GRIMM: the GFZ Reference Internal Magnetic Model based on vector satellite and observatory data   总被引：3，自引：0，他引：3  

Vincent Lesur  Ingo Wardinski  Martin Rother  Mioara Mandea 《Geophysical Journal International》2008,173(2):382-394

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Coupling mechanisms in double sandbar systems. Part 2: impact on alongshore variability of inner‐bar rip channels     

Bruno Castelle  B. G. Ruessink  Philippe Bonneton  Vincent Marieu  Nicolas Bruneau  Timothy D. Price 《地球表面变化过程与地形》2010,35(7):771-781

Double sandbar systems are common morphological features along sandy, wave‐dominated, micro‐ to meso‐tidal coastlines. In the companion paper, we demonstrated how various alongshore inner‐bar rip‐channel patterns can develop through morphological coupling to an alongshore‐variable outer bar. The simulated coupling patterns are, however, scarcely observed in the field. Instead, inner‐bar rip channels more often possess remarkably smaller and more variable alongshore length scales, suggesting that coupling mechanisms do not play a substantial role in the overall double‐sandbar dynamics. Here we use a numerical model to show that the relative importance of self‐organization and morphological coupling changes in favour of the latter with an increase in waterdepth variability along the outer‐bar crest. Furthermore, we find that the typical alongshore variability in inner‐bar rip‐channel scale is indicative of a mixture of self‐organization and morphological coupling rather than self‐organization alone. Morphological coupling may thus be more important to understanding and predicting the evolution of inner‐bar rip channels than previously envisaged. Copyright © 2010 John Wiley and Sons, Ltd.  相似文献   

A statistically significant signature of multi-decadal solar activity changes in atmospheric temperatures at three European stations     

Vladimir Kossobokov  Jean-Louis Le Mouël  Vincent Courtillot 《Journal of Atmospheric and Solar》2010,72(7-8):595-606

We study the effect of solar variability on temperatures recorded in three European stations with the longest gapless series available (Prague, Bologna and Uccle). Following a pattern recognition approach, we partition daily temperature “indices” (minimum, maximum and range) in two separate classes with respect to the level of solar activity (high H vs low L 11 year cycles). Using the two-sample Kolmogorov–Smirnov statistics, multiple shuffles of data, and other partitions, we demonstrate that the separation between the probability distribution functions of H and L temperatures is statistically significant and robust. We find that average annual variations for the H and L classes display common and site-specific patterns. For practically all series considered, differences between graphs of annual change for the two classes H and L are large (～1 °C). Solar activity accounts, at least in part, for the multi-decadal variations in temperature observed at these European sites in the past two centuries.  相似文献   

Multi-scale modelling of coastal, shelf and global ocean dynamics     

Eric Deleersnijder  Vincent Legat  Pierre F. J. Lermusiaux 《Ocean Dynamics》2010,60(6):1357-1359

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A discontinuous finite element baroclinic marine model on unstructured prismatic meshes     

Richard Comblen  Sébastien Blaise  Vincent Legat  Jean-François Remacle  Eric Deleersnijder  Jonathan Lambrechts 《Ocean Dynamics》2010,60(6):1395-1414

We describe the time discretization of a three-dimensional baroclinic finite element model for the hydrostatic Boussinesq equations based upon a discontinuous Galerkin finite element method. On one hand, the time marching algorithm is based on an efficient mode splitting. To ensure compatibility between the barotropic and baroclinic modes in the splitting algorithm, we introduce Lagrange multipliers in the discrete formulation. On the other hand, the use of implicit–explicit Runge–Kutta methods enables us to treat stiff linear operators implicitly, while the rest of the nonlinear dynamics is treated explicitly. By way of illustration, the time evolution of the flow over a tall isolated seamount on the sphere is simulated. The seamount height is 90% of the mean sea depth. Vortex shedding and Taylor caps are observed. The simulation compares well with results published by other authors.  相似文献   

Healthier Geographies: Mediating the Gaps between the Needs of People Living with HIV and AIDS and Health Care in Chiang Mai,Thailand     

Vincent J. Del Casino Jr. 《The Professional geographer》2013,65(3):407-421

In this article, I contribute to our understanding of the plurality of approaches that construct the geographies of health care through an examination of the distribution of health care services for people living with HIV/AIDS (PLWHA) in Chiang Mai Province, Thailand. In particular, I focus on the development of a network of support groups for PLWHA in order to examine the differences in the sociospatial organization of these groups, the practices of social actors participating in the groups' activities, and how these activities are mediated through place-based social relations. The first section of the article analyzes the spatial distribution of PLWHA support groups in relation to the distribution of AIDS cases over two time periods, 1994 and 1997. The second section goes below the surface of the spatial distribution, examining similarities and differences in PLWHA support groups through an analysis of survey data collected on thirty-five groups in 1997. The final section deepens this examination through an analysis of ethnographic data collected on the outreach efforts of one nongovernmental organization (NGO) and one PLWHA support group with which it worked. Each section offers opportunities for the extension of our understanding of the development of PLWHA support groups, their distribution in relation to the spread of AIDS cases, and their place-based meanings.  相似文献   

