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Steven Dewitte and GERB team Royal Meteorological Institute of Belgium

Generation of TOA Radiative Fluxes from the Geostationary Earth Radiation Budget (GERB) Instrument Data I) Methods. Steven Dewitte and GERB team Royal Meteorological Institute of Belgium EUMETSAT users conference – Weimar - September 2003. Meteosat Second Generation. SEVIRI

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Steven Dewitte and GERB team Royal Meteorological Institute of Belgium

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  1. Generation of TOA Radiative Fluxes from the Geostationary Earth Radiation Budget (GERB) Instrument DataI) Methods Steven Dewitte and GERB team Royal Meteorological Institute of Belgium EUMETSAT users conference – Weimar - September 2003

  2. Meteosat Second Generation SEVIRI Spinning Enhanced Visible and InfraRed Imager GERB Geostationary Earth Radiation Budget

  3. Geostationary Earth Radiation Budget

  4. Overview • The GERB measurements • Validation of GERB radiances • GERB/SEVIRI synergy • Conclusions

  5. The GERB measurements • 2 channel radiometer: shortwave and total • 1 pair of images in 5’. shortwave total

  6. Radiances Measured: radiances filtered by spectral response • LTOT,LSW Calculated: longwave radiance • LLW = LTOT -A LSW Wanted: unfiltered radiances • Lsol = reflected solar radiance • Lth = emitted thermal radiance

  7. GERB radiance validation • comparison with Clouds and the Earth’s Radiant Energy System (CERES) measurements • CERES on TERRA in flight since 2000 • special CERES mode : Rotating Azimuth Plane Scan (RAPS) allows co-angular views with all GERB detectors

  8. 95% confidence intervals • Reflected solar radiance:GERB/CERES=0.990 +/- 0.017 =[0.974 - 1.007]target uncertainty = 2*0.01 = 0.02 -> OK ! • Emitted thermal radiance:GERB/CERES=0.982 +/- 0.016 =[0.966 - 0.998] target uncertainty = 2*0.005 = 0.01 -> OK

  9. GERB/SEVIRI synergy GERB derived spectral correction factor for SEVIRI based flux estimate SEVIRI derived unfilter factor for GERB measurement SEVIRI derived unfilter and angular conversion factor for GERB measurement

  10. Conclusions • The GERB instrument performs well in space. • The GERB broadband radiances have been validated by comparison with CERES. • Next step: validate GERB fluxes.

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