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Analysis of Snow Bidirectional Reflectance from ARCTAS Spring-2008 CampaignThe spring 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment was one of major intensive field campaigns of the International Polar Year aimed at detailed characterization of atmospheric physical and chemical processes in the Arctic region. A part of this campaign was a unique snow bidirectional reflectance experiment on the NASA P-3B aircraft conducted on 7 and 15 April by the Cloud Absorption Radiometer (CAR) jointly with airborne Ames Airborne Tracking Sunphotometer (AATS) and ground-based Aerosol Robotic Network (AERONET) sunphotometers. The CAR data were atmospherically corrected to derive snow bidirectional reflectance at high 1 degree angular resolution in view zenith and azimuthal angles along with surface albedo. The derived albedo was generally in good agreement with ground albedo measurements collected on 15 April. The CAR snow bidirectional reflectance factor (BRF) was used to study the accuracy of analytical Ross-Thick Li-Sparse (RTLS), Modified Rahman-Pinty-Verstraete (MRPV) and Asymptotic Analytical Radiative Transfer (AART) BRF models. Except for the glint region (azimuthal angles phi less than 40 degrees), the best fit MRPV and RTLS models fit snow BRF to within 0.05. The plane-parallel radiative transfer (PPRT) solution was also analyzed with the models of spheres, spheroids, randomly oriented fractal crystals, and with a synthetic phase function. The latter merged the model of spheroids for the forward scattering angles with the fractal model in the backscattering direction. The PPRT solution with synthetic phase function provided the best fit to measured BRF in the full range of angles. Regardless of the snow grain shape, the PPRT model significantly over-/underestimated snow BRF in the glint/backscattering regions, respectively, which agrees with other studies. To improve agreement with experiment, we introduced a model of macroscopic snow surface roughness by averaging the PPRT solution over the slope distribution function and by adding a simple model of shadows. With macroscopic roughness described by two parameters, the AART model achieved an accuracy of about plus or minus 0.05 with a possible bias of plus or minus 0.03 in the spectral range 0.4-2.2 micrometers. This high accuracy holds at view zenith angles below 55-60 degrees covering the practically important range for remote sensing applications, and includes both glint and backscattering directions.
Document ID
20110016150
Document Type
Reprint (Version printed in journal)
Authors
Lyapustin, A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Gatebe, C. K. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Redemann, J. (Bay Area Environmental Research Inst. Sonoma , CA, United States)
Kahn, R. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Brandt, R. (Washington Univ. Seattle, WA, United States)
Russell, P. (NASA Ames Research Center Moffett Field, CA, United States)
King, M. D. (Colorado Univ. Boulder, CO, United States)
Pedersen, C. A. (Norwegian Polar Inst. Tromso, Norway)
Gerland, S. (Norwegian Polar Inst. Tromso, Norway)
Poudyal, R. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Marshak, A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Wang, Y. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Schaaf, C. (Boston Univ. Boston, MA, United States)
Hall, D. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Kokhanovsky, A. (Bremen Univ. Germany)
Date Acquired
August 25, 2013
Publication Date
May 10, 2010
Publication Information
Publication: Atmospheric Chemistry and Physics
Volume: 10
Subject Category
Meteorology and Climatology
Distribution Limits
Public
Copyright
Other