Application of periodic autoregressive process to the modeling of the Garonne river flows   总被引：1，自引：1，他引：0  

Eugen Ursu  Jean-Christophe Pereau 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(7):1785-1795

Accurate forecasting of river flows is one of the most important applications in hydrology, especially for the management of reservoir systems. To capture the seasonal variations in river flow statistics, this paper develops a robust modeling approach to identify and to estimate periodic autoregressive (PAR) model in the presence of additive outliers. Since the least squares estimators are not robust in the presence of outliers, we suggest a robust estimation based on residual autocovariances. A genetic algorithm with Bayes information criterion is used to identify the optimal PAR model. The method is applied to average monthly and quarter-monthly flow data (1959–2010) for the Garonne river in the southwest of France. Results show that the accuracy of forecasts is improved in the robust model with respect to the unrobust model for the quarter-monthly flows. By reducing the number of parameters to be estimated, the principle of parsimony favors the choice of the robust approach.  相似文献   

An Approximation of Inner Boundary Conditions for Wells Intersecting Highly Conductive Structures     

Markus Giese  Thomas Reimann  Rudolf Liedl  Benoit Dewandel  Jean-Christophe Maréchal  Martin Sauter 《Ground water》2020,58(4):611-621

Inner boundary conditions describe the interaction of groundwater wells with the surrounding aquifer during pumping and are associated with well-skin damage that limits water production and water derived from wellbore storage. Pumping test evaluations of wells during immediate and early time flow require assignment of inner boundary conditions. Originally, these concepts were developed for vertical well screens, and later transferred to wellbores intersecting highly conductive structures, such as preferential flow zones in fractured and karstic systems. Conceptual models for pumping test analysis in complex bedrock geology are often simplified. Classic analytical solutions generally lump or ignore conditions that limit or enhance well productivity along the well screen at the onset of pumping. Numerical solutions can represent well drawdowns in complex geological settings, such as karst systems, more precisely than many analytical solutions by accounting for additional physical processes and avoiding assumptions and simplifications. Suitable numerical tools for flow simulations in karst are discrete pipe-continuum models that account for various physical processes such as the transient hydraulics of wellbores intersecting highly conductive structures during pumping.  相似文献   

Dynamics of the major plinian eruption of Samalas in 1257 A.D. (Lombok,Indonesia)     

Céline M. Vidal  Jean-Christophe Komorowski  Nicole Métrich  Indyo Pratomo  Nugraha Kartadinata  Oktory Prambada  Agnès Michel  Guillaume Carazzo  Franck Lavigne  Jessica Rodysill  Karen Fontijn  Surono 《Bulletin of Volcanology》2015,77(9):1-24

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Impact of vertical structure on water mass circulation in a tropical lagoon (Ebrié, Ivory Coast)     

Isabelle Brenon  Olivier Audouin  Nicolas Pouvreau  Jean-Christophe Maurin 《Journal of African Earth Sciences》2009,55(1-2):47

A one-dimensional vertical model has been developed to simulate the water mass circulation along the vertical structure in all deep coastal areas. The model has hydrodynamic and transport components solved using finite difference scheme. The one-dimensional vertical model results are coupled to the vertically averaged two-dimensional model results at each point of a horizontal grid. A theoretical salinity profile is introduced for each vertically integrated value obtained from the 2DH model results. A viscosity profile, simulating a viscosity value close to zero at the surface and with large viscosity gradients, is applied along the water column. The model is applied to the Vridi channel, connecting the Ebrié lagoon to the sea (Ivory Coast).The response of the Ebrié lagoon is studied in terms of inflow and outflow of water in the system through the Vridi channel. Due to the abrupt variation of the surface slope, vertical velocities along the water column show an anticlockwise spiral from bottom to surface during a tidal cycle. Due to the bottom friction and to the vertical viscosity profile, velocities decrease from surface to bottom. However, the freshwater inflow slows down the tidal propagation during the flood and causes the surface velocity to be smaller than the bottom velocity at mid-tide. Close to the bottom, velocities follow an anticlockwise movement due to the tidal propagation. At the water surface, velocities follow only an alternative movement of either ebb or flood, along the channel direction. No cross shore velocities can develop at the surface in the channel.  相似文献   

