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2 Remote sensing applications in Oceanography: How much we can see using ocean color? Adapted from lectures by: Martin A Montes Rutgers University Institute of Marine and Coastal Sciences

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3 Main topics Introduction: definitions, sensor characteristics Model development: IOPs, AOPs, Forward and Inversion approach Applications: chl, phytoplankton size structure

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4 Ocean color sensors Definition: Types: Passive vs Active Sensor characteristics: swath, footprint, revisiting time, spectral resolution

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5 Ocean color sensors: characteristics First sensors: B&W Temporal resolution: revisiting time? Spectral resolution: number of channels?, bandwidth?

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Differences between measuring SST and ocean color: Infrared radiometers (like AVHRR) measure radiation emitted from the ocean surface Assumes ocean is like a black-body emitter with T B related to actual temperature Measures skin temperature only Ocean color sensors do not measure emission they measure reflectance How do we know were measuring reflectance, not emission?

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Emission by the Earth in the visible is zero. Reflectance of the ocean in the thermal infrared is almost zero Reflectance of the ocean is not only a skin phenomenon. Its signal is more complex because the optical depth is much greater and depends on wavelength.

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Ocean color sensors: characteristics http://www.ioccg.org/reports_ioccg.html

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Ocean color sensors: characteristics

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10 Ocean color sensors: characteristics

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Hyperion hyperspectral sensor on EO-1 220 channels

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12 Inherent and Apparent Optical properties IOPs: not influenced by the light field (e.g., absorption coefficients) AOPs: influenced by the light field (e.g., reflectance, backscattering)

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13 IOPS & biogeochemical parameters AbsorptionBackscattering PhytoplanktonCDOMPOCSPM VSF??

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14 Forward vs. Inversion models Forward: IOPs R rs (Hydrolight or non-commercial code) Given what we know is in the water, what do we expect it to look like? Inversion: R rs (Empirical, analytical, statistical) Given what we see, what can we tell about what is in the water? IOPs

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Rrs(412)/Rrs(555) band ratio yields a reasonably consistent relationship with in situ observations of CDOM absorption across several regions in the Mid-Atlantic continental shelf Can also derive empirical relationship between backscatter and particulate matter in the water. This allows estimation, by satelite, or Particulate Organic Carbon (POC) in the ocean.

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CZCS image of the Gulf Stream obtained on April 1, 1982, showing a prominent warm-core ring. http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/classic_scenes

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24 MODIS Sea Surface Temperature, 2000 December 6, 17:05 and MODIS Surface Chlorophyll Concentration

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25 Phytoplankton Bloom in the Arabian Sea