A comparison of rainfall estimation techniques for sub-Saharan Africa     

Elias Symeonakis  Rogerio Bonifaçio  Nick Drake 《International Journal of Applied Earth Observation and Geoinformation》2009

Interpolated rain-gauge data were compared to Meteosat-based precipitation estimates for sub-Saharan Africa. Validation was carried out using a dataset from a very dense gauge network in South Africa, on a point-to-pixel (PO–PI) as well as on a pixel-to-pixel (PI–PI) basis. Error criteria computed at the gauged pixels indicate that overall the interpolated estimates perform similarly to the satellite-based data: they provide good estimates of lower but underestimate larger precipitation amounts. It is concluded that the satellite estimates are more fitted for the operational modelling of processes such as surface runoff and soil erosion, especially in the developing areas where resources are scarce.  相似文献   

Provenance and tectonic setting of the metapelites deposits in the Bulfat Complex,NE-Iraq     

Elias M. Elias  Zahraa J. Al-Jubory 《Arabian Journal of Geosciences》2014,7(9):3589-3598

Major and trace elements including rare earth elements (REEs) chemistry of the metapelitic rocks of Bulfat Complex (Iraqi Zagros Suture Zone) indicate their enrichment in large-ion Lithophile, light rare earth (LREE) elements, and relative depletion of high field strength and heavy rare earth (HREE) elements. The linear correlation coefficients between TiO₂, K₂O, and Al₂O₃ and total REE reveal that phyllosilicates (e.g., mica) and accessory minerals mainly Ti-bearing phases (e.g., ilmenite) are likely the dominant hosts for REEs. Chondrite-normalized REE patterns typical of continental margin settings with significant enrichment of LREE, prominent negative Eu anomalies, and nearly flat HREE are positively correlated with post-Archean Australian shale (PAAS) and upper continental crust (UCC) patterns. Additionally, their consistent elemental La/Sc, Th/Sc, La/Co, Th/Co, Cr/Th, and Eu/Eu* values suggest that sediments may have been originally derived from an old post-Archean upper continental crust composed chiefly of granitic component. It seems most likely that the felsic source rocks were originated by a process of intra-crustal differentiation such as partial melting and/or fractional crystallization involving fractionation of Ca-plagioclase. The geochemical evidences particularly REEs evaluation show that deposition of clasts occurred in an active continental margin setting during lower–upper Cretaceous period contemporaneous with the igneous activities. It is evident therefore that the clasts source is from the north–northeast side, i.e., from the active margin of Iranian microcontinent (Sanandaj–Sirjan Zone).  相似文献   

Puhimau Thermal Area: A Window into the Upper East Rift Zone of Volcano, Hawaii?     

K. A. McGee  A. J. Sutton  T. Elias  M. P. Doukas  T. M. Gerlach 《Pure and Applied Geophysics》2006,163(4):837-851

We report the results of two soil CO₂ efflux surveys by the closed chamber circulation method at the Puhimau thermal area in the upper East Rift Zone (ERZ) of volcano, Hawaii. The surveys were undertaken in 1996 and 1998 to constrain how much CO₂ might be reaching the ERZ after degassing beneath the summit caldera and whether the Puhimau thermal area might be a significant contributor to the overall CO₂ budget of . The area was revisited in 2001 to determine the effects of surface disturbance on efflux values by the collar emplacement technique utilized in the earlier surveys. Utilizing a cutoff value of 50 g m⁻² d⁻¹ for the surrounding forest background efflux, the CO₂ emission rates for the anomaly at Puhimau thermal area were 27 t d⁻¹ in 1996 and 17 t d⁻¹ in 1998. Water vapor was removed before analysis in all cases in order to obtain CO₂ values on a dry air basis and mitigate the effect of water vapor dilution on the measurements. It is clear that Puhimau thermal area is not a significant contributor to CO₂ output and that most of CO₂ (8500 t d⁻¹) is degassed at the summit, leaving only magma with its remaining stored volatiles, such as SO₂, for injection down the ERZ. Because of the low CO₂ emission rate and the presence of a shallow water table in the upper ERZ that effectively scrubs SO₂ and other acid gases, Puhimau thermal area currently does not appear to be generally well suited for observing temporal changes in degassing at .  相似文献   

