A simple method of spatio-temporal localization of the ground-based aerosol sources, using the results of back trajectory analysis (BTA), is described in the paper. The key parameter of the method is the derivative of pressure by time (P't). A positive value corresponds to an upward air flow, negative one corresponds to a downward air flow. Two conditions are needed to satisfy in order to identify the ground source of aerosols in a specific location of the Earth: air mass is in the surface layer (below 700 mbar); P't > 20 mbar/hour, that is equivalent to an upstream flow with a velocity of several cm/s or more. Latter condition corresponds to the mesoscale vertical movements of the same signs of the air volumes with the horizontal dimensions of the order of 10–100 km. The value of 20 mbar/h is based on the analysis of the long-term (2007–2012) array of data of BTA for AERONET station Sevastopol. We also tried to take into account the process of «aerosol removing with precipitation». The criterion for a downward air flow is: P't < −20 mbar/h. If this condition is satisfied, it means that the atmospheric layer does not contain aerosol captured earlier by upstream flows from Earth’s surface. Method validation was carried out using data of Sevastopol station (network AERONET) and satellite optical scanner MODIS. The relation between the area of origin and specific aerosol optical properties was observed at Sevastopol station (network AERONET). The featureы of its impact on the results of the standard atmospheric correction of MODIS measurements have been shown on the example of dust aerosol from two arid zones. The results of this study will be useful to specialists, solving the problem of atmospheric correction of measurements of upward radiance on top of the atmosphere in visible range of spectrum above the water surface.

This paper examines the reasons of hydrodynamic instability of Mast Hoisting Gears that are related to interactions of bending and torsional oscillations of a structure in the hydraulic flow. A mast hoisting gear loaded by hydrodynamic forces is a non-conservative (self-oscillating) system. Unsteady modes of motion are possible for such systems under certain combinations of the system parameters and speed of external flow (critical speed). Naturally, this brings up the question of the possibility of occurrence of such an event within the limits of operational speeds of real structures and development of respective calculation methods. The paper presents equations of bending-torsion oscillations of Mast Hoisting Gears as a rod of variable cross-section working in bending and in torsion in the hydraulic flow. A calculation algorithm of a critical speed of Mast Hoisting Gear bending-torsion flutter is suggested based on the complex amplitude method. The algorithm extensively uses the capabilities of state-of-the-art computing aids. Taking as an example the actual Mast Hoisting Gear design, complex eigenvalues are determined that allows to assess the Mast Hoisting Gear stability in the hydraulic flow at the specified speed of an underwater object and to determine natural frequencies of oscillations using this algorithm. This paper gives recommendations allowing increase the structure stability threshold to bending-torsion flutter.

The modulation transfer function of an amplitude modulated signal propagating through seawater is explored. This function describes the dependence of the signal modulation depth on modulation frequency in the propagation process and is the most important factor determining the optical communication quality. The experimental data received as the laboratory simulation of the radiation transfer through seawaters are compared to results of the theoretical studies. The deployed experimental set-up and media simulating the optical characteristics of seawaters are briefly introduced. Theoretical studies are performed in the framework of the multi-component approach along with the small-angle diffusion approximation of the radiative transfer theory using the software CLIW (Communication with Light In Water) implementing this theory. It is shown that the theoretical approach deployed in the CLIW software ensures the satisfactorily description of the propagating amplitude-modulated signal characteristics and estimation of the parameters of a communication channel in seawaters at sufficiently large distances from the optical source. Beside it is noted there is a need to know the media phase function in a fairly wide range of angles for such comparisons. In this work the effect theoretically predicted in 1971 was experimentally confirmed for the first time. This effect consists in the fact that the asymptotic deep mode for the alternative component of the signal can take place only for a certain range of frequency modulation values. The maximum angular intensity distribution for the alternative component of the signal takes place not in the «forward» direction but at a certain observation angle q > 0°. The position of this maximum depends on the frequency modulation and optical characteristics of medium.

The estimation of the waveguide transfer function is required to measure the mentioned noise level of marine objects with a given accuracy and to perform matched filtering of the received signals for assessment of the depth and distance to the object in passive mode. The paper analyzes and discusses the methodology developed by the use of various technical means for acoustic calibration of local zones of shallow water and getting adequate models of ground with parameter estimation in the areas of the receiving antenna, in the area of traffic or towing of the source, as well as along the path of signals propagation. The information received, together with an evaluation of the vertical distribution of sound velocity allows us to give an analytical description of the waveguide transfer function according to the distance, the operating frequency, the depth of the transmitter and receiver. The results of comparison of different methods and of experimental estimation of the model parameters of the ground in homogeneous and inhomogeneous waveguides are presented. The advantage of applying the Wigner method to estimate the parameters of normal waves is proved. A comparison of different models is performed, their adequacy is estimated by calculating the correlation ratio between the experimental and theoretical dependences of sound field, as well as by assessing the noise with absolutely calibrated source noise which was known. Practical recommendations are given, the methods of the interference field structure prediction and of providing the consistent estimates of the noise of the source are justified.

Analytical description of traditional method of «optimal frequencies» for estimation of distance to noise emitting object in the sea is received. Analysis of method error of distance estimation has allowed to receive expression for the error component caused by lack of data about inclination of broadband signal spectrum. It is shown that at unknown inclination of signal spectrum, limiting error of distance estimation can be taken as about six percent. It is shown that along with traditional realization of the method, based on choice of the central frequency of broadband filter, advanced realization of distance estimation method with simultaneous estimation of inclination of broadband signal spectrum by optimization of the type of filter amplitude-frequency characteristic is possible. Analysis of received function extremum has shown its weakly expressed pattern. Practical importance of each variant by criterion of minimum error of distance estimation can be defined after additional theoretical and experimental research directed at revealing and comparison of methods noise stability depending on signal source parameters, parameters of signal propagation medium and parameters of sonar receiving subsystem.

