THE CORRELATED KAPPA-DISTRIBUTION TECHNIQUE AS APPLIED TO THE AVHRR CHANNELS

Correlated k-distributions have been created to account for the molecu lar absorption found in the spectral ranges of the five Advanced Very High Resolution Radiometer (AVHRR) satellite channels. The production of the k-distributions was based upon an exponential-sum fitting of tr ansmissions (ESFT) technique which was applied to reference line-by-li ne absorptance calculations. To account for the overlap of spectral fe atures from different molecular species, the present routines made use of the multiplication transmissivity property which allows for consid erable flexibility, especially when altering relative mixing ratios of the various molecular species. To determine the accuracy of the corre lated k-distribution technique as compared to the line-by-line procedu re, atmospheric flux and heating rate calculations were run for a wide variety of atmospheric conditions. For the atmospheric conditions tak en into consideration, the correlated k-distribution technique has yie lded results within about 0.5% for both the cases where the satellite spectral response functions were applied and where they were not. The correlated k-distribution's principal advantage is that it can be inco rporated directly into multiple scattering routines that consider scat tering as well as absorption by clouds and aerosol particles.