Assessing the impact of the hydraulic properties of a crusted soil on overland flow modelling at the field scale     

Nane Chahinian  Marc Voltz  Roger Moussa  Gwenn Trotoux 《水文研究》2006,20(8):1701-1722

Soil surface crusts are widely reported to favour Hortonian runoff, but are not explicitly represented in most rainfall‐runoff models. The aim of this paper is to assess the impact of soil surface crusts on infiltration and runoff modelling at two spatial scales, i.e. the local scale and the plot scale. At the local scale, two separate single ring infiltration experiments are undertaken. The first is performed on the undisturbed soil, whereas the second is done after removal of the soil surface crust. The HYDRUS 2D two‐dimensional vertical infiltration model is then used in an inverse modelling approach, first to estimate the soil hydraulic properties of the crust and the subsoil, and then the effective hydraulic properties of the soil represented as a single uniform layer. The results show that the crust hydraulic conductivity is 10 times lower than that of the subsoil, thus illustrating the limiting role the crust has on infiltration. Moving up to the plot scale, a rainfall‐runoff model coupling the Richards equation to a transfer function is used to simulate Hortonian overland flow hydrographs. The previously calculated hydraulic properties are used, and a comparison is undertaken between a single‐layer and a double‐layer representation of the crusted soil. The results of the rainfall‐runoff model show that the soil hydraulic properties calculated at the local scale give acceptable results when used to model runoff at the plot scale directly, without any numerical calibration. Also, at the plot scale, no clear improvement of the results can be seen when using a double‐layer representation of the soil in comparison with a single homogeneous layer. This is due to the hydrological characteristics of Hortonian runoff, which is triggered by a rainfall intensity exceeding the saturated hydraulic conductivity of the soil surface. Consequently, the rainfall‐runoff model is more sensitive to rainfall than to the subsoil's hydrodynamic properties. Therefore, the use of a double‐layer soil model to represent runoff on a crusted soil does not seem necessary, as the increase of precision in the soil discretization is not justified by a better performance of the model. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Supermassive black hole merger rates: uncertainties from halo merger theory     

Adrienne L. Erickcek  Marc Kamionkowski  Andrew J. Benson 《Monthly notices of the Royal Astronomical Society》2006,371(4):1992-2000

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A review of inverse methods in seismic site characterization     

Gosselin  Jeremy M.  Dosso  Stan E.  Askan  Aysegul  Wathelet  Marc  Savvaidis  Alexandros  Cassidy  John F. 《Journal of Seismology》2022,26(4):781-821

Journal of Seismology - Seismic site characterization attempts to quantify seismic wave behavior at a specific location based on near-surface geophysical properties, for the purpose of mitigating...  相似文献   

Mineralogy,petrology, chronology,and exposure history of the Chelyabinsk meteorite and parent body          下载免费PDF全文

K. Righter  P. Abell  D. Agresti  E. L. Berger  A. S. Burton  J. S. Delaney  M. D. Fries  E. K. Gibson  M. K. Haba  R. Harrington  G. F. Herzog  L. P. Keller  D. Locke  F. N. Lindsay  T. J. McCoy  R. V. Morris  K. Nagao  K. Nakamura‐Messenger  P. B. Niles  L. E. Nyquist  J. Park  Z. X. Peng  C.‐Y. Shih  J. I. Simon  C. C. Swisher III  M. J. Tappa  B. D. Turrin  R. A. Zeigler 《Meteoritics & planetary science》2015,50(10):1790-1819

