Geometrical Thickness, Liquid Water Content, and Radiative Properties of Stratocumulus Clouds over the Western North Pacific

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  • a Center for Atmospheric and Oceanic Studies, Faculty of Science, Tohoku University, Sendai, Japan
  • | b Center for Climate System Research, University of Tokyo, Tokyo, Japan
  • | c Institute for Hydrospheric-Atmospheric Sciences, Nagoya University, Nagoya, Japan
  • | d Center for Atmospheric and Oceanic Studies, Faculty of Science, Tohoku University, Sendai, Japan
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Abstract

An algorithm was developed for retrieving cloud geometrical thickness from a measured liquid water path and equivalent width of 0.94-µm water vapor absorption band. The algorithm was applied to aircraft observations obtained by a microwave radiometer and a spectrometer in the winter of 1991 over the western North Pacific Ocean. Retrieved values of the cloud geometrical thickness are apt to be smaller than those observed by eye, especially for horizontally inhomogeneous clouds. Measured cloud albedos in the visible and near-infrared spectral region were also compared with calculated values. For homogeneous clouds there exists a single droplet size distribution that satisfies both spectral regions. However, for inhomogeneous clouds no single size distribution exists that satisfies the albedo observed in both spectral regions.

Abstract

An algorithm was developed for retrieving cloud geometrical thickness from a measured liquid water path and equivalent width of 0.94-µm water vapor absorption band. The algorithm was applied to aircraft observations obtained by a microwave radiometer and a spectrometer in the winter of 1991 over the western North Pacific Ocean. Retrieved values of the cloud geometrical thickness are apt to be smaller than those observed by eye, especially for horizontally inhomogeneous clouds. Measured cloud albedos in the visible and near-infrared spectral region were also compared with calculated values. For homogeneous clouds there exists a single droplet size distribution that satisfies both spectral regions. However, for inhomogeneous clouds no single size distribution exists that satisfies the albedo observed in both spectral regions.

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