4DVAR data assimilation in the Intra-Americas Sea with the Regional Ocean Modeling System (ROMS)   总被引：2，自引：0，他引：2  

B.S. Powell  H.G. Arango  A.M. Moore  E. Di Lorenzo  R.F. Milliff  D. Foley   《Ocean Modelling》2008,23(3-4):130-145

We present the background, development, and preparation of a state-of-the-art 4D variational (4DVAR) data assimilation system in the Regional Ocean Modeling System (ROMS) with an application in the Intra-Americas Sea (IAS). This initial application with a coarse model shows the efficacy of the 4DVAR methodology for use within complex ocean environments, and serves as preparation for deploying an operational, real-time assimilation system onboard the Royal Caribbean Cruise Lines ship Explorer of the Seas. Assimilating satellite sea surface height and temperature observations with in situ data from the ship in 14 day cycles over 2 years from January 2005 through March 2007, reduces the observation-model misfit by over 75%. Using measures of the Loop Current dynamics, we show that the assimilated solution is consistent with observed statistics.  相似文献   

Transport and retention of a conservative tracer in an isolated creek–marsh system     

J.O. Blanton  A.J. Garrett  J.S. Bollinger  D.W. Hayes  L.D. Koffman  J. Amft  T. Moore 《Estuarine, Coastal and Shelf Science》2010

A study of tracer transport and retention in a small tidal creek and marsh system located in the southeastern US was conducted using a three-dimensional hydrodynamic model and data from a dye tracer release. The model simulated tidally driven flow, including inundation and drying out of the marshes and the dispersal of the dye tracer. Flow measurements in the tidal creek showed that the simulations appeared to generally duplicate the tidally driven flow into and out of the tidal creeks and marshes. The dye tracer experiment was conducted to test the hydrodynamic model's ability to simulate dispersal of a point release of pollutants into the creek during an incoming tide. The simulations reproduced much of the experimental measurements, but bathymetric errors and lack of resolution of the smallest arms of the tidal creeks affected the ability to faithfully reproduce the initial peak in measured dye tracer concentrations at a sampling location far from the boundary. The lack of the smallest tidal creeks led to some trapping of water and dye in the marshes. Two independent estimates of flushing time yielded values between 1.6 and 2.4 days. An uncertainty analysis indicates that model simulations are sensitive to variations in parameters such as water depth and marsh grass density. On the other hand, omission of the smallest tidal creeks in simulations may be partially offset by decreasing marsh grass density. Further improvements must rely on more accurate and detailed bathymetric data that resolves the smaller arms of the tidal creeks and includes quantitative information about the density and distribution of marsh grass.  相似文献   

The effect of soil–structure interaction on the seismic risk to buildings     

Farid Khosravikia  Mojtaba Mahsuli  Mohammad Ali Ghannad 《Bulletin of Earthquake Engineering》2018,16(9):3653-3673

This paper studies the effect of soil–structure interaction (SSI) on the seismic risk estimates of buildings. Risk, in this context, denotes the probability distribution of seismic monetary loss due to structural and nonstructural damage. The risk analysis here uncovers the probability that SSI is beneficial, detrimental, or uninfluential on seismic losses. The analyses are conducted for a wide range of buildings with different structural systems, numbers of stories, and foundation sizes on various soil types. A probabilistic approach is employed to account for prevailing sources of uncertainty, i.e., those in ground motion and in the properties of the soil–structure system. In this approach, probabilistic models are employed to predict the response, damage, and repair cost of buildings. To properly account for the ground motion uncertainty, a suite of nearly 7000 accelerograms recorded on soil is employed. It is concluded that structures on very soft soils are extremely likely to incur smaller losses due to SSI, which is in line with the common belief that SSI is a favorable effect for such systems. However, the results for buildings on moderately soft soils reveal a considerable probability, up to 0.4, that SSI has an adverse effect on the structure and increases the seismic losses.  相似文献   

Hydrocarbon‐Rich Groundwater above Shale‐Gas Formations: A Karoo Basin Case Study          下载免费PDF全文

William K. Eymold  Kelley Swana  Myles T. Moore  Colin J. Whyte  Jennifer S. Harkness  Siep Talma  Ricky Murray  Joachim B. Moortgat  Jodie Miller  Avner Vengosh  Thomas H. Darrah 《Ground water》2018,56(2):204-224

