Relationship between the depth of visibility of Secchi disk and biooptical characteristics of the Black-Sea waters

We present the parameters of empirical relationships between the depth of visibility of Secchi disk and optical and biological characteristics of the Black-Sea surface waters. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Summer dynamics of phytoplankton pigments and its correlation with the optical parameters of shelf waters in the Black Sea (2001–2002)

We study the space and time variations of the concentration of chlorophyll in the Black-Sea coastal zone (near Katsiveli) in summer 2001–2002. Typical vertical profiles of the pigments are presented. The relations between the concentration of chlorophyll and the optical parameters of seawater (including the Secchi depth, sea reflectance, effective wavelength of the upwelling radiation, and the vertical attenuation coefficient of light) are analyzed. The equations for the biological parameters of seawater and its optical characteristics are presented. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 36–51, May–June, 2006.     

Albedo of clouds and radiation conditions in the oceans

On the basis of the satellite and ship data of many-year observations, we parametrize the albedo of the ocean-atmosphere system both for the conditions of “fair weather” and for the maximum and climatic optical thicknesses of oceanic clouds. These results are used to develop a procedure of practically exact reconstruction of the monthly average fluxes of integral solar radiation and the radiation budget over the ice-free surface of the oceans according to the data of satellite measurements of albedo (Nimbus NOAA satellite, 1974–1983) for arbitrary conditions of transparency of the atmosphere and cloudiness. We determine the current and climatic monthly average values and the characteristics of interannual variability of all components of the radiation mode of the ocean-atmosphere system with a spatial resolution of 500×500 km. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Formation of a circulation in the quasiisopycnic model of the Black Sea taking into account the stochastic nature of the wind stress

We discuss the results of numerical experiments carried out within the framework of a new version of the quasiisopycnic model of the Black Sea [1, 2]. We take into account the stochasticity of the wind stress, vertical shift of the flow velocity in the upper quasihomogeneous layer, and diapycnic mixing. We generalize the procedure of “convective adjustment,” which enables us to consider the propagation and transformation of waters of the Sea of Marmara. It is shown that the consideration of these factors enables one to determine the structure and seasonal variability of hydrothermodynamic fields in the sea more correctly. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

A numerical model for the evaluation of the depth of penetration of two-dimensional turbulent convection

For a one type of temperature turbulent convection observed in the ocean, i.e., for the two-dimensional roller-type convection, we propose a model intended for the evaluation of the intensity and depth of penetration of convective motions as functions of a given heat flow from the sea surface and the temperature gradient in the thermocline. This model is based on the methods of the theory of turbulent jets and experimental data on the vertical distribution of temperature in the course of convection. The comparison of the calculated dimensionless values of the depth of penetration of the thermocline in autumn and winter shows a good qualitative agreement with the data ofin situ measurements. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Seasonal and spatial variability of the content of suspended organic substances in the active layer of the Black Sea

On the basis of the generalized data of multiannual observations (1985–1994), we analyze the seasonal variability of the vertical and spatial distributions and composition (C_sos, N_sos, C_sos/cha, and C/N) of suspended organic substances (SOS) in the shelf zone and in the upper active layer of the abyssal part of the Black Sea. The results of our analysis enable us to conclude that only a narrow coastal band of the shelf in the northwest and west parts of the sea suffers to an extremely pronounced anthropogenic impact, which manifests itself in a significant increase in the mass of suspended organic substances. The formation of new organic substances and, hence, the mass of suspended organic substances in these regions attain the level of eutrophic waters in the late-spring and summer periods. In the open-sea region, the anthropogenic impact is less pronounced and the spatial distribution of suspended organic substances is determined by the general dynamics of waters and the intensity of phytoplankton production. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Optical properties of the red tide in Isahaya Bay,southwestern Japan: Influence of chlorophyll a concentration

Remote sensing reflectance [R _rs(λ)] and absorption coefficients of red tides were measured in Isahaya Bay, southwestern Japan, to investigate differences in the optical properties of red tide and non-red tide waters. We defined colored areas of the sea surface, visualized from shipboard, as “red tides”. Peaks of the R _rs(λ) spectra of non-red tide waters were at 565 nm, while those of red tides shifted to longer wavelengths (589 nm). The spectral shape of R _rs(λ) was close to that of the reciprocal of the total absorption coefficient [1/a(λ)], implying that the R _rs(λ) peak is determined by absorption. Absorption coefficients of phytoplankton [a _ph(λ)], non-pigment particles and colored dissolved organic matter increased with increasing chlorophyll a concentration (Chl a), and those coefficients were correlated with Chl a for both red tide and non-red tide waters. Using these relationships between absorption coefficients and Chl a, variation in the spectrum of 1/a(λ) as a function of Chl a was calculated. The peak of 1/a(λ) shifted to longer wavelengths with increasing Chl a. Furthermore, the relative contribution of a _ph(λ) to the total absorption in red tide water was significantly higher than in non-red tide water in the wavelength range 550–600 nm, including the peak. Our results show that the variation of a _ph(λ) with Chl a dominates the behavior of the R _rs(λ) peak, and utilization of R _rs(λ) peaks at 589 and 565 nm may be useful to discriminate between red tide and non-red tide waters by remote sensing.     

