GIST, Boulder, 31/03/2004 RMIB GERB Processing: overview and status S. Dewitte Royal Meteorological Institute of Belgium

GIST, Boulder, 31/03/2004 Overview u 1. Physical fundamentals u 2. External interfaces u 3. Methodology u 4. Internal division into subsystems u 5. Status

GIST, Boulder, 31/03/2004 GERB measurements u General measurement: filtered radiance L f u total (TOT) filtered radiance : micron u short wave (SW) filtered radiance : micron

GIST, Boulder, 31/03/2004 Thermal/solar radiance separation u L f SW = reflected solar radiation u synthetic long wave (LW) radiance L f LW =L f TOT -A L f SW u A is chosen such that for reference SW spectrum L f LW = emitted thermal radiation

GIST, Boulder, 31/03/2004 Removal of non flat spectral response effects u L f = measured radiance, filtered with spectral response instrument u L uf = wanted radiance, not filtered with spectral response instrument è unfilter factor L uf / L f must be estimated from spectral modelling è scene type dependent

GIST, Boulder, 31/03/2004 Flux estimation u F = wanted flux = integral of unfiltered radiance contributions from all directions of the upper hemisphere è angular conversion factor F/ L uf must be estimated from modelling of the angular distribution of the observed radiation è scene type dependent

GIST, Boulder, 31/03/2004 Interface scheme Interfaces to : u RAL = Rutherford Appleton laboratories u EUMETSAT = European METeorological SATellite exploitation u Users

GIST, Boulder, 31/03/2004 GERB input data u NANRG: Non Averaged Non Rectified Geolocated GERB filtered radiances u one pair of SW and TOT filtered radiances every 5 minutes u nominal resolution 50 km at nadir (PSF weighted)

GIST, Boulder, 31/03/2004 SEVIRI input data u (HRV), 0.6, 0.8, 1.6 micron: solar band channels u (3.8 micron: intermediate) u 6.2, 7.3, 8.7, 9.7, 10.8, 12, 13.4 micron: thermal channels u all used channels at resolution of 3 km at nadir

GIST, Boulder, 31/03/2004 Unfiltering and angular conversion methodology 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

GIST, Boulder, 31/03/2004 Thermal/solar separation methodology u contributions to filtered radiance estimated separately from SEVIRI –main quantities: L f SW,sol,SEVIRI L f LW,th,SEVIRI –small quantities: L f SW,th,SEVIRI L f LW,sol,SEVIRI u sum contributions L f SW,SEVIRI = L f SW,sol,SEVIRI + L f SW,th,SEVIRI L f LW,SEVIRI = L f LW,th,SEVIRI + L f LW,sol,SEVIRI

GIST, Boulder, 31/03/2004 Internal division into subsystems

GIST, Boulder, 31/03/2004 SEVIRI Processing u estimates filtered radiances at SEVIRI pixel level u estimates unfiltered radiances at SEVIRI pixel level u estimates fluxes at 3 x 3 SEVIRI pixel level –Uses CERES TRMM ADM for SW case. –Scene identification from SEVIRI è concentrates all the needed physical scene modelling from SEVIRI data

GIST, Boulder, 31/03/2004 GERB Processing u convolution of SEVIRI based filtered radiance estimates over GERB footprint u time interpolation from SEVIRI acquisition times to GERB acquisition times u flux estimation at GERB footprint level u temporal averaging of 3 5’ fluxes to 15’ flux è concentrates GERB-SEVIRI coregistration

GIST, Boulder, 31/03/2004 Geolocation u Nominal: use GGSPS geolocation derived from SEVIRI parameters (version 1) –Target accuracy: SEVIRI pixel u Currently used: match GERB to SEVIRI (version 2) –Accuracy: order half GERB pixel

GIST, Boulder, 31/03/2004 Resolution enhancement u From the flux estimation at low resolution (GERB footprint), compatible fluxes at higher resolution (3 x 3 SEVIRI pixels) are calculated. u The compatible fluxes are corrected SEVIRI based flux estimates. u The same correction factors can be applied to the SEVIRI based unfiltered radiance estimates. è concentrates resolution enhancement of GERB by SEVIRI

GIST, Boulder, 31/03/2004 Status -software u Full system running since 19/12/2003: –Geolocation based on matching (version 2) –SEVIRI as imager (G2/SEV1) u Cloud problem (sunglint/Sahel) solved since begin March

GIST, Boulder, 31/03/2004 In progress u Validation of unfiltered radiances u New LOS non-repeatability error correction: implemented and tested, not yet activated u Validation of Fluxes u Validation of Cloud cover and optical depth

GIST, Boulder, 31/03/2004 Future u Validation of Cloud phase u Reprocessing

GIST, Boulder, 31/03/2004 Conclusions u RGP produces GERB unfiltered radiances and fluxes in near real time. u SEVIRI used as auxiliary data for –Spectral unfiltering –Scene id for ADM selection –Resolution enhancement u Near nominal processing since 19/12/2003. u Validation: in progress.