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931.
932.
Sébastien Blaise Eric Deleersnijder Laurent White Jean-François Remacle 《Continental Shelf Research》2007
A three-dimensional finite-element model is used to investigate the tidal flow around Rattray Island, Great Barrier Reef, Australia. Field measurements and visual observations show both stable eddies developing at rising and falling tide in the wake of the island. The water turbidity suggests intense upwelling able to carry bed sediments upwards. Based on previous numerical studies, it remains unclear at this point whether the most intense upwelling occurs near the centre of the eddies or off the island's tips, closer to the island. All these studies resorted to a very simple turbulence closure, with a zero-equation model whereby the coefficient of vertical viscosity is computed via an algebraic expression. In this work, we aim at studying the influence of the turbulence closure on model results, with emphasis on the prediction of vertical motions. The Mellor and Yamada level 2.5 closure scheme is used and an increase in the intensity of vertical transport is observed. This increase is partly explained by the fact that the Mellor and Yamada model takes into account the hysteresis effect in the time variation of turbulence variables. The influence of the advection of turbulence variables is estimated to be negligible. By a better representation of transient coastal phenomena, the Mellor and Yamada level 2.5 turbulence closure improves the model to a significant degree. 相似文献
933.
Scaling characteristics of spatial patterns of soil moisture from distributed modelling 总被引:1,自引:0,他引:1
Salvatore Manfreda Matthew F. McCabe Mauro Fiorentino Ignacio Rodríguez-Iturbe Eric F. Wood 《Advances in water resources》2007
Characterizing the spatial dynamics of soil moisture fields is a key issue in hydrology, offering an avenue to improve our understanding of complex land surface–atmosphere interactions. In this paper, the statistical structure of soil moisture patterns is examined using modelled soil moisture obtained from the North American Land Data Assimilation System (NLDAS) at 0.125° resolution. The study focuses on the vertically averaged soil moisture in the top 10 cm and 100 cm layers. The two variables display a weak dependence for lower values of surface soil moisture, with the strength of the relationship increasing with the water content of the top layer. In both cases, the variance of the soil moisture follows a power law decay as a function of the averaging area. The superficial layer shows a lower degree of spatial organization and higher temporal variability, which is reflected in rapid changes in time of the slope of the scaling functions of the soil moisture variance. Conversely, the soil moisture in the top 100 cm has lower variability in time and larger spatial correlation. The scaling of these patterns was found to be controlled by the changes in the soil water content. Results have implications for the downscaling of soil moisture to prevent model bias. 相似文献
934.
TONG WeiWei WANG LiangShu MI Ning XU MingJie LI Hua YU DaYong LI Cheng LIU ShaoWen LIU Mian Eric SanDvol 《中国科学D辑(英文版)》2007,50(Z2):227-233
A portable broadband seismic array was deployed from the northeast Tibetan Plateau to the southwest Ordos block, China. The seismic structure of the crust and uppermost mantle of the Liupanshan area is obtained using receiver function analysis of teleseismic body waves. The crustal thickness and Poisson's ratios are estimated by stacking the weighted amplitudes of receiver functions. Our results reveal complex seismic phases in the Liupanshan area, implying intense deformation at the boundary between the Tibetan Plateau and the Ordos block. The average crustal thickness is 51.5 km in the northeast Tibetan Plateau, 53.5 km in the Liupan Mountain and 50 km in the southwest Ordos block, resulting in a concave Moho beneath the Liupan Mountain. The Poisson's ratio of the Liupanshan area varies between 0.27-0.29, higher than the value of 0.25-0.26 to the east and west of the Liupan Mountain, suggesting partial melting in the lower crust. The variance in Poisson's ratio across the Liupan Mountain indicates notable changes in the crustal composition and mechanical properties, which may be formed by the northeastward flow of the Tibetan lower crust during the India-Eurasia collision. 相似文献
935.
936.
937.
