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61.
Valérie Estupina Borrell Jacques Chorda Denis Dartus 《Comptes Rendus Geoscience》2005,337(13):1109-1119
Flash-flood events resulting from paroxystic meteorological events concentrated in time and space are insufficiently documented as they produce destructive effects. They are hardly measurable and present single features that are not transposable to another event. In the South of France, the flash flood of November 1999 gives a perfect illustration of these characteristics. The physical complexity of the process and consequently the volume and the variety of the data to take into account are incompatible with the real time constraint allocated to the forecasters confronted to the occurrence of such phenomena. So, we have to make choices to afford acceptable simplifications to the complete mechanical model. MARINE (‘Modélisation de l'Anticipation du Ruissellement et des Inondations pour des évéNements Extrêmes’) is the operational and robust tool we developed for flash-flood forecasting. This model complies with the criterions of real-time simulation. It is a physically based distributed model composed of two parts: first the flood runoff process simulation in the upstream part of the basin modelled from a rainfall–runoff approach, then the flood propagation in the main rivers described by the Saint-Venant equations. It integrates remote sensed data – Digital Elevation Model, land-use map, hydrographic network for the observations from satellites and the rainfall evolution from meteorological radar. The main goal of MARINE is to supply real time pertinent information to the forecasters. Results obtained on the Orbieu River (Aude, France) show that this model is able to supply pertinent flood hydrograph with a sufficient precision for the forecasting service to take the appropriate safety decisions. Furthermore, MARINE has already been tested in the French National Flood Forecasting Service of Haute-Garonne in real conditions. To cite this article: V. Estupina Borrell et al., C. R. Geoscience 337 (2005). 相似文献
62.
Aude Lemonsu Sophie Bastin Valéry Masson Philippe Drobinski 《Boundary-Layer Meteorology》2006,118(3):477-501
During the UBL-ESCOMPTE program (June–July 2001), intensive observations were performed in Marseille (France). In particular, a Doppler lidar, located in the north of the city, provided radial velocity measurements on a 6-km radius area in the lowest 3 km of the troposphere. Thus, it is well adapted to document the vertical structure of the atmosphere above complex terrain, notably in Marseille, which is bordered by the Mediterranean sea and framed by numerous massifs. The present study focuses on the last day of the intensive observation period 2 (26 June 2001), which is characterized by a weak synoptic pressure gradient favouring the development of thermal circulations. Under such conditions, a complex stratification of the atmosphere is observed. Three-dimensional numerical simulations, with the Méso-NH atmospheric model including the town energy balance (TEB) urban parameterization, are conducted over south-eastern France. A complete evaluation of the model outputs was already performed at both regional and city scales. Here, the 250-m resolution outputs describing the vertical structure of the atmosphere above the Marseille area are compared to the Doppler lidar data, for which the spatial resolution is comparable. This joint analysis underscores the consistency between the atmospheric boundary layer (ABL) observed by the Doppler lidar and that modelled by Méso-NH. The observations and simulations reveal the presence of a shallow sea breeze (SSB) superimposed on a deep sea breeze (DSB) above Marseille during daytime. Because of the step-like shape of the Marseille coastline, the SSB is organized in two branches of different directions, which converge above the city centre. The analysis of the 250-m wind fields shows evidence of the role of the local topography on the local dynamics. Indeed, the topography tends to reinforce the SSB while it weakens the DSB. The ABL is directly affected by the different sea-breeze circulations, while the urban effects appear to be negligible. 相似文献
63.
In situ carbon flux measurements and calculated burial rates are utilized to construct an organic carbon budget for the upper meter of sediment at a single station in Cape Lookout Bight, a small marine basin located on the Outer Banks of North Carolina, U.S.A. (34°37′N, 76°33′W). Of 149 ± 20 mole · m?2 · yr?1 of total organic carbon deposited, 35.6 ± 5.2 mole · m?2 · yr?1 is recycled to overlying waters, 84 ± 18% as ∑CO2 and 16 ± 8% as CH4. Approximately 68 ± 20% of the upward carbon flux is supported by sulfate reduction while 32 ± 16% takes place as the result of underlying methanogenesis. Measured ∑CO2 and CH4 sediment-water fluxes range seasonally from 1900–6300 and 50–2500 μmole · m?2 · hr?1 respectively.The mean residence time of metabolizable organic carbon in the upper 80 cm of sediment is approximately four months with greater than 98% of the calculated total remineralization taking place within three years. In spite of large upward fluxes of methane, larger molecules derived from metabolizable sedimentary organic carbon appear to be the dominant reductants for dissolved sulfate. 相似文献
64.
The masses of 12 protostars assumed to be the central bodies in circumstellar protoplanetary disks are estimated based on analysis of their methanol maser spectra and fine spatial structure. The calculations are based on the hypothesis that the class II methanol maser lines are formed in an edge-on Keplerian disk, while the thermal methanol emission and CS lines are formed in a cocoon around the protostar. This provides information about the velocities of the protostar and the methanol maser condensations relative to the center. In most of the star-forming regions studied, the derived masses are within limits admissible for disks around massive OB stars. The masses are in good agreement with the calculations of other authors based on models of the velocity gradients of the maser features. It is suggested that the methanol spectra display a triplet structure in which the two lateral features are class II methanol lines and the central component is a class I methanol maser line or thermal methanol line. This is consistent with the fact that the correlation of regions of maser emission with regions of emission of dense molecular gas in the CS line is about twice as strong(about 100%) as the correlation with ultracompact HII regions (about 50%). This should be taken into account when modeling protoplanetary disks and star-forming regions. 相似文献
65.
