Intercomparison between spectral databases using REFIR/BB and BOMEM MR100 down-welling spectra in the range 450-900 cm-1

Ground based Fourier Transform Spectrometer (FTS) observations from two field campaigns in the 2004 summer have been considered in this study and compared to calculations. Synthetic spectra radiance has been obtained using an up-to-date line-by-line radiative transfer model along with three different spectral databases: HITRAN2000, HITRAN2004 and GEISA2003. Observations have been recorded with two FTS, which cover different spectral ranges. It has been found that synthetic radiance computations fit quite well to the data, even though the goodness of the fit depends on the spectral database. In particular, differences in the spectral residual behaviour appear in the short wave part of water vapour rotational band (450-600 cm-1). In this range GEISA2003 provides almost the same results as those of HITRAN2000, while HITRAN2004 shows a mixed behaviour: better than the first two in a large region of the spectral range, but worse at very few specific wave numbers. On overall, HITRAN2004 yields the highest consistency with the observations. Sensitive differences appear also between HITRAN (both) and GEISA for the CO2 Q-branches at 620 cm-1, 720 cm-1 and 792 cm-1.