Environmental Conditions for Snow Cornice Formation tested in a Wind Tunnel

Abstract. Snow cornices growing on the lee of mountain ridges are a common feature in alpine and polar regions during snow seasons. They can result in potential avalanche risk when they crack and fall. Current studies of cornices mainly focus on their deformation, collapsing, and avalanche risk via field observations. Few studies have paid attention to the accretion process of cornices, especially on their horizontal growth which enhances the instability of cornices. In this work, experiments in a cold laboratory under various wind conditions are carried out to investigate the environmental conditions and the internal physical mechanism of cornice formation. The results show that – for the specific settings in our wind tunnel – cornices appear only under moderate wind speeds which lead to necessary net mass flux divergence near the edge. The fastest growth rate is with winds approximately 40 % higher than the rebound threshold wind speed for snow transport because then the snow mass supply to the cornice edge is sufficient. Mass collection efficiency on the cornice surface decreases with the increasing wind speed. This work improves our understanding of cornice formation.