Analysis of averaged broadband residuals between MIPAS-Envisat spectra and line-by-line calculations

MIPAS-Envisat spectra are compared to broadband spectra calculated with the KOPRA radiative transfer algorithm, using atmospheric temperature and trace gas concentrations which have been derived from small spectral ranges, so called microwindows, of the MIPAS-Envisat spectra. The objective is to detect instrumental problems and inconsistencies in the retrievals as well as in the spectroscopic dataset. The HITRAN 2008 spectroscopic database is used for all calculations. In this paper, we discuss residuals between modelled and measured broadband spectra which are caused by inconsistencies in the HITRAN O3 and HNO3 datasets. We conclude that the intensity of the 16O16O18O Q-branch around 1090.3 cm−1 is too low. HNO3 spectroscopy has turned out to be largely improved in the HITRAN 2008 version. However, even these spectroscopic data still produce spectral radiances too low at 885.45 and 886.15 cm−1. Generally the calculated spectral radiance in the ν5/2ν9 region is slightly too low.

► We perform broadband radiative transfer calculations using HITRAN 2008. ► We compare results to MIPAS-Envisat Spectra. ► HNO3 spectroscopy shows inconsistencies near 885 and 886 cm−1. ► O3 spectroscopy shows inconsistencies near 1090 cm−1.