Inversion of the volume scattering function and spectral absorption in coastal waters with biogeochemical implications

Abstract. In the aquatic environment, particles can be broadly separated into phytoplankton (PHY), non-algal particle (NAP) and dissolved (or very small particle, VSP) fractions. Typically, absorption spectra are inverted to quantify these fractions, but volume scattering functions (VSFs) can also be used. Both absorption spectra and VSFs were used to calculate particle fractions for an experiment in Chesapeake Bay. A complete set of water inherent optical properties was measured using a suite of commercial instruments and a prototype Multispectral Volume Scattering Meter (MVSM); the chlorophyll concentration, [Chl] was determined using the HPLC method. The total scattering coefficient (measured by an ac-s) and the VSF (at a few backward angles, measured by a HydroScat 6 and an ECO-VSF) agreed with the LISST and MVSM data within 5%, thus indicating inter-instrument consistency. The size distribution and scattering parameters for PHY, NAP and VSP were inverted from measured VSFs. For the absorption inversion, the "dissolved" absorption spectra were measured for filtrate passing through a 0.2 μm filter, whereas [Chl] and NAP absorption spectra were inverted from the particulate fraction. Even though the total scattering coefficient showed no correlation with [Chl], estimates of [Chl] from the VSF-inversion agreed well with the HPLC measurements (r = 0.68, mean relative error s = −20%). The scattering associated with NAP and VSP both correlated well with the NAP and "dissolved" absorption coefficients, respectively. While NAP dominated forward, and hence total, scattering, our results also suggest that the scattering by VSP was far from negligible and dominated backscattering.

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Biogeochemical origins of particles obtained from the inversion of the volume scattering function and spectral absorption in coastal waters

Biogeosciences ◽

10.5194/bg-10-6029-2013 ◽

2013 ◽

Vol 10 (9) ◽

pp. 6029-6043 ◽

Cited By ~ 21

Author(s):

X. Zhang ◽

Y. Huot ◽

D. J. Gray ◽

A. Weidemann ◽

W. J. Rhea

Keyword(s):

Absorption Spectra ◽

Chlorophyll Concentration ◽

Hplc Method ◽

Scattering Coefficient ◽

Volume Scattering ◽

Total Scattering ◽

Inherent Optical Properties ◽

Dissolved Matter ◽

Complete Set ◽

Relative Errors

Abstract. In the aquatic environment, particles can be broadly separated into phytoplankton (PHY), non-algal particle (NAP) and dissolved (or very small particle, VSP) fractions. Typically, absorption spectra are inverted to quantify these fractions, but volume scattering functions (VSFs) can also be used. Both absorption spectra and VSFs were used to estimate particle fractions for an experiment in the Chesapeake Bay. A complete set of water inherent optical properties was measured using a suite of commercial instruments and a prototype Multispectral Volume Scattering Meter (MVSM); the chlorophyll concentration, [Chl] was determined using the HPLC method. The total scattering coefficient measured by an ac-s and the VSF at a few backward angles measured by a HydroScat-6 and an ECO-VSF agreed with the LISST and MVSM data within 5%, thus indicating inter-instrument consistency. The size distribution and scattering parameters for PHY, NAP and VSP were inverted from measured VSFs. For the absorption inversion, the "dissolved" absorption spectra were measured for filtrate passing through a 0.2 μm filter, whereas [Chl] and NAP absorption spectra were inverted from the particulate fraction. Even though the total scattering coefficient showed no correlation with [Chl], estimates of [Chl] from the VSF-inversion agreed well with the HPLC measurements (r = 0.68, mean relative errors = −20%). The scattering associated with NAP and VSP both correlated well with the NAP and "dissolved" absorption coefficients, respectively. While NAP dominated forward, and hence total, scattering, our results also suggest that the scattering by VSP was far from negligible and dominated backscattering. Since the sizes of VSP range from 0.02 to 0.2 μm, covering (a portion of) the operationally defined "dissolved" matter, the typical assumption that colored dissolved organic matter (i.e., CDOM) does not scatter may not hold, particularly in a coastal or estuarine environment.

