scholarly journals Connection between light-field parameters and optical properties of seawater

2002 ◽  
Author(s):  
Vladimir I. Haltrin ◽  
Donald R. Johnson ◽  
Vyacheslav A. Urdenko
Keyword(s):  
Optical Properties ◽  
Light Field

scholarly journals Determining Bottom Reflectance and Water Optical Properties Using Unmanned Underwater Vehicles under Clear or Cloudy Skies

2006 ◽  
Vol 23 (2) ◽  
pp. 314-324 ◽  
Author(s):  
David C. English ◽  
Kendall L. Carder
Keyword(s):  
Optical Properties ◽  
Water Column ◽  
Optical Sensors ◽  
Light Field ◽  
Field Measurements ◽  
Underwater Vehicles ◽  
Unmanned Underwater Vehicles ◽  
Cloudy Weather ◽  
Sea Grass ◽  
Ocean Color Imagery

Abstract An unmanned underwater vehicle (UUV) with hyperspectral optical sensors that measure downwelling irradiance and upwelling radiance was deployed over sandy bottoms, sea grass patches, and coral reefs near Lee Stocking Island, Bahamas, during the Coastal Benthic Optical Properties (CoBOP) program of 2000. These deployments occurred during both sunny and cloudy weather. If the rate of irradiance change due to cloud cover is slight, then the inclusion of a variable cloudy-irradiance factor will allow a reasonable estimation of water column absorption. Examination of data from a deployment in May 2000 under cloudy skies shows that the combination of hyperspectral light-field measurements, knowledge of the UUV's position in the water column, and a cloudy-irradiance factor permits consistent estimations of bottom reflectivity to be made from UUV measured reflectances. The spatial distribution of reflectance estimates obtained from a UUV may be useful for validation of airborne ocean color imagery.

scholarly journals The value of adding optics to ecosystem models: a case study

2007 ◽  
Vol 4 (3) ◽  
pp. 1585-1631 ◽  
Author(s):  
M. Fujii ◽  
E. Boss ◽  
F. Chai
Keyword(s):  
Optical Properties ◽  
Optical Model ◽  
Light Field ◽  
Ocean Color ◽  
Ecosystem Model ◽  
Model Parameters ◽  
Biogeochemical Processes ◽  
Ecosystem Models ◽  
Photo Oxidation ◽  
Subsurface Light

Abstract. Many ecosystem models have been developed to study the ocean's biogeochemistry, but most of these models use simple formulations to describe light penetration and spectral quality. Given that processes such as photosynthesis and photo-oxidation are uniquely important for biogeochemical processes in the upper ocean, it is necessary to model light distribution accurately. In addition, the global scale observations of proxies of biogeochemical variables are based on the color of the ocean. The ability to simulate the color of the ocean provides the possibility of comparing model simulation with these observations. Here, an optical model is coupled with a previously published ecosystem model that explicitly represents two phytoplankton (picoplankton and diatoms) and two zooplankton functional groups, as well as multiple nutrients and detritus. Surface ocean color field and subsurface light field are calculated by coupling the ecosystem model with an optical model that relates biogeochemical standing stocks with inherent optical properties (absorption, scattering); this provides input to a commercially available radiative transfer model (Ecolight). We apply this bio-optical model to the equatorial Pacific upwelling region, and find the model to be capable of reproducing many measured optical properties and key biogeochemical processes in this region. Results include large contributions by non-algal particles to the total scattering or attenuation (>50% at 660 nm) and their small contribution to particulate absorption (<20% at 440 nm), and a remarkable contribution by picoplankton to total phytoplankton absorption (>95% at 440 nm). These results are consistent with the field observations. In order to achieve such good agreement between data and model results, however, key model parameters, for which no field data is available, have to be constrained. Sensitivity analysis of the model results to optical parameters reveals the significant role of colored dissolved organic matter to the modeled properties. Coupling explicit optics to an ecosystem model provides several advantages in generating: (1) a more accurate subsurface light-field, which is important for light sensitive biogeochemical processes such as photosynthesis and photo-oxidation, (2) added constraints on model parameters that help to reduce uncertainties in ecosystem model simulations, and (3) model output which is comparable to basic remotely-sensed properties. In addition, the coupling of biogeochemical models and optics paves the road for future assimilation of ocean color and in-situ measured optical properties into the models.

