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Overview of the “Geostationary Earth Radiation Budget (GERB)” Experience.

Overview of the “Geostationary Earth Radiation Budget (GERB)” Experience. Nicolas Clerbaux Royal Meteorological Institute of Belgium (RMIB) In collaboration with: Imperial College, UK. Rutherford Appleton Laboratory (RAL), UK. GERB International Science Team (GIST). What it GERB ?.

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Overview of the “Geostationary Earth Radiation Budget (GERB)” Experience.

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  1. Overview of the “Geostationary Earth Radiation Budget (GERB)” Experience. Nicolas Clerbaux Royal Meteorological Institute of Belgium (RMIB) In collaboration with: Imperial College, UK. Rutherford Appleton Laboratory (RAL), UK. GERB International Science Team (GIST).

  2. What it GERB ? • New instrument on the Meteosat Second Generation satellites of EUMETSAT, • First broadband imager radiometer observing the Earth from a geostationary satellite

  3. Outline of the talk • The GERB mission/science goals : why we need new measurements of the Earth Radiation Budget (ERB), • Interest of the Meteosat field-of-view, • GERB instrument, data processing, derived products and current status, • Examples of GERB data usage

  4. The Earth Radiation Budget (ERB)

  5. Diurnal and synoptic variability Uganda Kenya Lake Victoria Rwanda Burundi Congo Tanzania Meteosat-8 images – 12 July 2004

  6. GERB Mission Science goals • Measurement of the ERB with high temporal sampling thanks to the geostationary orbit. • Improvement of climate models by better understanding the role of clouds and water vapour in the ERB, • Improvement of Numerical Weather Prediction (NWP) models by data assimilation or near real-time validation, • Synergy with low orbit satellites observations: improvement of the diurnal model, • Climate monitoring in the frame of the EUMETSAT Satellite Application Facility on Climate Monitoring (CM-SAF).

  7. Interest of the Meteosat Field-of-View (1/2) Aerosols Contrails Tropical Convection Cirrus Also: desertification, African monsoon, marine stratocumulus, vulcaneos, biomass burning, …

  8. Interest of the Meteosat Field-of-View (2/2) Well-mixed greenhouse gases Radiative effect of aerosols blue: cooling effect red: warming effect unit : W/m² Mineral dust Biomass burning

  9. GERB instrument, data processing, derived products and status • Characteristics • Scanning mechanism • Instrument data • Data processing • Derived images of solar and thermal flux • Current data status

  10. GERB characteristics WAVEBANDSTotal: 0.32 µm - 100.0 µm Shortwave, SW: 0.32 µm - 4.0 µm Longwave, LW (by subtraction): 4.0 µm - 100.0 µm RADIOMETRYSW LW Absolute Accuracy: < 1.0 % < 1.0 % Signal/Noise: 1250 400 Dynamic Range: 0-380 W m-2 sr-1 0-90 W m-2 sr-1 SPATIAL SAMPLING44.6  39.3 km (NS  EW) at nadir TEMPORAL SAMPLING15 minute SW and LW fluxes CYCLE TIMEFull Earth disc, both channels in 5 minutes CO-REGISTRATIONSpatial: 3 km wrt SEVIRI at satellite sub-point Temporal: Within 15 min of SEVIRI at each pixel INSTRUMENT MASS25 kg POWER 35 W DIMENSIONS 476 mm  275 mm  345 mm

  11. GERB scanning Satellite rotation period = 0.6 s 282 steps for full Earth disc = 169.2 s 2 channels: Total Total+quartz filter (SW) Average three scans in each channel to improve S/N Total repeat time = 169.2*6 ~ 17 min. 256 detector pixels 256 detector pixels Between each Earth scan, internal BB measurement taken for calibration At correct viewing geometry, calibration monitor records scattered solar light as a relative measure over time 262 steps 282 steps

  12. Measured Radiance Images total [W/m²/sr] shortwave [W/m²/sr]

  13. GERB data processing • Geolocation and calibration (RAL) • Radiance unfiltering: correction for the instrument spectral response f(l). • Conversion in flux: angular modelling of the radiation field • Scene identification (surface, cloudiness,…) • Application of angular models • Enhancement of the spatial resolution: 50km ->10km • Near real-time dissemination by RMIB • Long term archiving and dissemination (RAL) At the RMIB (Brussels)

  14. Derived Fluxes Images (50km) Thermal [W/m²] Solar [W/m²]

  15. Current Data Status • GERB acquisition on Meteosat-8 started December 2002 and is ongoing, • The instrument is operating well, is stable and the measurements have low noise • Cross-calibration with other instruments (CERES) indicates good performances of the instrument • GERB data processing is still under validation, public release expected for end of 2005. • GERB data will be available to the scientific community free of charge.

  16. Image courtesy NASA Example of usage (1/2) GERB solar flux MODIS image 27 January 2003

  17. Example of usage (2/2) UK-MO Unified Model GERB Solar Flux Thermal Flux (Courtesy UK Met Office)

  18. Conclusions • The GERB data is unique! • European initiative in operational climate monitoring • Long term mission (+/- 15 years): GERB instrument will fly on Meteosat-9, -10 and -11 • Interest for climate modelling and meteorology • Importantcontribution of the RMIB. • More info at: http://gerb.oma.be

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