THE NEAR-SURFACE LAYER OF THE OCEAN
scattering control the manner in which impinging photons propagate through
a natural water body and substantially determine the color of the ocean). The
process of absorption is simply the removal of photons from the light field,
while scattering changes the direction of photon propagation. Scattering of
photons can occur in both an elastic and inelastic manner. Elastic scattering
does not change the photon wavelength, while inelastic scattering does.
Fluorescence of dissolved organic matter or phytoplankton is an example of
inelastic scattering (IOCCG, 2000).
The absorption and scattering coefficients are defined for the idealized
conditions of collimated, monochromatic flux incident normally on the
water, and traversing an infinitesimally thin layer of the water. (Scattering
coefficients are defined separately for elastic and inelastic scattering
processes.) Unlike the apparent optical properties (e.g., diffusive attenuation
coefficient for downwelling irradiance K d defined in Section 1.4.6) the
inherent properties do not depend on natural light conditions. A complete
description of the scattering process requires knowledge of the distribution
of the scattered light as a function of scattering angle.
Inherent optical properties of Case 1 waters primarily depend on
phytoplankton populations and accompanying materials. In Case 2 waters,
suspended particulate material and dissolved organic matter of aqueous or
terrestrial origins can influence inherent optical properties (in addition to and
independently on phytoplankton). The optical properties of substances other
than phytoplankton often dominate the bulk optical properties of Case 2
waters (Siegel and Michaels, 1996). In order to retrieve quantitative
information on the constituents of the water body from ocean color,
information on the inherent optical properties of each of major constituents
is required.
The development of techniques for the interpretation of ocean color in the
remote sensing context has been focused on the theoretical modeling of
ocean color as a function of inherent optical properties and on the
cataloguing of the inherent optical properties of substances encountered in
the near-surface ocean waters, as well as their variations with the
concentrations of the substances (IOCCG, 2000). Remarkably, the inherent
optical properties allow a simple addition of the contributions of the
individual components that can constitute a multi-component medium
(which may not work for apparent optical properties, especially in highly
scattering media). It is therefore feasible to resolve individual components
and their concentrations from remote sensing of the ocean color. Detailed
cataloguing of the inherent optical properties of the near-surface ocean
waters is important for development of the most sophisticated inverse
algorithms that also take into account the natural variability in the optical
signatures of these substances especially due to the influence of air-bubbles
populating the near-surface layer of the ocean.
452
scattering control the manner in which impinging photons propagate through
a natural water body and substantially determine the color of the ocean). The
process of absorption is simply the removal of photons from the light field,
while scattering changes the direction of photon propagation. Scattering of
photons can occur in both an elastic and inelastic manner. Elastic scattering
does not change the photon wavelength, while inelastic scattering does.
Fluorescence of dissolved organic matter or phytoplankton is an example of
inelastic scattering (IOCCG, 2000).
The absorption and scattering coefficients are defined for the idealized
conditions of collimated, monochromatic flux incident normally on the
water, and traversing an infinitesimally thin layer of the water. (Scattering
coefficients are defined separately for elastic and inelastic scattering
processes.) Unlike the apparent optical properties (e.g., diffusive attenuation
coefficient for downwelling irradiance K d defined in Section 1.4.6) the
inherent properties do not depend on natural light conditions. A complete
description of the scattering process requires knowledge of the distribution
of the scattered light as a function of scattering angle.
Inherent optical properties of Case 1 waters primarily depend on
phytoplankton populations and accompanying materials. In Case 2 waters,
suspended particulate material and dissolved organic matter of aqueous or
terrestrial origins can influence inherent optical properties (in addition to and
independently on phytoplankton). The optical properties of substances other
than phytoplankton often dominate the bulk optical properties of Case 2
waters (Siegel and Michaels, 1996). In order to retrieve quantitative
information on the constituents of the water body from ocean color,
information on the inherent optical properties of each of major constituents
is required.
The development of techniques for the interpretation of ocean color in the
remote sensing context has been focused on the theoretical modeling of
ocean color as a function of inherent optical properties and on the
cataloguing of the inherent optical properties of substances encountered in
the near-surface ocean waters, as well as their variations with the
concentrations of the substances (IOCCG, 2000). Remarkably, the inherent
optical properties allow a simple addition of the contributions of the
individual components that can constitute a multi-component medium
(which may not work for apparent optical properties, especially in highly
scattering media). It is therefore feasible to resolve individual components
and their concentrations from remote sensing of the ocean color. Detailed
cataloguing of the inherent optical properties of the near-surface ocean
waters is important for development of the most sophisticated inverse
algorithms that also take into account the natural variability in the optical
signatures of these substances especially due to the influence of air-bubbles
populating the near-surface layer of the ocean.
452