Low resolution spectral modeling of water vapor and carbon dioxide is carried out by applying the weighted-sum-of-gray-gases model (WSGGM) to each narrow band. For a given narrow band, focus is placed on proper modeling of gray gas absorption coefficients vs. temperature relation. Five primary models and a modified model are suggested and tested with water vapor as the test gas. The gray gas absorption coefficients become the basic radiative properties which can be used for any solution methods for the Radiative Transfer Equation(RTE). Comparison between the modeled emissivity and the 'true' emissivity obtained from a high temperature statistical narrow band parameters (Grosshandler, 1980 ; Soufiani and Taine, 1997) is made for the total spectrum as well as for a few typical narrow bands. Application of the model to nonuniform gas layers is also made. Low resolution spectral intensities at the boundary are obtained for uniform, parabolic and boundary layer type temperature profiles using the obtained WSGGM's with several gray gases. The results are compared with the narrow band spectral intensities obtained by a narrow band model-based code with the Curtis-Godson approximation. Good agreement is found between them. Local heat source strength distribution is also compared for the cases of Kim et al(1991), which again gives promising agreement.
Finally, data bases including optimized modeling parameters and total and low resolution spectral weighting factors are given for water vapor, carbon dioxide and their mixtures. These data and model can be appropriately applied to any radiative transfer equation solver.
