Yellow Substance Absorption Research Articles

Estimation of the Absorption Coefficient of a Conservative Yellow Substance from Correlations between Hydrooptical Characteristics (a Version)

A technique for estimation of the absorption coefficient of a conservative yellow substance (CYS) from correlations between hydrooptical parameters is discussed. CYS absorption in different waters is estimated; the spectral selectivity of CYS absorption is determined. The ratio of CYS to total yellow substance absorption in waters with different chlorophyll concentrations is calculated.

Validation of MERIS water quality products in Murchison Bay, Lake Victoria – Preliminary results

As a step forward to validating the retrieval algorithm associated with the MERIS (Medium Resolution Imaging Spectrometer) sensor onboard the European Space Agency's ENVISAT satellite, we compare scaling factors for (442) (pigment absorption coefficient at 442 nm) versus chl-a concentration, and for (scattering coefficient for particles at 440 nm) versus TSM (total suspended matter) concentration, as well as in situ measurements of chl-a and TSM concentrations in Murchison Bay, Lake Victoria, with MERIS level 2 products. Our comparisons show that MERIS chl-a data products underestimate the in situ chl-a concentration by a factor of about 0.6, and that MERIS level 2 products overestimate the in situ TSM concentration and the yellow substance absorption coefficient by a factor of about 2. Application of a local inherent optical property (IOP) scaling factor improves the retrieval provided by MERIS level 2 products. The MERIS level 2 products also underestimate the water-leaving reflectance. These discrepancies between retrievals from MERIS data and in situ measurements are due to the current imperfect atmospheric correction algorithm for inland waters. Therefore, a need arises to develop site-specific bio-optical models and to improve existing MERIS retrieval algorithms.

BIO-OPTICAL CHARACTERISTIC OF CASE-2 COASTAL WATER SUBSTANCES IN INDONESIA COAST

The result of our study in the bio-optical characteristic of mixed water substances or referred as water leaving radiance of chlorophyll-a in case-2 water. Apparent optical properties of chlorophyll-a(chl-a) influence by others water constituents eq.particle backscattering, and yellow substances absorption coefficients. We studied varies Chl-a concentration from 0.001 ug/l,-65.0 ug/l, mixed by suspended particle (SS) concentration from 0.01 mg/l-50.0mg/l, and yellow substances absorption coeficients (ay) from 0.001m - 5.0m. We used the simple radiative transfer equation in seawater method to simulate the Normalized water leaving radiance (NLw)of Chl-a with concentration less than 1 ug/l and less influence from other substances similiar to NLw of pure sea water characteristic. This high reflected at blue band. Otherwise, chl-a concentrations more than 1 ug/l, are similiar to the absorption characteristic of Chl-a with flourescene peak at 680 nm. The Cross characteristic (Hinge point) occurs at 530 nm. Higher SS concentration causes NLw characteristic of Chl-a change, where hinge point moves toward the longer wavelength. Higher yellow substance absorption coeficients cause NLw characteristic of Chl-a has strange behavior. To keep the NLw Chl-a characteristic SS concentration should be no more than 1 mg/l, and ay coeficient no more than 0.01m. Keyword: bio-optical, chlorophyll, the Normalized water leaving radiance.

Parameterization of the inherent optical properties of Murchison Bay, Lake Victoria

Lake Victoria, Africa's largest freshwater lake, suffers greatly from negative changes in biomass of species of fish and also from severe eutrophication. The continuing deterioration of Lake Victoria's ecological functions has great long-term consequences for the ecosystem benefits it provides to the countries bordering its shores. However, knowledge about temporal and spatial variations of optical properties and how they relate to lake constituents is important for a number of reasons such as remote sensing, modeling of underwater light fields, and long-term monitoring of lake waters. Based on statistical analysis of data from optical measurements taken during half a year of weekly cruises in Murchison Bay, Lake Victoria, we present a three-component model for the absorption and a two-component model for the scattering of light in the UV and the visible regions of the solar spectrum along with tests of their ranges of validity. The three-component input to the model for absorption is the chlorophyll-a (Chl-a), total suspended materials concentrations, and yellow substance absorption, while the two-component input to the model for scattering is the Chl-a concentration and total suspended materials.

