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Alexei Lyapustin - One of the best experts on this subject based on the ideXlab platform.

  • analysis of snow Bidirectional Reflectance from arctas spring 2008 campaign
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Ralph A Kahn, Richard E Brandt, Jens Redemann, P B Russell, Michael D King, C A Pedersen
    Abstract:

    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 φ

  • Analysis of snow Bidirectional Reflectance from ARCTAS Spring-2008 Campaign
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Ralph A Kahn, Richard E Brandt, Jens Redemann, P B Russell, Michael D King, C A Pedersen, Sebastian Gerland, Rajesh Poudyal
    Abstract:

    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 φ<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.

  • Analysis of snow Bidirectional Reflectance from ARCTAS spring-2008 campaign
    2009
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Jens Redemann, Michael D King, C A Pedersen, Sebastian Gerland, R. Kahn, R. Brandt, P. Russell, Rajesh Poudyal
    Abstract:

    Abstract. The spring 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment was one of the major intensive field campaigns of the International Polar Year, aimed at detailed characterization of atmospheric physical and chemical processes in the Arctic region. 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 φ<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 the 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.

Michel M. Verstraete - One of the best experts on this subject based on the ideXlab platform.

  • On the design and validation of surface Bidirectional Reflectance and albedo models
    Remote Sensing of Environment, 1992
    Co-Authors: Bernard Pinty, Michel M. Verstraete
    Abstract:

    Abstract Physically based mathematical models of the Bidirectional Reflectance of terrestrial surfaces are needed to compute the albedo of these surfaces. Such models are also necessary to interpret satellite remote sensing data in terms of the fundamental physical parameters of the soil and vegetation which control how radiation is reflected by these media. Since a wide variety of mathematical functions can be made to fit the observed Reflectances, a clear and discriminating strategy must be thought out to validate the proposed models. Such a strategy consists in inverting the models against Reflectance data, and comparing the retrieved values of the parameters to those obtained independently from field or laboratory measurements. In this article, we review the state-of-the-art in modeling the Bidirectional Reflectance of natural surfaces, describe how such models can be validated, and highlight the remaining challenges for the remote sensing community.

  • Extracting information on surface properties from Bidirectional Reflectance measurements
    Journal of Geophysical Research, 1991
    Co-Authors: Bernard Pinty, Michel M. Verstraete
    Abstract:

    The retrieval of surface parameters from remotely sensed data is of prime interest for the estimation of surface properties of various planets in the solar system, including the Earth. Bidirectional Reflectance measurements taken over natural surfaces in visible and near-infrared spectral bands represent one data set from which these surface properties could be estimated. To achieve this goal, it is necessary to have both physical models predicting the Bidirectional Reflectance field as a function of the relevant surface parameters, and numerical procedures allowing the inversion of these models using a limited sampling of the Bidirectional Reflectance field. Given that theoretical models of the Bidirectional Reflectance have been published (Hapke, 1981, 1984, 1986; Verstraete et al., 1990) and that numerical procedures are available (Pinty et al., 1990), this paper focuses on the errors and uncertainties in the retrieved parameters which may arise because of (1) the weaknesses in our theoretical understanding and representation of the surface radiation transfer and (2) the errors in the Bidirectional Reflectance data. For instance, it is shown that the addition a posteriori of an amplitude parameter in the function accounting for the opposition effect can drastically modify the retrieved values of the optical and morphological parameters of the surface. The consequences of uncertainties in the Reflectance data are also investigated, and the redistribution, by the inversion procedure, of such uncertainties on the retrieved parameters is discussed. Finally, synthetic Reflectance data contaminated by a known random noise are used to examine the numerical stability of the retrieval and the compatibility between the models.

C A Pedersen - One of the best experts on this subject based on the ideXlab platform.

  • analysis of snow Bidirectional Reflectance from arctas spring 2008 campaign
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Ralph A Kahn, Richard E Brandt, Jens Redemann, P B Russell, Michael D King, C A Pedersen
    Abstract:

    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 φ

  • Analysis of snow Bidirectional Reflectance from ARCTAS Spring-2008 Campaign
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Ralph A Kahn, Richard E Brandt, Jens Redemann, P B Russell, Michael D King, C A Pedersen, Sebastian Gerland, Rajesh Poudyal
    Abstract:

    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 φ<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.

  • Analysis of snow Bidirectional Reflectance from ARCTAS spring-2008 campaign
    2009
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Jens Redemann, Michael D King, C A Pedersen, Sebastian Gerland, R. Kahn, R. Brandt, P. Russell, Rajesh Poudyal
    Abstract:

    Abstract. The spring 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment was one of the major intensive field campaigns of the International Polar Year, aimed at detailed characterization of atmospheric physical and chemical processes in the Arctic region. 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 φ<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 the 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.

