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. Ozone profile retrieval from nadir-viewing satellite instruments operating inthe ultraviolet–visible range requires accurate calibration ofLevel-1 (L1) radiance data. Here we study the effects of calibrationon the derived Level-2 (L2) ozone profiles for three versions ofSCanning Imaging Absorption spectroMeter for Atmospheric ChartograpHY(SCIAMACHY) L1 data: version 7 (v7), version 7 with m-factors(v7 mfac ) and version 8 (v8). We retrieve nadir ozone profilesfrom the SCIAMACHY instrument that flew on board Envisat using theOzone ProfilE Retrieval Algorithm (OPERA) developed at KNMI with a focus onstratospheric ozone. We study and assess the quality of these profiles andcompare retrieved L2 products from L1 SCIAMACHY data versions from theyears 2003 to 2011 without further radiometric correction. From validation ofthe profiles against ozone sonde measurements, we find that the v8 performsbetter than v7 and v7 mfac due to correction for the scan-angledependency of the instrument's optical degradation. Validation for the years 2003 and 2009 with ozone sondes shows deviations ofSCIAMACHY ozone profiles of 0.8–15 % in the stratosphere(corresponding to pressure range ∼  100–10 hPa) and 2.5–100 % inthe troposphere (corresponding to pressure range ∼  1000–100  hPa ), depending on the latitude and the L1 versionused. Using L1 v8 for the years 2003–2011 leads to deviations of ∼  1–11 % in stratospheric ozone and ∼  1–45 % intropospheric ozone. The SCIAMACHY L1 v8 data can still be improved upon in the265–330  nm range used for ozone profile retrieval. The slit functioncan be improved with a spectral shift and squeeze, which leads to a fewpercent residue reduction compared to reference solar irradiance spectra.Furthermore, studies of the ratio of measured to simulated reflectance spectrashow that a bias correction in the reflectance for wavelengths below300  nm appears to be necessary.

Evaluation of SCIAMACHY Level-1 data versions using nadir ozone profile retrievals in the period 2003–2011