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Modifications to MODIS Aqua ocean color bands calibration for 2010 OBPG reprocessing

Modifications to MODIS Aqua ocean color bands calibration for 2010 OBPG reprocessing. Gerhard Meister a,b a: Futuretech Corp. b: OBPG (Ocean Biology Processing Group) 1/25/10 MODIS Science Team Meeting 2010, Washington, D.C. MODIS Calibration Workshop 2010, Greenbelt, MD. 1. 1.

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Modifications to MODIS Aqua ocean color bands calibration for 2010 OBPG reprocessing

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  1. Modifications to MODIS Aqua ocean color bands calibration for 2010 OBPG reprocessing Gerhard Meistera,b a: Futuretech Corp. b: OBPG (Ocean Biology Processing Group) 1/25/10 MODIS Science Team Meeting 2010, Washington, D.C. MODIS Calibration Workshop 2010, Greenbelt, MD 1 1

  2. Methodology: • Baseline: MCST lunar and SD trending (coll. 6) • New MCST lunar analysis: time dependent NIR RVS • MODIS Aqua crosscalibrated to SeaWiFS (as for Terra in Kwiatkowska et al., Applied Optics, 2008) • Approach: Use SeaWiFS L3 nLw, bring to TOA, adjust MODIS cal. and pol., for every month of the mission (4-day L3) • Verify with analysis using only MODIS Aqua data: temporal trends (seasonal cycle removed) and ratio of L2/L3 versus scan angle 2 2

  3. Temporal issues: 412nm and red bands 3 3

  4. RVS issues: 412nm, red bands 4 4

  5. New lunar trending of bands 13-16 (667-869nm) Comparison of collection 5 LUT to coll. 6: 5

  6. Temporal issue resolved: 678nm / FLH 6

  7. Reduced temporal variation for 488-547nm 7

  8. Increased trend in 412nm, angstrom improved: 8

  9. Crosscalibration approach: Lm = M11*Lt + m12*Q + m13*U Lm: measured TOA radiance (MODIS) Lt: true TOA radiance (from SeaWiFS) Q, U : linear Stokes vector components, modeled from Rayleigh and glint M11, m12, m13 : fitted instrument characterization parameters (depend on band, MS, detector, scan angle) 9

  10. Crosscalibration results: Polarization (temporal) - Larger seasonal cycle than in MODIS Terra - No trend in polarization coefficient m12 until 2008, not clear if trend afterwards Band 8: 412nm Black, blue, red:detectors 1,5,10, MS 1 View angle: nadir 10 10

  11. Crosscalibration results: Polarization (temporal) - Cycle in m12 decreases with wavelength - All bands stable over time Band 10: 488nm Band 13: 667nm 11 11

  12. Crosscalibration results: Polarization (temporal) - Variability in m13 similar as in Terra - All bands stable over time, prelaunch values used Band 8: 412nm Band 13: 667nm 12 12

  13. Crosscalibration results: Polarization (detectors) • Crosscalibration results confirm detector trend from prelaunch measurements (not used before) - Absolute offset at BOS (low TOA deg. of pol.) Band 8: 412nm Band 12: 547nm 13 13

  14. Crosscalibration results: Calibration (m1 and RVS) • Implementation for 2010 reprocessing: Temporal correction for 412-443nm, constant correction for 488-678nm 14 14

  15. RVS issues resolved: 412nm, 443nm 15 15

  16. RVS issues resolved: red bands (not EOM) 16 16

  17. Temporal issue resolved: 412nm 17

  18. Chlorophyll trends: similar to SeaWiFS 18

  19. Summary • Principal changes for MODIS Aqua calibration and characterization:- New temporal NIR scan angle dependence (MCST) - New temporal trends for 412-443nm (xcal)- New scan angle dependence for 488nm-678nm (xcal, no time dependence)- New detector dependence of polarization sensitivity (prelaunch) • Resulting improvements to ocean color products:- FLH stable over mission in olig.- Rrs 412nm stable over mission, variability reduced for remaining bands- Large scan dependence at EOM removed for 412nm- Minor scan angle dependence removed for 443-547nm- Large scan angle dependence reduced for 667-678nm, but still present at EOM 19

  20. Backup 20

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