Characterization of Atmospheric Ekman Spirals at Dome C,Antarctica     

Jean-François Rysman  Alain Lahellec  Etienne Vignon  Christophe Genthon  Sébastien Verrier 《Boundary-Layer Meteorology》2016,160(2):363-373

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⁸⁷Rb⁸⁷Sr chronology of H chondrites: Constraint and speculations on the early evolution of their parent body     

Jean-François Minster  Claude J. Allègre 《Earth and Planetary Science Letters》1979,42(3):333-347

A precise⁸⁷Rb-⁸⁷Sr whole-rock isochron for H chondrites and an internal isochron for Tieschitz (H3) have been determined. The age and⁸⁷Sr/⁸⁶Sr initial ratio of the whole rocks are4.52 ± 0.05 b.y. and0.69876 ± 0.00040(λ(⁸⁷Rb) = 1.42 × 10^?11yr^?1). For Tieschitz, whereas handpicked separates plot on a well-defined line, heavy liquid separates scatter in the⁸⁷Rb/⁸⁶Sr vs.⁸⁷Sr/⁸⁶Sr diagram. Leaching experiments by heavy liquids indicate that they might have a sizeable effect on Tieschitz minerals. The age and⁸⁷Sr/⁸⁶Sr initial ratio as determined by handpicked separates are4.53 ± 0.06 b.y. and0.69880 ± 0.00020, indistinguishable from the whole-rock isochron.These results are interpreted as “primitive isochrons” dating the condensation of chondrites from the solar nebula. The best value of this event is given by joining both isochrons together at4.518 ± 0.026 b.y. and⁸⁷Sr/⁸⁶Sr= 0.69881 ± 0.00016. The near identity of this initial ratio with the one of Allende white inclusions argues in favor of a sharp isochronism of condensation from a⁸⁷Sr/⁸⁶Sr homogeneous nebula. Data from Guaren?a [11] and Richardton [48] are interpreted as secondary internal isochrons, 100 m.y. after the condensation of the whole rocks.The data are then used to constrain a thermal evolution model of the H chondrite parent body. This body might have a 150–175 km radius, and might have been heated by²⁶Al. An²⁶Al/²⁷Al ratio of 4–6 × 10^?6 is enough for heating such a body. Further tests for this model are proposed.  相似文献   

A numerical simulation of the surface water budget during HAPEX-MOBILHY     

Jean-François Mahfouf 《Boundary-Layer Meteorology》1990,53(3):201-222

A simple land surface parameterization scheme previously validated at the daily time scale is studied for monthly periods using the HAPEX-MOBILHY data set. For a set of six locations, the scheme reproduces with good accuracy two components of the surface water budget (evaporation and soil moisture depletion) when the observed rainfall rate at the ground surface is specified. For two sites where the superficial soil moisture content has been measured, the model provides a reasonable evolution for this quantity. The validation has been completed by examining the screen-level temperature and relative humidity. The agreement with observations is fair, except when the local properties of the site strongly differ from those of the surroundings.  相似文献   

Modeling the ionospheric electron content for the correction of altimetric measurements   总被引：1，自引：0，他引：1  

Françoise Foucher  Jean-François Ciavaldini 《Pure and Applied Geophysics》1991,135(3):475-491

The TOPEX-POSEIDON oceanographic satellite (due to be launched in 1992) will proceed to high accuracy altimetric measurements of the sea surface. Since the altimeter signals will propagate through the ionosphere, they will be retarded with respect to their free-space propagation delay. As a result, the measured altitude will exhibit an apparent lengthening which must be considered. In order to correct this effect, the ionosphere total electron content (TEC) beneath the satellite has to be known. This paper addresses the problem of determining the TEC form Doppler measurements performed on telemetric signals propagating between the satellite and the ground stations of the DORIS positioning system. This is an inverse problem which, in general, does not admit a single-valued solution. Physical observations of the ionophere lead us to assume that the TEC along each half-revolution is regular such that we can select an appropriate solution. This solution is approximated by cubic splines. The computed results are compared to simulation results, based on the Bent ionospheric model and seem to be particularly promising.  相似文献   

First direct geodetic link between Europe,Africa and South America with a multi station VLBI array     

Gérard Petit  Claude Boucher  Jean-François Lestrade 《Journal of Geodesy》1989,63(4):331-341

The first geodetic experiment tying Europe, Africa and South-America was realized in July 1985 by Very Long Baseline Interferometry with a network of 5 radiotelescopes. TheVLBI technique and data analysis are presented, with special emphasis on the ionosphere modeling because of its importance in this particular experiment. Comparisons of the results with other geodetic information confirm the achievement of decimetric accuracy.  相似文献   

Response of hurricane-type vortices to global warming as simulated by ARPEGE-Climat at high resolution   总被引：1，自引：0，他引：1  

Fabrice Chauvin  Jean-François Royer  Michel Déqué 《Climate Dynamics》2006,27(4):377-399