Three masses of the Chelyabinsk meteorite have been studied with a wide range of analytical techniques to understand the mineralogical variation and thermal history of the Chelyabinsk parent body. The samples exhibit little to no postentry oxidation via Mössbauer and Raman spectroscopy indicating their fresh character, but despite the rapid collection and care of handling some low levels of terrestrial contamination did nonetheless result. Detailed studies show three distinct lithologies, indicative of a genomict breccia. A light‐colored lithology is LL5 material that has experienced thermal metamorphism and subsequent shock at levels near S4. The second lithology is a shock‐darkened LL5 material in which the darkening is caused by melt and metal‐troilite veins along grain boundaries. The third lithology is an impact melt breccia that formed at high temperatures (~1600 °C), and it experienced rapid cooling and degassing of S₂ gas. Portions of light and dark lithologies from Chel‐101, and the impact melt breccias (Chel‐102 and Chel‐103) were prepared and analyzed for Rb‐Sr, Sm‐Nd, and Ar‐Ar dating. When combined with results from other studies and chronometers, at least eight impact events (e.g., ~4.53 Ga, ~4.45 Ga, ~3.73 Ga, ~2.81 Ga, ~1.46 Ga, ~852 Ma, ~312 Ma, and ~27 Ma) are clearly identified for Chelyabinsk, indicating a complex history of impacts and heating events. Finally, noble gases yield young cosmic ray exposure ages, near 1 Ma. These young ages, together with the absence of measurable cosmogenic derived Sm and Cr, indicate that Chelyabinsk may have been derived from a recent breakup event on an NEO of LL chondrite composition.  相似文献   

Similarity Scaling Over a Steep Alpine Slope   总被引：5，自引：5，他引：0  

Daniel F. Nadeau  Eric R. Pardyjak  Chad W. Higgins  Marc B. Parlange 《Boundary-Layer Meteorology》2013,147(3):401-419

In this study, we investigate the validity of similarity scaling over a steep mountain slope (30–41 $^\circ $ ). The results are based on eddy-covariance data collected during the Slope Experiment near La Fouly (SELF-2010); a field campaign conducted in a narrow valley of the Swiss Alps during summer 2010. The turbulent fluxes of heat and momentum are found to vary significantly with height in the first few metres above the inclined surface. These variations exceed by an order of magnitude the well-accepted maximum 10 % required for the applicability of Monin–Obukhov similarity theory in the surface layer. This could be due to a surface layer that is too thin to be detected or to the presence of advective fluxes. It is shown that local scaling can be a useful tool in these cases when surface-layer theory breaks down. Under convective conditions and after removing the effects of self-correlation, the normalized standard deviations of slope-normal wind velocity, temperature and humidity scale relatively well with $z/\varLambda $ , where $z$ is the measurement height and $\varLambda (z)$ the local Obukhov length. However, the horizontal velocity fluctuations are not correlated with $z/\varLambda $ under all stability regimes. The non-dimensional gradients of wind velocity and temperature are also investigated. For those, the local scaling appears inappropriate, particularly at night when shallow drainage flows prevail and lead to negative wind-speed gradients close to the surface.  相似文献   

Publisher’s Erratum to: The Herschel PACS photometer calibration     

Markus Nielbock  Thomas Müller  Ulrich Klaas  Bruno Altieri  Zoltán Balog  Nicolas Billot  Hendrik Linz  Koryo Okumura  Miguel Sánchez-Portal  Marc Sauvage 《Experimental Astronomy》2014,37(2):127-127

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Detection and rapid recovery of the Sutter's Mill meteorite fall as a model for future recoveries worldwide     

Marc Fries  Lucille Le Corre  Mike Hankey  Jeff Fries  Robert Matson  Jake Schaefer  Vishnu Reddy 《Meteoritics & planetary science》2014,49(11):1989-1996

