Cold Regions Science and Technology

Journal: Cold Regions Science and Technology

Abbreviation

Cold reg. sci. technol.

Publisher

Elsevier

ISSN

0165-232X
1872-7441

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Publications 1 - 10 of 38

A novel approach for bridging the gap between climate change scenarios and avalanche hazard indication mapping
Ortner, Gregor; Michel, Adrien; Spieler, Matthias B.A.; et al. (2025)
Cold Regions Science and Technology
The influence of climate change on snow avalanches, particularly for the end of this century, remains uncertain, underscoring the need for further research. To assess the possible consequences of potential changes in snow accumulation and temperature and their impact on avalanche hazard, we introduce a comprehensive multi-step framework. It includes the analysis of climate change scenarios as well as the modeling of future snow covers and the simulation of avalanches in a case study region in central Switzerland. Using a downscaling and a quantile mapping approach, we considered the high emission RCP8.5 from the CH2018 Swiss climate change scenarios and simulated a potential snow cover of more than 100 future winters with the snow cover model SNOWPACK. Changing snow accumulation and snow cover temperature was taken into account for two future time frames. The changed parameters were used in the RAMMS::EXTENDED avalanche simulation software on large scale. The results indicate that changes in snow accumulation and temperature have a considerable impact on the run-out of avalanches. The results strongly depend on the climate model, without a clear overall trend in snow accumulation across the selected model chains. Snow accumulation and layer temperature can increase or decrease. However, for snow cover temperature, an increase in the mean snow temperature, especially towards the end of the century, can be expected. In future scenarios with reduced snow accumulation and rising temperatures, avalanche simulations show a decrease in the affected area. The workflow from climate scenario analysis to avalanche hazard modeling serves as an initial method for estimating future avalanche extents in the context of climate change on a large scale and can be useful for achieving future protection and adaptation goals.
Snowpack response to directed gas explosions on level ground
Simioni, Stephan; Dual, Jürg; Schweizer, Jürg (2017)
Cold Regions Science and Technology
The artificial release of avalanches is an important mitigation measure in avalanche control. The explosion to trigger an avalanche is either produced by igniting solid (or liquid) explosives or a gas mixture. Whereas there have been several studies on the impact of explosives, there is little research on the effect of directed gas explosions on a snowpack. We performed experiments with a prototype gas exploder above snow and measured air pressure at different distances from the point of explosion and accelerations within the snowpack. By measuring along different directions from the point of explosion we assessed the lateral propagation of the pressure wave caused by the directed explosion. Air pressure decreased distinctly with distance from the point of explosion. For example, air pressure was about (6.0 ± 0.2) kPa at 20 m and (0.59 ± 0.02) kPa at 80 m with 1.8 kg of propane‑oxygen gas mixture. Within a forward cone of half angle of about 37°, the impact was independent of the direction from the exploder axis. Within the snowpack, accelerations decreased distinctly with depth and distance from the point of explosion as it is observed with explosives. The frequency content of the air pressure signal of the directed gas explosion was similar compared to experimental results previously obtained with solid explosives. We conclude that in the gas exploder axis, the impact of a directed gas explosion is comparable to an explosion with solid explosives with similar energy density. Hence, gas explosions are well suited to artificially trigger snow avalanches. In the future, side-by-side experiments will be needed to further analyze differences and similarities between the effect of gas and solid explosives. Moreover, additional measurements at operational gas exploders will allow further validation of the experimental results.
Multirotor UAV icing correlated to liquid water content measurements in natural supercooled clouds
Miller, Anna J.; Fuchs, Christopher; Omanovic, Nadja; et al. (2024)
Cold Regions Science and Technology
