Cenozoic denudation in the Marrakech High Atlas,Morocco: insight from apatite fission‐track thermochronology     

Yves Missenard  Omar Saddiqi  Jocelyn Barbarand  Pascale Leturmy  Geoffrey Ruiz  Fatima‐Zahra El Haimer  Dominique Frizon de Lamotte 《地学学报》2008,20(3):221-228

In North Africa, the High Atlas belt culminates at more than 4000 m. In Morocco, recent work shows that a lithospheric thinning explains about 1000 m of the mean topography, the remaining topography being related to crustal shortening. We combine regional geology with new apatite fission‐track (AFT) ages to constrain the timing of these events in the Marrakech High Atlas (MHA). In the inner belt, 10 AFT ages are comprised between 9 ± 1 and 27 ± 3 Ma. These Neogene ages indicate that the MHA underwent significant denudation during that time. In the southern foreland domain of the belt, three samples give scattered AFT ages between 27 ± 2 and 87 ±5 Ma. Geological evidences allow us to constrain the age of a major denudation event during Middle Miocene age. We propose that it is linked to the thermal doming highlighted in the whole Moroccan Atlas domain.  相似文献   

Towards a dedicated impact portal to bridge the gap between the impact and climate communities : Lessons from use cases     

Céline Déandreis  Christian Pagé  Pascale Braconnot  Lars Bärring  Edoardo Bucchignani  Wim Som de Cerff  Ronald Hutjes  Sylvie Joussaume  Constantin Mares  Serge Planton  Maarten Plieger 《Climatic change》2014,125(3-4):333-347

Future climate evolution is of primary importance for the societal, economical, political orientations and decision-making. It explains the increasing use of climate projections as input for quantitative impact studies, assessing vulnerability and defining adaptation strategies in different sectors. Here we analyse 17 national and representative use cases so as to identify the diversity of the demand for climate information depending on user profiles as well as the best practices, methods and tools that are needed to answer the different requests. A particular emphasis is put on the workflow that allows to translate climate data into suitable impact data, the way to deal with the different sources of uncertainty and to provide a suited product to users. We identified three complementary tools to close the gap between climate scientists and user needs: an efficient interface between users and providers; an optimized methodology to handle user requests and a portal to facilitate access to data and elaborated products. We detail in the paper how these three tools can limit the intervention of experts, educate users, and lead to the production of useful information. This work provides the basis on which the ENES (European Network for Earth System Modelling) Portal Interface for the Climate Impact Communities is built.  相似文献   

Impact Assessment of Pumping Parameters on Groundwater Bacterial Communities     

Noam Shani  Vasantha Aravinthan  Pierre Rossi  Guillaume Laulan  Pascale Ducommun  Christof Holliger 《Ground Water Monitoring & Remediation》2013,33(2):31-37

Groundwater microbial community samples are traditionally collected using pumping techniques optimized for groundwater chemistry assessment, although the impact of groundwater pumping parameters on apparent bacterial community structures (BCSs) is not really known. We therefore studied the impact of pumping lift, flow regime, and tubing material on BCS, which were analyzed by terminal‐restriction fragment length polymorphism (T‐RFLP). Ruzicka dissimilarity coefficients were calculated between T‐RFLP profiles to assess disparities between BCS. Variations in pumping lift, flow regime, and tubing material did not affect the apparent BCS in experiments using a homogenous water system under laboratory conditions showing that the conditions within the tube had no detectable effect on BCS. However, pumping groundwater from aquifer monitoring wells at different flow rates in the field revealed a significant impact on the apparent BCS. Water samples collected from fine sediment were the most affected by the pumping flow rate.  相似文献   

Improving the resilience of existing built assets to earthquake induced liquefaction disaster events     

Jones  Keith G.  Morga  Mariantonietta  Wanigarathna  Nadeeshani  Pascale  Federica  Meslem  Abdelghani 《Bulletin of Earthquake Engineering》2021,19(10):4145-4169