J. Val KLUMP David N. EDGINGTON James T. WAPLES Donald C. SZMANIA Bruce E. BROWN Kent A. ORLANDINI 《国际泥沙研究》2003,(2)
1 INTRODUCTION Sediment resuspension, particularly in response to episodic storm events, is a common characteristic of coastal and nearshore environments. The resulting 揵enthic storms?may play a significant role in the dynamics of benthic systems, including structuring the physical characteristics of the bottom, providing a mechanism for the recycling of biogeochemically important materials to the water column, and driving horizontal and cross margin transport of suspended particulates … 相似文献
66.
The paper reports the results of a survey of Galactic star-forming regions in the methanol lines 8?1–70 E at 229.8 GHz, 3?2–4?1 E at 230.0 GHz, 00–1?1 E at 108.9 GHz, and a series of J 1–J 0 E lines near 165 GHz. In addition to the methanol lines, lines of methyl cyanide (CH3CN), cyanoacetylene (HC3N), methyl formate (HCOOCH3), and sulphur dioxide (SO2) were detected. Analysis of the data indicates that the methanol emission arises in warm (30–50 K) gas. 相似文献
67.
68.
Marie-Noëlle Bouin Valérie Ballu Stéphane Calmant Bernard Pelletier 《Journal of Geodesy》2009,83(11):1017-1030
Satellite altimetry provides an ocean mean sea surface (MSS) map with global coverage and overall excellent precision. However,
in some areas, like the Vanuatu archipelago, the coverage and resolution of this tool are not sufficient to correctly map
the short scale undulations of the sea surface, due to numerous islands and to strong lithospheric and mantle heterogeneities.
New applications such as seafloor geodesy may require local mean surface representation with improved resolution in specific
areas. We used sea surface height collected with kinematic GPS during three different cruises in 2004, 2006 and 2007 to reconstruct
a homogeneous sea surface map around Santo Island, Vanuatu. We assess the accuracy of this GPS-derived local sea surface to
6–19 cm and evaluate the quality of existing altimetry and gravity-derived MSSs on the Vanuatu archipelago. Observed short
scale undulations are interpreted as due to local geodynamics. 相似文献
69.
Absolute seafloor vertical positioning using combined pressure gauge and kinematic GPS data 总被引:1,自引:0,他引:1
Valérie Ballu Marie-Noelle Bouin Stéphane Calmant Eric Folcher Jean-Michel Bore Jérome Ammann Olivier Pot Michel Diament Bernard Pelletier 《Journal of Geodesy》2010,84(1):65-77
Knowledge of the position and motion of points on the seafloor can be critically important in both fundamental research (for
example, global geodesy and plate tectonics) and for more practical applications such as seismic risk evaluation, off-shore
construction and pipeline monitoring. In the Vanuatu subduction zone, for example, measuring deformation underwater could
provide valuable information for modeling deformation and understanding the seismic cycle. We report a shallow water experiment
in Vanuatu to measure the relative and absolute depth of seafloor points. The experiment differs from previous efforts mainly
in that it uses the height of the sea surface determined by kinematic GPS, allowing us to locate the points in a global reference
frame. The ITRF2005 ellipsoidal height of a seafloor benchmark was determined with a 1-sigma uncertainty of 0.7–2.1 cm. The
estimated ellipsoidal height differs only by a few tenths of a centimeter between measurements made in 2004 and another set
made in 2006. These results are encouraging and open new perspectives for vertical underwater deformation monitoring in shallow
water areas. Sea-surface GPS measurements can also help to reduce the uncertainty in depth difference determination for relative
measurements. 相似文献
70.
Xiaolan L. Wang Hui Wan Francis W. Zwiers Val R. Swail Gilbert P. Compo Robert J. Allan Russell S. Vose Sylvie Jourdain Xungang Yin 《Climate Dynamics》2011,37(11-12):2355-2371
This study analyzes extremes of geostrophic wind speeds derived from sub-daily surface pressure observations at 13 sites in the European region from the Iberian peninsula to Scandinavia for the period from 1878 or later to 2007. It extends previous studies on storminess conditions in the Northeast (NE) Atlantic-European region. It also briefly discusses the relationship between storminess and the North Atlantic Oscillation (NAO). The results show that storminess conditions in the region from the Northeast Atlantic to western Europe have undergone substantial decadal or longer time scale fluctuations, with considerable seasonal and regional differences (especially between winter and summer, and between the British Isles-North Sea area and other parts of the region). In the North Sea and the Alps areas, there has been a notable increase in the occurrence frequency of strong geostrophic winds from the mid to the late twentieth century. The results also show that, in the cold season (December–March), the NAO-storminess relationship is significantly positive in the north-central part of this region, but negative in the south-southeastern part. 相似文献