Application of SeaWiFS data for studying variability of bio-optical characteristics in the Barents, Black and Caspian Seas

Abstract We report the results of our study of spatial and temporal variability of the bio-optical characteristics in the Barents, Black and Caspian seas derived from SeaWiFS data in 1998–2001. The modified bio-optical algorithms were used to derive chlorophyll concentration, particle backscattering, and yellow substance absorption coefficients. The mean monthly distributions of the above characteristics were constructed, and variations of their monthly means in the different regions were analyzed. No significant correlation was found between the variations of chlorophyll concentration in open parts of the basins and the coastal regions with river run-off, suggesting no direct effect of the processes in the coastal zone on bio-productivity in the open parts. Of particular interest is the sharp increase of chlorophyll concentration and particle backscattering found in the Middle and Southern Caspian in July–August 2001, perhaps the result of invasion of the ctenophore, Mnemiopsis leidyi. That event as well as the suspected coccolithophorid bloom in the Middle Barents in July–August needs field evidence.

Remote sensing of ocean colour: Accuracy assessment of an approximate atmospheric correction method

The accuracy of an approximate atmospheric correction method included in a processing scheme for SeaWiFS images, is assessed for atmospheric and water parameters typical of midlatitude European sites with specific reference to the North Adriatic sea. The analysis is carried out using a highly accurate numerical radiative transfer code and results show that the coupling of an approximate atmospheric correction method with vicarious calibration of the space sensor is a valuable solution for the estimate of atmospheric and seawater parameters. Over different simulated measurement conditions, the aerosol optical thickness at 865 nm and the aerosol @ngström exponent are estimated with uncertainties lower than - 5% and - 8% respectively. The uncertainty in water leaving radiance estimate decreases on pigment concentration increase and on yellow substance absorption decrease. For medium-high pigment concentration (i.e. 3.0-10.0 mg m m 3 ) and for a medium yellow substance absorption (i.e. a ys (400 nm) = 0.149 m m 1 ), the water leaving radiance is estimated with an average uncertainty of - 10%. The remote sensing reflectance ratio R 35 is estimated with an average uncertainty ranging between m 5% and +1%.

SeaWiFS data interpretation in a coastal area in the Bay of Biscay

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument, launched onboard the Orbimage 2 satellite, is composed of an optical scanner with eight channels that are used to interpret the ocean colour, and has been operational since September 1997. SeaWiFS data were received by the Dundee Satellite Receiving Station and processed by the Plymouth Marine Laboratory with a slight time-lag. In situ measurements of reflectance, salinity, seston and chlorophyll a were analysed during the Biomet surveys to gain a better knowledge of the dynamics of the Gironde turbid plume during this period. The results showed logarithmic relationships between the SeaWiFS normalized water-leaving radiances (n L w ) at 490 and 555 nm (n L w (490) and n L w (555)), and the suspended particle matter concentrations. The relationship between the n L w (555) radiances and these concentrations is used to map the coastal terrigenous turbidities. But the chlorophyll a concentrations calculated from SeaWiFS are overestimated in the turbid waters. The n L w (490)/n L w (555) ratio decreases with increasing turbidity and with increasing chlorophyll a concentration. To distinguish the chlorophyll a in turbid waters, the n L w (490) radiances are calculated from n L w (555) considering only the effect of terrigenous turbidity. Then, the n L w (490) SeaWiFS image is compared to the calculated n L w (490), to reveal the 'negative' areas caused by the chlorophyll a and yellow substance absorption.

Analysis of a Method to Estimate Chlorophyll-aConcentration from Irradiance Measurements at Varying Depths

A model to estimate chlorophyll-a concentration and yellow substance absorption at 440 nm from irradiance measurements made at varying depths is examined. The derivation of the model, requiring irradiance measurements at three wavebands, is presented and tested on data collected in oligotrophic (with low chlorophyll concentrations) waters and in coastal waters (with both high and low chlorophyll concentrations). The results indicate excellent quantitative agreement with chlorophyll-a concentration and yellow substance absorption measurements. A sensitivity analysis of the model shows it to be highly sensitive to pressure sensor precision, the accuracy of the value used for the mean cosine of the downwelling radiance distribution, and the irradiance sensor measurement error. However, provided that these factors are taken into account, accurate estimates of chlorophyll-a concentrations in case I (phytoplankton-dominated) waters using a single (or multiple) irradiance sensor with three wavebands can be derived. This model can be applied to irradiance data from a variety of deployment methods including profilers, bottom-tethered moorings, subsurface drifters, and towed platforms.

