A comparison of downscaling techniques in the projection of local climate change and wheat yields     

Qunying Luo  Li Wen  John L. McGregor  Bertrand Timbal 《Climatic change》2013,120(1-2):249-261

This study aims to evaluate the performance of two mainstream downscaling techniques: statistical and dynamical downscaling and to compare the differences in their projection of future climate change and the resultant impact on wheat crop yields for three locations across New South Wales, Australia. Bureau of Meteorology statistically- and CSIRO dynamically-downscaled climate, derived or driven by the CSIRO Mk 3.5 coupled general circulation model, were firstly evaluated against observed climate data for the period 1980–1999. Future climate projections derived from the two downscaling approaches for the period centred on 2055 were then compared. A stochastic weather generator, LARS-WG, was used in this study to derive monthly climate changes and to construct climate change scenarios. The Agricultural Production System sIMulator-Wheat model was then combined with the constructed climate change scenarios to quantify the impact of climate change on wheat grain yield. Statistical results show that (1) in terms of reproducing the past climate, statistical downscaling performed better over dynamical downscaling in most of the cases including climate variables, their mean, variance and distribution, and study locations, (2) there is significant difference between the two downscaling techniques in projected future climate change except the mean value of rainfall across the three locations for most of the months; and (3) there is significant difference in projected wheat grain yields between the two downscaling techniques at two of the three locations.  相似文献   

On the Influence of a Simple Microphysics Parametrization on Radiation Fog Modelling: A Case Study During ParisFog     

Xiaojing Zhang  Luc Musson-Genon  Eric Dupont  Maya Milliez  Bertrand Carissimo 《Boundary-Layer Meteorology》2014,151(2):293-315

A detailed numerical simulation of a radiation fog event with a single column model is presented, which takes into account recent developments in microphysical parametrizations. One-dimensional simulations are performed using the computational fluid dynamics model Code_Saturne and the results are compared to a very detailed in situ dataset collected during the ParisFog campaign, which took place near Paris, France, during the winter 2006–2007. Special attention is given to the detailed and complete diurnal simulations and to the role of microphysics in the fog life cycle. The comparison between the simulated and the observed visibility, in the single-column model case study, shows that the evolution of radiation fog is correctly simulated. Sensitivity simulations show that fog development and dissipation are sensitive to the droplet-size distribution through sedimentation/deposition processes but the aerosol number concentration in the coarse mode has a low impact on the time of fog formation.  相似文献   

Hollow Cylinder Tests on Boom Clay: Modelling of Strain Localization in the Anisotropic Excavation Damaged Zone     

Bertrand François  Vincent Labiouse  Arnaud Dizier  Ferdinando Marinelli  Robert Charlier  Frédéric Collin 《Rock Mechanics and Rock Engineering》2014,47(1):71-86

Boom Clay is extensively studied as a potential candidate to host underground nuclear waste disposal in Belgium. To guarantee the safety of such a disposal, the mechanical behaviour of the clay during gallery excavation must be properly predicted. In that purpose, a hollow cylinder experiment on Boom Clay has been designed to reproduce, in a small-scale test, the Excavation Damaged Zone (EDZ) as experienced during the excavation of a disposal gallery in the underground. In this article, the focus is made on the hydro-mechanical constitutive interpretation of the displacement (experimentally obtained by medium resolution X-ray tomography scanning). The coupled hydro-mechanical response of Boom Clay in this experiment is addressed through finite element computations with a constitutive model including strain hardening/softening, elastic and plastic cross-anisotropy and a regularization method for the modelling of strain localization processes. The obtained results evidence the directional dependency of the mechanical response of the clay. The softening behaviour induces transient strain localization processes, addressed through a hydro-mechanical second grade model. The shape of the obtained damaged zone is clearly affected by the anisotropy of the materials, evidencing an eye-shaped EDZ. The modelling results agree with experiments not only qualitatively (in terms of the shape of the induced damaged zone), but also quantitatively (for the obtained displacement in three particular radial directions).  相似文献   

The application of an innovative inverse model for understanding and predicting landslide movements (Salazie cirque landslides,Reunion Island)     

Pierre Belle  Bertrand Aunay  Séverine Bernardie  Gilles Grandjean  Bernard Ladouche  Romain Mazué  Jean-Lambert Join 《Landslides》2014,11(3):343-355

The prediction of landslide movement acceleration is a complex problem, among others identified for deep-seated landslides, and represents a crucial step for risk assessment. Within the scope of this problem, the objective of this paper is to explore a modelling method that enables the study of landslide function and facilitates displacement predictions based on a limited data set. An inverse modelling approach is proposed for predicting the temporal evolution of landslide movement based on rainfall and displacement velocities. Initially, the hydrogeology of the studied landslides was conceptualised based on correlative analyses. Subsequently, we applied an inverse model with a Gaussian-exponential transfer function to reproduce the displacements. This method was tested on the Grand Ilet (GI) and Mare-à-Poule-d’Eau (HB) landslides on Reunion Island in the Indian Ocean. We show that the behaviour of landslides can be modelled by inverse models with a bimodal transfer function using a Gaussian-exponential impulse response. The cumulative displacements over 7 years of modelling (2 years of calibration period for GI, and 4 years for HB) were reproduced with an RMSE above 0.9. The characteristics of the bimodal transfer function are directly related to the hydrogeological functioning demonstrated by the correlative analyses: the rapid reaction of a landslide can be associated with the effect of a preferential flow path on groundwater level variations. Thus, this study shows that the inverse model using a Gaussian-exponential transfer function is a powerful tool for predicting deep-seated landslide movements and for studying how they function. Beyond modelling displacements, our approach effectively demonstrates its ability to contribute relevant data for conceptualising the sliding mechanisms and hydrogeology of landslides.  相似文献   