The main features of seasonal and inter-annual variations of bio-optical characteristics in the surface layer of the Barents, White, Black and Caspian Seas, according to a new issue of e-atlas “Bio-optical characteristics of the Russian seas from satellite ocean color data” (http://optics. ocean.ru) are discussed. The bio-optical parameters in the Atlas were computed by means of the regional algorithms, derived from in situ measured data in given regions; they provided much better results than the NASA standard algorithms (http://oceancolor.gsfc.nasa.gov). The article includes Introduction, Results and Discussion, Conclusion and References. The Introduction gives a brief information about the new issue as compared with the previous ones. Atlas’2013 presents the biooptical characteristics, calculated from data of satellite scanners SeaWiFS and MODIS-Aqua from 1998 to 2012; the color maps of their mean monthly distributions, diagrams and tables demonstrating their seasonal and inter-annual variability are given. As examples, the coccolithophore blooms in the Barents and Black Seas and the seasonal changes of chlorophyll concentration (Chl) and the particle backscattering (bbp) in the Dvina Bay and the central part of the White Sea under the influence of Dvina river runoff are considered. It is noted that the highest bbp values, as compared with the other regions, were observed in the shallow Northern Caspian owing to the intense river runoff from Volga and the stirring of bottom sediment by wind mixing. Interestingly, that the mean values of Chl and bbp in 2012 were higher than their average climatic values over 1998−2011 in eight from ten regions under consideration.

Spatial distribution of dissolved organic matter and chlorophyll-a fluorescence intensity in the Western Black Sea is studied in the article. The measurements were carried out during a number of international bio-optical cruises. Their routes passed through the open sea and the coastal areas, including areas exposed to the river runoff of the Danube. The measurements of the spatial distribution of fluorescence intensity were carried out with use of a custom developed flow-through fluorometer with super flux LEDs. UV (373 nm) and green (521 nm) light is used to excite fluorescence in the flow-through fluorometer. A two-channel laser spectrometer is utilized for the purpose of calibration of the obtained data. The calibration allows for determining of the chlorophyll-a fluorescence intensity taking into account the contribution of the DOM fluorescence. The spectrometer operates on samples of seawater. High spatial variability was registered in coastal areas, especially close to the Danube estuary. In open-sea areas the distribution of the measured sea water characteristics was quasi-uniform. Vertical profiles of the fluorescence intensity show high variability in the whole surveyed water area. Daily changeability of the fluorescence intensity was registered in the surface layer of seawater.

We present the investigation of uranium(VI) complexes using steady-state and time-resolved laser induced fluorescence spectroscopy. Dependences of uranyl complexes’ photophysical parameters on local environmental parameters (i. e. coordination or anion ligands number in the first coordination sphere), global environmental parameters (solution ionic strength, temperature, humic substances concentration) and excitation radiation intensity are investigated. We demonstrate that the dependence of integral luminescence of uranium(VI) complexes on the total concentration of fluoride-anion in solution is not monotonous. Our investigation of uranium solutions with humic and fulvic acids demonstrates that the process of uranyl luminescence quenching is a static quenching process and it can be described by Stern-Volmer equation. We show that the process of uranyl excited state deactivation depends on the laser excitation intensity. This dependence could be explained with diffusion-limited excited state annihilation, which is a process involving interaction of excited ions. Presented results provide a better understanding of uranium(VI) complexes luminescent properties which should be taken into account in the fluorescent diagnostic tools development.

A new method for retrieving the slopes of a rough water surface from its imaging under the conditions of daylight illumination and clear cloudless sky is proposed. The traditional method uses the approximation, within the framework of which the distribution of the sky radiance can be considered linear. The new method uses more realistic approximation, in which the distribution of the sky radiance is not linear but has an axial symmetry with respect to the Sun direction. To implement any of these methods, one should not only image the water surface but also know the distribution of the sky radiance in the "mirror" area of the celestial sphere. An important part of the new algorithm is the operation of retrieving the second component of the surface slope vector by the component directly determined by spatial image processing. Mathematically, this operation is nothing but a problem of finding the gradient of a smooth function of two variables by one of its components. In this paper, this problem is solved by means of the Fourier transform. An improved (from the viewpoint of the computing speed) version of the algorithm and a formula for calculating the error are given.

In this work we examine new approaches for measurment of photophysical and photophysiological parameters of photosynthetic organisms that could be used to assess their physiological state, photosynthetic efficiency, and primary productivity. On the example of cyanobacteria, we demonstrate the potential of Fluorescence Induction and Relaxation technique (FIRe) and Non-linear Laser Fluorimetry (NLF) in assessing physiological state of phytoplankton. We apply these methods to study mechanism of high light tolerance (non-photochemical quenching). In particular, we show that chlorophyll-containing light harvesting complex of cyanobacteria does not directly participate in the mechanism of non-photochemical quenching. Studies on the effect of spectral properties on the physiological state of cyanobacteria demonstrate that light induced changes in the content, quantity and ratio of chlorophyll- and phycobilin-containing light harvesting complexes could be determined from measured photophysiological parameters. Thus, FIRe and NLF could be used to assess light growth conditions in situ.