Using the DPFT approach to improve flash flood forecasting models     

D. Sempere Torres  J. Y. Rodriguez  Ch. Obled 《Natural Hazards》1992,5(1):17-41

DPFT is a lumped approach for operational flash flood forecasting, based on the unit hydrograph. Using a multi-event alternating iterative algorithm, it identifies a robust and stable average transfer function and a consistent set of effective rainfall series associated with each event at the same time. This key ingredient allows an objective calibration of different loss functions, relating gauged precipitation and effective rainfall. A case study based on an operational French basin (545 km²) is presented. Three lumped production functions have been calibrated and compared. The results show that more elaborate models of loss functions must be proposed, and some possible directions for this are pointed out.  相似文献   

From oblique subduction to intra-continental transpression: Structures of the southern Kermadec-Hikurangi margin from multibeam bathymetry,side-scan sonar and seismic reflection     

Jean-Yves Collot  Jean Delteil  Keith B. Lewis  Bryan Davy  Geoffroy Lamarche  Jean-Christophe Audru  Phil Barnes  Franck Chanier  Eric Chaumillon  Serge Lallemand  Bernard Mercier de Lepinay  Alan Orpin  Bernard Pelletier  Marc Sosson  Bertrand Toussaint  Chris Uruski 《Marine Geophysical Researches》1996,18(2-4):357-381

The southern Kermadec-Hikurangi convergent margin, east of New Zealand, accommodates the oblique subduction of the oceanic Hikurangi Plateau at rates of 4–5 cm/yr. Swath bathymetry and sidescan data, together with seismic reflection and geopotential data obtained during the GEODYNZ-SUD cruise, showed major changes in tectonic style along the margin. The changes reflect the size and abundance of seamounts on the subducting plateau, the presence and thickness of trench-fill turbidites, and the change to increasing obliquity and intracontinental transpression towards the south. In this paper, we provide evidence that faulting with a significant strike-slip component is widespread along the entire 1000 km margin. Subduction of the northeastern scrap of the Hikurangi Plateau is marked by an offset in the Kermadec Trench and adjacent margin, and by a major NW-trending tear fault in the scarp. To the south, the southern Kermadec Trench is devoid of turbidite fill and the adjacent margin is characterized by an up to 1200 m high scarp that locally separates apparent clockwise rotated blocks on the upper slope from strike-slip faults and mass wasting on the lower slope. The northern Hikurangi Trough has at least 1 km of trench-fill but its adjacent margin is characterized by tectonic erosion. The toe of the margin is indented by 10–25 km for more than 200 km, and this is inferred to be the result of repeated impacts of the large seamounts that are abundant on the northern Hikurangi Plateau. The two most recent impacts have left major indentations in the margin. The central Hikurangi margin is characterized by development of a wide accretionary wedge on the lower slope, and by transpression of presubduction passive margin sediments on the upper slope. Shortening across the wedge together with a component of strike-slip motion on the upper slope supports an interpretation of some strain partitioning. The southern Hikurangi margin is a narrow, mainly compressive belt along a very oblique, apparently locked subduction zone.  相似文献   

Far-Infrared CO Rotational Lines in the Orion Molecular Cloud     

M.J. Sempere  J. Cernicharo  E. González-Alfonso  B. Lefloch  S. Pérez-Martínez  S.J. Leeks 《Astrophysics and Space Science》1998,263(1-4):205-208

We present a high signal-to-noise grating spectrum between 43-196.9 μm of the Orion molecular cloud towards the massive star-forming region IRc2, obtained with the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO). CO lines up to J=20-19 have been detected around Orion-IRc2, while in the central position higher quantum numbers have been found. Lines of the ¹³CO isotopic species have also been observed in several directions. In addition, high quality LWS-FP observations of some CO lines have been performed towards IRc2. The data analysis suggest that at least two regions of Orion-IRc2 contribute to the observed CO emission: the ridge, responsible of the spatial extension, and the plateau, dominating the line flux observed towards the center of the map. CO emission through the Orion molecular cloud has been studied in terms of temperature, column density and H₂ volume density, using and Large Velocity Gradient (LVG) model. We find that the flux ratio of the several CO lines can not be explained in terms of an homogeneous source, but a gradient in temperature and density must be involved. Besides the CO lines, several molecular and fine-structure atomic lines have been detected in all observed positions. A detailed discussion of other molecular species rather than CO (H2O, OH...) can be found in the contribution by Cernicharo et al (1998). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Ethnic groups’ response to the 26 December 2004 earthquake and tsunami in Aceh, Indonesia   总被引：4，自引：4，他引：0  

