Left: Total column ozone in DU on 11 Sep 2004 from the operational ECMWF analysis (top),
from an analysis experiment assimilating SCIAMACHY total ozone products from KNMI (middle) and from gridded
daily TOMS data (bottom). Right: The two top panels show the zonal mean ozone values from the experiments
(solid lines) and from TOMS data (open circles), the bottom panel shows the relative difference in % between
the analysis using SCIAMACHY and TOMS (taken here as reference). Improvement due to the use of SCIAMACHY is
noticeable, especially over the South Pole.