Bulletin of Earthquake Engineering - LIQUEFACT was a EU H2020 funded project to investigate earthquake induced liquefaction potential across Europe and develop a series of tools to understand...  相似文献   

First Mass-resolved Measurement of High-Energy Cosmic-Ray Antiprotons     

Bergström D  Boezio M  Carlson P  Francke T  Grinstein S  Khalchukov F  Suffert M  Hof M  Kremer J  Menn W  Simon M  Stephens SA  Ambriola ML  Bellotti R  Cafagna F  Ciacio F  Circella M  De Marzo C  Finetti N  Papini P  Piccardi S  Spillantini P  Bartalucci S  Ricci M  Casolino M  De Pascale MP  Morselli A  Picozza P  Sparvoli R  Bonvicini V  Schiavon P  Vacchi A  Zampa N  Mitchell JW  Ormes JF  Streitmatter RE  Bravar U  Stochaj SJ 《The Astrophysical journal》2000,534(2):L177-L180

We report new results for the cosmic-ray antiproton-to-proton ratio from 3 to 50 GeV at the top of the atmosphere. These results represent the first measurements, on an event-by-event basis, of mass-resolved antiprotons above 18 GeV. The results were obtained with the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas-RICH (Ring-Imaging Cerenkov) counter and a silicon-tungsten imaging calorimeter. The RICH detector was the first ever flown that is capable of identifying charge-one particles at energies above 5 GeV. The spectrometer was flown on 1998 May 28-29 from Fort Sumner, New Mexico. The measured p&d1;/p ratio is in agreement with a pure secondary interstellar production.  相似文献   

Spatial patterns of water surface topography at a river confluence     

Pascale M. Biron  Antoine Richer  Alistair D. Kirkbride  Andr G. Roy  Sangsoo Han 《地球表面变化过程与地形》2002,27(9):913-928

Understanding flow structures in river confluences has largely been the product of interpretations made from measured flow velocity data. Here, we turn the attention to the investigation of the patterns of both the average and standard deviations of the micro‐topography of the water surface at an asymmetrical natural discordant confluence for different flow conditions. Water surface topography is measured using a total station to survey the position of a reflector mounted on a custom‐built raft. To limit error problems related to changes in the water level, measurements are taken and analysed by cross‐stream transects where five water surface profiles are taken before moving to the next transect. Three‐dimensional numerical simulations of the flow dynamics at the field site are used to examine predicted water surface topography for a steady‐state situation. The patterns are interpreted with respect to flow structure dynamics, visual observations of boils, and bed topography. Results indicate that coherent patterns emerge at the water surface of a discordant bed confluence for different flow conditions. The zone of stagnation and the mixing layer are characterized by super‐elevation, a lateral tilt is present at the edge of the mixing layer, and a zone of super‐elevation is present on the tributary side at the downstream junction corner. The latter seems associated with periodical upwelling and is not present in the numerical simulations that do not take into account instantaneous velocity fluctuations. Planform curvature, topographic steering related to the tributary mouth bar, and turbulent structures associated with the mixing layer all play a key role in the pattern of both the average and standard deviation of the water surface topography at confluences. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The influence of the coast on the dynamics of upwelling fronts: Part I. Laboratory experiments     

Pascale Bouruet-Aubertot  P. F. Linden 《Dynamics of Atmospheres and Oceans》2002,36(1-3)

