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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. Source


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. Source


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. Source


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. Source


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. Source

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