On The Small-Scale Dynamics Of Flow Splitting In The Rhine Valley During A Shallow Foehn Event     

Philippe Drobinski  Alain M. Dabas  Christian Haeberli  Pierre H. Flamant 《Boundary-Layer Meteorology》2001,99(2):277-296

Flow splitting in the Rhine valley has been observed with a transportable wind lidar (TWL) during a shallow-foehn event in the framework of the Mesoscale Alpine Programme (MAP). The Doppler lidar recorded in detail flow splitting, foehn wind gusts, and flow reversal. Such structures have not previously been observed with comparable detail by conventional in-situinstruments. In addition to the TWL, boundary-layer processes have been documented by means of rawinsondes and surface stations. This paper presents an analysis of the processes giving birth to flow splitting between the Seez and Rhine valleys during Intensive Observation Period (IOP) 5 (1–3 October 1999) by combining the collected data with hydraulic theory. The study shows thatthe splitting of the channelled flow is associated with (1) the existence of a stagnation point at the intersection of the Seez and Rhine valleys, and (2) the deflection of the flow by the lateral sidewalls of the valleys.  相似文献   

The stability of sapphirine-quartz and hypersthene-sillimanite-quartz assemblages: an experimental investigation in the system FeO−MgO−Al2O3−SiO2 under H2O and CO2 conditions     

Philippe Bertrand  David J. Ellis  David H. Green 《Contributions to Mineralogy and Petrology》1991,108(1-2):55-71

Phase relations and mineral chemistry involving the phases garnet (Gt), spinel (Sp), hypersthene (Hy), sapphirine (Sa), cordierite (Cd), sillimanite (Sil) and quartz (Qz) have been experimentally determined in the system FMAS (FeO−MgO−Al₂O₂−SiO₂) under low fO₂ and for various H₂O/CO₂ conditions. Several compositions were studied with 100 (Mg/Mg+Fe) ratio ranging from 64 to 87 with excess quartz and sillimanite. Our data do not show any differences in Gt−Cd stability and composition as a function of H₂O, CO₂ and H₂O−CO₂ (±CH₄) content, in good agreement with a previous experimental study at lower temperature (Aranovich and Podlesskii 1983). At 1,000° C and 11 kbar, under CO₂-saturated conditions, cordierite grew from a crystalline mix unseeded with cordierite. Thus, under water-absent conditions, cordierite will have a high-P stability field in the presence of CO₂. If water has a pressure stabilizing effect on cordierite, then our results would indicate that the effects of H₂O and CO₂ are of the same magnitude at high temperature. Our data support the theoretical P-T grid proposed by Hensen (1986) for high-T metapelites and are largely consistent with the high-temperature experimental data of Hensen and Green (1973). The univariant boundary Gt+Cd=Hy+Sil+Qz, which marks the disappearance of Hy−Sil−Qz assemblages, has a negative dP/dT slope above 1,000° C and a positive one below this temperature. Extrapolation of our data to iron-free systems shows that the high-P breakdown limit of Mg-cordierite has a negative slope in the range 1,025–1,300° C and probably positive below 1,000° C. This indicates a maximum of stability for Mg-cordierite at around 1,000° C and 13 kbar. Because of the curvature of the univariant reactions En+Sil=Py+Qz, Mg−Cd=En+Sil+Qz and Gt+Cd=Hy+Sil+Qz, the iron-free invariant point involving the phases Py, En, Cd, Sil and Qz probably does not exist. Sapphirine—Qz-bearing assemblages are stable only at temperatures above 1,050° C. At 1,075° C, the joint Gt−Sa is stable up to 11 kbar. At higher pressure, garnet, sapphirine and quartz react according to the reaction Gt+Sa+Qz=Hy+Sil. Reequilibrated sapphirines are more aluminous than the theoretical endmember Mg₂Al₄SiO₁₀ due to AlAl=MgSi substitutions [100(Al₂O₃/Al₂O₃+FeO+MgO) in experimental sapphirines ranges from 50.5 to 52.2]. Sapphirine in the assemblage Sa−Cd−Sil−Qz shows a decrease in Al content with decreasing temperature and pressure, such that the alumina isopleths for sapphirine have a slight negative dP/dT slope. A similar decrease in Al content of sapphirine with temperature is also observed in Sa−Sil−Qz assemblages.  相似文献   

Sensitivity of evapotranspiration in a wheat field,a forest,and a grassland to changes in climate and direct effects of carbon dioxide   总被引：2，自引：1，他引：2  

Philippe Martin  Norman J. Rosenberg  Mary S. McKenney 《Climatic change》1989,14(2):117-151

Micrometeorological and physiological measurements were used to develop Penman-Monteith models of evapotranspiration for a wheat field in eastern Nebraska, a forest in Tennessee, and a grassland in east-central Kansas. The model fit the measurements well over the periods of observation. Model sensitivities to changes in climatic and physiological parameters were then analyzed. The range of changes considered was established from recent general circulation model output and from review of recent plant physiological research. Finally, climate change scenarios produced by general circulation models for the locations and seasons matching the observed data were applied to the micrometeorological models. Simulation studies show that when all climatic and plant factors are considered, evapotranspiration estimates can differ greatly from those that consider only temperature. Depending on ecosystem and on climate and plant input used, evapotranspiration can differ from the control (no climate or plant change) by about -20 to +40%.  相似文献   

