Applying the adjoint-free 4dVar assimilation to modeling the Kuroshio south of Japan     

Miyazawa  Yasumasa  Yaremchuk  Max  Varlamov  Sergey M.  Miyama  Toru  Aoki  Kunihiro 《Ocean Dynamics》2020,70(8):1129-1149

Ocean Dynamics - Operational ocean nowcast/forecast systems require real-time sampling of oceanic data for representing realistic oceanic conditions. Satellite altimetry plays a key role in...  相似文献   

Using Resin‐Based 3D Printing to Build Geometrically Accurate Proxies of Porous Sedimentary Rocks          下载免费PDF全文

Sergey Ishutov  Franciszek J. Hasiuk  Dawn Jobe  Susan Agar 《Ground water》2018,56(3):482-490

Three‐dimensional (3D) printing is capable of transforming intricate digital models into tangible objects, allowing geoscientists to replicate the geometry of 3D pore networks of sedimentary rocks. We provide a refined method for building scalable pore‐network models (“proxies”) using stereolithography 3D printing that can be used in repeated flow experiments (e.g., core flooding, permeametry, porosimetry). Typically, this workflow involves two steps, model design and 3D printing. In this study, we explore how the addition of post‐processing and validation can reduce uncertainty in the 3D‐printed proxy accuracy (difference of proxy geometry from the digital model). Post‐processing is a multi‐step cleaning of porous proxies involving pressurized ethanol flushing and oven drying. Proxies are validated by: (1) helium porosimetry and (2) digital measurements of porosity from thin‐section images of 3D‐printed proxies. 3D printer resolution was determined by measuring the smallest open channel in 3D‐printed “gap test” wafers. This resolution (400 µm) was insufficient to build porosity of Fontainebleau sandstone (～13%) from computed tomography data at the sample's natural scale, so proxies were printed at 15‐, 23‐, and 30‐fold magnifications to validate the workflow. Helium porosities of the 3D‐printed proxies differed from digital calculations by up to 7% points. Results improved after pressurized flushing with ethanol (e.g., porosity difference reduced to ～1% point), though uncertainties remain regarding the nature of sub‐micron “artifact” pores imparted by the 3D printing process. This study shows the benefits of including post‐processing and validation in any workflow to produce porous rock proxies.  相似文献   

Classification issues within ensemble-based simulation: application to surge floods forecasting     

Sergey?V.?KovalchukEmail authorView author&#;s OrcID profile  Aleksey?V.?Krikunov  Konstantin?V.?Knyazkov  Alexander?V.?Boukhanovsky 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(5):1183-1197

The paper proposes a high-level conceptual and technological approach to manage the ensemble-based simulation, taking into account changing states of both simulated system and system of models. The approach includes systematization of ensemble-based modeling and simulation techniques, analysis of simulation results, quality assessments, and detailed analysis of ensemble management procedures using classification operators. The technological basis for such an approach includes ensemble-based simulation techniques using domain-specific software combined within a composite application; data science approaches for analysis of available datasets (simulation data, observations, situation assessments, etc.). Within this work, a set of case studies is addressed to examine the opportunities provided by the developed approach considering ensemble-based simulation of storm surges for flood prediction in St. Petersburg, Russia as an example.  相似文献   

Mesoscale circulation along the Sakhalin Island eastern coast   总被引：1，自引：1，他引：0  

Sergey V. Prants  Andrey G. Andreev  Michael Yu. Uleysky  Maxim V. Budyansky 《Ocean Dynamics》2017,67(3-4):345-356

The seasonal and interannual variability of mesoscale circulation along the eastern coast of the Sakhalin Island in the Okhotsk Sea is investigated using the AVISO velocity field and oceanographic data for the period from 1993 to 2016. It is found that mesoscale cyclones with the horizontal dimension of about 100 km occur there predominantly during summer, whereas anticyclones occur predominantly during fall and winter. The cyclones are generated due to a coastal upwelling forced by northward winds and the positive wind stress curl along the Sakhalin coast. The anticyclones are formed due to an inflow of low-salinity Amur River waters from the Sakhalin Gulf intensified by southward winds and the negative wind stress curl in the cold season. The mesoscale cyclones support the high biological productivity at the eastern Sakhalin shelf in July– August.  相似文献   

Elastic wave‐vector decomposition in heterogeneous anisotropic media          下载免费PDF全文

Yanadet Sripanich  Sergey Fomel  Junzhe Sun  Jiubing Cheng 《Geophysical Prospecting》2017,65(5):1231-1245

The goal of wave‐mode separation and wave‐vector decomposition is to separate a full elastic wavefield into three wavefields with each corresponding to a different wave mode. This allows elastic reverse‐time migration to handle each wave mode independently. Several of the previously proposed methods to accomplish this task require the knowledge of the polarisation vectors of all three wave modes in a given anisotropic medium. We propose a wave‐vector decomposition method where the wavefield is decomposed in the wavenumber domain via the analytical decomposition operator with improved computational efficiency using low‐rank approximations. The method is applicable for general heterogeneous anisotropic media. To apply the proposed method in low‐symmetry anisotropic media such as orthorhombic, monoclinic, and triclinic, we define the two S modes by sorting them based on their phase velocities (S1 and S2), which are defined everywhere except at the singularities. The singularities can be located using an analytical condition derived from the exact phase‐velocity expressions for S waves. This condition defines a weight function, which can be applied to attenuate the planar artefacts caused by the local discontinuity of polarisation vectors at the singularities. The amplitude information lost because of weighting can be recovered using the technique of local signal–noise orthogonalisation. Numerical examples show that the proposed approach provides an effective decomposition method for all wave modes in heterogeneous, strongly anisotropic media.  相似文献   

