The effect of ambient air temperature on meltwater production and flow dynamics in snow avalanches

Abstract

Snow avalanche run-out is controlled by flow regime, which is heavily dependent on snow temperature and water content. Existing avalanche models calculate temperature change and snow melting arising from frictional work, snowcover entrainment and particle collisions, but ignore the influence of the ambient air temperature. Here, we propose an experimentally-based relationship to describe the sensible heat flux between the flowing avalanche and the ambient air. A snow avalanche case study and a sensitivity analysis are performed using the proposed model. Modeling results suggest a marginal contribution of heat to the avalanche core, but one, that nonetheless can have significant effect on avalanche runout. For wet (warm) avalanches, higher air temperature will amplify water lubrication effects, leading to longer avalanche run-out. Warmer air temperatures also influence the behaviour of dry, cold avalanches, as the presence of meltwater increases snow cohesion, restricting the formation of strong powder clouds and reducing the avalanche run-out. Colder air temperatures facilitate the formation of more fluidized powder snow avalanches with long run-out and strong air-blasts. The proposed model quantifies the temperature change in the avalanche and can be included in avalanche hazard assessments in which temperature and flow regime are important elements, including the understanding of air temperature and avalanche flow in a changing climate.