Lac Blanc Pass: a natural wind-tunnel for studying drifting snow at 2700ma.s.l
Résumé
The investigation of the spatial variability of snow depth in high alpine areas is an important topic in snow hydrology, glacier and avalanche research and the transport of snow by wind is an important process for the distribution of snow in mountainous regions. That's why, for 25 years IRSTEA (previously Cemagref) and Météo France (Centre for the Study of Snow) have joined together in studying drifting snow at Col du Lac Blanc 2700 m a.s.l. near the Alpe d'Huez ski resort in the French Alps. Initially, the site was mainly equipped with conventional meteorological stations and a network of snow poles, in order to test numerical models of drifting snow Sytron (CEN) and NEMO (Cemagref). These models are complementary in terms of spatial and temporal scales: outputs of Sytron model will form the inputs of NEMO model. Then new sensors and technologies appeared which allow to develop new knowledge dealing with thresholds velocity according to morphological features of snow grains, snow flux profiles including parameters such as fall velocity and Schmidt number, histograms of particle widths, aerodynamic roughness, gust factors. More recently, the coupled snowpack/ atmosphere model Meso-NH/Crocus has been evaluated at the experimental site. At the same time, some tested sensors have been deployed in Adelie Land in Antarctica, where blowing snow accounts for a major component of the surface mass balance. Japanese and Austrian research teams have been accomodated at Lac Blanc Pass and new foreign teams are welcome. Initial observations continue. That's why Lac Blanc Pass is also a climatological reference for 25 years at 2700 m. Data are available.
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