Inference of cirrus cloud properties using satellite-observed visible and infrared radiances. Part I: parameterization of radiance fields

Journal Article · Sat May 01 04:00:00 EDT 1993 · Journal of the Atmospheric Sciences; (United States)

DOI:https://doi.org/10.1175/1520-0469(1993)050<1279:IOCCPU>2.0.CO;2· OSTI ID:6336468

Minnis, P ^[1]; Liou, Kuonan; Takano, Yoshihide ^[2]

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1. NASA Langley Research Center, Hampton, VA (United States)
2. Univ. of Utah, Salt Lake City (United States)

This study examines the impact of using phase functions for spherical droplets and hexagonal ice crystals to analyze radiances from cirrus. Adding-doubling radiative transfer calculations are used to compute radiances for different cloud thicknesses and heights over various backgrounds. These radiances are used to develop parameterizations of top-of-the-atmosphere visible reflectance and infrared emittance utilizing tables of reflectance as a function of cloud optical depth, viewing and illumination angles, and microphysics. This parameterization, which includes Rayleigh scattering, ozone absorption, variable cloud height, and an anisotropic surface reflectance, reproduces the computed top-of-the-atmosphere reflectances with an accuracy of [+-]6% for four microphysical models: 10-[mu]m water droplet, small symmetric crystal, cirrostratus, and cirrus uncinus. The accuracy is twice that of previous models. Bidirectional reflectance patterns from theoretical ice-crystal clouds are different from those of the theoretical water-droplet clouds. The ice-crystal phase functions produce significantly larger reflectances than the water-droplet phase function for a given optical depth. A parameterization relating infrared emittance to visible optical depth is also developed. Simulated cloud retrievals using the parameterization indicate that optical depths and cloud temperatures can be determined with an accuracy of [approximately]25% and [approximately]6 K for typical cirrus conditions. Sensitivity analyses show that the use of the water-droplet phase function to interpret radiances from a theoretical cirrostratus cloud will significantly overestimate the optical depth and underestimate cloud height by 1.5-2.0 km for nominal cirrus clouds. The parameterization developed here is economical in terms of computer memory and is useful for both simulation and interpretation of cloud radiance fields. 46 refs., 28 figs., 4 tabs.

• OSTI ID: 6336468
• Journal Information: Journal of the Atmospheric Sciences; (United States), Journal Name: Journal of the Atmospheric Sciences; (United States) Vol. 50:9; ISSN JAHSAK; ISSN 0022-4928
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
CLOUDS
COHERENT SCATTERING
COMPARATIVE EVALUATIONS
COMPUTER CALCULATIONS
DATA COVARIANCES
DIAGRAMS
DIMENSIONS
DROPLETS
EVALUATION
FUNCTIONS
HYDROGEN COMPOUNDS
ICE
INFRARED SPECTRA
LEVELS
OPTICAL DEPTH CURVE
OPTICAL PROPERTIES
OXYGEN COMPOUNDS
OZONE
PARTICLES
PHYSICAL PROPERTIES
RAYLEIGH SCATTERING
SCATTERING
SENSITIVITY ANALYSIS
SPECTRA
THICKNESS
VISIBLE SPECTRA
WATER