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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D18106, doi:10.1029/2006JD007290, 2006

Spectral bidirectional reflectance of Antarctic snow: Measurements and parameterization

Stephen R. Hudson

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

Stephen G. Warren

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

Richard E. Brandt

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

Thomas C. Grenfell

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

Delphine Six

Laboratoire de Glaciologie et Géophysique de l'Environnement, Centre National de la Recherche Scientifique, Université Joseph Fourier, Saint Martin d'Hères, France

Abstract

The bidirectional reflectance distribution function (BRDF) of snow was measured from a 32-m tower at Dome C, at latitude 75°S on the East Antarctic Plateau. These measurements were made at 96 solar zenith angles between 51° and 87° and cover wavelengths 350–2400 nm, with 3- to 30-nm resolution, over the full range of viewing geometry. The BRDF at 900 nm had previously been measured at the South Pole; the Dome C measurement at that wavelength is similar. At both locations the natural roughness of the snow surface causes the anisotropy of the BRDF to be less than that of flat snow. The inherent BRDF of the snow is nearly constant in the high-albedo part of the spectrum (350–900 nm), but the angular distribution of reflected radiance becomes more isotropic at the shorter wavelengths because of atmospheric Rayleigh scattering. Parameterizations were developed for the anisotropic reflectance factor using a small number of empirical orthogonal functions. Because the reflectance is more anisotropic at wavelengths at which ice is more absorptive, albedo rather than wavelength is used as a predictor in the near infrared. The parameterizations cover nearly all viewing angles and are applicable to the high parts of the Antarctic Plateau that have small surface roughness and, at viewing zenith angles less than 55°, elsewhere on the plateau, where larger surface roughness affects the BRDF at larger viewing angles. The root-mean-squared error of the parameterized reflectances is between 2% and 4% at wavelengths less than 1400 nm and between 5% and 8% at longer wavelengths.

Received 12 March 2006; accepted 1 June 2006; published 28 September 2006.

Keywords: BRDF; snow; Antarctica.

Index Terms: 0736 Cryosphere: Snow (1827, 1863); 0758 Cryosphere: Remote sensing; 9310 Geographic Location: Antarctica (4207).

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Citation: Hudson, S. R., S. G. Warren, R. E. Brandt, T. C. Grenfell, and D. Six (2006), Spectral bidirectional reflectance of Antarctic snow: Measurements and parameterization, J. Geophys. Res., 111, D18106, doi:10.1029/2006JD007290.

Copyright 2006 by the American Geophysical Union.