Snow farming: Conserving snow over the summer season

Abstract. Summer storage of snow for winter touristic purpose has seen an increasing interest in the last years. Covering large snow piles with materials such as sawdust enables to conserve more than two thirds of the initial snow volume. We present detailed mass balance measurements of two sawdust covered snow piles obtained by terrestrial laser scanning during summer 2015. Results indicate that 74 % and 63 % of the snow volume remained over the summer. If snow mass is considered instead of volume, the values increase to 85 % and 72 % which is attributed to settling and densification of the snow. Additionally, we adapted the one-dimensional, physically based snow cover model SNOWPACK to perform simulations of the sawdust covered snow piles. Model results and measurement agreed extremely well at the point scale. Moreover, we analyzed the contribution of the different terms of the energy balance to snow ablation for a pile covered with a 40 cm thick sawdust layer and a pile without insulation. Shortwave radiation was the dominant source of energy for both scenarios but the moist sawdust caused strong cooling by long-wave emission and negative sensible and latent heat fluxes. This cooling effect reduces the surface energy balance by a factor or 12. As a result only 9 % of the net shortwave energy remained available for melt. Finally, sensitivity studies of the parameters thickness of the sawdust layer, air temperature, precipitation and wind speed were performed. We show that sawdust thickness has a tremendous effect on snow loss. Higher temperatures and wind speeds increase snow ablation but are less important. No significant effect of additional precipitation could be found as the sawdust remained wet during the entire summer. However, switching of precipitation of completely would strongly increase melt.