Temporal and spatial variation of the surface albedo of Morteratschgletscher, Switzerland, as derived from 12 Landsat images

Abstract

AbstractThis investigation uses Landsat images from 12 days in 1999 and 2000 to study the spatial and temporal variation in surface albedo of a glacier with a rugged topography: Morteratschgletscher, Switzerland. Our retrieval method considers all processes that substantially influence the relationship between the satellite signal and the surface albedo. The correction for the anisotropy of the reflected radiation field of ice and snow ranges up to 0.10, depending on wavelength band, solar zenith angle and surface type. We analyzed the uncertainties in the retrieval method and mainly expect errors in satellite-derived albedos for areas with large variation in topography and high albedos. The latter is due to application of bidirectional reflectance distribution function (BRDF) parameterizations for the anisotropic correction to albedos outside the parameterizations’ validity. On average, satellite-derived albedos exceed the measured surface albedo by 0.03. The glacier tongue is characterized by bands of low and high albedo, relating to ice with higher and lower concentrations of debris. The ice albedo shows no dependence on altitude, except at 2000–2200 m a.s.l. It increases during summer, which is likely associated with rainfall, as concluded from a comparison between summer rainfall and measured albedos.