A calibration diagram of specific beam attenuation

Spinrad, Richard W.

doi:10.1029/jc091ic06p07761

Cited by 47 publications

(21 citation statements)

References 24 publications

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“…In lake waters the scattering coefficient is normally much larger than the absorption coefficient, particularly at 660 nm. Consequently, variations in c are largely the result of variations in scattering which, in addition to particle concentration, is dependent on the size, shape, density, and refractive index of the SPM (Gordon et al, 1980;Kitchen et al, 1982;Kirk, 1983;Baker & Lavelle, 1984;Spinrad, 1986). Of these, size is of critical importance in determining the attenuation efficiency of the SPM [e.g.…”

Section: Resultsmentioning

confidence: 99%

High resolution measurements of sediment resuspension above an accumulation bottom in a stratified lake

Pierson¹,

Weyhenmeyer

1994

Hydrobiologia

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A detailed record of suspended particulate matter (SPM) concentrations in the benthic boundary layer (BBL) 1.5 m above an accumulation bottom and 13.5 m below the surface was obtained from frequent (30 min interval) beam attenuation measurements made with a Sea Tech transmissometer in the main basin of Lake Erken, a moderately deep (mean depth 9 m, maximum depth 2 1 m) dimictic lake in central Sweden. Concentrations of SPM (g m -3, were not as strongly correlated to the beam attenuation coefficient (c, [m-'I), as were concentrations of the inorganic SPM fraction. Apparently, this was caused by large optically inactive organic particles which significantly affected the measurements of SPM, but had little effect on the attenuation of light.When the water column was thermally stratified, SPM concentrations in the BBL showed a seasonal increase which was related to an increase in the thermocline depth. As the epilimnion deepened, there was also a marked increase in the occurrence of rapid and large changes in SPM concentration. After the loss of stratification, the amount of SPM and the temporal variability in its concentration was reduced. Since surface waves could not influence sediment resuspension at the depth of measurement, these data show the importance of internal waves in promoting sediment resuspension in areas of sediment accumulation. The relatively short period in each summer, when the thermocline reaches a sufficient depth to allow for resuspension over accumulation bottoms, can have important consequences for both the redistribution of lake sediments and the internal loading of phosphorus.

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Section: Resultsmentioning

confidence: 99%

High resolution measurements of sediment resuspension above an accumulation bottom in a stratified lake

Pierson¹,

Weyhenmeyer

1994

Hydrobiologia

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“…The slope in this linear relationship depends on the characteristics (size distribution, refractive index, and to a lesser extent shape) of the seston assemblage (see e.g. Baker and Lavelle 1984;Spinrad 1986). This slope changes from place to place, even iF only deep waters are considered (Bishop 1986).…”

Section: Discussionmentioning

confidence: 99%

Light scattering and chlorophyll concentration in case 1 waters: A reexamination

Loisel¹,

Morel²

1998

Limnol. Oceanogr.

309

239

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An analysis is presented based on a large dataset (N = 2,787) made up of recent measurements of the beam attenuation coefficient at 660 nm and of the chlorophyll concentration by using the SeaTech transmissometer and the high-pressure liquid chromatography technique, respectively. This analysis, restricted to case 1 waters, aims at reassessing a previous nonlinear relationship established between the particle scattering coefficient, b,, (very close to the particle attenuation coefficient, c,,), and the chlorophyll concentration, [Chl]. As a first result, nonlinearity is fully confirmed over the whole range of oceanic chlorophyll concentration (about 3 orders of magnitude). Despite more accurate measurements, the scatter in this relationship remains large and is actually comparable to that observed within the old dataset. Rather than establishing a single relationship between c,, (or b,,) and [Chl] for the entire upper water column, the deep layer and the near-surface layer (important for remote-sensing application) have been studied separately. This separation has led to two distinct expressions. A more appropriate parameterization is thus proposed when dealing specifically with, and modeling, the near-surface layer. As a consequence, a modified criterion is also suggested with a view to identifying turbid case 2 waters.Understanding or predicting the propagation of radiant energy within a water body requires that the boundary conditions (at the interface and bottom) and the inherent optical properties (IOP) within the medium are both known or prescribed. Strictly speaking, these properties (IOP) within the medium are both known or prescribed. Strictly speaking, these properties comprise the absorption coefficient, a, and the volume scattering function p(0); the scattering coefficient, b, derives from p(0) by integrating over the whole space, and the attenuation coefficient, c, represents the sum of a and b. These last three coefficients are expressed as m--l. The IOP result from the presence in a water body of colored dissolved organic substances and of scattering as well as absorbing particulate matter.In the open ocean, far from notable terrigenous influence, these optically active materials are locally and permanently Acknowledgments OMEX data were made available with the originators' permission from the EU-MAST OMEX 1 Programme by the British Oceanographic Data center (BODC). The HPLC chlorophyll measurements for this project were undertaken by R. Barlow and R. E C. Mantoura at the Plymouth Laboratory. They are gratefully acknowledged for having made their data available to us. The transmissometer data for the same cruise were calibrated and quality controlled by the BODC. We thank R. Lowry for his help in the control of, and access to, these data. The BOFS data, published on a CD-ROM, were also produced under the BODC, and are duly appreciated here. The HPLC data for the EUMELI and OLIPAC (French JGOFS) cruises and those (unpubl.) for the MlNOS campaign were performed by H. Claustre with the colla...

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“…The range of refractive indices for marine particles relative to seawater are 1 .O l-l. 10 (e.g. Carder et al 1972;Gordon and Brown 1972;Zaneveld et al 1974;Spinrad 1986). The relative refractive index of the gelatin mixture (1.036) nearly matched the refractive index of marine particles, minimizing the effects of light scattering.…”

Section: Microphotometric Determinations -mentioning

confidence: 99%

Microphotometric characterization of phytoplankton and detrital absorption properties in the Sargasso Sea

Iturriaga

Siegel

1989

Limnology & Oceanography

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Microphotometric techniques were used to characterize the spectral absorption properties of individual phytoplankton cells and detrital particles from two sites in the Sargasso Sea during spring 1985. Direct determinations of the absorption efficiency factor, Qa(X), geometric crosssectional area, G, and particle type were made for about 50 individual particles for each water sample analyzed. Large intrasample and intersample variations of Qn(X) spectra for both phytoplankton and detrital particles were observed. For the mesotrophic northern station, mean values of Q=(x) and G for phytoplankton cells showed insignificant vertical variations. For detrital particles, however, the mean geometric cross-sectional area decreased with depth while their mean Q,(X) values increased. For the oligotrophic southern station these same relationships were observed, although more small-scale variability was apparent.The statistical comparison of the mean Q,(X) values with the total particulate absorption coefficient spectrum, a,(X), enabled quantification of the contributions phytoplankton and detrital materials made to a,(X). Results showed that phytoplankton abundances accounted for -X)-70% of the particulate absorption at 440 nm, although instances were observed where phytoplankton cells accounted for > 90% of a,(440 nm). The reconstructed particulate absorption spectrum, dp(X), compared favorably with the total a,(X) indicating that nearly all of the optically relevant absorbing particulate material was sampled with the microphotometric technique.

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A calibration diagram of specific beam attenuation

Cited by 47 publications

References 24 publications

High resolution measurements of sediment resuspension above an accumulation bottom in a stratified lake

High resolution measurements of sediment resuspension above an accumulation bottom in a stratified lake

Light scattering and chlorophyll concentration in case 1 waters: A reexamination

Microphotometric characterization of phytoplankton and detrital absorption properties in the Sargasso Sea

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