Assessing the drivers controlling the development of airborne layers in powder snow avalanches through infrasound analysis

6 S.

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200212314

Proceedings of the International Snow Science Workshop 2024 Tromsø, Norway (2024) , 6 S.

Powder snow avalanches (PSAs) with high-energy airborne layers pose a significant threat to buildings and facilities intended to be protected by infrastructure like dams. However, understanding the factors driving the development of these hazardous suspension layers remains challenging due to limited experimental data and understanding of PSA generation mechanisms. Recent advances in infrasound research have revealed that infrasound is primarily generated from particle clusters suspended in the airborne layer of PSAs by turbulent eddies or ejected from the denser basal layer. In addition, the infrasound signal is correlated with the kinetic energy of all active particles within these layers, offering a promising avenue to address this challenge. In this study, we analyze 27 infrasound signals collected at the Vall ´ee de la Sionne test site in Switzerland, covering various PSA dimensions and degrees of powder cloud development. We systematically quantify amplitudes, cumulative intensities, and energy distribution extracted from the infrasound measurements. These findings are compared with reference data from a high-resolution GEODAR radar to assess the evolution of the powder cloud in both temporal and spatial dimensions. Subsequently, we correlate this information with boundary conditions such as snow cover, and previous avalanche activity to understand their influence on the development of high-energy airborne layers in PSAs. Conversely, we explore how these factors contribute to the decay of the powder cloud, thereby enhancing our ability to assess and mitigate avalanche hazard.
Keywords: Powder Snow Avalanches, Infrasound, Turbulent Particle-Laden Flow, Turbulent Multiphase Flow