Snow farming: conserving snow over the summer season

Abstract

Abstract. Summer storage of snow for tourism has seen an increasing interest in the last years. Covering large snow piles with materials such as sawdust enables more than two-thirds of the initial snow volume to be conserved. 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 for piles in Davos, Switzerland and Martell, Italy. If snow mass is considered instead of volume, the values increase to 83 and 72 %. The difference 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 measurements agreed extremely well at the point scale. Moreover, we analysed the contribution of the different terms of the surface energy balance to snow ablation for a pile covered with a 40 cm thick sawdust layer and a pile without insulation. Short-wave 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 energy available for melt by up to a factor of 12. As a result only 9 % of the net short-wave 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 air temperatures and wind speeds increase snow ablation but less significantly. No significant effect of additional precipitation could be found as the sawdust remained wet during the entire summer with the measured quantity of rain. Setting precipitation amounts to zero, however, strongly increased melt. Overall, the 40 cm sawdust provides sufficient protection for midelevation (approx. 1500 m a.s.l.) Alpine climates and can be managed with reasonable effort.

Water Losses During Technical Snow Production: Results From Field Experiments

“…Terrestrial laser scanning is a well-established method to acquire high resolution elevation models of snow surfaces with a vertical accuracy of some centimeters (Prokop et al, 2008;Grünewald et al, 2010Grünewald et al, , 2018bRevuelto et al, 2014). The device deployed for this study was a Riegl VZ-6000 terrestrial laser scanner (Riegl Measurement Systems GmbH, 2018) that has been successfully applied to monitor snow surfaces and snow-height changes (dHSs) in several projects (e.g., Gabbud et al, 2015;Fischer et al, 2016;Haberkorn et al, 2017;Grünewald et al, 2018b;Mott et al, 2019). Technical specifications of the VZ6000 are listed by Fischer et al (2016) and in the Riegl data sheet (Riegl Measurement Systems GmbH, 2018).…”

“…To avoid data gaps caused by terrain shadowing, scans were done from two to three positions. The workflow of post-processing was the same as described in Grünewald et al (2018b). For each pair of surveys, raw data were registered with four reflectors installed in the area.…”

“…Unchanged areas (without snow accumulation) were selected for Multi Station Adjustment, a semi-automatic least square surface matching technique implemented in the processing software (Riegl Measurement Systems GmbH, 2011). This technique was successfully applied by many studies for the registration of TLS data (Carrivick et al, 2013;Sommer et al, 2015;Fischer et al, 2016;Grünewald et al, 2018b). After selecting the area of interest, a moving-window filter (octree filter) was applied to reduce the data amount and to produce a regular grid with an edge length of 10 cm.…”

Comments and suggestions

“…Printer-friendly version Discussion paper L14: snow storage is quite expensive (see Grünewald et al 2018) L16 Besides solar radiation, air temperature is most important for snow melt (see Fig 11 in Grünewald et al 2018); precipitation is less relevant; why should evaporative cooling be higher in cold and dry climates? Evaporation is depending on the temperature gradient between surface and air, wind and wetness of the covering-layer.…”

“…How is it interpreted? Add references; P7 L6-9 This explanation is too simple: heat transfer is not simply depending on air temperature; surface temperature, cloudiness (longwave radiation) and wind (turbulent fluxes) are also crucial; See discussion of simulation results in Grünewald et al 2018 and the sections about energy balance, and snow melt of the recent review paper of C7…”