Snow Surface Roughness at a Ski Resort During Melt

When snow is present, the snow surface is the interface between the atmosphere and the Earth’s surface. The snowpack energy balance is dictated in part by snow surface roughness, which 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-dimensions from snow roughness boards and in 3-dimensions from iPad surface scanning to measure across resolutions. Both data collection methods yielded similar roughness estimates via random roughness (RR) and variogram analysis (scale break, SB, and fractal dimension, D) for each distinct surface, yet the roughness differences between the surfaces were substantial. The geometry-based aerodynamic roughness length (z0) was computed for the iPad-scanned surfaces, yielding an order-of-magnitude variability in z0. This produced an order-of-magnitude difference in modelled sublimation. This work can inform snow management at ski areas and reflects some of the snow-surface conditions encountered in a natural snowpack.