Merged ozone profiles from four MIPAS Processors

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) was an infrared limb emission spectrometer on the Envisat platform. Currently, there are four MIPAS ozone data products, including operational Level-2 ozone product processed at ESA with the scientific prototype processor being operated at IFAC Florence and three independent research products: ISACCNR/University of Bologna, Oxford University and KIT-IMK/IAA. Here we present a dataset of ozone vertical profiles obtained by merging ozone retrievals from four independent Level 2 MIPAS Processors. We also discuss the advantages and the shortcomings of this merged product. As the four processors retrieve ozone in different parts of the spectra (microwindows), source measurements can be considered as nearly independent. The information content of the merged product is hence more important. The precision of the merged product is better than that of any parent dataset. The merging is performed on profile per profile base. Parent ozone profiles are weighted based on the corresponding covariance matrices, the correlations between different profile levels are taken into account. The intercorrelations between the processors' errors are evaluated statistically and are used in the merging. The height range of the merged product is 20-55 km, and statistical covariance matrices are provided as diagnostics. Validation of the merged dataset is performed by comparing it with ozone profiles from ACE-FTS and MLS. Even though the merging is not supposed to remove the bias, around the ozone volume mixing ratio peak the merged product has a smaller (up to 0.1 ppmv) bias with respect to ACE-FTS than any of the parent datasets. The bias with respect to MLS is of the order of 0.15 ppmv at 20-30 km height, and up to 0.45 ppmv at larger altitudes. Comparison with ACE-FTS looks better than with MLS, however this is the case for all parent processors as well.