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Titre. IIR / CALIPSO : Validation of Level 1b data N.A. Scott, R. Armante , O. Chomette, V. Capelle, B. Sebag, Chédin ARA/LMD/IPSL(*) Ecole Polytechnique, Palaiseau. Acknowledgements : IPSL : Jacques Pelon, Anne Garnier

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  1. Titre • IIR / CALIPSO : • Validation of Level 1b data • N.A. Scott, • R. Armante, O. Chomette, • V. Capelle, B. Sebag, • Chédin • ARA/LMD/IPSL(*) • Ecole Polytechnique, Palaiseau Acknowledgements : IPSL : Jacques Pelon, Anne Garnier ICARE : Bruno Six, Jean-Marc Nicolas, Jacques Descloîtres et coll. CNES : Thierry Tremas et coll. (*) Contacts: scott@lmd.polytechnique.fr

  2. Introduction Two complementary approaches AMMA IIR in synergy with other imagers  Comparison of observed IIR radiances with radiances observed from other imagers IIR in "stand alone “(*) • Comparison of IIR observed brightness temperatures To simulated brightness temperatures based on forward models + in-situ (R/S) observations (or analyses) (*) Heritage of the LMD approach to TOVS, ATOVS, AIRS, AMSU’s, IASI quality control and validation of level1B data.

  3. Presentation • Validation approach 1 : IIR in synergy with other imagers •  methodology •  first results obtained at LMD • Validation approach 2 : IIR in "stand alone“ •  methodology •  heritage from AIRS/AMSU •  application to IIR • Implementation of the whole process on Icare for operational processing: first results • Perspectives

  4. IIR in synergy with other instruments  Comparison of observed IIR radiances with radiances observed from other imagers Approach : • Selection of companion instruments (imagers) and companion channels • Spatial + temporal colocation of the various instruments • Computation, statistical analysis (bias, stdv, fits) of differences between IIR channels and other instruments/channels observations: • for global or zonal area(s) • for land or sea • for various TBs ranges • for various viewing angles

  5. Selection of companion instruments and channels Required Criteria - Companion Instruments : Relevant number of spatio-temporal colocations • Companion Channels: « same » characteristics of absorption/emission • Modis/Aqua and Seviri/MSG

  6. Definition of thresholds : Quantification of inter-channels and inter-instruments radiance differences. TIGR dataset 2311 atmospheres (5 air masses) Spectral Response Functions IIR, MODIS, SEVIRI Forward radiative transfer model 4A/OP* TB’s IIR, Modis, Seviri DTBs(IIR-MODIS, IIR-Seviri, Seviri-Modis, IIR-IIR) Statistics on inter-channels and inter-instruments DTBs to get THRESHOLDS : F ( AIR MASS , VIEWING ANGLE, TBs ranges, …) *LMD/Noveltis

  7. Statistics (bias, stdv) on inter-channels differences IIR-MODIS and IIR-SEVIRI as a function of air mass IIR - MODIS IIR - SEVIRI Nadir σ BIAS

  8. Statistics (bias) on inter-channels differences IIR-MODIS , IIR-SEVIRI and Modis-Sevirias a function of viewing angle Mean differences for tropical atmosphere Viewing angle

  9. Spatial and temporal colocation of Modis and Seviri on an IIR grid: the “REMAP” algorithm (*) IIRswath 69 km spatial resolution = 1 km CALIPSO A-TRAIN (polar orbiters) Aqua MODISswath 2000 km spatial resolution = 1 km MSG geostationary SEVIRIspatial resolution 3 km @ sub-satellite point. scan the earth disc at a 15 minute rate colocation accepted if : spatial+temporal window within 1.5km + 7minutes 30 homogeneous surfaces for colocated pixels (all over sea or all over land) Seviri viewing angles < 50° colocation rejected if : TBs differences not within the thresholds values Heterogeneous land surface emissivities clear vs cloud pixels (*)from ICARE Specifications and Validation at LMD.

  10. !Emissivity!  Inhomogeneities land/sea land/land IIR - seviri Due to the high variability of the land surface emissivity with wavelength, Due to differences in the central position and shape of the SRFs, colocations over land are to be cautiously considered Colocated pixels are de-selected if not 100% sea

  11. Les 1er résultats (Approche I) !Clouds! Inhomogeneities : clear pixel vs cloud pixel (due to cloud texture, due to slightly different observation time, …) Annapolis area, Md, USA, Aug. 2006 DTb IIR-MODIS channels 1, 2 et 3 Elimination Abs(IIR – MODIS) >3σ (σ=0.7 K)

  12. Very First results: Detection of a calibration problem First data set: 19/06/2006  04/07/2006 - Important systematic differences • Obviousproblem on • IIR channels 1 and 2 -  problem submitted to CNES - Calibration and Geolocation problems identified and corrected. • Complete reprocessing by CNES • Starting on 17/08/2006

  13. First Results: 1 month IIR vs MODIS (17 Aug. 2006  16/09/2006) Nb colocations Bias Linear fit (in blue) Tb=a(time) + b No data Global, TBs range 200-330K, viewing angle 0-50°, DAY, SEA