Benchmarking spatial joins a la carte     

Oliver Gunther  Philippe Picouet  Jean-Marc Saglio  Michel Scholl  Vincent Oria 《International journal of geographical information science》2013,27(7):639-655

Spatial joins are join operations that involve spatial data types and operators. Spatial access methods are often used to speed up the computation of spatial joins. This paper addresses the issue of benchmarking spatial join operations. For this purpose, we first present a WWW-based benchmark generator to produce sets of rectangles. Using a Web browser, experimenters can specify the number of rectangles in a sample, as well as the statistical distributions of their sizes, shapes, and locations. Second, using the generator and a well-defined set of statistical models we define several tests to compare the performance of three spatial join algorithms: nested loop, scan-and-index, and synchronized tree traversal. We also added two real-life data sets from the Sequoia 2000 storage benchmark. Our results show that the relative performance of the different techniques mainly depends on the selectivity factor of the join predicate. All of the statistical models and algorithms are available on the Web, which allows for easy verification and modification of our experiments.  相似文献   

Corrigendum to the note “Evidence of Quaternary active folding near Utique (Northeast Tunisia) from tectonic observations and a seismic profile” [C. R. Geoscience 342 (11) (2010) 864–72]     

Lassaad Mejri  Vincent Regard  Sébastien Carretier  Stéphane Brusset  Mahmoud Dlala 《Comptes Rendus Geoscience》2012,344(9):471

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A set-membership approach for high integrity height-aided satellite positioning   总被引：1，自引：0，他引：1  

Vincent Drevelle  Philippe Bonnifait 《GPS Solutions》2011,15(4):357-368

A Robust Set-Inversion via Interval Analysis method in a bounded-error framework is used to compute three-dimensional location zones in real time, at a given confidence level. This approach differs significantly from the usual Gaussian error model paradigm, since the satellite positions and the pseudorange measurements are represented by intervals encompassing the true value with a particular level of confidence. The method computes a location zone recursively, using contractions and bisections of an arbitrarily large initial location box. Such an approach can also handle an arbitrary number of erroneous measurements using a q-relaxed solver and allows the integration of geographic and cartographic information such as digital elevation models or three-dimensional maps. With enough data redundancy, inconsistent measurements can be detected and even rejected. The integrity risk of the location zone comes only from the measurement bounds settings, since the solver is guaranteed. A method for setting these bounds for a particular location zone confidence level is proposed. An experimental validation using real L1 code measurements and a digital elevation model is also reported in order to illustrate the performance of the method on real data.  相似文献   

Heat budget of the surface mixed layer south of Africa     

Vincent Faure  Michel Arhan  Sabrina Speich  Sergey Gladyshev 《Ocean Dynamics》2011,61(10):1441-1458

ARGO hydrographic profiles, two hydrographic transects and satellite measurements of air–sea exchange parameters were used to characterize the properties and seasonal heat budget variations of the Surface Mixed Layer (SML) south of Africa. The analysis distinguishes the Subtropical domain (STZ) and the Subantarctic Zone (SAZ), Polar Frontal Zone (PFZ) and Antarctic Zone (AZ) of the Antarctic Circumpolar Current. While no Subantarctic Mode Water forms in that region, occurrences of deep SML (up to ∼450 m) are observed in the SAZ in anticyclones detached from the Agulhas Current retroflection or Agulhas Return Current. These are present latitudinally throughout the SAZ, but preferentially at longitudes 10–20° E where, according to previous results, the Subtropical Front is interrupted. Likely owing to this exchange window and to transfers at the Subantarctic Front also enhanced by the anticyclones, the SAZ shows a wide range of properties largely encroaching upon those of the neighbouring domains. Heat budget computations in each zone reveal significant meridional changes of regime. While air–sea heat fluxes dictate the heat budget seasonal variability everywhere, heat is mostly brought through lateral geostrophic advection by the Agulhas Current in the STZ, through lateral diffusion in the SAZ and through air–sea fluxes in the PFZ and AZ. The cooling contributions are by Ekman advection everywhere, lateral diffusion in the STZ (also favoured by the ∼10° breach in the Subtropical Front) and geostrophic advection in the SAZ. The latter likely reflects an eastward draining of water warmed through mixing of the subtropical eddies.  相似文献