The analysis of the optical measurements held in 2008-2014 on a stationary oceanographic platform in coastal waters of the Southern coast of Crimea near the village of Katsiveli is performed. The relationships between the beam attenuation coefficient in eight spectral regions in the wavelength range 416 – 640 nm and the Secchi depth, which varied in the range from 6 to 17.5 m, were established. The spectral distributions of the beam attenuation coefficient at different Secchi depths in coastal waters and in the waters of the deep sea are compared.
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 average radius of suspended organic particles in Atlantic Ocean waters is calculated from the measurements of light scattering phase function. The calculated average sizes of organic particles were compared with the average sizes of phytoplankton cells determined visually using a microscope. The relationship between the size of organic particles and the water transparency is established. It is shown that the sizes of organic particles in oligotrophic waters are larger in comparison with eutrophic waters.
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.
The relations of the beam attenuation coefficient with Secchi disk depth in three parts of spectrum for the Mediterranean Sea waters are established. Beam attenuation coefficient spectra in wavelength range 416-677 nm for waters with Secchi disk values of 9 m and 33 m are retrieved using the system of orthogonal vectors. The shape of spectra in oligotrophic and eutrophic waters of the Black and Mediterranean Seas, Atlantic and Pacific Oceans is compared. The influence of different components of sea water on the variability of spectral shape of beam attenuation coefficient is shown.
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.
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.
Characteristics of light scattering in sea water depend on the concentration and composition of suspended particles. There are a number of methods for solving inverse problems of determination of suspended matter composition from light scattering phase functions. In this work number and mass concentrations of total suspended matter and its specific size fractions in the waters of major currents of North Atlantic tropical region (NATR) are determined using these methods. The concentration and fractional composition of suspended matter differ significantly in the areas of upwelling and downwelling of water. All parameters is higher in the upwelling areas. The characteristics and variability of suspended matter in areas of upwelling and downwelling were found to be similar in Atlantic tropical water, Mediterranean Sea and Indian tropical water.
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.
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