Whether avalanche release is likely largely depends on snow layering, in particular the complex interaction between slab layers and a so-called weak layer ( Schweizer et al., 2008). Each year, around 100 avalanche fatalities occur in the European Alps ( Techel et al., 2016). Snow slab avalanches are hazardous and can threaten people and infrastructure. The improved parameterization of critical crack length may be useful for both weak layer detection in simulated snow stratigraphy and also providing more realistic snow stability information – and hence may improve avalanche forecasting. Hence, minimal values in modeled critical crack length better match observed weak layers. In turn, critical weak layers appear more prominently in the vertical profile of critical crack length simulated with SNOWPACK.

With these adjustments, the normalized root-mean-square error between modeled and observed critical crack lengths decreased from 1.80 to 0.28.Īs the improved parameterization accounts for grain size, values of critical crack lengths for snow layers consisting of small grains, which in general are not weak layers, become larger. Hence, we replaced two variables of the original parameterization, namely the weak layer shear modulus and thickness, with a fit factor depending on weak layer density and grain size. Comparing modeled to measured critical crack length showed some discrepancies stemming from model assumption. We monitored seven distinct weak layers and performed in total 157 propagation saw tests on a weekly basis. To validate and improve the parameterization for the critical crack length, we used data from 3 years of field experiments performed close to two automatic weather stations above Davos, Switzerland. The critical crack length can also be measured in the field with a propagation saw test, which allows for an unambiguous comparison. Recently, a new stability criterion relating to crack propagation, namely the critical crack length, was implemented into the snow cover model SNOWPACK. To evaluate snow stability, failure initiation and crack propagation have to be considered. Such observations are rare and snow cover models can improve the spatial and temporal resolution. Observed snow stratigraphy and snow stability are of key importance for avalanche forecasting.

Crystal Impact Match 2 Crack