Jean-Christophe Gaillard  Elsa Clavé  Océane Vibert  Azhari  Dedi  Jean-Charles Denain  Yusuf Efendi  Delphine Grancher  Catherine C. Liamzon  Desy Rosnita Sari  Ryo Setiawan 《Natural Hazards》2008,47(1):17-38

The 26 December 2004 earthquake and tsunami unfairly hit the different ethnic groups of Aceh, Indonesia. About 170,000 Acehnese and Minangkabau people died in the Northern tip of Sumatra while only 44 Simeulue people passed away in the neighbouring Simeulue island located near the earthquake epicentre. Such a difference in the death toll does not lie in the nature of the hazard but in different human behaviours and ethnic contexts. The present study draws on a contextual framework of analysis where people’s behaviour in the face of natural hazards is deeply influenced by the cultural, social, economic and political context. Questionnaire-based surveys among affected communities, key informant interviews and literature reviews show that the people of Simeulue detected the tsunami very early and then escaped to the mountains. On the other hand, Acehnese and Minangkabau people, respectively in the cities of Banda Aceh and Meulaboh, did not anticipate the phenomenon and were thus caught by the waves. The different behaviours of the victims have been commanded by the existence or the absence of a disaster subculture among affected communities as well as by their capacity to protect themselves in facing the tsunami. People’s behaviours and the capacity to protect oneself can be further tracked down to a deep tangle of intricate factors which include the armed conflict that has been affecting the province since the 1970s, the historical and cultural heritage and the national political economy system. This paper finally argues that the uneven impact of the 26 December 2004 earthquake and tsunami in Aceh lies in the different daily life conditions of the ethnic groups struck by the disaster.  相似文献   

Transitions between explosive and effusive phases during the cataclysmic 2010 eruption of Merapi volcano,Java, Indonesia     

Katie Preece  Ralf Gertisser  Jenni Barclay  Sylvain J. Charbonnier  Jean-Christophe Komorowski  Richard A. Herd 《Bulletin of Volcanology》2016,78(8):54

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The typology of Irish hard-rock aquifers based on an integrated hydrogeological and geophysical approach     

Jean-Christophe Comte  Rachel Cassidy  Janka Nitsche  Ulrich Ofterdinger  Katarina Pilatova  Raymond Flynn 《Hydrogeology Journal》2012,20(8):1569-1588

Groundwater flow in hard-rock aquifers is strongly controlled by the characteristics and distribution of structural heterogeneity. A methodology for catchment-scale characterisation is presented, based on the integration of complementary, multi-scale hydrogeological, geophysical and geological approaches. This was applied to three contrasting catchments underlain by metamorphic rocks in the northern parts of Ireland (Republic of Ireland and Northern Ireland, UK). Cross-validated surface and borehole geophysical investigations confirm the discontinuous overburden, lithological compartmentalisation of the bedrock and important spatial variations of the weathered bedrock profiles at macro-scale. Fracture analysis suggests that the recent (Alpine) tectonic fabric exerts strong control on the internal aquifer structure at meso-scale, which is likely to impact on the anisotropy of aquifer properties. The combination of the interpretation of depth-specific hydraulic-test data with the structural information provided by geophysical tests allows characterisation of the hydrodynamic properties of the identified aquifer units. Regionally, the distribution of hydraulic conductivities can be described by inverse power laws specific to the aquifer litho-type. Observed groundwater flow directions reflect this multi-scale structure. The proposed integrated approach applies widely available investigative tools to identify key dominant structures controlling groundwater flow, characterising the aquifer type for each catchment and resolving the spatial distribution of relevant aquifer units and associated hydrodynamic parameters.  相似文献