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.15: Temporal variation of the AOT at 670nm derived from AERONET and MSG for the 12th
and 14 th of July over Blida (Near Alger - Algeria)
In Fig. 16 we present the comparison between the MSG/SEVIRI and the MODIS aerosol product.
The two instruments capture the main patterns of the aerosol field but quantitative comparison is at
the moment difficult since we do not retrieve the AOT at the same wavelength. The background
AOT seems to agree well and large dust outbreak over North of Algeria and the Mediterranean Sea
is seen by the two instruments. There is a good land/ocean continuity of the aerosol front passing
over Spain and South of France for MSG and it is not so clear for MODIS. However some
discrepancies occur for cloud covered regions, for example in the centre of France where high AOT
are retrieved from MSG and MODIS observes mainly clouds instead of aerosols. There is
agreement between the two instruments over England where very high AOT are found. This
emphasizes one more time the fact that our cloud mask still has to be improved.
Finally these results are obtained with lots and sometimes strong assumptions but they are really
promising, especially because changes in aerosol amount over some locations are also seen by
MSG. Better agreements should be obtained using exact radiative transfer calculations and filters on
the number of pixel used for the mean calculation, threshold on the standard deviation and the
proximity of clouds.
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