Precambrian crustal contribution to the Variscan accretionary prism of the Kaczawa Mountains (Sudetes,SW Poland): evidence from SHRIMP dating of detrital zircons     

Ryszard Kryza  Jan Zalasiewicz  Stanisław Mazur  Paweł Aleksandrowski  Sergey Sergeev  Alexander Larionov 《International Journal of Earth Sciences》2007,96(6):1153-1162

SHRIMP dating of detrital zircons from sandstones of the Gackowa Formation (Kaczawa Complex, Sudetes, SW Poland) indicates input from late (550–750 Ma) and early Proterozoic to Archaean sources (∼2.0–3.4 Ga, the latter being the oldest recorded age from the Sudetic region). These dates preclude within-terrane derivation from seemingly correlatory acid volcanic rocks of early Palaeozoic age. Rather, they indicate provenance from Cadomian and older rocks that currently form part of other, geographically distant terranes; the most likely source identified to date is the Lusatian Block in the Saxothuringian Zone. Hence, the Gackowa Formation may be late Proterozoic rather than early Palaeozoic in depositional age, possibly coeval with the late Proterozoic (pre-Cadomian) greywackes of Lusatia, being subsequently tectonically interleaved with early Palaeozoic volcanic rocks into the Kaczawa accretionary prism during the Variscan orogeny. However, correlation with the lithologically similar early Ordovician Dubrau Quartzite of Saxothuringia, and so assignation to the early Paleozoic (post-Cadomian) rift succession deposited at the northern margin of Gondwana, cannot yet be precluded.  相似文献   

Coordinated monitoring of the eccentric O-star binary Iota Orionis: optical spectroscopy and photometry     

Sergey V. Marchenko  Gregor Rauw  Eleonora A. Antokhina  Igor I. Antokhin  Dominique Ballereau  Jacques Chauville  Michael F. Corcoran  Rafael Costero  Juan Echevarria  Thomas Eversberg  Ken G. Gayley  Gloria Koenigsberger  Anatoly S. Miroshnichenko  Anthony F. J. Moffat  Nidia I. Morrell  Nancy D. Morrison  Christopher L. Mulliss  Julian M. Pittard  Ian R. Stevens  Jean-Marie Vreux  Jean Zorec 《Monthly notices of the Royal Astronomical Society》2000,317(2):333-342

With the objective of investigating the windwind collision phenomenon and supporting contemporaneous X-ray observations, we have organized a large-scale, coordinated optical monitoring campaign of the massive, highly eccentric O9 III+B1 III binary Iota Orionis. Successfully separating the spectra of the components, we refine the orbital elements and confirm the rapid apsidal motion in the system. We also see strong interaction between the components during periastron passage and detect phase-locked variability in the spectrum of the secondary star. However, we find no unambiguous signs of the bow shock crashing on the surface of the secondary, despite the predictions of hydrodynamic simulations. Combining all available photometric data, we find rapid, phase-locked variations and model them numerically, thus restricting the orbital inclination to 50° i 70°.  相似文献   

Shallow groundwater dynamics and its driving forces in extremely arid areas: a case study of the lower Heihe River in northwestern China          下载免费PDF全文

Ping Wang  Jingjie Yu  Sergey P. Pozdniakov  Sergey O. Grinevsky  Changming Liu 《水文研究》2014,28(3):1539-1553

Shallow groundwater is an important source of water for the maintenance and restoration of ecosystems in arid environments, which necessitates a deeper understanding of its complex spatial and temporal dynamics driven by hydrological processes. This study explores the dominant hydrological processes that control the shallow groundwater dynamics in the Gobi Desert‐riparian‐oasis system of the lower Heihe River, a typical arid inland river basin located in northwestern China. The groundwater level and temperature were monitored in 14 shallow wells at 30‐min intervals during the 2010–2012 period. After combining this information with meteorological and hydrological data, a comprehensive analysis was conducted to understand the dynamic behaviour of the shallow groundwater system and to determine the dominant factors that control the groundwater flow processes. The results of the study indicate notably large temporal and spatial variations in both the groundwater level and temperature. Noticeable fluctuations in the groundwater level (0.5–1 m) and temperature (4–8 °C) were observed in the riparian zone, evidencing a clear river influence. In comparison, the groundwater fluctuations in the Gobi Desert were more stable (the annual variations of the water table were less than 0.5 m, and the water temperature varied by no more than 2 °C). Strong variations in the groundwater table (1.5–5.0 m/year) and temperature (1.5–6.5 °C), mainly caused by surface flood irrigation and groundwater pumping, were observed in the oasis area. The investigated sites were categorized into three types that reflect the dominant hydrological processes: (1) the riparian zone, dominated by riverbank filtration and groundwater evapotranspiration; (2) the Gobi Desert area, controlled by groundwater evaporation and lateral recharge; and (3) the oasis area, dominated by groundwater evapotranspiration as well as surface–groundwater interactions caused by human activities. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Engelhauptite,KCu3(V2O7)(OH)2Cl,a new mineral species from Eifel,Germany     

Igor V. Pekov  Oleg I. Siidra  Nikita V. Chukanov  Vasiliy O. Yapaskurt  Sergey N. Britvin  Sergey V. Krivovichev  Willi Schüller  Bernd Ternes 《Mineralogy and Petrology》2015,109(6):705-711

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Calcinaksite,KNaCa(Si4O10) H2O,a new mineral from the Eifel volcanic area,Germany     

Nikita V. Chukanov  Sergey M. Aksenov  Ramiza K. Rastsvetaeva  Günter Blass  Dmitry A. Varlamov  Igor V. Pekov  Dmitry I. Belakovskiy  Vladislav V. Gurzhiy 《Mineralogy and Petrology》2015,109(4):397-404

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