Aerosol retrievals from METEOSAT-8 - CM SAF

More documents

Recommendations

Info

SAF on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 Fig. B3: SEVIRI aerosol optical thickness at 670nm at 14:00 UTC for an area with fires in the North of Porto. - 42 -
SAF on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 Appendix C Clear sky observations and contribution of the temporal resolution of MSG/SEVIRI Dominique Jolivet and Didier Ramon (HYGEOS) & Jérôme Riedi and Jean-Marc Nicolas (LOA) The algorithm to separate cloud free from cloud contaminated or cloud filled pixels has been developed with the intention of being applicable globally without requiring ancillary data such as surface temperature or atmospheric profiles. Each test implemented within the algorithm has been designed based on fundamental physical differences (emissivity, spectral behaviour) between clouds and surface. Many lessons learned from the Moderate Resolution Imaging Spectroradiometer (MODIS), regarding discrimination between clouds and heavy aerosols events or sunglint for instance (spatial variability, spectral behaviour), have been taken into account in the design of this cloud detection scheme. However, the present algorithm shall not be considered as just a simplified MODIS-like cloud mask because : (i) some tests have been adapted and modified to account for the differences in spectral channels, calibration and/or spatial resolution and make them applicable to SEVIRI, (ii) the number of tests used is currently much smaller than the one used in the operational MODIS algorithm (Ackerman et al. 1998; Platnick et al. 2003) and (iii) the decision logic differs significantly from the one used for MODIS (http://www-loa.univ-lille1.fr/~riedi/). The input to the SEVIRI cloud detection algorithm consists of normalized reflectances from the visible (0.6 and 0.8 µm) and near-infrared (1.6 µm) channels, whereas brightness temperatures are used from the thermal infrared channels (3.8, 8.7, 10.8 and 12.0 µm). Additionally, the algorithm uses ancillary data on solar and viewing geometry and a land/sea map but none is required from model reanalysis. There are spectral threshold and spatial coherence cloud detection tests that are different for land and ocean surfaces. The various tests implemented are grouped together in such a - 43 -
Page 1 and 2: SAF on Climate Monitoring Visiting
Page 41: SAF on Climate Monitoring Visiting
Page 51: SAF on Climate Monitoring Visiting

Aerosol retrievals from METEOSAT-8 - CM SAF

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?