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contributor authorFu, Qiang
contributor authorLiou, K. N.
date accessioned2017-06-09T14:31:06Z
date available2017-06-09T14:31:06Z
date copyright1992/11/01
date issued1992
identifier issn0022-4928
identifier otherams-20785.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4157051
description abstractThe correlated k-distribution method for radiative transfer in nonhomogeneous atmospheres is discussed in terms of the physical and mathematical conditions under which this method is valid. Two correlated conditions are necessary and sufficient for the exact transformation of the wavenumber integration to an integration over the cumulative probability (g), a monotonically increasing and smooth function in the absorption coefficient space. These conditions involve the use of a reference condition to define the absorption coefficient and an assumption concerning the ordering of the absorption coefficient. The correlated conditions are exact in the context of a single line, periodic lines, and the strong- and weak-line limits. In realistic atmospheres, these assumptions are best for adjacent levels but produce increasing blurring or deviations for distant levels. We investigate the blurring of the correlated assumptions on the computations of fluxes and heating rates based on ?exact? line-by-line results, using a variety of atmospheric profiles and spectral intervals containing principal absorbing gases. In the thermal infrared, errors in fluxes are less than 0.2% for H2O, CO2, CH4, and N2O, and ?2% for O3. Errors in heating rates are less than 0.01 K day?1 for these gases below ?30 km. Larger errors of ?0.1 K day?1 can occur at some levels above this height. For H2O lines in the solar region, errors in fluxes and heating rates are within 0.05% and 0.01 K day?1, respectively. Based on numerical experimentation, we find that the number of g values ranging from 1 (for weak bands) to ?10 (for strong bands) are usually sufficient to achieve acceptable accuracy for flux and heating rate calculations. The correlated k-distribution method differs fundamentally from the traditional approach that employs scaling approximations and band models to separate height and wavenumber integrations for transmittance calculations. The equivalent k values for various gases computed from this approach can be directly incorporated in the multiple-scattering program involving cloud and aerosol particles.
publisherAmerican Meteorological Society
titleOn the Correlated k-Distribution Method for Radiative Transfer in Nonhomogeneous Atmospheres
typeJournal Paper
journal volume49
journal issue22
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/1520-0469(1992)049<2139:OTCDMF>2.0.CO;2
journal fristpage2139
journal lastpage2156
treeJournal of the Atmospheric Sciences:;1992:;Volume( 049 ):;issue: 022
contenttypeFulltext


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