Search results for "Ada"
showing 10 items of 10244 documents
Hydrostratigraphic characterization of glaciofluvial deposits underlying an infiltration basin using ground penetrating radar.
2008
14 pages; International audience; An understanding of the heterogeneity of quaternary gravelly deposits is required to predict flow and contaminant transfer through these formations. In such deposits, preferential flow paths can lead to contamination at depths greater than predicted under the assumption of a homogeneous medium. The difficulties in characterizing their complex structure with conventional methods represent an obstacle for this prediction. In this study, we developed an approach relying on the use of ground penetrating radar (GPR) for the detection of sedimentary depositional units. A genetic interpretation of the radar stratigraphy allowed us to construct a distribution model…
Estimating Gravimetric Moisture of Vegetation Using an Attenuation-Based Multi-Sensor Approach
2018
Estimating parameters for global climate models via combined active and passive microwave remote sensing data has been a subject of intensive research in recent years. A variety of retrieval algorithms has been proposed for the estimation of soil moisture, vegetation optical depth and other parameters. A novel attenuation-based retrieval approach is proposed here to globally estimate the gravimetric moisture of vegetation (m g ) and retrieve information about the amount of water [kg] per amount of wet vegetation [kg]. The parameter m g is particularly interesting for agro-ecosystems, to assess the status of growing vegetation. The key feature of the proposed approach is that it relies on mu…
First M87 Event Horizon Telescope Results. I. the Shadow of the Supermassive Black Hole
2019
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux rati…
A Comparison between Drifter and X-Band Wave Radar for Sea Surface Current Estimation
2016
This paper deals with exploitation of the wave radar system for sea surface current estimation in a coastal zone. In particular, we present the results of the processing of the radar data collected by an X-band marine radar installed in Capo Granitola site, which is located in the south-west part of Sicily, on 15 May 2015. The effectiveness of the data processing is analyzed by comparing the wave radar estimated sea surface current with that provided by the Lagrangian drifters along its movement trajectory. During the measurement campaign, three drifter releases are carried out and for each one the comparison is provided in terms of the mean error and standard deviation. In addition, we rep…
Analysis of the radar vegetation index and assessment of potential for improvement
2018
The Radar Vegetation Index (RVI) is widely applied to indicate vegetation cover. The index includes the backscattering intensities of co- and cross-polarization that do not only contain information coming from vegetation scattering at longer wavelength (L-band), but also from the soil underneath. A forward modelling approach using active and passive microwave-derived parameters to obtain the scattering contribution of the soil is pursued. The idea of this research study is a subtraction of the attenuated soil scattering contribution from the measured backscattering intensities, to provide a clean vegetation-based solution, called improved RVI (RVII). For latter analysis, the vegetation volu…
Multi-centennial summer and winter precipitation variability in southern South America
2010
[1] We present the first spatially and temporally highly resolved gridded reconstruction of multi-centennial precipitation variability for southern South America (SSA). A novel reconstruction approach of deriving 10,000 ensemble members based on varying predictor networks and methodological settings allows the identification of spatiotemporal changes in SSA precipitation and associated uncertainties. The summer and winter reconstructions back to AD 1498 and AD 1590, respectively, provide new evidence for multi-centennial increase in summer precipitation and an opposing decrease in winter precipitation into the 20th century. The drying in winter is significant over large parts of SSA, wherea…
Un assemblage inhabituel d’insectivores au Miocène inférieur du Sud-Ouest de l’Europe : les talpidés et les dimylidés du bassin de Ribesalbes–Alcora …
2019
The Miocene record of talpids and dimylids in south-western Europe is very scarce. In the present work, we study for the first time the talpids and complete the description of the dimylids, already started with a new species of the genus Plesiodimylus from the Ribesalbes–Alcora Basin (MN4, lower Aragonian, early Miocene) by Crespo et al. (2018). The talpids recovered inRibesalbes–Alcora comprise themost common Desmanodon daamsi and Desmanella fejfari, for which the last known occurrence is recorded here. The dimylids comprise the species Plesiodimylus ilercavonicus, which expands the biostratigraphic record of the genus and species and has been found in a new site. On the other hand, we dis…
A 2500 year record of natural and anthropogenic soil erosion in South Greenland
2012
International audience; The environmental impact of the Norse landnám in Greenland has been studied extensively. But to date, no study has quantified the soil erosion that Norse agricultural practices are believed to have caused. To resolve this problem, a high resolution sedimentary record from Lake Igaliku in South Greenland is used to quantitatively reconstruct 2500 years of soil erosion driven by climate and historical land use. An accurate chronology allows for the estimation of detritic fluxes and their uncertainties. Land clearance and the introduction of grazing livestock by the Norse around 1010 AD caused an acceleration of soil erosion up to 8 mm/century in 1180 AD which is two-fo…
Investigating the Local Reservoir Age and Stable Isotopes of Shells from Southeast Arabia
2016
AbstractWe recently started a systematic approach to determine the reservoir age in southeast Arabia and its dependence on mollusk species and their environment. This part of the study concentrates on local reservoir age and stable isotopes of the lagoonal species Terebralia palustris and Anadara uropigimelana at Khor Kalba, Oman Sea. Environmental and nutritive influences on mollusks are reflected in the radiocarbon and stable isotope signal. We found a local reservoir age of A. uropigimelana of about 940 yr and that of T. palustris as 800 yr. Sclerochronological analyses yielded information about seasonality of growth and death in A. uropigimelana. The modern shell of Periglypta reticulat…
Turia river delta and coastal barrier-lagoon of Valencia (Mediterranean coast of Spain): Geomorphological processes and global climate fluctuations s…
2019
Abstract Extensive drillings and 31 new C-14 datings were used to establish the geomorphological evolution of the Turia river delta and coastal barrier-lagoon system of Valencia (Spain) over the last three millennia. Integration of geomorphological, stratigraphic, malacological, sedimentological and geoarchaeological data enables us to relate river Turia avulsions and alluvial episodes to the development of coastal spits and barriers. Geomorphological changes in the study area may also be associated with global climate events, sea-level fluctuations or anthropogenic periods in the Turia catchment. Six phases may be differentiated: (1) a major early alluviation phase during the Iberian perio…