A parameterization of the stable atmospheric boundary layer     

Yves Delage 《Boundary-Layer Meteorology》1988,43(4):365-381

Two formulations of the stable atmospheric boundary layer are proposed for use in weather forecasting or climate models. They feature the log-linear profile near the surface, but are free from the associated critical Richardson number. The diffusion coefficients in the Ekman layer are a natural extension of the surface layer. They are locally determined using wind shear in one case and turbulent kinetic energy in the other. The parameterizations are tested in a one-dimensional model simulating the evolution of the nocturnal boundary layer with and without radiative cooling. Both formulations give very similar results, except near the top of the boundary layer where the transition to the free atmosphere is smoother with the wind shear formulation. A distinctive feature of these schemes is that they retain their simulating skill when resolution is reduced. This is verified for a wide range of situations. In practice, this means that there is no need for a large-scale model to have a level below 50 m or so.  相似文献   

Contribution à l'étude des litages pegmatitiques: l'exemple de la pegmatite de Covide (Nord-Portugal)     

Yves Gouanvic  Claude Gagny 《International Journal of Earth Sciences》1987,76(1):125-135

Résumé La pegmatite de Covide (Nord-Portugal) fournit un nouvel exemple de litage à quartz-albite-feldspath potassique. Son étude conduit à proposer un modèle de pétrogenèse magmatique faisant intervenir des processus de double diffusion dans un gradient de température. Ces processus provoquent la formation simultanée et périodique de niveaux millimétriques d'albite, en »planchers flottants« horizontaux. Chaque cellule, phénomène-unité du litage compris entre deux niveaux planchers successifs, évolue ensuite en système clos par cristallisation orientée centripète. L'organisation litée est acquise en milieu magmatique liquide.

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The Covide pegmatite, (Northern Portugal), exhibit a new example of K-feldspar, Albite, quartz layering. The present study leads to propose a magmatic petrogenetit model, with double diffusive processe in temperature gradient allowing the simultaneous growth of millimetric and horizontal »floating layers« of albite. Each cell, unit-phenomenon between two consecutive boundary layers, evolves in closed system with a centripetal, oriented crystallization. The layered organisation is obtaind in the magmatic liquid medium.

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Zusammenfassung Der Pegmetit aus Covide (Nordportugal) stellt ein neues Beispiel für Quarz-Albitfeldspat Wechsellagerung dar. Seine Untersuchung führt zu einem magmatischen Petrogenesemodell, bei dem Prozesse der Doppeldiffusion in einem Temperaturgefälle intervenieren. Diese Prozesse bewirken die gleichzeitige und periodische Bildung von millimeterdicken Albitflächen in horizontalen »schwimmenden Flächen«. Jede Zelle, die ein Phänomen der Einheit der Anlagerungsfläche zwischen zwei aufeinanderfolgenden Flächenlagen ist, entwickelt sich schlie\lich durch zentripetale Kristallisierung zu einem geschlossenen System. Die schichtweise Anordnung erfolgt im flüssigen magmatischen Milieu.

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Statistical models for the estimation of net phosphorus sedimentation in lakes   总被引：2，自引：0，他引：2  

Yves T. Prairie 《Aquatic Sciences - Research Across Boundaries》1989,51(3):192-210

The empirical adequacy of four phosphorus mass-balance models is evaluated with respect to how the prediction error variance of the corresponding net sedimentation parameters is propagated in the steadystate equations. Using the criterion of minimum propagation error variance (PEV), different groups of lakes can be distinguished for which different empirical equations are used to predict net phosphorus sedimentation. The classification reduced prediction error significantly and also reflected different patterns of sedimentation. Application of this criterion to time-series of individual lakes shows that it is possible to determine a priori whether net annual sedimentation will be better correlated to the annual loading or to the lake content. The correlations depended also on the load/lake content ratio, suggesting that net sedimentation is best viewed as the sum of the partial sedimentation of the load and of the partial sedimentation of the lake content. On average, 25% of the load and 18% of the lake content are sedimented annually. Viewing net phosphorus sedimentation as a function of both the load and the lake content can also explain and predict the well-known cross-sectional correlation between phosphorus retention and water residence time.  相似文献   

