Analyis of a 3 year meteorological record from the ablation zone of the Morteratschgletscher, Switzerland: energy and mass balance

Abstract

Since 1 October 1995, an automatic weather station has been operated on the tongue of Morteratschgletscher, Switzerland. The station stands freely on the ice, and sinks with the melting glacier surface. It is located at 2100 m a.s.l., and measures air temperature, wind speed and direction, incoming and reflected solar radiation, pressure and snow temperature. A sonic ranger, mounted to stakes drilled into the ice, measures surface height from which melt rates and snow accumulation can be derived. In this paper the data for the period 1 October 1995 to 30 September 1998 are used to evaluate the surface energy balance. The turbulent energy fluxes are calculated with the bulk method. The turbulent exchange coefficient Ch is used as a control parameter. With Ch = 0.00127 the calculated melt equals the observed melt, which is 17.70 m w.e. over the 3 years. When averaged over the time when melting occurs (i.e. 35% of the time), the mean surface heat flux equals 191 W m [exp. -2]. Net shortwave radiation contributes 177 W m [exp. -2], net longwave radiation -25 W m [exp. -2], the sensible-heat flux 31 W m [exp. -2]. and the latent-heat flux 8 W m [exp. -2].