Assessing uncertainties in the building of ensemble RCMs over Spain based on dry spell lengths probability density functions     

J. D. Giraldo Osorio  S. G. García Galiano 《Climate Dynamics》2013,40(5-6):1271-1290

Spain is one of the European countries with most environmental problems related to water scarcity and droughts. Additionally, several studies suggest trends of increasing temperature and decreasing rainfall, mainly for the Iberian Peninsula, due to climate variability and change. While Regional Climate Models (RCM) are a valuable tool for understanding climate processes, the causes and plausible impacts on variables and meteorological extremes present a wide range of associated uncertainties. The multi-model ensemble approach allows the quantification and reduction of uncertainties in the predictions. The combination of models (RCM in this case), generally increases the reliability of the predictions, although there are different weighting methodologies. In this paper, a strategy is presented for the building of non-stationary PDF (probability density functions) ensembles with the aim of evaluating the spatial pattern of future risk of drought for an area. At the same time, the uncertainty associated with the metric used in the construction of the PDF ensembles is assessed. A comparative study of methodologies based on the application of the Reliability Ensemble Averaging (REA), assessing its factors using two performance measures, on the one hand the Perkins Score Methods, on the other hand the Kolmogorov-Smirnov test, is proposed. The evaluation of the sensitivity of the methodologies used in the construction of ensembles, as proposed in this paper, although without completely eliminating uncertainty, allows a better understanding of the sources and magnitude of the uncertainties involved. Despite the differences between the spatial distribution results from each metric (which can be in the order of 40 % in some areas), both approaches concluded about a plausible significant and widespread increase throughout continental Spain of the mean value of annual maximum dry spell lengths (AMDSL) between the years 1990 and 2050. Finally, the more parsimonious approach in the building of ensembles PDF, based on AMDSL in peninsular Spain, is identified.  相似文献   

Could bulk density profiles provide information about recent sedimentation rates?     

José-María Abril 《Journal of Paleolimnology》2011,46(2):173-186

Independent validation has to be an integral part of the ²¹⁰Pb-based radiometric dating of recent sediments. The combined use of artificial fallout radionuclides leads to serious problems because only the identification of peaks and their use as time-marks is not sufficiently rigorous to ensure the accuracy of dates. Quantitative modelling of depth profiles requires reliable input functions, which can be substantially different from the atmospheric deposition records. The appropriate treatment of compaction is another source of complexity. Continuum mechanics provide a suitable framework to understand compaction in sedimentary basins with length scales of several km. Nevertheless, early compaction (with length scales of few cm at the sediment surface) takes place under hydrostatic equilibrium conditions, and it can be better understood as a transport phenomenon: a mass flow governed by spatial gradients of a compaction-potential energy, involving a conductivity function. This paper explores some analytical and numerical solutions for these equations to provide insight about the early compaction phenomenon. Given a conductivity function and a constant sedimentation rate, the system will evolve towards a steady-state profile for bulk density. The fingerprint of variable sedimentation rates, among other changes in environmental conditions, will be studied with numerical solutions. Finally, the paper explores the use of bulk density profiles for deriving information on recent sedimentation rates, which could provide independent support for the radiometric dating models.  相似文献   

Structure and recent evolution of the Hazar Basin: a strike‐slip basin on the East Anatolian Fault,Eastern Turkey     

D. Garcia Moreno  A. Hubert‐Ferrari  J. Moernaut  J. G. Fraser  X. Boes  M. Van Daele  U. Avsar  N. Çağatay  M. De Batist 《Basin Research》2011,23(2):191-207

The Hazar Basin is a 25 km‐long, 7 km‐wide and 216 m‐deep depression located on the central section of the East Anatolian Fault zone (eastern Turkey) and predominantly overlain by Lake Hazar. This basin has been described previously as a pull‐apart basin because of its rhombic shape and an apparent fault step‐over between the main fault traces situated at the southwestern and northeastern ends of the lake. However, detailed structural investigation beneath Lake Hazar has not been undertaken previously to verify this interpretation. Geophysical and sedimentological data from Lake Hazar were collected during field campaigns in 2006 and 2007. The analysis of this data reveals that the main strand of the East Anatolian Fault (the Master Fault) is continuous across the Hazar Basin, connecting the two segments previously assumed to be the sidewall faults of a pull‐apart structure. In the northeastern part of the lake, an asymmetrical subsiding sub‐basin, bounded by two major faults, is cross‐cut by the Master Fault, which forms a releasing bend within the lake. Comparison of the structure revealed by this study with analogue models produced for transtensional step‐overs suggests that the Hazar Basin structure represents a highly evolved pull‐apart basin, to the extent that the previous asperity has been bypassed by a linking fault. The absence of a step‐over structure at the Hazar Basin means that no significant segmentation boundary is recognised on the East Anatolian Fault between Palu and Sincik. Therefore, this fault segment is capable of causing larger earthquakes than recognised previously.  相似文献   

