This work precedes the field experiment on Lake Teletskoye, which is scheduled for August 10-20, 2023. The main goal of the work is to get an information of the regional features and seasonal variability of the optically active characteristics of the water upper layer of Lake Teletskoye based on the Level-2 standard products of the OLCI optical scanner.
Reflectance spectra were measured in situ in April-May 2019 in the north-eastern part of the Black Sea, the water color characteristics were calculated. The relationships between effective wavelength of reflectance with other optical characteristics are shown. The absorption, vertical light attenuation, euphotic depth are analyzed taking into account the hydrological parameters of the test polygon. Optical water types of the test polygon were determined.
The paper shows the results of optical measurements carried out during the coccolithophore bloom and the primary bio-optical characteristics obtained. Blooming coccolithophores produce a significant amount of mineral suspension, increasing light scattering and reducing the transparency of water. An increase in the backward scattering leads to an increase in the upwelling radiance and the reflectance coefficient of the sea water. On the base of field and satellite data, the characteristics of coccolithophore bloom in June 2017 in the Black Sea are calculated. A weak relationship between the biological and optical characteristics of the bloom is observed. It is shown that in 2017 the optical properties at the test site were determined not only by coccolithophore suspension, but also by a suspension of terrigenous origin. Suspension concentrations and optical parameters during the bloom are estimated.
The results of the sea water hydro-optical characteristics calculation from satellite and contact data using a modified bio-optical model are presented. The research of the optical characteristics of sea water during the mass growth of coccolithophore is carried out. The estimates of the coccolith and chlorophyll concentration are obtained.
This paper is devoted to the study of the possibilities of restoring the concentrations of chlorophyll-a (Chl-a) and total
suspended matter (TSM) in fresh waterbodies using the images of Sentinel-2 / MSI of the Gorky reservoir as an
example, validated via the high-resolution ground-truth data obtained by fluorescence lidar UFL. This water area in the
period of intense chromaticity of cyanobacteria is distinguished by their completely heterogeneous spatial-temporal
distribution with scales of patchiness from several tens of meters and high temporal variability. For this reason, direct
methods of “spot” measurements in place on water samples in a small part of the reservoir for 3 hours relative to the
satellite’s span do not provide us with reliable and statistically proved data. In this regard, the work proposed an original
method of high-performance sub-satellite synchronous measurements of the brightness of the water column,
concentrations of Chl-a and TSM with a fluorescent lidar onboard a high-speed vessel. This technique is provided with a
spatial (8 m) and a temporary (1 s) resolution. Based on this, 4 independent regional models for the recovery of Chl-a
concentrations, as well as TSM were developed based on in-situ measurements of the brightness of the water surface, or
from Sentinel-2 / MSI images. To ensure the possibility of using satellite images, the analysis of atmospheric correction
algorithms was performed and the best one was determined. The proposed models can be used for regular environmental
monitoring of the Gorky Reservoir according to the in-situ ship measurements of the brightness of the water surface or
from Sentinel-2 / MSI images. When using the proposed methodology for lidar high-performance collection of sub-satellite
data, the developed models can be adapted for limnological monitoring of other freshwater bodies with high
spatial and temporal variability of the optical properties of water.
The scattering characteristics of suspended matter in seawater obtained during combined processing of the field measurements data of the light beam attenuation coefficient and the information from satellite ocean-color scanners are presented. The model estimation of particles size composition is made. Percent of fine fraction of the suspension and its spatial distribution are shown to correlate with seasonal changes in hydrology of measurements polygon.
The results of hydro-optical investigations performed in the spring-summer period of 2017 in the northern part of the Black Sea are considered. It is shown that during the spring survey (22.04.17 - 6.05.17), low concentrations of the total suspended matter were observed in the surface layer. The subsurface maximum in the vertical distributions of the total suspended matter concentrations was not present. In summer (14.06.17 - 4.07.17), due to intensive coccolithophore bloom, a higher content of suspended particles was observed. It was found that in summer the vertical structure of the total suspended matter concentration was characterized by a well-pronounced maximum at the depth close to the depth of vertical temperature and density gradients maxima.
