The ‘MESOGERS 84’ experiment: A report     

A. Weill  C. Mazaudier  F. Baudin  C. Klapisz  F. Leca  M. Masmoudi  D. Vidal Madjar  R. Bernard  O. Taconet  B. S. Gera  A. Sauvaget  A. Druilhet  P. Durand  J. Y. Caneil  P. Mery  G. Dubosclard  A. C. M. Beljaars  W. A. A. Monna  J. G. Van Der Vliet  M. Crochet  D. Thomson  T. Carlson 《Boundary-Layer Meteorology》1988,42(3):251-264

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The partitioning of Fe and Mg between olivine and carbonate and the stability of carbonate under mantle conditions   总被引：4，自引：1，他引：4  

John A. Dalton  Bernard J. Wood 《Contributions to Mineralogy and Petrology》1993,114(4):501-509

We have investigated the effect of Fe on the stabilities of carbonate (carb) in lherzolite assemblages by determining the partitioning of Fe and Mg between silicate (olivine; ol) and carbonates (magnesite, dolomite, magnesian calcite) at high pressures and temperatures. Fe enters olivine preferentially relative to magnesite and ordered dolomite, but Fe and Mg partition almost equally between disordered calcic carbonate and olivine. Measurement of K _d (X _Fe ^carb X _Mg ^ol /X _Fe ^ol X _Mg ^carb ) as a function of Fe/ Mg ratio indicates that Fe–Mg carbonates deviate only slightly from ideality. Using the regular solution parameter for olivine W _FeMg ^ol of 3.7±0.8 kJ/mol (Wiser and Wood 1991) we obtain for (FeMg)CO₃ a W _FeMg ^carb of 3.05±1.50 kJ/mol. The effect of Ca–Mg–Fe disordering is to raise K _d substantially enabling us to calculate W _CaMg ^carb -W _CaFe ^carb of 5.3±2.2 kJ/mol. The activity-composition relationships and partitioning data have been used to calculate the effect of Fe/Mg ratio on mantle decarbonation and exchange reactions. We find that carbonate (dolomite and magnesian calcite) is stable to slightly lower pressures (by 1 kbar) in mantle lherzolitic assemblages than in the CaO–MgO–SiO₂(CMS)–CO₂ system. The high pressure breakdown of dolomite + orthopyroxene to magnesite + clinopyroxene is displaced to higher pressures (by 2 kbar) in natural compositions relative to CMS. CO₂. We also find a stability field of magnesian calcite in lherzolite at 15–25 kbar and 750–1000°C.  相似文献   

The “geo” of United States national strategy     

Bernie Grover  M. Baruch Bernard 《GeoJournal》1993,31(2):141-148

The paper discusses the geo dimensions of the new world order, with particular emphasis on the increasing role of geoeconomics, and its impact on US national strategy. While the paper uses the US experience to illustrate the growing importance of geoeconomic considerations, the issues raised have direct bearing on many other nations throughout the world.US post Cold War strategy is determined by its three geo challenges. The most important is the geoeconomic challenge caused by the tri-polar division of the world along trading bloc lines, instant global communication and other technologies overcoming the constraints of physical geography, transnational corporations (TNCS) that are becoming supranational in character, and the emergence of a well educated global labor force. The geopolitical challenge is characterized by America's declining relative economic power and its traditional military allies having become economic competitors, while religious, ethnic, and regional tensions threaten its global interests. The third challenge is the military geography issue of effectively projecting power over distance, within the constraints of greatly reduced budgets and loss of overseas bases.  相似文献   

Application of objective analysis to metallic traces in the atmospheric aerosol     

Christophe Migon  Bernard Gentili 《Journal of Atmospheric Chemistry》1993,16(3):277-284

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Influence of bottom topography roughness on the jet and inertial recirculation of a mid-latitude gyre     

Bernard Barnier  Christian Le Provost 《Dynamics of Atmospheres and Oceans》1993,18(1-2)

Several numerical experiments are conducted to examine the influence of mesoscale, bottom topography roughness on the inertial circulation of a wind-driven, mid-latitude ocean gyre. The ocean model is based on the quasi-geostrophic formulation, and is eddy-resolving as it features high vertical and horizontal resolutions (six layers and a 10 km grid). An antisymmetrical double-gyre wind stress curl forces the baroclinic modes and generates a strong surface jet. In the case of a flat bottom, inertia and inverse energy cascade force the barotropic mode, and the resulting circulation features strong, barotropic, inertial gyres. The sea-floor roughness inhibits the inertial circulation in the deep layers; the barotropic component of the flow is then forced by eddy-topography interactions, and its energy concentrates at the scales of the topography. As a result, the baroclinicity of the flow is intesified: the barotropic mode is reduced with regard to the baroclinic modes, and the bottom flow (constrained by the mesoscale sea-floor roughness) is decoupled from the surface flow (forced by the gyre-scale wind). Rectified, mesoscale bottom circulation induces an interfacial form stress at the thermocline, which enhances horizontal shear instability and opposes the eastward penetration of the jet. The mean jet is consequently shortened, but the instantaneous jet remains very turbulent, with meanders of large meridional extent. The sea-floor roughness modifies the energy pathways, and the eddies have an even more important role in the establishment of the mean circulation: below the thermocline, rectification processes are dominant, and eddies transfer energy toward permanent mesoscale circulations strongly correlated with topography, whereas above the thermocline mean flow and eddy generation are influenced by the mean bottom circulation through interfacial stress. The topography modifies the vorticity of the barotropic and highest baroclinic modes. Vorticity accumulates at the small topographic scales, and the vorticity content of the highest modes, which is very weak in the flat-bottom case, increases significantly. Few changes occur in surface-intensified modes. In the deep layers of the model, the inverse correlation between relative vorticity and topography at small scales ensures the homogenization of the potential vorticity, which mainly retains the largest scales of the bottom flow and the scale of β.  相似文献   