The Sutter's Mill C‐type meteorite fall occurred on 22 April 2012 in and around the town of Coloma, California. The exact location of the meteorite fall was determined within hours of the event using a combination of eyewitness reports, weather radar imagery, and seismometry data. Recovery of the first meteorites occurred within 2 days and continued for months afterward. The recovery effort included local citizens, scientists, and meteorite hunters, and featured coordination efforts by local scientific institutions. Scientific analysis of the collected meteorites revealed characteristics that were available for study only because the rapid collection of samples had minimized terrestrial contamination/alteration. This combination of factors—rapid and accurate location of the event, participation in the meteorite search by the public, and coordinated scientific investigation of recovered samples—is a model that was widely beneficial and should be emulated in future meteorite falls. The tools necessary to recreate the Sutter's Mill recovery are available, but are currently underutilized in much of the world. Weather radar networks, scientific institutions with interest in meteoritics, and the interested public are available globally. Therefore, it is possible to repeat the Sutter's Mill recovery model for future meteorite falls around the world, each for relatively little cost with a dedicated researcher. Doing so will significantly increase the number of fresh meteorite falls available for study, provide meteorite material that can serve as the nuclei of new meteorite collections, and will improve the public visibility of meteoritics research.  相似文献   

3. Solar System Formation and Early Evolution: the First 100 Million Years     

Thierry Montmerle  Jean-Charles Augereau  Marc Chaussidon  Mathieu Gounelle  Bernard Marty  Alessandro Morbidelli 《Earth, Moon, and Planets》2006,98(1-4):39-95

The solar system, as we know it today, is about 4.5 billion years old. It is widely believed that it was essentially completed 100 million years after the formation of the Sun, which itself took less than 1 million years, although the exact chronology remains highly uncertain. For instance: which, of the giant planets or the terrestrial planets, formed first, and how? How did they acquire their mass? What was the early evolution of the “primitive solar nebula” (solar nebula for short)? What is its relation with the circumstellar disks that are ubiquitous around young low-mass stars today? Is it possible to define a “time zero” (t ₀), the epoch of the formation of the solar system? Is the solar system exceptional or common? This astronomical chapter focuses on the early stages, which determine in large part the subsequent evolution of the proto-solar system. This evolution is logarithmic, being very fast initially, then gradually slowing down. The chapter is thus divided in three parts: (1) The first million years: the stellar era. The dominant phase is the formation of the Sun in a stellar cluster, via accretion of material from a circumstellar disk, itself fed by a progressively vanishing circumstellar envelope. (2) The first 10 million years: the disk era. The dominant phase is the evolution and progressive disappearance of circumstellar disks around evolved young stars; planets will start to form at this stage. Important constraints on the solar nebula and on planet formation are drawn from the most primitive objects in the solar system, i.e., meteorites. (3) The first 100 million years: the “telluric” era. This phase is dominated by terrestrial (rocky) planet formation and differentiation, and the appearance of oceans and atmospheres.  相似文献   

Molluscan assemblages of seagrass-covered and bare intertidal flats on the Banc d'Arguin, Mauritania, in relation to characteristics of sediment and organic matter     

Pieter J.C. Honkoop  Eilke M. Berghuis  Sander Holthuijsen  Marc S.S. Lavaleye  Theunis Piersma   《Journal of Sea Research》2008,60(4):255-263