Atlantic hurricanes and their sensitivity to anthropogenic warming are investigated using very high (0.5°×0.5° over the Atlantic domain) resolution global simulations. The ARPEGE-Climat variable resolution grid demonstrates its usefulness in regional climate studies since resolution can be multiplied by a factor of 2.5 over the domain of interest compared to a uniform grid, for a similar computer cost. The question of hurricane characteristics dependence on anthropogenic warming is tackled trough the implementation of a tracking method. Changes in the total number, as well as locations, of hurricanes appear to depend more on sea surface temperature (SST) spatial patterns anomaly than Atlantic mean intensity, essentially through the change in large scale vertical wind shear. A uniform SST anomaly forcing produces increased and eastward shifted systems while a spatially contrasted anomaly leads to a decrease. Comparison between cyclogenesis density calculated from tracking or large scale combined variables (as a modified Gray parameter) brings some confidence in the use of the latter to investigate low resolution simulations. Mean hurricane dynamical characteristics are weakly changed by the warming but precipitation core and latent heat flux are enhanced in all scenarios.  相似文献   

Les surfaces boisées à l'échelle de la planète : usages conjoints pour la séquestration du carbone et la production d'énergie     

Anne Prieur  Jean-François Bonnet  Michel Combarnous 《Comptes Rendus Geoscience》2004,336(15):1323-1335

The role of forest ecosystems in the regulation of greenhouse effect at the global scale is developed here, from two points of view, sometimes considered as opposed: carbon storage and wood production for energy. A nomenclature is proposed to understand all the various mechanisms implied in carbon storage. A comparison is made between the effects on carbon emissions of storage alone and storage with wood fuel production. Use of wood energy is proved to be a ‘bonus’ that could optimise, in the middle and long terms, the use of fossil fuel reserves. To cite this article: A. Prieur et al., C. R. Geoscience 336 (2004).  相似文献   

The contribution of marine magnetics in the Gulf of Saint-Malo (Brittany,France) to the understanding of the geology of the North Armorican Cadomian belt     

Jean-François Oehler  Marie-Françoise Lequentrec-Lalancette 《Comptes Rendus Geoscience》2019,351(1):1-9

Marine magnetic data extracted from the geophysical database of the SHOM (the French Hydrographic and Oceanographic Service) offer a first overview of the magnetic offshore environment in the Gulf of Saint-Malo (Brittany, France). Their cross-interpretation with available geological and geophysical knowledge provides a new land and sea model of the western part of the Late Proterozoic North Armorican Cadomian belt. In particular, marine data exhibit relatively intense and heterogeneous magnetic signatures, mainly interpreted as the offshore prolongation of plutonic, volcanic, and metamorphic geologic formations recognized onshore. Imprints of major faults well known on land can be inferred at sea from discontinuities and shifting of magnetic anomalies or followed by high-resolution bathymetry. An impressive and dense dolerite dyke swarm propagated on more than 50 km from the coast seaward. Dykes are characterized by both 1-km-deep and less than 50-m-deep superficial magnetic responses, suggesting the existence of deeply rooted super dykes to which individual small-scale structures are connected.  相似文献   

Protracted,coeval crust and mantle melting during Variscan late-orogenic evolution: U–Pb dating in the eastern French Massif Central     

Laurent  Oscar  Couzinié  Simon  Zeh  Armin  Vanderhaeghe  Olivier  Moyen  Jean-François  Villaros  Arnaud  Gardien  Véronique  Chelle-Michou  Cyril 《International Journal of Earth Sciences》2017,106(2):421-451

International Journal of Earth Sciences - The late stages of the Variscan orogeny are characterized by middle to lower crustal melting and intrusion of voluminous granitoids throughout the belt,...  相似文献   

A discontinuous finite element baroclinic marine model on unstructured prismatic meshes     

Sébastien Blaise  Richard Comblen  Vincent Legat  Jean-François Remacle  Eric Deleersnijder  Jonathan Lambrechts 《Ocean Dynamics》2010,60(6):1371-1393

We describe the space discretization of a three-dimensional baroclinic finite element model, based upon a discontinuous Galerkin method, while the companion paper (Comblen et al. 2010a) describes the discretization in time. We solve the hydrostatic Boussinesq equations governing marine flows on a mesh made up of triangles extruded from the surface toward the seabed to obtain prismatic three-dimensional elements. Diffusion is implemented using the symmetric interior penalty method. The tracer equation is consistent with the continuity equation. A Lax–Friedrichs flux is used to take into account internal wave propagation. By way of illustration, a flow exhibiting internal waves in the lee of an isolated seamount on the sphere is simulated. This enables us to show the advantages of using an unstructured mesh, where the resolution is higher in areas where the flow varies rapidly in space, the mesh being coarser far from the region of interest. The solution exhibits the expected wave structure. Linear and quadratic shape functions are used, and the extension to higher-order discretization is straightforward.  相似文献