Horizontal drilling and hydraulic fracturing have enhanced unconventional hydrocarbon recovery but raised environmental concerns related to water quality. Because most basins targeted for shale‐gas development in the USA have histories of both active and legacy petroleum extraction, confusion about the hydrogeological context of naturally occurring methane in shallow aquifers overlying shales remains. The Karoo Basin, located in South Africa, provides a near‐pristine setting to evaluate these processes, without a history of conventional or unconventional energy extraction. We conducted a comprehensive pre‐industrial evaluation of water quality and gas geochemistry in 22 groundwater samples across the Karoo Basin, including dissolved ions, water isotopes, hydrocarbon molecular and isotopic composition, and noble gases. Methane‐rich samples were associated with high‐salinity, NaCl‐type groundwater and elevated levels of ethane, ⁴He, and other noble gases produced by radioactive decay. This endmember displayed less negative δ¹³C‐CH₄ and evidence of mixing between thermogenic natural gases and hydrogenotrophic methane. Atmospheric noble gases in the methane‐rich samples record a history of fractionation during gas‐phase migration from source rocks to shallow aquifers. Conversely, methane‐poor samples have a paucity of ethane and ⁴He, near saturation levels of atmospheric noble gases, and more negative δ¹³C‐CH₄; methane in these samples is biogenic and produced by a mixture of hydrogenotrophic and acetoclastic sources. These geochemical observations are consistent with other basins targeted for unconventional energy extraction in the USA and contribute to a growing data base of naturally occurring methane in shallow aquifers globally, which provide a framework for evaluating environmental concerns related to unconventional energy development (e.g., stray gas).  相似文献   

Tidal pumping and biogeochemical processes: Dissolution within the tidal capillary fringe of eogenetic coastal carbonates     

J.D. Gulley  D. Breecker  M. Covington  S. Cooperdock  J. Banner  P.J. Moore  A. Noronha  C. Breithaupt  J.B. Martin  J. Jenson 《地球表面变化过程与地形》2020,45(11):2675-2688

Growing evidence suggests microbial respiration of dissolved organic carbon (DOC) may be a principal driver of subsurface dissolution and cave formation in eogenetic carbonate rock. Analyses of samples of vadose zone gasses, and geochemical and hydrological data collected from shallow, uncased wells on San Salvador Island, Bahamas, suggest tidally varying water tables may help fuel microbial respiration and dissolution through oxygenation. Respiration of soil organic carbon transported to water tables generates dysaerobic to anaerobic groundwater, limiting aerobic microbial processes. Positive correlations of carbon dioxide (CO₂), radon-222 (²²²Rn) and water table elevation indicate, however, that tidal pumping of water tables pulls atmospheric air that is rich in oxygen, and low in CO₂ and ²²²Rn, into contact with the tidal capillary fringe during falling tides. Ratios of CO₂ and O₂ in vadose gas relative to the atmosphere indicate this atmospheric oxygen fuels respiration within newly-exposed, wetted bedrock. Deficits of expected CO₂ relative to O₂ concentrations indicate some respired CO₂ is likely removed by carbonate mineral dissolution. Tidal pumping also appears capable of transferring oxygen to the freshwater lens, where it could also contribute to respiration and dissolution; dissolved oxygen concentrations at the water table are at least 5% saturated and decline to anaerobic conditions 1–2 m below. Our results demonstrate how tidal pumping of air to vadose zones can drive mineral dissolution reactions that are focused near water tables and may contribute to the formation of laterally continuous vuggy horizons and potentially caves. © 2020 John Wiley & Sons, Ltd.  相似文献   

Predicting the maximum sunspot number and the associated geomagnetic activity indices a a $aa$ and A p $Ap$ for solar cycle 25     

Singh  P. R.  Saad Farid  A. I.  Singh  A. K.  Pant  T. K.  Aly  Ayman A. 《Astrophysics and Space Science》2021,366(5):1-6

We are considering the spacetime described by the metric proposed by Mannheim and Kazanas. The effective potential and the circular orbits are discussed. The rotational velocity derived from the geodesics equation agrees with the observed flat galactic rotation curves. Finally, solutions to the Gordon equation for massless bosons evolving in this spacetime are obtained in terms of Heun general functions.

