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Validating the GSM01 algorithm for chlorophyll products in the Chesapeake Bay

Validating the GSM01 algorithm for chlorophyll products in the Chesapeake Bay. Mimi Szeto Research & Discover, GSFC Summer Intern 2007 Advisor: Jeremy Werdell, 614.2. the satellite views the spectral light field at the top-of-the-atmosphere. SATELLITE. TOP-OF-THE-ATMOSPHERE.

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Validating the GSM01 algorithm for chlorophyll products in the Chesapeake Bay

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  1. Validating the GSM01 algorithm for chlorophyll products in the Chesapeake Bay Mimi Szeto Research & Discover, GSFC Summer Intern 2007 Advisor: Jeremy Werdell, 614.2

  2. the satellite views the spectral light field at the top-of-the-atmosphere SATELLITE TOP-OF-THE-ATMOSPHERE 1. remove atmosphere from total signal to get light from sea surface (water-leaving radiance, Lw) 3. spatially / temporally bin and remap satellite Ca observations SEA SURFACE 2. relate spectral Lw to Ca (or geophysical product of interest) PHYTOPLANKTON Background: Remote Sensing

  3. Background: Why Chlorophyll? Photosynthesis in Chlorophyll Global Carbon Cycle Legal Action for Regulating Bay Health

  4. Background: How it works. Light Scattered Remote Sensing Equation Absorbed fcn Remote sensing reflectance, Derived from water leaving radiances Inherent Optical Properties

  5. Background: How it works. Inherent Optical Properties Remote Sensing Equation ABSORPTION fcn water plankton CDOM and non-algal particles SCATTERING water particles Inherent Optical Property = [magnitude] x (spectral shape) 2.5 1.0 0.008 2.0 0.8 0.006 S a*(l) 0.6 1.5 0.004 0.4 Absorption 1.0 0.002 0.2 0.5 0.0 0.000 0.0 600 400 500 600 700 400 500 700 400 500 600 700 Wavelengths Wavelengths Wavelengths

  6. Background: How it works. SeaWiFS Wavelengths  412 443  490  510 555   670  Chlorophyll concentration Model Parameters

  7. Background: In situ vs Satellite SATELLITE IN SITU nLw: Radiometer Chlorophyll: HPLC, fluorometer GSM01 nLw Chlorophyll • NOMAD • in situ data set (N: 2208, 281 in the Chesapeake Bay) • Chl Concentration, Rrs at SeaWiFS wavelengths • Modeled products vs In situ products

  8. GSM01

  9. Validation and Testing • Consolidate data from 3000 stations. • Statistically derive new model parameters ABSORPTION water plankton CDOM and non-algal particles SCATTERING water particles a*(l)& S Combo 1 Combo 2 Combo 3… GSM01 Modeled Chl 1 Modeled Chl 2 Modeled Chl 3 … NOMAD Rrs

  10. Results: Model Parameter GSM01CB a*(l) New Parameter a*(l)

  11. Results: Chlorophyll Modeled/Insitu Ratio (ACCURACY) (SPREAD)

  12. Validation and Testing • Extra tests • Sensitivity Analysis • Drop 412 • atmospheric problem • Drop 670 • often not reliable • Matrix Inversion • Backscattering Parameter GSM01 Negative Modeled Chlorophyll RESULTS

  13. Ten-Year Analyses • Distributions of % Frequency for 10 years of Chl data • GSM01NP - ineffective in Summer • High values • Better in Fall % Frequency Chl RED = IN SITU CHL BLACK = MODEL CHL % Frequency % Frequency Chl Chl

  14. Regional Blending BLENDING ALGORITHMS GSM01 GSM01NP SWITCH AT -75.7 W

  15. Conclusion • Validation was successful. • The new parameters help improve chlorophyll retrievals. • I created a method for sensitivity analysis. • Use all six wavelengths with the new parameters. • Blending algorithms can be used to avoid abrupt transitions in chlorophyll images

  16. Acknowledgements • Jeremy, Sean, Gene, Brian, and the rest of the Ocean Biological Processing Group at NASA • Research and Discover, UNH • Fellow interns

  17. Ten-Year Analyses Ten Year Time Series Comparison of Modeled Chlorophyll vs Insitu Chlorophyll

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