We describe laboratory experiments on the instability and later evolution of a front in a two-layer rotating fluid. In particular, we focus on the influence of a nearby boundary on instability growth and eddy formation. The front is produced through the adjustment of a buoyant fluid initially confined within a bottomless cylinder. Typically a front in quasi-cyclostrophic balance establishes after two rotation periods, after which it becomes unstable. Measurements of the velocity and vorticity fields at the surface are made which provide detailed information on the evolution of the front as the instability grows to finite amplitude. We focus on the time evolution of the vorticity and distinguish between the cyclonic and anticyclonic components. The spatial averages of the cyclonic and anticyclonic vorticity first grow exponentially. This growth saturates when eddies form and are advected across the front. The growth rate depends upon two nondimensional parameters: the width W of the upwelling region in units of the internal radius of deformation and the depth ratio δ between the two layers. Measurements of the growth rates for the average of the cyclonic and anticyclonic vorticity are compared to the values inferred from a simplified model for baroclinic instability. A good agreement is obtained when the front develops far from the boundary (i.e. W1). However, the agreement is only qualitative when the front is near the boundary (i.e. W1). We find that, as W decreases, the growth of cyclonic eddies consisting of dense—“coastal”—water is enhanced compared to that of anticyclonic vorticity consisting of buoyant—“off-shore”—water. This crucial effect of the boundary with respect to the instability of the front has significant impact on exchanges across the front.  相似文献   

On the influence of RF absorbing material on the GNSS position     

Wim Aerts  Carine Bruyninx  Pascale Defraigne  Guy A. E. Vandenbosch  Philipp Zeimetz 《GPS Solutions》2016,20(1):1-7

Reflections of the GNSS signal around the antenna induce an error in the measurement of the satellite–receiver distance and therefore should be avoided as much as possible. One solution often used to mitigate these reflections is to apply radio frequency (RF) absorbing material to the antenna, its support or its site. Such material could however alter the antenna phase delay and, in turn, alter the position as calculated from the GNSS observations. We explain under which conditions the RF material will or will not alter the antenna phase delay, and hence in which conditions a re-calibration of the antenna is necessary after the installation of absorbing material. Furthermore, rules of thumb are given to install the material in such a way that re-calibration can be avoided. Some basic theory and measurements of the influence of RF material are reviewed. An application to a real life absorber setup similar to one of the International GNSS Service reference stations is then discussed, and the position offset due to the absorbing material is demonstrated. The topics discussed can serve station managers to limit effects of absorbing material and take precautions to avoid a position bias.  相似文献   

Spatial stabilization and intensification of moistening and drying rate patterns under future climate change     

Yann Chavaillaz  Sylvie Joussaume  Sandrine Bony  Pascale Braconnot 《Climate Dynamics》2016,47(3-4):951-965

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Quantifying atmosphere and ocean origins of North American precipitation variability     

Zhang  Honghai  Seager  Richard  He  Jie  Diao  Hansheng  Pascale  Salvatore 《Climate Dynamics》2021,56(11):4051-4074

How atmospheric and oceanic processes control North American precipitation variability has been extensively investigated, and yet debates remain. Here we address this question in a 50 km-resolution flux-adjusted global climate model. The high spatial resolution and flux adjustment greatly improve the model’s ability to realistically simulate North American precipitation, the relevant tropical and midlatitude variability and their teleconnections. Comparing two millennium-long simulations with and without an interactive ocean, we find that the leading modes of North American precipitation variability on seasonal and longer timescales exhibit nearly identical spatial and spectral characteristics, explained fraction of total variance and associated atmospheric circulation. This finding suggests that these leading modes arise from internal atmospheric dynamics and atmosphere-land coupling. However, in the fully coupled simulation, North American precipitation variability still correlates significantly with tropical ocean variability, consistent with observations and prior literature. We find that tropical ocean variability does not create its own type of atmospheric variability but excites internal atmospheric modes of variability in midlatitudes. This oceanic impact on North American precipitation is secondary to atmospheric impacts based on correlation. However, relative to the simulation without an interactive ocean, the fully coupled simulation amplifies precipitation variance over southwest North America (SWNA) during late spring to summer by up to 90%. The amplification is caused by a stronger variability in atmospheric moisture content that is attributed to tropical Pacific sea surface temperature variability. Enhanced atmospheric moisture variations over the tropical Pacific are transported by seasonal mean southwesterly winds into SWNA, resulting in larger precipitation variance.

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