Fréchet derivatives of coupled seismograms with respect to an anelastic rotating earth     

Eric Clévédé  Philippe Lognonné 《Geophysical Journal International》1996,124(2):456-482

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9 to 5: 9 approaches to tackle 5 aspects of climate change     

Philippe Martin  Myriam Lefebvre 《Climatic change》1993,25(3-4):421-438

Humans are modifying the Earth's climate by increasing the atmospheric concentrations of carbon dioxide and other radiatively active trace gases. The resulting Climate Change is global, pervasive, complex, unpredictable, and irreversible. Nine different approaches (scientific assessment, structural analysis, decision analysis, procedure analysis, game theory, cost-benefit analysis, option valuation, insurance, and deterrence) are presented to explore how the five aspects of Climate Change affect the design of appropriate responses to its impacts.  相似文献   

Effects of the inhibitor ellipticine on cytochrome P450-reductase and cytochrome P450 (1A) function in hepatic microsomes of flounder (Platichthys flesus)     

Philippe Lemaire  David R. Livingstone 《Marine environmental research》1995,39(1-4)

The effects of the mammalian inhibitor ellipticine (5,11-dimethyl-[6H]-pyrido[4,3b] carbazole) were examined in a mechanistic study of the cytochrome P450 monooxygenase system of control and β-naphthoflavone (βNF)-induced hepatic microsomes of Platichthys flesus. Ellipticine was indicated to bind to the haem moiety of cytochrome P450s (gave type II binding spectra) and to inhibit the transfer of electrons from both the hydrophobic binding site of cytochrome P450 reductase (P450R) to P450 (inhibited P450R reductase activity) and the hydrophilic binding site of P450R to soluble electron acceptors (inhibited NAD(P)H-cytochrome c reductase activity). No effect was seen on cytochrome b₅ reductase activity. Ellipticine inhibition indicated the involvement of (i) P450R (possibly also P450s) in NADPH- but not NADH- dependent hydroxyl radical production, and (ii) electron transfer and P450/P450R interaction in NADPH-dependent cytochrome P450 1A-catalysed monooxygenation (7-ethoxyresorufin O-deethylase activity and benzo(a)pyrene (BaP) metabolism). Differential effects of ellipticine on cumene hydroperoxide (CHP)-dependent BaP metabolism (P450 peroxidase activity) with CHP concentration indicated the existence of at least two forms of P450 with different substrate affinities for CHP, and different mechanisms of formation for protein adducts and free metabolites. Overall, the studies indicate the primary site of action of ellipticine in P. flesus is binding between Fe³⁺-P450 and P450R.  相似文献   

Accretion,structure and hydrology of intermediate spreading-rate oceanic crust from drillhole experiments and seafloor observations     

Philippe A. Pezard  Roger N. Anderson  William B. F. Ryan  Keir Becker  Jeffrey C. Alt  Pascal Gente 《Marine Geophysical Researches》1992,14(2):93-123

Downhole measurements recorded in the context of the Ocean Drilling Program in Hole 504B, the deepest hole drilled yet into the oceanic crust, are analyzed in terms of accretion processes of the upper oceanic crust at intermediate spreading-rate. The upper part of the crust is found to support the non steady-state models of crustal accretion developed from seafloor observations (Kappel and Ryan, 1986; Gente, 1987). The continuous and vertical nature of borehole measurements provides stratigraphic and structural data that cannot be obtained solely from seafloor studies and, in turn, these models define a framework to analyze the structural, hydrological, and mineralogical observations made in the hole over the past decade.Due to the observed zonation with depth of alteration processes, and its relation to lava morphologies, the 650-m-thick effusive section penetrated in Hole 504B is postulated to be emplaced as the result of two main volcanic sequences. Massive lava flows are interpreted as corresponding to the onset of these sequences emplaced on the floor of the axial graben. The underlying lava made of structures with large porosity values and numerous cm-scale fractures is thus necessarily accreted at the end of the previous volcanic episode. On top of such high heterogeneous and porous intervals, the thick lava flows constitute crustal permeability barriers, thereby constraining the circulation of hydrothermal fluids.Accreted in the near vicinity of the magma chamber, the lower section is that exposed to the most intense hydrothermal circulation (such as black smokers activity). Once capped by a massive flow at the onset of the second volcanic phase, the lower interval is hydrologically separated from ocean-waters. A reducing environment develops then below it resulting, for example, in the precipitation of sulfides. Today, whereas the interval corresponding to the first volcanic episode is sealed by alteration minerals, the second-one is still open to fluid circulation in its upper section. Thus, upper part of the volcanic edifice is potentially never exposed to fluids reaching deep into the crust, while the lower one is near the ridge axis.Considering that most of the extrusives are emplaced within a narrow volcanic zone, the first unit extruded for a given vertical cross-section is necessarily emplaced at the ridge-axis. In Hole 504B, the 250-m-thickTransition Zone from dikes to extrusives is interpreted as the relict massive unit flooding the axial graben at the onset of the first volcanic sequence, and later ruptured by numerous dikes. Further from the axis, the same massive unit constitutes a potential permeability cap for vertical crustal sections accreted earlier. Also, the upper 50 meters of the basement might be considered as the far-end expression of massive outpours extruded near the ridge-axis.  相似文献   

