1 / 41

ENVISAT first quality assessment Calibration and cross-calibration. F-PAC activities

ENVISAT first quality assessment Calibration and cross-calibration. F-PAC activities Joël DORANDEU , Yannice FAUGERE , Françoise MERTZ - CLS , France. OUTLINE: Calibration / Validation, performance assessment Cross-calibration wrt ERS-2 and Jason-1.

lucine
Download Presentation

ENVISAT first quality assessment Calibration and cross-calibration. F-PAC activities

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ENVISAT first quality assessment Calibration and cross-calibration. F-PAC activities Joël DORANDEU, Yannice FAUGERE, Françoise MERTZ- CLS, France OUTLINE: Calibration / Validation, performance assessment Cross-calibration wrt ERS-2 and Jason-1

  2. Calibration and cross-calibration. F-PAC activities • Objectives: • Quality assessment of ENVISAT data • Long-term monitoring of altimeter/radiometer parameters and geophysical corrections • Algorithm assessment and improvement • Cross-calibration with other altimeters/radiometers • Activation: • routinely in an operational context • particular investigations • long term monitoring • Tools : CMA/Verification tools and other CalVal tools • Connexions: • with ground segment teams • with other studies: SSB, MWR, in-situ measurements Quality assessment report: Associated to data dissemination

  3. Calibration and cross-calibration. F-PAC activities • ENVISAT data. Verification strategy: • to estimate the product data quality (GDR). • to assess/propose improvements. Product update: • Ice flag • Bent model ionosphere correction • GIM ionosphere correction • Along-track filtering of dual-frequency iono. • Correction of Sigma0 atmospheric attenuation • Radiometer correction (+1 dB Sigma0) • SSB estimation • CLS01 MSS model

  4. ENVISAT Calibration / Validation Joël DORANDEU, Yannice FAUGERE, Françoise MERTZ- CLS, France Data processing Altimeter parameter Radiometer parameter Envisat performances

  5. Available data - 3 cycles of GDR (10, 11, a part of 12) - Global coverage of 75% on cycle 10 and 11 - Missing measurements on cycle 11:

  6. S BandAnomal Mean /pass of Range Ku – Range S (m) (cycle 12)

  7. Main editing parameters Radiometer Land flag Ice flag -10 m < SSH – MSS < 10 m Number of 18 Hz measurements > 10 RMS of 18 Hz measurements < 20 cm -0.20 deg2 < Off-nadir angle < 0.16 deg2 0 < Ku SWH < 11 m 7 < Ku Sigma0 < 30 dB Other selections on geophysical corrections Selection of valid periods for S-band estimations

  8. Data selection

  9. Data selection

  10. Altimeter parameters RMS of elementary measurements RMS of Ku-Band Range (cm) RMS of S-Band Range (cm)

  11. Altimeter parameters RMS of elementary measurements RMS of S Range / RMS of Ku Range RMS of Ku Range / SWH

  12. Altimeter parameters Off-nadir angle (from waveforms) Mean /pass of Off-nadir angle (deg2) (cycle 10, 11, 12)

  13. Altimeter parameters Significant Wave Height SWH Ku SWH S

  14. Altimeter parameters Backscatter coefficient Sigm0 Ku Sigm0 S

  15. Altimeter parameters Ionosphere corrections Dual iono / bent iono Dual iono / GIM iono

  16. Altimeter parameters Ionosphere corrections (Cycle 11)

  17. Radiometer parameters Wet troposphere correction Radiometer / ECMWF Radiometer recomputed / ECMWF

  18. ENVISAT performance assessment Crossover analysis Regression coefficients at crossovers: Pseudo Time Tag Bias (ms):

  19. ENVISAT performance assessment Crossover analysis - Standard deviation (cm)

  20. ENVISAT performance assessment – crossover analysis Impact of Ionosphere corrections - Standard deviation (cm)

  21. ENVISAT performance assessment ENVISAT SLA relative to MSS* with different SSB (using Bent) * GSFC CLS01 ENVISAT SLA relative to MSS* with different iono (using BM4) ENVISAT SLA relative to MSS* with computed wet tropo using BM4 and GIM

  22. ENVISAT performance assessment Preliminary high frequency signal estimations Spectral analyses ENVISAT ERS-2

  23. ENVISAT performance assessment Preliminary high frequency signal estimations High pass filtering method Std. dev. of HF[SSH-MSS]3pts (cm) SWH (m) 6 0 5 0.5

  24. conclusions Good general performances of ENVISAT data parameter analysis crossover variance (8 cm) SLA Algorithms and corrections: need to be tuned Sea State Bias Ionosphere correction MWR correction ENVISAT bias: SSH ~ 1.26 m / MSS

  25. Cross-calibration activities brief overview Objectives: Long-term monitoring of altimeter/radiometer parameters and geophysical corrections Cross-calibration with other altimeters/radiometers ENVISAT IGDR/GDR assessment reports will include cross-calibration results This study: - ENVISAT (cycles 10 and 11) GDR ERS-2 OPR2 (from CERSAT) cycles 78 and 79 Jason 1 GDR cycles 25-36 SPTR+USO corrections Homogeneous corrections Sigma0 correction (since 01/2000) TBs drift correction (02/2003) => Wet tropo Homogeneous corrections Results presented from cycle 11 Envisat

  26. Altimeter parameters Significant Wave Height – Cross-calibration : ERS-2 Mean : 21.2 cm Standard deviation : 27 cm Slope = 0.028

  27. Altimeter parameters Significant Wave Height – Cross-calibration : ERS-2 Envisat ERS-2

  28. Altimeter parameters Significant Wave Height – Cross-calibration : Jason-1 mean 13 cm std 26 cm

  29. Altimeter parameters Significant Wave Height – Cross-calibration : Jason-1 10 days Envisat |latitude|<66° Cycle 31 Jason 1

  30. Altimeter parameters Ku-band Backscatter coefficient – Cross-calibration : ERS-2 Mean : 0.06 dB Standard deviation : 0.27 dB Slope = 0.019

  31. Altimeter parameters Ku-band Backscatter coefficient – Cross-calibration : ERS-2 ERS-2 Envisat

  32. Altimeter parameters Ku-band Backscatter coefficient – Cross-calibration : ERS-2

  33. Altimeter parameters Ku-band Backscatter coefficient – Cross-calibration : Jason 1 10 days Envisat |latitude|<66° Mean 0.61 dB Std 0.74 dB Cycle 31 Jason 1

  34. Altimeter parameters Dual Frequency ionosphere correction – Cross-calibration : Jason 1 Mean 1.5 cm Std 2 cm

  35. Radiometer parameters Cross-calibration : ERS-2 Mean 4.8 mm

  36. Radiometer parameters Cross-calibration : Jason 1 Computed Product Mean 9 mm Std 1.5 cm Mean 1.7 cm Std 1.6 cm

  37. ENVISAT performance assessment ENVISAT- ERS-2 cross-calibration (repeat-track analysis)

  38. Envisat performance assessment Envisat Jason-1 crossover SSH differences DT < 10 days / open ocean 65000 points

  39. Envisat performance assessment Envisat Jason-1 crossover SSH differences DT < 10 days / open ocean

  40. Envisat performance assessment SLA Envisat / Jason-1

  41. Cross-calibration conclusions ENVISAT bias: /ERS-2 /Jason SWH ~ 20 cm 13 cm Sigma0 ~ 0.06 dB 0.6 dB SSH ~ 1.12 m 1.05 m Wet tropo ~ 4.8 mm 1 cm SSB Dual-Frequency ionosphere Wet troposphere neural computation

More Related