Comparison of avalanche-velocity measurements by means of pulsed Doppler radar, continuous wave radar and optical methods

Rammer, Lambert; Kern, M.; Gruber, Urs; Tiefenbacher, F.

doi:10.1016/j.coldregions.2007.03.014

Cited by 36 publications

(24 citation statements)

References 7 publications

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“…Unlike Doppler radars (Rammer et al, 2007;Vriend et al, 2013), which target a specific single avalanche path, infrasound array analysis can be applied to multiple paths covering large areas around the array, with a resolution depending on the relative position of the array and the avalanche path (Fig. 4).…”

Section: Discussionmentioning

confidence: 99%

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Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system

Marchetti

Ripepe

Ulivieri³

et al. 2015

Nat. Hazards Earth Syst. Sci.

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Abstract. Avalanche risk management is strongly related to the ability to identify and timely report the occurrence of snow avalanches. Infrasound has been applied to avalanche research and monitoring for the last 20 years but it never turned into an operational tool to identify clear signals related to avalanches. We present here a method based on the analysis of infrasound signals recorded by a small aperture array in Ischgl (Austria), which provides a significant improvement to overcome this limit. The method is based on array-derived wave parameters, such as back azimuth and apparent velocity. The method defines threshold criteria for automatic avalanche identification by considering avalanches as a moving source of infrasound. We validate the efficiency of the automatic infrasound detection with continuous observations with Doppler radar and we show how the velocity of a snow avalanche in any given path around the array can be efficiently derived. Our results indicate that a proper infrasound array analysis allows a robust, real-time, remote detection of snow avalanches that is able to provide the number and the time of occurrence of snow avalanches occurring all around the array, which represent key information for a proper validation of avalanche forecast models and risk management in a given area.

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Section: Discussionmentioning

confidence: 99%

“…Videogrammetry (e.g., Vallet et al, 2004) and radars (e.g., Rammer et al, 2007;Vriend et al, 2013) are among the most common geophysical methods to detect snow avalanches. They measure directly the physical characteristics of an avalanche front but are limited to single paths analysis.…”

Section: Introductionmentioning

confidence: 99%

Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system

Marchetti

Ripepe

Ulivieri³

et al. 2015

Nat. Hazards Earth Syst. Sci.

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“…The radar can see denser parts of the flow-like granules and snow clumps which have an extent larger than the radar wavelength [Salm and Gubler, 1985;Rammer et al, 2007]. Such blocks occur in the frontal intermittent region (Figure 1a) as well as in the dense core.…”

Section: Geodarmentioning

confidence: 99%

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

Köhler¹,

McElwaine

Sovilla³

et al. 2016

JGR Earth Surface

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Five avalanches were artificially released at the Vallée de la Sionne test site in the west of Switzerland on 3 February 2015 and recorded by the GEOphysical flow dynamics using pulsed Doppler radAR Mark 3 radar system. The radar beam penetrates the dilute powder cloud and measures reflections from the underlying denser avalanche features allowing the tracking of the flow at 111 Hz with 0.75 m downslope resolution. The data show that the avalanches contain many internal surges. The large or “major” surges originate from the secondary release of slabs. These slabs can each contain more mass than the initial release, and thus can greatly affect the flow dynamics, by unevenly distributing the mass. The small or “minor” surges appear to be a roll wave‐like instability, and these can greatly influence the front dynamics as they can repeatedly overtake the leading edge. We analyzed the friction acting on the fronts of minor surges using a Voellmy‐like, simple one‐dimensional model with frictional resistance and velocity‐squared drag. This model fits the data of the overall velocity, but it cannot capture the dynamics and especially the slowing of the minor surges, which requires dramatically varying effective friction. Our findings suggest that current avalanche models based on Voellmy‐like friction laws do not accurately describe the physics of the intermittent frontal region of large mixed avalanches. We suggest that these data can only be explained by changes in the snow surface, such as the entrainment of the upper snow layers and the smoothing by earlier flow fronts.

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“…The PDR data were used to obtain the speed profile of Avalanche 1. A detailed explanation of the radar system is given in Rammer et al (2007). The measurement system is started automatically by seismic triggering whenever natural avalanches are released within the avalanche path.…”

Section: Test Site and Instrumentationmentioning

confidence: 99%

On the complementariness of infrasound and seismic sensors for monitoring snow avalanches

Kogelnig

Suriñach

Vilajosana

et al. 2011

Nat. Hazards Earth Syst. Sci.

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Abstract. The paper analyses and compares infrasonic and seismic data from snow avalanches monitored at the Vallée de la Sionne test site in Switzerland from 2009 to 2010. Using a combination of seismic and infrasound sensors, it is possible not only to detect a snow avalanche but also to distinguish between the different flow regimes and to analyse duration, average speed (for sections of the avalanche path) and avalanche size. Different sensitiveness of the seismic and infrasound sensors to the avalanche regimes is shown. Furthermore, the high amplitudes observed in the infrasound signal for one avalanche were modelled assuming that the suspension layer of the avalanche acts as a moving turbulent sound source. Our results show reproducibility for similar avalanches on the same avalanche path.

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Comparison of avalanche-velocity measurements by means of pulsed Doppler radar, continuous wave radar and optical methods

Cited by 36 publications

References 7 publications

Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system

Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

On the complementariness of infrasound and seismic sensors for monitoring snow avalanches

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