Optical scattering and backscattering by organic and inorganic particulates in U.S. coastal waters
TL;DR: The results of a study of optical scattering and backscattering of particulates for three coastal sites that represent a wide range of optical properties that are found in U.S. near-shore waters can be well approximated by a power-law function of wavelength.
Abstract: We present the results of a study of optical scattering and backscattering of particulates for three coastal sites that represent a wide range of optical properties that are found in U.S. near-shore waters. The 6000 scattering and backscattering spectra collected for this study can be well approximated by a power-law function of wavelength. The power-law exponent for particulate scattering changes dramatically from site to site (and within each site) compared with particulate backscattering where all the spectra, except possibly the very clearest waters, cluster around a single wavelength power-law exponent of -0.94. The particulate backscattering-to-scattering ratio (the backscattering ratio) displays a wide range in wavelength dependence. This result is not consistent with scattering models that describe the bulk composition of water as a uniform mix of homogeneous spherical particles with a Junge-like power-law distribution over all particle sizes. Simultaneous particulate organic matter (POM) and particulate inorganic matter (PIM) measurements are available for some of our optical measurements, and site-averaged POM and PIM mass-specific cross sections for scattering and backscattering can be derived. Cross sections for organic and inorganic material differ at each site, and the relative contribution of organic and inorganic material to scattering and backscattering depends differently at each site on the relative amount of material that is present.
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TL;DR: In this paper, a TSM algorithm is developed for turbid waters, suitable for any ocean colour sensor including MERIS, MODIS and SeaWiFS. But it does not consider the effect of bidirectional effects.
498 citations
Cites background from "Optical scattering and backscatteri..."
...Snyder et al. (2008) report mass-specific backscatter at 630 nm of up to about 0.025 m2g−1 for particulate organic matter at the LEO-15 site but highly variable values at other sites down to less than 0.001 m2g−1 with large but not systematic differences between the organic and inorganic fractions....
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TL;DR: In this paper, a semi-empirical single-band turbidity retrieval algorithm using the near infrared (NIR) band at 859 nm in highly turbid waters is assessed.
290 citations
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...…matter which varied between 0.01 and 0.06, with a mean value of approximately 0.02 (e.g. Boss et al., 2004; Chami, McKee, Leymarie, & Khomenko, 2006; Loisel, Mériaux, Berthon, & Poteau, 2007; McKee et al., 2009; Snyder et al., 2008; Tzortziou et al., 2006; Whitmire, Boss, Cowles, & Pegau, 2007)....
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...02 (e.g. Boss et al., 2004; Chami, McKee, Leymarie, & Khomenko, 2006; Loisel, Mériaux, Berthon, & Poteau, 2007; McKee et al., 2009; Snyder et al., 2008; Tzortziou et al., 2006; Whitmire, Boss, Cowles, & Pegau, 2007)....
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TL;DR: In this article, the authors analyzed the relationship between the concentration of suspended particles represented by dry mass and optical properties, including particle beam attenuation, side scattering, and backscattering, obtained from an intensive sampling program in coastal and offshore waters around Europe and French Guyana.
Abstract: This study analyzes relationships between concentration of suspended particles represented by dry mass, [SPM], or area, [AC], and optical properties including particulate beam attenuation (cp), side scattering (bs), and backscattering (bbp), obtained from an intensive sampling program in coastal and offshore waters around Europe and French Guyana. First-order optical properties are driven by particle concentration with best predictions of [SPM] by bbp and bs, and of [AC] by cp. Second-order variability is investigated with respect to particle size, apparent density (dry weight-to-wet-volume ratio), and composition. Overall, the mass-specific particulate backscattering coefficient, b m (5bbp:[SPM]), is relatively well constrained, with variability of a factor of 3–4. This coefficient is well correlated with particle composition, with inorganic particles having values about three times greater (b m5 0.012 m2 g21) than organic particles (b m5 0.005 m 2 g21). The mass-specific particulate attenuation coefficient, c m (5cp:[SPM]), on the other hand, varies over one order of magnitude and is strongly driven (77% of the variability explained) by particle apparent density. In this data set particle size does not affect c m and affects b m only weakly in clear (case 1) waters, despite size variations over one order of magnitude. A significant fraction (40–60% )o f the variability inb m remains unexplained. Possible causes are the limitation of the measured size distributions to the 2–302-mm range and effects of particle shape and internal structure that affect bbp more than cp and were not accounted for.
