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MODIS/Aqua Ocean Reprocessing

MODIS/Aqua Ocean Reprocessing. Bryan Franz Ocean Biology Processing Group MODIS Science Team Meeting 22-24 March 2005. Introduction. MODIS/Aqua Ocean Reprocessing 1 completed March 2005. L1A-GEO-L1B-L2 completed less than 1 week (~150X) Also completed SeaWiFS Reprocessing 5

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MODIS/Aqua Ocean Reprocessing

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  1. MODIS/Aqua Ocean Reprocessing Bryan Franz Ocean Biology Processing Group MODIS Science Team Meeting 22-24 March 2005

  2. Introduction • MODIS/Aqua Ocean Reprocessing 1 completed March 2005. • L1A-GEO-L1B-L2 completed less than 1 week (~150X) • Also completed SeaWiFS Reprocessing 5 • This presentation will cover • Remaining issues from initial OBPG processing • Changes implemented for this reprocessing • Analysis of results • Remaining issues & work in progress • New products available for evaluation

  3. Issues Following Initial OBPG Processing of MODIS/AquaCompleted May 2004

  4. Issues from Initial ProcessingCompleted May 2004 • Inconsistency in the annual cycle of global water-leaving radiances SeaWiFS R4.1 MODIS/Aqua Deep-Water - mean of all common bins deeper than 1000 meters

  5. Issues from Initial Processing • Long-term (3% per year) and seasonal (+/- 10%) deviations relative to SeaWiFS R4.1 global trends Global Deep-Water nLw Ratio +50% ~ 3% change/year +10% -10% -50%

  6. Issues from Initial Processing • Differences relative to SeaWiFS R4.1 which increase with latitude or solar zenith angle 35 North nLw Ratios, Zonal Pacific, 150W-170W +20% 25 North -20% 15 North

  7. Issues from Initial Processing • Very large differences relative to SeaWiFS R4.1 in global mean aerosol optical thickness retrievals MODIS and SeaWiFS Deep-Water AOT Comparison 0.15 MODIS/Aqua SeaWiFS 0.10

  8. Issues from Initial Processing • Larger deviations in recent months due to out-dated MODIS instrument calibration look-up table (LUT) MODIS/SeaWiFS Deep-Water nLw Ratio Last SD Measurement for Operational LUT

  9. Reprocessing Changes

  10. Changes for 1st Aqua Reprocessing • Updated instrument calibration • MCST V5.0.1 equivalent, OBC measurements to Nov 2004. • Refit by OBPG as single exponential after removal of detector-dependent screen vignetting residuals. Before LUT Change After LUT and Other Changes

  11. Changes for 1st Aqua Reprocessing • Straylight Masking • Modeled point-spread function (PSF) indicates significant sensitivity to straylight from adjacent sources. • 7 x 5 masking around cloud and saturation pixels removes the most significant contamination, fixes AOT discrepancy. MODIS & SeaWiFS Deep-Water AOT Comparison MODIS Band 16 PSF Before SL Masking After SL Masking 0.15 0.10

  12. Changes for 1st Aqua Reprocessing • Changes to atmospheric correction • Updated relative spectral response (RSR) functions: new Rayleigh tables and band-averaged coefficients. • Revised Rayleigh pressure correction (M. Wang), to include solar zenith dependence (effect can be significant at high latitudes, for large deviations from standard pressure). Impact of Change on MODIS nLw Deep-Water nLw Ratio 40-50N Pacific nLw Ratio +1% -10%

  13. Deep-Water nLw Ratios +1% SeaWiFS 40-50N Pacific nLw Ratios +7% SeaWiFS Changes for 1st Aqua Reprocessing • Enhanced Fresnel correction for Lw normalization • include reflection/refraction to downwelling irradiance. Fresnel Correction, Atmosphere to Ocean Wind = 0 m/s Wind = 20 m/s M. Wang Model

  14. Changes for 1st Aqua Reprocessing • Morel f/Q correction for Lw normalization • accounting for non-isotropic sub-surface light field Before f/Q After f/Q +20% Deep Water nLw Ratio MODIS/SeaWiFS 0% -20% +50% Southern Pacific MODIS/SeaWiFS 0% -50%

