Spectral albedo of seasonal snow during intensive melt period at Sodankylä, beyond the Arctic Circle
- ISSN: 1680-7324
- DOI: 10.5194/acp-13-3793-2013
We have measured spectral albedo, as well as an- cillary parameters, of seasonal European Arctic snow at So- dankyl¨ a, Finland (67◦22? N, 26◦39? E). The springtime inten- sive melt period was observed during the Snow Reflectance Transition Experiment (SNORTEX) in April 2009. The up- welling and downwelling spectral irradiance, measured at 290–550nm with a double monochromator spectroradiome- ter, revealed albedo values of ∼0.5–0.7 for the ultraviolet and visible range, both under clear sky and variable cloudi- ness. During the most intensive snowmelt period of four days, albedo decreased from 0.65 to 0.45 at 330 nm, and from 0.72 to 0.53 at 450 nm. In the literature, the UV and VIS albedo for clean snow are ∼0.97–0.99, consistent with the extremely small absorption coefficient of ice in this spec- tral region. Our low albedo values were supported by two independent simultaneous broadband albedo measurements, and simulated albedo data.We explain the low albedo values to be due to (i) large snow grain sizes up to ∼3mm in di- ameter; (ii) meltwater surrounding the grains and increasing the effective grain size; (iii) absorption caused by impurities in the snow, with concentration of elemental carbon (black carbon) in snow of 87 ppb, and organic carbon 2894 ppb, at the time of albedo measurements. The high concentrations of carbon, detected by the thermal–optical method, were due to air masses originating from the Kola Peninsula, Russia, where mining and refining industries are located.