Aerosol retrievals from METEOSAT-8 - CM SAF

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SAF on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 11:00 UTC 12:00 UTC 13:00 UTC 14:00 UTC 15:00 UTC 16:00 UTC 17:00 UTC 8:00 UTC 1 Figure 8: Reference surface reflectance map over Europa from the period 1-14 July 2005 in SEVIRI channel 1. The color scale is from 0.00 (dark blue) to 0.40 (red). - 22 -

SAF on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 Figure 9: Example of surface reflectance of reference at 670nm for different geographical locations from the period 1-14 th July 2005. In conclusion, the reference surface reflectance maps are built from the minimum value of the Rayleigh corrected reflectance over a 14 day period. Although they are contaminated by a residual aerosol loading but we have neglected this so far. The spatial cover is very good, and only in small areas very high or missing values are found. It is suggested that these areas were most of the time covered by clouds during the compositing period. The spatial variations of the reflectance at 670nm are most of the time smooth. However, in some part of central Europe and Norway large variations in surface reflectance are observed, which are due to frequent cloud cover. Although we limited our report to the European continent, it can be easily extended to the disc observed by MSG/SEVIRI. Thus, the reference surface reflectance map has also been calculated for the complete northern part of the disc as shown in Appendix A. 6.1.4 MSG/SEVIRI aerosol optical thickness retrieval algorithm Knowing the surface reflectance in the appropriate geometry, the retrieval of the aerosol optical thickness is made in two steps. In the first step we estimate the aerosols path reflectance using a rough approximation. The aerosol path reflectance (R aer ) is the difference between the Rayleigh - 23 -

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