Analysis of temporal and spatial snow depth changes in a steep rock face

ABSTRACT: To understand snow distribution in steep rock walls a high resolution terrestrial laser scanner (TLS) was used to achieve precise snow height digital surface models. We collected surface data without snow, before and after significant snowfall or wind drift events and during the ablation period. We then generated digital surface models (DSM) for each observation period. The summer scan under the total absence of snow allowed us to provide a digital elevation model (DEM) and to calculate absolute snow depth. Relative snow depth changes can be extracted by the comparison of different winter scans. In addition to the laser scans, orthophotos were taken with a digital camera. In a first step we could show that with TLS reliable information on surface data of a steep rocky surface can be achieved. In comparison to a flat field point measurement the mean snow depth in the rock face was smaller during the entire winter, but trends of snow depth changes were similar. We ob-served repeating accumulation and ablation patterns in the rock face, while maximum snow depth loss occurred always at those places with maximum snow depth gain. Furthermore, increasing snow depth resulted in a decrease of high slope angles. Further analyses should involve the statistical relation of spatial and temporal distribution of snow depth to (i) terrain features e.g. slope angle, aspect or curva-ture and (ii) resulting surface processes derived from spatial distributed model outputs e.g. radiation, wind fields or blowing and drifting snow