174 citations
Cites background or result from "Optical scattering and backscatteri..."
...Several studies in U.S. coastal waters showed that [SPM] correlates better with bbp than with cp or bp (Snyder et al. 2008; Boss et al. 2009a)....
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...Snyder et al. (2008) show evidence of spatial variability of b mbp along the U.S. coast and found significant differences between the massspecific coefficients bbp : [PIM] and bbp : [POM], where [POM] is the particulate organic matter concentration, and [SPM] 5 [PIM] + [POM]....
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...The spectral dependency of cp or bbp is beyond the scope of this paper and has been investigated by other authors (Snyder et al. 2008)....
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...[POM]- and [PIM]-specific bbp vary between 0.001 and 0.05 m2 g21, which is in good agreement with the 0.001–0.025 m2 g21 range reported by Snyder et al. (2008) where [POM] : [SPM] varied between 34% and 70%....
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TL;DR: In this paper, the authors examined the relationship between spectral bbp and bp vs. [Chl] along an 8000 km transect crossing the Case 1 waters of the eastern South Pacific Gyre.
Abstract: . The particulate scattering, bp, and backscattering, bbp, coefficients are determined by the concentration and physical properties of suspended particles in the ocean. They provide a simple description of the influence of these particles on the scattering of light within the water column. For the remote observation of ocean color, bbp along with the total absorption coefficient govern the amount and spectral qualities of light leaving the sea surface. However, for the construction and validation of ocean color models measurements of bbp are still lacking, especially at low chlorophyll a concentrations ([Chl]). Here, we examine the relationships between spectral bbp and bp vs. [Chl] along an 8000 km transect crossing the Case 1 waters of the eastern South Pacific Gyre. In these waters, over the entire range of [Chl] encountered (~0.02–2 mg m3), both bbp and bp can be related to [Chl] by power functions (i.e. bp or bbp=α[Chl]β). Regression analyses are carried out to provide the parameters α and β for several wavelengths throughout the visible for both bbp and bp. When applied to the data, these functions retrieve the same fraction of variability in bbp and bp (coefficients of determination between 0.82 and 0.88). The bbp coefficient fall within the bounds of previous measurements at intermediate and high [Chl] recently published. Its dependence on [Chl] below ~0.1 mg m−3 is described for the first time with in situ data. The backscattering ratio (i.e. bbp/bp) with values near 0.01 for all stations appears to be spectrally neutral and not significantly dependent on [Chl]. These results should foster the development of improved forward models of the mean optical properties for oceanic Case 1 waters as well as inverse models based upon them.
151 citations
TL;DR: Woźniak et al. as mentioned in this paper measured the hyperspectral inherent optical properties (IOPs) of seawater (particulate beam attenuation, particulate and CDOM absorption coefficients within the spectral range 300-850 nm), particle size distribution (PSD) within the diameter range 2-60 mm, and the mass concentrations of suspended particulate matter (SPM), particulate organic carbon (POC), and chlorophyll a (Chl).
Abstract: Beach, California, over a period of 1.5 years. Measurements included the hyperspectral inherent optical properties (IOPs) of seawater (particulate beam attenuation, particulate and CDOM absorption coefficients within the spectral range 300–850 nm), particle size distribution (PSD) within the diameter range 2–60 mm, and the mass concentrations of suspended particulate matter (SPM), particulate organic carbon (POC), and chlorophyll a (Chl). The particulate assemblage spanned a wide range of concentrations and composition, from the dominance of mineral particles (POC/SPM 0.25) with considerably greater contribution of larger‐sized particles. Large variability in the particulate characteristics produced correspondingly large variability in the IOPs; up to 100‐fold variation in particulate absorption and scattering coefficients and several‐fold variation in the SPM‐specific and POC‐specific coefficients. Analysis of these data demonstrates that knowledge of general characteristics about the particulate composition and size distribution leads to improved interpretations of the observed optical variability. We illustrate a multistep empirical approach for estimating proxies of particle concentration (SPM and POC), composition (POC/SPM), and size distribution (median diameter) from the measured IOPs in a complex coastal environment. The initial step provides information about a proxy for particle composition; other particulate characteristics are subsequently derived from relationships specific to different categories of particulate composition. Citation: Woźniak, S. B., D. Stramski, M. Stramska, R. A. Reynolds, V. M. Wright, E. Y. Miksic, M. Cichocka, and A. M. Cieplak (2010), Optical variability of seawater in relation to particle concentration, composition, and size distribution in the nearshore marine environment at Imperial Beach, California, J. Geophys. Res., 115, C08027, doi:10.1029/2009JC005554.