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VARIABILITY AND SPATIAL DISTRIBUTION OF TOTAL SCATTERING COEFFICIENTS OF SURFACE WATER IN VARIOUS SEASONS

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.29244/jitkt.v5i2.7571 ◽

2013 ◽

Vol 5 (2) ◽

Author(s):

Murjat Hi Untung ◽

Bisman Nababan ◽

Vincentus P. Siregar

Keyword(s):

Spatial Distribution ◽

Mississippi River ◽

Coastal Waters ◽

River Flow ◽

Moving Average ◽

Scattering Coefficient ◽

Distribution Data ◽

Total Scattering ◽

Scattering Coefficients ◽

Average Value

Variability and spatial distribution data of the total scattering coefficients ares useful in the development of bio-optical algorithms of ocean color satellite. The purpose of this study was to determine the variability and spatial distribution of the total scattering coefficient at 9 wavelengths (λ) in different seasons. Field data collection were conducted in the Northeastern Gulf of Mexico (NEGOM) of the spring , summer, and fall in 1999-2000 by using the ac-9 in-situ Spectrophotometer and restricted to coastal waters of 10 m isobath and offshore of 1000 m isobath. The data were filtered using the moving average method and tested with the Kruskal-Wallis. The results showed that the average value of the total scattering coefficients were significantly different among spring, summer, and fall. In general, the total scattering coefficients were relatively high, especially in the coastal waters near the mouth of the river each season and relatively low in offshore waters except during the summer that the total scattering coefficients were also relatively high in offshore watersdue to the intrusion of the Mississippi river flow toward offshore containing high nutrients that can promote the growth of phytoplankton in the offshore, suspended material and lower salinity jointly to increase the total scattering coefficients. Keywords: variability, spatial distribution, total scattering coefficient, bio-optic, NEGOM.

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VARIABILITY AND SPATIAL DISTRIBUTION OF TOTAL SCATTERING COEFFICIENTS OF SURFACE WATER IN VARIOUS SEASONS

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.28930/jitkt.v5i2.7571 ◽

2013 ◽

Vol 5 (2) ◽

Author(s):

Murjat Hi Untung ◽

Bisman Nababan ◽

Vincentus P. Siregar

Keyword(s):

Spatial Distribution ◽

Mississippi River ◽

Coastal Waters ◽

River Flow ◽

Moving Average ◽

Scattering Coefficient ◽

Distribution Data ◽

Total Scattering ◽

Scattering Coefficients ◽

Average Value

Variability and spatial distribution data of the total scattering coefficients ares useful in the development of bio-optical algorithms of ocean color satellite. The purpose of this study was to determine the variability and spatial distribution of the total scattering coefficient at 9 wavelengths (λ) in different seasons. Field data collection were conducted in the Northeastern Gulf of Mexico (NEGOM) of the spring , summer, and fall in 1999-2000 by using the ac-9 in-situ Spectrophotometer and restricted to coastal waters of 10 m isobath and offshore of 1000 m isobath. The data were filtered using the moving average method and tested with the Kruskal-Wallis. The results showed that the average value of the total scattering coefficients were significantly different among spring, summer, and fall. In general, the total scattering coefficients were relatively high, especially in the coastal waters near the mouth of the river each season and relatively low in offshore waters except during the summer that the total scattering coefficients were also relatively high in offshore watersdue to the intrusion of the Mississippi river flow toward offshore containing high nutrients that can promote the growth of phytoplankton in the offshore, suspended material and lower salinity jointly to increase the total scattering coefficients. Keywords: variability, spatial distribution, total scattering coefficient, bio-optic, NEGOM.

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Correlations between the Parameters of the Light Volume Scattering Functions in the Mediterranean Sea Surface Waters

Physical Oceanography ◽

10.22449/1573-160x-2021-5-514-524 ◽

2021 ◽

Vol 28 (5) ◽

Author(s):

V. I. Mankovsky ◽

E. V. Mankovskaya ◽

◽

Keyword(s):

