Aerosol retrievals from METEOSAT-8 - CM SAF

SAF on Climate Monitoring Visiting Scientists Report Doc. No: 1.0
Issue : 1.0
Date : 4 October 2006
Fig. 12 to 15 present for the 4 AERONET locations the relationship between observed and
MSG/SEVIRI retrieved Aerosol Optical Thickness. Big discrepancies appear for some hours of the
day (around 13:00 UTC for Toulouse and 12:00 UTC for Blida), which should be due to the use of
an inappropriate phase function, especially for particular scattering angles. For the El Arenosillo
station, MSG tends to overestimate the AOT between 12:00 and 15:00 UTC. We can remark that
the standard deviation in the box of 5x5 pixels is high during these hours, in the order of 0.2,
whereas the standard deviation is less than 0.06 for the rest of the day. Large standard deviations
can be used as an index of the quality, indicating large spatial variability of the surface reflectance
or the presence of thin clouds. As expected the agreement is better for sites where the surface
reflectance is not too high (Toulouse and Ispra) and when the aerosol is surely non dust. In other
places with high surface reflectance and presence of dust, the quantitative comparison is not yet
satisfactory.
Fig.12: Temporal variation of the aerosol optical thickness at 670nm derived from AERONET and
MSG for the 2 nd and 14 th July 2005 over Toulouse (South-West of France)
- 28 -