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| Titel |
A process-based approach to estimate point snow instability |
| VerfasserIn |
B. Reuter, J. Schweizer, A. van Herwijnen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 9, no. 3 ; Nr. 9, no. 3 (2015-05-04), S.837-847 |
| Datensatznummer |
250116788
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| Publikation (Nr.) |
 copernicus.org/tc-9-837-2015.pdf |
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| Zusammenfassung |
| Snow instability data provide
information about the mechanical state of the snow cover and are essential
for forecasting snow avalanches. So far, direct observations of instability
(recent avalanches, shooting cracks or whumpf sounds) are complemented with
field tests such as the rutschblock test, since no measurement method for
instability exists. We propose a new approach based on snow mechanical
properties derived from the snow micro-penetrometer that takes into account
the two essential processes during dry-snow avalanche release: failure
initiation and crack propagation. To estimate the propensity of failure
initiation we define a stress-based failure criterion, whereas the propensity
of crack propagation is described by the critical cut length as obtained with
a propagation saw test. The input parameters include layer thickness, snow
density, effective elastic modulus, strength and specific fracture energy of
the weak layer – all derived from the penetration-force signal acquired with
the snow micro-penetrometer. Both instability measures were validated with
independent field data and correlated well with results from field tests.
Comparisons with observed signs of instability clearly indicated that a
snowpack is only prone to avalanche if the two separate conditions for
failure initiation and crack propagation are fulfilled. To our knowledge,
this is the first time that an objective method for estimating snow
instability has been proposed. The approach can either be used directly based
on field measurements with the snow micro-penetrometer, or be implemented in
numerical snow cover models. With an objective measure of instability at
hand, the problem of spatial variations of instability and its causes can now
be tackled. |
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