Mixed estimation methods for Halphen distributions with applications in extreme hydrologic events   总被引：3，自引：1，他引：2  

Fateh Chebana  Salaheddine El Adlouni  Bernard Bobée 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(3):359-376

The Halphen family of distributions is a flexible and complete system to fit sets of observations independent and identically distributed. Recently, it is shown that this family of distributions represents a potential alternative to the generalized extreme value distributions to model extreme hydrological events. The existence of jointly sufficient statistics for parameter estimation leads to optimality of the method of maximum likelihood (ML). Nevertheless, the ML method requires numerical approximations leading to less accurate values. However, estimators by the method of moments (MM) are explicit and their computation is fast. Even though MM method leads to good results, it is not optimal. In order to combine the advantages of the ML (optimality) and MM (efficiency and fast computations), two new mixed methods were proposed in this paper. One of the two methods is direct and the other is iterative, denoted respectively direct mixed method (MMD) and iterative mixed method (MMI). An overall comparison of the four estimation methods (MM, ML, MMD and MMI) was performed using Monte Carlo simulations regarding the three Halphen distributions. Generally, the MMI method can be considered for the three Halphen distributions since it is recommended for a majority of cases encountered in hydrology. The principal idea of the mixed methods MMD and MMI could be generalized for other distributions with complicated density functions.  相似文献   

Invertebrate assemblage responses and the dual roles of resistance and resilience to drying in intermittent rivers     

Catherine Leigh  Núria Bonada  Andrew J. Boulton  Bernard Hugueny  Scott T. Larned  Ross Vander Vorste  Thibault Datry 《Aquatic Sciences - Research Across Boundaries》2016,78(2):291-301

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Relationship between volcanic ash fallouts and seismic tremor: quantitative assessment of the 2015 eruptive period at Cotopaxi volcano,Ecuador     

Benjamin Bernard  Jean Battaglia  Antonio Proaño  Silvana Hidalgo  Francisco Vásconez  Stephen Hernandez  Mario Ruiz 《Bulletin of Volcanology》2016,78(11):80

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Contribution of geophysical surveys to groundwater modelling of a porous aquifer in semiarid Niger: An overview     

Marie Boucher  Guillaume Favreau  Marc Descloitres  Jean-Michel Vouillamoz  Sylvain Massuel  Yahaya Nazoumou  Bernard Cappelaere  Anatoli Legchenko 《Comptes Rendus Geoscience》2009,341(10-11):800-809

Subsurface geophysical surveys were carried out using a large range of methods in an unconfined sandstone aquifer in semiarid south-western Niger for improving both the conceptual model of water flow through the unsaturated zone and the parameterization of numerical a groundwater model of the aquifer. Methods included: electromagnetic mapping, electrical resistivity tomography (ERT), resistivity logging, time domain electromagnetic sounding (TDEM), and magnetic resonance sounding (MRS). Analyses of electrical conductivities, complemented by geochemical measurements, allowed us to identify preferential pathways for infiltration and drainage beneath gullies and alluvial fans. The mean water content estimated by MRS (13%) was used for computing the regional groundwater recharge from long-term change in the water table. The ranges in permeability and water content obtained with MRS allowed a reduction of the degree of freedom of aquifer parameters used in groundwater modelling.  相似文献   

A high-resolution modeling study of the Western Iberian Margin mean and seasonal upper ocean circulation   总被引：1，自引：0，他引：1  

Rita Nolasco  Ana Cordeiro Pires  Nuno Cordeiro  Bernard Le Cann  Jesus Dubert 《Ocean Dynamics》2013,63(9-10):1041-1062

The mean seasonal hydrography and circulation of the Western Iberian Margin (WIM) are studied by means of a high-resolution configuration of the Regional Oceanic Modeling System. A comparison of 5-year model averages for January and July with climatological datasets shows a general good agreement in the reproduction of the mean water mass properties and hydrographic distribution. We find that there is a prevailing tendency for slope poleward flow at about 80–100 km offshore at all latitudes from the surface to 1,500 m with strong vertical coupling. This northward flow, which is mainly along slope and amounts up to 8–10 cm s^?1, exhibits several mean flow recirculation regions on its way and evidences of an offshore pathway of poleward flow. Transports at different zonal sections further confirm the poleward flow tendency with two peaks of poleward transport in summer (3–10 Sv) and winter (2–7 Sv). The transport time series emphasize the seasonal character of the alongshore circulation and the interannual intrinsic variability of the circulation, since the forcing fields are climatological. As a conceptual essay with the purpose of assessing the Mediterranean Water flow influence on the WIM mean circulation, a second model configuration is setup, where the Mediterranean outflow into the study domain is removed. We find that there is an attenuation of the mesoscale field, but the slope poleward flow intensifies and remains as a mean dynamical feature closer to the upper slope.  相似文献   

