This characteristic is a convolution of (a) absorbing and scattering properties of
the water medium, and (b) geometry of propagation of the light flux beneath the
water surface.
In the three Practices below, the specific features of sun light transfer in natural
waters is investigated by means of numerical simulations followed by subsequent
analysis of emerged changes in the spectral composition of the coefficient of diffuse
reflection of sunlight immediately beneath the water surface, R(À0,l).
In Practice 15 the spectral variability in R(À0,l) is investigated as a function of
concentration of color producing agents (CPAs) inherent in natural waters. By
CPAs we assume the substances whose participation in the processes of sunlight
absorption, scattering and Raman inelastic scattering emission effects control the
intensity and spectral composition of light leaving the water-atmosphere interface.
Such group of water constituents incorporates, inter alia, phytoplankton (whose
cells encapsulate chlorophyll), mineral suspended matter and colored dissolved
organics. As it will be stressed below, the water leaving radiative signal is also
controlled by the bottom depth and its albedo.
Within the framework of the present Practices collection, the students are invited
to familiarize themselves with the specific processes controlling the formation of
water color characteristics (Practice 16) as well as with one of the methods of
retrieval of CPA concentrations to the effect of remote sensing of natural water
bodies (Practice 17).
A hydro-optical model developed for Lake Ladoga will be offered for effecting
of the aforementioned exercises. The model is a set of tabulated spectral values of
specific coefficients (cross-sections) of absorption and backscattering of the three
CPAs, viz. phytoplankton chlorophyll, suspended mineral particulates and
dissolved organic matter. This choice of CPAs is dictated by the typical/predominant
hydro-optical constituents in Lake Ladoga. Through numerous investigations, it
was shown that the suggested hydro-optical model of Lake Ladoga proves to be
adequate for a wide range of hydro-optical conditions, and thus could be considered
as confidently representative of waters at mid latitudes. The present set of exercises
leaves beyond scope the pelagic marine waters as most hydro-optically simple, and
thus not presenting some particular interest in light of studying the formation of
water leaving radiative signal in the visible.
In addition to such mechanisms of interaction of solar light with the aquatic
medium as absorption and elastic scattering, which participate in forming the
radiance signal coming up from beneath the water surface in the case of all
types of natural waters, in inland water bodies as well as marine coastal shallow
zones, a significant impact on the spectral composition of water leaving radiance
signal can be generated by such internal sources of radiation as phytoplankton
fluorescence and dissolved organic matter (due to their typically high content).
The other subsurface source of optical/radiative influence on the emerging
light in such environments is constituted by the optical influence of the bottom.
This in turn, can appreciably affect the accuracy of retrieval of water quality
parameters.
16.1 Concise Theory
157
the water medium, and (b) geometry of propagation of the light flux beneath the
water surface.
In the three Practices below, the specific features of sun light transfer in natural
waters is investigated by means of numerical simulations followed by subsequent
analysis of emerged changes in the spectral composition of the coefficient of diffuse
reflection of sunlight immediately beneath the water surface, R(À0,l).
In Practice 15 the spectral variability in R(À0,l) is investigated as a function of
concentration of color producing agents (CPAs) inherent in natural waters. By
CPAs we assume the substances whose participation in the processes of sunlight
absorption, scattering and Raman inelastic scattering emission effects control the
intensity and spectral composition of light leaving the water-atmosphere interface.
Such group of water constituents incorporates, inter alia, phytoplankton (whose
cells encapsulate chlorophyll), mineral suspended matter and colored dissolved
organics. As it will be stressed below, the water leaving radiative signal is also
controlled by the bottom depth and its albedo.
Within the framework of the present Practices collection, the students are invited
to familiarize themselves with the specific processes controlling the formation of
water color characteristics (Practice 16) as well as with one of the methods of
retrieval of CPA concentrations to the effect of remote sensing of natural water
bodies (Practice 17).
A hydro-optical model developed for Lake Ladoga will be offered for effecting
of the aforementioned exercises. The model is a set of tabulated spectral values of
specific coefficients (cross-sections) of absorption and backscattering of the three
CPAs, viz. phytoplankton chlorophyll, suspended mineral particulates and
dissolved organic matter. This choice of CPAs is dictated by the typical/predominant
hydro-optical constituents in Lake Ladoga. Through numerous investigations, it
was shown that the suggested hydro-optical model of Lake Ladoga proves to be
adequate for a wide range of hydro-optical conditions, and thus could be considered
as confidently representative of waters at mid latitudes. The present set of exercises
leaves beyond scope the pelagic marine waters as most hydro-optically simple, and
thus not presenting some particular interest in light of studying the formation of
water leaving radiative signal in the visible.
In addition to such mechanisms of interaction of solar light with the aquatic
medium as absorption and elastic scattering, which participate in forming the
radiance signal coming up from beneath the water surface in the case of all
types of natural waters, in inland water bodies as well as marine coastal shallow
zones, a significant impact on the spectral composition of water leaving radiance
signal can be generated by such internal sources of radiation as phytoplankton
fluorescence and dissolved organic matter (due to their typically high content).
The other subsurface source of optical/radiative influence on the emerging
light in such environments is constituted by the optical influence of the bottom.
This in turn, can appreciably affect the accuracy of retrieval of water quality
parameters.
16.1 Concise Theory
157