A 1 year record of global radiation and albedo in the ablation zone of Morteratschgletscher, Switzerland

We analyse data on solar radiation measured with an automatic weather stati on on Morteratschgletscher, Switzerland, for the period 1 October 1995-30 S eptember 1996. The station is in the lower ablation zone. Due to shading by surrounding mountains and atmospheric attenuation, only 49% of the annual extraterrestrial irradiance (mean: 292 W m(2)) reaches the glacier surface. About 48% of this is absorbed at the surface (mean: 79 W m(-2); annual alb edo of 0.53). We present a simple albedo scheme for use in glacier mass-balance models. W e fit the model to the 1 year dataset by optimizing five control parameters (optimal values in brackets): albedo of snow (0.75), albedo of firn (0.53) , albedo of ice (0.34), e-folding constant for effect of ageing on snow alb edo (21.9 days) and e-folding constant for effect of snow depth on albedo ( 3.2 cm). The input consists of daily albedo, snow depth and dates of snowfa ll events. The correlation coefficient between observed and simulated albed o is 0.931, the corresponding rms difference being 0.067.