Statistical detection and no-detection of rainfall change trends and breaks in semiarid Tunisia—50+ years over the Merguellil agro-hydro-climatic reference basin     

Sameh Chargui  Asma Jaberi  Christophe Cudennec  Fethi Lachaal  Rogez Calvez  Mohamed Slimani 《Arabian Journal of Geosciences》2018,11(21):675

Rainfall variability is an important feature of semiarid climates with major effects on hydrology, and beyond on key water-dependent societal aspects. Eventual changes in rainfall variability are a strong driver of change of hydrological processes, resources, and hazards, up to catchment signatures and spatial arrangements. We deal with observed precipitations and subsequent statistical coefficients available from a network of 15 rainfall gauges over and around the Merguellil catchment (1175 km²), with series ranging up to the 1961–2013 period. We look for eventual annual trends and breakpoints with a set of methods: Mann Kendall test, Pettitt test, Hubert segmentation procedure, Buishand U statistic, and Lee Heghinian Bayesian procedure. The results underline oscillation of dry and wet periods; several studied rain gauges (Tella, Oueslatia forêt, Majbar, Kesra forêt, Henchir Bhima, and Haffouz DGRE) denote significant trends in annual precipitation. Some breaks are detected but they are not synchronous. These methods reveal the variability of rainfall regimes in the semiarid region and provide a synoptic view of detection and no-detection of symptoms of change. This work gives opportunities to water stakeholders and climate experts in understanding the relationships between climate variability and water availability.  相似文献   

Late Pleistocene (MIS 3–4) climate inferred from micromammal communities and δO of rodents from Les Pradelles,France     

Aurélien Royer  Christophe Lécuyer  Sophie Montuire  Gilles Escarguel  François Fourel  Alan Mann  Bruno Maureille 《Quaternary Research》2013

The middle Paleolithic stratigraphic sequence of Les Pradelles (Charente, France) spans from the end of Marine Isotope Stage (MIS) 4 until the middle of MIS 3. Micromammal remains are present in all the stratigraphic levels, offering a rare opportunity to address the questions of both environmental and climatic fluctuations throughout this period. Climate modes were studied through the taphonomy, biodiversity and oxygen isotope compositions of phosphate (δ¹⁸O_p) from 66 samples of rodent tooth enamel. The δ¹⁸O_p values from the lower sedimentary levels provide summer mean air temperatures of 19 ± 2°C (level 2/1) and of 16 ± 2°C (levels 2A, 2B and 4A). Within the middle of sequence (level 4B), a paleobiodiversity change can be identified with an increase of Dicrostonyx torquatus, which is associated with the largest amplitude in δ¹⁸O_p values and the highest maximal δ¹⁸O_p values. At the top of the sequence (level 5-2), a biodiversity change is observed with the increase of Microtus arvalis, but without any change in δ¹⁸O_p values. The association of cold rodent species with unexpected high and large amplitudes in the δ¹⁸O_p values of their teeth, possibly indicative of aridity, suggests their deposition during a Heinrich event.  相似文献   

Incorporating elevation in rainfall interpolation in Tunisia using geostatistical methods     

Haifa Feki  Mohamed Slimani  Christophe Cudennec 《水文科学杂志》2013,58(7):1294-1314

Abstract

This paper compares the performance of three geostatistical algorithms, which integrate elevation as an auxiliary variable: kriging with external drift (KED); kriging combined with regression, called regression kriging (RK) or kriging after detrending; and co-kriging (CK). These three methods differ by the way by in which the secondary information is introduced into the prediction procedure. They are applied to improve the prediction of the monthly average rainfall observations measured at 106 climatic stations in Tunisia over an area of 164 150 km² using the elevation as the auxiliary variable. The experimental sample semivariograms, residual semivariograms and cross-variograms are constructed and fitted to estimate the rainfall levels and the estimation variance at the nodes of a square grid of 20 km?×?20 km resolution and to develop corresponding contour maps. Contour diagrams for KED and RK were similar and exhibited a pattern corresponding more closely to local topographic features when (a) the network is sparse and (b) the rainfall–elevation correlation is poor, while CK showed a smooth zonal pattern. Smaller prediction variances are obtained for the RK algorithm. The cross-validation showed that the RMSE obtained for CK gave better results than for KED or RK.

Editor D. Koutsoyiannis; Associate editor C. Onof

Citation Feki, H., Slimani, M., and Cudennec, C., 2012. Incorporating elevation in rainfall interpolation in Tunisia using geostatistical methods. Hydrological Sciences Journal, 57 (7), 1294–1314.  相似文献   

Editorial – GGR Cutting Edge Reviews     

Thomas Meisel  Michel Grégoire  Bill McDonough  Christophe Quétel  Jon Woodhead 《Geostandards and Geoanalytical Research》2013,37(2):109-109

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Editorial – New GGR Editorial Board     

Thomas Meisel  Michel Grégoire  Bill McDonough  Christophe Quétel  Jon Woodhead  Edward Williams 《Geostandards and Geoanalytical Research》2013,37(3):237-242

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Organic sedimentary deposits in Titan’s dry lakebeds: Probable evaporite     

