Nanoscale origin of the thermo-mechanical behavior of clays     

Laurent Brochard  Túlio Honório  Matthieu Vandamme  Michel Bornert  Michael Peigney 《Acta Geotechnica》2017,12(6):1261-1279

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Thermal radiative fluxes through inhomogeneous cloud fields: a sensitivity study using a new stochastic cloud generator     

Albert Benassi  Frdric Szczap  Anthony Davis  Matthieu Masbou  Cline Cornet  Pascal Bleuyard 《Atmospheric Research》2004,72(1-4):291

We analyze the effects of flat and bumpy top, fractional and internally inhomogeneous cloud layers on large area-averaged thermal radiative fluxes. Inhomogeneous clouds are generated by a new stochastic model: the tree-driven mass accumulation process (tdMAP). This model is able to provide stratocumulus and cumulus cloud fields with properties close to those observed in real clouds. A sensitivity study of cloud parameters is done by analyzing differences between 3D fluxes simulated by the spherical harmonic discrete ordinate method and three “standard” models likely to be used in general circulation models: plane-parallel homogeneous cloud model (PPH), PPH with fractional cloud coverage model (FCPPH) and independent pixel approximation model (IPA). We show that thermal fluxes are strong functions of fractional cloud coverage, mean optical depth, mean geometrical thickness and cloud base altitude. Fluctuations of “in-cloud” horizontal variability in optical depth and cloud-top bumps have negligible effects in the whole. We also showed that PPH, FCPPH and IPA models are not suitable to compute thermal fluxes of flat top fractional inhomogeneous cloud layer, except for completely overcast cloud. This implies that horizontal transport of photon at thermal wavelengths is important when cloudy cells are separated by optically thin regions.  相似文献   

Modelling the Mixing Function to Constrain Coseismic Hydrochemical Effects: An Example from the French Pyrénées     

Jean-Paul Toutain  Margot Munoz  Jean-Louis Pinaud  Stéphanie Levet  Matthieu Sylvander  Alexis Rigo  Jocelyne Escalier 《Pure and Applied Geophysics》2006,163(4):723-744

Groundwater coseismic transient anomalies are evidenced and characterized by modelling the mixing function F characteristic of the groundwater dynamics in the Ogeu (western French Pyrénées) seismic context. Investigations of water-rock interactions at Ogeu indicate that these mineral waters from sedimentary environments result from the mixing of deep waters with evaporitic signature with surficial karstic waters. A 3-year hydrochemical monitoring of Ogeu springwater evidences that using arbitrary thresholds constituted by the mean ± 1 or 2σ, as often performed in such studies, is not a suitable approach to characterize transient anomalies. Instead, we have used a mixing function F calculated with chemical elements, which display a conservative behavior not controlled by the precipitation of a mineral phase. F is processed with seismic energy release (E_s) and effective rainfalls (R). Linear impulse responses of F to E_s and R have been calculated. Rapid responses (10 days) to rainwater inputs are evidenced, consisting in the recharge of the shallow karstic reservoir by fresh water. Complex impulse response of F to microseismic activity is also evidenced. It consists in a 2-phase hydrologic signal, with an inflow of saline water in the shallow reservoir with a response delay of 10 days, followed by an inflow of karstic water with a response delay of 70 days, the amount being higher than the saline inflow. Such a process probably results from changes in volumetric strain with subsequent microfracturation transient episodes allowing short inflow of deep salted water in the aquifer. This study demonstrates that groundwater systems in such environments are unstable systems that are highly sensitive to both rainfall inputs and microseismic activity. Impulse responses calculation of F to E_s is shown to be a powerful tool to identify transient anomalies. Similar processing is suggested to be potentially efficient to detect precursors of earthquakes when long time-series (5 years at least) are available in areas with high seismicity.  相似文献   

Reconstruction of the history of the Palliser Rockslide based on 36Cl terrestrial cosmogenic nuclide dating and debris volume estimations     

Matthieu Sturzenegger  Doug Stead  John Gosse  Brent Ward  Corey Froese 《Landslides》2015,12(6):1097-1106

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Analysis of the seismicity in the central part of the Pyrenees (France), and tectonic implications     

Alexis?RigoEmail author  Annie?Souriau  Noalwenn?Dubos  Matthieu?Sylvander  Christian?Ponsolles 《Journal of Seismology》2005,9(2):211-222

