Coupled surface and subsurface flow modeling of natural hillslopes in the Aburrá Valley (Medellín,Colombia)     

Daniela Blessent  Janet Barco  André Guy Tranquille Temgoua  Oscar Echeverrri-Ramirez 《Hydrogeology Journal》2017,25(2):331-345

Numerical results are presented of surface-subsurface water modeling of a natural hillslope located in the Aburrá Valley, in the city of Medellín (Antioquia, Colombia). The integrated finite-element hydrogeological simulator HydroGeoSphere is used to conduct transient variably saturated simulations. The objective is to analyze pore-water pressure and saturation variation at shallow depths, as well as volumes of water infiltrated in the porous medium. These aspects are important in the region of study, which is highly affected by soil movements, especially during the high-rain seasons that occur twice a year. The modeling exercise considers rainfall events that occurred between October and December 2014 and a hillslope that is currently monitored because of soil instability problems. Simulation results show that rainfall temporal variability, mesh resolution, coupling length, and the conceptual model chosen to represent the heterogeneous soil, have a noticeable influence on results, particularly for high rainfall intensities. Results also indicate that surface-subsurface coupled modeling is required to avoid unrealistic increase in hydraulic heads when high rainfall intensities cause top-down saturation of soil. This work is a first effort towards fostering hydrogeological modeling expertise that may support the development of monitoring systems and early landslide warning in a country where the rainy season is often the cause of hydrogeological tragedies associated with landslides, mud flow or debris flow.  相似文献   

Kinematic Evolution Model of Fault-Related Anticline based on the Study of the Striated Pebbles of the Related Growth-Strata: A Case Study of the Es Satah Anticline in Southern Tunisian Atlas,Tunisia     

Khalfi  C.  Ahmadi  R.  Trigui  H.  Ouali  J.  Mercier  E. 《Geotectonics》2019,53(3):419-432

Geotectonics - Through several stations on the forelimb of the Es Satah anticline belonging to Gafsa basin part of the southern Tunisian Atlas, an analysis of the striations encountered on the...  相似文献   

Near-future changes in storm surges along the Atlantic Iberian coast     

Fortunato  André B.  Meredith  Edmund P.  Rodrigues  Marta  Freire  Paula  Feldmann  Hendrik 《Natural Hazards》2019,98(3):1003-1020

Natural Hazards - Decadal predictions bridge the gap between the short-term weather/seasonal forecasts and the long-term climate projections. They target the reproduction of large-scale weather...  相似文献   

10,000 years of climate control over carbon accumulation in an Iberian bog(southwestern Europe)     

Xabier Pontevedra-Pombal  Daniel Castro  Martín Souto  Isabel Fraga  William H.Blake  Maarten Blaauw  José A.López-Sáez  Sebastián Pérez-Díaz  Marcos Valcárcel  Eduardo García-Rodeja 《地学前缘(英文版)》2019,10(4):1521-1533

The northwest region of the Iberian Peninsula is home to a unique ecosystem of bogs,which are particularly sensitive to projected climate cha nge.In this context,the rate of carbon(C)accumulation in Chao de Veiga Mol.an intact raised bog,was analysed.Changes in the accumulation rate over the past10 millennia were determined in a peat core of 847 cm in depth,with a high mean rate of peat growth(11 yr cm^-1,0.09 cm yr^-1).An age-depth model was generated from 22 14C dates and fallout radionuclides.Chronological,stratigraphical and physico-chemical data confirmed the existence of a single cycle of peat formation throughout the Holocene and the formation of ombrotrophic peat 9500 years ago.The total mean C content was 50.2%,and over 10 millennia 583 kg C m^-2 accumulated at a mean rate of 35.3 g C m^-2 yr^-1,with a long-term(apparent)rate of carbon accumulation in the catotelm of59.9 g C m^-2 yr^-1.These values are much higher than reported for other Iberian peatlands and are amongst the highest documented for peatlands in the northern hemisphere.The dynamics of C accumulation and other measured parameters reveals important variations throughout the Holocene.They could be associated with the main climatic events described in the northern hemisphere and are highly consistent with models established for northern latitudes.The Chao de Veiga Mol raised bog is unique and of great potential value for carrying out high resolution palaeoenvironmental studies,especially in relation to regional and Iocal modulations in southern Europe.  相似文献   

Editorial     

René Schwarzenbach 《Aquatic Sciences - Research Across Boundaries》1990,52(1):2-2

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Energy balance in current sheets: From Petschek to gravity driven reconnection?     

