Wave dissipation by vegetation with layer schematization in SWAN   总被引：1，自引：0，他引：1  

Tomohiro Suzuki  Marcel ZijlemaBastiaan Burger  Martijn C. MeijerSiddharth Narayan 《Coastal Engineering》2012,59(1):64-71

The energy of waves propagating through vegetation is dissipated due to the work done by the waves on the vegetation. Dalrymple et al. (1984) estimated wave dissipation by integrating the force on a cylinder over its vertical extent. This was extended by Mendez and Losada (2004) to include varying depths and the effects of wave damping due to vegetation and wave breaking for narrow-banded random waves. This paper describes the wave dissipation over a vegetation field by the implementation of the Mendez and Losada formulation in a full spectrum model SWAN, with an extension to include a vertical layer schematization for the vegetation. The present model is validated with the original equation and results from Mendez and Losada (2004). The sensitivity of the model to the shape of the frequency spectrum, directional spreading and layer schematization are investigated. The model is then applied to field measurements by using a vegetation factor. This model has the ability to calculate two-dimensional wave dissipation over a vegetation field including some important aspects such as breaking and diffraction as used in SWAN model.  相似文献   

An integrated suspended sediment transport monitoring and analysis concept   总被引：1，自引：1，他引：0  

Marlene HAIMANN  Marcel LIEDERMANN  Petra LALK  Helmut HABERSACK 《国际泥沙研究》2014,29(2):135-148

A new integrated suspended sediment monitoring strategy applying direct and indirect technologies is presented.Optical sensors continuously record the turbidity at one point in the channel cross section close to the river bank and are calibrated by water samples taken close to the sensor.Additionally measurements are performed to establish the distribution of suspended sediment in a cross section（bottle samples combined with acoustic devices）.Using correction factors（probe and cross-sectional factor） these monitoring methods are combined and it is,thus,possible to fully document the temporal and spatial variability of the suspended sediment transport and to estimate the suspended sediment load for certain time periods.This monitoring strategy was implemented at various measurement sites in Austria as well as at the Hainburg Road Bridge site on the Danube River.It has already been successfully applied for three years at this measurement site and suspended sediment loads during high discharges up to a 15 year flood event have been monitored.To evaluate the new monitoring methods the results were compared with load estimation methods found in the literature including averaging and ratio estimators as well as rating curves.The results prove that with the new methodology,the temporal variability of the suspended sediment transport can be detected more accurately compared with the other methods.They also demonstrate that the additional consideration of the spatial distribution of the suspended sediment concentration in the cross section is crucial as the mean concentration in the cross section can significantly exceed the concentration near the banks,especially at large rivers like the Danube River.  相似文献   

Toward Bayesian uncertainty quantification for forestry models used in the United Kingdom Greenhouse Gas Inventory for land use, land use change, and forestry     

Marcel van Oijen  Amanda Thomson 《Climatic change》2010,103(1-2):55-67

The Greenhouse Gas Inventory for the United Kingdom currently uses a simple carbon-flow model, CFLOW, to calculate the emissions and removals associated with forest planting since 1920. Here, we aim to determine whether a more complex process-based model, the BASic FORest (BASFOR) simulator, could be used instead of CFLOW. The use of a more complex approach allows spatial heterogeneity in soils and weather to be accounted for, but places extra demands on uncertainty quantification. We show how Bayesian methods can be used to address this problem.  相似文献   

Estimating coastal recession due to sea level rise: beyond the Bruun rule   总被引：2，自引：0，他引：2  

Roshanka Ranasinghe  David Callaghan  Marcel J. F. Stive 《Climatic change》2012,110(3-4):561-574

Accelerated sea level rise (SLR) in the twenty-first century will result in unprecedented coastal recession, threatening billions of dollars worth of coastal developments and infrastructure. Therefore, we cannot continue to depend on the highly uncertain coastal recession estimates obtained via the simple, deterministic method (Bruun rule) that has been widely used over the last 50?years. Furthermore, the emergence of risk management style coastal planning frameworks is now requiring probabilistic (rather than deterministic, single value) estimates of coastal recession. This paper describes the development and application of a process based model (PCR model) which provides probabilistic estimates of SLR driven coastal recession. The PCR model is proposed as a more appropriate and defensible method for determining coastal recession due to SLR for planning purposes in the twenty-first century and beyond.  相似文献   

Pyrite oxidation during sample storage determines phosphorus fractionation in carbonate-poor anoxic sediments   总被引：4，自引：0，他引：4  

Peter Kraal  Caroline P. Slomp  Marcel M.M. Kuypers 《Geochimica et cosmochimica acta》2009,73(11):3277-3290

We investigated the phosphorus (P) and iron (Fe) fractionation in four cores with anoxic sediments, deposited during the mid-Cretaceous oceanic anoxic event 2 (∼94 Ma) and the Paleocene-Eocene thermal maximum (∼55 Ma), that were exposed to oxygen after core recovery. Surprisingly, P associated with iron oxyhydroxides (Fe-bound P) was a major P phase in these laminated sediments deposited under euxinic conditions. A significant fraction of total Fe was present as (poorly) crystalline ferric Fe. This fraction increased with increasing storage time of the investigated cores. In carbonate-poor samples, Fe-bound P accounted for up to 99% of total P and its abundance correlated with pyrite contents. In samples with higher CaCO₃ contents (>5 wt% in the investigated samples), P was mostly present in authigenic Ca-P minerals, irrespective of pyrite contents. We conclude that the P fractionation in anoxic, carbonate-poor, sediments is strongly affected by pyrite oxidation that occurs when these sediments are exposed to oxygen. Pyrite oxidation produces sulfuric acid and iron oxyhydroxides. The abundance of poorly crystalline Fe oxyhydroxides provides further evidence that these were indeed formed through recent (post-recovery) oxidation rather than in situ tens of millions of years ago. The acid dissolves apatite and the released phosphate is subsequently bound in the freshly formed iron oxyhydroxides. Pyrite oxidation thus leads to a conversion of authigenic Ca-P to Fe-bound P. In more calcareous samples, CaCO₃ can act as an effective buffer against acidic dissolution of Ca-P minerals. The results indicate that shielding of sediments from atmospheric oxygen is vital to preserve the in situ P fractionation and to enable a valid reconstruction of marine phosphorus cycling based on sediment records.  相似文献   

