1Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland
2Institute for Environmental Research and Sustainable Development, National Observatory of Athens, Greece
3Finnish Meteorological Institute, Kuopio Unit, P.O. Box 1627, 70211 Kuopio, Finland
4Finnish Meteorological Institute, Arctic Research Centre, Tähteläntie 62, 99600 Sodankylä, Finland
5Meteo-France/Centre National de la Recherche Scientifique (CNRS), Toulouse, France
Abstract. Spectral albedo and water liquid content of intensively melting Arctic snow were measured during the Snow Reflectance Transition Experiment (SNORTEX), in Sodankylä, Finland, in April 2009. The upwelling and downwelling spectral irradiance, measured at 290–550 nm with a double monochromator spectroradiometer, revealed the snow albedo to increase as a function wavelength. At the same time, we found the albedo of melting snow to decrease by ~10%, as a function of time within one day. During four days of intensive snow melt, the albedo decreased from 0.65 to 0.45 at 330 nm, and from 0.72 to 0.53 at 450 nm. The diurnal decrease in albedo was supported by measurements of erythemally weighted broadband ultraviolet (UV) albedo. Our simultaneous ancillary data on snow water liquid content showed that the water content first increased in the surface layer, and then moved into deeper layers, after several hours of accumulation. In Radiative Transfer (RT) model calculations, the use of Lambertian assumed regional albedo, instead of the measured local albedo, showed a wavelength dependent difference between the modeled and the measured radiation by up to 9%.