Christine Pielmeier

Swiss Federal Institute for Forest, Snow and Landscape Research

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Martin Schneebeli

Swiss Federal Institute for Forest, Snow and Landscape Research

Frank Techel

University of Zurich

Hans‐Peter Marshall

Boise State University

Benjamin Zweifel

Swiss Federal Institute for Forest, Snow and Landscape Research

Jürg Schweizer

Center for Snow and Avalanche Studies

Thomas Stucki

Swiss Federal Institute for Forest, Snow and Landscape Research

Christoph Marty

Center for Snow and Avalanche Studies

Sascha Bellaire

University of Calgary

Andreas Wiesmann

Gamma Remote Sensing (Switzerland)

Yves Bühler

Swiss Federal Institute for Forest, Snow and Landscape Research

Cooperative Institutions

Swiss Federal Institute for Forest, Snow and Landscape Research

Center for Snow and Avalanche Studies

ETH Zurich

École Polytechnique Fédérale de Lausanne

University of Zurich

Gamma Remote Sensing (Switzerland)

University of Bern

Cold Regions Research and Engineering Laboratory

Montana State University

Norwegian Geotechnical Institute

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Stability algorithm for snow micro-penetrometer measurements

Journal of Glaciology (2009)

Sascha Bellaire Christine Pielmeier Martin Schneebeli Jürg Schweizer

Abstract Information on snow-cover stability is important for predicting avalanche danger. Traditionally, stability evaluation is based on manual observations of snow stratigraphy and stability tests, which are time-consuming. The SnowMicroPen (SMP) is a high-resolution, constant-speed penetrometer to measure penetration resistance. We have analysed the resistance signal to derive snow stability. The proposed stability algorithm was developed by comparing 68 SMP force–distance profiles with the corresponding manual profiles, including stability tests. The algorithm identifies a set of four potentially weak layers by taking into account changes in structure and rupture strength of microstructural elements that make up snow layers as derived from the SMP signal. In 90% of the cases, one of the four potentially weak layers proposed by the algorithm coincided with the failure layer observed in the stability test. To select the critical layer from the four potential weaknesses was more difficult. With fully automatic picking of the critical layer, agreement with the failure layer observed in the stability test was reached in 60% of the cases. To derive a stability classification, we analysed weak-layer as well as slab properties. These predictor variables allow the SMP signal to be classified into two stability classes, poor and fair-to-good, with an accuracy of ∼75% when compared with observed stability. The SMP, in combination with the proposed algorithm, shows high potential for providing snow-cover stability information at high resolution in time and space.

Penetrometer

10.3189/002214309790152582

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Citations (25)

Snow Microstructure

Encyclopedia of earth sciences series/Encyclopedia of earth sciences (2011)

Christine Pielmeier

10.1007/978-90-481-2642-2_525

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Citations (0)

Preliminary characterization of Alpine snow using SnowMicroPen

Cold Regions Science and Technology (2008)

P.K. Satyawali Martin Schneebeli Christine Pielmeier Thomas Stucki Akhilendra Singh

Snowpack

Penetrometer

Snow field

10.1016/j.coldregions.2008.09.003

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Citations (34)

Measuring Snow Profiles with High Resolution: Interpretation of the Force-Distance Signal from a Snow Micro Penetrometer

Christine Pielmeier Martin Schneebeli

Penetrometer

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Wet Snow Diurnal Evolution and Stability Assessment

International Snow Science Workshop, Davos 2009, Proceedings (2009)

Frank Techel Christine Pielmeier

Wet snow avalanches pose a threat to snow recreationists and to infrastructure such as mountain roads. The timing of wet snow avalanche formation is difficult to predict. The loss of strength is more important than stress imposed by additional loads. Processes leading to weakening, such as water infiltration can be gradual or sudden. Therefore, the time scale of observations is essential. A questionnaire among 40 international avalanche professionals aimed at determining common practice in assessing wet snow stability during first and repeated wetting events. It turns out that only few respondents use different stability tests for dry and wet snow. 14 respondents consider tests in wet snow useful. In view of the responses, we sampled 35 locations during first and repeated wetting cycles in the Swiss Alps. We compare the results of one rutschblock test (RB), four extended column tests (ECT) and two shovel shear tests from the morning and the afternoon. Additionally, vertical liquid water content profiles and snow profiles are analyzed. Moist and very soft persistent weak layers most often produce unstable test results, where the failure character is a collapse. Observed ponding horizons did not produce failures in the tests. As in dry snow, the RB is comparable to the ECT in wet and moist snow. The influence of surface melt-freeze crust is investigated by comparing ECT fracture propagation with a modified version of the ECT, where the surface melt-freeze crust is removed. A procedure to assess deep, wet snow instabilities is suggested.