A model of the evolution of vertical thermohaline inhomogeneities of an oceanic thermocline taking into account the effects of double diffusion

We construct a numerical model of the evolution of the structure of an oceanic thermocline in the presence of “salt-finger” convection. The model explains the formation of a piecewise homogeneous vertical structure of the temperature and salinity fields in the ocean. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

A spectral model of underwater irradiance in the Black Sea

We develop a semiempirical spectral model of penetrating irradiance taking into account the biooptical characteristics of the Black Sea. The evaluation of the contributions of the principal optically active components to the total absorption of light in the sea shows that, in the short-wave range (400–500 nm), light is mainly absorbed by the dissolved organic matter (41–77%). The contribution of phytoplankton to the total absorption attains its maximum values (26–37%) in the abyssal part of the sea in the period of spring blooming of diatoms. In the coastal waters, the absorption of light by suspended nonalgae particles in summer is almost twice as intense (20–30%) as in the open sea (8–13%). The analysis of the sensitivity of our model shows that the absorption of light by dissolved organic matter is more significant for the estimation of the photosynthetically active radiation in the Black Sea than the concentration of pigments and backscattering of light by suspended particles. The comparison of the results of model computations with the data of measurements of the underwater irradiance reveals high accuracy of the proposed model.     

Estimate of water inherent optical properties from Secchi depth

This paper suggests a new version of the Secchi disk theory which shows a connection between Secchi depth measurements and inherent optical properties (IOP) of water such as the extinction coefficient, the single scattering albedo, and the backscattering coefficient. Ways around Preisendorfer’s objection to using measurements of the Secchi depth for determining the IOP are proposed. This theory is compared with a marine experiment and its accuracy under different conditions is estimated.     

Analysis of the possibilities of aGALS-3 hydrophysical towed complex

We describe the characteristics of a towed complex used for measurements in the upper layer of the ocean under the conditions of periodic deepening and lifting (scanning) of a carrier with sensors connected with the ship by a weight-carrying cable of constant lengt. For a maximum scanning range of 0–200 m and a towing speed of up to 12 knots, the measurements were performed every 1.5–2.0 km. The minimum vertical scale of recorded temperature and conductivity inhomogeneities is 0.05–0.08 m. We present the results of measurements carried out by the towed complex in a section of the frontal zone in the north-east part of the Tropical Atlantic. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Hydrooptical Characteristics of Subsatellite Test Ranges in the Mediterranean and Black Seas According to the Data of Investigations Performed by the R/V Gorizont in 1998

Hydrooptical investigations were performed for three subsatellite test ranges located near the Rhodes Island in the Levant Sea, near Dardanelles in the north part of the Aegean Sea, and near the Crimean Peninsula in the northwest part of the Black Sea. In the course of observations, we measured the beam attenuation coefficient, the depth of visibility of the Secchi disk, and the color of water. These data are used to characterize the space and time variability of the optical properties of water in the investigated regions.     

Variations in a set of optical and hydrologic parameters of the Atlantic surface waters

A complex analysis of the hydrooptical and dynamic parameters of the Atlantic surface waters has been made on the basis of experimental data. It is shown that the structural properties of the distribution of the basic hydrooptical parameters—such as the optical water-type index m (according to Prof. V.N. Pelevin’s classification), surface-water transparency (the depth of white-disc visibility Z _σ), circulation parameter (the dynamic height D at a depth of 100 m), and flow fields—are similar. On the basis of this, in the authors’ previous studies, relations between these parameters were obtained and the empirical dependences Z _σ(m) and D(m) were found. These dependences and the earlier obtained relationships between biological and optical parameters-chlorophyll concentrations c _p (m) and the indices of light attenuation by a soluted “yellow substance” a _ys (m) and suspended matter a _sm (m)—were combined and formed the basis of a method to determine them at any point of the open ocean from the measured (also remotely) parameter m. The results of the measurements of hydro-optical parameters (which were taken as part of the Meridian project from the Akademik Ioffe during its 14th voyage in October-November 2003) supported the validity of calculations of variations in the five parameters indicated above from the values of the index m. Thus, the efficiency of the developed rapid method of estimating variations in a set of parameters according to the optical water-type index m was demonstrated. In addition, the water’s “health” index H _w proposed by Pelevin in 2002, which is equal to the ratio between chlorophyll concentrations and soluted yellow substance, proved to be efficient at identifying the ecological state of the near-surface waters.     