Mediterranean Sea ◽

Suspended Matter ◽

Variation Coefficient ◽

Scattering Coefficient ◽

Asymmetry Coefficient ◽

Volume Scattering ◽

Total Scattering ◽

Angle Scattering ◽

The Asymmetry ◽

The Mediterranean

Purpose. The aim of the work is to study relationships between the parameters of the light volume scattering functions based on the data of their measurements in the Mediterranean Sea surface waters. Methods and Results. The data of measurements of the light volume scattering functions in the water samples taken in a few regions of the southern Mediterranean Sea, namely from the Strait of Gibraltar to the Levant Sea, as well as in the central part of the Aegean Sea and near the Dardanelles Strait (May, 1998) were used. The following parameters of the volume scattering functions were calculated: total scattering coefficient, and asymmetry and variation coefficients. The maximum and minimum values of the scattering coefficient were 0.21 and 0.09 m–1, respectively; and those for the asymmetry coefficient – 77.8 and 33.9. The variation coefficient of the angle scattering coefficients changed within 35–79%, its maximum and minimum values fell on the angles 7.5° and 162.5°, respectively. Obtained were the relations between the variation coefficient and the scattering angle, the asymmetry coefficient and the scattering coefficient, and the angle scattering coefficients and the total scattering coefficient. All of them possess high (more than 0.9) correlation coefficients. The coefficient value (51.7%) at the angle 2° does not correspond to general relation of the variation coefficient to the scattering angle. This fact is explained by different contributions of coarse and fine suspended matter to the light volume scattering function. At the angle 2°, the main contribution is made by a coarse (organic) suspended matter, whereas at the angles exceeding 7.5° – by a fine (mineral) suspension. Conclusions. The values of the variation coefficient of the angle scattering coefficient at the angles equal to 2° and exceeding 7.5° demonstrate variability of the coarse and fine suspended matter in the Mediterranean Sea, respectively. The equation for the relation between the asymmetry coefficient of the light volume scattering functions and the total scattering coefficient obtained for the Mediterranean Sea waters is close to the analogous one obtained for the Atlantic Ocean tropical waters. The angle 3.5° is optimal for determining the total scattering coefficient using the angle scattering coefficient for the Mediterranean Sea functions.

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The Relationship between the Inherent and the Apparent Optical Properties of Surface Waters and its Dependence on the Shape of the Volume Scattering Function

Ocean Optics ◽

10.1093/oso/9780195068436.003.0006 ◽

1994 ◽

Author(s):

John T. O. Kirk

Keyword(s):

Optical Properties ◽

Absorption Coefficient ◽

Water Body ◽

Small Sample ◽

Scattering Coefficient ◽

Scattering Function ◽

Parallel Beam ◽

Volume Scattering ◽

Inherent Optical Properties ◽

Aquatic Medium

Let us begin by reminding ourselves just what we mean by “the inherent optical properties” and “the apparent optical properties” of surface waters. The inherent optical properties are those that belong to the aquatic medium itself: properties that belong to a small sample of the aquatic medium taken out of the water body just as much as they belong to a great mass of the medium existing within the water body itself. The properties of particular concern to us are the absorption coefficient, a, the scattering coefficient, b, and the volume scattering function, β(θ). The absorption coefficient at a given wavelength is a measure of the intensity with which the medium absorbs light from a parallel beam per unit pathlength of medium (see Eq. 1.18). The scattering coefficient at a given wavelength is a measure of the intensity with which the medium scatters light from a parallel beam per unit pathlength of medium (see Eq. 1.17). Both a and b have the units, m-1. The normalized volume scattering function specifies the angular (θ) distribution of single-event scattering around the direction of a parallel incident beam. It is often normalized to total scattering and referred to as the scattering phase function, P(θ) (see Eq. 1.21). Since these properties belong, as I have already said, to a small sample of the medium, just as much as they do to a great slab of ocean, they can be measured in the laboratory. The absorption coefficients at various wavelengths can be measured with a suitable spectrophotometer: the scattering coefficient and the volume scattering function can be measured with a light scattering photometer. The apparent optical properties are not properties of the aquatic medium as such although they are closely dependent on the nature of the aquatic medium. In reality they are properties of the light field that, under the incident solar radiation stream, is established within the water body.

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Correlation between zooplankton population and the volume‐scattering coefficient

The Journal of the Acoustical Society of America ◽

10.1121/1.2001803 ◽

1975 ◽

Vol 58 (S1) ◽

pp. S101-S101

Author(s):

W. B. Anderson

Keyword(s):

Scattering Coefficient ◽

Volume Scattering ◽

Zooplankton Population

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Comparison of inherent optical properties as a surrogate for particulate matter concentration in coastal waters

Limnology and Oceanography Methods ◽

10.4319/lom.2009.7.803 ◽

2009 ◽

Vol 7 (11) ◽

pp. 803-810 ◽

Cited By ~ 62

Author(s):

Emmanuel Boss ◽

Lisa Taylor ◽

Sherryl Gilbert ◽

Kjell Gundersen ◽

Nathan Hawley ◽

...