C. Mercier  J. Heyvaerts 《Solar physics》1980,68(1):151-176

It has been shown earlier that energy balance processes play a very important role in the determination of the reconnection regime in the central diffusive region of a steady Petschek flow (usually considered elsewhere as isothermal and incompressible): as a consequence of the plasma thermal properties, abrupt transitions in the reconnection regime may occur for special external conditions. The regime becomes then a dynamical one, and it was suggested that onset of plasma microturbulence may result and act as a primary triggering mechanism in solar flares.In this paper we will reexamine the problem of onset of such dynamical transition and conclude that plasma microturbulence does not appear in a straightforward way. However it is possible that the canonical Petschek regime may evolute into a new one in which the dissipative sheet is no longer infinitesimal with respect to the dimensions of the structure, and in which gravity plays an important role. Flare triggering, if related to the reconnection regime, must then proceed by more complex processes, possibly related to tearing mode dynamics, or to more global properties of the magnetic structure of the active region.  相似文献   

Study of the Ammonia ice cloud layer in the equatorial region of Jupiter from the infrared interferometric experiment on voyager     

André Marten  Daniel Rouan  Jean Paul Baluteau  Daniel Gautier  Barney J. Conrath  Rudolf A. Hanel  Virgil Kunde  Robert Samuelson  Alain Chedin  Noëlle Scott 《Icarus》1981,46(2):233-248

Spectra from the Voyager 1 infrared interferometer spectrometer (IRIS) obtained near the time of closest approach to Jupiter were analyzed for the purpose of inferring ammonia cloud properties associated with the Equatorial Region. Comparisons of observed spectra with synthetic spectra computed from a radiative transfer formulation, that includes multiple scattering, yielded the following conclusions: (1) very few NH₃ ice particles with radii less than 3 μm contribute to the cloud opacity; (2) the major source of cloud opacity arises from particles with radii in excess of 30 μm; (3) column particle densities are between 1 and 2 orders of magnitude smaller than those derived from thermochemical considerations alone, implying the presence of important atmospheric motion; and (4) another cloud system is confirmed to exist deeper in the Jovian troposphere.  相似文献   

Evidence of large scale diverging paths in the solar corona for type III bursts exciters     

C. Mercier 《Solar physics》1975,45(1):169-179

On July 1,1971, about ten groups of type III radiobursts were observed with the 169 MHz Nançay radioheliograph. Each group consisted of two or several bursts exhibiting short delays from east to west (～0.5 s) and separated by distance of ～ 1.5 × 10⁵ km. Explanations by simultaneous emission at the fundamental and harmonic of the local plasma frequency, or by reflexion of electromagnetic radiations at dense regions are shown to be inconsistent with the observations. We suggest that distinct exciters are simultaneously accelerated at low levels in very close regions and propagate upward along very widely diverging magnetic field lines.  相似文献   

Some statistical properties of Ellerman bombs     

J. -René Roy  H. Leparskas 《Solar physics》1973,30(2):449-457

One hundred seventy-eight Ellerman bombs were identified and studied with on- and off-band H filtergrams of two active centers, one near disk center and the other near the east limb. The photographs, taken through a 1/4 Å bandpass filter, occasionally attained resolution as fine as 0.3. The mean duration of bombs at H-2 Å was about 13 min near disk center and 11 min near the limb; these times increase slightly when we observe closer to the core of H. Eighty-six percent of the bombs in the near-limb region and 56% in the disk-center region were seen to be accompanied by ejections of dark material; the ejections were 3–30 long. The ejection length appears to be proportional to the bomb size times the bomb lifetime.  相似文献   

In memoriam     

André Deprit 《Celestial Mechanics and Dynamical Astronomy》1974,10(2):138-139

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