MODIS/Aqua Ocean Reprocessing Bryan Franz Ocean Biology Processing Group MODIS Science Team Meeting March 2005

Introduction MODIS/Aqua Ocean Reprocessing 1 completed March –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

Issues Following Initial OBPG Processing of MODIS/Aqua Completed May 2004

Issues from Initial Processing Completed May Inconsistency in the annual cycle of global water- leaving radiances MODIS/AquaSeaWiFS R4.1 Deep-Water - mean of all common bins deeper than 1000 meters

Issues from Initial Processing 2Long-term (3% per year) and seasonal (+/- 10%) deviations relative to SeaWiFS R4.1 global trends Global Deep-Water nLw Ratio +50% -50% ~ 3% change/year +10% -10%

Issues from Initial Processing 3Differences relative to SeaWiFS R4.1 which increase with latitude or solar zenith angle 35 North 25 North 15 North nLw Ratios, Zonal Pacific, 150W-170W +20% -20%

Issues from Initial Processing 4Very large differences relative to SeaWiFS R4.1 in global mean aerosol optical thickness retrievals MODIS and SeaWiFS Deep-Water AOT Comparison MODIS /Aqua SeaWiFS

Issues from Initial Processing 5Larger deviations in recent months due to out-dated MODIS instrument calibration look-up table (LUT) Last SD Measurement for Operational LUT MODIS/SeaWiFS Deep-Water nLw Ratio

Reprocessing Changes

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

Changes for 1st Aqua Reprocessing 2Straylight 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. Before SL MaskingAfter SL Masking MODIS Band 16 PSF MODIS & SeaWiFS Deep-Water AOT Comparison

Changes for 1st Aqua Reprocessing 3Changes 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). Deep-Water nLw Ratio40-50N Pacific nLw Ratio Impact of Change on MODIS nLw +1% -10%

Changes for 1st Aqua Reprocessing 4Enhanced Fresnel correction for Lw normalization include reflection/refraction to downwelling irradiance. Fresnel Correction, Atmosphere to Ocean SeaWiFS Deep-Water nLw Ratios +1% 40-50N Pacific nLw Ratios SeaWiFS +7% Wind = 0 m/s Wind = 20 m/s M. Wang Model

Changes for 1st Aqua Reprocessing 5Morel f/Q correction for Lw normalization accounting for non-isotropic sub-surface light field Deep Water nLw Ratio MODIS/SeaWiFS After f/Q Southern Pacific MODIS/SeaWiFS Before f/Q +20% 0% -20% +50% 0% -50%

Changes for 1st Aqua Reprocessing 5Morel f/Q correction for Lw normalization accounting for non-isotropic sub-surface light field After f/Q Before f/Q Residual Scan Dependence in MODIS nLw(443) +2% -4% +10% 0% -10%

Changes for 1st Aqua Reprocessing 6MOBY data reprocessing, final vicarious calibration largest effect in 412 and 551-nm bands Deep-WaterCoastal Impact of MOBY Change on MODIS nLw +2% +4%

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

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

Initial ProcessingReprocessing 1 Results from Reprocessing 1 nLw Comparison with In situ

SeaWiFS R5MODIS/Aqua R1 Results from Reprocessing 1 nLw Comparison with In situ

SeaWiFS R5MODIS/Aqua R1 Results from Reprocessing 1 Chlorophyll Comparison with In situ

Results for Reprocessing 1 Consistency in annual cycle is approaching SeaWiFS MODIS/Aqua R1SeaWiFS R5

Results from Reprocessing 1 nLw 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 ProcessingReprocessing 1 +10% 0% -10%

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

Results from Reprocessing 1 Deep-water AOT and Chlorophyll Comparison to SeaWiFS AOT (865) Chlorophyll Solid Line: MODIS/Aqua R1 Dashed Line: SeaWiFS R5 = mg m -3 = mg m -3

Seasonal Chlorophyll Images mg m -3 Summer 2004 Winter 2004 SeaWiFS R5 MODIS/Aqua R1 Winter 2004 Summer 2004

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

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

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

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

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

Effect of OBPG Striping Correction nLw 412 nm Before Correction After Correction

New Products for evaluation

New or Revised Products implemented 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

New or Revised Products implemented 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

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

Seasonal Chlorophyll Images mg m -3 Summer 2004 Winter 2004 SeaWiFS R5 MODIS/Aqua R1 Winter 2004 Summer 2004

Extra Slides

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

New or Revised Products implemented 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

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 nnn - sensor wavelength Thanks to P. Martinolich at NRL Stennis

On the Subject of Flags Each derived product should include tests for: 1poor or questionable quality, sets the Level-2 CHLWARN flag bit 2algorithm 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.

Carder Model Product-Specific Flag Definition flags_carder

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

nLw: MODIS/Aqua vs SeaWiFS Deep-Water Chlor-a 551 vs vs 490 Simulated Center-Wavelength Differences (after band-pass correction) Deep-Water Mean Relative to SeaWiFS, the 488 and 551 bands should be elevated at chlorophylls typical of deep water (~0.2 mg/m 3 ).

MODIS/Aqua Variation of Geometry Along-Track Eastern Scan Edge Scattering Angle

Variation of Rayleigh Radiance Along-Track NadirEastern Edge Western Edge Scattering Angle Rayleigh Radiance 412 nm 0.05 mW/cm 2 um sr or ~2% of nLw

Cross-Scan Variation of Sensor View Zenith MODIS/Aqua

Coastal

Deep

Clear