Asiago Supernova classification program: Blowing out the first two hundred candles     

L. Tomasella  S. Benetti  E. Cappellaro  A. Pastorello  M. Turatto  R. Barbon  N. Elias‐Rosa  A. Harutyunyan  P. Ochner  L. Tartaglia  S. Valenti 《Astronomische Nachrichten》2014,335(8):841-849

We present the compilation of the first 221 supernovae classified during the Asiago Classification Program (ACP). The details of transients classification and the preliminarily reduced spectra, in fits format, are immediately posted on the Padova‐Asiago SN group web site. The achieved performances for the first 2 years of the ACP are analysed, showing that half of all our classifications were made within 5 days from transient detection. The distribution of the supernova types of this sample resembles the distribution of the general list of all the supernovae listed in the Asiago SN catalog (ASNC, Barbon et al. 1999). Finally, we use our subsample of 78 core‐collapse supernovae, for which we retrieve the host‐galaxy morphology and r ‐band absolute magnitudes, to study the observed subtype distribution in dwarf compared to giant galaxies. This ongoing program will give its contribution to the classification of the large number of transients that will be soon delivered by the Gaia mission. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Deformed Messinian markers in the Cyprus Arc: tectonic and/or Messinian Salinity Crisis indicators?     

Agnès Maillard  Christian Hübscher  Jean Benkhelil  Elias Tahchi 《Basin Research》2011,23(2):146-170

This paper focuses on Messinian Salinity Crisis (MSC) evaporites in the Cyprus Arc (eastern Mediterranean) using high‐resolution reflection seismic and multi‐beam data. The results shed new light on the Miocene to Present tectonic evolution of this area and contribute to our general knowledge of the MSC in a deep basin setting. The evaporites and overlying formations show a complex deformation pattern due to a combination of thick‐skinned plate‐tectonic convergence and thin‐skinned disharmonic deformation related to the mobile evaporite‐bearing unit. Several MSC markers are identified and precisely mapped: the base of the MSC unit is a ‘decollement’ level, whereas the top is clearly identified as a toplap surface. Intra‐MSC markers and two MSC subunits are identified and mapped over the entire study area. The geometry of MSC markers shows that the lower MSC subunit was deposited in a relatively quiet tectonic setting. The nature of the anisopachous upper unit indicates a syn‐depositional phase of large‐scale plate‐tectonic activity. A thin‐skinned phase of compressional deformation during the Late Miocene affected the entire MSC unit, overlain by undeformed Pliocene–Quaternary layers. A second thin‐skinned phase, well expressed in the bathymetry, occurred from the Pliocene to Recent, resulting in extensional gravity‐gliding within the evaporites and the Pliocene–Quaternary sequence. We show that the MSC had a dramatic impact on the regional structure. For instance, the erosive nature of the top of the MSC unit is linked to the desiccation episode rather than to the cessation of tectonic activity. This particularly strong and short‐lived erosion may have been enhanced by the regional effects of the MSC, owing to differential uplift/subsidence caused by the drawdown. The evaporites are essential markers for constraining the tectonic framework, provided that active deformation can be distinguished from passive gliding associated with extensional/contractional deformation.  相似文献   

The grazing encounter between IC 2163 and NGC 2207: pushing the limits of observational modelling     

Curtis Struck  Michele Kaufman  Elias Brinks †  Magnus Thomasson  Bruce G. Elmegreen  Debra Meloy Elmegreen 《Monthly notices of the Royal Astronomical Society》2005,364(1):69-90

  相似文献   

New techniques for integral field spectroscopy – II. Performance of the GNIRS IFU     

Jeremy Allington-Smith  Cornelis M. Dubbeldam  Robert Content  David Robertson  James Turner  Bernadette Rodgers  Jonathan Elias  Joris Gerssen †  Mark Swinbank 《Monthly notices of the Royal Astronomical Society》2007,376(2):785-792

  相似文献   

Localized climate change scenarios of mean temperature and precipitation over Switzerland     

Elias M. Zubler  Andreas M. Fischer  Mark A. Liniger  Mischa Croci-Maspoli  Simon C. Scherrer  Christof Appenzeller 《Climatic change》2014,125(2):237-252

