Simple model of the optical characteristics of bubbles and sediments in seawater of the surf zone

Zege, Eleonora P.; Katsev, I. L.; Prikhach, Alexander S.; Gilbert, Gary D.; Witherspoon, Ned H.

doi:10.1364/ao.45.006577

Cited by 11 publications

(6 citation statements)

References 5 publications

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“…A more nuanced approach is to treat whitecaps as a two-layered system where a semi-transparent layer of foam and bubbles overlays a background water reflectance (Frouin et al, 1996), as described further in the results. Radiative transfer modeling based on the theoretical work of Kokhanovsky (2004) and Zege et al (2006) is presented in the Results. Radiative modeling of whitecaps bridges the measured reflectance to the optical properties of foam.…”

Section: Discussionmentioning

confidence: 99%

“…The utility of this formulation would only be significant when there is a thin foam and the presumed R f is low. Hence, another way to consider the problem is to specify separate contributions from thick foam, as well as a semitransparent thin foam/bubble layer overlying the background water, which can also contain submerged bubbles, and potentially submerged bubbles without surface foam (Zege et al, 2006;Randolph et al, 2014). This would imply a fraction covered by the opaque whitecaps (A 1 ) and another fraction that may be covered by semitransparent layer (A 2 ).…”

Section: Estimation Of Whitecap Coverage With Known Background Reflecmentioning

confidence: 99%

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Hyperspectral Measurements, Parameterizations, and Atmospheric Correction of Whitecaps and Foam From Visible to Shortwave Infrared for Ocean Color Remote Sensing

Dierssen

2019

Front. Earth Sci.

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Breaking waves are highly reflective features on the sea surface that change the spectral properties of the ocean surface in both magnitude and spectral shape. Here, hyperspectral reflectance measurements of whitecaps from 400 to 2,500 nm were taken in Long Island Sound, USA of natural and manufactured breaking waves to explore new methods to estimate whitecap contributions to ocean color imagery. Whitecap reflectance was on average ∼40% in visible wavelengths and decreased significantly into the near infrared and shortwave infrared following published trends. The spectral shape was well-characterized by a third order polynomial function of liquid water absorption that can be incorporated into coupled ocean-atmospheric models and spectral optimization routines. Localized troughs in whitecap reflectance correspond to peaks in liquid water absorption and depths of the troughs are correlated to the amount and intensity of the breaking waves. Specifically, baseline-corrected band depths at 980 and 1,200 nm explained 77 and 90% of the whitecap-enhanced reflectance on a logarithmic scale, respectively. Including these wavebands into future ocean color sensors could potentially provide new tools to estimate whitecap contributions to reflectance more accurately than with wind speed. An effective whitecap factor was defined as the optical enhancements within a pixel due to whitecaps and foam independent of spatial scale. A simple mixed-pixel model of whitecap and background reflectance explained as much of the variability in measured reflectance as more complex models incorporating semi-transparent layers of foam. Using an example atmosphere, enhanced radiance from whitecaps was detectable at the top of the atmosphere and a multiple regression of at-sensor radiance at 880, 1,038, 1,250, and 1,615 nm explained 99% of the variability in whitecap factor. A proposed model of whitecap-free reflectance includes contributions from water-leaving radiance, glint, and diffuse reflected skylight. The epsilon ratio at 753 and 869 nm commonly used for aerosol model selection is nearly invariant with whitecap factor compared to the ratio at shortwave infrared bands. While more validation data is needed, this research suggests several promising avenues to retrieve estimates of the whitecap reflectance and to use ocean color to further elucidate the physics of wave breaking and gas exchange.

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Section: Discussionmentioning

confidence: 99%

Section: Estimation Of Whitecap Coverage With Known Background Reflecmentioning

confidence: 99%

Hyperspectral Measurements, Parameterizations, and Atmospheric Correction of Whitecaps and Foam From Visible to Shortwave Infrared for Ocean Color Remote Sensing

Dierssen

2019

Front. Earth Sci.

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“…First, we solved the set of Equations (37) and (38) with neglected last terms and then the expression for the moment L…”

Section: Equation For the Radiance Of Multiple Scattered Lightmentioning

confidence: 99%

“…n into Equation (37). As a result, from (37)- (39) and (35) we obtained the expressions for the parameters of the function Q 3 :…”

Section: Equation For the Radiance Of Multiple Scattered Lightmentioning

confidence: 99%

New Theoretical Model of the Irradiance Distribution in Water from a Unidirectional Point Source

Долин

2020

JMSE

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Formulas are presented for calculating the irradiance field, which is formed in a turbid medium with a narrow scattering phase function and homogeneous optical properties when an infinitely narrow light beam passes through it. The calculations are based on a new mathematical model of the stationary radiation field of an omnidirectional point source and relationships enabling one to represent the irradiance distribution in a continuous or modulated light beam through this field. The obtained formulas, in contrast to the previously known ones, permit taking into account the temporal spreading of a pulsed light beam in the sea without a significant decrease in the accuracy of describing its spatial structure.

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“…The intensity of light scattered by surfzone bubbles and sand increases with a reduction in scattering angle (Zege et al. 2006 ). Therefore, the smaller SCUFA scattering angle increases the excitation light incident on the detection filter, enhancing spurious dye measurements.…”

Section: Considerations For In Situ Surfzone Rhodamine Wt Measurementmentioning

confidence: 99%

Measuring Fluorescent Dye in the Bubbly and Sediment-Laden Surfzone

Clark

Feddersen

Omand

et al. 2009

Water Air Soil Pollut

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Decisions about recreational beach closures would be enhanced if better estimates of surfzone contaminant transport and dilution were available. In situ methods for measuring fluorescent Rhodamine WT dye tracer in the surfzone are presented, increasing the temporal and spatial resolution over previous surfzone techniques. Bubbles and sand suspended by breaking waves in the surfzone interfere with in situ optical fluorometer dye measurements, increasing the lower bound for dye detection (≈ 1 ppb) and reducing (quenching) measured dye concentrations. Simultaneous turbidity measurements are used to estimate the level of bubble and sand interference and correct dye estimates. After correction, root-mean-square dye concentration errors are estimated to be < 5% of dye concentration magnitude, thus demonstrating the viability of in situ surfzone fluorescent dye measurements. The surfzone techniques developed here may be applicable to other environments with high bubble and sand concentrations (e.g., cascading rivers and streams).

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Simple model of the optical characteristics of bubbles and sediments in seawater of the surf zone

Cited by 11 publications

References 5 publications

Hyperspectral Measurements, Parameterizations, and Atmospheric Correction of Whitecaps and Foam From Visible to Shortwave Infrared for Ocean Color Remote Sensing

Hyperspectral Measurements, Parameterizations, and Atmospheric Correction of Whitecaps and Foam From Visible to Shortwave Infrared for Ocean Color Remote Sensing

New Theoretical Model of the Irradiance Distribution in Water from a Unidirectional Point Source

Measuring Fluorescent Dye in the Bubbly and Sediment-Laden Surfzone

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