Modelling seasonal and spatial variations in the surface energy balance of Haut Glacier d'Arolla, Switzerland

The impact of spatial and temporal variations in the surface albedo and acrodynamic roughness length on the surface energy balance of Haut Glacier d'Arolla, Switzerland, was examined using a semi-distributed surface energy-balance model (Arnold and others, 1996). The model was updated to incorporate the glacier-wide effects of albedo and aerodynamic roughness-length variations using parameterizations following Brock (1997). After the model's performance was validated, the glacier-wide patterns of the net shortwave, turbulent and melt energy fluxes were examined on four days, representative of surface conditions in late May, June, July and August. In the model, meteorological conditions were held constant on each day in order that the impact of albedo and aerodynamic roughness-length variations could be assessed independently. A late-summer snowfall event was also simulated. Albedo and aerodynamic roughness-length variations, particularly those associated with the migration of the transient snowline and the decay of the winter snowpack, were found to exert a strong influence on the magnitude of the surface energy fluxes. The importance of meteorological conditions in suppressing the surface energy fluxes and melt rate following a fresh snowfall was highlighted.