Tendances et ruptures au niveau des pluies journalières extrêmes en Côte d'Ivoire (Afrique de l'Ouest)     

Bi Tié Albert Goula  Emile Gneneyougo Soro  Williams Kouassi  Bernard Srohourou 《水文科学杂志》2013,58(6):1067-1080

Résumé

Le changement climatique est une réalité qui affecte plusieurs variables climatiques dont les précipitations. Néanmoins, son impact sur les évènements extrêmes et en particulier sur les pluies journalières extrêmes n'est pas encore certain car peu de travaux y ont été consacrés en Afrique de l'Ouest. Dans ce contexte, il a été proposé de détecter d'éventuels tendances et ruptures dans les propriétés statistiques (moyenne, variance) des pluies journalières extrêmes à l'aide de tests statistiques locaux et régionaux. Pour détecter ces changements, les indices caractérisant la pluie maximale journalière annuelle (PJmaxan), le nombre annuel de jours de pluie dépassant 50 mm (NJsup50) et la contribution des pluies dépassant 50 mm dans les cumuls annuels (R(PJsup50/Pan)) ont été définis. L'analyse de 44 postes pluviométriques en Côte d'Ivoire sur la période 1942–2002 ne montre pas de changement généralisé ni en moyenne, ni en variance. Toutefois, en subdivisant la Côte d'Ivoire en régions climatiques homogènes, des tendances à la baisse ont été observées dans les régions IV (au Nord) et II (au Sud-Est).

Editeur Z.W. Kundzewicz; Assistant editeur G. Mahé

Citation Goula, A.B.T., Gneneyougo Soro, E., Kouassi, W. et Srohourou, B., 2012. Tendances et ruptures au niveau des pluies journalières extrêmes en Côte d'Ivoire (Afrique de l'Ouest). Hydrological Sciences Journal, 57 (6), 1067–1080.  相似文献   

Micro- and nano-textural evidence of Ti(–Ca–Fe) mobility during fluid–rock interactions in carbonaceous lawsonite-bearing rocks from New Zealand     

Matthieu?E.?GalvezEmail author  Olivier?Beyssac  Karim?Benzerara  Nicolas?Menguy  Sylvain?Bernard  Simon?C.?Cox 《Contributions to Mineralogy and Petrology》2012,164(5):895-914

Understanding the mobility of chemical elements during fluid–rock interactions is critical to assess the geochemical evolution of a rock undergoing burial and metamorphism and, more generally, to constrain the geochemical budget of the subduction factory. In particular, determining the behavior and mobility of Ti in aqueous fluids constitutes a great challenge that is still under scrutiny. Here, we study plant fossils preserved in blueschist metasedimentary rocks from the Marybank Formation (New Zealand). Using scanning and transmission electron microscopies (SEM and TEM), we show that the carbonaceous material (CM) composing the fossils contains abundant nano-inclusions of Ti- and Fe-oxides. These nanocrystals are mainly anatase, rutile, and Fe–Ti oxides. The mineral composition observed within the fossils is significantly different from that detected in the surrounding rock matrix. We propose that Ti and Fe might have been mobilized by the alteration of a detrital Ti–Fe-rich protolith during an early diagenetic event under acidic and reducing conditions. Aqueous fluids rich in organic ligands released by the degradation of organic matter may have been involved. Moreover, using mass balance and petrological observations, we show that the contrasted mineralogy between the rock matrix and the fossil CM might be the consequence of the chemical isolation of fossil CM during the prograde path of the rock. Such an isolation results from the early formation of quartz and Fe-rich phyllosilicate layers enclosing the fossil as characterized by SEM and TEM investigations. Overall, this study shows that investigating minerals associated with CM down to the nanometer scale in metamorphic rocks can provide a precious record of early prograde geochemical conditions.  相似文献   

