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101.
Yann Chavaillaz Sylvie Joussaume Amaury Dehecq Pascale Braconnot Robert Vautard 《Climatic change》2016,137(1-2):187-200
Most climatological studies characterize the future climate change as the evolution between a fixed current baseline and the future. However, as climate continues to change, ecosystems and societies will need to continuously adapt to a moving target. Here, we consider indicators of the pace of temperature change estimated from CMIP5 projections of an ensemble of climate models. We define the pace as a difference in relevant metrics between two successive 20-year periods, i.e. with a continually moving baseline. Under the strongest emission pathway (RCP8.5), the warming rate strongly increases, and peaks before 2080. All latitudes experience at least a doubling in the warming rate compared to the current period. Significant shifts in temperature distributions above twice the standard deviation between two successive 20-year periods expand from 9 % of continents on average currently to 41 % by 2060 onwards. In these regions, a warm year with a return period of about 50 years would become quite common 20 years later. The fraction of the world population exposed to such shifts will grow from 8 % to about 60 % on average, i.e. 6 billion people. Tropical areas are strongly affected, especially West Africa and South-East Asia. Low mitigation (RCP6.0) limits the warming rate to current values. Medium mitigation (RCP4.5) even reduces population exposure to significant shifts in temperature distributions to negligible values by the end of the century. Strong mitigation (RCP2.6) is the only option that generates a return to values similar to the historical period for all our indicators related to the pace of temperature change. This alternative way to analyze climate projections can yield new insights for the climate impacts and adaptation communities. 相似文献
102.
Rim Ladhar‐Chaabouni Amel Hamza‐Chaffai Yann Hardivillier Benoît Chénais Françoise Denis 《Marine Ecology》2010,31(2):355-363
The internal transcribed spacer 1 (ITS1) region of 29 individuals of Cerastoderma glaucum (from the Mediterranean Sea, the Atlantic and the North Sea) and 18 individuals of Cerastoderma edule (from the Atlantic and the North Sea) and the cytochrome c oxidase subunit I (COI) region of 43 individuals of C. glaucum (from the Mediterranean Sea, the Atlantic and the North Sea) and 9 individuals of C. edule (from the Atlantic and the North Sea) were PCR amplified and sequenced. The ITS1 sequences led us to describe 27 genetic haplotypes, while 21 genetic haplotypes were determined via the COI sequences. The ITS1 and the COI sequences revealed an important genetic variability within the Mediterranean population of C. glaucum, which contained two different phenotypes: orange foot and yellow foot. A genetic differentiation between the two phenotypes was revealed by the nucleotide diversity index (π) and is strengthened by the AMOVA analysis. This result leads us to suspect the presence of two different groups in the same population of C. glaucum. Nevertheless to be confirmed this hypothesis requires further studies using more locations and a larger number of sample sizes. 相似文献
103.
Marta M. Cassiano Pierre Kaufmann Rogério Marcon Amauri S. Kudaka Adolfo Marun Rodolfo Godoy Pablo Pereyra Arline M. Melo Hugo Levato 《Solar physics》2010,264(1):71-79
Solar observations in the mid-infrared 8 – 14 μm band continuum were carried out with cadence of 5 frames per second, in December 2007.
Rapid small heated sources, with a typical duration of the order of seconds, were found on the bright plage-like areas around
sunspots, in association with relatively weak GOES soft X-ray bursts. This work presents the analysis of fast mid-infrared
flashes detected during a GOES B2.0-class event on 10 December 2007, beginning at about 10:40 UT. Rapid brightness temperature
enhancements of 0.5 to 2.0 K were detected at the Earth by a microbolometer array, using a telescope with 10.5 cm diameter
aperture producing a diffraction-limited photometric beam of 25 arc sec. The minimum detectable temperature change was of
0.1 K. The corresponding fluxes are 30 – 130 solar flux units. At the solar surface the estimated rapid brightenings represented
a temperature enhancement of 50 – 150 K. 相似文献
104.
Youssef M.A. Hashash Séverine Levasseur Abdolreza Osouli Richard Finno Yann Malecot 《Computers and Geotechnics》2010
Performance observation is a necessary part of the design and construction process in geotechnical engineering. For deep urban excavations, empirical and numerical methods are used to predict potential deformations and their impacts on surrounding structures. Two inverse analysis approaches are described and compared for an excavation project in downtown Chicago. The first approach is a parameter optimization approach based on genetic algorithm (GA). GA is a stochastic global search technique for optimizing an objective function with linear or non-linear constraints. The second approach, self-learning simulations (SelfSim), is an inverse analysis technique that combines finite element method, continuously evolving material models, and field measurements. The optimization based on genetic algorithm approach identifies material properties of an existing soil model, and SelfSim approach extracts the underlying soil behavior unconstrained by a specific assumption on soil constitutive behavior. The two inverse analysis approaches capture well lateral wall deflections and maximum surface settlements. The GA optimization approach tends to overpredict surface settlements at some distance from the excavation as it is constrained by a specific form of the material constitutive model (i.e. hardening soil model); while the surface settlements computed using SelfSim approach match the observed ones due to its ability to learn small strain non-linearity of soil implied in the measured settlements. 相似文献
105.
