Depth-hoar growth rates near a rocky outcrop

Observations of slab-avalanche releases in alpine terrain have led to the h ypothesis that rocky outcrops can influence the spatial distributions of te mperature and heat flow in dry alpine snow covers and thus control the loca l distribution of depth hear. We investigate the effects of terrain on crys tal growth by using a two-dimensional finite-element model of heat flow cou pled with a model of crystal growth from vapor. We used the model to examin e the influence of snow properties, terrain geometry and snow depth on this phenomenon. The effect is stronger in the early winter than in the late wi nter, because the rock has then had time to cool. In all cases, We found th at depth-hear growth occurs preferentially over the rock. This suggests tha t snow-pit investigations made over soil can be misleading if rocky outcrop s are present.