Intermediate tectonic pattern and hydrodynamic process deduced from audiomagnetotelluric investigations on the volcanic island of Mayotte (Comores Archipelago)     

Rgis Ballestracci  Jacques Nougier  Yves Benderitter 《Tectonophysics》1985,115(1-2)

Audiomagnetotelluric soundings were carried out on the volcanic island of Mayotte (Comores Archipelago). The field method and data are described and discussed. All the sounding cross sections show coherent curves with a high conductive layer between 100 and 200 m. depth. This layer is considered to be a fluctuating water table zone correlated to yearly climatic changes under tropical weathering processes. Dipping and sudden level variations are linked to tectonic volcanic features and are the visualization of a block faulting system of the primitive basaltic shield, a consequence of a distensive phase possibly connected with the collapse of the western flank of the volcano. Piano-key panels are the typical sub-surface style and the guide-line for any water prospection on the volcano and the activity of the island water transfer system.  相似文献   

Fission-track dating of glass inclusions in volcanic quartz     

Denis Vincent  Roberto Clocchiatti  Yves Langevin 《Earth and Planetary Science Letters》1984,71(2):340-348

We have extended fission-track dating techniques to volcanic pyroclastic rocks, using quartz-bearing uranium-rich glass inclusions. We use both the glass itself and the surrounding quartz as track detectors, the latter having a much higher resetting temperature. We can thus derive the age of the last low-temperature thermal event, as well as that of the most recent deposition of quartz on the walls of the inclusions. This method has been applied to a Sardinian sample and to a Moroccan Precambrian sample.  相似文献   

Sur la structure,l'âge et l'origine des « brèches de Bosmendiette » (Pyrénées-Atlantiques)     

Joseph Canérot  Jacques Bauer  Michel Bilotte  Chantal Bourdillon  Jean-Paul Colin  Elie-Jean Debroas  Françoise Magniez  Francis Mediavilla  Yves Ternet 《Comptes Rendus Geoscience》2004,336(10):951-958

By us considered as Albo-Aptian in age and generated through halokinetic processes, the Bosmendiette breccias have been recently interpreted as Selandian (Palaeocene) globigerine-bearing sediments deposited in sub-marine canyons within a deep trough crossing the Pyrenees, from the Mediterranean Sea to the Atlantic Ocean. These breccias are really azoic in their lower part and contain a scarce microfauna including radolarians and benthic foraminifera at the top of the formation. They are unconformably covered by the Urgo-Aptian limestones and marls and indicate, under opening marine conditions, Lower Cretaceous collapse movements and northward sliding of the Jurassic slumped cover, related to the growth of the Béloscare–Apoura diapir. To cite this article: J. Canérot et al., C. R. Geoscience 336 (2004).  相似文献   

Three millennia of directional variation of the Earth’s magnetic field in western Europe as revealed by archeological artefacts     

Yves Gallet  Agnès GeneveyMaxime Le Goff 《Physics of the Earth and Planetary Interiors》2002,131(1):81-89

Directional secular variation of the geomagnetic field over the last 2000 years has been defined in western Europe from numerous archeomagnetic studies. However, the number of archeomagnetic results for older periods is much more limited. For this reason, we present new data obtained from fired archeological structures found in two French sites (Loupiac and Aspiran) dated within the first millennium b.c. (latest Bronze-earliest Iron Age transition, ∼850-700 b.c. and Iron Age, ∼525-475 b.c., respectively). From a compilation of archeomagnetic results from western Europe (Great Britain, Italy and France) and northern Africa (Tunisia), we propose a directional secular variation curve for western Europe that covers the entire first millennium b.c. This curve exhibits a large clockwise motion with rapid changes during the first half of the millennium, while the last four centuries b.c. are characterized by weak variations.  相似文献   