Atmospheric icing, the accumulation of ice on surfaces, is a severe concern for the aviation industry. Deicing and icing prediction tools are necessary for pilots to ensure flight safety, and while there is established technology for large aircraft icing, more research is needed for smaller uncrewed aerial vehicles (UAVs). Here, we present measurements from 59 flights of a multirotor UAV into wintertime low stratus clouds of temperatures between − 3 and − 10 ◦C. The UAV is equipped with rotor heating to allow flights up to 10 min in icing conditions. Icing severity was quantified by using the rate of increase in battery current during icing, and was then compared with simultaneous, co-located measurements of liquid water content (LWC). LWC measurements were (a) calculated from cloud droplets measured with an in situ holographic imager on a tethered balloon system and (b) retrieved from remote sensing observations (microwave radiometer, ceilometer, cloud radar). We show that, for these environmental conditions, icing was strongly positively correlated to LWC over an LWC range of 0.02 to 0.5 g m− 3 , independent of temperature and mean droplet size, though droplets > 50 μm in diameter may contribute to increased icing severity. We also show that the LWC retrieved from remote sensing agrees well with the in situ measurements, indicating that remote sensing measurements can effectively be used to assess icing conditions. These are the first known measurements of multirotor UAV icing with co-located LWC measurements in natural clouds.
Hazard mapping for ice and combined snow/ice avalanches - two case studies from the Swiss and Italian Alps
Margreth, Stefan; Funk, Martin (1999)
Cold Regions Science and Technology
In September 1996, 210,000 m3 of glacier ice broke off from the Gutzgletscher which is situated in the north-west face of the Wetterhorn above Grindelwald (Bernese Alps, Switzerland). The ice masses dropped down the 1000-m high rock face and formed two huge powder avalanches. The avalanche debris blocked a road and the air pressure injured three people. The avalanche history of the Gutzgletscher is well-documented. The second case study we describe is situated below the top of the Grandes Jorasses in the Italian part of the Mont Blanc Massif. In January 1997, a part of the hanging glacier broke off. The time of the event was predicted by displacement measurements at the front of the hanging glacier. Below the hanging glacier, there are huge starting zones for snow avalanches. Because the break-off was expected during a period with considerable avalanche hazard, it was assumed that the ice masses could release big snow avalanches. For that reason, we proposed to evacuate the valley below the hanging glacier. The breaking off occurred a few days after the important snowfall, so that the snowpack had stabilized and no snow avalanches were observed. There were no damages. For both cases, the Swiss Federal Institute for Snow and Avalanche Research (SLF) prepared hazard maps and worked out corresponding safety plans in collaboration with the Laboratory for Hydraulics, Hydrology and Glaciology (VAW). The main principles and difficulties of hazard assessment for ice avalanches are described based on the two case studies.
Field measurements of snowpack response to explosive loading
Simioni, Stephan; Sidler, Rolf; Dual, Jürg; et al. (2015)
Cold Regions Science and Technology
Avalanche control by explosives is among the key temporary preventive measures. Hitherto, little is known about wave propagation in a snowpack caused by an explosion. During the winter 2013–2014 we performed field experiments on a flat study site. We triggered slurry explosive charges at different heights above the snow surface. At three different distances from the point of explosion we measured surface air pressure and accelerations of the snowpack at various depths. Cameras were placed in the snow pits for recording weak layer failure and crack propagation. We report empirical relations for the decay of near-surface air pressure, accelerations, displacement velocities and displacement with distance from the explosion and depth within the snowpack. Waves within the snowpack arrived earlier at the sensors than the corresponding air pressure waves at the microphones. Air pressure decayed stronger than accelerations within the snowpack. Weak layer failure mainly happened in the top part of the snowpack. We observed two types of weak layer failure, one caused by the direct impact of the air pressure wave close to the point of observation, the other by failure induced by the air pressure wave closer to the point of explosion and subsequent crack propagation. Our measurements increase the understanding of acoustic wave propagation in snow and can be used for comparison with numerical simulations.
Speed and attenuation of acoustic waves in snow: Laboratory experiments and modeling with Biot's theory
Capelli, Achille; Kapil, Jagdish C.; Reiweger, Ingrid; et al. (2016)
Cold Regions Science and Technology
