Item: The Effects of Slope Aspect on the Formation of Surface Hoar and Diurnally Recrystalized Near-Surface Faceted Crystals: Implications for Avalanche Forecasting
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Title: The Effects of Slope Aspect on the Formation of Surface Hoar and Diurnally Recrystalized Near-Surface Faceted Crystals: Implications for Avalanche Forecasting
Proceedings: Proceedings of the 2004 International Snow Science Workshop, Jackson Hole, Wyoming
Authors:
- Mike S. Cooperstein [ Department of Earth Sciences, Montana State University, Bozeman, MT, USA ]
- Karl W. Birkeland [ Department of Earth Sciences, Montana State University, Bozeman, MT, USA ] [ U.S. Forest Service National Avalanche Center, Bozeman, MT, USA ]
- Kathy J. Hansen [ Department of Earth Sciences, Montana State University, Bozeman, MT, USA ]
Date: 2004
Abstract: This study presents evidence that slope aspect plays a significant role in the formation, size, type, and extent of surface hoar and near-surface faceted crystals. Experimental stations were placed on the north and south-facing aspects of Pioneer Mountain in southwest Montana to measure wind speed and direction, snow temperatures from 0.1m above the snow surface to 0.35m below the snow surface, incoming and outgoing shortwave radiation, and snow surface temperature. Each time a surface hoar or near-surface faceted crystal layer formed, snowpack and meteorological variables were gathered and snow crystals were collected, measured, characterized and photographed so that crystal size and structure could be compared between aspects. Persistent weak layers formed on January 9-10, 2004, and January 12-13, 2004. Results show a statistically significant difference in the size of surface hoar and near-surface faceted crystals based on slope aspect. During these two periods, better developed near-surface facets formed on south-facing slopes, while surface hoar crystals grew larger at the north-facing study site. These aspect dependent differences are important for assessing mountain range scale spatial variability and may also play a role at smaller scales due to subtle aspect changes. The results of this research may help us better understand some of the differences in weak layer formation on different aspects which, in turn, lead to different avalanche conditions.
Object ID: issw-2004-083-093.pdf
Language of Article: English
Presenter(s): Unknown
Keywords: avalanche, avalanche forecasting, large scale spatial variability, surface hoar, diurnally recrystalized near-surface faceted crystals, temperature and vapor pressure gradients
Page Number(s): 83-93
Subjects: avalanche forecasting surface hoar persistent weak layers
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