Title Analysis of snow bidirectional reflectance from ARCTAS Spring-2008 Campaign
Author Lyapustin, A.I.; Gatebe, C.K.; Kahn, R.; Brandt, R.; Redemann, J.; Russell, P.; King, M.D.; Pedersen, C.A.; Gerland, S.; Poudyal, R.; Marshak, A.; Wang, Y.; Schaaf, C.; Hall, D.; Kokhanovsky, A.
Author Affil Lyapustin, A.I., University of Maryland Baltimore County, Baltimore, MD. Other: NASA, Goddard Space Flight Center; University of Washington; Bay Area Environmental Research Institute; NASA, Ames Research Center; University of Colorado; Norwegian Polar Institute, Norway; Science Systems and Applications; Boston University; Universität Bremen, Germany
Source Atmospheric Chemistry and Physics, 10(9), p.4359-4375, . Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1680- 7316
Publication Date 2010
Notes In English. Includes appendices; part of special issue no. 182, POLARCAT (Polar study using aircraft, remote sensing, surface measurements and models, of climate, chemistry, aerosols, and transport), edited by Stohl, A., et al., http://www.atmos-chem- phys.net/special_issue182.html; published in Atmospheric Chemistry and Physics Discussions: 20 October 2009, http://www.atmos-chem-phys- discuss.net/9/21993/2009/acpd-9-21993-2009.ht ml; accessed in May, 2011. 53 refs. CRREL Acc. No: 65006801
Index Terms aerial surveys; albedo; anisotropy; backscattering; climate; composition; crystals; fractals; grain size; ice; ice crystals; impurities; polar regions; polar atmospheres; reflectivity; reflection; remote sensing; snow; solar radiation; Arctic region; polar regions; airborne methods; Analytical Approximate Radiative Transfer model; atmosphere; Cloud Absorption Radiometer; errors; International Polar Year 2007-08; MODIS; reflectance; satellite methods; shadows; troposphere
Abstract The 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° 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 #2F‹40°), 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 ±0.05 with a possible bias of ±0.03 in the spectral range 0.4-2.2 µm. This high accuracy holds at view zenith angles below 55-60° covering the practically important range for remote sensing applications, and includes both glint and backscattering directions.
URL http://www.atmos-chem-phys.net/10/4359/2010/acp-10-4359-2010.pdf
Publication Type journal article
Record ID 310051