Test of three methods to detect the overbank flow from water level time‐series analysis     

O. Navratil  M. B. Albert  P. Breil 《水文研究》2010,24(17):2452-2464

In this study, we propose to identify morphological and hydraulic characteristics related to overbank flows in the water level time‐series available at many gauged stations. The results obtained at 13 river stations (the catchment sizes vary from 10 to 1700 km² with contrasted geology, land use and rainfalls regime) show that overflow mechanisms at the river‐reach scale can be systematically identified in the water level frequency distribution estimated with the peaks‐over‐threshold (POT) method. A first level (Lts1) was in the range of the incipient flooding onto the floodplain. Even if the definition of this level is variable in terms of flooded area at the reach scale, this method can be useful in providing a first estimation of the bankfull level for many gauged stations, without complex and costly field surveys. A second level (Lts2) was systematically detected on average 38 cm above the topographic flat floodplain elevation. The Lts2 inflection in the water‐level frequency distribution is assumed to reflect a composite effect of catchment hydrology and local hydraulics and channel geometry, without possibility to make a clear distinction between both processes at the moment. The local or reach scale effect would probably play an essential role in the frequency distribution as flood attenuation at catchment scale may explain the inflection Lts2 at only three sites. In light of the knowledge acquired in laboratory flumes with compound channels, most of the time Lts2 level would correspond to the level of resumption of flow both in the main channel and the floodplain. Once this method is validated in various physiographic contexts, it should apply to many hydrometric stations for both synchronic (e.g. regional analysis) and diachronic analysis (e.g. evolution over time of the bankfull discharge) to evaluate anthropic impacts on river morphology. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Spitzer spectroscopy of carbon stars in the Small Magellanic Cloud     

Eric Lagadec  Albert A. Zijlstra  G. C. Sloan  Mikako Matsuura  Peter R. Wood  Jacco Th. van Loon  G. J. Harris  J. A. D. L. Blommaert  S. Hony  M. A. T. Groenewegen  M. W. Feast  P. A. Whitelock  J. W. Menzies  M.-R. Cioni 《Monthly notices of the Royal Astronomical Society》2007,376(3):1270-1284

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The trophic roles of microzooplankton in marine systems   总被引：4，自引：1，他引：3  

Calbet  Albert 《ICES Journal of Marine Science》2008,65(3):325-331

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Multi-proxy climate and environmental records from a Holocene eutrophic mire,southern taiga subzone,West Siberia     

Irina V. Kurina  Elena E. Veretennikova  Anna A. Il’ina  Marina L. Egorova  Lyudmila V. Salisch  Vladimir N. Dolgin  Albert V. Udaloi  Evgeniya A. Golovatskaya  Egor A. Dyukarev  Sergei V. Smirnov 《Boreas: An International Journal of Quaternary Research》2023,52(2):223-239

Palaeoenvironmental reconstructions from peat are strongly focused on ombrotrophic mires, but this study demonstrates that eutrophic mires can also be used. A multi-proxy approach was applied to a eutrophic mire on a floodplain terrace in the southern taiga of West Siberia. The results of the reconstruction were considered in the wide geographic context of the surrounding regions, including Siberia and Central Asia. Different palaeoecological proxies (analysis of plant macrofossils, testate amoebae, oribatid mites, molluscs, peat humification, ash content and spectral characteristics of humic acids) were used in this study. The results of different proxies showed a high level of consistency among themselves, which allowed for a robust interpretation of Holocene mire development. Throughout the ~7800 years history of the mire, there was a high level of surface wetness. The presence of mineral matter in the peat between 7800 and 5100 cal. a BP indicates regular flooding caused by the intensive fluvial activity, apparently resulting from increased precipitation. This was followed by a trend towards a gradual decrease in surface wetness from conditions of high surface moisture (stagnant water) between 5100 and 3000 cal. a BP to present day conditions of moderate surface moisture with a water table slightly below the mire surface. This pattern is consistent with the well-documented long-term trend from palaeoecological records throughout the taiga and arctic zones in West Siberia and central arid Asia. Our data further support the idea that the westerlies were the dominant driver of climate for the southern taiga of West Siberia during the Middle to Late Holocene.  相似文献   

Planning for resettlement: building partnerships for,by, and with Indigenous peoples     

Kumasaka  Osamu  Bronen  Robin  Harrington  Elise  Knox-Hayes  Janelle  Laska  Shirley  Naquin  Albert  Patrick  Andy  Peterson  Kristina  Tom  Stanislaus 《GeoJournal》2021,87(2):307-327

Efforts in the United States to plan or implement relocation in response to climate risks have struggled to improve material conditions for participants, to incorporate local knowledge, and to keep communities intact. Mixed methodologies of community geography provide an opportunity for dialogue and knowledge-sharing to collaboratively diagnose the challenges of climate adaptation led by communities. In this article, we advance a participatory practice model for the co-creation of knowledge initiated during a two-day workshop with members from the Biloxi-Chitimacha-Choctaw Tribe from Isle de Jean Charles in Louisiana, Yup’ik people from Newtok Village in Alaska, and researchers from the MIT Resilient Communities Lab. Building on prior scholarship of indigenizing climate change research, this article shares the experience of the workshop to support knowledge exchange and dialogue, with the goal of understanding how to build participatory and non-extractive community-academic partnerships. We reflect on the community values and principles used to guide this workshop to inform more inclusive and co-produced research partnerships, and pedagogies that can improve and assist the self-determination of groups impacted by climate change. Workshop presentations and discussions highlight interconnected themes of resources, systems & structures, regulatory imbalance, and resilience that underpin climate resettlement. We reflect on the narratives presented by members of both Indigenous tribes and NGO partners that illustrate the shortcomings of resettlement planning practices past and present as perpetuating existing inequality. In response to this structured knowledge exchange, we identify potential roles for community-academic partnerships that aim to improve the equity of existing resettlement models. We propose approaches for incorporating traditional knowledge into the pedagogy, discourse, and practice of academic planning programs.

