Observation of the thermal structure and dynamics of the stratosphere and the mesosphere from space     

Alain Hauchecorne  Philippe Keckhut  Chantal Claud  Francis Dalaudier  Anne Garnier 《Comptes Rendus Geoscience》2010,342(4-5):323-330

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From whom Bells tolls: Reclassifying Bells among CR chondrites and implications for the formation conditions of CR parent bodies     

Yves Marrocchi  Emmanuel Jacquet  Julia Neukampf  Johan Villeneuve  Michael E. Zolensky 《Meteoritics & planetary science》2023,58(2):195-206

The ungrouped carbonaceous chondrite (CC) Bells has long been considered petrographically similar to CM chondrites based on its matrix abundance and degree of aqueous alteration, but also shows significant isotopic affinities to CR chondrites. Its taxonomic status is thus important for clarifying the relationship of the CRHB (formerly “CR”) clan with other CCs. In this study, we measured the oxygen isotopic compositions of olivines in type I chondrules and isolated olivine grains in Bells. Bells olivines mostly have ∆¹⁷O > −4‰, similar to CR chondrites but unlike other CCs that are rich in refractory inclusions, in which chondrules are generally richer in ¹⁶O. Therefore, Bells is a CR chondrite (albeit an anomalous one), most similar to the rare, matrix-rich CRs like Al Rais. These chondrites (i) may not necessarily derive from the same primary parent body as mainstream CRs, (ii) bear witness to significant variations of the matrix/chondrule ratio within the CRHB clan, and (iii) may be a good analog for samples retrieved by the space mission OSIRIS-REx.  相似文献   

Selection of Less Biased Threshold Angles for SAM Classification Using the Real Value–Area Fractal Technique     

Hadi Shahriari  Hojjatollah Ranjbar  Mehdi Honarmand  Emmanuel John M. Carranza 《Resource Geology》2014,64(4):301-315

The accuracy of classification of the Spectral Angle Mapping (SAM) is warranted by choosing the appropriate threshold angles, which are normally defined by the user. Trial‐and‐error and statistical methods are commonly applied to determine threshold angles. In this paper, we discuss a real value–area (RV–A) technique based on the established concentration–area (C–A) fractal model to determine less biased threshold angles for SAM classification of multispectral images. Short wave infrared (SWIR) bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images were used over and around the Sar Cheshmeh porphyry Cu deposit and Seridune porphyry Cu prospect. Reference spectra from the known hydrothermal alteration zones in each study area were chosen for producing respective rule images. Segmentation of each rule image resulted in a RV–A curve. Hydrothermal alteration mapping based on threshold values of each RV–A curve showed that the first break in each curve is practical for selection of optimum threshold angles. The hydrothermal alteration maps of the study areas were evaluated by field and laboratory studies including X–ray diffraction analysis, spectral analysis, and thin section study of rock samples. The accuracy of the SAM classification was evaluated by using an error matrix. Overall accuracies of 80.62% and 75.45% were acquired in the Sar Cheshmeh and Seridune areas, respectively. We also used different threshold angles obtained by some statistical techniques to evaluate the efficiency of the proposed RV–A technique. Threshold angles provided by statistical techniques could not enhance the hydrothermal alteration zones around the known deposits, as good as threshold angles obtained by the RV–A technique. Since no arbitrary parameter is defined by the user in the application of the RV‐A technique, its application prevents introduction of human bias to the selection of optimum threshold angle for SAM classification.  相似文献   

Mineralogy and geochemical behaviour during weathering of greenstone belt under tropical dry conditions in the extreme North Cameroon (Central Africa)     

Jean Pierre Nguetnkam  Fredéric Villiéras  Richard Kamga  Georges Emmanuel Ekodeck  Jacques Yvon 《Chemie der Erde / Geochemistry》2014

