Aerosol retrievals from METEOSAT-8 - CM SAF

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<strong>SAF</strong> on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 corrected reflectance and the surface reflectance of reference such as: R aer =R Ray_corrected -R surf_ref In the second step we assume only single scattering and the aerosol type (and then phase function), the aerosol optical thickness (AOT) is derived as follows: AOT=Raer . 4 . cos(θs) cos(θv)/ P(Θ) where: θs is the solar zenith angle, θv is the viewing zenith angle and P(Θ) is the value of the aerosol phase function for the scattering angle Θ. We assume a continental model with an Angstrom coefficient of 1.0, a real refractive index m r of 1.44 and an imaginary index mi of 0.0 which means there is no absorption (This aerosol model is used in MERIS LUT's). Of course the single scattering assumption in the radiative transfer model will lead to erroneous retrieval for large value of the AOT. Fig. 10 resumes the schema of the retrieval method and Fig, 11 shows the aerosol optical thickness at 670nm for the 14 th July 2005 over Europe and for every hour between 05:00 UTC and 18:00 UTC. The AOT maps are very noisy for partly cloudy areas as seen in Fig.11. Efforts must be planned to use and apply a better cloud mask. However, the coverage is very good. An aerosol front crossing the Pyrenees Mountains can be seen and be followed with correct land-sea continuity. A dust event over North Africa is detected both over land and the Mediterranean Sea. We also mapped the retrieved aerosol optical thickness over ocean assuming a Lambertian surface with an albedo of 0.01 at 670nm. But, we plan in the near future to derive the sea reflectance with the identical method used for the continental surface reflectance. In Appendix B maps of retrieved AOT are given for the forest fires in Portugal around the 10 th July 2005. - 24 -
<strong>SAF</strong> on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 Figure 10: Flow chart of the aerosol optical thickness retrieval method. - 25 -
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Aerosol retrievals from METEOSAT-8 - CM SAF

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