Volatile fluxes from volcanoes   总被引：1，自引：0，他引：1  

Marie-Françoise Le Cloarec  Bernard Marty 《地学学报》1991,3(1):17-27

Volatile fluxes from Mid Ocean Ridge (MOR) and subaerial volcanism have been estimated or re-evaluated using several natural tracers-³He, ²¹⁰Po, SO₂-and chemical ratios of volatile species in lavas and volcanic gases.
These estimates confirm the net predominance of anthropogenic fluxes over volcanic fluxes for CO₂, SO₂ and trace metals.
They also suggest that, while most of the volatiles transferred during MOR volcanism come from the mantle, volatiles stored at the surface of the Earth supply an appreciable fraction of subaerial fluxes and can be the dominant source for some of them.
The surface inventory of volatile species cannot result from steady-state degassing with constant rate and needs much greater fluxes in the past or other volatile supply processes. This inventory is the result of several of the following processes: capture of the solar nebula and its subsequent partial escape, impact degassing of accreting bodies, and, from Archean to present mantle, degasssing through volcanism and associated phenomena, with recycling into the mantle through subduction.  相似文献   

Characteristics of the seismic attenuation in two tectonically active zones of Southern Europe     

E. Del Pezzo  S. De Martino  F. De Miguel  J. Ibanez  A. Sorgente 《Pure and Applied Geophysics》1991,135(1):91-106

The seismic energy attenuation in the frequency range of 1–18 Hz was studied in the two tectonically active zones of Irno Valley (Southern Italy) and Granada Basin (South-East Spain). Data were recorded by short period vertical components seismographs for low-magnitude local earthquakes. The method of coda waves, assuming singleS toS scattering approximation, was used to calculate the quality factorQ from the two data set. Results show a quality factor increasing with frequency, following the empirical lawQ=Q _o f ⁿ .Q _o andn are lower for the Irno Valley than for Granada. This result is interpreted in terms of different scattering environments present in the two investigated areas.  相似文献   

Acid Neutralization by Gulf Coast Sediments     

Linn E. Fink  Winton G. Aubert  William J. Bernard 《Ground water》1991,29(4):489-494

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The Behavior of Dense, Nonaqueous Phase Liquids in Fractured Clay and Rock   总被引：2，自引：0，他引：2  

Bernard H. Kueper  David B. McWhorter 《Ground water》1991,29(5):716-728

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Carboxylic monoacids in the air of mayombe forest (Congo): Role of the forest as a source or sink     

Jean Servant  Georges Kouadio  Bernard Cros  Robert Delmas 《Journal of Atmospheric Chemistry》1991,12(4):367-380

In the tropical rain forests of the Congo during the dry season, from June to September 1987, carboxylic acid partial pressures (P _gas) in the air above the canopy, at ground level, and at the boundary layer, were estimated from water samples such as fog and rainwater. The concentrations of these acids were also measured in the sap of tree leaves. Tree leaves act as a sink or as a source if the acid P _gas is greater of lower than the acid concentrations in molecular form in sap. For each of these soluble gases, there is a value of P _gas where the exchange is nul. This is called the compensation point. Values of the compensation point for some tree leaves were evaluated according to Henry's law. Henry's law coefficients at ppm levels were redetermined for formic (HCOOH), acetic (CH₃COOH), propionic (CH₃CH₂COOH), and isobutyric (CH₃CH(CH₃)COOH) acids.By comparison of P _gas and compensation points, it is concluded that the forest was a potential source for these acids. The soil-or the litter-acts as a significant source of a carboxylic acid of C₃ or C₄ atoms in the aliphatic chain. This carboxylic acid, not yet fully characterized, could play an important role in the rain acidity in forested zones of the equatorial areas.The direct emission of these carboxylic acids by vegetation was the main source in the boundary layer above the forest. The average emissions were 3.1×10⁹, 7.8×10⁹, and 8.4×10⁹ molecules cm^-2 s^-1 for HCOOH, CH₃COOH, and CH₃CH₂COOH, respectively. The savanna is an exogenous source of HCOOH and CH₃CH₂COOH during moderately rainy days for 30% of the time. The ozonolysis of isoprene seems to be a small source of HCOOH.  相似文献