Lagrangian modelling of multi-dimensional advection-diffusion with space-varying diffusivities: theory and idealized test cases     

Darya Spivakovskaya  Arnold W. Heemink  Eric Deleersnijder 《Ocean Dynamics》2007,57(3):189-203

To efficiently simulate the advection-diffusion processes along and across density surfaces, we need to deal with a diffusivity tensor containing off-diagonal elements (Redi, J Phys Oceanogr, 12:1154–1158, 1982). In the present paper, the Lagrangian model, in case of a space-varying diffusivity tensor, is developed. This random walk model is applied for two idealized test cases for which the analytical solutions are known. Results of the testing show that the Lagrangian approach provides accurate and effective solutions of advection-diffusion problems for general diffusivity tensor.  相似文献   

The Sarikavak Tephra, Galatea, north central Turkey: a case study of a Miocene complex plinian eruption deposit     

Rolf Schumacher  Ulrike Mues-Schumacher  Vedat Toprak 《Journal of Volcanology and Geothermal Research》2001,112(1-4)

The Sarikavak Tephra from the central Galatean Volcanic Province (Turkey) represents the deposit of a complex multiple phase plinian eruption of Miocene age. The eruptive sequence is subdivided into the Lower-, Middle-, and Upper Sarikavak Tephra (LSKT, MSKT, USKT) which differ in type of deposits, lithology and eruptive mechanisms.The Lower Sarikavak Tephra is characterised by pumice fall deposits with minor interbedded fine-grained ash beds in the lower LSKT-A. Deposits are well stratified and enriched in lithic fragments up to >50 wt% in some layers. The upper LSKT-B is mainly reversely graded pumice fall with minor amounts of lithics. It represents the main plinian phase of the eruption. The LSKT-A and B units are separated from each other by a fine-grained ash fall deposit. The Middle Sarikavak Tephra is predominantly composed of cross-bedded ash-and-pumice surge deposits with minor pumice fall deposits in the lower MSKT-A and major pyroclastic flow deposits in the upper MSKT-B unit. The Upper Sarikavak Tephra shows subaerial laminated surge deposits in USKT-A and subaqueous tephra beds in USKT-B.Isopach maps of the LSKT pumice fall deposits as well as the fine ash at the LSKT-A/B boundary indicate NNE–SSW extending depositional fans with the source area in the western part of the Ovaçik caldera. The MSKT pyroclastic flow and surge deposits form a SW-extending main lobe related to paleotopography where the deposits are thickest.Internal bedding and lithic distribution of the LSKT-A result from intermittent activity due to significant vent wall instabilities. Reductions in eruption power from (partial) plugging of the vent produced fine ash deposits in near-vent locations and subsequent explosive expulsion of wall rock debris was responsible for the high lithic contents of the lapilli fall deposits. A period of vent closure promoted fine ash fall deposition at the end of LSKT-A. The subsequent main plinian phase of the LSKT-B evolved from stable vent conditions after some initial gravitational column collapses during the early ascent of the re-established eruption plume. The ash-and-pumice surges of the MSKT-A are interpreted as deposits from phreatomagmatic activity prior to the main pyroclastic flow formation of the MSKT-B.  相似文献   

Gravimetric deflections of the vertical in high mountains determined by free-air anomalies     

K. Arnold 《Journal of Geodesy》1962,36(1):73-74

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K. Arnold 《Journal of Geodesy》1968,42(1):97-101

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NOAA卫星探测数据对B-模式分析预报系统性误差的影响   总被引：1，自引：1，他引：1       下载免费PDF全文

王宗皓  毛建平  黄继红  A. Gruber  A. Thomasell  T. S. Chen 《Acta Meteorologica Sinica》1993,51(1):21-33

本文报告极轨气象卫星探测数据对B-模式的海平面气压场预报和500hPa高度预报的系统性误差的影响.主要结果是:(1)B-模式预报海平面气压的强度偏弱,即高压系统太低,低压太高;(2)500hPa高度预报的系统性误差情况不如海平面气压场误差情况明显.但也能发现槽区的高度预报不够低,而脊区的高度预报不够高;(3)应用卫星数据对B-模式分析预报系统的预报有正作用,对海洋上的地面低压和500hPa槽区附近的系统性误差有明显减小,但对其它地区天气系统预报的正负影响参差不齐,其作用难下结论。  相似文献   

An evaluation of the apparent dissociation constants of carbonic acid in seawater     

Taro Takahashi  Peter Kaiteris  Wallace S. Broecker  Arnold E. Bainbridge 《Earth and Planetary Science Letters》1976,32(2):458-467

The internal consistency of five sets of apparent dissociation constants of carbonic acid in seawater obtained by Buch (1951), Lyman (1956), Edmond and Gieskes (1970), Hansson (1973) and Mehrbach et al. (1973) have been tested using the GEOSECS Atlantic data for the total alkalinity, the total CO₂ concentration and the partial pressure of CO₂. As a measure of the consistency for each of the five sets of the dissociation constants with the data, the 77 measured values of the partial pressure of CO₂ have been compared with those calculated from the alkalinity and total CO₂ values determined for these samples. It has been found that: (1) the apparent dissociation constants of Lyman (1956), Hansson (1973) and Mehrbach et al. (1973) appear to be internally consistent with the data, whereas those of Buch (1951) and of Edmond and Gieskes (1970) appear to be markedly inconsistent with the GEOSECS data; and (2) on the basis of a statistical analysis of the data grouped in three temperature ranges, the dissociation constants of Lyman (1956) and of Mehrbach et al. (1973) appear to be most satisfactory.  相似文献   

Aspèct Isotopique δ34S‰ d'un Processus de Mobilisation et de Réconcentration de Sulfures en Amas à Structure Filoniénne     

