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151.
B. Cros P. Durand H. Cachier Ph. Drobinski E. Frjafon C. Kottmeier P. E. Perros V. -H. Peuch J. -L. Ponche D. Robin F. Saïd G. Toupance H. Wortham 《Atmospheric Research》2004,69(3-4):241-279
In this paper, the “Expérience sur Site pour COntraindre les Modèles de Pollution atmosphérique et de Transport d'Emissions” (ESCOMPTE) program is presented. The ESCOMPTE program is used to produce a relevant set of data for testing and evaluating regional pollution models. It includes high-resolution (in space and time) atmospheric emission inventories and field experiments, and covers an area of 120×120 km, centered over the Marseilles-Berre area in the southeast of France during Summer 2001. This region presents a high occurrence of photochemical pollution events, which result from numerous industrial and urban sources of primary pollutants. From the dynamical characteristics of the area, sea-breeze circulation and channeling effects due to terrain features highly influence the location of the pollutant plumes. ESCOMPTE will provide a highly documented framework for dynamics and chemistry studies.Campaign strategies and experimental set up are described. During the planning phase, existing modeling results helped defining the experimental design. The campaign involved surface measurement networks, remote sensing, ship-borne, balloon-borne, and airplane measurements. Mean standard meteorological parameters and turbulent fluxes, ozone, ozone precursors, photochemically active trace gases, and aerosols were measured. Five intensive observation periods (IOPs) were documented using a wide spectrum of instruments, involving aircraft (7) (one of them equipped with a Doppler lidar, the others for in situ meteorological and chemical measurements), constant volume balloons (33), ozone lidars (5), wind profilers (15 sodars and radars), Doppler scanning lidar (1), radiosonde systems (at 4 locations), instrumented ships (2). In addition to the air quality networks from environmental agencies, 15 supplementary ground stations equipped for chemistry and/or meteorology and/or surface flux measurements, were operational. All instruments were calibrated and compared during a Quality Control/Quality Assurance (QC/QA) week, at the very beginning of the campaign.Fifteen days were intensively documented during five IOPs, referenced as 1, 2a, 2b, 3, and 4. High pollution levels were encountered during sea-breeze conditions observed during IOPs 2b and 3, whereas IOPs 2a and 4 corresponded to moderate wind, and channeled plume regimes. In addition, hourly emissions inventories for all IOPs were established to complete data sets and to finalize the ESCOMPTE database (EDB).Two other projects were associated to ESCOMPTE: urban boundary layer (UBL) and tropospheric water vapor content by GPS tomography (GPS/H2O). They took advantage of the scientific environment provided by ESCOMPTE. 相似文献
152.
153.
Hahn Chul Jung James Hamski Michael Durand Doug Alsdorf Faisal Hossain Hyongki Lee A. K. M. Azad Hossain Khaled Hasan Abu Saleh Khan A.K.M. Zeaul Hoque 《地球表面变化过程与地形》2010,35(3):294-304
The Surface Water and Ocean Topography (SWOT) satellite mission will provide global, space‐based estimates of water elevation, its temporal change, and its spatial slope in fluvial environments, as well as across lakes, reservoirs, wetlands, and floodplains. This paper illustrates the utility of existing remote sensing measurements of water temporal changes and spatial slope to characterize two complex fluvial environments. First, repeat‐pass interferometric SAR measurements from the Japanese Earth Resources Satellite are used to compare and contrast floodplain processes in the Amazon and Congo River basins. Measurements of temporal water level changes over the two areas reveal clearly different hydraulic processes at work. The Amazon is highly interconnected by floodplain channels, resulting in complex flow patterns. In contrast, the Congo does not show similar floodplain channels and the flow patterns are not well defined and have diffuse boundaries. During inundation, the Amazon floodplain often shows sharp hydraulic changes across floodplain channels. The Congo, however, does not show similar sharp changes during either infilling or evacuation. Second, Shuttle Radar Topography Mission measurements of water elevation are used to derive water slope over the braided Brahmaputra river system. In combination with in situ bathymetry measurements, water elevation and slope allow one to calculate discharge estimates within 2.3% accuracy. These two studies illustrate the utility of satellite‐based measurements of water elevation for characterizing complex fluvial environments, and highlight the potential of SWOT measurements for fluvial hydrology. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
154.
Rony Keppens Hubert Baty Jeroen Bergmans Fabien Casse 《Astrophysics and Space Science》2004,293(1-2):217-224
A suitable model for the macroscopic behavior of accretion disk-jet systems is provided by the equations of MagnetoHydroDynamics (MHD). These equations allow us to perform scale-encompassing numerical simulations of multidimensional nonlinear magnetized plasma flows. For that purpose, we continue the development and exploitation of the Versatile Advection Code (VAC) along with its recent extension which employs dynamically controlled grid adaptation. In the adaptive mesh refinement AMRVAC code, modules for simulating any-dimensional special relativistic hydro- and magnetohydrodynamic problems are currently operational. Here, we review recent 3D MHD simulations of fundamental plasma instabilities, relevant when dealing with cospatial shear flow and twisted magnetic fields. Such magnetized jet flows can be susceptible to a wide variety of hydro (e.g. Kelvin-Helmholtz) or magnetohydrodynamic (e.g. current driven kink) instabilities. Recent MHD computations of 3D jet flows have revealed how such mutually interacting instabilities can in fact aid in maintaining jet coherency. Another breakthrough from computational magnetofluid modeling is the demonstration of continuous, collimated, transmagnetosonic jet launching from magnetized accretion disks. Summarizing, MHD simulations are rapidly gaining realism and significantly advance our understanding of nonlinear astrophysical magnetofluid dynamics. 相似文献
155.
