scholarly journals Measuring and Modeling the Polarized Upwelling Radiance Distribution in Clear and Coastal Waters

2018 ◽  
Vol 8 (12) ◽  
pp. 2683 ◽  
Author(s):  
Arthur Gleason ◽  
Kenneth Voss ◽  
Howard Gordon ◽  
Michael Twardowski ◽  
Jean-François Berthon
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Field Experiments ◽  
Absolute Error ◽  
Mueller Matrix ◽  
Spectral Radiance ◽  
Remote Measurement ◽  
Inherent Optical Properties ◽  
Satellite Sensors ◽  
Radiance Distribution

The upwelling spectral radiance distribution is polarized, and this polarization varies with the optical properties of the water body. Knowledge of the polarized, upwelling, bidirectional radiance distribution function (BRDF) is important for generating consistent, long-term data records for ocean color because the satellite sensors from which the data are derived are sensitive to polarization. In addition, various studies have indicated that measurement of the polarization of the radiance leaving the ocean can used to determine particle characteristics (Tonizzo et al., 2007; Ibrahim et al., 2016; Chami et al., 2001). Models for the unpolarized BRDF (Morel et al., 2002; Lee et al., 2011) have been validated (Voss et al., 2007; Gleason et al., 2012), but variations in the polarization of the upwelling radiance due to the sun angle, viewing geometry, dissolved material, and suspended particles have not been systematically documented. In this work, we simulated the upwelling radiance distribution using a Monte Carlo-based radiative transfer code and measured it using a set of fish-eye cameras with linear polarizing filters. The results of model-data comparisons from three field experiments in clear and turbid coastal conditions showed that the degree of linear polarization (DOLP) of the upwelling light field could be determined by the model with an absolute error of ±0.05 (or 5% when the DOLP was expressed in %). This agreement was achieved even with a fixed scattering Mueller matrix, but did require in situ measurements of the other inherent optical properties, e.g., scattering coefficient, absorption coefficient, etc. This underscores the difficulty that is likely to be encountered using the particle scattering Mueller matrix (as indicated through the remote measurement of the polarized radiance) to provide a signature relating to the properties of marine particles beyond the attenuation/absorption coefficient.

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 Detailed validation of the bidirectional effect in various Case 1 waters for application to ocean color imagery

2007 ◽  
Vol 4 (5) ◽  
pp. 781-789 ◽  
Author(s):  
K. J. Voss ◽  
A. Morel ◽  
D. Antoine
Keyword(s):  
Current Model ◽  
Distribution Data ◽  
Noise Sources ◽  
Water Parameters ◽  
Inherent Optical Properties ◽  
Wide Range ◽  
Satellite Sensors ◽  
Ocean Color Imagery ◽  
Radiance Distribution ◽  
Measured Water

Abstract. The radiance viewed from the ocean depends on the illumination and viewing geometry along with the water properties, and this variation is called the bidirectional effect. This bidirectional effect depends on the inherent optical properties of the water, including the volume scattering function, and is important when comparing data from different satellite sensors. The current model of f/Q, which contains the bidirectional effect, by Morel et al. (2002) depends on modeled, not measured, water parameters, thus must be carefully validated. In this paper we combined upwelling radiance distribution data from several cruises, in varied water types and with a wide range of solar zenith angles. We compared modeled and measured Lview/Lnadir and found that the average difference between the model and data was less than 0.01, while the RMS difference between the model and data was on the order of 0.02–0.03. This is well within the statistical noise of the data, which was on the order of 0.04–0.05, due to environmental noise sources such as wave focusing.

scholarly journals Underwater Radiance Distributions Measured with Miniaturized Multispectral Radiance Cameras

2013 ◽  
Vol 30 (1) ◽  
pp. 74-95 ◽  
Author(s):  
David Antoine ◽  
André Morel ◽  
Edouard Leymarie ◽  
Amel Houyou ◽  
Bernard Gentili ◽  
...  
Keyword(s):  
Optical Properties ◽  
Complementary Metal Oxide Semiconductor ◽  
Optical Quality ◽  
Low Noise ◽  
Oxide Semiconductor ◽  
Significant Advance ◽  
Inherent Optical Properties ◽  
Camera Design ◽  
Radiance Distribution

Abstract Miniaturized radiance cameras measuring underwater multispectral radiances in all directions at high-radiometric accuracy (CE600) are presented. The camera design is described, as well as the main steps of its optical and radiometric characterization and calibration. The results show the excellent optical quality of the specifically designed fish-eye objective. They also show the low noise and excellent linearity of the complementary metal oxide semiconductor (CMOS) detector array that is used. Initial results obtained in various oceanic environments demonstrate the potential of this instrument to provide new measurements of the underwater radiance distribution from the sea surface to dimly lit layers at depth. Excellent agreement is obtained between nadir radiances measured with the camera and commercial radiometers. Comparison of the upwelling radiance distributions measured with the CE600 and those obtained with another radiance camera also shows a very close agreement. The CE600 measurements allow all apparent optical properties (AOPs) to be determined from integration of the radiance distributions and inherent optical properties (IOPs) to be determined from inversion of the AOPs. This possibility represents a significant advance for marine optics by tying all optical properties to the radiometric standard and avoiding the deployment of complex instrument packages to collect AOPs and IOPs simultaneously (except when it comes to partitioning IOPs into their component parts).

scholarly journals ESTIMATION OF OPTICAL PROPERTIES USING QAA-V6 MODEL BASED ON MODIS DATA