The effects of variability in the inherent optical properties on estimations of chlorophyll a by remote sensing in Swedish freshwaters

During late summer of 1997 measurements were made of the inherent optical properties in Lake Mälaren, Sweden. These included measurements of the total particulate absorption, phytoplankton absorption, yellow substance absorption and total backscattering. Measurements were also made of concentrations known to affect the inherent optical properties; chlorophyll a and suspended particulate organic and inorganic matter. At the same time measurements of underwater radiance reflectance were made. The above measurements were used to better define the relationships between the inherent optical properties and the concentrations affecting them. Correlation analyses were also made in order to study covariation of the concentrations of suspended and dissolved substances in the data set. These relationships were then used to better parameterize a semi-analytical model predicting remote sensing reflectance. Multivariate sensitivity analyses showed that large variations on the Rr(700–710)/Rr(678–685) ratio vs. chlorophyll concentrations could be expected in a heterogeneous environment such as Lake Mälaren. This could lead to large errors in subsequent estimates of chlorophyll concentrations.

Seasonal variability of yellow substance absorption in the surface layer of the Baltic Sea

The value of the yellow substance absorption coefficient in the visible‐light spectrum is a very important characteristic used in the optical classification of seawater. This quantity also needs to be included in algorithms for the remote detection of optically active seawater constituents. An extensive database of measurements of optical parameters has been collected during a series of cruises since 1993 in different water masses of the southern Baltic. The yellow substance absorption coefficient at a wavelength of 400 nm was measured and the yellow substance absorption spectrum slope coefficient calculated. The statistical distribution of values of these parameters in the three various water masses (bay waters, coastal, and open seawater) is presented. The seasonal variability of both parameters in the three regions is analyzed. Results are discussed and compared with the published record of yellow substance absorption properties and variability patterns of other optical parameters in the southern Baltic and other marine basins.

Inversion of Reflectance Spectra of Nonchlorophyllous Turbid Coastal Waters

This article deals with the inversion of reflectance spectra measured in the Rhône River mouth area during a flood event in terms of parameters characterizing the turbid water components. The optically active constituents considered are the total suspended matter, mainly composed of sediment, of known concentration ranging from 3.7 mg L −1 to 234 mg L −1, and yellow substance. A simple reflectance model is presented. Scattering is treated by Mie theory applied to a collection of particles of real refractive index m p and obeying a Junge size distribution law. A sensitivity study performed on the model shows that both concentration and refractive index and both cutoff particle diameters of the Junge size distribution law cannot be accurately determined from a given reflectance spectrum. Two model parameters, among a total of six, are estimated from model inversion: m p and a parameter characterizing the yellow substance absorption spectrum, a y0=a y (440 nm). The derived values are realistic as compared to the values that can be found in literature. Other combinations of parameters could be determined by inversion but measurement of m p and a y0 from reflectance spectra already has interesting applications in a satellite remote sensing perspective. Increasing the number of parameters of the model is feasable, but much work is needed to envisage the inverse problem.

Optical measurements in the North Sea-Baltic Sea transition zone. III. Statistical analysis of bio-optical data from the Eastern North Sea, the Skagerrak and the Kattegat

Bio-optical measurements (downward and upward spectral irradiance, beam attenuation, yellow substance absorption, Chi- a, CTD and nutrients) were gathered in the Eastern North Sea, the Skagerrak and the Kattegat during nine cruises over the years 1990–1992. The light data were used to describe the spatial and seasonal variations of the underwater light climate in the region and to develop ocean color models for estimation of water quality parameters. Empirical relations were established between the vertical attenuation coefficients K d( λ) and K d(488) which showed good agreement with the results obtained by Austin and Petzold ( Optical Engineering, 25, 471–479, 1986). Local ocean color algorithms for estimating z q(10%), the depth of the 10% downward quanta irradiance level and K d(488) were derived and showed fair agreement with previously established expressions from the literature. irradiance reflectance measurements were subjected to principal component analysis that showed that more than 95% of the variance in the reflectance spectra for Danish coastal waters was explained by the first two eigenvectors. The model by Kirk ( Limnology & Oceanography, 29, 350–356, 1984) was used to determine the inherent optical properties a (light absorption) and b (light scattering) from irradiance and reflectance measurements. The results were in accordance with the few historic measurements that exist from the area though the scattering estimates were slightly higher than previous measurements. Concentrations of Chl- a and suspended matter and yellow substance absorption were estimated by the inverse method of Jain and Miller ( Applied Optics, 15, 886–890, 1976). The results showed fair agreement with in situ measurements and the model tended to overestimate the concentrations of suspended matter and yellow substance absorption.

