The article considers the period of influence of the tropical storm Ophelia on the optical characteristics obtained for the Black Sea region. Over the Black Sea on 18.10.2017-19.10.2017 the transfer of air flows from the northwest was recorded, which contained particles like dust aerosol from the Sahara desert, and smoke particles from fires from the Iberian Peninsula. Analysis of the dust-smoke combined type aerosol influence on the results of satellite spectral brightness coefficient over the Black Sea water area according to MODIS and VIIRS measurements showed an underestimation of the values of Rrs(λ) in the short-wave region compared to in situ data obtained at the western Black Sea stations of the AERONET network.
The paper is concerned to the problem to determine the light absorption in seawater by measuring properties of the light field. To highlight the multiple light scattering effects in a water body, the radiation transfer equation (RTE) in the depth regime is analyzed. The scattering phase function of the light by suspended particles was derived from the field VSF data (BLACK SEA BIO-OPT Oceanographic Campaign 31.08 – 16.09.2012). One-parametrical model of phase function accounted only variations in the proportion of molecular scattering. To calculate the deep water angular radiation distribution a new iterative procedure was applied. It is shown that in comparison with formulas of the two-flow approximation the characteristics of the light field exhibit greater non-linearity depending on the Gordon parameters.
The problem of consistency of the thermodynamic approach to predict the light scattering in water over a wide angular range is discussed. It is proposed that not only particles but impurities could significantly affect on the shape and the magnitude of VSF of water. To prove this approach the light scattering measurements in filtered waters and its salt solutions were carried out. On the base of the experimental data, it is concluded that the chemical composition of impurities plays a significant role on spectral and angular shape of VSF.
In turbid coastal waters the fluorescence by yellow substance and by chlorophyll affect on the light fields. It would be quit important to take into account the effects of incoherent light scattering more precisely. In this paper, the equation of transfer is written in vector form, in which the spectral matrix of incoherent light scattering is included. The spectral matrices of the reflectance and of the transmittance for a plane-parallel layer are introduced. An analytical solution of the equation for a single and two-fold scattering is written. To get numerical solution a matrix operator method based on the “interaction” principle is proposed. The method is intended for numerical simulation of the light fields in the vertically non-uniform seas illuminated by daylight.
The paper is devoted to theoretical aspects of the light scattering of water that does not contain suspended particles. To be consistent with current physical point of view the water as far as any liquid is regarded as a complex unstable nonergodic media. It was proposed that at fixed time the water as a condensed medium had global inhomogeneities similar to linear and planar defects in a solid. Anticipated own global inhomogeneities of water have been approximated by the system randomly distributed spherical clusters filling the entire water bulk. An analytical expression for the single scattered light has been derived. The formula simultaneously describes both the high anisotropy of light scattering and the high degree of polarization which one close to those for molecular scattering. It is shown that at general angles there is a qualitative coincidence with the two-component Kopelevich’s model for the light scattering by marine particles. On the contrary towards to forwards angles the spectral law becomes much more prominent i.e. it corresponds to results for model of optically soft particles.
The problem of optical constant of seawater to in situ measured light fields in the clear natural waters is under discussion. A precise radiative transfer prediction for the water reflectance demonstrates significant discrepancy in comparison to the field data. It was shown that to meet agreement between the empirical and theoretical reflectance values it would be necessary to increase the backscattering. On the contrary, the interpretation of diffuse attenuation coefficients for downward irradiance tends to underestimate the light absorption in the water. A conception of own water heterogeneity is proposed. This enables to explain the most of inconsistencies.
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.
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