meteorological observations for 15 sites distributed across all four aspects and at different elevations on Pioneer Mountain. At every site, sub-weekly manual observations of surface grain forms were made, while 15 minute data on air temperature and relative humidity data were continually recorded at 1.5m above the snow surface. Using these snowpack and meteorological data, combined with topographic variables and modeled solar radiation, we examine the dominant controls that can discriminate between periods of surface hoar and periods without. We also consider each site individually and note that not one site always exhibits surface hoar during every facet event. This analysis highlights that small-scale meteorological differences and local scale lapse rates can greatly influence the spatial variability of these grain forms, over and above that which aspect alone can explain. These results highlight our incomplete understanding of the processes at this scale, and are likely to have implications for both regional and local scale avalanche forecasting in environments where these grain forms cause ongoing instabilities.
Object ID: issw-2012-1005-1010.pdf
Language of Article: English
Presenter(s): unknown
Keywords: surface hoar, weak layer, grain form, avalanche forecasting
Page Number(s): 1005-1010
Subjects: snow stablility surface hoar near surface facets
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