High swell warnings in the Caribbean Islands during March 2008     

Jean-Michel Lefèvre 《Natural Hazards》2009,49(2):361-370

Long and high swells are dangerous for many islands located in the Tropics because they can generate large breakers and long run up associated with large set up when reaching the coast. Most of the time those islands do not experience large waves especially in usually protected areas, for instance, by coral reefs or wind protected. Long waves have the ability to reach such areas, thanks to wave set up, shoaling and bottom refraction. This article describes an example of such high swell events and its impact on the islands. The buoy network used by the French National Weather Service and all available satellite observations related to waves are presented together with numerical sea-state models used to issue early warnings.  相似文献   

ESR/U-series chronology of the Lower Palaeolithic palaeoanthropological site of Visogliano, Trieste, Italy     

Christophe Falgures  Jean-Jacques Bahain  Carlo Tozzi  Giovanni Boschian  Jean-Michel Dolo  Norbert Mercier  Hlne Valladas  Yuji Yokoyama 《Quaternary Geochronology》2008,3(4):390-398

The Visogliano shelter, in north-eastern Italy, is an important Middle Pleistocene occupation site where human remains were found together with an archaic lithic industry, including choppers, chopping tools and a few protobifaces. It is of utmost importance to try to document this period, when a second wave of settlement colonised Western Europe, carrying new flaking techniques and tools.Combined ESR/U-series analyses, integrated with biostratigraphical and environmental data, define a chronological frame for the layers from which the artefacts were unearthed. The lower levels, including human remains, can be dated to the 350–500 kyr time span, in agreement with micromammal and stratigraphical studies.These data make Visogliano one of the oldest palaeoanthropological sites in Italy, where human remains are directly associated with protobifaces, choppers and chopping tools. In Western Europe, Visogliano is contemporaneous to the G soil of the Arago Cave, France, with which it shares several similarities in faunal assemblages and radiometric data, and which contains human remains also. These data make Visogliano as one of the oldest sites in Europe where the Acheulian culture is observed.  相似文献   

Development of a Field Preconcentration/Elution Unit for Routine Determination of Dissolved Metal Concentrations by ICP-OES in Marine Waters: Application for Monitoring of the New Caledonia Lagoon     

Benjamin M. Moreton  Jean-Michel Fernandez  Mathieu B.D. Dolbecq 《Geostandards and Geoanalytical Research》2009,33(2):205-218

An iminodiacetate chelating resin was optimised for the rapid determination of Co, Cu, Fe, Mn and Ni in seawater. Using inexpensive, high-capacity, reusable cartridges allowed high flow rates of up to 25 ml min⁻¹. High preconcentration factors, of up to 500, were obtained in order to analyse samples using an ICP-OES. The requirement for a buffer was eliminated due to the high tolerance of the ICP-OES to interfering matrix elements, thereby further reducing the potential for contamination. Quantification limits in seawater were: Co = 6 ng l⁻¹, Cu = 8 ng l⁻¹, Fe = 6 ng l⁻¹, Mn = 5 ng l⁻¹ and Ni = 6 ng l⁻¹. The method was verified by the analysis of near shore seawater (CASS-4) and open ocean seawater (NASS-5) reference materials. In order to satisfy the high sampling demands using the iminodiacetate cartridges, a portable off-line preconcentration unit was developed for routine analysis. The multi-channel preconcentration unit, was capable of treating up to eight samples simultaneously with concentrating times as little as 30 minutes. The technique was also used to determine dissolved metals in fresh and interstitial waters. The technique has been successfully used in a number of environmental studies and impact assessments to evaluate the effects of mining on the New Caledonian lagoon.  相似文献   

Preliminary results about the stability of an intermediate water current   总被引：1，自引：0，他引：1  

Jean-Michel Baey  Dominique Renouard  Gabriel Chabert D'hieres 《Deep Sea Research Part I: Oceanographic Research Papers》1995,42(11-12)

Experiments were run on a 14 m diameter rotating platform to study the stability conditions for a constant volume flow rate current of intermediate water. The flow was introduced in a two-layer system initially at rest in solid body rotation, along the sidewall of the tank, and allowed freely to evolve. A sink collected the intermediate water and thus ensured that the free surface height was constant. Thus the upstream conditions were the rotation rate, the volume flow rate, the density and the initial width of the intermediate current, which was in geostrophic equilibrium when it left the source; i.e. its thickness along the wall at the source was fixed by this condition. The relevant parameters appear to be the Ekman and the Burger numbers. The data collected from the experiments are very consistent, and it appears that there were five typical flow regimes: (1) a stable current along the whole basin; (2) a series of cyclonic vortices attached to the outer edge of the current, with an upstream stable current; (3) a large cyclonic vortex attached to an anticyclonic instability; (4) dipoles shed from the current into the interior fluid; and (5) generation of lenses of intermediate water, similar to meddies. This last result shows that no topographical effect is required to generate such long-lived lenses, which then drift slowly upstream as the dipoles do.  相似文献   

Comparison of wind and wave measurements and models in the Western Mediterranean Sea   总被引：2，自引：0，他引：2  

Fabrice Ardhuin  Luciana Bertotti  Jean-Raymond Bidlot  Luigi Cavaleri  Valentina Filipetto  Jean-Michel Lefevre  Paul Wittmann 《Ocean Engineering》2007,34(3-4):526-541