There is a growing need of the climate change impact modeling and adaptation community to have more localized climate change scenario information available over complex topography such as in Switzerland. A gridded dataset of expected future climate change signals for seasonal averages of daily mean temperature and precipitation in Switzerland is presented. The basic scenarios are taken from the CH2011 initiative. In CH2011, a Bayesian framework was applied to obtain probabilistic scenarios for three regions within Switzerland. Here, the results for two additional Alpine sub-regions are presented. The regional estimates have then been downscaled onto a regular latitude-longitude grid with a resolution of 0.02° or roughly 2 km. The downscaling procedure is based on the spatial structure of the climate change signals as simulated by the underlying regional climate models and relies on a Kriging with external drift using height as auxiliary predictor. The considered emission scenarios are A1B, A2 and the mitigation scenario RCP3PD. The new dataset shows an expected warming of about 1 to 6 °C until the end of the 21st century, strongly depending on the scenario and the lead time. Owing to a large vertical gradient, the warming is about 1 °C stronger in the Alps than in the Swiss lowlands. In case of precipitation, the projection uncertainty is large and in most seasons precipitation can increase or decrease. In summer a distinct decrease of precipitation can be found, again strongly depending on the emission scenario.  相似文献   

Key climate indices in Switzerland; expected changes in a future climate     

Elias M. Zubler  Simon C. Scherrer  Mischa Croci-Maspoli  Mark A. Liniger  Christof Appenzeller 《Climatic change》2014,123(2):255-271

Climate indices facilitate the interpretation of expected climate change impacts for many sectors in society, economy, and ecology. The new localized data set of climatic change signals for temperature and precipitation presented by Zubler et al. (Clim Change, 2013) is applied for an analysis of frequently used climate indices in Switzerland. The indices considered are: number of summer days and tropical nights, growing season length, number of frost days and ice days, heating and cooling degree days, and the number of days with fresh snow. For the future periods 2020-49, 2045-74 and 2070–2099 the indices are computed using a delta-change approach based on the reference period 1980–2009 for the emission scenarios A1B, A2, and RCP3PD. The scenario data suggest the following relevant findings: (1) a doubling of the number of summer days by the end of the century under the scenarios A1B and A2, (2) an appearance of tropical nights even above 1500 m asl, (3) a possible reduction of the number of frost days by more than 3 months at altitudes higher than 2500 m asl, (4) a decline of heating degree days by about 30 % until the end of the century, and (5) the near disappearance of days with fresh snow at low altitudes. It is also shown that the end-of-the-century projections of all indices strongly depend on the chosen emission scenario.  相似文献   

Seismic response analysis of an interacting curved bridge–train system under frequent earthquakes          下载免费PDF全文

Qing Zeng  Elias G. Dimitrakopoulos 《地震工程与结构动力学》2016,45(7):1129-1148

This paper establishes a scheme for the seismic analysis of interacting vehicle–bridge systems. The focus is on (horizontally) curved continuous railway bridges and frequent earthquakes. Main features of the proposed scheme are (i) the treatment of the dynamics in all three dimensions (3D), employing an additional rotating system of reference to describe the dynamics of the vehicles and a realistic 3D bridge model; (ii) the simulation of the creep interaction forces generated by the rolling contact between the wheel and the rail; and (iii) the integration of the proposed scheme with powerful commercial finite element software, during the pre‐processing and post‐processing phases of the analysis. The study brings forward the dynamics of a realistic vehicle–bridge (interacting) system during seismic shaking. For the (vehicle–bridge) case examined, the results verify the favorable damping effect the running vehicles have on the vibration of the deck. By contrast, the study stresses the adverse influence of the earthquake‐induced bridge vibration on the riding comfort but, more importantly, on the safety of the running vehicles. In this context, the paper unveils also a vehicle–bridge–earthquake timing problem, behind the most critical vehicle response, and underlines the need for a probabilistic treatment. Among the 20 sets of historic records examined, the most crucial for the safety of the vehicles are near‐fault ground motions. Finally, the study shows that even frequent earthquakes, of moderate intensity, can threaten the safety of vehicles running on bridges during the ground motion excitation, in accordance with recorded accidents. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献