The K-Distribution Method for a SW Radiative Transfer Model

Ackerman, T. P., University of Washington

General Circulation and Single Column Models/Parameterizations

Cloud Modeling

Kato, S., Ackerman, T.P., Mather, J.H., and Clothiaux, E.E., 1999: "The K-distribution Method and Correlated-k Approximation for a Shortwave Radiative Transfer Model," Journal of Quantitative Spectroscopy & Radiative Transfer, 62(1):109-121.

Absorption cross sections are tabulated for water vapor, including continuum absorption, ozone, oxygen and carbon dioxide in the solar spectral region by adopting the k-distribution method. These tables are generated based on line-by-line code results for ranges of total pressure, temperature and water vapor concentration typical of values throughout the troposphere. These tables are incorporated into a shortwave radiative transfer code, which has 32 wavelength intervals across the solar spectrum, by using the correlated-k approximation in order to evaluate the accuracy in the broad band direct normal irradiance computation.

A comparison of the direct normal irradiance with MODTRAN3 demonstrates that these tables can be used for shortwave broad band irradiance computations; the difference in the transmissivity is within 0.01 throughout most of the solar spectral region.

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