Relations between the emplacement and fabric-forming conditions of the Kapitan-Dimitrievo pluton and the Maritsa shear zone (Central Bulgaria): magnetic and visible fabrics analysis     

Bernard?HenryEmail author  Kalin?Naydenov  Dimo?Dimov  Diana?Jordanova  Neli?Jordanova 《International Journal of Earth Sciences》2012,101(3):747-759

The Kapitan-Dimitrievo pluton was emplaced within the 15 km wide Maritsa shear zone during the Late Cretaceous. It has well-known U–Pb zircon age (78.54 ± 0.13 Ma) and appears as a late-syntectonic intrusion that marked the last ductile deformation in the Maritsa shear zone. Magnetite is believed to be the main carrier of the magnetic fabric in this pluton, and crystallized mainly late, after the main rock-forming minerals. Two fabrics are recorded, a visible syn-magmatic fabric (due to magma flow) and magnetic late-magmatic fabric (related to regional stresses). Although different, both are mainly related to the shearing along this shear zone. These results constrain in age the dextral strike-slip controlled emplacement and evolution of the Late Cretaceous plutons from Central Bulgaria.  相似文献   

A new mammalian fauna from the earliest Eocene (Ilerdian) of the Corbières (Southern France): palaeobiogeographical implications     

Bernard Marandat  Sylvain Adnet  Laurent Marivaux  Alain Martinez  Monique Vianey-Liaud  Rodolphe Tabuce 《Swiss Journal of Geoscience》2012,105(3):417-434

A new mammal fauna from the earliest Eocene of Le Clot (Corbières, Southern France) is described. Some taxa identified there, such as Corbarimys hottingeri and Paschatherium plaziati, allow a correlation with the previously described Corbières fauna of Fordones. Moreover, the presence at Le Clot of Lessnessina praecipuus, which is defined in Palette (Provence, Southern France) allows correlating both localities. All three of these localities are referred to the MP7 reference level, even if a direct correlation with the type locality of MP7 (Dormaal, Belgium) is not ascertained. A Southern Europe biochronological sequence is proposed for the beginning of the Eocene: Silveirinha, Fordones/Palette/Le Clot, Rians/Fournes. The diagnosis of a new species of a neoplagiaulacid multituberculate (?Ectypodus riansensis nov. sp.) is proposed. From a compilation of data concerning the earliest Eocene faunas from both Northern Europe and Southern Europe, we conclude that two faunas corresponding to two distinct palaeobiogeographical provinces existed in Western Europe. This faunal disparity, probably related to climatic differences, makes correlations particularly difficult between the two provinces.  相似文献   

Soil Organic Carbon mapping of partially vegetated agricultural fields with imaging spectroscopy     

Harm Bartholomeus  Lammert Kooistra  Antoine Stevens  Martin van Leeuwen  Bas van Wesemael  Eyal Ben-Dor  Bernard Tychon 《International Journal of Applied Earth Observation and Geoinformation》2011

Soil Organic Carbon (SOC) is one of the key soil properties, but the large spatial variation makes continuous mapping a complex task. Imaging spectroscopy has proven to be an useful technique for mapping of soil properties, but the applicability decreases rapidly when fields are partially covered with vegetation. In this paper we show that with only a few percent fractional maize cover the accuracy of a Partial Least Square Regression (PLSR) based SOC prediction model drops dramatically. However, this problem can be solved with the use of spectral unmixing techniques. First, the fractional maize cover is determined with linear spectral unmixing, taking the illumination and observation angles into account. In a next step the influence of maize is filtered out from the spectral signal by a new procedure termed Residual Spectral Unmixing (RSU). The residual soil spectra resulting from this procedure are used for mapping of SOC using PLSR, which could be done with accuracies comparable to studies performed on bare soil surfaces (Root Mean Standard Error of Calibration = 1.34 g/kg and Root Mean Standard Error of Prediction = 1.65 g/kg). With the presented RSU approach it is possible to filter out the influence of maize from the mixed spectra, and the residual soil spectra contain enough information for mapping of the SOC distribution within agricultural fields. This can improve the applicability of airborne imaging spectroscopy for soil studies in temperate climates, since the use of the RSU approach can extend the flight-window which is often constrained by the presence of vegetation.  相似文献