Snow Surface Roughness at a Ski Resort During Melt

The snowpack is the interface between the atmosphere and the earth’s surface when snow is present. The snowpack energy balance is dictated in part by the nature of the snow surface. The roughness of the snow surface can be quite dynamic. At the Sierra Nevada ski resort in Spain, we measured several snow surface forms: natural, with the presence of dust, with the presence of sun cups, and groomed snow (tracked and between tracks). The snow surface was assessed in 2-D from snow roughness boards and in 3-D from iPad surface scanning to measure across resolutions. Both data collection methods provided similar roughness estimates via the random roughness (RR) and variogram analysis (scale break, SB and fractal dimension, D) for each distinct surface. The geometry-based aerodynamic roughness length (z0) was computed for the iPad-scanned surfaces yielding an order of magnitude variability in z0. This produced substantial differences in modelled sublimation.