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Green/Blue => Chl-a concentrations (derived for simple water cases: water+phytoplankton). Watercolors in the coastal zone. Ocean color from satellite: Global ocean production Radiant heating processes Define biotic provinces Shelf break frontal processes.
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Green/Blue => Chl-a concentrations (derived for simple water cases: water+phytoplankton) Watercolors in the coastal zone • Ocean color from satellite: • Global ocean production • Radiant heating processes • Define biotic provinces • Shelf break frontal processes • Measured reflectance => algorithm => sw constituents
Watercolors in the coastal zone • SW is more complex (more constituents affect reflectance): • HNLC region (suspended iron dust) • Coastal regions (CDOM, High scattering particles, Photons reflected from the bottom) Moreover large fronts => sharp horizontal gradients (need for high resolution in situ measurements)
Watercolors in the coastal zone • Reflectance: • Measure the ocean color • 95% of the signal is due to the atmosphere • Can be expressed as function of bb(λ) and a(λ) => it integrates the effects of all the substances in the water • bb(λ) is small, while a(λ) => R(λ) is small (challenge for the instruments) • Satellites: 5 bands or hyperspectral (better to invert R to water constituents)
Watercolors in the coastal zone • What determines Ocean color: • CDOM: • Organic matter smaller than 0.2 μm • High a(λ) => decrease in R(λ) • Can be estimated from Green/Red • Age from a(λ) curve: small slope => fresh CDOM • (used to characterize water masses)
Watercolors in the coastal zone • What determines Ocean color: • Phytoplankton: • Major absorbing constituent • Pigments varies with species (hyperspectral optics to distinguish different species) • Affect scattering (but low bb(λ)): scattering varies depending on the dimensions => on the species
Watercolors in the coastal zone • What determines Ocean color: • Bacteria and suspended sediments: • High influence on backscattering • Detritus (non living organic matter): • a(λ) curve similar to CDOM but relatively understudied