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Generation of TOA Radiative Fluxes from the GERB Instrument Data. Part II: First Results

Generation of TOA Radiative Fluxes from the GERB Instrument Data. Part II: First Results. Nicolas Clerbaux and GERB team Royal Meteorological Institute of Belgium EUMETSAT users conference – Weimar – 30 Sept. 2003. Content. First result of using SEVIRI in the RMIB GERB data processing system:

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Generation of TOA Radiative Fluxes from the GERB Instrument Data. Part II: First Results

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  1. Generation of TOA Radiative Fluxes from the GERB Instrument Data.Part II: First Results Nicolas Clerbaux and GERB team Royal Meteorological Institute of Belgium EUMETSAT users conference – Weimar – 30 Sept. 2003

  2. Content First result of using SEVIRI in the RMIB GERB data processing system: • NB -> BB conversions, • Scene identification, • Anisotropic factor for the radiance-to-flux conversions.

  3. RMIB GERB/SEVIRI Overview • Estimation of unfiltered reflected solar and emitted thermal radiative radiances and fluxes at the TOA from the SEVIRI: • NB-to-BB radiances • radiance-to-flux • Comparison of BB radiance with GERB measurements -> SW and LW correction factors to apply to the SEVIRI radiances and fluxes.

  4. SEVIRI NB->BB conversion • Need: for the GERB unfiltering (cf. S. Dewitte presentation) and for the resolution enhancement of GERB data. • Method: use of 2nd order regression on the NB radiances: • Validation with the GERB BB radiance

  5. Longwave Ratio GERB/SEVIRI GERB defective pixel

  6. Shortwave Ratio GERB/SEVIRI SEVIRI overestimation over desert

  7. SEVIRI Scene Identification • Needed for the shortwave ADMs selection (surface type, cloud fraction, optical depth t and phase). • Method: building of clear sky reflectance images for the SEVIRI VIS 0.6 and VIS 0.8mm (each 10 days) and analyse of the difference with actual NB reflectance. NIR 1.6 and IR for for cloud phase. • TBD: aerosol and wind speed over clear ocean, fresh snow detection.

  8. SEVIRI False Color Clear sky Reflectance Image R=rcs (0.8mm) G=rcs (0.8mm) B=rcs (0.6mm) Ref: A. Ipe et al., Pixel -Scale Composite TOA Clear-Sky Reflectances for Meteosat-7 Visible Data, Journal of Geophysical Research, in press.

  9. VIS 0.6 or VIS 0.8 ? Automatic selection of the more appropriated channel for cloud detection and cloud optical depth estimation: 0.6mm 0.8mm

  10. Cloud Optical DepthRetrieval Use of 24 look-up-tables: for: - VIS 0.6 and VIS 0.8 - 6 surface types - Ice and water clouds with: -r = actual reflectance -rcs = clear sky refl. -(qv,qs,j)=viewing geom.

  11. Shortwave Angular Dependency Models Use of the 592 CERES-TRMM SW ADMs:

  12. Longwave Angular Dependency Models with Ref: N. Clerbaux et al., Outgoing longwave flux estimation: improvement of angular modelling using spectral information, Rem. Sens.,2003, 85, 369-395.

  13. Conclusions • SEVIRI data looks fine (incl. calibration) • NB->BB seems OK over most of the surfaces and cloud types but fails over desert (to be improved), • Scene identification seems OK, • Radiance-to-flux conversions: to be validated using CERES data on EOS Terra and Aqua satellites. • Goal: processing of GERB using SEVIRI data operational for end of october 2003.

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