Snow gliding and glide snow avalanches: recent outcomes from two experimental test sites in Aosta Valley (NW Italian Alps)

We have been continuing our research on snow gliding and glide snow avalanches in two experimental test sites in Aosta Valley Region. The sites are located in the Monterosa Ski resorts at 2100-2200 m a.s.l. and are equipped with a couple of glide-snow shoes, temperature and volumetric liquid water content (VLWC) sensors in the soil (at 5 and 15 cm depths) and in the basal snowpack layer. In the surrounding a manual snow station and an automatic weather station recorded snow and weather data. Starting from the preliminary presentation given at the ISSW 2014, we are now able to present new outcomes deriving from different analyses made on a more complete database. In the two monitoring seasons 2013-14 and 2014-15 we registered 9 glide snow avalanches: 2 cold and 7 warm-temperature events. A simple descriptive statistics of the variables registered at the moment of the glide avalanche events showed that the cold glide snow avalanche events were characterized, in average, by: i) a higher soil VLWC (26.9 % and 25.3 %) than in case of warm events (25.6 % and 24.9 %) at 5 cm and 15 cm depths, respectively; ii) a lower VLWC (0.6 %) in the snowpack basal layer than in case of warm events (2.5 %); iii) a slightly higher soil temperature at 5 and 15 cm depths (difference of 0.1 and 0.3 °C respectively) than in case of warm events. In the only warm glide snow avalanche event which presented a continuous gliding before, the daily glide rate showed a significant exponential relationship with the soil VLWC at both depths. Conversely, we did not found any relationship between the glide rate and the driving factors in the continuous cold gliding periods, as we have recently found in another experimental test site in the same region. In conclusion, this study contributes to assess the importance of soil VLWC, which seems to be one of the most important driving factor for gliding processes. Therefore, this study supports the need, already suggested by other scientists, of analysing such processes with an interdisciplinary approach which integrates snow and soil sciences.