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   

Towards coastal risk management in France     

Philippe Deboudt 《Ocean & Coastal Management》2010,53(7):366-378

The coastal territories of mainland France constitute a prime example of an at-risk territory, with their growing concentrations of people and economic activities located mostly on a coastal fringe that is subject to shoreline retreat and coastal flooding. The perspective of higher sea levels due to climate changes exacerbates the risk that these territories will be exposed to natural coastal hazards. Since the “invention” of the littoral zone in the mid 19th-century, the vulnerability of the economic stakes on this coastal fringe has been managed mainly by controlling the hazards; this control is coordinated by the national government, which initiated coastal defense practices. At the beginning of the 1980s, natural risk prevention policies favored managing the consequences of natural disasters, with the creation of the CatNat insurance regime to indemnify natural disaster victims. By the middle of the 1990s, new natural risk management strategies had been invented to complete the control of natural hazards. As part of the emerging philosophy of Integrated Coastal Zone Management (ICZM), the French government encouraged the development of natural risk prevention policies by establishing Natural Risk Prevention Plans (PPRn) in 1995. These PPRn were a new approach to shoreline management that favored controlling development in coastal communities. As of 2008, PPRn had been approved in 270 coastal communities and required in 149.At the beginning of the 21st century, the French government set down the general orientations for managing natural coastal risks, but it was not the only stakeholder involved. Collective action emerged, bringing the national government, public institutions and the territorial and local authorities together to develop risk management policies. This collective action was facilitated by a form of decentralization of natural coastal risk management, involving regional or local implementation of the strategic orientations of shoreline management, respecting the general principles defined by the national government. These changes are part of the ICZM implementation process, which has been under way since 2005. The development of natural coastal risk prevention policies is reinforced by the soon-to-be-adopted bill concerning the Grenelle of the Environment. These policies are mainly financed by the Barnier Fund for major natural risk prevention, which is in turn funded by an obligatory contribution based on the CatNat insurance premiums. This type of financing raises the question of the relationship between risk prevention strategies and natural disaster management.  相似文献   

How to model shallow water‐table depth variations: the case of the Kervidy‐Naizin catchment,France     

Jrme Molnat  Chantal Gascuel‐Odoux  Philippe Davy  Patrick Durand 《水文研究》2005,19(4):901-920

The aim of this work is threefold: (1) to identify the main characteristics of water‐table variations from observations in the Kervidy‐Naizin catchment, a small catchment located in western France; (2) to confront these characteristics with the assumptions of the Topmodel concepts; and (3) to analyse how relaxation of the assumptions could improve the simulation of distributed water‐table depth. A network of piezometers was installed in the Kervidy‐Naizin catchment and the water‐table depth was recorded every 15 min in each piezometer from 1997 to 2000. From these observations, the Kervidy‐Naizin groundwater appears to be characteristic of shallow groundwaters of catchments underlain by crystalline bedrock, in view of the strong relation between water distribution and topography in the bottom land of the hillslopes. However, from midslope to summit, the water table can attain a depth of many metres, it does not parallel the topographic surface and it remains very responsive to rainfall. In particular, hydraulic gradients vary with time and are not equivalent to the soil surface slope. These characteristics call into question some assumptions that are used to model shallow lateral subsurface flow in saturated conditions. We investigate the performance of three models (Topmodel, a kinematic model and a diffusive model) in simulating the hourly distributed water‐table depths along one of the hillslope transects, as well as the hourly stream discharge. For each model, two sets of parameters are identified following a Monte Carlo procedure applied to a simulation period of 2649 h. The performance of each model with each of the two parameter sets is evaluated over a test period of 2158 h. All three models, and hence their underlying assumptions, appear to reproduce adequately the stream discharge variations and water‐table depths in bottom lands at the foot of the hillslope. To simulate the groundwater depth distribution over the whole hillslope, the steady‐state assumption (Topmodel) is quite constraining and leads to unacceptable water‐table depths in midslope and summit areas. Once this assumption is relaxed (kinematic model), the water‐table simulation is improved. A subsequent relaxation of the hydraulic gradient (diffusive model) further improves water‐table simulations in the summit area, while still yielding realistic water‐table depths in the bottom land. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献