M. Arnold  J. Guha 《Mineralium Deposita》1980,15(3):361-381

Résumé Beaucoup de minéralisations sulfurées filoniennes sont encaissées dans des formations qui contiennent les mêmes éléments mais à l'état disséminé. En ce cas, on admet généralement que ces éléments ont été mobilisés et reconcentrés dans des structures tectoniques distensives. Le même mécanisme peut encore être envisagé quand de telles minéralisations sont spatialement éloignées des formations réservoirs de soufre et de métaux. Connaissant la composition isotopique des sulfures filoniens ainsi que les conditions physico-chimiques de leur dépôt il est possible de calculer la valeur théorique de la composition isotopique des sulfures du réservoir. Celle-ci peut alors être comparée aux compositions isotopiques effectives des sulfures provenant des différents réservoirs potentiels dans le but de déterminer quel est le réservoir de soufre et de métaux le plus probable. Une série d' analyses isotopiques a été entreprise sur les sulfures des minéralisations de Henderson et de Campbell Chibougamau Main Mine. Ces minéralisations du type Cu-Au sont en relation spatiale avec des zones de cisaillement développées dans le complexe du Lac Doré. La composition isotopique moyenne de la pyrite de Henderson vaut –2.9. Cette valeur est très proche de la moyenne des compositions isotopiques de la pyrite de Chibougamau Main Mine (–2.8). La composition isotopique moyenne de la chalcopyrite de Henderson est de –3.2. En se fondant sur le modèle thermodynamique proposé d'une part, sur les compositions isotopiques de la pyrite et de la chalcopyrite d'une minéralisation stratiforme encaissée dans le réservoir présumé d'autre part, il est possible de conclure que les sulfures des minéralisations filoniennes ont été remobilisés des formations volcano-sédimentaires.

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Many sulphide concentrations occur in formations containing the same elements in a disseminated state. It is generally admitted that these elements may be mobilised and reconcentrated into open spaces. The same mechanism has been envisaged in cases where vein deposits are spatially separated from the rocks which acted as a reservoir for sulphur and metals. Knowing the isotopic composition of the sulphide from the veins as well as the physico-chemical conditions of deposition, the theoretical value of the sulphur isotopic composition of the reservoir can be calculated and this can be compared with the values of the sulphides from the different reservoirs in order to indicate the most likely source. A series of isotopic analyses were untertaken on the sulphides from Henderson and Campbell Chibougamau Main Mines. These two deposits belong to the Cu-Au type of mineralisation associated with shear zones within the Lac Doré Complex. The mean isotopic composition of pyrite at Henderson is –2.9 which is close to the mean values measured at Campbell Chibougamau Main Mine (–2.8). The mean value of the chalcopyrite from the Henderson Mine is –3.2. Different possibilities concerning the provencance of sulphur are discussed. Based on existing thermodynamic model and on a set of new isotopic datas (pyrite and chalcopyrite) from volcanogenic mineralisation, it is possible to conclude that measured values correspond to mobilised volcanogenic sulfur.

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Neuere Veröffentlichungen     

Arnold Schumacher  Hans Ermel  G. Dietrich 《Ocean Dynamics》1954,7(5-6):203-207

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Plio-Pleistocene transpressional reactivation of Paleozoic and Paleogene structures in the Rhine-Bresse transform zone (northern Switzerland and eastern France)     

M.?GiamboniEmail author  K.?Ustaszewski  S.?M.?Schmid  M.?E.?Schumacher  A.?Wetzel 《International Journal of Earth Sciences》2004,93(2):207-223

Pliocene to recent uplift and shortening in the southern Rhinegraben is documented by deformation of Pliocene fluvial gravels, deposited on a nearly planar surface, as well as by progressive deflection and capture of rivers. This deformation is suggested to result from thick-skinned tectonic movements as evidenced by observations on seismic records, which demonstrate a spatial coincidence between en-échelon anticlines at the surface and faults located in the crystalline basement. These findings contradict the often invoked thin-skinned tectonism in the recent tectonic history of the Rhinegraben. In particular the transfer zone between the Rhinegraben and the Bressegraben is very suitable for reactivation under the present day stress field. Thick-skinned reactivation of faults in the basement is also expressed by focal plane mechanisms of recent earthquakes showing strike-slip- rather than reverse faulting characteristics. This is of importance for the densely populated and industrialised southern Rhinegraben, previously affected by large earthquakes in historical times (e.g. Basel 1356).  相似文献   

A GIS-Coupled Hydrological Model System for the Watershed Assessment of Agricultural Nonpoint and Point Sources of Pollution   总被引：9，自引：0，他引：9  

Mauro Di Luzio  Raghavan Srinivasan  Jeffrey G Arnold 《Transactions in GIS》2004,8(1):113-136

This paper introduces AVSWAT, a GIS based hydrological system linking the Soil and Water Assessment Tool (SWAT) water quality model and ArcView“ Geographic Information System software. The main purpose of AVSWAT is the combined assess‐ment of nonpoint and point pollution loading at the watershed scale. The GIS component of the system, in addition to the traditional functions of data acquisition, storage, organization and display, implements advanced analytical methods with enhanced flexibility to improve the hydrological characterization of a study watershed. Intuitive user friendly graphic interfaces, also part of the GIS component, have been developed to provide an efficient interaction with the model and the associated parameter databases, and ultimately to simplify water quality assessments, while maintaining and increasing their reliability. This is also supported by SWAT, the core of the system, a complex, conceptual, hydrologic, continuous model with spatially explicit parameterization, building upon the United State Department of Agriculture (USDA) modeling experience. A step‐by‐step example application for a watershed in Central Texas is also included to verify the capability and illustrate some of the characteristics of the system which has been adopted by many users around the world.  相似文献