Development of Algorithms for Atmospheric Methane Distribution Retrieval from METOP/IASI Spectra

Abstract

The applicability of the Levenberg–Marquardt method, modified for the case of inaccessibility of a priori covariance matrices for methane vertical profiles, to atmospheric methane total column retrieval from the spectra measured by METOP/IASI is studied. The method and algorithm are software implemented together with an iterative evaluation of a posteriori covariance matrices and averaging kernels for each individual case of retrieval. This allows selection of the results based on properties of both matrices. The comparison between our results and IASI standard methane products retrieved from the same spectra shows their satisfactory agreement.