Coastal changes at the Sulina mouth of the Danube River as a result of human activities   总被引：2，自引：0，他引：2  

Stanica A  Dan S  Ungureanu VG 《Marine pollution bulletin》2007,55(10-12):555-563

Sulina, the middle distributary of the Danube Delta, has been significantly changed by human activities over the past 150 yr. These include engineering works in the second half of the 19th century, when the channel was transformed for navigation and the construction of jetties which nowadays extend 8 km seawards. These interventions have strongly affected the natural processes of the Black Sea coast near the Sulina mouth. To the south of the Sulina mouth, the natural mild erosion has been reversed in the area close to the jetties where accretion is occurring, while southwards the greatest erosion rate along the entire Romanian coast, of more than 20 m/yr, has been recorded. Sediment accumulation in the northern part of the mouth is also huge and has brought to the creation and swift elongation of a sediment spit in several decades. Thus, the bay located here suffers from a rapid transformation into a lagoon.  相似文献   

Possible role of warm SST bias in the simulation of boreal summer monsoon in SINTEX-F2 coupled model     

Susmitha Joseph  A. K. Sahai  B. N. Goswami  Pascal Terray  Sebastian Masson  J.-J. Luo 《Climate Dynamics》2012,38(7-8):1561-1576

Reasonably realistic climatology of atmospheric and oceanic parameters over the Asian monsoon region is a pre-requisite for models used for monsoon studies. The biases in representing these features lead to problems in representing the strength and variability of Indian summer monsoon (ISM). This study attempts to unravel the ability of a state-of-the-art coupled model, SINTEX-F2, in simulating these characteristics of ISM. The coupled model reproduces the precipitation and circulation climatology reasonably well. However, the mean ISM is weaker than observed, as evident from various monsoon indices. A wavenumber–frequency spectrum analysis reveals that the model intraseasonal oscillations are also weaker-than-observed. One possible reason for the weaker-than-observed ISM arises from the warm bias, over the tropical oceans, especially over the equatorial western Indian Ocean, inherent in the model. This warm bias is not only confined to the surface layers, but also extends through most of the troposphere. As a result of this warm bias, the coupled model has too weak meridional tropospheric temperature gradient to drive a realistic monsoon circulation. This in turn leads to a weakening of the moisture gradient as well as the vertical shear of easterlies required for sustained northward propagation of rain band, resulting in weak monsoon circulation. It is also noted that the recently documented interaction between the interannual and intraseasonal variabilities of ISM through very long breaks (VLBs) is poor in the model. This seems to be related to the inability of the model in simulating the eastward propagating Madden–Julian oscillation during VLBs.  相似文献   

A multicriteria approach for flood risk mapping exemplified at the Mulde river,Germany   总被引：6，自引：4，他引：2  

Volker Meyer  Sebastian Scheuer  Dagmar Haase 《Natural Hazards》2009,48(1):17-39

In this paper we develop a GIS-based multicriteria flood risk assessment and mapping approach. This approach includes flood risks which are not measured in monetary terms; it shows the spatial distribution of multiple risks, and it is able to deal with uncertainties in criteria values and to show their influence on the overall flood risk assessment. Additionally, the approach can be used to show the spatial allocation of the flood effects if risk reduction measures are implemented. The approach is applied to a pilot study for the River Mulde in Saxony, Germany, heavily affected by the hazardous flood in 2002. Therefore, a GIS database of economic, social and environmental risk criteria was created. Two different multicriteria decision rules, a disjunctive and an additive weighting approach, are utilised for an overall flood risk assessment in the area. For implementation, a software tool (FloodCalc) was developed supporting both, the risk calculation of the single criteria as well as the multicriteria analysis.

Volker MeyerEmail:

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Micromechanics of vortices in granular media: connection to shear bands and implications for continuum modelling of failure in geomaterials     

Antoinette Tordesillas  Sebastian Pucilowski  David M. Walker  John F. Peters  Laura E. Walizer 《国际地质力学数值与分析法杂志》2014,38(12):1247-1275

Recent analysis of data from triaxial tests on sand and discrete element simulations indicate the final pattern of failure is encoded in grain motions during the nascent stages of loading. We study vortices that are evident from grain displacements at the start of loading and bear a direct mathematical connection to boundary conditions, uniform continuum strain and shear bands. Motions of three grains in mutual contact, that is, 3‐cycles, manifest vortices. In the initial stages of loading, 3‐cycles initiate a rotation around a region Ω^* where the shear band ultimately develops. This bias sets a course in 3‐cycle evolution, determining where they will more likely collapse. A multiscale spatial analysis of 3‐cycle temporal evolution provides quantitative evidence that the most stable, persistent 3‐cycles degrade preferentially in Ω^*, until essentially depleted when the shear band is fully formed. The transition towards a clustered distribution of persistent 3‐cycles occurs early in the loading history—and coincides with the persistent localisation of vortices in Ω^*. In 3D samples, no evidence of spatial clustering in persistent 3‐cycle deaths is found in samples undergoing diffuse failure, while early clustering manifests in a sample that ultimately failed by strain localisation. This study not only delivered insights into the possible structural origins of vortices in dense granular systems but also a tool for the early detection of the mode of failure—localised versus diffuse—a sample will ultimately undergo. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Validation of impact penetrometer data by cone penetration testing and shallow seismic data within the regional geology of the Southern North Sea     