Optical measurements in the North Sea-Baltic Sea transition zone. I. On the origin of the deep water in the Kattegat

In the North Sea-Baltic Sea region, several studies have shown that yellow substance can be treated as a quasi-conservative parameter that is negatively correlated with salinity. A review of more than 5000 historic and recently gathered yellow substance absorption and salinity measurements from the transition zone between the North Sea and the Baltic Sea have been analyzed for the purpose of water mass identification. Salinity-yellow substance scatter plots show that three water masses can be identified in the area: (1) North Sea water (high salinity, low yellow substance content); (2) Baltic Sea water (low salinity, intermediate-high yellow substance content); and (3) German Bight/Southern North Sea water (intermediate-high salinity, high yellow substance content). Based on the volume flow estimates used in a two-layer box-model of the Kattegat (Jørgensen, Continental Shelf Research, 12, 103–114, 1992) and conservation of yellow substance, it is argued that the long-term average composition of the bottom layer inflow to the Kattegat from the Skagerrak consists of about 90% North Sea/Atlantic water and 10% German Bight/Southern North Sea water. The German Bight content estimate is substantially lower than the ones given in earlier studies (50–67%) and implies that the Jutland Coastal Current only has a small impact on the water quality of the Kattegat.

Local algorithms using SeaWiFS data for the retrieval of phytoplankton, pigments, suspended sediment, and yellow substance in coastal waters

Algorithms that use the SeaWiFS radiometer band reflectance data for the retrieval of phytoplankton pigment concentration, suspended sediment concentration, and yellow substance absorption in coastal water are set up by a computation based on a three-component model of sea color. The varying coastal environment is characterized by a site-specific correlation among the three parameters, subjected to large spatial and temporal fluctuations. The computation is performed with respect to the summer situation of the Gulf of Naples (Mediterranean Sea). The sensitivity of the retrieval of each parameter to variations in the concentration of the two other quantities is investigated by numerical simulations. The sensitivity to the variability of the absorption and scattering properties of phytoplankton and suspended sediment is analyzed, as well as the error induced by the uncertainty of the remote-sensing data. The algorithms's performance is satisfactorily tested on sets of SeaWiFS band reflectances randomly generated within wide water composition ranges. Although the results obtained cannot be generalized and require experimental validation, the series of tests performed suggests that the proposed algorithms, with numerical constants adjusted to the local conditions, can be effectively applied to several types of coastal environment.

Evaluation of the influence of yellow substance absorption on the remote sensing of water quality in the Gulf of Naples: a case study

Abstract The yellow substance absorption in the coastal waters of the Gulf of Naples was measured by a method combining beam transmission and induced fluorescence measurements. A water optical model specific to that test area, derived from experimentation carried out in situ has been used to evaluate the impact of the measured yellow substance absorption on the remote sensing of water quality parameters, such as chlorophyll-like pigment and total suspended sediment concentrations.

Influence of pH and heavy metals in the determination of yellow substance in estuarine areas

Absorption and fluorescence changes of yellow substance in the presence of pH and heavy metal excursions were examined for water samples collected in the deltaic area of the Po river (Sacca di Goro) and for solutions of natural humic and fulvic acids isolated from lake waters and podsol soils, respectively. An important effect on the light absorption and induced fluorescence was found for the pH variations that occur during the mixing of fresh and saline waters. For this reason, correction factors are required to normalize the absorption and fluorescence values for use in remote-sensing water quality of estuarine/coastal areas. If the factor is chosen to equal 1 at pH 7, the percentage error in the uncorrected estimate of the yellow substance absorption varies from 0% to 18% with a mean of 5% relative to a set of samples collected in Sacca di Goro. Among the heavy metals Cu 2+, Pb 2+, and Cd 2+ present as pollutants in trace levels in estuarine environments, only Cu 2+ and Pb 2+ in high concentration (> 15 μg/L for Pb and > 10 μg/L for Cu) have been found to depress the induced fluorescence response of water samples containing yellow substance and humic acid solutions.

The effect of dissolved “yellow substance” on the quantitative retrieval of chlorophyll and total suspended sediment concentrations from remote measurements of water colour

Abstract The effect of the dissolved “yellow substance” on the quantitative retrieval of chlorophyll and suspended sediment concentrations from remote measurements of water colour, has been investigated through a sensitivity analysis applied to theoretical simulations. Two different models for yellow substance absorption, derived from experimental observations, have been used in the computation. The results obtained showed important effects, leading to the conclusion that the presence of yellow substance must be taken into careful account in the process of inferring water composition from its colour signature.