  14. Les 1er résultats (Approche I) obtenus au LMD First Results: IIR vs MODIS, IIR vs Seviri, MODIS vs Seviri1 month data (17/08/2006  16/09/2006) Longitude zone TBs range Latitude zone sea

  15. IIR in stand alone  Comparison of IIR observed brightness temperatures to simulated brightness temperatures with forward model + in-situ (R/S) observations (or analyses) AMMA • « Héritage » from LMD: low and high spectral resolution vertical sounders and imagers (IR and MWV) • TOVS (1979 à 1995, 100 Mo/jour) on NOAA platforms • AIRS/AMSU-A(04/2003  03/2007, 900 Mo/jour) on AQUA platform • - in progress : IASI ; HIRS4 ; AMSUa ; MHS on Metop platform Required « tools »: ECMWF « ERA/40 » Radiosoundings or ECMWF « ERA/40 » Analyses 4A/OP* (forward radiative transfer model) REMAP * * (colocation algorithm) Clear/cloud algorithm Statistical algorithms • : *4A/OP : LMD/Noveltis • * * REMAP : ICARE

  16. IIR in stand alone mode +Modis + Seviri in stand alone Acquisition of analyses and/or radiosoundings from ECMWF Radiosoundings (or analyses): Quality control Colocation with IIR, Modis, Seviri pixels Interface with 4A/OP Clear/cloudyAlgorithm from Calipso ancillary data Lidar+IIR Forward model 4A/OP Statistical Analyses of Simulated vs Observed Long Time Series of IIR « Simulated vs observed » statistics By-products: same for the Modis and Seviri companion channels

  17. The level1b validation suite at LMD : colocation of hyperspectral AIRS or IASI observations withradiosoundings or re-analyses ERA40 Satellite data :14 orbits / day 900 Mo / day AIRS+AMSU/AQUA April 2003- June 2007 324 channels IR, 15 channels MWV Radiosoundings «ERA40 » (23 Go from 1979 to 2007) / Re-analyses ERA-40 (79 Mo / day 2 days / month) Era40 Raob colocation Adjustable Time/Space window ~ 3h/100km Quality control + Inter/extrapolation of thermodynamic profiles To interface the 4A model Colocated Database (250 Mo) Satellite Data Level 1b (5 Mo/month  Raob 17 Mo/day  Analyse)

  18. LMD/ARA Raobs Quality control check and inter/extrapolation Number of temperature levels check > 20 Number of h2o levels check > 15 yes Keep if : Ln(dp) < 0.15 (1050-800 mb) Ln(dp) < 0.30 (800-200 mb) Ln(dp) < 0.40 (200-35 mb) Ln(dp) < 0.60 (35-1 mb) Ln(dp) < 0.90 (1-0.01 mb) Log(pressure) difference between 2 consecutive pressure levels check yes Interfacingthe4A/OP model: Inter/extrapolation temperature profile Inter/extrapolation H2O profile (from Atmos profiles) Add or inter/extrapolate ozone profile (from Ugamp climatology) Top temperature pressure level check (for extrapolation  0.05mb) < 30 mb Top h2o pressure level Check (for extrapolation 0.05 mb) < 350 mb yes LMD/ARA Raobs Archive Surface pressure over Land > 920 mb Surface pressure Over sea > 950 mb yes

  19. Example of outputs: « simul-obs » AIRS et AMSU-A on the Aqua platform from a 4-year simulation based on LMD forward models (4A/OP and STRANSAC) and ECMWF Era40 radiosoundings For Infrared and Mirowave: Standard Deviation : 0.3 to 0.5 K Drift : 0.1 to 0.2 K during 3 years, more important in 2006 AIRS – Channel 76 AMSU - 6 AMSU - 8

  20. Results 1st results of the operational calibration of IIR at ICARE GLOBAL ZONE (sea only) – 01/02/2007 – 30/04/2007 IIR-Modis1 (K) IIR-Sev1 (K) Modis-Sev1 (K) IIR1-IIR2 (K)

  21. Typical Output : ONE DAY Statistics (14/03/2007 - 15 orbits) Diff. TB range angle mean σ # colocations IIR-Modis1 : 200.0 330.0 0.0 50.0 -0.08 0.67 10242366 IIR-Sev1 : 200.0 330.0 0.0 50.0 0.24 0.95 1207096 Modis-Sev1 : 200.0 330.0 0.0 50.0 0.33 1.01 1333895 IIR1-IIR2 : 200.0 330.0 0.0 50.0 -1.47 0.77 11731254

  22. 1st results of the operational calibration of IIR at ICARE From 01/02/2007 to 30/04/2007 –90 S : 90 N -180W : +180 E 200-330 K, 0-50 viewing angles IIR - Modis IIR - Seviri Modis - Seviri

  23. 01/02/2007  30/04/2007 IIR-modis 1st results of the operational calibration of IIR at ICARE -90S, 90N, -180W, 180E, angle between 10-20 ° 280-300 K 200-330 K 220-240 K

  24. Short Term Perspectives • … for an IIR operational long term analysis • Implementation of the whole process (IIR in synergy and IIR in stand alone) at Icare for an operational processing expected within the coming 2 months. • Archive and Distribution of the validation results to Calipso PIs, IPSL and CNES users.

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