Mineralogy, major, trace and rare earth elements of a weathering profile developed on tertiary greenstone belt in the extreme North Cameroon are reported. The aim of which was to investigate mineralogical evolution and element mobilization and redistribution during weathering under dry tropical climate. The weathering profile consists of four main horizons: (1) a spheroidal weathering zone constituted by a corestone–shell complex, (2) a C horizon, (3) a Bw horizon and an Ah horizon. The results indicate that nontronite, a Fe-rich smectite, is the exclusive clay mineral formed in the exfoliated shells and the C horizon. It is associated with kaolinite in the upper horizons. The coexistence of these two clay minerals induced a decrease of CEC and pH which becomes neutral. The weathering index (WI) values reveal that weathering becomes more and more intensive from the corestone up to Bw horizon, which is the most weathered horizon in the weathering profile. Mass balance calculations, using Th as immobile element, indicate that Ti is quite mobile and that Al and Fe are relatively enriched at the bottom and strongly leached at the top of the profile. Alkalis and alkaline earth elements are strong leached through out the profile, except Ca which displays similar trend as Al and Fe. The same goes for LILE (Cs, Sr), TTE (Cr, Co, Ni) and HSFE (Y, Nb, Hf). In opposite, REE are depleted at the bottom and enriched in the upper horizons, with more enrichment for LREE than for HREE. It appears that weathering of greenstone belt causes a fractionation of HREE and induces a concentration of LREEs. Ce and Eu anomalies display opposite behaviour.  相似文献   

Human choices and environmental constraints: deciphering the variability of large game procurement from Mousterian to Aurignacian times (MIS 5-3) in southwestern France     

Emmanuel Discamps  Jacques Jaubert  François Bachellerie 《Quaternary Science Reviews》2011,30(19-20):2755-2775

The evolution in the selection of prey made by past humans, especially the Neandertals and the first anatomically modern humans, has been widely debated. Between Marine Isotope Stages (MIS) 5 and 3, the accuracy of absolute dating is still insufficient to precisely correlate paleoclimatic and archaeological data. It is often difficult, therefore, to estimate to what extent changes in species procurement are correlated with either climate fluctuations or deliberate cultural choices in terms of subsistence behavior. Here, the full development of archeostratigraphy and Bayesian statistical analysis of absolute dates allows the archeological and paleoclimatic chronologies to be compared. The variability in hunted fauna is investigated using multivariate statistical analysis of quantitative faunal lists of 148 assemblages from 39 archeological sequences from MIS 5 through MIS 3. Despite significant intra-technocomplex variability, it is possible to identify major shifts in the human diet during these stages. The integration of archeological data, paleoclimatic proxies and the ecological characteristics of the different species of prey shows that the shifts in large game hunting can be explained by an adaptation of the human groups to climatic fluctuations. However, even if Middle and Early Upper Paleolithic men adapted to changes in their environment and to contrasting landscapes, they ultimately belonged to the ecosystems of the past and were limited by environmental constraints.  相似文献   

Preliminary spectral characterization of snow in a high altitude tropical glacier and potential effects of impurities in snow on albedo of tropical glaciers     

Jean Emmanuel Sicart  Yves Arnaud 《水文研究》2007,21(26):3642-3644

This paper presents some preliminary measurements of snow spectral reflectance on the tropical Bolivian Zongo glacier. Measurements show a correct agreement with theoretical spectral albedo of pure snow in the near infrared region, but lower values in the visible region (by 10–20%) probably due to aerosols contained in snow. Impurity contents ranged from 10 to 100 ppmw in one‐week‐old snow collected from the Zongo glacier, but measurements are scarce. Large amounts of snowfall partly compensate the proximity of dust sources in mid‐latitude glaciers, whereas on outer‐tropical glaciers precipitations are not abundant and are very seasonal, and sources of aerosols are proximate. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Latitudinal variations of CO and OCS in the lower atmosphere of Venus from near-infrared nightside spectro-imaging     