The first results in development of method for satellite monitoring of the bio-optical water properties of Gorky reservoir as an example of an inland freshwater eutrophic water body are presented. The method is based on the semi-analytical algorithm for the Black Sea and uses the data on the reflectance coefficient of the water column, allowing to calculate the concentrations of optically significant substances (phytoplankton pigments, dissolved organic matter and mineral suspended matter). Field measurements of spectral reflectance were carried out in years 2016 – 2017. Spatial variability of reflectance and factors affecting it were analyzed. Reflectance model used in Black Sea algorithm was adapted to biooptical features of the studied water body. Model calculations of pigment concentration were compared with chlorophyll a content data obtained from water samples analyses. The pigment absorption spectra were calculated, showing the spectral features characteristic of photosynthetic pigments. The ways of further research for algorithm development are determined.
The goal of current investigation was a study of seasonal variability of remote sensing reflectance in the lake part of the Gorky reservoir, characterized by intense bloom of blue-green algae. The basis of this study includes the data of ship measurements of remote sensing reflectance, euphotic zone and chlorophyll a and dissolved organic carbon concentrations, performed from May 14, 2018 to August 27, 2018 in 7 points of the reservoir, two of which are located in shallow areas with a slow current (floodplain area), two - in the channel and the remaining three - in estuaries of three inflowing rivers. The spatial and temporal variability of remote sensing reflectance is analyzed, its variations are calculated, vertical profiles of chlorophyll a and dissolved organic carbon are constructed, variations of euphotic depth are determined and correlation between variations of remote sensing reflectance and concentrations of optically active components is established
The methods of determination of concentration and scattering by suspended particles in seawater are compared. The methods considered include gravimetric measurements of the mass concentration of suspended matter, empirical and analytical calculations based on measurements of the light beam attenuation coefficient (BAC) in 4 spectral bands, calculation of backscattering by particles using satellite measurements in the visible spectral range. The data were obtained in two cruises of the R/V "Professor Vodyanitsky" in the deep-water part of the Black Sea in July and October 2016., Spatial distribution of scattering by marine particles according to satellite data is in good agreement with the contact measurements.
A method allowing to obtain estimates of dissolved organic and suspended matter content in Black Sea waters using beam attenuation coefficient (BAC) measurements in two spectral channels is proposed. It makes possible to assess the composition, bio-productivity and ecological state of waters in real time, and to validate the data of satellite scanners. The method is based on retrieval the spectral distribution of BAC by orthogonal functions. Full spectral distribution in range 416 – 677 nm allows to select spectral sites with a dominant contribution of certain substance in BAC and to obtain the content of yellow substance and suspended matter using specially designed optimization technique. Calculated values are in good agreement with the satellite data obtained from MODIS scanner.
This paper proposes a method of remote determination of the suspended matter concentration in seawater on the effective wavelength of upwelling radiation. The system of orthogonal functions is found, allowing to retrieve reflectance of the sea using two measurements in the green part of the visible spectrum. Empirical relations linking the effective wavelength with the concentration of suspended matter for the Black Sea waters are presented and analyzed.
Results of the seawater reflectance coefficient measurements carried out in 2002 – 2014 on the oceanographic platform of Marine Hydrophysical Institute using spectrophotometer designed by authors are discussed. Reflectance is measured in range 390 – 700 nm with 2.5 nm step. The light reflected by sea surface is taken into account by special measurement technique. The processing algorithm allows to calculate the following seawater biooptical characteristics: concentration of phytoplankton pigments, absorption by nonliving organic matter and backscattering by suspended matter, and also to detect presence of auxiliary photosynthetic pigments based on the reconstructed spectrum of phytoplankton absorption. The proposed method makes it possible to carry out operational sub-satellite monitoring of marine environment and to validate the algorithms of remote sensing data processing.
New hydro-optical instruments for sub-pixel scale investigation of satellite features and a new technique to invert water
properties is described. The new semi-analytic algorithm, based on high resolution spectrally continuous remote sensing
reflectance measurements, is proposed for inversion of the optical properties. The algorithm retrieves absorption spectra
of phytoplankton pigment and pigment concentration.
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