Two temporary seismological networks have been set up in 2000 and 2002 in the central part of the Pyrenees, in a region, which appears as a transition between two domains where both the seismic activity and the tectonic regime are different. Together with the permanent networks, they allowed us to obtain precise hypocenter locations for more than 400 events with local magnitudes ranging from 1.5 to 4.6, as well as 30 new focal mechanisms. The seismicity is distributed in several clusters, which are not located along the North Pyrenean Fault, considered as the major tectonic accident resulting from the suture of the Iberian and Eurasian convergent plates when the range formed. Several small fault segments dipping to the north are identified. The maximum focal depth varies from 10 to 20 km, with variations which are roughly parallel to those of the Moho, indicating a thickening of the seismogenic layer to the east of the studied area. The obtained focal solutions reveal a predominance of normal faulting to the West and reverse faulting to the East, with strike-slip motions in between. The largest fault segment to the East, with a length of about 20 km, could possibly be related to a large historical event which occurred in 1660, with intensity IX, close to cities which have become since then important touristic centres.  相似文献   

Quantifying initial and wind forcing uncertainties in the Gulf of Mexico   总被引：1，自引：0，他引：1  

Guotu Li  Mohamed Iskandarani  Matthieu Le Hénaff  Justin Winokur  Olivier P. Le Maître  Omar M. Knio 《Computational Geosciences》2016,20(5):1133-1153

This study aims at analyzing the combined impact of uncertainties in initial conditions and wind forcing fields in ocean general circulation models (OGCM) using polynomial chaos (PC) expansions. Empirical orthogonal functions (EOF) are used to formulate both spatial perturbations to initial conditions and space-time wind forcing perturbations, namely in the form of a superposition of modal components with uniformly distributed random amplitudes. The forward deterministic HYbrid Coordinate Ocean Model (HYCOM) is used to propagate input uncertainties in the Gulf of Mexico (GoM) in spring 2010, during the Deepwater Horizon oil spill, and to generate the ensemble of model realizations based on which PC surrogate models are constructed for both localized and field quantities of interest (QoIs), focusing specifically on sea surface height (SSH) and mixed layer depth (MLD). These PC surrogate models are constructed using basis pursuit denoising methodology, and their performance is assessed through various statistical measures. A global sensitivity analysis is then performed to quantify the impact of individual modes as well as their interactions. It shows that the local SSH at the edge of the GoM main current—the Loop Current—is mostly sensitive to perturbations of the initial conditions affecting the current front, whereas the local MLD in the area of the Deepwater Horizon oil spill is more sensitive to wind forcing perturbations. At the basin scale, the SSH in the deep GoM is mostly sensitive to initial condition perturbations, while over the shelf it is sensitive to wind forcing perturbations. On the other hand, the basin MLD is almost exclusively sensitive to wind perturbations. For both quantities, the two sources of uncertainty have limited interactions. Finally, the computations indicate that whereas local quantities can exhibit complex behavior that necessitates a large number of realizations, the modal analysis of field sensitivities can be suitably achieved with a moderate size ensemble.  相似文献   

Assessment of observational networks with the Representer Matrix Spectra method—application to a 3D coastal model of the Bay of Biscay     

Matthieu Le Hénaff  Pierre De Mey  Patrick Marsaleix 《Ocean Dynamics》2009,59(1):3-20

The development of coastal ocean modeling in the recent years has allowed an improved representation of the associated complex physics. Such models have become more realistic, to the point that they can now be used to design observation networks in coastal areas, with the idea that a “good” network is a network that controls model state error. To test this ability without performing data assimilation, we set up a technique called Representer Matrix Spectra (RMS) technique that combines the model state and observation error covariance matrices into a single scaled representer matrix. Examination of the spectrum and the eigenvectors of that matrix informs us on which model state error modes a network can detect and constrain amidst the observation error background. We applied our technique to a 3D coastal model in the Bay of Biscay, with a focus on mesoscale activity, and tested the performance of various altimetry networks and an in situ array deployment strategy. It appears that a single nadir altimeter is not efficient enough at capturing coastal mesoscale physics, while a wide swath altimeter would do a much better job. Testing various local in situ array configurations confirms that adding a current meter to a vertical temperature measurement array improves the detection of secondary variability modes, while shifting the array higher on the shelf break would obviously enhance the model constraint along the coast. The RMS technique is easily set up and used as a “black box,” but the utility of its results is maximized by previous knowledge of model state error physics. The technique provides both quantitative (eigenvalues) and qualitative (eigenvectors) tools to study and compare various network options. The qualitative approach is essential to discard possibly inconsistent modes.  相似文献   

Solar EUV/FUV irradiance variations: analysis and observational strategy     

Matthieu Kretzschmar  Thierry Dudok de Wit  Jean Lilensten  Jean-Francois Hochedez  Jean Aboudarham  Pierre-Olivier Amblard  Frederic Auchère  Said Moussaoui 《Acta Geophysica》2009,57(1):42-51

