Assessing wet snow avalanche activity using detailed physics based snowpack simulations

Wever, Nander; Valero, César Vera; Fierz, Charles

doi:10.1002/2016gl068428

Cited by 47 publications

(54 citation statements)

References 42 publications

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“…LWC increases with depth in the upper layer, it presents a marked peak at the textural boundary, and it decreases again below the capillary barrier. Peaks in LWC at the interface may be associated with capillary barriers as water ponds until ψ reaches ψ WE and the underlying layer becomes conductive (Stormont and Anderson, 1999) (2015b), and Wever et al (2015Wever et al ( , 2016. All FC-FM samples yield a similar LWC in the upper layer at the interface: ∼ 33 vol % in FC samples and ∼ 34-36 vol % in FM samples.…”

Section: Development Of Capillary Barriersmentioning

confidence: 86%

“…Furthermore, capillary barriers can play an important role for triggering wet snow avalanches (Mitterer et al, 2011;Wever et al, 2016). For example, Wever et al (2016) report that predicted local accumulations of water like those expected during ponding at capillary barriers can be used to separate avalanche from non-avalanche days. The position of peak LWC within the snow cover correlates with avalanche size.…”

Section: F Avanzi Et Al: Capillary Barriers In Snowmentioning

confidence: 99%

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Observations of capillary barriers and preferential flow in layered snow during cold laboratory experiments

et al. 2016

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Abstract. Data of liquid water flow around a capillary barrier in snow are still limited. To gain insight into this process, we carried out observations of dyed water infiltration in layered snow at 0 • C during cold laboratory experiments. We considered three different finer-over-coarser textures and three different water input rates. By means of visual inspection, horizontal sectioning, and measurements of liquid water content (LWC), capillary barriers and associated preferential flow were characterized. The flow dynamics of each sample were also simulated solving the Richards equation within the 1-D multi-layer physically based snow cover model SNOW-PACK. Results revealed that capillary barriers and preferential flow are relevant processes ruling the speed of water infiltration in stratified snow. Both are marked by a high degree of spatial variability at centimeter scale and complex 3-D patterns. During unsteady percolation of water, observed peaks in bulk volumetric LWC at the interface reached ∼ 33-36 vol % when the upper layer was composed by fine snow (grain size smaller than 0.5 mm). However, LWC might locally be greater due to the observed heterogeneity in the process. Spatial variability in water transmission increases with grain size, whereas we did not observe a systematic dependency on water input rate for samples containing fine snow. The comparison between observed and simulated LWC profiles revealed that the implementation of the Richards equation reproduces the existence of a capillary barrier for all observed cases and yields a good agreement with observed peaks in LWC at the interface between layers.

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Section: Development Of Capillary Barriersmentioning

confidence: 86%

Section: F Avanzi Et Al: Capillary Barriers In Snowmentioning

confidence: 99%

Observations of capillary barriers and preferential flow in layered snow during cold laboratory experiments

et al. 2016

View full text Add to dashboard Cite

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“…More important than the linear distance is the difference in altitude. The small elevation difference between the release zones and the weather stations, (see Table 1), provides the sufficient conditions to apply snowcover models to estimate the initial and boundary conditions of the case studies Wever et al, 2016).…”

Section: Snowpack Simulationsmentioning

confidence: 99%

“…We apply the SNOWPACK model Lehning et al, 2002;Wever et al, 2014) in a similar setup as the snow-height driven simulations in Wever et al (2015Wever et al ( , 2016. Because SNOWPACK is a one-dimensional model, we must transfer point simulation results to the slope in order to apply a three-dimensional avalanche dynamics model.…”

Section: Snowpack Simulationsmentioning

confidence: 99%

“…The vertical liquid water distribution typically exhibited a thin layer with high LWC located near layer boundaries (capillary barriers), which supports the 605 assumption in the avalanche model that the liquid water is concentrated at the sliding surface. The results of the snowcover simulations were visually inspected to determine the avalanche fracture depth (following Wever et al (2016)). This depth could be verified by the observations of the actual release zone.…”

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confidence: 99%

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Modeling the influence of snowcover temperature and water content on wet snow avalanche runout

Valero¹,

Wever²,

Christen³

et al. 2017

Preprint

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Abstract. Snow avalanche motion is strongly dependent on the temperature and water content of the snowcover. In this paper we use a snowcover model, driven by measured meteorological data, to set the initial and boundary conditions for wet snow avalanche calculations. The snowcover model provides estimates of snow depth, density, temperature and liquid water content. This information is used to prescribe fracture heights and erosion depths for an avalanche dynamics model. We 5 compare simulated runout distances with observed avalanche deposition fields using a contingency table analysis. Our analysis of the simulations reveals a large variability in predicted runout for tracks with flat terraces and gradual slope transitions to the runout zone. Reliable estimates of avalanche mass (height and density) in the release and erosion zones is identified to be more important than an exact specification of temperature and water content. For wet snow avalanches, this implies that the 10 layers where meltwater accumulates in the release zone must be identified accurately as this defines the height of the fracture slab and therefore the release mass. This is an interesting result because it indicates the critical role of fracture depth as an input parameter in avalanche simulations. Advanced thermomechanical models appear to be better suited than existing guideline procedure to simulate wet snow avalanches when accurate snowcover information is available.

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Early formation of preferential flow in a homogeneous snowpack observed by micro‐CT

Avanzi

Petrucci

Matzl³

et al. 2017

Water Resources Research

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We performed X‐ray microtomographic observations of wet‐snow metamorphism during controlled continuous melting and melt‐freeze events in the laboratory. Three blocks of snow were sieved into boxes and subjected to cyclic, superficial heating or heating‐cooling to reproduce vertical water infiltration patterns in snow similarly to natural conditions. Periodically, samples were taken at different heights and scanned. Results suggest that wet‐snow metamorphism dynamics are highly heterogeneous even in an initially homogeneous snowpack. Consistent with previous work, we observed an increase with time in the thickness of the ice structure, which is a measure of grain size. However, this was coupled with large temporal scatter between consecutive measurements of the specific surface area and of the statistical moments of grain thickness distributions. Because of marked differences in the right tail, grain thickness distributions did not show shape invariance with time, contrary to previous analyses. In our experiments, wet‐snow metamorphism showed two strikingly different patterns: homogeneous coarsening superimposed by faster heterogeneous coarsening in areas that were affected by preferential percolation of water. Liquid water movement in snow and fast structural evolution may be thus intrinsically coupled by early formation of preferential flow at local scale. These observations suggest that further experiments are highly needed to fully understand wet‐snow metamorphism and infiltration patterns in a natural snowpack.

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Assessing wet snow avalanche activity using detailed physics based snowpack simulations

Cited by 47 publications

References 42 publications

Observations of capillary barriers and preferential flow in layered snow during cold laboratory experiments

Observations of capillary barriers and preferential flow in layered snow during cold laboratory experiments

Modeling the influence of snowcover temperature and water content on wet snow avalanche runout

Early formation of preferential flow in a homogeneous snowpack observed by micro‐CT

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