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Ocean Color Reprocessing

Ocean Color Reprocessing. Bryan Franz Ocean Biology Processing Group NASA Goddard Space Flight Center. Contents. reprocessing overview known issues proposed changes preliminary results international collaborations. Overview. Scope: sensors: MODISA, MODIST, SeaWiFS, OCTS, CZCS

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Ocean Color Reprocessing

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  1. Ocean Color Reprocessing Bryan Franz Ocean Biology Processing Group NASA Goddard Space Flight Center

  2. Contents • reprocessing overview • known issues • proposed changes • preliminary results • international collaborations

  3. Overview Scope: • sensors: MODISA, MODIST, SeaWiFS, OCTS, CZCS • suites: OC, PAR, CLCT, FLH, POC, ZEU, IOP Highlights: • sensor calibration updates (instrument aging, new insights) • vicarious calibration updates (new MOBY data) • new aerosol models based on AERONET • NO2 corrections • change MODIS nominal band center • traceability & reproducibility of all inputs

  4. We're not doing bad "as is" SeaWiFS MODISA "first, do no harm" --Hippocrates

  5. Known Issues MODIS and SeaWiFS Oligotrophic Chlorophyll 0.01 - 0.02 mg m-3

  6. Known Issues MODIS and SeaWiFS Deep-Water Lwn Ratios 551 vs 555 667 vs 670

  7. Known Issues MODIS Fluorescence Line Height Global Deep-Water Anomaly Trend Mean FLH = 0.005 20% FLH 2004 2007 2007 2006 Mission Time

  8. Changes

  9. Aerosol Models • based on AERONET size distributions & albedos • 70 models (7 humidities x 10 size fractions) • model selection descriminated by relative humidity • vector RT code accounting for polarization • same code used for Rayleigh LUTs Current S&F Size Distributions AeroNET Size Distributions c50 c90

  10. Revised Band Center 551 547 Revised Out-of-Band Corrections

  11. SeaWiFS Orbit • orbit has drifted to a 1:30 p.m. node crossing • impact to: • attitude system (Sun sensors) • solar diffuser calibration • thermal environment • solar path geometry Node Crossing Time

  12. SeaWiFS Orbit Node Crossing Time

  13. SeaWiFS Temporal Calibration - Current Operational Model Lunar Observations

  14. SeaWiFS Temporal Calibration - Revised

  15. SeaWiFS Temporal Calibration Issue

  16. Uncertainty in SeaWiFS nLw Trends

  17. Uncertainty in SeaWiFS Chl Trends OC4 OC3

  18. Uncertainty in SeaWiFS Chl Trends Oligotrophic Eutrophic OC3 OC4 Mesotrophic variation in retrieved chl trend due to uncertainty in lunar-view to earth-view gain ratio at 765nm.

  19. Other Changes • MODISA calibrations • unknown temporal trend in Red-NIR RVS • recharacterize polarization sensitivity, 412 drift • NO2 corrections • Ahmad et al. (2007) Appl. Opt. • extensive effort to produce/qc filled gome-schiamachy-omi dataset • 0-10 % effects on Lwn, mostly coastal and high latitude • Updates to ancillary fields • best available ozone and met data, new dependency on RH • Reduction of SeaWiFS "straylight" speckling issues • outlier-resistant Level-3 binning strategies • Updated OCx chlorophyll & Kd algorithms based on NOMAD V2

  20. Results

  21. SeaWiFS Deep-Water In situ Match-up Stats Operational Processing Configuration Product Med Ratio APD N Slope Intercept R-Squared Lwn412 1.0149 12.4190 171 1.0526 -0.0259 0.8801 Lwn443 0.9453 16.1420 252 1.0219 -0.0908 0.8112 Lwn490 0.9222 13.2710 251 0.9125 0.0167 0.7196 Lwn510 0.9548 13.8035 142 0.9172 0.0302 0.4385 Lwn555 0.9590 16.4210 252 0.7742 0.0653 0.6453 Lwn670 1.6866 79.9820 248 1.2104 0.0121 0.4412 chlorophyll 0.9995 29.8490 466 0.8834 -0.1714 0.7892 aot865 1.4177 42.3055 60 1.4115 Current Baseline Reprocessing Configuration Product Med Ratio APD N Slope Intercept R-Squared Lwn412 1.0013 11.7425 160 1.0148 -0.0181 0.8886 Lwn443 0.9418 16.3365 238 1.0393 -0.1221 0.8198 Lwn490 0.9119 14.5100 237 0.9390 -0.0279 0.7206 Lwn510 0.9767 13.4330 133 0.9508 0.0005 0.4568 Lwn555 0.9450 18.0115 238 0.7707 0.0637 0.6413 Lwn670 1.5503 75.4955 234 1.2204 0.0113 0.4547 chlorophyll 0.9944 26.4870 423 0.8749 -0.2078 0.7931 aot865 1.0631 25.1590 57 1.0583 -0.0028 0.7360