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 937-940
Author(s):  
J. Zhan ◽  
D. J. Zhang ◽  
G. Y. Zhang ◽  
C. X. Wang ◽  
G. Q. Zhou
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Biological Properties ◽  
Ocean Colour ◽  
Data Set ◽  
Modis Data ◽  
Inherent Optical Properties ◽  
Physical Chemical ◽  
Analytical Algorithm ◽  
Ocean Colour Remote Sensing

Abstract. Optical property parameters play an important role in ocean colour studies. As a key variable, the absorption coefficient is of great significance for calculating the content of each component in water and simulating the physical, chemical and biological properties of water. The inversion algorithms mainly include empirical model, semi-analytical model and neural network model. In this study, we focused on the QAA_V6, which is the newest version of Quasi-Analytical Algorithm (QAA). It is necessary to test the QAA_V6 model in different conditions. IOCCG data set is used to verify the accuracy of QAA_V6. Additionally, MODIS data of case 1 waters and case 2 waters were selected. After extraction and matching, the data was finally imported into QAA_V6 model to calculate the absorption coefficient with a R2 of 0.999 in both case 1 waters and case 2 waters, thus the QAA_V6 model showed a high accuracy and robust applicability in the inversion of inherent optical properties. Subsequently, it can be further verified for the waters in more complicated areas, providing a firm foundation for implementing QAA into the research of ocean colour remote sensing.

scholarly journals Detailed validation of the bidirectional effect in various Case 1 waters for application to Ocean Color imagery

2007 ◽  
Vol 4 (3) ◽  
pp. 2069-2093
Author(s):  
K. J. Voss ◽  
A. Morel ◽  
D. Antoine
Keyword(s):  
Current Model ◽  
Average Error ◽  
Distribution Data ◽  
Noise Sources ◽  
Water Parameters ◽  
Inherent Optical Properties ◽  
Wide Range ◽  
Satellite Sensors ◽  
Ocean Color Imagery ◽  
Radiance Distribution

Abstract. The radiance viewed from the ocean depends on the illumination and viewing geometry along with the water properties and this variation is called the bidirectional effect, or BRDF of the water. This BRDF depends on the inherent optical properties of the water, including the volume scattering function, and is important when comparing data from different satellite sensors. The current model by Morel et al. (2002) depends on modeled water parameters, thus must be carefully validated. In this paper we combined upwelling radiance distribution data from several cruises, in varied water types and with a wide range of solar zenith angles. We found that the average error of the model, when compared to the data was less than 1%, while the RMS difference between the model and data was on the order of 0.02–0.03. This is well within the statistical noise of the data, which was on the order of 0.04–0.05, due to environmental noise sources such as wave focusing.

scholarly journals A Semi-Empirical Chlorophyll-a Retrieval Algorithm Considering the Effects of Sun Glint, Bottom Reflectance, and Non-Algal Particles in the Optically Shallow Water Zones of Sanya Bay Using SPOT6 Data

2020 ◽  
Vol 12 (17) ◽  
pp. 2765
Author(s):  
Yan Yu ◽  
Shengbo Chen ◽  
Wenhan Qin ◽  
Tianqi Lu ◽  
Jian Li ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Chlorophyll A ◽  
Coastal Waters ◽  
Green Band ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Sanya Bay ◽  
Semi Empirical ◽  
Empirical Algorithms

Chlorophyll-a (Chl-a) concentration retrieval is essential for water quality monitoring, aquaculture, and guiding coastline infrastructure construction. Compared with common ocean color satellites, land observation satellites have the advantage of a higher resolution and more data sources for retrieving the concentration of Chl-a from optically shallow waters. However, the sun glint (Rsg), bottom reflectance (Rb), and non-algal particle (NAP) derived from terrigenous matter affect the accuracy of Chl-a concentration retrieval using land observation satellite image data. In this paper, we propose a semi-empirical algorithm based on the remote sensing reflectance (Rrs) of SPOT6 to retrieve the Chl-a concentration in Sanya Bay (SYB), considering the effect of Rsg, Rb, and NAP. In this semi-empirical algorithm, the Cox–Munk anisotropic model and radiative transfer model (RTM) were used to reduce the effects of Rsg and Rb on Rrs, and the Chl-a concentration was retrieved by the Chl-a absorption coefficient at 490 nm (aphy(490)) to remove the effect of NAP. The semi-empirical algorithm was in the form of Chl-a = 43.3[aphy(490)]1.454, where aphy (490) was calculated by the total absorption coefficient and the absorption coefficients of each component by empirical algorithms. The results of the Chl-a concentration retrieval show the following: (1) SPOT6 data are available for Chl-a retrieval using this semi-empirical algorithm in oligotrophic or mesotrophic coastal waters, and the accuracy of the algorithm can be improved by removing the effects of Rsg, Rb, and NAP (R2 from 0.71 to 0.93 and root mean square error (RMSE) from 0.23 to 0.11 ug/L); (2) empirical algorithms based on the blue-green band are suitable for oligotrophic or mesotrophic coastal waters, and the algorithm based on the blue-green band difference Chl-a index (DCI) has stronger anti-interference in terms of the effects of sun glint and bottom reflectance than the algorithm based on the blue-green ratio (BGr); (3) in the case of ignoring Rsg unrelated to inherent optical properties (IOPs), NAP is the biggest interference factor when >9.5 mg/L and the effect of bottom reflectance should be considered when the water depth (H) <5 m in SYB; and (4) the inherent optical properties of the waters in SYB are dominated by NAP (Chl-a = 0.2–2.6 ug/L and NAP = 2.2–30.1 mg/L), and the nutrients are concentrated by enclosed terrain and southeast current. This semi-empirical algorithm for Chl-a concentration retrieval has the potential to monitor Chl-a in oligotrophic and mesotrophic coastal waters using other land observation satellites (e.g., Landsat8 OLI, ASTER, and GaoFen2).

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