Keyword(s):

Optical Properties ◽

Particulate Matter ◽

Coastal Waters ◽

Inherent Optical Properties ◽

Particulate Matter Concentration ◽

Matter Concentration

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Estimation of inherent optical properties using quasi-analytical algorithm along the coastal waters of southeast Arabian Sea

Ocean Dynamics ◽

10.1007/s10236-019-01287-x ◽

2019 ◽

Vol 69 (8) ◽

pp. 925-937

Author(s):

Kumaraswami Munnooru ◽

Sisir Kumar Dash ◽

Gijjapu Durga Rao ◽

Ramu Karri ◽

Vinjamuri Ranga Rao

Keyword(s):

Optical Properties ◽

Coastal Waters ◽

Arabian Sea ◽

Inherent Optical Properties ◽

Analytical Algorithm

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Optical backscattering properties of the "clearest" natural waters

Biogeosciences ◽

10.5194/bg-4-1041-2007 ◽

2007 ◽

Vol 4 (6) ◽

pp. 1041-1058 ◽

Cited By ~ 82

Author(s):

M. S. Twardowski ◽

H. Claustre ◽

S. A. Freeman ◽

D. Stramski ◽

Y. Huot

Keyword(s):

Natural Waters ◽

Pure Water ◽

Pigment Composition ◽

Volume Scattering ◽

Inherent Optical Properties ◽

Order Of Magnitude ◽

Low Levels ◽

Florisphaera Profunda ◽

Reflectance Measurements

Abstract. During the BIOSOPE field campaign October–December 2004, measurements of inherent optical properties from the surface to 500 m depth were made with a ship profiler at stations covering over 8000 km through the Southeast Pacific Ocean. Data from a ~3000 km section containing the very clearest waters in the central gyre are reported here. The total volume scattering function at 117°, βt(117°), was measured with a WET Labs ECO-BB3 sensor at 462, 532, and 650 nm with estimated uncertainties of 2×10-5, 5×10-6, and 2×10-6 m−1 sr−1, respectively. These values were approximately 6%, 3%, and 3% of the volume scattering by pure seawater at their respective wavelengths. From a methodological perspective, there were several results: – distributions were resolvable even though some of the values from the central gyre were an order of magnitude lower than the lowest previous measurements in the literature; – Direct in-situ measurements of instrument dark offsets were necessary to accurately resolve backscattering at these low levels; – accurate pure seawater backscattering values are critical in determining particulate backscattering coefficients in the open ocean (not only in these very clear waters); the pure water scattering values determined by Buiteveld et al. (1994) with a [1+0.3S/37] adjustment for salinity based on Morel (1974) appear to be the most accurate estimates, with aggregate accuracies as low as a few percent; and – closure was demonstrated with subsurface reflectance measurements reported by Morel et al. (2007) within instrument precisions, a useful factor in validating the backscattering measurements. This methodology enabled several observations with respect to the hydrography and the use of backscattering as a biogeochemical proxy: –The clearest waters sampled were found at depths between 300 and 350 m, from 23.5° S, 118° W to 26° S, 114° W, where total backscattering at 650 nm was not distinguishable from pure seawater; –Distributions of particulate backscattering bbp across the central gyre exhibited a broad particle peak centered ~100 m; –The particulate backscattering ratio typically ranged between 0.4% and 0.6% at 650 nm through the majority of the central gyre from the surface to ~210 m, indicative of "soft" water-filled particles with low bulk refractive index; and – bbp showed a distinct secondary deeper layer centered ~230 m that was absent in particulate attenuation cp data. The particulate backscattering ratio was significantly higher in this layer than in the rest of the water column, reaching 1.2% in some locations. This high relative backscattering, along with the pigment composition and ecological niche of this layer, appear to be consistent with the coccolithophorid Florisphaera profunda. Moreover, results were consistent with several expectations extrapolated from theory and previous work in oceanic and coastal regions, supporting the conclusion that particulate and total backscattering could be resolved in these extremely clear natural waters.

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