How to detect snow fall occurence during blowing snow event?
Résumé
In mountainous areas, drifting snow influences the spatial distribution of the snow cover and consequently snowpack stability and avalanche risk. When comparing models with in situ-measurements, it is first necessary to identify snow-drift events with and without concurrent falling snow. In Antarctica, the mass balance of the Antarctic ice sheet is a key parameter of sea level rise, which can be moderated by accumulation change. However, in the coastal areas where katabatic winds are strong and frequent, it is necessary to identify and separate blowing snow and precipitation. It was shown that size distribution of blowing snow particles given by a snow particle counter at a specific height can be approximated by a two-parameter gamma probability function and that a bi-modal distribution could appear at high elevation when snow fall occurs (Nishimura and Nemoto, 2005). In such way, it could be possible to evaluate precipitation. But depending on the height, the size of snow fall particle and the wind speed it is not so easy to distinguish between both types of events. In such case, the analysis of snow flux and mean diameter according to wind speed allows to separate blowing snow event with and without precipitation. It gives better results in predicting the timing of precipitation than done by precipitation gauges. A simpler photoelectric counter such as designed by Wenglor could also give some interesting results. These conclusions are supported by field campaigns conducted in French Alps and in Antarctica (coastal Adélie Land) during last winters.
Domaines
Sciences de l'environnement
Origine : Fichiers produits par l'(les) auteur(s)
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