Topical Collection: Groundwater-based agriculture in the Mediterranean     

Marcel Kuper  Christian Leduc  Sylvain Massuel  Sami Bouarfa 《Hydrogeology Journal》2017,25(6):1525-1528

This essay introduces a collection of articles that explore the future of groundwater-based agriculture in the Mediterranean from an interdisciplinary perspective, in a context of declining water tables due to intensive groundwater use. The imminent crisis that many groundwater economies face due to very rapid and intense global change may have severe irreversible social, economic and environmental consequences, but could also be the opportunity to make a clear break with current agricultural development models and move towards more sustainable agricultural practices. The Mediterranean region is, therefore, an interesting case for the future of intensive groundwater use, as innovative ideas and practices may emerge and inspire similar groundwater-based agricultural systems around the world.  相似文献   

Book reviews     

Verna D. Freeman  R. Sinclair  Anthony M. Fuller  P. Bruyelle  Marcel Bazin  Wolf Tietze  Guido G. Weigend  K. Cehak  Werner Gallusser 《GeoJournal》1980,4(6):576-580

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Excitation of high-frequency Alfvén waves by plasma outflows from coronal reconnection events     

Voitenko  Yuriy  Goossens  Marcel 《Solar physics》2002,206(2):285-313

We study a kinetic excitation mechanism for high-frequency dispersive Alfvén waves in the solar corona by magnetic reconnection events. The ion-cyclotron and Cerenkov kinetic effects are important for these waves which we call the ion-cyclotron kinetic Alfvén waves (IC KAWs). The plasma outflowing from the reconnection site sets up a neutralized proton beam in the surrounding plasma, providing free energy for the excitation of waves. The dependence of the phase velocity of the IC KAW on the parallel wavenumber is different from that on the perpendicular wavenumber. The phase velocity is an increasing function of the perpendicular wavenumber and overtakes the Alfvén velocity for sufficiently large values of k . However, the phase velocity is a decreasing function of k , and sufficiently large values of k result in a phase velocity below the Alfvén velocity. As a result, the IC KAWs can undergo the Cerenkov resonance with both super- and sub-Alfvénic particles, and for the waves to be excited the outflow velocity does not need to be super-Alfvénic, as for KAWs, but the beam/Alfvén velocity ratio can span a wide range of values. High growth rates of the order of 10⁴ s^–1 are found for the values of the plasma parameters typical for the low solar corona. The waves excited by (sub-)Alfvénic beams are damped mainly due to kinetic wave-particle interactions with ions at the cyclotron resonance (ion-cyclotron damping), and with ions and electrons at the Cerenkov resonance (Landau damping). Therefore, IC KAWs can heat the plasma species of the corona in both the parallel and perpendicular direction, giving rise to an anisotropic heating of the ions. The observational consequences of the processes under study are discussed.  相似文献   

Numerical Homogenization of the Rigidity Tensor in Hooke''s Law Using the Node-Based Finite Element Method     

Wouter Zijl  Max A. N. Hendriks  C. Marcel P. ''t Hart 《Mathematical Geology》2002,34(3):291-322

Combining a geological model with a geomechanical model, it generally turns out that the geomechanical model is built from units that are at least a 100 times larger in volume than the units of the geological model. To counter this mismatch in scales, the geological data model's heterogeneous fine-scale Young's moduli and Poisson's ratios have to be upscaled to one equivalent homogeneous coarse-scale rigidity. This coarse-scale rigidity relates the volume-averaged displacement, strain, stress, and energy to each other, in such a way that the equilibrium equation, Hooke's law, and the energy equation preserve their fine-scale form on the coarse scale. Under the simplifying assumption of spatial periodicity of the heterogeneous fine-scale rigidity, homogenization theory can be applied. However, even then the spatial variability is generally so complex that exact solutions cannot be found. Therefore, numerical approximation methods have to be applied. Here the node-based finite element method for the displacement as primary variable has been used. Three numerical examples showing the upper bound character of this finite element method are presented.  相似文献   

Variabilité spatiale du signal palynologique dans le bassin de Paris à la limite Dogger–Malm     

Vincent Huault  Marcel Élie  Régine Ruck-Mosser 《Comptes Rendus Geoscience》2003,335(4):401-409

The drilling of new cores performed for ANDRA in eastern France allowed us to compare palynological data between central and eastern parts of the Paris Basin. Such a comparison, which was also motivated by the existence of a set of geochemical data in contradiction with the first palynological results, showed a spatial differentiation in palynological record from the Oxfordian. Such a palynological signal could result from overlapping of both local and global signals, the latter being in connection with the contemporaneous opening of proto-Atlantic Ocean. It could also be of major palaeogeographic and palaeoclimatic interest. To cite this article: V. Huault et al., C. R. Geoscience 335 (2003).  相似文献