  15. Changes for 1st Aqua Reprocessing • Morel f/Q correction for Lw normalization • accounting for non-isotropic sub-surface light field Residual Scan Dependence in MODIS nLw(443) Before f/Q After f/Q +2% +10% 0% -10% -4%

  16. Changes for 1st Aqua Reprocessing • MOBY data reprocessing, final vicarious calibration • largest effect in 412 and 551-nm bands Impact of MOBY Change on MODIS nLw Deep-Water Coastal +4% +2%

  17. Reprocessing Results • New LUT • Straylight rejection • RSR and pressure corrections • Fresnel • f/Q • New MOBY vicarious cal

  18. Reprocessing Results • New LUT • Straylight rejection • RSR and pressure corrections • Fresnel • f/Q • New MOBY vicarious cal Also applied in SeaWiFS Reprocessing 5

  19. Results from Reprocessing 1nLw Comparison with In situ Initial Processing Reprocessing 1

  20. Results from Reprocessing 1nLw Comparison with In situ SeaWiFS R5 MODIS/Aqua R1

  21. Results from Reprocessing 1Chlorophyll Comparison with In situ SeaWiFS R5 MODIS/Aqua R1

  22. Results for Reprocessing 1 Consistency in annual cycle is approaching SeaWiFS SeaWiFS R5 MODIS/Aqua R1

  23. Results from Reprocessing 1nLw Comparison to SeaWiFS R5 • Sensor agreement to within 7% for global mean deep-water nLw retrieval. Better for clear water. • Some bias & trend is still evident between instruments. Initial Processing Reprocessing 1 +10% 0% -10%

  24. Results from Reprocessing 1 nLw Ratio to SeaWiFS R5, Zonal Pacific, 150W-170W Initial Processing Reprocessing +/- 20% 35 North Laitude (Solar Zenith) +/- 10% 25 North +/- 5% 15 North

  25. Results from Reprocessing 1 Deep-water AOT and Chlorophyll Comparison to SeaWiFS Chlorophyll AOT (865) <Cmodis> = 0.174 mg m-3 <Cseawifs> = 0.171 mg m-3 Solid Line: MODIS/Aqua R1 Dashed Line: SeaWiFS R5

  26. Seasonal Chlorophyll Images MODIS/Aqua R1 SeaWiFS R5 Winter 2004 Winter 2004 Summer 2004 Summer 2004 • 0.01-64 mg m-3

  27. Remaining Issues & Work in Progress • Bias & trends in relative agreement with SeaWiFS • instrument calibration (SD fit, lunar vs solar, RVS change) • effect of aerosols on polarization (analysis in progress) • straylight correction (reduce masking losses) • apparent earth shine in dark counts • Residual cross-scan trends • Residual striping

  28. 60° Sensor Zenith 60° Sensor Zenith Residual Cross-scan Trends nLw(412) nLw(551) • Global mean residual RVS at +/- 3% in nLw • Already Level-3 masking at 60° sensor zenith +20% +10% -10% -20%

  29. Residual RVS & Striping in Red Bands nLw(667) nLw(678) • Fractionally large cross-scan artifacts in red, no explanation yet. +20% +10% 0% -10% -20%

  30. Residual Striping nLw(412) nLw(551) +10% • Global mean residual striping at +/- 2% in nLw • Consistent over life of mission (problem with SD cal?) +5% -5% -10%

  31. Progress on Striping Corrections MCST Lunar Analysis () • derived by averaging all Lunar calibrations on a per-detector basis OBPG TOA Analysis (,) • derived by collecting 20-pixel along-track runs (10 detectors x 2 mirror sides) in clear atmosphere/low polarization/low chlorophyll conditions, correcting for relative change due to atmosphere, and averaging per detector, per mirror-side. Red & NIR bands saturate on Moon

