Achille Capelli

University of Alaska Fairbanks · Geophysical Institute

Infrasound monitoring of geophysical and human-sourced activity, such as explosions, eruptions, earthquakes, and avalanches, may be impacted by burial of sensors in a snowpack. We studied the frequency-dependent attenuation of sound, vertical sound speed, and wind noise reduction in a natural snowpack using earthquakes as a natural source of infras...

In a changing arctic environment transitioning from perennial to seasonal ice measuring sea ice thickness and snow cover depth is fundamental for understanding the present and future state of the ice cover and polar marine environment. Changing ice conditions are moreover a challenge for the traditional uses of sea ice as travel and subsistence hun...

Snow water equivalent (SWE) can be measured using low-cost Global Navigation Satellite System (GNSS) sensors with one antenna placed below the snowpack and another one serving as a reference above the snow. The underlying GNSS signal-based algorithm for SWE determination for dry- and wet-snow conditions processes the carrier phases and signal stren...

Snow water equivalent (SWE) can be measured using low-cost Global Navigation Satellite System (GNSS) sensors with one antenna placed below the snowpack and another one serving as a reference above the snow. The underlying GNSS signal-based algorithm for SWE determination for dry- and wet-snow conditions processes the carrier phases and signal stren...

Snow is a highly porous material with properties that may strongly differ depending on the environmental conditions. On slopes, the layered snowpack may fail and avalanches occur. Hence, knowing how snow deforms and fails is essential for understanding and modeling snow avalanche release and flow. The response of snow to imposed load or deformation...

The water stored in the snowpack is a crucial contribution to the hydrological cycle in mountain areas. Estimating the spatial distribution and temporal evolution of snow water equivalent (SWE) in mountain regions is, therefore, a key question in snow hydrology research. For this reason, direct measurements of SWE are still essential, but they are...

Dry-snow slab avalanches start with the formation of a local failure in a highly porous weak layer underlying a cohesive snow slab. If followed by rapid crack propagation within the weak layer and finally a tensile fracture through the slab, a slab avalanche releases. While the basic concepts of avalanche release are relatively well understood, per...

For various (snow)hydrological applications like water availability, hydropower generation and flood forecasts, information on snow water equivalent (SWE) and further snow cover properties is essential. Since a few decades, the use of GNSS (Global Navigation Satellite System) signals for the derivation of snow cover properties is increasing. For se...

Continuous information on snow cover properties is very important for various hydrological applications and forecasts of natural risks like avalanches and floods. Moreover, in situ measured snow data are requested for the validation of models and remote sensing products. However, they are often scarce, labor-intense, expensive, or invasive. During...

Snow failure is the result of gradual damage accumulation culminating in macroscopic cracks. The failure type strongly depends on the rate of the applied load or strain. Our aim was to study the microstructural mechanisms leading to the macroscopic loading rate dependence. We modeled snow failure and the concurrent acoustic emissions for different...

Dry-snow slab avalanches start with the formation of a local failure in a highly porous weak layer underlying a cohesive snow slab. If followed by rapid crack propagation within the weak layer and finally a tensile fracture through the slab appears, a slab avalanche releases. While the basic concepts of avalanche release are relatively well underst...

Snow water equivalent (SWE) is a key property of the seasonal snow cover. The water stored in the snowpack is a crucial contribution to the hydrological cycle in mountain areas. Estimating the spatial distribution and temporal evolution of SWE in mountain region is currently considered as one of the most important unsolved problems in snow hydrolog...

Improving the prediction of snow avalanches requires a detailed understanding of the fracture behavior of snow as dry-snow slab avalanche release is a multi-scale fracture process. In principle, avalanches start with the formation of a localized failure in a highly porous weak snow layer underlying a cohesive snow slab, which can be followed by rap...

Snow is a heterogeneous material with strain- and/or load-rate-dependent strength. In particular, a transition from ductile-to-brittle failure behavior with increasing load rate is observed. The rate-dependent behavior can partly be explained with the existence of a unique healing mechanism in snow that stems from its high homologous temperature (t...

Snow slab avalanches are caused by cracks forming and propagating in a weak snow layer below a cohesive slab. The gradual damage process leading to the formation of the initial failure within the weak layer (WL) is still not entirely understood. To this end, we designed a novel test apparatus that allows performing loading experiments with large sn...

Snow is a heterogeneous material with strain/load rate dependent strength. In particular, a transition from duc-tile to brittle failure behavior with increasing loading rate is observed. The rate dependent behavior can partly be explained with the existence of a unique healing mechanism in snow that stems from its high homologous temperature. As so...

Snow is a heterogeneous material with strain/load rate dependent strength. In particular, a transition from brittle to ductile failure at low loading rates is observed. The rate dependent behavior can partly be explained with the existence of a unique healing mechanism in snow. As soon as broken elements in the ice matrix get in contact, they start...

Digital cone penetration measurements can be used to infer snow mechanical properties, for instance to study snow avalanche formation. The standard interpretation of these measurements is based on statistically inferred micromechanical interactions between snow microstructural elements and a well-calibrated penetrating cone. We propose an alternati...

Slab avalanches are caused by a crack forming and propagating in a weak layer within the snow cover, which eventually causes the detachment of the overlying cohesive slab. The gradual damage process leading to the nucleation of the initial failure is still not entirely understood. Therefore, we studied the damage process preceding snow failure by a...

Acoustic emissions generated by crack formation or bond failure allow a non-destructive observation of the progressive failure of snow. Moreover, acoustic emission features often indicate imminent failure. We developed a new apparatus for fully load-controlled snow failure experiments. Our apparatus includes six piezoelectric transducers which reco...

We developed a new apparatus for fully load-controlled snow failure experiments. The deformation and applied load are measured with two displacement and two force sensors, respectively. The loading experiments are recorded with a high speed camera, and the local strain is derived by a particle image velocimetry (PIV) algorithm. To monitor the progr...

Monitoring acoustic emissions (AE) prior to imminent failure is considered a promising technique for assessing snow slope instability. Gaps in elastic wave propagation characteristics in snow hinder quantitative interpretation of AE signals. Our study focuses on characterizing the propagation of acoustic reference signals in the ultrasonic range ac...

Acoustic emission analysis is a promising technique for monitoring snow slope stability with potential for application in early warning systems for avalanches. Current research efforts focus on identification and localization of acoustic emission features preceding snow failure and avalanches. However, our knowledge of sound propagation characteris...

We present real-time detection measurements of electron tunneling in a graphene quantum dot. By counting single electron charging events on the dot, the tunneling process in a graphene constriction and the role of localized states are studied in detail. In the regime of low charge detector bias we see only a single time-dependent process in the tun...