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Computing Planck function for each longwave g point: The emission in a particular band and for a particular layer of the atmosphere is computed by considering the average Planck function over the spectral domain covered by the band (DISORT approach). Each g point in a band uses this Planck function in the radiative transfer, and then then a weighted average of the fluxes is computed according to the weight given to each g point. The Planck function is not accounted for in computing the coefficients (i.e. not accounted for in computing g).
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