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Title: Optical measurements on snow
Authors: Mellor, Malcolm.
Keywords: Snow
Snow properties
Snow optics
Optical properties
Specular reflectance
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Research report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 169.
Description: Research Report
Summary: Spectral extinction measurements for the visual range were made on homogeneous snow samples prepared under controlled conditions, with snow density and grain size as variables. Comparative measurements were made on coarse-grained natural snow. Extinction coefficient 𝙫 was in the range 0.8 to 1.7 cm^-1 for fine-grained dense snow, and 0.16 to 0.37 cm^-1 for the coarse-grained snow. In the fine-grained snow, where scattering is thought to be the dominant attenuating process, there is a general decline in 𝙫 as wavelength 𝝺 increases from 0.4 to 0.7 microns. In the coarse-grained snow, where absorption becomes significant, spectral selection was slight, with a weak minimum in the region 0.5 to 0.6 microns. When 𝙫 is related to density it must have a maximum value; limited data for fine-grained snow show this maximum in the density range 0.45 to 0.60 g/cm^3, and the density for maximum extinction is inversely related to wavelength. For a given density 𝙫 decreases as grain size increases, the rate of change varying with wavelength. Spectral reflectance measurements on natural snow are reported, and attenuation data are interpreted to give surface reflectivity for fine-grained snow. Diffuse reflection from fine-grained snow is believed to have little spectral dependence in the visual range, but with coarse-grained snow reflectance is expected to become inversely dependent on wavelength. It is suggested that optical principles might be applied in the measurement of snow structure, and also for remote sensing of snow-covered terrain.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:CRREL Research Report

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