Comparison of line-by-line and curtis matrix calculations for the vibrational temperatures and radiative cooling of the CO 2 15 μm bands in the middle and upper atmosphere

Abstract

A comparison of the iterative line-by-line RAD, and the inverse modified Curtis matrix (MCM) non-LTE models has been undertaken with the purpose of studying the effect of radiative transfer algorithms on the non-LTE populations of the CO 2( v 2) levels and on the 15 μm radiative cooling rates produced by the bands originating from them. The comparison has been carried out for a large range of model input parameters which include CO 2 strong and weak 15 μm bands, extreme atmospheric temperature structures, a large altitude interval (40-160 km), and extreme values for kinetic parameters. A good general agreement for the populations and cooling rates for all bands and conditions is found. The model differences for the vibrational temperatures and cooling rates are generally smaller than 2 K and 0.5 K/day, respectively. This result is in contrast with the large differences found when compared with some previous non-LTE models.