Emmanuel Marcq  Bruno Bézard  Mirel Birlan 《Icarus》2005,179(2):375-386

Spectro-imaging of Venus' nightside in the 2.3-μm window provides a powerful means of probing the lower atmosphere in the 25-40 km altitude range. We present observations recorded at the NASA/IRTF in February 2003 and August 2004, using the SpeX spectro-imager in the 2.1-2.5-μm region. Abundances of CO and OCS have been derived as a function of latitude for different longitudes. The CO abundance increases by about 15% between the equatorial region and higher latitudes (±40°). No longitudinal or temporal variations are observed. The OCS abundance shows the opposite variation in observational sets with sufficient S/N. These variations and anticorrelation are consistent with upwelling motions in the equatorial region and downwelling at higher latitudes.  相似文献   

Simulating daily soil water under foothills fescue grazing with the soil and water assessment tool model (Alberta,Canada)     

Emmanuel Mapfumo  David S. Chanasyk  Walter D. Willms 《水文研究》2004,18(15):2787-2800

Grazing is common in the foothills fescue grasslands and may influence the seasonal soil‐water patterns, which in turn determine range productivity. Hydrological modelling using the soil and water assessment tool (SWAT) is becoming widely adopted throughout North America especially for simulation of stream flow and runoff in small and large basins. Although applications of the SWAT model have been wide, little attention has been paid to the model's ability to simulate soil‐water patterns in small watersheds. Thus a daily profile of soil water was simulated with SWAT using data collected from the Stavely Range Sub‐station in the foothills of south‐western Alberta, Canada. Three small watersheds were established using a combination of natural and artificial barriers in 1996–97. The watersheds were subjected to no grazing (control), heavy grazing (2·4 animal unit months (AUM) per hectare) or very heavy grazing (4·8 AUM ha^?1). Soil‐water measurements were conducted at four slope positions within each watershed (upper, middle, lower and 5 m close to the collector drain), every 2 weeks annually from 1998 to 2000 using a downhole CPN 503 neutron moisture meter. Calibration of the model was conducted using 1998 soil‐water data and resulted in Nash–Sutcliffe coefficient (EF or R²) and regression coefficient of determination (r²) values of 0·77 and 0·85, respectively. Model graphical and statistical evaluation was conducted using the soil‐water data collected in 1999 and 2000. During the evaluation period, soil water was simulated reasonably with an overall EF of 0·70, r² of 0·72 and a root mean square error (RMSE) of 18·01. The model had a general tendency to overpredict soil water under relatively dry soil conditions, but to underpredict soil water under wet conditions. Sensitivity analysis indicated that absolute relative sensitivity indices of input parameters in soil‐water simulation were in the following order; available water capacity > bulk density > runoff curve number > fraction of field capacity (FFCB) > saturated hydraulic conductivity. Thus these data were critical inputs to ensure reasonable simulation of soil‐water patterns. Overall, the model performed satisfactorily in simulating soil‐water patterns in all three watersheds with a daily time‐step and indicates a great potential for monitoring soil‐water resources in small watersheds. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Data-Driven Evidential Belief Modeling of Mineral Potential Using Few Prospects and Evidence with Missing Values     

Emmanuel John M. Carranza 《Natural Resources Research》2015,24(3):291-304

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The Shear Testing Programme – I. Weak lensing analysis of simulated ground-based observations     

Catherine Heymans  Ludovic Van Waerbeke  David Bacon  Joel Berge  Gary Bernstein  Emmanuel Bertin  Sarah Bridle  Michael L. Brown  Douglas Clowe  Håkon Dahle  Thomas Erben  Meghan Gray  Marco Hetterscheidt  Henk Hoekstra  Patrick Hudelot  Mike Jarvis  Konrad Kuijken  Vera Margoniner  Richard Massey  Yannick Mellier  Reiko Nakajima  Alexandre Refregier  Jason Rhodes  Tim Schrabback  David Wittman 《Monthly notices of the Royal Astronomical Society》2006,368(3):1323-1339

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