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Volume 12, issue 7 | Copyright
The Cryosphere, 12, 2371-2382, 2018
https://doi.org/10.5194/tc-12-2371-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 20 Jul 2018

Research article | 20 Jul 2018

On the reflectance spectroscopy of snow

Alexander Kokhanovsky1, Maxim Lamare2,3, Biagio Di Mauro4, Ghislain Picard2, Laurent Arnaud2, Marie Dumont3, François Tuzet3,2, Carsten Brockmann5, and Jason E. Box6 Alexander Kokhanovsky et al.
  • 1VITROCISET, Bratustrasse 7, 64293 Darmstadt, Germany
  • 2UGA, CNRS, Institut des Géosciences de l'Environnement (IGE), UMR 5001, Grenoble, 38041, France
  • 3Meteo-France–CNRS, CNRM UMR 3589, Centre d'Etudes de la Neige, Grenoble, France
  • 4Department of Earth and Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza, 1, 20126 Milan, Italy
  • 5Brockmann Consult, Max Planck Strasse 2, Geesthacht, Germany
  • 6Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark

Abstract. We propose a system of analytical equations to retrieve snow grain size and absorption coefficient of pollutants from snow reflectance or snow albedo measurements in the visible and near-infrared regions of the electromagnetic spectrum, where snow single-scattering albedo is close to 1.0. It is assumed that ice grains and impurities (e.g., dust, black and brown carbon) are externally mixed, and that the snow layer is semi-infinite and vertically and horizontally homogeneous. The influence of close-packing effects on reflected light intensity are assumed to be small and ignored. The system of nonlinear equations is solved analytically under the assumption that impurities have the spectral absorption coefficient, which obey the Ångström power law, and the impurities influence the registered spectra only in the visible and not in the near infrared (and vice versa for ice grains). The theory is validated using spectral reflectance measurements and albedo of clean and polluted snow at various locations (Antarctica Dome C, European Alps). A technique to derive the snow albedo (plane and spherical) from reflectance measurements at a fixed observation geometry is proposed. The technique also enables the simulation of hyperspectral snow reflectance measurements in the broad spectral range from ultraviolet to the near infrared for a given snow surface if the actual measurements are performed at a restricted number of wavelengths (two to four, depending on the type of snow and the measurement system).

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This work presents a new technique with which to derive the snow microphysical and optical properties from snow spectral reflectance measurements. The technique is robust and easy to use, and it does not require the extraction of snow samples from a given snowpack. It can be used in processing satellite imagery over extended fresh dry, wet and polluted snowfields.
This work presents a new technique with which to derive the snow microphysical and optical...
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