Evaluation of the influence of surface films on short wind waves and the characteristics of the boundary layer of the atmosphere

With the help of a combined model of wind and waves, we study the influence of films of surfactants on the spectrum of short wind waves and the parameters of the lowest layer of the atmosphere. It is shown that the films of surfactants decrease the roughness of the sea surface as a result of suppression of short wind waves, which decreases the coefficient of resistance of the sea surface and the coefficient of turbulent heat exchange. The maximum influence of films on the exchange coefficients is attained forU∼10 m/s. In this case, the relative decrements of the coefficients of resistance and turbulent heat exchange are equal to 15 and 9%, respectively. Translated by Peter V. Malyshev and Dmitry V. Malyshev UDC 551.46     

Turbulence in the ocean: Development of investigations, evolution of ideas, and prospects

We present an analytic survey of a series of works devoted to the direct methods for the investigation of turbulence in natural basins originated under the guidance of A. G. Kolesnikov in the 50s. We describe the principal results of the early stage which formed the basis for future investigations. The main scientific directions of the latest period are also considered from the viewpoint of the development of Kolesnikov's ideas: investigation of the processes of generation and energy supply of small-scale turbulence, relationship between turbulence and the fine vertical structure and internal waves, and the mechanisms of vertical turbulent exchange in the ocean. A model of vertical exchange under the conditions of intermittent “source” turbulence is distinguished. We also discuss the directions of development and prospects of the investigation of turbulence. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Convection of salt fingers in theC-SALT region

We study possible mechanisms of mixing in the northwest part of the Tropical Atlantic (C-SALT) and show that homogeneous layers in the staircase structure can be observed across the entire frontal zone of the North Equatorial Countercurrent. In the central region of the frontal zone, one may observe horizontal motions of the upper parts of quasihomogeneous layers with respect to their lower parts and an essential role in the exchange processes is played by turbulence. The peripheral regions of the frontal zone are characterized by the presence of horizontal advection and isopycnic mixing. Far from the frontal interface, the principal contribution to the exchange processes is made by double diffusion. We demonstrate that, for the analysis of the vertical buoyancy fluxes caused by salt fingers, one can use both the Stern relation and the “law of 4/3”. Translated by Peter V. Malyshev and Dmitry V. Malyshev.     

Reconstruction of the seasonal climate of the Black Sea on the basis of available hydrological data

We analyze the seasonal variability of the climatic hydrophysical fields of the Black Sea reporduced in three numerical experiments carried out according to the model of circulation. The numerical predictions are performed for a period of 12.5 yr on the basis of the hydrological data accumulated in 1983–1995. The monthly average climatic fields of the current speed are reconstructed according to the data on the climatic fields of temperature and salinity by the method of hydrodynamic adaptation (standard). It is shown that, in prognostic calculations, the seasonal variability of temperature and salinity is qualitatively close to the “standard” dependence. At the same time, the quantitative difference between the climatic behavior of the model and the standard dependence may be significant. The annual cycle of the currents is characterized by the intensification of the Main Black-Sea Current in winter. The structure of the hydrophysical fields of the sea in the model becomes much more realistic if it is based on the actual hydrological data. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Spectrophotometric and iodometric methods for the detection of hydrogen sulfide in the Black Sea: Comparison of the results of analysis

We discuss the results of analysis of published data and field and laboratory investigations aimed at the solution of the problem of comparabilityof the results of detection of hydrogen sulfide in the Black Sea by spectrophotometric and iodometric methods. We show that the reproducibility of the results of spectrophotometric analysis is higher than hat of the iodometric method only in the case where the content of sulfide in a sample is less than 10–30 μMl⁻¹. When larger concentrations are involved, the traditional iodometric analysis proves to be the most precise and reliable method for the detection of hydrogen sulfide in the Black-Sea waters. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Space and time variability of the parameters of ecological economical systems

We propose a procedure for the construction of prognostic models of ecological economical systems based on the combination of dynamical models of natural environments with conceptual models of natural economical complexes. This procedure enables one to study space and time distributions of ecological and economical parameters parallel with the fields of physical, chemical, biological, and other characteristics of the natural environment. With the help of a conceptual model of the “sea-land” natural economical complex in the Sea of Azov used asan example, we show that it is possible to relate the dynamics of the concentrations of pollutants and biological resources of the sea with the economical profitability of fishery and the rates of ecological fines controlling the costs of production. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Trapped bottom topographic waves over the inclined bottom

In the Boussinesq approximation, we study baroclinic topographic waves trapped by the flat meridional slope. The existence of these waves is explained by stratification, inclined bottom, and Earth's rotation. We deduce the evolutionary equation for the square of the envelope of a narrow-band wave packet of trapped waves. In the second order of smallness relative to the wave amplitude, we find the mean fields of velocity and density induced by the packet. It is shown that, in the limiting case of weakly nonlinear plane waves, the induced current is zonal. In the Northern hemisphere, depending on the slope of the bottom γ₁, the sign of the phase velocity σ/k (k is the zonal wave number) is either always positive (for γ₁>γ_1cr) or always negative (for γ₁<γ_1cr). If we neglect the vertical component of the Coriolis acceleration, then γ_1cr=0. Translated by Peter V. Malyshev and Dmitry V. Malyshev