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Conference Papers Year : 2008

Drifting snow measurements over an instrumented mountainous site : improvement of numerical model input parameters

Mesures in situ du transport éolien de la neige : amélioration de la connaissance des paramètres d'entrée des modèles

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F. Naaim-Bouvet
H. Bellot

Abstract

Blowing snow may occur both in mountain ranges and on flat terrain, creating cornices, slabs, or snowdrifts. As a consequence, the probability of avalanche occurrence can be totally modified, roads and buildings can be obstructed and drivers' visibility can be dramatically reduced. Therefore, the prediction and control of drift patterns are of real importance. Different blowing-snow studies were conducted using either physical or numerical modeling. The numerical model currently used in Cemagref is NEMO. Although its predictions correctly reproduce the windward and leeward accumulations around fences in wind tunnels, the computation results were often less conclusive when compared to those of field experiments. Indeed, accurate evaluations of the input parameters needed for the numerical model remain an open question. At the present time for our numerical model the estimation of roughness, blowing snow mass fluxes and wind profiles is mainly obtained from empirical relations determined by Pomeroy and Gray on flat areas in Canada. As the topography and type of snow could be quite different in the Alps, further experimental research is needed before using such formulae. To obtain the required field data (roughness, friction speed, threshold friction speed, flowing snow mass fluxes profiles), specific optical and acoustic instruments (e.g., SPC and Flowcapt, respectively) and a 10 meter-mast with 6 anemometers, 3 temperature sensors and a depth sensor were set up on our experimental site Col Du Lac Blanc (2700 m) in the Alps. New data obtained during winter 2007-2008 are compared with empirical formulae and past experimental data.

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Dates and versions

hal-02591734 , version 1 (15-05-2020)

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F. Naaim-Bouvet, H. Bellot. Drifting snow measurements over an instrumented mountainous site : improvement of numerical model input parameters. European Geosciences Union, General Assembly, Vienna, AUT, 13-18 April 2008, 2008, pp.1. ⟨hal-02591734⟩

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