Abstract
Abstract. We have measured spectral albedo, as well as ancillary parameters, of seasonal European Arctic snow at Sodankylä, Finland (67°22' N, 26°39' E). The springtime intensive melt period was observed during the Snow Reflectance Transition Experiment (SNORTEX) in April 2009. The upwelling and downwelling spectral irradiance, measured at 290–550 nm with a double monochromator spectroradiometer, revealed albedo values of ~0.5–0.7 for the ultraviolet and visible range, both under clear sky and variable cloudiness. 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 spectral 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 ~3 mm in diameter; (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.
Highlights
The extremely small absorption coefficient of ice in this spec- et al, 2006; Warren andHByrdanrdot,lo20g0y8).aAnsdthe wavelength tral region
Acthe effective grain size; (iii) absorption caused by impurities cording to the literature (Wiscombe and Warren, 1980; Warin the snow, with concentration of elemental carbon in snow of 87 ppb, and organic carbon 2894 ppb, at r2e0n07a;nGd aWrdinsecromanbde,Sh1a9Or8p0c,)2ea0an1d0n;RMSTacymieeordnaenlcsde(KFylallninnge,r et al, 2005), the time of albedo measurements
The Snow Reflectance Transition Experiment (SNORTEX) study area was located in the Finnish Lapland beyond the Arctic Circle, and benefited from existing facilities provided by the Finnish Meteorological Institute – Arctic Research Center (FMI-ARC), based in Sodankyla (67◦22 N, 26◦39 E, 179 m.a.s.l.)
Summary
The extremely small absorption coefficient of ice in this spec- et al, 2006; Warren andHByrdanrdot,lo20g0y8).aAnsdthe wavelength tral region. Acthe effective grain size; (iii) absorption caused by impurities cording to the literature (Wiscombe and Warren, 1980; Warin the snow, with concentration of elemental carbon (black carbon) in snow of 87 ppb, and organic carbon 2894 ppb, at r2e0n07a;nGd aWrdinsecromanbde,Sh1a9Or8p0c,)2ea0an1d0n;RMSTacymieeordnaenlcsde(KFylallninnge,r et al, 2005), the time of albedo measurements. Ing to theory (Wiscombe and Warren, 1980), snow albedo decreases as the grain size inScroealisdes,Easaartshmaller effective radius increases the probability that an incident photon will scatter out of the snowpack (Gardner and Sharp, 2010). As snow ages, with or without melting, the grain size increases and albedo lowers (Wiscombe and Warren, 1980)
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