Optical Effects of Large Particles

Ocean Optics ◽  
1994 ◽  
Author(s):  
Kendall L. Carder ◽  
David K. Costello
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Process Model ◽  
Light Field ◽  
Ocean Optics ◽  
Backscattering Coefficient ◽  
Model Inversion ◽  
Inherent Optical Properties ◽  
And Inversion ◽  
The Relationship

Two important problems facing the ocean optics research community in the coming decade concern optical model closure and inversion (see Chapter 3). We obtain model closure if we can describe the measured light environment by combining elementary measurements of the optical properties of the medium with radiative transfer theory. If we can accurately deduce the concentration of various constituents from a combination of measures of the submarine light field and inverse model calculations, we term this process model inversion. The most elementary measurements of the optical properties of the sea are those that are independent of the geometry of the light field, the inherent optical properties (Preisendorfer, 1961). Optical properties that are dependent on the geometry of the light field are termed apparent optical properties (AOP). Models of the submarine light field typically relate apparent optical properties to inherent optical properties (see Chapter 2). Examples include the relationship between the AOP irradiance reflectance R and a combination of inherent optical properties (backscattering coefficient bb and absorption coefficient a), and the relationship between the AOP downwelling diffuse attenuation coefficient kd and a combination of the absorption coefficient, backscattering coefficient, and downwelling average cosine μd (e.g., Gordon et al., 1975; Morel and Prieur, 1977; Smith and Baker, 1981; Morel, 1988; Kirk, 1984a). Under some circumstances these relationships work well enough that the absorption coefficient can be derived indirectly. This is important since measurement of the absorption coefficient by direct means has been difficult. Derived values for the absorption coefficient by model inversion methods are not easily verified by independent measurements, however, because of the difficulty of measuring the absorption coefficient. Model closure and model inversion both become more tenuous when the following phenomena are present: 1. Transpectral or inelastic scattering such as fluorescence (e.g., Gordon, 1979; Carder and Steward, 1985; Mitchell and Kiefer, 1988a; Spitzer and Dirks, 1985; Hawes and Carder, 1990) or water Raman scattering (Marshall and Smith, 1990; Stavn, 1990; Stavn and Weidemann, 1988a,b; Peacock et al, 1990; Chapter 12 this volume). 2. Particles that are large relative to the measurement volume for inherent optical property meters such as beam transmissometers, light-scattering photometers, fluorometers, and absorption meters.

Optical Closure: from Theory to Measurement

Ocean Optics ◽  
1994 ◽  
Author(s):  
J. Ronald V. Zaneveld
Keyword(s):  
Optical Properties ◽  
Light Field ◽  
Vertical Structure ◽  
Spectral Radiance ◽  
Major Influence ◽  
The Sun ◽  
Attenuation Coefficients ◽  
Inherent Optical Properties ◽  
Dissolved Matter ◽  
Beam Attenuation Coefficient

The intensity and spectrum of the light in the ocean have a major influence on the biological processes. These processes in turn determine the concentrations of much of the suspended and dissolved matter in the ocean, which affect the way in which the light is scattered and absorbed. These relationships can perhaps be most easily illustrated schematically as in Fig. 3-1. At the upper boundary we have the sun and sky radiances and the surface transmission conditions that combine to provide the energy entering through the surface. The ocean itself contains the vertical structure of those optical properties that do not depend on the structure of the light field, but depend only on the properties of the suspended and dissolved materials: the absorption coefficient a(λ,z), the beam attenuation coefficient c(λ,z), and the volume scattering function β(θ,λ,z). These are known as inherent optical properties, because they do not depend on the source radiance field (Preisendorfer, 1976). They are a function only of the suspended and dissolved materials in the water, and of the water itself. How does the vertical structure of the inherent optical properties affect the vertical structure of the radiance field in the ocean itself? This is the problem of radiative transfer in which we try to predict the intensity, direction, and spectrum of the light (spectral radiance) in the ocean, based on a set of given inherent optical properties. Those properties of the light field in the ocean that depend on the radiance are known as the apparent optical properties. Radiance field integrals, such as the vector irradiance, E(λ,z), the scalar irradiance E0(λ,z), and their attenuation coefficients are also apparent optical properties.

scholarly journals Altered inherent optical properties and estimates of the underwater light field during an Arctic under-ice bloom of Phaeocystis pouchetii

2017 ◽  
Vol 122 (6) ◽  
pp. 4939-4961 ◽  
Author(s):  
Alexey K. Pavlov ◽  
Torbjørn Taskjelle ◽  
Hanna M. Kauko ◽  
Børge Hamre ◽  
Stephen R. Hudson ◽  
...  
Keyword(s):  
Optical Properties ◽  
Light Field ◽  
Underwater Light Field ◽  
Inherent Optical Properties ◽  
Underwater Light ◽  
Phaeocystis Pouchetii

scholarly journals Avoiding Ship-Induced Light-Field Perturbation in the Determination of Oceanic Optical Properties

Oceanography ◽  
1990 ◽  
Vol 3 (2) ◽  
pp. 8-21 ◽  
Author(s):  
Kirk Waters ◽  
Raymond Smith ◽  
Marion Lewis
Keyword(s):  
Optical Properties ◽  
Light Field ◽  
Field Perturbation
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