Introductory Editorial     

Jacques Mudry  Catherine Bertrand  François Zwahlen 《Environmental Earth Sciences》2014,71(2):505-506

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Constitutive analysis of the mechanical anisotropy of Opalinus Clay   总被引：1，自引：0，他引：1  

Simon Salager  Bertrand François  Mathieu Nuth  Lyesse Laloui 《Acta Geotechnica》2013,8(2):137-154

This paper aims to analyse the anisotropic features of behaviour of Opalinus Clay using the theory of plastic multi-mechanisms. The results of triaxial tests conducted with different load levels and directions showed that the mechanical behaviour of this shale is cross-anisotropic. The stiffer samples are those in which the loading direction is parallel to the bedding plane. This indicates that the preconsolidation stress depends on the orientation of the load with respect to the fabric of Opalinus Clay. It is proposed to interpret the observed cross-anisotropy with an elastoplastic model based on four plastic strain mechanisms that may be successively mobilised depending on the loading direction. The predicted stress–strain responses vary according to the directions of the space as a result of the hardening process, depending on the number of plastic strain mechanisms that have been mobilised. The numerical predictions show overall good agreement with the experimental data in terms of deviatoric stress versus axial strain, demonstrating that multi-mechanism plasticity is a suitable constitutive tool for the interpretation of the mechanical anisotropy of this shale.  相似文献   

Direct detection and characterization of extrasolar planets: The Mariotti space interferometer     

Bertrand Mennesson  Alain Léger 《Icarus》2005,178(2):570-588

Space infrared nulling interferometry has been identified as one of the most promising techniques for direct detection of Earthlike extrasolar planets and spectroscopic analysis of their atmospheres in the near future. After a review of various nulling interferometer schemes, we introduce the concept of internal modulation. As an illustration, we describe a two-dimensional array of telescopes that provides full internal modulation capabilities: the Mariotti space interferometer. It consists of six free-flying telescopes positioned on the sides of an equilateral triangle and grouped into three nulling interferometers. Their nulled outputs are suitably phase-shifted with respect to each other, coherently recombined, and detected. The phase shifts applied between the nullers are periodically changed, providing signal modulation at a frequency that can be selected to minimize instrumental and background noise. The frequency upper limit is set by the read-out noise of the detectors, and turns out to be ¹⁰⁻¹-¹⁰⁻² Hz for currently available Si:As BIB devices. This “fast” signal modulation allows much better monitoring of the background and detector drifts than when one relies solely on the external modulation provided by the slow rotation of the whole interferometer (at typical frequencies of 3×¹⁰⁻⁴-3×¹⁰⁻⁵ Hz). Mariotti internal modulation, also known as “phase chopping,” thus appears as a major step toward the feasibility of the Darwin and TPF space missions.  相似文献   

Crustal structure deduced from receiver functions via single-scattering migration     

E. Bertrand  A. Deschamps  J. Virieux 《Geophysical Journal International》2002,150(2):524-541

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Pyroxene microstructure in the Northwest Africa 856 martian meteorite     

Hugues Leroux  Bertrand Devouard  Patrick Cordier  Franois Guyot 《Meteoritics & planetary science》2004,39(5):711-722

Abstract— Transmission electron microscopy was used to examine pyroxene microstructure in the Northwest Africa (NWA) 856 martian meteorite to construct its cooling and shock histories. All pyroxenes contain strained coherent pigeonite/augite exsolution lamellae on (001). The average width and periodicity of lamellae are 80 and 400 nm, respectively, indicating a cooling rate below 0.1 °C/hr for the parent rock. Pigeonite and augite are topotactic, with strained coherent interfaces parallel to (001). The closure temperature for Ca‐Fe, Mg interdiffusion, estimated from the composition at the augite pigeonite interface, is about 700 °C. Tweed texture in augite reveals that a spinodal decomposition occurred. Locally, tweed evolved toward secondary pigeonite exsolutions on (001). Due to the decreasing diffusion rate with decreasing temperature, “M‐shaped” concentration profiles developed in augite lamellae. Pigeonite contains antiphase boundaries resulting from the C2/c to P2₁/c space group transition that occurred during cooling. The reconstructive phase transition from P2₁/c clinopyroxene to orthopyroxene did not occur. The deformation (shock) history of the meteorites is revealed by the presence of dislocations and mechanical twins. Dislocations are found in glide configuration, with the [001](100) glide system preferentially activated. They exhibit strong interaction with the strained augite/pigeonite interfaces and did not propagate over large distances. Twins are found to be almost all parallel to (100) and show moderate interaction with the augite/pigeonite interfaces. These twins are responsible for the plastic deformation of the pyroxene grains. Comparison with microstructure of shocked clinopyroxene (experimentally or naturally shocked) suggests that NWA 856 pyroxenes are not strongly shocked.  相似文献   

Stages of evolution of a Toarcian compacted claystone around galleries excavated between 1 and 124 years ago by the study of noble gases dissolved in pore water at the Tournemire Underground Research Laboratory (France)     

Bernard Lavielle  Jean-Michel Matray  Bertrand Thomas  Alexandre Dauzères  Fethi Bensenouci  Eric Gilabert 《Applied Geochemistry》2012

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