• Barker, H. W., B. W. Wielicki, and L. Parker, 1996: A parameterization for computing grid-averaged solar fluxes for inhomogeneous marine boundary layer clouds. Part II: Validation using satellite data. J. Atmos. Sci.,53, 2304–2316.

  • Baum, B. A., and Coauthors, 1995: Imager cloud height determination (Subsystem 4.2). Clouds and the Earth’s Radiant Energy System (CERES) algorithm theoretical basis document, Volume III: Cloud analyses and radiance inversion (Subsystem 4). NASA RP 1376, Vol. 3, CERES Science Team, Eds., 259 pp. [Available from NASA Center for AeroSpace Information, 800 Elkridge Landing Rd., Linthicum Heights, MD 21090-2934.].

  • Cahalan, R. F., W. Ridgway, W. J. Wiscombe, T. L. Bell, and J. B. Snider, 1994a: The albedo of fractal stratocumulus clouds. J. Atmos. Sci.,51, 2434–2455.

  • ——, ——, ——, S. Gollmer, and Harshvardhan, 1994b: Independent pixel and Monte Carlo estimates of stratocumulus albedo. J. Atmos. Sci.,51, 3776–3790.

  • ——, D. Silberstein, and J. B. Snider, 1995: Liquid water path and plane-parallel albedo bias during ASTEX. J. Atmos. Sci.,52, 3002–3011.

  • Chambers, L. H., 1997: Computation of the effects of inhomogeneous clouds on retrieval of remotely sensed properties. Preprints, Ninth Conf. on Atmospheric Radiation, Long Beach, CA, Amer. Meteor. Soc., 378–382.

  • ——, B. A. Wielicki, and K. F. Evans, 1996: On the accuracy of the independent pixel approximation for satellite estimates of oceanic boundary layer cloud optical depth. J. Geophys. Res.,102 (D2), 1779–1794.

  • Harshvardhan, B. A. Wielicki, and K. M. Ginger, 1994: The interpretation of remotely sensed cloud properties from a model parameterization perspective. J. Climate,7, 1987–1998.

  • Marshak, A., A. Davis, W. Wiscombe, and R. Cahalan, 1995: Radiative smoothing in fractal clouds. J. Geophys. Res.,100, 26 247–26 261.

  • Minnis, P., P. W. Heck, D. F. Young, C. W. Fairall, and B. J. Snider, 1992: Stratocumulus cloud properties derived from simultaneous satellite and island-based instrumentation during FIRE. J. Appl. Meteor.,31, 317–339.

  • Wiscombe, W. J., 1977: The delta-M method: Rapid yet accurate radiative flux calculations for strongly asymmetric phase functions. J. Atmos. Sci.,34, 1408–1422.

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Independent Pixel and Two-Dimensional Estimates of Landsat-Derived Cloud Field Albedo

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  • 1 Atmospheric Sciences Division, NASA/Langley Research Center, Hampton, Virginia
  • | 2 University of Colorado, Boulder, Colorado
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Abstract

A theoretical study has been conducted on the effects of cloud horizontal inhomogeneity on cloud albedo bias. A two-dimensional (2D) version of the Spherical Harmonic Discrete Ordinate Method (SHDOM) is used to estimate the albedo bias of the plane-parallel (PP–IPA) and independent pixel (IPA–2D) approximations for a wide range of 2D cloud fields obtained from Landsat. They include single-layer trade cumulus, open and closed cell broken stratocumulus, and solid stratocumulus boundary layer cloud fields over ocean. Findings are presented on a variety of averaging scales and are summarized as a function of cloud fraction, mean cloud optical depth, cloud aspect ratio, standard deviation of optical depth, and the gamma function parameter ν (a measure of the width of the optical depth distribution). Biases are found to be small for small cloud fraction or mean optical depth, where the cloud fields under study behave linearly. They are large (up to 0.20 for PP–IPA bias, −0.12 for IPA–2D bias) for large ν. On a scene-average basis, PP–IPA bias can reach 0.30, while IPA–2D bias reaches its largest magnitude at −0.07. Biases due to horizontal transport (IPA–2D) are much smaller than PP–IPA biases but account for 20% rms of the bias overall.

Limitations of this work include the particular cloud field set used, assumptions of conservative scattering, constant cloud droplet size, no gas absorption or surface reflectance, and restriction to 2D radiative transport. The Landsat data used may also be affected by radiative smoothing.

Corresponding author address: Dr. Lin H. Chambers, Atmospheric Sciences Division, NASA/Langley Research Center, Hampton, VA 23681-0001.

Email: L.H.Chambers@larc.nasa.gov

Abstract

A theoretical study has been conducted on the effects of cloud horizontal inhomogeneity on cloud albedo bias. A two-dimensional (2D) version of the Spherical Harmonic Discrete Ordinate Method (SHDOM) is used to estimate the albedo bias of the plane-parallel (PP–IPA) and independent pixel (IPA–2D) approximations for a wide range of 2D cloud fields obtained from Landsat. They include single-layer trade cumulus, open and closed cell broken stratocumulus, and solid stratocumulus boundary layer cloud fields over ocean. Findings are presented on a variety of averaging scales and are summarized as a function of cloud fraction, mean cloud optical depth, cloud aspect ratio, standard deviation of optical depth, and the gamma function parameter ν (a measure of the width of the optical depth distribution). Biases are found to be small for small cloud fraction or mean optical depth, where the cloud fields under study behave linearly. They are large (up to 0.20 for PP–IPA bias, −0.12 for IPA–2D bias) for large ν. On a scene-average basis, PP–IPA bias can reach 0.30, while IPA–2D bias reaches its largest magnitude at −0.07. Biases due to horizontal transport (IPA–2D) are much smaller than PP–IPA biases but account for 20% rms of the bias overall.

Limitations of this work include the particular cloud field set used, assumptions of conservative scattering, constant cloud droplet size, no gas absorption or surface reflectance, and restriction to 2D radiative transport. The Landsat data used may also be affected by radiative smoothing.

Corresponding author address: Dr. Lin H. Chambers, Atmospheric Sciences Division, NASA/Langley Research Center, Hampton, VA 23681-0001.

Email: L.H.Chambers@larc.nasa.gov

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