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Metal-rich carbon stars in the Sagittarius dwarf spheroidal galaxy     

Eric Lagadec  Albert A. Zijlstra  G. C. Sloan  Peter R. Wood  Mikako Matsuura  Jeronimo Bernard-Salas  J. A. D. L. Blommaert  M.-R. L. Cioni  M. W. Feast  M. A. T. Groenewegen  Sacha Hony  J. W. Menzies  J. Th. van Loon  P. A. Whitelock 《Monthly notices of the Royal Astronomical Society》2009,396(1):598-608

We present spectroscopic observations from the Spitzer Space Telescope of six carbon-rich asymptotic giant branch (AGB) stars in the Sagittarius dwarf spheroidal galaxy (Sgr dSph) and two foreground Galactic carbon stars. The band strengths of the observed C₂H₂ and SiC features are very similar to those observed in Galactic AGB stars. The metallicities are estimated from an empirical relation between the acetylene optical depth and the strength of the SiC feature. The metallicities are higher than those of the Large Magellanic Cloud, and close to Galactic values. While the high metallicity could imply an age of around 1 Gyr, for the dusty AGB stars, the pulsation periods suggest ages in excess of 2 or 3 Gyr. We fit the spectra of the observed stars using the dusty radiative transfer model and determine their dust mass-loss rates to be in the range  1.0–3.3 × 10⁻⁸ M_⊙ yr⁻¹  . The two Galactic foreground carbon-rich AGB stars are located at the far side of the solar circle, beyond the Galactic Centre. One of these two stars shows the strongest SiC feature in our present Local Group sample.  相似文献   

Towards Closing the Surface Energy Budget of a Mid-latitude Grassland   总被引：4，自引：1，他引：3  

Adrie F. G. Jacobs  Bert G. Heusinkveld  Albert A. M. Holtslag 《Boundary-Layer Meteorology》2008,126(1):125-136

Observations for May and August, 2005, from a long-term grassland meteorological station situated in central Netherlands were used to evaluate the closure of the surface energy budget. We compute all possible enthalpy changes, such as the grass cover heat storage, dew water heat storage, air mass heat storage and the photosynthesis energy flux, over an averaging time interval. In addition, the soil heat flux was estimated using a harmonic analysis technique to obtain a more accurate assessment of the surface soil heat flux. By doing so, a closure of 96% was obtained. The harmonic analysis technique appears to improve closure by 9%, the photosynthesis for 3% and the rest of the storage terms for a 3% improvement of the energy budget closure. For calm nights (friction velocity u _* < 0.1 m s⁻¹) when the eddy covariance technique is unreliable for measurement of the vertical turbulent fluxes, the inclusion of a scheme that calculates dew fluxes improves the energy budget closure significantly.  相似文献   

Gravity currents down a slope in deceleration phase     

Albert Dai  Marcelo H. García 《Dynamics of Atmospheres and Oceans》2010

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Fractures,hydrothermal alterations and permeability in the Soultz Enhanced Geothermal System     

Béatrice Ledésert  Ronan Hebert  Albert Genter  Danièle Bartier  Norbert Clauer  Céline Grall 《Comptes Rendus Geoscience》2010,342(7-8):607-615

Borehole studies of the Soultz-sous-Forêts granite are dedicated to deep geothermics. The hydraulic properties of the reservoir are mainly controlled by the occurrence of some altered cataclastic shear zones showing a low natural permeability characterized by the occurrence of brines. Those zones show a fracture cluster organisation with sealed fractures of various types (post-filled joints, sheared fractures, veins). The main hydrothermal deposits observed within the permeable zones are geodic quartz, carbonates, illite and more locally sulphides. The fracture wall–rocks are intensely transformed: dissolution of igneous minerals, crystallization of new minerals, porosity and permeability increase. It is important to characterize the newly-formed minerals in order to choose the reagents used to improve the permeability of the exchanger by chemical stimulations. This article represents a synthesis of the studies completed by the authors between 1990 and 2008 on the fracture networks, hydrothermal alterations and mineral crystallizations they induced and data about the flow pathways in the exchanger.  相似文献   

Structure of the low permeable naturally fractured geothermal reservoir at Soultz     

Chrystel Dezayes  Albert Genter  Benoît Valley 《Comptes Rendus Geoscience》2010,342(7-8):517-530

The permeability of the granite geothermal reservoir of Soultz is primarily related to major fracture zones, which, in turn, are connected to dense networks of small-scale fractures. The small-scale fractures are nearly vertical and the major direction is about N0°E. This direction differs from that of the Rhine Graben, which is about N20°E to N45°E in northern Alsace. A total of 39 fracture zones, with a general strike of N160°E, have been identified in six wells between 1400 and 5000 m depth. These fracture zones are spatially concentrated in three clusters. The upper cluster at 1800–2000 m True Vertical Depth (TVD) is highly permeable. At 3000–3400 m TVD, the intermediate cluster in composed of a dense network developed in an altered matrix and forms the upper reservoir. In the lower part of the wells, the deeper cluster appears as a fractured reservoir developed within a low permeable matrix. Fracture zones represent a key element to take into account for predicting the geothermal reservoir life time submitted to various thermo-hydromechanical and chemical processes generated by hydraulic or chemical stimulations and by hydraulic circulation tests related to long-term exploitation.  相似文献