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Flexibility of superstructures and supports in the seismic analysis of simple bridges     

Farid Alfawakhiri  Michel Bruneau 《地震工程与结构动力学》2000,29(5):711-729

This paper addresses the elastic dynamic response of simply supported bridges to ground motion in their transverse direction. The interaction between superstructure and support flexibilities is studied in a systematic manner for symmetric spans. The bridges are modelled as beams with uniformly distributed mass and elasticity, simply supported at the ends by elastic springs. It is shown that a dimensionless stiffness index, which reflects the relative stiffness of the superstructure compared to the stiffness of the substructure, completely defines the dynamic mode shapes of the model. Useful closed‐form expressions, based on approximate shape functions, are derived for the dynamic parameters of the first mode, and their accuracy is assessed. The effect of the stiffness index on these dynamic parameters is investigated. Numerical case studies are presented to illustrate the use of proposed equations in the seismic analysis of bridges. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Cytochrome P4051A expression and localization in organs of the minke whale (Balaenoptera acutorostrata)     

J. J. Stegeman  C. A. Miller  J. Beyer  M. J. Moore  A. Goksyr 《Marine environmental research》1998,46(1-5)

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Distribution of diffuse flow megafauna in two sites on the Eastern Lau Spreading Center, Tonga     

Elizabeth L. Podowski  Tom S. Moore  Kevin A. Zelnio  George W. Luther III  Charles R. Fisher 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2041-2056

Hydrothermal vent environments are characterized by large gradients of toxic chemicals and high temperatures, which play a significant role in defining species’ distributions. We used high-resolution imagery and spatially explicit in-situ physico-chemical measurements analyzed within a Geographic Information System (GIS) in order to characterize the spatial relations among different groups of megafauna, temperature, and chemistry within two discrete vent communities (40 and 50 m²) on the Eastern Lau Spreading Center (ELSC). Chemical (sulfide and O₂ concentrations) and temperature data were obtained from approximately 75 different locations within each community using in-situ instruments. All data were integrated into a GIS, which served as a visualization tool and enabled the data to be analyzed in a spatial context. Our results confirm the importance of abiotic variables in defining the distributions of some fauna and elucidate several biological associations that are consistent between the two communities. The provannid snail, Alviniconcha spp., appears to actively avoid temperatures above 32–46 °C and/or sulfide concentrations exceeding approximately 260 μM. Slightly higher average sulfide concentrations and temperatures were measured among aggregations of Ifremeria nautilei compared to aggregations of the mussel Bathymodiolus brevior; however, the presence of mixed aggregations of the two species indicates an overlap in requirements. The brachyuran crab, Austinograea spp., was consistently observed directly on symbiont-containing species, particularly Alviniconcha spp. The solitary snail, Eosipho desbruyeresi, was rarely observed on biological substrata, but was often (60% of its population at the most active site) within 5 cm of symbiont-containing fauna, indicating a tolerance and preference for proximity to areas of high productivity. Densities and coverage of species differed substantially between the two communities despite high species overlap. Symbiont-containing species covered much larger areas at the more hydrothermally active site, ABE1, while shrimp and anemones occurred in relatively higher densities within the less-active site, TM1. This is the first study to thoroughly characterize realized distributions of megafauna at vent sites along the ELSC.  相似文献   

Provenance record of late Maastrichtian–late Palaeocene Andean Mountain building in the Amazonian retroarc foreland basin (Madre de Dios basin,Peru)          下载免费PDF全文

Mélanie Louterbach  Martin Roddaz  Pierre‐Olivier Antoine  Laurent Marivaux  Sylvain Adnet  Julien Bailleul  Elton Dantas  Roberto Ventura Santos  Farid Chemale Jr  Patrice Baby  Caroline Sanchez  Ysabel Calderon 《地学学报》2018,30(1):17-23

Biostratigraphic, sedimentological and provenance analyses suggest that a proto‐Andean Cordillera already existed in southern Peru by late Maastrichtian–late Palaeocene times. A 270‐m‐thick stratigraphic section shows changes in depositional environments from shallow marine (early Maastrichtian) to non‐marine (late Maastrichtian) then back to estuarine (late Palaeocene) conditions. An erosional surface separates lower Maastrichtian from upper Maastrichtian deposits. Above this surface, the late Maastrichtian unit exhibits moderately developed palaeosols and syn‐sedimentary normal faults. The sedimentary evolution is accompanied by a decrease in sedimentation rate and by changes in provenance. Shallow marine lower Maastrichtian deposits have a cratonic provenance as shown by their low εNd(0) values (?15 to ?16) and the presence of Precambrian inherited zircon grains. The upper Maastrichtian deposits have a mixed Andean and cratonic origin with εNd(0) values of ~12.6 and yield the first Cretaceous and Permo‐Triassic zircon grains. Estuarine to shallow marine upper Palaeocene deposits have an Andean dominant source as attested by higher εNd(0) values (?6 to ?10) and by the presence of Palaeozoic and Late Cretaceous zircon grains. The changes in depositional environments and sedimentation rates, as well as the shift in detrital provenance, are consistent with a late Maastrichtian–late Palaeocene period of Andean mountain building. In agreement with recently published studies, our data suggest that an Andean retroarc foreland basin was active by late Maastrichtian–late Palaeocene times.  相似文献