2 Remote sensing applications in Oceanography: How much we can see using ocean color? Adapted from...
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Transcript of 2 Remote sensing applications in Oceanography: How much we can see using ocean color? Adapted from...
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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