Abstract ID: 3.12853 | Accepted as Talk | Talk/Oral | TBA | TBA

Surface radiation drives the energy balance on earth and so plays a crucial role in climate change. Here, snow surfaces are of particular interest due to their high reflectivity. In complex alpine terrain, radiation reflected from surrounding slopes significantly impacts the local radiation balance through multiple scattering and the forward scattering properties of snow. The anisotropy largely varies within the solar spectrum, thus leading to a spectral shift within the reflected radiation. Multiple reflections within the terrain further enhance this effect. In this study, we investigate the impact of anisotropic reflection on the spectral albedo and its local differences in complex terrain. We conducted ground-based spectral albedo measurements using a handheld ASD spectrometer on 14th March 2024. Note that scattered clouds during the observations add uncertainty due to non-uniform sky radiation. The measurements were compared with albedo calculations for a flat surface without terrain reflections using the Snow TARTES model. Our findings show enhanced albedo in specific near-infrared wavelength bands, which correlate for large viewing zenith angles positively with the anisotropic reflectance factor. These results suggest that the anisotropic scattering of snow surfaces creates the detected spectral shifts in reflected radiation, varying with viewing angle and terrain complexity. The observed anisotropy appears to preferentially enhance higher energy wavelengths. This effect may increase energy absorption by dark outcropping rocks and potentially accelerate local snow melt. With this study, we want to show the importance of considering anisotropic reflection and multiple scattering in complex terrain when assessing surface radiation budgets and snowmelt processes. To validate and expand our results, we plan to conduct additional measurements under various snow and atmospheric conditions in this winter season.