Virginia Marcon Beth Hoagland Xin Gu Wenjing Liu Jason Kaye Roman A. DiBiase Susan L. Brantley 《地球表面变化过程与地形》2021,46(14):2807-2823
More above-ground biomass (kg m−2) grows in the northern Appalachian Mountains (USA) in forests on shale than on sandstone at all landscape positions other than ridgetops. This has been tentatively attributed to physical (rather than chemical) attributes of the substrates, such as elevation, particle size, and water capacity. However, shales have generally similar phosphorus (P) concentrations to sandstones and, in the Valley and Ridge province, they erode more quickly. This led us to hypothesize that faster replenishment of the lithogenic nutrient P in shale soils through erosion + soil production could instead control the differences in biomass. To test this, soils and foliage from 10 sites on shales and sandstones in the northern Appalachians from roughly the same elevation and aspect were analysed. We discovered that, when controlling for location, concentrations of bioavailable P in soils and P in foliage were higher and P resorbed from senescing red oak leaves was lower on slower-eroding sandstone than on faster-eroding shale. Lower resorption generally can be attributed to lower P limitation for trees. Further investigation of weathering and erosion on one of the sandstone–shale pairs within a larger, paired watershed study revealed that the differences in P concentrations in biomass and foliage between lithologies likely developed because sandstones act as ‘collectors’ that trap nutrients from residual and exogenous sources, while shales erode quickly and thus promote production of soil from bedrock that releases P to ecosystems. We concluded that the combined effects of differential rates of dust collection and erosion results in roughly equal biomass growing on sandstone and shale ridgetops. This work emphasizes the balance between a landscape's capacity to collect dust versus produce soil in controlling bioavailability of nutrients. 相似文献
106.
Jean-Yves Boisson Lucien Bertrand Jean-François Heitz Yann Golvan 《Hydrogeology Journal》2001,9(1):108-123
In the context of a research and development program on waste disposal, an experimental site (Tournemire tunnel, Aveyron,
France) was selected by the French Institute for Nuclear Protection and Safety (IPSN) in order to undertake studies on potential
fluid flow at different scales of space and time within a 250-m-thick argillaceous formation. The argillite has a low natural
water content (~3–5%) and very low radii access porosity. Diffusion (tritiated water) coefficients (1×10–12 to 2×10–11 m2/s) and hydraulic conductivities derived from different types of laboratory tests (10–14 to 10–13 m/s) are characteristics of a very low-permeable rock. In situ hydraulic tests (including long-term hydraulic-head measurements)
were used to obtain values for hydraulic head and hydraulic conductivity at a scale of 1–10 m (10–13 to 10–11 m/s). Despite uncertainties on these data (due to a scale factor, presence of fissures, and possible artefacts due to hydro-chemo-mechanical
coupling), it is expected that fluid flow is essentially governed by diffusion processes. Identification of possible natural
flows at larger scales of time and space was investigated using natural isotopic tracers from interstitial fluids. Modelling,
based on the deuterium profile along the clay formation and assuming pure diffusion processes, provides estimations of possible
flow times. However, lack of knowledge concerning the past geological evolution of the site and the possible role of a fracture
network do not permit reduction of uncertainties on these estimations at this stage.
Electronic Publication 相似文献
107.
The Gold Coast sandy beaches of Queensland (Australia) are exposed to energetic wave conditions. Storms, particularly tropical
cyclones, have a high potential of destruction. The Gold Coast has not experienced excessive erosive events over the past
30 years. However, some climate indicators suggest that cyclone frequency is likely to increase in response to global climate
change within the near future. Over a 2-month period in early 2006, beach surveys were undertaken with a theodolite total
station at four different sites. Offshore wave conditions were provided by SWAN regional wave modelling. During this study,
the Gold Coast was exposed to three major storms, the first one being the second most energetic over the past 30 years. Results
show a substantial variability of the beach response to these events along the Gold Coast, and that engineering structures
do not have marked effects. Easterly swells have the greatest impact on the Gold Coast sub-aerial beach morphology. When low
wave-energy conditions prevail, the southern Gold Coast beaches recover more quickly than the northern ones, as they are sheltered
from high SE waves and draw advantage from the artificial sand bypassing system. Nevertheless, the data show that the Gold
Coast beaches are exceedingly fragile. For instance, the early March decadal event considerably weakened the beaches, which
resulted in surprisingly high erosion rates all along the Gold Coast during the two following annual wave events. This study
suggests that the Gold Coast beaches would not be able to withstand the impact of an increased frequency of extreme events
similar in scale to those of 1967. 相似文献
108.
The south-eastern part of the European Variscan belt forms a zone composed of several crystalline segments: the External Crystalline Massifs of the western Alps, the Maures-Tanneron massif, also Corsica and Sardinia, which are mutually displaced due to the Alpine deformation of the European Paleozoic lithosphere. All these crystalline fragments record similar structural, metamorphic, geochronological and magmatic histories during Paleozoic times. In particular, the Late Carboniferous period (~320–300 Ma) is characterized by crustal-scale folding associated with strike-slip faulting and intracontinental basin formation. In this transpressive context, dome structures exhume partially-molten crust in convergent setting, which is in contradiction with generally accepted models of late orogenic collapse of the Variscan belt. It is suggested that this particular transpressive–obliquely convergent template, exemplified by tectonometamorphic evolution of the Maures-Tanneron massif, is valid for the whole eastern European Variscan margin. 相似文献
109.
110.
利用国家气候中心提供的1951—2012年逐日降水、温度、综合气象干旱指数、逐月NCEP/NCAR再分析资料等,采用REOF分析、动力诊断、相关分析以及合成分析等方法,从大气环流异常特征、高空急流与季风异常等方面揭示西北东部夏季极端干旱事件的可能机理。研究发现西北东部夏季发生极端干旱时,副热带急流轴"倾斜",且急流与东亚夏季风强度均处于相对偏弱阶段。极端干旱的成因研究表明:急流轴"倾斜"及其强度减弱导致西北东部地区高层大范围的异常辐合;该地区为水汽源区,对流层整层水汽收支显著亏损;此外,该地区低层盛行来自内陆干旱区的异常西南风,东亚夏季风强度偏弱,高低层配置及大尺度环流形势不利于降水产生。 相似文献