Ponding

Infiltration (HVAC)

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Citations (16)

Continuous monitoring of snowpack displacement at high spatial and temporal resolution with terrestrial radar interferometry

Geophysical Research Letters (2015)

Rafael Caduff Andreas Wiesmann Yves Bühler Christine Pielmeier

Abstract Terrestrial radar interferometry is used in geotechnical applications for monitoring hazardous Earth or rock movements. In this study, we use it to continuously monitor snowpack displacements. As test site, the Dorfberg slope at Davos, Switzerland, was measured continuously during March 2014. The line of sight displacement was retrieved at a spatial resolution of millimeter to centimeter and a temporal resolution of up to 1 min independent of visibility. The results reveal several temperature‐driven diurnal acceleration and deceleration cycles. The initiation of a small full‐depth glide avalanche was observed after 50 cm total differential displacement. The maximum measured displacement of another differential glide area reached 43 cm/h without resulting in a full‐depth avalanche even after a total measured differential displacement of 4.5 m. In regard of the difficulty to predict full‐depth glide avalanches on the regional scale, the presented method has big potential for operational snow glide monitoring on critical slopes.

Snowpack

Temporal resolution

Visibility

10.1002/2014gl062442

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Citations (17)

All-weather avalanche activity monitoring from space?

International Snow Science Workshop 2014 Proceedings, Banff, Canada (2014)

Yves Bühler Claudia Bieler Christine Pielmeier Andreas Wiesmann Rafael Caduff

Information on avalanche activity or non-activity on local and regional scale is of great value for avalanche warning services, traffic authorities and experts responsible for safety in communities or ski resorts. In particular during bad weather condition, such information is available only very limited or not at all. The aim of the ESA IAP feasibility study Improved Alpine Avalanche Forecast Service was to investigate existing technology to overcome this gap. Of particular interest were radar-based techniques that have the potential to operate independently of daylight and weather conditions. For testing the observation of avalanche activity on a local scale, a terrestrial radar was installed at the WSL Institute for Snow and Avalanche Research SLF, illuminating the Dorfberg close to Davos, Switzerland during winter 2013/2014. On that slope, frequent natural as well as artificially triggered avalanches can be expected. The system acquired datasets at minute temporal resolution, which allows the production of coherence maps to detect avalanche events and also features such as snow creep and free-riders tracks. The spatial coverage of the terrestrial system was 6 km 2 for this experiment. On the regional scale, data from radar satellites with very high spatial resolution (< 3 m) were analyzed. A TerraSAR-X stripmap mode satellite frame, for example, covers 1500 km 2 and has a temporal resolution of 11 days. A combination of terrestrial and space-borne radar sensors could be a powerful tool to map avalanche activity for different scales during any weather condition. We present first results of terrestrial and space-borne avalanche activity mapping at Davos during the winter 2013/2014 and discuss capabilities and limitations for local and regional avalanche warning services.

Weather radar

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Citations (6)

Wetter, Schneedecke und Lawinengefahr in den Schweizer Alpen. Hydrologisches Jahr 2016/17

Christine Pielmeier Benjamin Zweifel Christoph Marty Frank Techel

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Citations (2)

Evaluating and improving the stability predictions of the snow cover model SNOWPACK

Cold Regions Science and Technology (2006)

Jürg Schweizer Sascha Bellaire Charles Fierz Michael Lehning Christine Pielmeier

Snowpack

10.1016/j.coldregions.2006.05.007

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Citations (101)

Snow stratigraphy measured by snow hardness and compared to surface section images

2002 International Snow Science Workshop, Penticton, British Columbia (2002)

Christine Pielmeier Martin Schneebeli

Snow hardness is one of the most important parameters in the study of snow. Hand, ram and micro penetrometer hardness measurements were taken in seven snow pits. The snow profiles are analysed in terms of the three hardness tests and surface section images are used as an objective reference. From the images we established the stratigraphy in terms of layers and layer boundaries at high spatial resolution and compared the stratigraphy to the hardness profiles. The hand hardness test captured 80 % of all layers and layer boundaries and the ram hardness test 60 %. The micro penetrometer captured the stratigraphy more complete than hand and ram profiles. The hand and ram profiles are a generalization of the effective snow hardness and stratigraphy. Important details are missed, for example thin hard and soft layers which are highly relevant to avalanche formation. Differences in soft snow are resolved by the micro penetrometer, which is problematic or impossible with hand and ram tests. The surface sections and micro penetrometer profile show a much more stratified snowpack than revealed in a classical snow profile. Quantitative evaluation of mechanical and textural snowpack properties requires methods that have a spatial resolution of at least 1 mm. Since the main heat and mass fluxes are perpendicular to the snow surface, the much stronger stratification now revealed has a large impact on vapour transport. Electromagnetic models (microwave emission and radar), hydrology (water flow), avalanche formation (metamorphism in thin layers) are examples where a highly resolved snowpack stratigraphy will be important.

Snowpack

Penetrometer

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Citations (12)