The primary objectives of this study are to investigate the ability of narrow-band models to accurately calculate the radiative effects of infrared-active molecules, and to then employ the narrow-band models to investigate the radiative effects which the minor trace gases CH4, N2O, NO2, NH3, SO2, and OCS have upon the transfer of thermal infrared radiation through Earth's atmosphere.For the atmospheric application of narrow-band models there are several issues involved. First, the ability of the narrow-band model to accurately calculate the total band absorptance for a homogeneous gas (i.e., constant temperature and pressure). Second, the validity of the associated scaling approximation which is required when the narrow-band model is employed under atmospheric conditions where temperature and pressure vary. Third, the applicability of the transmissivity multiplication property to accurately account for the overlap of the absorption bands of different gases.
Results from this investigation have shown that, in general, the Malkmus narrow-band model with an interval width of 5 cm-1 is fairly accurate in reproducing the total band absorptance results as calculated for a homogeneous gas by the reference line-by-line procedure. Furthermore, the Curtis-Godson scaling procedure when employed with a narrow-band model provides an accurate means of accounting for atmospheric temperature and pressure variations for a gas with an altitude invariant mixing ratio. Finally, the transmissivity multiplication property when utilized by a random-line narrow-band model is a valid technique to account for the overlap of the absorption bands of different gases. Care should be taken, however, since as shown in this study, there are notable exceptions to the above results.
The results of flux calculations for clear sky atmospheres with the above contingent of minor trace gases along with H2O, CO2, and O3, have demonstrated that a doubling of the minor trace gases will collectively yield a radiative effect comparable to a doubling of CO2. Furthermore, it should be noted, that on a per molecule basis, the minor trace gases possess a far greater radiative effect than CO2,