The acoustic snowdrift sensor: interests, calibration and results

During a drifting snow event, it seems to be important to know the flux of blowing snow. Indeed, the height of the snow accumulation in an avalanche departure zone and also snowdrift on roads depend on this quantity. In order to estimate this flux, we have developed at Cemagref, in collaboration with Hydroemac, an acoustic snowdrift sensor. It is made of a microphone located in an aluminum pole. The pole is exposed to the snow particle flux and the sound produced by the particle impacts is recorded as an electrical signal. However, this signal depends not only on the particles flux, but also on the type 01 particles, the presence of a snowfall or not, the wind noise on the sensor, etc. Therefore we have done experiences, both in situ on our experimental site of high altitude called Col du Lac Blanc, and in a climatic wind tunnel (CSTB, France), in order to calibrate our sensor i.e. to establish a relation between the signal on the sensor, and the flux of particles. Moreover, thank to this sensor, we obtained information concerning the threshold velocities of erosion and deposit, and relations between wind and drifting snow. This paper presents our results. KEYWORDS: Drifting snow- snowdrift acoustic sensor _. flux threshold velocitie