111 citations
Cites background or methods from "Optical scattering and backscatteri..."
...…in the Irish Sea [McKee and Cunningham, 2006], tropical coastal waters of eastern Australia [Oubelkheir et al., 2006], eastern English Channel [Vantrepotte et al., 2007], and coastal waters off New Jersey, the Northern Gulf of Mexico, and Monterey Bay [Snyder et al., 2008; Stavn and Richter, 2008]....
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...The use of POC/SPM ratio as a proxy for particulate composition could also be enhanced by additional determinations of POM and PIM from the LOI technique [e.g., Stavn and Richter, 2008]....
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References
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Book•
01 Jun 1969
TL;DR: In this paper, Monte Carlo techniques are used to fit dependent and independent variables least squares fit to a polynomial least-squares fit to an arbitrary function fitting composite peaks direct application of the maximum likelihood.
Abstract: Uncertainties in measurements probability distributions error analysis estimates of means and errors Monte Carlo techniques dependent and independent variables least-squares fit to a polynomial least-squares fit to an arbitrary function fitting composite peaks direct application of the maximum likelihood. Appendices: numerical methods matrices graphs and tables histograms and graphs computer routines in Pascal.
12,737 citations
TL;DR: Numerical methods matrices graphs and tables histograms and graphs computer routines in Pascal and Monte Carlo techniques dependent and independent variables least-squares fit to a polynomial least-square fit to an arbitrary function fitting composite peaks direct application of the maximum likelihood.
Abstract: Uncertainties in measurements probability distributions error analysis estimates of means and errors Monte Carlo techniques dependent and independent variables least-squares fit to a polynomial least-squares fit to an arbitrary function fitting composite peaks direct application of the maximum likelihood. Appendices: numerical methods matrices graphs and tables histograms and graphs computer routines in Pascal.
10,546 citations
1,095 citations
TL;DR: If rho is not estimated accurately, significant errors can occur in the estimated R(rs) for near-zenith Sun positions and for high wind speeds, both of which can give considerable Sun glitter effects.
Abstract: The remote-sensing reflectance Rrs is not
directly measurable, and various methodologies have been employed in
its estimation. I review the radiative transfer foundations of
several commonly used methods for estimating
Rrs, and errors associated with estimating
Rrs by removal of surface-reflected sky radiance
are evaluated using the Hydrolight radiative transfer numerical
model. The dependence of the sea surface reflectance factor ρ,
which is not an inherent optical property of the surface, on sky
conditions, wind speed, solar zenith angle, and viewing geometry is
examined. If ρ is not estimated accurately, significant errors
can occur in the estimated Rrs for near-zenith
Sun positions and for high wind speeds, both of which can give
considerable Sun glitter effects. The numerical simulations suggest
that a viewing direction of 40 deg from the nadir and 135 deg from the
Sun is a reasonable compromise among conflicting requirements. For
this viewing direction, a value of ρ ≈ 0.028 is acceptable
only for wind speeds less than 5 m s-1. For
higher wind speeds, curves are presented for the determination of ρ
as a function of solar zenith angle and wind speed. If the sky is
overcast, a value of ρ ≈ 0.028 is used at all wind
speeds.
1,014 citations
01 Jan 1974
665 citations
"Optical scattering and backscatteri..." refers background in this paper
...At these low levels of particulate backscattering, the average power-law exponent could be consistent with the average value seen at higher backscattering levels if our pure water backscattering correction [32] is reduced by 15%....
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