Sebastian Stephan  Norbert Kaul  Heinrich Villinger 《Geo-Marine Letters》2015,35(3):203-219

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Structural and magnetic phase transitions in the synthetic clinopyroxene LiCrGe2O6: a neutron diffraction study between 0.5 and 1473 K     

Günther J. Redhammer  Anatoliy Senyshyn  Gerold Tippelt  Sebastian Prinz  Georg Roth 《Physics and Chemistry of Minerals》2015,42(6):491-507

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Model insight into glacial–interglacial paleodust records     

Natalie Mahowald  Samuel Albani  Sebastian Engelstaedter  Gisela Winckler  Michelle Goman 《Quaternary Science Reviews》2011,30(7-8):832-854

We present a new method of analyzing model results to help identify the sensitivity of the location of different paleodust records to estimate local to regional scale variability of dust and climate variables. We use model simulations of global dust distribution from the last glacial maximum, preindustrial, current, and predicted future. The dust model has been previously shown to match available observational data for the current and last glacial maximum climate. Here, the model is compared to available source provenance data and is shown to agree with these limited observations. Using correlations and slopes across different time periods, the modeled relationships between deposition at specific observational sites and regional deposition and dustiness are shown. In addition, we evaluate the modeled relative slope of these cores to determine the location of paleodust sites that are especially easy to interpret as regional indicators of dustiness. Model predictions suggest that deposition in Antarctic ice cores is usually better than dust concentration to capture regional deposition and dustiness variability over glacial–interglacial time periods, in agreement with ice core interpretations. For Greenland, the model predicts a possible shift from dominantly wet deposition under modern conditions to dominantly dry deposition during glacial climate conditions indicating that deposition may be better suited to capture dustiness variability under LGM conditions in Greenland. The model also identifies specific regions that are not well covered by observations for glacial/interglacial or anthropocene dust variability. In addition, we evaluate the modeled relative slope of the location of these cores to determine regions that would provide ideal localities for pursuing records that would provide easily interpretable paleo-proxy records of regional dustiness.  相似文献   

No evidence for widespread bird declines in protected South American forests     

Philip C Stouffer  Kristina L. Cockle  Alexandre Aleixo  Juan I. Areta  Juan Mazar Barnett  Alejandro Bodrati  Carlos Daniel Cadena  Adri��n S. Di Giacomo  Sebastian K. Herzog  Peter Hosner  Erik I. Johnson  Luciano N. Naka  C��sar S��nchez 《Climatic change》2011,108(1-2):383-386

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Warm winds from the Pacific caused extensive Arctic sea-ice melt in summer 2007   总被引：1，自引：1，他引：0  

Rune G. Graversen  Thorsten Mauritsen  Sybren Drijfhout  Michael Tjernstr?m  Sebastian M?rtensson 《Climate Dynamics》2011,36(11-12):2103-2112

During summer 2007 the Arctic sea-ice shrank to the lowest extent ever observed. The role of the atmospheric energy transport in this extreme melt event is explored using the state-of-the-art ERA-Interim reanalysis data. We find that in summer 2007 there was an anomalous atmospheric flow of warm and humid air into the region that suffered severe melt. This anomaly was larger than during any other year in the data (1989?C2008). Convergence of the atmospheric energy transport over this area led to positive anomalies of the downward longwave radiation and turbulent fluxes. In the region that experienced unusual ice melt, the net anomaly of the surface fluxes provided enough extra energy to melt roughly one meter of ice during the melting season. When the ocean successively became ice-free, the surface-albedo decreased causing additional absorption of shortwave radiation, despite the fact that the downwelling solar radiation was smaller than average. We argue that the positive anomalies of net downward longwave radiation and turbulent fluxes played a key role in initiating the 2007 extreme ice melt, whereas the shortwave-radiation changes acted as an amplifying feedback mechanism in response to the melt.  相似文献   

Exploring multicriteria flood vulnerability by integrating economic,social and ecological dimensions of flood risk and coping capacity: from a starting point view towards an end point view of vulnerability   总被引：5，自引：3，他引：2  

Sebastian Scheuer  Dagmar Haase  Volker Meyer 《Natural Hazards》2011,58(2):731-751

In this paper, we present an approach to modelling multicriteria flood vulnerability which integrates the economic, social and ecological dimension of risk and coping capacity. We start with an existing multicriteria risk mapping approach. The term risk is used here in a way that could be called a starting point view, looking at vulnerability without considering coping capacities. We extend this approach by a multicriteria modelling of coping capacities towards an end point view of vulnerability. In doing so, we explore a way to differentiate coping capacity from flood risk in each of the dimensions of vulnerability. The approach is tested in an urban case study, the city of Leipzig, Germany. Our results show that it is possible to map multicriteria risks as well as coping capacities and relate them in a simple way. However, a detailed calculation of end point vulnerability would require more detailed knowledge on the causal relationships between risk and coping capacity criteria and their relative importance.  相似文献