Jason W. Barnes  Jacob Bow  Jacob Schwartz  Robert H. Brown  Jason M. Soderblom  Alexander G. Hayes  Graham Vixie  Stéphane Le Mouélic  Sebastien Rodriguez  Christophe Sotin  Ralf Jaumann  Katrin Stephan  Laurence A. Soderblom  Roger N. Clark  Bonnie J. Buratti  Kevin H. Baines  Philip D. Nicholson 《Icarus》2011,216(1):136-140

We report the discovery of organic sedimentary deposits at the bottom of dry lakebeds near Titan’s north pole in observations from the Cassini Visual and Infrared Mapping Spectrometer (VIMS). We show evidence that the deposits are evaporitic, making Titan just the third known planetary body with evaporitic processes after Earth and Mars, and is the first that uses a solvent other than water.  相似文献   

Saturn’s F ring grains: Aggregates made of crystalline water ice     

Sanaz Vahidinia  Jeffrey N. Cuzzi  Matt Hedman  Bruce Draine  Roger N. Clark  Ted Roush  Gianrico Filacchione  Philip D. Nicholson  Robert H. Brown  Bonnie Buratti  Christophe Sotin 《Icarus》2011,215(2):682-694

We present models of the near-infrared (1-5 μm) spectra of Saturn’s F ring obtained by Cassini’s Visual and Infrared Mapping Spectrometer (VIMS) at ultra-high phase angles (177.4-178.5°). Modeling this spectrum constrains the size distribution, composition, and structure of F ring particles in the 0.1-100 μm size range. These spectra are very different from those obtained at lower phase angles; they lack the familiar 1.5 and 2 μm absorption bands, and the expected 3 μm water ice primary absorption appears as an unusually narrow dip at 2.87 μm. We have modeled these data using multiple approaches. First, we use a simple Mie scattering model to constrain the size distribution and composition of the particles. The Mie model allows us to understand the overall shapes of the spectra in terms of dominance by diffraction at these ultra-high phase angles, and also to demonstrate that the 2.87 μm dip is associated with the Christiansen frequency of water ice (where the real refractive index passes unity). Second, we use a combination of Mie scattering with Effective Medium Theory to probe the effect of porous (but structureless) particles on the overall shape of the spectrum and depth of the 2.87 μm band. Such simple models are not able to capture the shape of this absorption feature well. Finally, we model each particle as an aggregate of discrete monomers, using the Discrete Dipole Approximation (DDA) model, and find a better fit for the depth of the 2.87 μm feature. The DDA models imply a slightly different overall size distribution. We present a simple heuristic model which explains the differences between the Mie and DDA model results. We conclude that the F ring contains aggregate particles with a size distribution that is distinctly narrower than a typical power law, and that the particles are predominantly crystalline water ice.  相似文献   

SPICES: spectro-polarimetric imaging and characterization of exoplanetary systems     

Anthony Boccaletti  Jean Schneider  Wes Traub  Pierre-Olivier Lagage  Daphne Stam  Raffaele Gratton  John Trauger  Kerri Cahoy  Frans Snik  Pierre Baudoz  Raphael Galicher  Jean-Michel Reess  Dimitri Mawet  Jean-Charles Augereau  Jenny Patience  Marc Kuchner  Mark Wyatt  Eric Pantin  Anne-Lise Maire  Christophe Vérinaud  Samuel Ronayette  Didier Dubreuil  Michiel Min  Michiel Rodenhuis  Dino Mesa  Russ Belikov  Olivier Guyon  Motohide Tamura  Naoshi Murakami  Ingrid Mary Beerer 《Experimental Astronomy》2012,34(2):355-384

SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks in the visible (450?C900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/2022, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5?C10?AU) from nearby stars (<25 pc) with masses ranging from a few Jupiter masses to Super Earths (??2 Earth radii, ??10 M_??) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System.  相似文献   

OSS (Outer Solar System): a fundamental and planetary physics mission to Neptune, Triton and the Kuiper Belt     

B. Christophe  L. J. Spilker  J. D. Anderson  N. André  S. W. Asmar  J. Aurnou  D. Banfield  A. Barucci  O. Bertolami  R. Bingham  P. Brown  B. Cecconi  J. -M. Courty  H. Dittus  L. N. Fletcher  B. Foulon  F. Francisco  P. J. S. Gil  K. H. Glassmeier  W. Grundy  C. Hansen  J. Helbert  R. Helled  H. Hussmann  B. Lamine  C. L?mmerzahl  L. Lamy  R. Lehoucq  B. Lenoir  A. Levy  G. Orton  J. Páramos  J. Poncy  F. Postberg  S. V. Progrebenko  K. R. Reh  S. Reynaud  C. Robert  E. Samain  J. Saur  K. M. Sayanagi  N. Schmitz  H. Selig  F. Sohl  T. R. Spilker  R. Srama  K. Stephan  P. Touboul  P. Wolf 《Experimental Astronomy》2012,34(2):203-242

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Twenty-three unsolved problems in hydrology (UPH) – a community perspective     

Günter Blöschl  Marc F.P. Bierkens  Antonio Chambel  Christophe Cudennec  Georgia Destouni  Aldo Fiori 《水文科学杂志》2013,58(10):1141-1158

ABSTRACT

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.  相似文献