Structure of the Malpelo Ridge (Colombia) from seismic and gravity modelling     

Boris Marcaillou  Philippe Charvis  Jean-Yves Collot 《Marine Geophysical Researches》2006,27(4):289-300

Wide-angle and multichannel seismic data collected on the Malpelo Ridge provide an image of the deep structure of the ridge and new insights on its emplacement and tectonic history. The crustal structure of the Malpelo Ridge shows a 14 km thick asymmetric crustal root with a smooth transition to the oceanic basin southeastward, whereas the transition is abrupt beneath its northwestern flank. Crustal thickening is mainly related to the thickening of the lower crust, which exhibits velocities from 6.5 to 7.4 km/s. The deep structure is consistent with emplacement at an active spreading axis under a hotspot like the present-day Galapagos Hotspot on the Cocos-Nazca Spreading Centre. Our results favour the hypothesis that the Malpelo Ridge was formerly a continuation of the Cocos Ridge, emplaced simultaneously with the Carnegie Ridge at the Cocos-Nazca Spreading Centre, from which it was separated and subsequently drifted southward relative to the Cocos Ridge due to differential motion along the dextral strike-slip Panama Fracture Zone. The steep faulted northern flank of the Malpelo Ridge and the counterpart steep and faulted southern flank of Regina Ridge are possibly related to a rifting phase that resulted in the Coiba Microplate’s separation from the Nazca Plate along the Sandra Rift.  相似文献   

The Role of Laser Ranging for Calibrating Jason-1: The Corsica Tracking Campaign     

Pierre Exertier  Joë  lle Nicolas  Philippe Berio  David Coulot  Pascal Bonnefond  Olivier Laurain 《Marine Geodesy》2004,27(1):333-340

The French Transportable Laser Ranging System (FTLRS), a highly transportable Satellite Laser Ranging (SLR) instrument, was set up in Corsica (from January to September 2002) for participating to the JASON-1 altimeter verification phase. In addition to the tracking of oceanographic satellite missions and in order to perform an accurate positioning, the FTLRS also acquired laser ranging data on geodetic satellites, STARLETTE and STELLA essentially.

The paper describes the analysis strategy mainly based on the use of a short-arc orbit technique to compute accurate 1 cm local orbits, and then the geocentric positioning (2-3 mm relative to GPS). Finally, we established the JASON-1 absolute calibration value, based on 9 SLR short-arcs (between cycles 1 and 26), at 108.2 ± 8.7 mm; the 10-day repeatability is of 26.1 mm showing that a great accuracy has been reached.  相似文献   

Seismological study of the central Ecuadorian margin: Evidence of upper plate deformation     

Nicole Bethoux  Monica Segovia  Viviana Alvarez  Jean-Yves Collot  Philippe Charvis  Audrey Gailler  Tony Monfret 《Journal of South American Earth Sciences》2011,31(1):139-152

A seismic study of a segment of the convergent margin of Ecuador is presented. During the SISTEUR campaign a network of 24 Ocean Bottom Seismometers (OBS) was deployed on the Carnegie Ridge, one line along the main axes of the ridge and two lines across the strike of the edge of the ridge, during one month. This marine network was complemented with a land network of 20 stations distributed in two lines: one parallel to the margin and the other perpendicular to it.The seismic event recorded by these networks, were located using different crustal models defined from the wide-angle seismic data modeling. Relative location techniques were used to improve earthquake locations. Seismogram waveform modeling allowed us to constrain hypocentral location for events farther than ～50 km from the network. This modeling also provided additional information to constrain the focal mechanisms of these events. The upper limit of the Interplate Seismogenic Zone (ISZ) is estimated to be at a 10 km depth in the region. The background seismic activity of the upper plate provided new insights:1) A seismic cluster that reaches the base of the overriding plate is linked to the Jipijapa-Portoviejo fault. The reactivation of this Quaternary fault is confirmed by focal mechanisms that provide rupture planes parallel to its superficial projection (N10°–N25°).2) The focal mechanisms presented in this study are compatible with a homogeneous regional stress field corresponding to an E–W to ESE–WNW compression and an NNE–SSW extension. The presence of strike-slip deformation, with a reverse component, corresponds to the NNE escape of the North Andean Block. Normal faulting accommodating this movement suggests that this part of the North Andean Block cannot be considered as a rigid block.  相似文献