156.
Karine Grangeré Sébastien Lefebvre Alain Ménesguen Fabien Jouenne 《Estuarine, Coastal and Shelf Science》2009
In many ecosystem models based on empirical formulations, parameters generally are calibrated in order to achieve the best fit between measured and simulated chlorophyll a standing stocks. An accurate calibration of rate processes as primary production rarely is taken into account. In this paper, we test the usefulness of calibration of phytoplankton photosynthetic processes in an ecosystem model using field primary production data. We used 18 months of photosynthetic process data from the Baie des Veys ecosystem (Normandy, France). Five empirical formulations of photosynthesis–irradiance curve models amongst the most widely used were tested. In each formulation, the variability of photosynthetic parameters (i.e. the light-saturated rate of photosynthesis (PmaxB) and the initial slope of the photosynthesis–light curve (αB)) was considered depending on environmental factors (temperature and nutrient availability). The fit of the five equations as well as the calibration of parameters on field measurements (i.e. the light-saturated rate of photosynthesis (PrefB), the initial slope of the photosynthesis–light curve (αrefB), the half-saturation constant for nitrogen (KN) and silicates uptake (KSi), and the coefficient in the exponential thermal effect (KT)) was performed using the whole available data set of P vs. E curves (n = 143, P vs. E curves). Then, the Smith formulation allowing the best simulation of the Baie des Veys primary production and corresponding parameters were introduced in an ecosystem box model. This formulation led directly to a satisfactory representation of the Baie des Veys phytoplankton dynamics without additional calibration. Results obtained were compared with a more classical approach in which ecosystem models were calibrated using published values of parameters. This comparison showed that for the two years studied, annual primary production estimated through the ecosystem model was 13% and 26% higher with our approach than with the more classical approach. This work emphasizes the importance of accurately representing rate processes in ecosystem models in order to adequately simulate production as well as standing stocks. 相似文献
157.
Estimating boundary currents from satellite altimetry: A case study for the east coast of India 总被引:1,自引:0,他引:1
Fabien Durand Doraiswamy Shankar Florence Birol S. Satheesh Chandra Shenoi 《Journal of Oceanography》2008,64(6):831-845
We present a methodology to derive surface geostrophic current from a newly released altimetric sea-level data set. TOPEX/Poseidon
data were first completely reprocessed from Geophysical Data Records using new algorithms accommodating marginal seas and
coastal conditions. The methodology applied to the reprocessed data essentially consists of a smoothing of the raw along-track
coastal altimetric data at scales at which the geostrophic equilibrium holds. This was reduced to a computational procedure
using a set of objective criteria. We have applied the method to the East India Coastal Current (EICC) at the western boundary
of the Bay of Bengal. This paper first examines the quality of the new data set, which compares well with tide-gauge data;
the current we derived is consistent with independent estimates. Our methodology reveals the full spectrum of the along-shore
current, ranging from intra-seasonal to inter-annual time scales, from the deep ocean to the shelf-break area where the EICC
exists. The algorithm can be applied to any coastal region where an order of the Rossby radius can be defined, and it therefore
opens up bright prospects for mapping the variability of other boundary-current systems in the world ocean from altimetry. 相似文献
158.
159.
Cyril Durand Didier Marquer Lukas Baumgartner Philippe Goncalves Philippe Boulvais Michel Rossy 《Contributions to Mineralogy and Petrology》2009,157(6):749-763
Chemical mass transfer was quantified in a metacarbonate xenolith enclosed within the granodiorite of the Quérigut massif
(Pyrenees, France). Mass balance calculations suggest a strong decrease of CaO, SrO and CO2 contents (up to −90%), correlated with a decrease of modal calcite content as the contact is approached. Most other chemical
elements behave immobile during metasomatism. They are therefore passively enriched. Only a small increase of SiO2, Al2O3 and Fe2O3 contents occurs in the immediate vicinity of the contact. Hence, in this study, skarn formation is characterized by the lack
of large chemical element influx from the granitoid protolith. A large decrease of the initial carbonate volume (up to −86%)
resulted from a combination of decarbonation reactions and loss of CaO and CO2. The resulting volume change has potentially important consequences for the interpretation of stable isotope profiles: the
isotope alteration could have occured over greater distances than those observed today. 相似文献
160.
This study aims at understanding the physico-chemical interactions between the saturated brine and the rocks enclosing the
underground salt workings in Lorraine (eastern France). These anhydrite-rich and argillaceous rocks were characterized in
terms of mineralogy, micro-texture and connected porosity. Then, the two main lithofacies, massive anhydrite and anhydrite-rich
argillite, were immersed in brine during more than 1 year. During this batch experiment, the argillites were affected by macroscopic
splitting, contrarily to the massive anhydrite. Micro-texture and brine chemical analyses clearly show the swelling due to
the hydration of anhydrite into gypsum inside the argillites, whereas hydration occurs superficially on the massive anhydrite,
due to its very low permeability. Anhydrite–gypsum transformation is promoted by the presence of dissolved strontium and potassium
in saturated brine. The low activity of water in saturated brine does not allow the clay fraction to swell significantly during
the experiment. Thus, the expansion resulting from the hydration of anhydrite into gypsum might be responsible of the splitting
of argillite in a saturated brine environment. The superficial anhydrite hydration on massive anhydrite can be explained by
the low amount of connected porosity (less than 1%). 相似文献