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 across cylindrical snow samples with varying density (240–450 kg m− 3). We deduced the acoustic attenuation coefficient within snow by performing experiments with different column lengths to eliminate possible influences of the snow-sensor coupling. The attenuation coefficient was measured for the entire burst signal and for single frequency components in the range of 8 to 35 kHz. The acoustic wave propagation speed, calculated from the travel time of the acoustic signal, varied between 300 m s− 1 and 950 m s− 1, depending on the density and hardness of snow. From the sound speed we also estimated the Young's modulus of our snow samples; the values of the modulus ranged from 30 to 340 MPa for densities between 240 and 450 kg m− 3. In addition, we modeled the sound propagation for our experimental setup using Biot's model for wave propagation in a porous medium. The model results were in good agreement with our experimental results and suggest that our acoustic signals consisted of Biot's slow and fast waves. Our results can be used to improve the identification and localization of acoustic emission sources within snow in view of assessing snow slope instability.
Load-controlled test apparatus for snow
Reiweger, Ingrid; Schweizer, Jürg; Ernst, Robert; et al. (2010)
Cold Regions Science and Technology
Natural dry-snow slab avalanches start with a failure at a weak snow layer. In order to understand the mechanical behaviour and the failure mechanism, we designed an experimental setup to perform loading experiments with homogeneous and layered snow samples under controlled conditions in a cold laboratory. We here present our loading apparatus where the snow sample can be tilted by a “slope angle” and is loaded by an increasing weight analogous to a snowfall. The force and the global displacement are measured with a force and two displacement sensors, respectively. The local displacement can be computed with a particle image velocimetry algorithm (PIV). Additionally, we record acoustic emissions (AE) to monitor the damage (breaking of bonds) in the snow sample before catastrophic failure. To demonstrate the capability of the system we present preliminary results with both homogeneous and layered snow samples. The AE count rate increased before fracture, as the samples progressively weakened. For the layered samples we measured a concentration of strain within the weak layer.
Influence of snowpack layering on human-triggered snow slab avalanche release
Habermann, Marijke; Schweizer, Jurg; Jamieson, J. Bruce (2008)
Cold Regions Science and Technology
Evaluating methods to estimate the water equivalent of new snow from daily snow depth recordings
Magnusson, Jan; Cluzet, Bertrand; Quéno, Louis; et al. (2025)
Cold Regions Science and Technology
The water equivalent of new snow (HNW) plays a crucial role in various fields, including hydrological modeling, avalanche forecasting, and assessing snow loads on structures. However, in contrast to snow depth (HS), obtaining HNW measurements is challenging as well as time-consuming and is hence rarely measured. Therefore, we assess the reliability of two semi-empirical methods, HS2SWE and ΔSNOW, for estimating HNW. These methods are designed to simulate continuous water equivalent of the snowpack (SWE) from daily HS only, with changes in SWE yielding daily HNW estimates. We compare both parametric methods against HNW predictions from a physics-based snow model (FSM2oshd) that integrates daily HS recordings using data assimilation. Our findings reveal that all methods exhibit similar performance, with relative biases of less than ∼3 % in replicating SWE observations commonly used for model evaluations. However, the ΔSNOW model tends to underestimate daily HNW by ∼17 %, whereas HS2SWE and FSM2oshd combined with a particle filter data assimilation scheme provide nearly unbiased estimates, with relative biases below ∼5 %. In contrast to the parsimonious parametric methods, we show that the physics-based approach can yield information about unobserved variables, such as total solid precipitation amounts, that may differ from HNW due to concurrent melt. Overall, our results underscore the potential of utilizing commonly available daily HS data in conjunction with appropriate modeling techniques to provide valuable insights into snow accumulation processes. Our study demonstrates that daily SWE observations or supplementary measurements like HNW are important for validating the day-to-day accuracy of simulations and should ideally already be incorporated during the calibration and development of models.
Feasibility study of a system for airborne detection of avalanche victims with ground penetrating radar and a possible automatic location algorithm
Heilig, Achim; Schneebeli, Martin; Fellin, Wolfgang (2008)
Cold Regions Science and Technology

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