  32. Effect of OBPG Striping CorrectionnLw 412 nm Before Correction After Correction

  33. New Productsfor evaluation

  34. New or Revised Productsimplemented for evaluation • Carder IPAR & ARP • ipar -instantaneous photosynthetically available radiation • arp -instantaneous absorbed radiation by phytoplankton • Chlorophyll Fluorescence and Supporting Products • flh -fluorescence line height • cfe -chlorophyll fluorescence efficiency • Clark Empirical Algorithms • chl_clark -chlorophyll concentration • poc_clark -particulate organic carbon • tsm_clark -total suspended matter • Gordon & Balch Calcite • calcite_2b -calcite concentration, 2-band algorithm • calcite_3b -calcite concentration, 3-band algorithm

  35. New or Revised Productsimplemented for evaluation • IOP Models • gsm01 - Garver-Siegel-Maritorena Semi-Analytical • carder - Carder Semi-Analytical • qaa - Quasi-Analytical Algorithm * • IOP-based Products • Kd_lee - Z.P.Lee diffuse attenuation * * Coming Soon, Thanks to P. Martinolich at NRL Stennis

  36. In The Works • Daily-Average PAR (R. Frouin) • PAR - SeaWiFS PAR updated for MODIS

  37. Seasonal Chlorophyll Images MODIS/Aqua R1 SeaWiFS R5 Winter 2004 Winter 2004 Summer 2004 Summer 2004 • 0.01-64 mg m-3

  38. Extra Slides

  39. Residual RVS & Striping in Red Bands nLw(667) nLw(678) +20% +10% -10% -20% +10% +5% -5% -10%

  40. New or Revised Productsimplemented for evaluation • Garver-Siegel-Maritorena Semi-Analytical Bio-Optical Model • chl_gsm01- chlorophyll concentration • a_nnn_gsm01- total absorption • bb_nnn_gsm01- total backscatter • bbp_nnn_gsm01- particulate backscatter • aph_nnn_gsm01- absorption due to phytoplankton • adg_nnn_gsm01- absorption due to gelbstof and detrital material • Carder Semi-Analytical Bio-Optical Model • chl_carder- chlorophyll concentration • a_nnn_carder- total absorption • bb_nnn_carder- total backscatter • bbp_nnn_carder- particulate backscatter • aph_nnn_carder- absorption due to phytoplankton • adg_nnn_carder - absorption due to gelbstof and detrital material • flags_carder- product-specific flags nnn - sensor wavelength

  41. Coming Soon • Quasi-Analytic Algorithm (Z.P. Lee) • a_nnn_qaa- total absorption • bb_nnn_qaa- total backscatter • bbp_nnn_qaa- particulate backscatter • aph_nnn_qaa- absorption due to phytoplankton • adg_nnn_qaa- absorption due to gelbstof and detrital material • IOP-based Diffuse Attenuation (Z.P. Lee) • Kd_nnn_lee- diffuse attenuation at sensor wavelength nnn Thanks to P. Martinolich at NRL Stennis nnn - sensor wavelength

  42. On the Subject of Flags • Each derived product should include tests for: • poor or questionable quality, sets the Level-2 CHLWARN flag bit • algorithm failure, sets the Level-2 CHLFAIL flag bit • The failure and warning flags can be masked at Level-3. The binner masking is product independent, all products binned at the same time are masked the same. • Additional flags or supporting products can be associated with a derived product, for QC and evaluation purposes at Level-2. No impact to binning.

  43. Carder Model Product-Specific Flag Definitionflags_carder

  44. In situ Match-ups for MODIS/Aqua 55% of Radiance Match-ups

  45. nLw: MODIS/Aqua vs SeaWiFS Deep-Water Simulated Center-Wavelength Differences (after band-pass correction) 488 vs 490 Chlor-a 551 vs 555 Deep-Water Mean Relative to SeaWiFS, the 488 and 551 bands should be elevated at chlorophylls typical of deep water (~0.2 mg/m3).

  46. MODIS/AquaVariation of Geometry Along-TrackEastern Scan Edge Scattering Angle

  47. Variation of Rayleigh Radiance Along-Track Eastern Edge Nadir Western Edge Scattering Angle 0.05 mW/cm2 um sr or ~2% of nLw Rayleigh Radiance 412 nm

  48. Cross-Scan Variation of Sensor View ZenithMODIS/Aqua

  49. Coastal

  50. Deep

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