Impact of molecular absorption spectroscopy data on methane retrieval from SCIAMACHY and GOSAT shortwave infrared spectra

Abstract

Methane is an important species of Earth's atmosphere, highly relevant for climate. Accordingly, a large number of spaceborne sensors are observing this species in the thermal, near and shortwave infrared. For the analysis of shortwave infrared spectra measured by SCIAMACHY aboard the Envisat and the simulated spectra of GOSAT, respectively, in this master thesis the Beer InfraRed Retrieval Algorithm (BIRRA) was used to retrieve methane column densities from the radiance with respect to different sets of observations. Our investigations are based on the separate comparisons of retrieved fitting parameters with respect to the different molecular absorption spectroscopic databases in order to account for their impact on the retrieval quality. After the analysis, it can be concluded that HITRAN 2012 and GEISA 2015 have a comparable performance with good retrieval quality, HITRAN 1986 achieves the worst quality. Moreover, several useful suggestions are provided for the further improvement on retrieval according to the study.