We have hindcast the wind and wave conditions in the Mediterranean Sea for two one month periods. Four different meteorological models and three different wave models have been used. The results have been compared with satellite and buoy wind and wave observations.Several conclusions concerning both the instruments and the models have been derived. The quality of both wind and wave results has been assessed. Close to the coasts high resolution, nested wave models are required for sufficient reliability.A wave threshold analysis suggests a sufficient reliability only off the coast, with a substantial decrease for low wave heights.  相似文献   

Oceanic control of multidecadal variability in an idealized coupled GCM     

Quentin Jamet  Thierry Huck  Olivier Arzel  Jean-Michel Campin  Alain Colin de Verdière 《Climate Dynamics》2016,46(9-10):3079-3095

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Young (late Amazonian), near-surface, ground ice features near the equator, Athabasca Valles, Mars     

Devon M. Burr  Richard J. Soare  Jean-Michel Wan Bun Tseung 《Icarus》2005,178(1):56-73

A suite of four feature types in a ∼20 km² area near 10° N, 204° W in Athabasca Valles is interpreted to have resulted from near-surface ground ice. These features include mounds, conical forms with rimmed summit depressions, flatter irregularly-shaped forms with raised rims, and polygonal terrain. Based on morphology, size, and analogy to terrestrial ground ice forms, these Athabascan features are interpreted as pingos, collapsing pingos, pingo scars, and thermal contraction polygons, respectively. Thermal Infrared Mapping Spectrometer (THEMIS) data and geological features in the area are consistent with a sedimentary substrate underlying these features. These observations lead us to favor a ground ice interpretation, although we do not rule out volcanic and especially glaciofluvial hypotheses. The hypothesized ground ice that formed the mounds and rimmed features may have been emplaced via the deposition of saturated sediment during flooding; an alternative scenario invokes magmatically cycled groundwater. The ground ice implicit in the hypothesized thermal contraction polygons may have derived either from this flooding/ground water, or from atmospheric water vapor. The lack of obvious flood modification of the mounds and rimmed features indicates that they formed after the most recent flood inundated the area. Analogy with terrestrial pingos suggests that ground ice may be still extant within the positive relief mounds. As the water that flooded down Athabasca Valles emerged via a volcanotectonic fissure from a deep aquifer, any extant pingo ice may contain evidence of a deep subsurface biosphere.  相似文献   

Classical and Mg ii-selected damped Lyman α absorbers: impact on Ω_H i at z < 1.7     

Céline Péroux †  Jean-Michel Deharveng  Vincent Le Brun  Stefano Cristiani 《Monthly notices of the Royal Astronomical Society》2004,352(4):1291-1301

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Improved GRACE science results after adjustment of geometric biases in the Level-1B K-band ranging data   总被引：3，自引：1，他引：2  

Martin Horwath  Jean-Michel Lemoine  Richard Biancale  Stéphane Bourgogne 《Journal of Geodesy》2011,85(1):23-38

The GRACE (Gravity Recovery and Climate Experiment) satellite mission relies on the inter-satellite K-band microwave ranging (KBR) observations. We investigate systematic errors that are present in the Level-1B KBR data, namely in the geometric correction. This correction converts the original ranging observation (between the two KBR antennas phase centers) into an observation between the two satellites’ centers of mass. It is computed from data on the precise alignment between both satellites, that is, between the lines joining the center of mass and the antenna phase center of either satellite. The Level-1B data used to determine this alignment exhibit constant biases as large as 1–2 mrad in terms of pitch and yaw alignment angles. These biases induce non-constant errors in the Level-1B geometric correction. While the precise origin of the biases remains to be identified, we are able to estimate and reduce them in a re-calibration approach. This significantly improves time-variable gravity field solutions based on the CNES/GRGS processing strategy. Empirical assessments indicate that the systematic KBR data errors have previously induced gravity field errors on the level of 6–11 times the so-called GRACE baseline error level. The zonal coefficients (from degree 14) are particularly affected. The re-calibration reduces their rms errors by about 50%. As examples for geophysical inferences, the improvement enhances agreement between mass variations observed by GRACE and in-situ ocean bottom pressure observations. The improvement also importantly affects estimates of inter-annual mass variations of the Antarctic ice sheet.  相似文献   

The significance of stretching lineations in terms of progressive deformation and finite strain     

Benoit Ildefonse  Jean-Michel Caron 《Geodinamica Acta》2013,26(3):161-170

Abstract

For a given increment of deformation, stretching lineations can be defined either by old grains or by new grains.

Progressive strain accumulated in a matrix causes reorientation of old grains. The velocity field acting within a grain depends on the degree of non-coaxiality of the progressive strain in the matrix, and on the competence contrast between grain and matrix (e.g. Lister & Williams, 1983). Deformed populations of old grains do not systematically track the principal directions of finite stretch; this depends on the mechanical behavior of the grains. On the other hand, these populations may be good markers of finite strain magnitude, provided that the initial distribution is known.

In contrast, the statistical shape orientation distribution of population of new grains cannot be related in a simple way to the finite strain magnitude, but their preferred orientation is considered to be the best indicator of the principal directions of finite stretch.

An example is considered from the schistes lustrés near Kenestrelle (Val Chisone, Western Alps), where the observed mineral lineation is attributed to a late E-W stretching event in the alpine orogenic history.  相似文献