Comparison of the MIPAS products obtained by four different L2 processors

MIPAS measurements on ENVISAT represents a unique database for the study of atmospheric composition. Four different retrieval codes have been developed for the analysis of MIPAS measurements and they have been used for the processing of the entire MIPAS mission. These are: the ESA processor, specifically designed for the near real time analysis of MIPAS measurements, but also used for the off-line analysis; the GMTR, performing a two-dimensional analysis of MIPAS measurements; the algorithm obtained by the joint effort of the Institut fur Meteorologie und Klimaforschung (IMK) at Forschungszentrum Karlsruhe and the Instituto de Astrofísica de Andalucía (IAA), capable of handling deviations from Local Thermodynamic Equilibrium (Non-LTE) and taking into account an horizontal gradient of temperature along the line of sight; and the algorithm MORSE developed at Oxford University, based on the Optimal Estimation approach and using the Reference Forward Model. The four retrieval algorithms differ for some assumptions in the forward model, for the spectral intervals used for the analysis and for the retrieval approach. Comparison between the products of the four codes is important in order to validate the consistency of the different choices. Zonal mean averages of temperature, water vapor, nitric acid, methane, nitrous oxide, nitrogen dioxide are compared for two selected years (2008 and 2009) and the results are discussed.