Charles K Gatebe - One of the best experts on this subject based on the ideXlab platform.

  • analysis of snow Bidirectional Reflectance from arctas spring 2008 campaign
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Ralph A Kahn, Richard E Brandt, Jens Redemann, P B Russell, Michael D King, C A Pedersen
    Abstract:

    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 φ

  • Analysis of snow Bidirectional Reflectance from ARCTAS Spring-2008 Campaign
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Ralph A Kahn, Richard E Brandt, Jens Redemann, P B Russell, Michael D King, C A Pedersen, Sebastian Gerland, Rajesh Poudyal
    Abstract:

    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 φ<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.

  • Analysis of snow Bidirectional Reflectance from ARCTAS spring-2008 campaign
    2009
    Co-Authors: Alexei Lyapustin, Charles K Gatebe, Jens Redemann, Michael D King, C A Pedersen, Sebastian Gerland, R. Kahn, R. Brandt, P. Russell, Rajesh Poudyal
    Abstract:

    Abstract. The spring 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment was one of the major intensive field campaigns of the International Polar Year, aimed at detailed characterization of atmospheric physical and chemical processes in the Arctic region. 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 φ<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 the 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.

Donald W Deering - One of the best experts on this subject based on the ideXlab platform.

  • Spectral Bidirectional Reflectance characteristics of Russian steppe vegetation and comparison to US prairie grasslands
    Remote Sensing Reviews, 1998
    Co-Authors: Donald W Deering, Thomas F. Eck
    Abstract:

    The spectral, solar angle, and view angle variability of the Bidirectional Reflectance of vegetation canopies has the potential for yielding information on various biophysical and structural aspects of the canopy. Several existing and future satellite sensors provide measurements from which plant canopy Bidirectional Reflectances can be inferred. However, in order to fully utilize the potential of these satellite measurements, a more complete understanding of the dynamics of vegetation canopy optical Reflectance is needed. In this study we present measurements of the dynamics of the Bidirectional Reflectance of several grassland canopies. Measurements were made with the Portable Apparatus for Rapid Acquisition of Bidirectional Observations of the Land and Atmosphere (PARABOLA) instrument in three spectral bands (662, 826, and 1658 nm) for steppe grassland sites of differing productivity levels in the Streletskaya Steppe Reserve, Russia. Variations in solar principal plane Reflectance and vegetation indice...

  • a simple analytical function for Bidirectional Reflectance
    Journal of Geophysical Research, 1992
    Co-Authors: Suraiya P Ahmad, Donald W Deering
    Abstract:

    A simple Bidirectional Reflectance model based on physical scattering laws is developed to calculate the Bidirectional Reflectance of a wide variety of surfaces. Chandrasekhar's radiative transfer solution, obtained for the anisotropically scattering semi-infinite medium, is used to compute the multiplescattered radiances. However, since the radiative transfer solution does not take architectural effects into consideration, we adopt Hapke's (1986) approach and add an empirical term to explain the hot-spot phenomenon and use Cox and Munk's (1954) formulation to take into account the specular reflection. The physical parameters of the model are retrieved from Bidirectional Reflectance measurements. For each surface, only one set of model parameters is needed for application to all illumination and viewing geometries. The validity of the model is established by comparing the computed and measured Reflectances for sets of viewing and illumination angles that were not included in the inversion algorithm. Good agreement is shown between the model-computed and the observed Reflectances for dense prairie vegetation canopies, a sparse desert scrub community, a plowed agricultural field, and an alkali flat.

  • Temporal attributes of the Bidirectional Reflectance for three boreal forest canopies
    1995 International Geoscience and Remote Sensing Symposium IGARSS '95. Quantitative Remote Sensing for Science and Applications, 1
    Co-Authors: Donald W Deering, S. Ahmad, Thomas F. Eck, B. P. Banerjee
    Abstract:

    Multidirectional ground-based optical measurements were acquired along tramways above and beneath three important boreal forest canopies to characterize the complete radiative transfer of visible through shortwave infrared wavelengths. The three forest canopy types exhibited Bidirectional Reflectance features that were distinctively different from each other not only in their magnitudes of Reflectance in a given spectral wavelength band and at forward and backscatter angles but also in their diurnal and seasonal changes. The above-canopy data analyses indicate that each of these forest types must be considered as having unique Bidirectional Reflectance distribution functions and should be modeled individually for both direct (e.g. albedo) and indirect (e.g. biophysical parameter assessments) applications in the quantitative remote sensing of the boreal forest biome.