Datation UPb sur zircons des dolérites tholéiitiques pyrénéennes (ophites) à la limite Trias–Jurassique et relations avec les tufs volcaniques dits « infra-liasiques » nord-pyrénéens     

Philippe Rossi  Alain Cocherie  C.Mark Fanning  Yves Ternet 《Comptes Rendus Geoscience》2003,335(15):1071-1080

The tholeiitic doleritic magmatism (ophites) in the Aspe valley of the Pyrenees has been dated on the Triassic–Jurassic boundary (199±2 Ma) by the UPb method on zircon (SHRIMP). Emplacement of the ophites was probably synchronous with that of the earliest ‘Infraliassic’ Ségalas tuffs. The ophites are thus related to the Central Atlantic Magmatic Province (CAMP) whose emplacement linked with the fracturing of Pangea, preceded the opening of the Atlantic Ocean. To cite this article: P. Rossi et al., C. R. Geoscience 335 (2003).  相似文献   

Study Of `Soft' Night-Time Surface-Layer Decoupling Over Forest Canopies In A Land-Surface Model     

Yves Delage  Paul A. Bartlett  J. Harry McCaughey 《Boundary-Layer Meteorology》2002,103(2):253-276

The cause of a night-time land-surface model cold bias over forest canopies at threedifferent sites is studied in connection with various formulations of turbulent transferand the phenomenon of decoupling between the surface and the boundary layer. Themodel is the Canadian Land Surface Scheme (CLASS), a leading internationally knownmodel that has been tested over a variety of instrumented sites. The bias was first attributed to a deficient turbulent transfer and a few formulations were compared. One formulation is the classical log-linear profile with a sharp cut-off of the fluxes at a critical Richardsonnumber around 0.2, while in the other ones the flux decreases less rapidly with increasingstatic stability. While the surface-layer formulations have an impact on the modelled canopy temperature, other causes were found for the negative bias. The CLASS model neglected the heat capacity of the air trapped inside the canopy and its inclusion multiplied theeffective heat capacity of the canopy, by a factor ranging from 2.3 to 3.4 for the canopies studied, and reduced the error. A correction was also made to the air specific humidity at canopy level and the topsoil thermal conductivity was changed from that of organic matter to that of mineral soil. With these modifications, and using the incoming longwave radiative flux instead of the net longwave flux, the bias almost completely disappeared. Using ascheme with more heat transfer at large static stability, obtained by assuming that thefluxes decrease in magnitude with height in the surface layer, reduced the original biaswhile using the log-linear formulation amplified the cold bias. The impact of the turbulent transfer formulations is much reduced when they are applied to model runs in which the other above modifications have been made.The phenomenon of decoupling is presented and its understanding is complementedwith the new notions of `hard' versus `soft' decoupling and complete versus incompletedecoupling, depending on the impact decoupling has on the model and on the effectiveness of the model in achieving the decoupling. The geostrophic wind speed is a determiningfactor in separating cases of hard decoupling (rare) from the soft cases (frequent) while the completeness of the decoupling primarily depends on the form of the turbulent transfer curve as a function of static stability.  相似文献   

Milieux coralliens du Dogger près de Betioky (Madagascar) : la fin d'une exceptionCorallian meadows in the Dogger near Betioky (Madagascar): the end of an exception     

Bernard Lathuilire  Yves Almeras  Vincent Huault  Frdric Bouticourt  La-Jacqueline Raharijaona-Raharison 《Comptes Rendus Geoscience》2002,334(16)

Corallian outcrops of the Dogger in the Betioky area (Madagascar) have been previously interpreted as barrier reefs or atolls involved in a large carbonate platform. This statement appeared exceptional for these times. A field study demonstrates that, in fact, they are only sparse solitary or colonial corals, whose growth occurred with some difficulty. They developed in meadows strongly marked by terrigenous inputs, in a subsiding context, and during brief episodes favourable to the genesis of ooids. To cite this article: B. Lathuilière et al., C. R. Geoscience 334 (2002) 1169–1176.  相似文献