Joseph A. Stewart Steven J. Christopher John R. Kucklick Louise Bordier Thomas B. Chalk Arnaud Dapoigny Eric Douville Gavin L. Foster William R. Gray Rosanna Greenop Marcus Gutjahr Freya Hemsing Michael J. Henehan Philip Holdship Yu‐Te Hsieh Ana Kolevica Yen‐Po Lin Elaine M. Mawbey James W. B. Rae Laura F. Robinson Rachael Shuttleworth Chen‐Feng You Shuang Zhang Russell D. Day 《Geostandards and Geoanalytical Research》2021,45(1):77-96
The boron isotopic ratio of 11B/10B (δ11BSRM951) and trace element composition of marine carbonates are key proxies for understanding carbon cycling (pH) and palaeoceanographic change. However, method validation and comparability of results between laboratories requires carbonate reference materials. Here, we report results of an inter‐laboratory comparison study to both assign δ11BSRM951 and trace element compositions to new synthetic marine carbonate reference materials (RMs), NIST RM 8301 (Coral) and NIST RM 8301 (Foram) and to assess the variance of data among laboratories. Non‐certified reference values and expanded 95% uncertainties for δ11BSRM951 in NIST RM 8301 (Coral) (+24.17‰ ± 0.18‰) and NIST RM 8301 (Foram) (+14.51‰ ± 0.17‰) solutions were assigned by consensus approach using inter‐laboratory data. Differences reported among laboratories were considerably smaller than some previous inter‐laboratory comparisons, yet discrepancies could still lead to large differences in calculated seawater pH. Similarly, variability in reported trace element information among laboratories (e.g., Mg/Ca ± 5% RSD) was often greater than within a single laboratory (e.g., Mg/Ca < 2%). Such differences potentially alter proxy‐reconstructed seawater temperature by more than 2 °C. These now well‐characterised solutions are useful reference materials to help the palaeoceanographic community build a comprehensive view of past ocean changes. 相似文献
938.
Maria Rosa Scicchitano Michael J. Spicuzza Eric T. Ellison David Tuschel Alexis S. Templeton John W. Valley 《Geostandards and Geoanalytical Research》2021,45(1):161-187
The ability to constrain the petrogenesis of multiple serpentine generations recorded at the microscale is crucial for estimating the extent and conditions of modern versus fossil serpentinisation in ophiolites. To address matrix bias effects during oxygen isotope analysis by SIMS, we present the first investigation analysing antigorite in the compositional range Mg# = 77.5–99.5 mole %, using a CAMECA IMS‐1280 secondary ion mass spectrometer. Spot‐to‐spot homogeneity is ≤ 0.5‰ (2s) for the new antigorite reference materials. The relative bias between antigorite reference materials with different Mg/Fe ratios is described by a second‐order polynomial, and a maximum difference in bias of ~ 1.8‰ was measured for Mg# ~ 78 to 100. We observed a bias up to ~ 1.0‰ between lizardite and antigorite attributed to their different crystal structures. Orientation effects up to ~ 1‰ were observed in chrysotile. The new analytical protocol allowed the identification of oxygen isotope zoning up to ~ 7‰ in serpentine minerals from two serpentinites recovered from an area of active serpentinisation in the Samail ophiolite. Thus, in situ analysis is capable of resolving isotopic heterogeneity that may directly reflect changes in the physical and chemical conditions of multiple serpentinisation events in the Samail ophiolite. 相似文献
939.
Tate Eric Rahman Md Asif Emrich Christopher T. Sampson Christopher C. 《Natural Hazards》2021,106(1):435-457
Natural Hazards - Human exposure to floods continues to increase, driven by changes in hydrology and land use. Adverse impacts amplify for socially vulnerable populations, who disproportionately... 相似文献
940.
Natural Hazards - This study investigates economic damage risk due to extreme rainfall during tropical storms in Jamaica. To this end, remote sensing precipitation data are linked to regional... 相似文献