The Banc d'Arguin, a non-estuarine area of shallows and intertidal flats off the tropical Saharan coast of Mauritania, is characterised by extensive intertidal and subtidal seagrass beds. We examined the characteristics of intertidal seagrass (Zostera noltii) meadows and bare areas in terms of the presence and abundance of molluscs (gastropods and bivalves). To explain observed differences between molluscan assemblages in seagrass and bare patches, some aspects of the feeding habitat (top-5 mm of the sediment) and of food (organic materials) of molluscs were examined. The novelty of this study is that phytopigments were measured and identified to assess source and level of decay (freshness) of organic material in the sediment and to study their importance as an explanatory variable for the distribution of molluscs. Over an area of 36 km² of intertidal flats, at 12 sites, paired comparisons were made between seagrass-covered and nearby bare patches. Within seagrass meadows, dry mass of living seagrass was large and amounted to 180 ±10 g AFDM m^− 2 (range 75–240). Containing twice the amount of silt per unit dry sediment mass, seagrass sediments were muddier than bare areas; the relative amount of organic material was also larger. The total number of species of bivalves and gastropods amounted to 27, 14 of which were found only in seagrass areas, 4 only in bare and 9 in both types of habitat. Among the three numerically most abundant species, the bivalves Anadara senilis, Dosinia hepatica and Loripes lacteus, the first was numerically most abundant in bare and the other two in seagrass-covered areas. Bare intertidal areas had greater mean total biomass of molluscs (80.5 g AFDM m^− 2) than seagrass meadows (30.0 g AFDM m^− 2). In both habitats, the bulk of the biomass was made up by A. senilis. Excluding this species, bare mudflats contained on average only 3.1 g AFDM m^− 2 and seagrass meadows 6.9 g AFDM m^− 2. As compared to previous surveys in 1980–1986, the biomass of A. senilis had increased almost 10-fold and D. hepatica, previously found in very small numbers, had become the most numerous species. However, the total biomass excluding that of A. senilis was similar. Concentrations of phytopigments were similar to those observed at temperate mudflats, indicating that the Banc d'Arguin might not be as oligotrophic as previously thought. Per unit of dry sediment mass, smaller amounts of phytopigments were found in bare than in seagrass areas. Per unit of dry organic material, bare sediments contained most (fresh) phytopigments. This suggests that in seagrass-covered meadows the organic material is more degraded than in bare sediments. Overall, the composition of phytopigments, quite surprisingly, indicated a benthic-diatom-dominated trophic system. Multivariate statistics revealed that patterns of zoobenthic assemblages were correlated with patterns of a combination of four environmental parameters: grain size of the sediment, amount of fresh phytopigments and amounts of leaves and roots of seagrass.  相似文献   

Trophic modeling of the Northern Humboldt Current Ecosystem, Part II: Elucidating ecosystem dynamics from 1995 to 2004 with a focus on the impact of ENSO   总被引：1，自引：1，他引：0  

Marc H. Taylor  Jorge Tam  Vernica Blaskovic  Pepe Espinoza  R. Michael Balln  Claudia Wosnitza-Mendo  Juan Argüelles  Erich Díaz  Sara Purca  Noemi Ochoa  Patricia Ayn  Elisa Goya  Dimitri Gutirrez  Luis Quipuzcoa  Matthias Wolff 《Progress in Oceanography》2008,79(2-4):366

The Northern Humboldt Current Ecosystem is one of the most productive in the world in terms of fish production. Its location near to the equator permits strong upwelling under relatively low winds, thus creating optimal conditions for the development of plankton communities. These communities ultimately support abundant populations of grazing fish such as the Peruvian anchoveta, Engraulis ringens. The ecosystem is also subject to strong inter-annual environmental variability associated with the El Niño Southern Oscillation (ENSO), which has major effects on nutrient structure, primary production, and higher trophic levels. Here our objective is to model the contributions of several external drivers (i.e. reconstructed phytoplankton changes, fish immigration, and fishing rate) and internal control mechanisms (i.e. predator-prey) to ecosystem dynamics over an ENSO cycle. Steady-state models and time-series data from the Instituto del Mar del Perú (IMARPE) from 1995 to 2004 provide the base data for simulations conducted with the program Ecopath with Ecosim. In simulations all three external drivers contribute to ecosystem dynamics. Changes in phytoplankton quantity and composition (i.e. contribution of diatoms and dino- and silicoflagellates), as affected by upwelling intensity, were important in dynamics of the El Niño of 1997–98 and the subsequent 3 years. The expansion and immigration of mesopelagic fish populations during El Niño was important for dynamics in following years. Fishing rate changes were the most important of the three external drivers tested, helping to explain observed dynamics throughout the modeled period, and particularly during the post-El Niño period. Internal control settings show a mix of predator–prey control settings; however a “wasp-waist” control of the ecosystem by small pelagic fish is not supported.  相似文献