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91.
On the basis of investigations carried out since 1966 at Mount Etna, the temperatures of erupting magmas are shown to be determined within a few °C in the range 1000–1200°C, by using suitable techniques and apparatus. The best measurements are obtained from sheathed thermocouples that are briefly described. Particularly, a new continuously recording multithermocouple system has been designed, tested satisfactorily, and compared with the performances of other pyrometers. However, a certain standardization of measurements is necessary to obtain and discuss the results: measurements should be made at lava vents or a few meters away and at least 30–50 cm into the flows, the highest values only being considered as significant.The magmatic temperatures and petrological characters appear closely related to the volcanic activity. In the normal state of moderate persistent activity of Mount Etna, the alkaline basic magma extrudes at a nearly constant temperature of 1080°C (corresponding to about 50% crystalline phases), meanwhile during stronger paroxysmal eruptions the magma temperature is higher (1125°C and possibly more) with a lower observed content of phenocrysts. 相似文献
92.
This article offers an analysis of the emerging scalar configuration of the governance of the European Union. It discusses how European integration stands for a move from a collection of territorially homogenous systems of rule towards a new assemblage of territories, authorities and rights. The paper first questions the stretchy territoriality of the seemingly obvious European level. Second it analyses the sectoral differences in the evolution of the width and the depth of integration, measured as the transfer of competencies to the EU level between the Rome Treaty (1958) and the Lisbon Treaty (200y). Third it turns to the day-to-day decision-making to assess the relations between players in EU governance and finally it looks more closely at the administrative wheels of the EU machinery. 相似文献
93.
94.
Georges Durry Alain Hauchecorne Joelle Ovarlez Henri Ovarlez Ivan Pouchet Virginie Zeninari Bertrand Parvitte 《Journal of Atmospheric Chemistry》2002,43(3):175-194
Telecommunication laser diodes emitting near 1.39 m and 1.65 m in combination with direct-differential absorption spectroscopy are efficient tools to monitor in situ stratospheric H2O andCH4 with a good precision error (a few percents), a high temporal resolution (ranging from 10 ms to 1 s), a large dynamic range in the concentration measurements (four orders of magnitude) and a high selectivity in the analyte species. To illustrate the capability of laser probing technique, we report balloonborne H2Oand CH4 simultaneous measurements obtained on October 2001 atmidlatitudes (43° N). The H2O vertical profile achieved with the lasersensor in the lower stratosphere is compared with the H2O data yielded by a balloonborne frost-point hygrometer. The total hydrogen mixing ratio in the lower stratosphere, 2[CH4] + [H2O], appears to beconstant at 7.5 ± 0.1 ppmv. Nevertheless, an unexpected largedehydration of 0.5 ppmv was detected by both the laser sensor and thehygrometer between 16 km and 23 km. We suspect the occurrence of a tropicalair intrusion into mid-latitudes. We support this interpretation using a high-resolution advection model for potential vorticity. 相似文献
95.
96.
Stable SO4 isotopes (δ34S-SO4 and δ18O-SO4), and more occasionally δ15N-NO3 were studied in groundwater from seven hard-rock aquifer catchments. The sites are located in Brittany (France) and all are characterized by intensive agricultural activity. The purpose of the study was to investigate the potential use of these isotopes for highlighting the fate of both SO4 and NO3 in the different aquifer compartments. Nitrate-contaminated groundwater occurs in the regolith; δ34S fingerprints the origin of SO4, such as atmospheric deposition and fertilizers, and δ18O-SO4 provides evidence of the cycling of S within soil. The correlation between the δ18O-SO4 of sulfates and the δ15N-NO3 of nitrates suggests that S and N were both cycled in soil before being leached to groundwater. Autotrophic and heterotrophic denitrification was noted in fissured aquifers and in wetlands, respectively, the two processes being distinguished on the basis of stable SO4 isotopes. During autotrophic denitrification, both δ34S-SO4 and δ18O-SO4 decrease due to the oxidation of pyrite and the incorporation of O from the NO3 molecule in the newly formed SO4. Within wetlands, fractionation occurs of O isotopes on SO4 in favour of lighter isotopes, probably through reductive assimilation processes. Fractionation of S isotopes is negligible as the redox conditions are not sufficiently reductive for dissimilatory reduction. δ34S-SO4 and δ18O-SO4 data fingerprint the presence of a NO3-free brackish groundwater in the deepest parts of the aquifer. Through mixing with present-day denitrified groundwater, this brackish groundwater can contribute to significantly increase the salinity of pumped water from the fissured aquifer. 相似文献
97.
Frédéric Hourdin Marie-Alice Foujols Francis Codron Virginie Guemas Jean-Louis Dufresne Sandrine Bony Sébastien Denvil Lionel Guez François Lott Josefine Ghattas Pascale Braconnot Olivier Marti Yann Meurdesoif Laurent Bopp 《Climate Dynamics》2013,40(9-10):2167-2192
The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m2 which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m2 when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged. 相似文献