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We report on the dependence of ozone volume mixing ratio profiles, retrieved fromlimb emission infrared spectra of the Michelson Interferometer for Passive AtmosphericSounding (MIPAS), on different retrieval setups such as the treatment of the backgroundcontinuum, cloud filtering, spectral regions used for analysis and a series of furthermore technical parameter choices. The purpose of this investigation is to better understandthe error sources of the ozone retrieval, to optimize the current retrieval setup and todocument changes in the data versions.It was shown that the cloud clearing technique used so far (cloud index 1.8) doesnot reliably exclude all cloud-contaminated spectra from analysis. Through analysis ofspectra calculated for cloudy atmospheres we found that the cloud index should be increasedto a value of 3.0 or higher. Further, it was found that assignment of a common backgroundcontinuum to adjacent microwindows within 5 cm−1 is advantageous, because it sufficientlyrepresents the continuum emission by aerosols, clouds and gases as reported in the literature,and is computationally more efficient.For ozone retrieval we use ozone lines from MIPAS band A (685–970 cm−1)and band AB (1020–1170 cm−1) as well. Therefore we checked ozone retrievalswith lines from bands A or AB only for a systematic difference. Such adifference was indeed found and could, to a major part, be attributed to thespectroscopic data used in these two bands, and to a minor part to neglection of modellingof non-local thermodynamic (non-LTE) emissions. Another potential explanation, a bias inthe radiance calibration of level-1B spectra of bands A and AB, could largely be ruled outby correlation analysis and inspection of broadband spectra. Further upgradesin the ozone retrieval consist of applicationof an all-zero a-priori profile and a weaker regularization. Finally, the ozonedistribution obtained with the new retrieval setup (data versions V3o_O3_7) wascompared to the data version used before (V2_O3_2). Differences are smallerthan $pm$0.4 ppmv in the altitude region 15–50 km. Further, differences to ozone measuredby the HALogen Occultation Experiment (HALOE) on the Upper Atmospheric Research Satellite(UARS) are partly reduced with the new MIPAS data version

Retrieval of stratospheric ozone profiles from MIPAS/ENVISAT limb emission spectra: a sensitivity study