Sign of the amount of nonconservation energy in entropic cosmology     

Samuel Lepe  Francisco Peña 《Astrophysics and Space Science》2014,350(1):401-406

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Principal moments of inertia and secular love number of Phobos     

M. Burša 《Earth, Moon, and Planets》1988,42(1):49-53

A dynamic homogeneous model of Phobos is used: its boundary is an equipotential surface specified by the second zonal and the second sectorial harmonics plus the constant part of the tidal potential due to Mars. The principal moments of inertia, the hydrostatic second zonal harmonic and the secular Love number of Phobos have been estimated. They support the hypothesis that Phobos is formed out of primordial matter by accretion in orbit.  相似文献   

Orbital structure in oscillating galactic potentials     

Bal&#;a Terzi&#;  Henry E. Kandrup † 《Monthly notices of the Royal Astronomical Society》2004,347(3):957-967

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The cosmological evolution of colour gradients in spheroids     

A.C.S. Friaça  R.J. Terlevich † 《Monthly notices of the Royal Astronomical Society》2001,325(1):335-342

The analysis of the four-colour maps of galaxies in the Hubble Deep Field (HDF) has revealed, in the sample of 0.4< z <1 early-type field galaxies, the existence of ellipticals with a predominantly old coeval stellar population. However, there is another, unexpected, category of HDF early-type galaxies, in which the galaxy core is significantly bluer than the outer regions. We demonstrate that these colour gradients are predicted by the multizone chemodynamical model for the evolution of elliptical galaxies.
We suggest that the colour gradient could be used as a chronometer for the evolution of elliptical galaxies: galaxies younger than a few Gyr exhibit cores bluer than the surrounding galaxy as a result of ongoing star formation, while more evolved galaxies have redder cores because of metallicity gradients increasing toward the centre.  相似文献   

First Results on it p Modes from GOLF Experiment     

M. Lazrek  F. Baudin  L. Bertello  P. Boumier  J. Charra  D. Fierry-Fraillon  E. Fossat  A. H. Gabriel  R. A. García  B. Gelly  C. Gouiffes  G. Grec  P. L. Pallé  F. Pérez Hernández  C. Régulo  C. Renaud  J.-M. Robillot  T. Roca Cortés  S. Turck-Chièze  R. K. Ulrich 《Solar physics》1997,175(2):227-246

The GOLF experiment on the SOHO mission aims to study the internal structure of the Sun by measuring the spectrum of global oscillations in the frequency range 10^-7 to 10^-2 Hz. Here we present the results of the analysis of the first 8 months of data. Special emphasis is put into the frequency determination of the p modes, as well as the splitting in the multiplets due to rotation. For both, we show that the improvement in S/N level with respect to the ground-based networks and other experiments is essential in achieving a very low-degree frequency table with small errors ∼ 2 parts in 10^-5). On the other hand, the splitting found seems to favour a solar core which does not rotate slower than its surface. The line widths do agree with theoretical expectations and other observations.  相似文献   

A photometric–spectroscopic analysis and the evolutionary status of the Algol-type binary U Coronae Borealis     

S. K. Yerli  M. J. Sarna  S. Zo&#;a  Robert Connon Smith  G. Tovmassian 《Monthly notices of the Royal Astronomical Society》2003,342(4):1349-1360

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Asynchroneity of maximum glacier advances in the central Spanish Pyrenees     

Jos M. García‐Ruiz  Blas L. Valero‐Garcs  Carlos Martí‐Bono  Penlope Gonzlez‐Sampriz 《第四纪科学杂志》2003,18(1):61-72

The deglaciation history of the Escarra and Lana Mayor glaciers (Upper Gállego valley, central Spanish Pyrenees) had been reconstructed on the basis of detailed geomorphological studies of glacier deposits, sedimentological and palynological analyses of glacial lake sediments and an accelerator mass spectrometry (AMS) ¹⁴C chronology based on minimum ages from glacial lake deposits. The maximum extent of the Pyrenean glaciers during the last glaciation was before 30 000 yr BP and pre‐dated the maximum advances of the Scandinavian Ice Sheet and some Alpine glaciers. A later advance occurred during the coldest period (around 20 000 yr BP), synchronous with the maximum global ice extent, but in the Pyrenees it was less extensive than the previous one. Later, there were minor advances followed by a stage of debris‐covered glaciers and a phase of moraine formation near cirque backwalls. The deglaciation chronology of the Upper Gállego valley provides more examples of the general asynchroneity between mountain and continental glaciers. The asynchroneity of maximum advances may be explained by different regional responses to climatic forcing and by the southern latitude of the Pyrenees. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献