Evaluation of Satellite Total Ozone and NO2 Columns Using the SAOZ UV-Vis Network

The full series of SAOZ network total ozone measurements in the visible Chappuis bands has been revised according to the spectral analysis and Air Mass Factor (AMF) settings recommended by the NDACC UV-Vis Working Group (Hendrick et al., 2011). They have been compared to overpass observations from the TOMS, GOME-GDP4, SCIAMACHY-TOSOMI, SCIAMACHY-OL3, OMI-TOMS, and OMI-DOAS satellite instruments. Significant improvement is obtained after applying the new O3 AMFs, although systematic seasonal differences between SAOZ and all other instruments still remain. These are shown to originate from (i) a stratospheric temperature and solar zenith angle (SZA) dependencies in the satellites retrievals, (ii) longitudinal modulations and seasonal variations of tropospheric ozone columns not accounted for in the TOMS V8 ozone profile climatology used for calculating the AMFs, and (iii) uncertainties on the climatological stratospheric ozone profiles for polar winter conditions. For those measurements mostly sensitive to stratospheric temperature like TOMS, OMI-TOMS or to SZA like SCIAMACHY-TOSOMI, the application of temperature and SZA corrections results in the almost complete removal of the seasonal difference with SAOZ, improving significantly the consistency between satellite and ground-based total ozone series. However, small but sometimes significant biases remain after applying those corrections. A similar exercise is in progress with SAOZ NO2 data sets, using AMFs calculated from a profile climatology based on HALOE, SAGE II, POAM III and SAOZ balloon profiles. The consistency with GOME/ERS2, SCIAMACHY/ENVISAT and OMI/AURA NO2 total columns is also currently 5 examined. In this presentation, we will focus on the resulting evaluation of ozone and NO2 total columns biases of the various satellite instruments