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Zabolotskikh E.,Russian State Hydrometeorological University | Mitnik L.,RAS Ilichev Pacific Oceanological Institute | Chapron B.,French Research Institute for Exploitation of the Sea
Remote Sensing of Environment | Year: 2014

This study presents the results of the comparison between sea surface wind speed (SWS) estimates made by MetOp-A scatterometer ASCAT and GCOM-W1 Advanced Microwave Sounding Radiometer 2 (AMSR2) relating to winds developing in the extratropical cyclones (ECs) over the North Atlantic. One season of winter ECs of 2012-2013 is considered in which 33 most intensive ECs are selected for the study. ASCAT Level 2 operational coastal wind vector product is used for the comparison, whereas AMSR2 SWS values are calculated with newly developed algorithms. Two algorithms for SWS retrieval from AMSR2 are based on numerical simulation of AMSR2 brightness temperatures (TB) over the oceans and their following inversion with Neural Networks. The first algorithm uses TB measurements at higher frequency AMSR2 channels (HF algorithm), the second one uses TB measurements at lower frequency channels (LF algorithm). It is demonstrated that both AMSR2 SWS estimates are highly correlated with ASCAT SWS for the range of low and moderate wind speeds which opens new potential for possible merging of active and passive microwave SWS products. It is shown also that LF AMSR2 algorithm overestimates ASCAT winds greater than 15. m/s. To support the comparison results SWS estimates by AMSR2 are validated against in-situ wind speed measurements from platform weather stations in the North Sea and Norwegian Sea, including high wind events. © 2014 Elsevier Inc.

Zabolotskikh E.V.,Russian State Hydrometeorological University | Mitnik L.M.,RAS Ilichev Pacific Oceanological Institute | Chapron B.,French Research Institute for Exploitation of the Sea
Geophysical Research Letters | Year: 2013

A methodology, based on model simulations and neural networks inversion, is proposed to jointly retrieve sea surface wind speed, sea surface temperature, atmospheric water vapor content, cloud liquid water content, and total atmospheric absorption at 10.65 GHz using Advanced Microwave Scanning Radiometer 2 measurements. In particular, estimation of the total atmospheric absorption at 10.65 GHz, which can be done with high accuracy due to the not so strong influence of liquid water and especially water vapor, helps to refine a new filter to considerably reduce masking ocean areas for severe weather systems, characterized by high wind speeds and moderate atmospheric absorption, appropriate for studying winter extratropical cyclone and polar low systems. A polar low case study has demonstrated significant improvement in the coverage of the ocean area available for geophysical retrievals: Only less than 1% of high wind speed pixels were masked comparatively to the 40-70% masking given by other methods. Key Points Algorithm for atmospheric absorption retrieval from AMSR2 data is developed Threshold value on atmospheric absorption can be used for severe weather masking New weather masking can significantly improve ocean retrieval coverage ©2013. American Geophysical Union. All Rights Reserved.

Ryzhov E.A.,RAS Ilichev Pacific Oceanological Institute
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2014

The paper examines scalar advection caused by a point-vortex pair encountering a fixed point vortex in a uniform flow. The interaction produces two types of vortex motion. First is unbounded as the pair moves unrestrictedly after encountering the fixed vortex. The scalar exchanging between the pair's bubble and fixed vortex's neighbourhood is numerically estimated. Second is bounded as the pair's vortices periodically oscillate about the fixed vortex. The pair's periodic motion perturbs scalar motion causing a portion of scalar trajectories to manifest chaotic behaviour. We analyse scalar transport using Poincaré sections, which reveal regular and chaotic transport regions. © 2014 Elsevier B.V. All rights reserved.

Koshel K.V.,RAS Ilichev Pacific Oceanological Institute | Ryzhov E.A.,RAS Ilichev Pacific Oceanological Institute
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2012

The movement of a pair of point vortices with arbitrary intensities, embedded in a nonstationary shear and rotational flow, is studied. The expression for the vorticity center is shown to be reduced to a Riccati equation. In the particular case of harmonic oscillations, parametric resonance, which results in unbounded motion of the vortex pair, is found and analyzed. Using the fast oscillation averaging, an analytical estimate for the main zone in the parametric space is obtained. With the help of numerical calculations, the reliability of the estimate is asserted and a family of the minor zones is obtained. © 2011 Elsevier B.V. All rights reserved.

Gulin O.E.,RAS Ilichev Pacific Oceanological Institute | Yaroshchuk I.O.,RAS Ilichev Pacific Oceanological Institute
Journal of Computational Acoustics | Year: 2014

Statistical problems encountered in the study of the influence of random inhomogeneities in layered shallow water on the propagation of sound signal is considered. The study is carried out by the example of two-layer models of the sea - a stochastic Pekeris waveguide and a waveguide with a regular refraction in the water layer, which describes the presence of the thermocline. The results were obtained by statistical simulation without approximations and assumptions. In the middle frequency range for actual parameters of sound speed fluctuations in shallow sea with a loss penetrable bottom, the specific features of acoustic field statistical moments behavior have been discovered. They did not get adequate attention in the scientific literature. © IMACS.

