Measured-predicted molecular spectra at band-line resolution

Early ERIM measurements of hot-through-cold gas (CO₂, H₂O, N₂) emission-absorption spectra are replicated by modern line-band computations that incorporate independent fundamental line strength-frequency information. Close agreement is achieved for all cases by empirical adjustment of the line broadening function. Line spectra for CO₂ and H₂O computed at 0.001 cm⁻¹ resolution were integrated to 3.2 and 14 cm⁻¹ using a triangular slit function consistent with ERIM measurements for the 4.3 and 2.7 μm spectral regions. Band spectra computed at 0.1 cm⁻¹ resolution give close agreement with spectra generated at higher resolution. The findings demonstrate a merged line-band model for nonuniform path radiance and transmittance based on the line-sum spectral cross section for each piecewise-uniform path segment. The band-and-line transmittance become equivalent at high spectral resolution. - Highlights: • ERIM-1975 radiance transmittance spectra for H₂O-CO₂ in short-midwave infrared. • Comprehensive line strengths-frequencies from NASA-H₂O and CDSD-CO_2. • Merged line-band model based on broadened line-sum spectral cross section. • Empirical line-width function yields near-exact spectral match for all test conditions.