Envisat and SARAL/AltiKa Observations of the Antarctic Ice Sheet: A Comparison Between the Ku-band and Ka-band     

Frédérique Rémy  Thomas Flament  Aurélie Michel  Denis Blumstein 《Marine Geodesy》2015,38(3):510-521

The AltiKa altimeter onboard SARAL is a joint CNES/ISRO mission launched in February 2013 that has the same 35 days repeat orbit of the previous European altimeters, Envisat, and ERS-1/2. SARAL/AltiKa is thus a unique opportunity to extend the repeat observations of this orbit that have been surveyed since 1991. However, the altimeter operates in Ka-band, which is higher than the previous frequencies, and offers new paths of investigation. The penetration depth is theoretically reduced from around 10 m in Ku-band to less than 1 m in Ka-band, such that the volume echo originates from the near subsurface. Second, the sharper antenna aperture leads to a narrower leading edge that reduces the impact of the ratio between surface and volume echoes of the height retrieval. Indeed, the spatial and temporal observations of AltiKa at cross-over points and along-track indicate that the impact of backscatter changes on the height decreasesfrom 0.3 m/dB for the Ku-band to only 0.05 m/dB for the Ka-band. Therefore, the height measurement is stable over time. Moreover, the volume echo in the Ka-band results from the near subsurface layer and is mostly controlled by ice grain size, unlike the Ku-band.  相似文献   

Deep reflection seismic imaging of the internal zone of the South Armorican Hercynian belt (western France) (ARMOR 2/Géofrance 3D Program)     

Adnand Bitri  Jean-Pierre Brun  Denis Gapais  Florence Cagnard  Charles Gumiaux  Jean Chantraine  Guillaume Martelet  Catherine Truffert 《Comptes Rendus Geoscience》2010,342(6):448-452

We present results and interpretation of a 72 km long deep seismic reflection profile acquired across the internal zone of the Hercynian belt of South Brittany. The profile is of excellent quality, most of the crust being highly reflective. The “ARMOR 2 South” profile, is correlated with the “ARMOR 2 North” profile that was published in 2003. Correlation of the main subsurface reflections with surface geological and structural data provides important information about the crustal structure that resulted from thickening during Late Devonian and regional-scale extension during Late Carboniferous. In particular, seismics image shows a very high reflectivity zone, lying flat over more than 40 km at about 10–12 km depth. This zone is interpreted as a major zone of ductile crustal thinning.  相似文献   

The water impacts of climate change mitigation measures     

Philip J. Wallis  Michael B. Ward  Jamie Pittock  Karen Hussey  Howard Bamsey  Amandine Denis  Steven J. Kenway  Carey W. King  Shahbaz Mushtaq  Monique L. Retamal  Brian R. Spies 《Climatic change》2014,125(2):209-220

A variety of proposed activities to mitigate greenhouse gas emissions will impact on scarce water resources, which are coming under increasing pressure in many countries due to population growth and shifting weather patterns. However, the integrated analysis of water and carbon impacts has been given limited attention in greenhouse mitigation planning. In this Australian case study, we analyse a suite of 74 mitigation measures ranked as highest priority by one influential analysis, and we find that they have highly variable consequences for water quantity. We find: (1) The largest impacts result from land-based sequestration, which has the potential to intercept large quantities of water and reduce catchment yields, estimated to exceed 100 Mm³/MtCO₂-e of carbon mitigated (100,000 l per tonne CO₂-e). (2) Moderate impacts result from some renewable power options, including solar thermal power with a water cost estimated at nearly 4 Mm³/MtCO₂-e. However, the water impacts of solar thermal power facilities could be reduced by designing them to use existing power-related water supplies or to use air or salt-water cooling. (3) Wind power, biogas, solar photovoltaics, energy efficiency and operational improvements to existing power sources can reduce water demand through offsetting the water used to cool thermal power generation, with minor savings estimated at 2 Mm³/MtCO₂-e and amounting to nearly 100 Mm³ of water saved in Australia per annum in 2020. This integrated analysis significantly changes the attractiveness of some mitigation options, compared to the case where water impacts are not considered.  相似文献   

Interpreting CO2–SIc relationship to estimate CO2 baseline in limestone aquifers     

N. Peyraube  R. Lastennet  A. Denis  P. Malaurent  J. D. Villanueva 《Environmental Earth Sciences》2014,72(10):4207-4215

Saturation index with respect to calcite (SIc) and equilibrium CO₂ partial pressure are important parameters to study groundwater in limestone aquifers. Aside from their use in time series, CO₂ and SIc are used to estimate the baseline of CO₂ in the vadose zone. The objective of this paper is to present conceptual examples on the use of the CO₂–SIc relationship to have new information from usual parameters. Case study was considered as an example of use from Cussac site, a limestone aquifer in southwest of France. The result showed that CO₂ baseline in unsaturated zone is found close to 25,000 ± 1,000 ppm.  相似文献   