  22. Improved Aerosol Retrievals Improved AOT and Angstrom Comparisons before after after before Chlorophyll Unchanged SeaWiFS Lower Cheseapeake Bay Time-Series

  23. Improved Aerosol Retrievals Even Better Using Regional Aerosol Models before after after before Chlorophyll Unchanged SeaWiFS Lower Cheseapeake Bay Time-Series

  24. more work TBD on MODISA calibration Improved Agreement Between Sensors Mean Deep-Water Lw Ratio Trends

  25. Eutrophic SeaWiFS Red-Band Issue MODISA SeaWiFS

  26. Improved Agreement Between Sensors Before After Mean Diff = 0.013 mg m-3 Mean Diff = 0.006 mg m-3 Mission Time Mission Time Mean Oligotrophic Chlorophyll Trends

  27. Other Missions • MODIST • see Franz et al. (2008) J. Appl. Rem. Sens. • see Kwiatkowska et al. (2008) Appl. Opt. • make changes consistent with MODISA • regenerate vicarious instrument characterization • CZCS • update vicarious calibration (model-based) • reprocess with latest tables, algorithms, flags & masks • OCTS • update vicarious calibration (model-based) • reprocess with latest tables, algorithms, flags & masks

  28. Summary • it’s a big job! • SeaWiFS (11+ years), MODISA (6+ years), MODIST (9+ years) • instruments aging, orbits changing • first complete end-to-end re-evaluation and update of ocean color processing methodology, radiative transfer tables, sensor cal, ancillary sources, file formats, etc. • good progress and demonstrated improvements to date. • more details and full analyses will be posted online for community comment and feedback. • start reprocessing of SeaWiFS and MODISA within few months, then MODIST, SST, legacy missions, PAR, IOPs, etc.

  29. International Collaborationskeeping the time-series alive

  30. ESA-NASA Collaborations on MERIS • G. Meister & B. Franz members of MERIS Quality Working Group • providing review and analysis for MERIS reprocessing • sharing ideas and gaining insight • CoastColor • OBPG applied to be a "champion user" for MERIS full resolution data • access to archive of 300-meter Chesapeake Bay scenes • awaiting ESA decision • SeaDAS • MERIS display support added • MERIS processing capability developed

  31. MERIS Processed with NASA Algorithms OC4 Chlorophyll RGB

  32. ISRO-NASA Collaborations on OCM • OCM-2 is global 1-km, 8-band tilting CCD with lunar calibration • Implementing arrangements in development for OCM-2 • ISRO-NASA & ISRO-NOAA • ISRO to provide online access to global OCM-2 data (4km) at Level-1B for research use, to all international users, at no cost. • NASA to provide processing capability (Level-1B through Level-3) for use by ISRO and the international community (SeaDAS). • preliminary capability based on OCM-1 already implemented • need ISRO to finalize Level-1B format • NASA & NOAA to participate in Joint Cal/Val Team

  33. Thank You

  34. Aerosol Models Rvf :Geometric mean radius (fine mode) σf : Geometric standard dev. (fine mode) Cvf: Max value of the fine mode dist. Rcf :Geometric mean radius (coarse mode) σc : Geometric standard dev. (coarse mode) Ccf: Max value of the coarse mode dist. fvf = Cvf/(Cvf+Cvc): Fraction of fine mode fvc = 1-fvf :Fraction of coarse mode Cvf Cvc σf σc Rvf Rvc

  35. Aerosol Models Standard Deviation Modal Radius SERC Wallop Island <0.762> COVE <0.666> <0.425> <0.096> Fine Mode Fraction Effective Radius <0.267>

  36. Aerosol Models Coarse Mode Fine Mode

  37. Spectral Out-of-Band Corrections

  38. SeaWiFS Temporal Calibration

  39. Comparison with Morel (Ca=0.065) MODISA: Theoretical nLw(547) = 0.319248 Observed nLw(547) = 0.320000 Theoretical nLw(667) = 0.0173954 Observed nLw(667) = 0.0230000 SeaWiFS: Theoretical nLw(555) = 0.269945 Observed nLw(555) = 0.305000 Theoretical nLw(670) = 0.0167871 Observed nLw(670) = 0.0400000

  40. Uncertainty in SeaWiFS Chl Trends Comparison Ratio Oligotrophic OC3 Eutrophic OC4

  41. Chl Chl Chl Effect of a Known Unknown Gain 3 Option 1 Gain 3 Option 3 Gain 3 Option 2 Lwn(555) Lwn(555) Lwn(555)

  42. Uncertainty in SeaWiFS Lwn Trends Oligotrophic Eutrophic Mesotrophic variation in retrieved nLw trend due to uncertainty in lunar-view to earth-view gain ratio at 765nm.

  43. Known Issues: SeaWiFS Late-Mission SeaWiFS Lw(510) Anomaly

  44. Removed Late-Mission Drift in SeaWiFS Before

  45. Known Issues: MODISA Lw(412) Trend

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