Investigation of the Impact of Horizontal Inhomogeneities on MIPAS/ENVISAT Products

Several studies have highlighted the importance of properly account for temperature horizontal inhomogeneities in the retrieval of atmospheric constituents from limb sounding infrared space-born instruments. For this reason 2-dimensional (2-D) tomographic retrieval algorithms have been developed to take into account the inhomogeneity of the atmosphere in the along-track direction of limb- measurements. Among these algorithms the Geofit-Multi Target Retrieval (GMTR) by [1]) system was specifically developed to process Michelson Interferometer for Passive Atmospheric Sounding (MIPAS /ENVISAT) measurements and was proven to minimize the anomalies observed on MIPAS/ENVISAT products retrieved with 1-D codes [2]. In this study, we exploit the 2-D Forward Model (FM) of the GMTR system to evaluate the impact of the horizontal inhomogeneities on ESA MIPAS/ENVISAT level 2 products retrieved with 1-D approach. The 2-D FM is used to produce synthetic MIPAS/ENVISAT observations simulated in a realistic horizontal inhomogeneous atmosphere that are analyzed using a 1-D retrieval system. We also investigate the advantages and disadvantages of the use of an intermediate approach between the 1-D and 2-D retrieval through the implementation of a temperature gradient along the orbit. The impact of horizontal Volume Mixing Ratio (VMR) gradients along the orbit is also evaluated.