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AerGOM is a retrieval algorithm developed for the GOMOS instrument onboardEnvisat as an alternative to the operational retrieval (IPF). AerGOM enhancesthe quality of the stratospheric aerosol extinction retrieval due to theextension of the spectral range used, refines the aerosol spectralparameterization, the simultaneous inversion of all atmospheric species aswell as an improvement of the Rayleigh scattering correction. The retrievalalgorithm allows for a good characterization of the stratospheric aerosolextinction for a wide range of wavelengths.In this work, we present the results of stratospheric aerosol extinctioncomparisons between AerGOM and various spaceborne instruments (SAGE II,SAGE III, POAM III, ACE-MAESTRO and OSIRIS) for different wavelengths. Theaerosol extinction intercomparisons for λ < 700 nm and above 20 kmshow agreements with SAGE II version 7 and SAGE III version 4.0 within ±15 % and ±45 %, respectively. There is a strong positive biasbelow 20 km at λ < 700 nm, which suggests that cirrus clouds atthese altitudes have a large impact on the extinction values. Comparisonsperformed with GOMOS IPF v6.01 alongside AerGOM show that at shortwavelengths and altitudes below 20 km, IPF retrievals are more accurate whenevaluated against SAGE II and SAGE III but are much less precise than AerGOM.A modified aerosol spectral parameterization can improve AerGOM in thisspectral and altitude range and leads to results that have an accuracysimilar to IPF retrievals. Comparisons of AerGOM aerosol extinctioncoefficients with OSIRIS and SAGE III measurements at wavelengths larger than700 nm show a very large negative bias at altitudes above 25 km. Therefore,the use of AerGOM aerosol extinction data is not recommended for λ > 700 nm.Due to the unique observational technique of GOMOS, some of the resultsappear to be dependent on the star occultation parameters such as starapparent temperature and magnitude, solar zenith angle and latitude ofobservation. A systematic analysis is carried out to identify biases in thedataset, using the various spaceborne instruments as references. The qualityof the aerosol retrieval is mainly influenced by the star magnitude, as wellas star temperature to a lesser degree. To ensure good-quality profiles, wesuggest to select occultations performed with star magnitude M < 2.5 andstar temperature T > 6 × 103 K. Stray-light contamination isnegligible for extinction coefficients below 700 nm using occultationsperformed with a solar zenith angle  > 110° but becomes important at largerwavelengths. Comparison of AerGOM results in the tropics shows an enhancedbias below 20 km that seem to confirm cirrus clouds as its cause. There arealso differences between mid-latitude and tropical observations that cannotyet be explained, with a bias difference of up to 25 %.This bias characterization is extremely important for data users and mightprove valuable for the production of unbiased long-term merged dataset

AerGOM, an improved algorithm for stratospheric aerosol extinction retrieval from GOMOS observations – Part 2: Intercomparisons