Maksimov A.O.,RAS Ilichev Pacific Oceanological Institute
Acoustical Physics | Year: 2011

Hydrocarbon sources on the ocean floor produce buoyant bubble plumes, i.e., gas flares. In winter, bubbles reaching the surface freeze in an ice sheet. Such clouds of frozen bubbles are observable in Arctic seas and are usual elements of ice sheets of lakes, e.g., Lake Baikal. Based on the general solution of the problem of scattering by a sphere in an isotropic elastic medium, the frozen bubble scattering cross section is found. The theory of multiple scattering by frozen bubble plume is derived. The structure of low-frequency resonances corresponding to collective oscillations of a bubble cloud is described. © 2011 Pleiades Publishing, Ltd.

Ryzhov E.A.,RAS Ilichev Pacific Oceanological Institute
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

The dynamics of fluid particles in the vicinity of a self-propagating vortex pair, embedded in a nonstationary shear flow, is studied. When the shear flow is steady, the vicinity of the pair, which is called as a vortex atmosphere, consists of closed stream-lines, which coincide with fluid particles' trajectories. When the shear flow is nonstationary, the trajectories' behaviour changes drastically, then chaotic advection occurs. It is shown in the Letter that the vortex pair propagation velocity varies with the parameters (amplitude, and frequency) of the nonstationary shear flow. It is demonstrated, that changing of the mean velocity leads to changing of the size of the atmosphere. © 2011 Elsevier B.V.

Ryzhov E.A.,RAS Ilichev Pacific Oceanological Institute | Koshel K.V.,RAS Ilichev Pacific Oceanological Institute
Nonlinear Processes in Geophysics | Year: 2013

In the frame of a three-layer, quasi-geostrophic analytical model of an f-plane geophysical flow, the Lagrangian advection induced by the interaction of a monopole vortex with an isolated topographic feature is addressed. Two different cases when the monopole is located either within the upper or the middle layer are of our interest. In the bottom layer, there is a delta-function topographic feature, which generates a closed recirculation region in its vicinity due to the background flow. This recirculation region extends to the middle and upper layers, and it plays the role of a topographic vortex. The interaction between the monopole and the topographic vortex causes a complex, including chaotic, advection of fluid particles. We show that the model's parameters, namely the monopole and topographic vortices' strengths and initial positions, and the layers' depths and densities, are responsible for the diverse advection patterns. While the patterns are rather complicated, one can single out two major processes, which mostly govern the fluid particle advection. The first one is the variation in time of the system's phase space structure, so that within the closed region of the topographic vortex, there appear periodically unclosed particle pathways by which the particles leave the topographic vortex. The second one is chaotic advection that arises from the nonstationarity of the monopole-topography interaction. © 2013 Author(s).

Sattarova V.V.,RAS Ilichev Pacific Oceanological Institute | Artemova A.V.,RAS Ilichev Pacific Oceanological Institute
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2015

Sediments from the abyssal plain adjacent to the Kuril-Kamchatka Trench were collected during the German-Russian cruise for the Kuril Kamchatka Biodiversity Study, and the chemical composition, quantitative content, and species composition of collected diatoms were studied. The collected sediments are silt and clayey silt, the SiO2am and Corg contents range 7.58-19.38% and 0.44-1.55%, respectively. The enrichment of silts by amorphous silica indicates the presence of a significant number of organisms (predominantly diatoms) with an opal skeleton. High Corg content in sediments reflects biological productivity, which is controlled by factors such as water circulation and the distribution of nutrients. Interrelation trends among chemical constituents is investigated via multi-component statistics. Diatom assemblages reflect present-day water masses characterized by high nutrient content, surface water circulation, and sedimentation conditions for different parts of the study area. Analysis of this new data also highlights changes in the response of diatom flora due to abiotic factors. © 2014 Elsevier Ltd.

Pochekutova I.A.,RAS Ilichev Pacific Oceanological Institute | Korenbaum V.I.,RAS Ilichev Pacific Oceanological Institute
Respirology | Year: 2013

Background and objective Increased forced expiratory time was first recognized as a marker of obstruction half a century ago. However, the reported diagnostic capabilities of both auscultated forced expiratory time (FET as) and spirometric forced expiratory time are contradictory. Computer analysis of respiratory noises provides a precise estimation of acoustic forced expiratory noise time (FETa) being the object-measured analogue of FETas. The aim of this study was to analyse FETa diagnostic capabilities in patients with asthma based on the hypothesis that FETa could reveal hidden bronchial obstruction. Methods A group of asthma patients involved 149 males aged 16-25 years. In this group, 71 subjects had spirometry features of bronchial obstruction, meanwhile, the remaining 78 had normal spirometry. A control group involved 77 healthy subjects. Spirometry and forced expiratory tracheal noise recording were sequentially measured for each participant. FETa values were estimated by means of a developed computer procedure, including bandpass filtration (200-2000 Hz), waveform envelope calculation with accumulation period of 0.01 s, automated measurement of FETa at 0.5% level from the peak amplitude. Results Specificity, sensitivity and area under Receiver Operating Characteristic curve of FETa and its ratios to squared chest circumference, height, weight were indistinguishable with baseline spirometry index FEV1/forced vital capacity. Meanwhile, acoustic features of obstruction were revealed in 41%-49% of subgroup of patients with asthma but normal spirometry. Conclusions FETa of tracheal noise and its ratio to anthropometric parameters seem to be sensitive and specific tests of hidden bronchial obstruction in young male asthma patients. We analysed the capability of computerized assessment of tracheal forced expiratory noise time to reveal hidden bronchial obstruction in individuals with known asthma but normal spirometry. Acoustic features of bronchial obstruction were found in 41%-49% of 78 male subjects. © 2012 The Authors. Respirology © 2012 Asian Pacific Society of Respirology.

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