The lower limit of the Doppler factor for a Fermi blazar sample     

Jun-Hui Fan  Denis Bastieri  Jiang-He Yang  Yi Liu  Tong-Xu Hua  Yu-Hai Yuan  De-Xiang Wu 《中国天文和天体物理学报》2014,(9)

We selected 457 blazars(193 flat spectrum radio quasars, 61 lowsynchrotron peaked blazars, 69 intermediate-synchrotron peaked blazars and 134high-synchrotron peaked blazars) from the second Fermi-LAT catalog(2FGL) of γ-ray sources, which have X-ray observations. We calculated the lower limits for their Doppler factors, δγ, and compared the lower limits with the available Doppler factors and the apparent superluminal velocities in the literature.  相似文献   

The activity coefficients of Fe(III) hydroxide complexes in NaCl and NaClO₄ solutions     

Frank J. Millero  Denis Pierrot 《Geochimica et cosmochimica acta》2007,71(20):4825-4833

The osmotic coefficients of FeCl₃ at 25 °C from 0.15 to 1.7 m [Rumyantsev et al., Z. Phys. Chem., 218, 1089-1127, 2004] have been used to determine the Pitzer parameters (β⁽⁰⁾, β⁽¹⁾ and C^?) for FeCl₃. Since the differences in the Pitzer coefficients of rare earths in NaCl and NaClO₄ are small, the values of Fe(ClO₄)₃ have been estimated using the differences between La(ClO₄)₃ and LaCl₃. The Pitzer coefficients for FeCl₃ combined with enthalpy and heat capacity data for the rare earths can be used to estimate the activity coefficients of Fe³⁺ in NaCl over a wide range of temperatures (0 to 50 °C) and ionic strength (0 to 6 m).The activity coefficients of Fe³⁺ in NaCl and NaClO₄ solutions have been used to determine the activity coefficients of Fe(OH)²⁺ in these solutions from the measured first hydrolysis constants of Fe³⁺ [Byrne et al., Mar. Chem., 97, 34-48, 2005]. The activity coefficients of , Fe(OH)₃ and from 0 to 50 °C have also been determined from the solubility measurements of Fe(III) in NaCl solutions [Liu and Millero, Geochim. Cosmochim Acta, 63, 3487-3497, 1999]. These activity coefficients have been fitted to the Pitzer equations. These results can be used to estimate the speciation of Fe(III) with OH⁻ in natural waters with high concentrations of NaCl from 0 to 50 °C.  相似文献   

Bias in hydraulic head measurements from multilevel vibrating-wire piezometers with excessively permeable backfill     

Young  Nathan L.  Lemieux  Jean-Michel  Locat  Pascal  Demers  Denis  Delottier  Hugo  Mony  Laura 《Hydrogeology Journal》2022,30(4):1337-1344

Hydrogeology Journal - An extensive network of multilevel vibrating-wire piezometers (VWP) was recently created to monitor the spatial and temporal variation of pore pressure (and hydraulic head)...  相似文献   

Characterization of karst systems using SIc-Pco2 method coupled with PCA and frequency distribution analysis. Application to karst systems in the Vaucluse county (Southeastern France)     

S. Minvielle  R. Lastennet  A. Denis  N. Peyraube 《Environmental Earth Sciences》2015,74(12):7593-7604

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Quantified,multi-scale X-ray fluorescence element mapping using the Maia detector array: application to mineral deposit studies     

Louise A. Fisher  Denis Fougerouse  James S. Cleverley  Christopher G. Ryan  Steven Micklethwaite  Angela Halfpenny  Robert M. Hough  Mary Gee  David Paterson  Daryl L. Howard  Kathryn Spiers 《Mineralium Deposita》2015,50(6):665-674

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Influence d'un changement climatique dû à une hausse de gaz à effet de serre sur l'agriculture au quebec     

Bhawan Singh  Mustapha El Maayar  Pierre André  Jean‐Pierre Thouez  Christopher Bryant  Denis Provençal 《大气与海洋》2013,51(2):379-399

Abstract

This study, using a climate change scenario generated by the Canadian Climate Centre (CCC) general circulation model (GCM) examines the impacts of such a climate change on agriculture in southern Quebec. Using a crop model from the Food and Agriculture Organization (FAO), yield responses of a variety of cereals, legumes, oleaginous and special crops to climate change are analysed and discussed.

Results show that under the 2 × CO₂ climate scenario the growing season would be longer and accumulation of corn heat units and growing degree days would be more important than under actual climate (1961–1990). One of the more important results of this study is that, on the one hand yield of C₃ cereals would be lower and that of C₄ cereals higher in most agricultural regions. On the other hand, the direct fertilisation effect of increased CO₂ is not considered. It must be cautioned however that we can not generalise results obtained for one legume crop to all legumes.  相似文献