The knowledge of solar extreme and far ultraviolet (EUV) irradiance variations is essential for the characterization of the Earth’s upper atmosphere. For a long time, this knowledge has been based on empirical models, which are themselves based on proxies of the solar activity. However, the accurate modeling and prediction of the Earth’s upper atmosphere necessitate to improve the precision on the irradiance and its variations below about 200 nm. Here, we present a review of recent works made by the authors that aim at quantifying the irradiance variability at these wavelengths, and that lead to new way of monitoring the solar EUV/FUV irradiance spectrum. In more details, it is shown that the quantification of the high level of redundancy in the solar spectrum variability allows to envisage measuring only a small portion of the spectrum without losing essential knowledge. Finally, we discuss what should and could be measured in order to retrieve the solar extreme and far ultraviolet spectrum.  相似文献   

Voluminous lava flows at Oldoinyo Lengai in 2006: chronology of events and insights into the shallow magmatic system     

Matthieu Kervyn  Gerald G. J. Ernst  Jurgis Klaudius  Jörg Keller  François Kervyn  Hannes B. Mattsson  Frederic Belton  Evelyne Mbede  Patric Jacobs 《Bulletin of Volcanology》2008,70(9):1069-1086

The largest natrocarbonatite lava flow eruption ever documented at Oldoinyo Lengai, NW Tanzania, occurred from March 25 to April 5, 2006, in two main phases. It was associated with hornito collapse, rapid extrusion of lava covering a third of the crater and emplacement of a 3-km long compound rubbly pahoehoe to blocky aa-like flow on the W flank. The eruption was followed by rapid enlargement of a pit crater. The erupted natrocarbonatite lava has high silica content (3% SiO₂). The eruption chronology is reconstructed from eyewitness and news media reports and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, which provide the most reliable evidence to constrain the eruption’s onset and variations in activity. The eruption products were mapped in the field and the total erupted lava volume estimated at 9.2 ± 3.0 × 10⁵ m³. The event chronology and field evidence are consistent with vent construct instability causing magma mixing and rapid extrusion from shallow reservoirs. It provides new insights into and highlights the evolution of the shallow magmatic system at this unique natrocarbonatite volcano.  相似文献   

Developing a Complex Independent Component Analysis (CICA) Technique to Extract Non-stationary Patterns from Geophysical Time Series     

Ehsan Forootan  Jürgen Kusche  Matthieu Talpe  C. K. Shum  Michael Schmidt 《Surveys in Geophysics》2018,39(3):435-465

In recent decades, decomposition techniques have enabled increasingly more applications for dimension reduction, as well as extraction of additional information from geophysical time series. Traditionally, the principal component analysis (PCA)/empirical orthogonal function (EOF) method and more recently the independent component analysis (ICA) have been applied to extract, statistical orthogonal (uncorrelated), and independent modes that represent the maximum variance of time series, respectively. PCA and ICA can be classified as stationary signal decomposition techniques since they are based on decomposing the autocovariance matrix and diagonalizing higher (than two) order statistical tensors from centered time series, respectively. However, the stationarity assumption in these techniques is not justified for many geophysical and climate variables even after removing cyclic components, e.g., the commonly removed dominant seasonal cycles. In this paper, we present a novel decomposition method, the complex independent component analysis (CICA), which can be applied to extract non-stationary (changing in space and time) patterns from geophysical time series. Here, CICA is derived as an extension of real-valued ICA, where (a) we first define a new complex dataset that contains the observed time series in its real part, and their Hilbert transformed series as its imaginary part, (b) an ICA algorithm based on diagonalization of fourth-order cumulants is then applied to decompose the new complex dataset in (a), and finally, (c) the dominant independent complex modes are extracted and used to represent the dominant space and time amplitudes and associated phase propagation patterns. The performance of CICA is examined by analyzing synthetic data constructed from multiple physically meaningful modes in a simulation framework, with known truth. Next, global terrestrial water storage (TWS) data from the Gravity Recovery And Climate Experiment (GRACE) gravimetry mission (2003–2016), and satellite radiometric sea surface temperature (SST) data (1982–2016) over the Atlantic and Pacific Oceans are used with the aim of demonstrating signal separations of the North Atlantic Oscillation (NAO) from the Atlantic Multi-decadal Oscillation (AMO), and the El Niño Southern Oscillation (ENSO) from the Pacific Decadal Oscillation (PDO). CICA results indicate that ENSO-related patterns can be extracted from the Gravity Recovery And Climate Experiment Terrestrial Water Storage (GRACE TWS) with an accuracy of 0.5–1 cm in terms of equivalent water height (EWH). The magnitude of errors in extracting NAO or AMO from SST data using the complex EOF (CEOF) approach reaches up to ~50% of the signal itself, while it is reduced to ~16% when applying CICA. Larger errors with magnitudes of ~100% and ~30% of the signal itself are found while separating ENSO from PDO using CEOF and CICA, respectively. We thus conclude that the CICA is more effective than CEOF in separating non-stationary patterns.  相似文献