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131.
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
132.
Marie Lothon Fleur Couvreux Sylvie Donier Françoise Guichard Pierre Lacarrère Donald H. Lenschow Joël Noilhan Frédérique Saïd 《Boundary-Layer Meteorology》2007,124(3):425-447
During the Hydrological-Atmospheric Pilot Experiment (HAPEX)-Sahel, which took place in Niger in the transitional period between
the wet and dry seasons, two French aircraft probed the Sahelian boundary layer to measure sensible and latent heat fluxes.
The measurements over the Niamey area often revealed organised structures of a few km scale that were associated with both
thermals and dry intrusions. We study the impact of these coherent structures using a single day’s aircraft-measured fluxes
and a numerical simulation of that day with a mesoscale model. The numerical simulation at high horizontal resolution (250 m)
contains structures that evolve from streaks in the early morning to cells by noon. This simulation shows distribution, variance
and skewness similar to the observations. In particular, the numerical simulation shows dry intrusions that can penetrate
deeply into the atmospheric boundary layer (ABL), and even reach the surface in some cases, which is in accordance with the
observed highly negatively skewed water vapour fluctuations. Dry intrusions and thermals organised at a few km scale give
skewed flux statistics and can introduce large errors in measured fluxes. We use the numerical simulation to: (i) evaluate
the contribution of the organised structures to the total flux, and (ii) estimate the impact of the organised structures on
the systematic and random errors resulting from the 1D sampling of the aircraft as opposed to the 2D numerical simulation
estimate. We find a significant contribution by the organised structures to the total resolved fluxes. When rolls occur, and
for a leg length of about 30 times the ABL depth, the 1D sampled flux is shown to be sometimes 20% lower than the corresponding
2D flux when the 1D sampling direction is the same as the main axis of the rolls, whereas the systematic error is much lower
when the direction of the leg is transverse to the rolls. In the case of cells, an underestimate of around 10% can still be
observed with the 1D approach independent of direction, due to poor sampling of the energy-containing scales. 相似文献
133.
Danièle Valdes Jean-Paul Dupont Nicolas Massei Benoît Laignel Joël Rodet 《Comptes Rendus Geoscience》2005,337(15):1365-1374
In karst systems, rain events often result in a decrease of the conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. This study shows that the comparison of suspended solids and solute transport by the coupled approach of curves (Turbidity–Conductivity) and autocorrelations gives evidence of the transport processes in the karst network and allows understanding the karst hydrodynamics. To cite this article: D. Valdes et al., C. R. Geoscience 337 (2005). 相似文献
134.
Fabien Arnaud Joël Serralongue Thierry Winiarski Marc Desmet Martine Paterne 《Comptes Rendus Geoscience》2006,338(4):244-252
In Lake Anterne (NW French Alps), the Roman period is characterised by a lead contamination more important than that of the 1970s, due to the use of leaded gasoline. The maximum of this contamination period has been varve-dated 220 AD, i.e., during the optimum of Roman civilization in the Alps. Crossing palaeoenvironmental and archaeological evidences points out the economic importance of the town of Passy for the City of Vienne and yields a new example of lead contamination due to local metallurgical activity rather than distant impact of the exploitation of the Spanish Rio Tinto mine. To cite this article: F. Arnaud et al., C. R. Geoscience 338 (2005). 相似文献
135.
Michaël Heller 《Astrophysics and Space Science》1975,33(2):L33-L35
The so-called dominant energy condition and the strong energy condition (of singularity theorems) cannot be violated by the negative effective ‘pressure’ arising from the inhomogeneous distribution of matter in the Universe. 相似文献
136.
Max Bouët 《Theoretical and Applied Climatology》1958,9(3-4):323-326
Résumé Les cumulus de beau temps et les cumulonibus locaux ont leur base comprise entre 1500 et 4500 m. dans les Alpes valaisannes (Suisse); l'altitude moyenne s'établit à 3160 m. Variation diurne et saisonnière du niveau de condensation et spectre de fréquence.
Summary In the Alps of the Valais (Switzerland) the base of the height of the fine weather cumuli and of the cumulo-nimbi of local character is situated between 1500 and 4500 m. above sea level; the average height is 3160 m. The diurnal and the annual variation of the condensation height and the frequency distribution are discussed.
Zusammenfassung Die Basishöhe der Schönwettercumuli und der Cumulonimben lokalen Charakters liegt in den Walliser Alpen (Schweiz) zwischen 1500 und 4500 m über Meer; die mittlere Höhe beträgt 3160 m. Es werden die Tages- und die Jahresschwankung der Kondensationshöhe und Frequenzverteilung untersucht.相似文献
137.
138.
139.
Manuëlla Delalande Laurent Bergonzini Fabrizio Gherardi Massimo Guidi Luc Andre Issah Abdallah David Williamson 《Journal of Volcanology and Geothermal Research》2011,199(1-2):127-141
The South Poroto–Rungwe geothermal field, in the northern part of the Malawi rift, Tanzania divides in two main areas. The relatively high altitude northern area around the main Ngozi, Rungwe, Tukuyu and Kyejo volcanoes, is characterised by cold and gas-rich springs. In contrast, hot springs occur in the southern and low-altitude area between the Kyela and Livingstone faults. The isotopic signature of the almost stagnant, cold springs of the Northern district is clearly influenced by H2O–CO2(g) exchange as evidenced from negative oxygen-shifts in the order of few deltas permil. In contrast, the isotopic signature of waters discharged from the hot springs of the Southern district is markedly less affected by the H2O–CO2(g) interaction. This evidence is interpreted as an effect of the large, permanent outflow of these springs, which supports the hypothesis of a regional-scale recharge of the major thermal springs. Measurements of carbon isotope variations of the dissolved inorganic carbon of waters and CO2(g) from the Northern and Southern springs support a model of CO2(g)-driven reactivity all over the investigated area. Our combined chemical and isotopic results show that the composition of hot springs is consistent with a mixing between (i) cold surface fresh (SFW) and (ii) Deep Hot Mineralised (DHMW) Water, indicating that the deep-originated fluids also supply most of the aqueous species dissolved in the surface waters used as local potable water. Based on geothermometric approaches, the temperature of the deep hydrothermal system has been estimated to be higher than 110 °C up to 185 °C, in agreement with the geological and thermal setting of the Malawi rift basin. Geochemical data point to (i) a major upflow zone of geothermal fluids mixed with shallow meteoric waters in the Southern part of the province, and (ii) gas absorption phenomena in the small, perched aquifers of the Northern volcanic highlands. 相似文献
140.
Determination of Boron Concentration in Geochemical Reference Materials Extracted by Pyrohydrolysis and Measured by ICP‐MS 下载免费PDF全文
Agnès Michel Johanna Noireaux Mickaël Tharaud 《Geostandards and Geoanalytical Research》2015,39(4):489-495
This article presents new boron concentrations for nine geochemical reference materials (GS‐N, FK‐N, GL‐O, BX‐N, DT‐N, AN‐G, GH, Mica‐Fe, Mica‐Mg). After extraction by a modified pyrohydrolysis technique, boron concentrations were measured by ICP‐MS. The blank levels for the whole procedure were 0.091 ± 0.020 ng ml?1 or 14 ± 5 ng of boron in total. The method was first validated by measuring nine reference materials with known boron concentrations. The determined boron concentrations are all within the range of recommended or published values, which means that the yields were 100%, and show precisions below 10% for samples containing over 2 μg g?1 of boron. 相似文献