Institute Fisica Of Cantabria

Santander, Spain

Institute Fisica Of Cantabria

Santander, Spain
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Garcia-Diez M.,Institute Fisica Of Cantabria | Garcia-Diez M.,University of Cantabria | Fernandez J.,University of Cantabria | Fita L.,University of Cantabria | And 2 more authors.
Quarterly Journal of the Royal Meteorological Society | Year: 2013

The seasonal dependence of Weather Research and Forecasting (WRF) model surface temperature biases and sensitivity to planetary boundary layer (PBL) schemes are jointly explored. For this purpose, the year 2001 was simulated using three different PBL schemes in a domain covering all Europe. The simulations were compared with gridded observations, upper-air data and high-frequency station data. Seasonal and daily cycles were analysed, aimed at providing a link between long-term biases and restricted case studies. The results show that the model mean bias significantly depends on the season, being warm in winter and cold in summer. The winter warm bias is related to misrepresented cold extremes, while a systematic cold bias dominates the whole temperature range in summer. Regarding PBL schemes, an overall underestimation of the entrainment is found, with the non-local Yonsei University scheme producing systematically warmer temperatures. It is shown that the opposite seasonal biases and systematic behaviour of the PBL schemes during the year lead to a different best-performing scheme in winter and summer. Moreover, the best-performing PBL scheme in an average sense is a result of the compensation of errors. The average summer results can be partially explained by a detailed case study. It is concluded that short-term studies should be used with caution to decide on the parametrizations to be used in long-term simulations. © 2012 Royal Meteorological Society.

Bharucha A.,University of Hamburg | Heinemeyer S.,Institute Fisica Of Cantabria | von der Pahlen F.,Institute Fisica Of Cantabria
European Physical Journal C | Year: 2013

We re-assess the exclusion limits on the parameters describing the supersymmetric (SUSY) electroweak sector of the MSSM obtained from the search for direct chargino-neutralino production at the LHC. We start from the published limits obtained for simplified models, where for the case of heavy sleptons the relevant branching ratio, BR(χ̃2 0 → χ̃1 0), is set to one. We show how the decay mode χ̃2 0 → χ̃1 0, which cannot be neglected in any realistic model once kinematically allowed, substantially reduces the excluded parameter region. We analyze the dependence of the excluded regions on the phase of the gaugino soft SUSY-breaking mass parameter, M1, on the mass of the light scalar tau, mτ1, on tanβ as well as on the squark and slepton mass scales. Large reductions in the ranges of parameters excluded can be observed in all scenarios. The branching ratios of charginos and neutralinos are evaluated using a full NLO calculation for the complex MSSM. The size of the effects of the NLO calculation on the exclusion bounds is investigated. We furthermore assess the potential reach of the experimental analyses after collecting 100 fb-1 at the LHC running at 13 TeV. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Herrera S.,Institute Fisica Of Cantabria | Fita L.,University of Cantabria | Fernandez J.,University of Cantabria | Gutierrez J.M.,Institute Fisica Of Cantabria
Journal of Geophysical Research: Atmospheres | Year: 2010

A state-of-the-art ensemble of regional climate model (RCM) simulations provided by the European Union-funded project ENSEMBLES is used to test the ability of RCMs to reproduce the mean and extreme precipitation regimes over Spain. To this aim, ERA-40-driven simulations at 25 km resolution are compared with the 20 km daily precipitation grid Spain02, considering the period 1960-2000. This gridded data set has been interpolated from thousands of quality-controlled stations capturing the spatial variability of precipitation over this RCM benchmark-like area with complex orography and influence of both Atlantic and Mediterranean climates. The results show a good representation of the mean regimes and the annual cycle but an overestimation of rainfall frequency leading to a wrong estimation of wet and dry spells. The amount of rainfall coming from extreme events is also deficient in the RCMs. The use of the multimodel ensemble improves the results of the individual models; moreover, discarding the worst performing models for the particular area and variable leads to improved results and reduced spread. Copyright © 2010 by the American Geophysical Union.

Torres D.F.,Catalan Institution for Research and Advanced Studies | Torres D.F.,Institute Of Ciencies Of Lespai Ieec Csic | Marrero A.Y.R.,Institute Fisica Of Cantabria | De Cea Del Pozo E.,Institute Of Ciencies Of Lespai Ieec Csic
Monthly Notices of the Royal Astronomical Society | Year: 2010

We have recently interpreted the source MAGIC J0616+225 as a result of delayed TeV emission of cosmic rays diffusing from IC 443 and interacting with a cloud in the foreground of the remnant. This model was used to make predictions for future observations, especially those to be made with the Fermi satellite. Just recently, AGILE, Fermi and Very Energetic Radiation Imaging Telescope Array System (VERITAS) have released new results of their observations of IC 443. In this paper, we compare them with the predictions of our model, exploring the GeV to TeV connection in this region of space. We use Fermi data to consider the possibility of constraining the cosmic ray diffusion features of the environment. We analyse the cosmic ray distributions, their interactions and a possible detection of the supernova remnant environment in the neutrino channel. © 2010 The Authors. Journal compilation © 2010 RAS.

Fernandez-Del-castillo E.,Institute Fisica Of Cantabria
Computing and Informatics | Year: 2012

The current middleware stacks provide varying support for the Message Passing Interface (MPI) programming paradigm. Users face a complex and heterogeneous environment where too many low level details have to be specified to execute even the simplest parallel jobs. MPI-Start is a tool that provides an interoperable MPI execution framework across the different middleware implementations to abstract the user interfaces from the underlying middleware and to allow users to execute parallel applications in a uniform way, thus bridging the gap between HPC and HTC. In this work we present the latest developments in MPI-Start and how it can be integrated in the different middleware stacks available as part of EMI, providing a unified user experience for MPI jobs.

Rodriguez M.A.,Institute Fisica Of Cantabria
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

The standard spectral scaling, S(f)∼1/fβ, has been traditionally used as a correlation measure characterizing the dynamical behavior of time series. The ubiquity of 1/f and 1/f2 spectra in many processes certainly suggests the existence of universal mechanisms, but also gives rise to the suspicion that some important features are not included in this scaling. In this paper we argue that a complete spectral scaling, including as a main variable the size of the series, S(f,T)∼Tη/fβ, which is usually considered irrelevant, gives an insight into this problem. Using synthetically generated series we show that, in general, the scaling exponent β is too generic, while the exponent associated with the size, η, gives a more specific information. Hence, we propose the use of both exponents in a scheme to classify series into different universality classes. In this way many of the processes appearing in the literature could be better identified, and much of the ambiguity that surrounds the standard spectral scaling could be clarified. © 2014 American Physical Society.

Hernan-Caballero A.,Institute Fisica Of Cantabria
Monthly Notices of the Royal Astronomical Society | Year: 2012

Obtaining accurate redshifts from mid-infrared (MIR) low-resolution (R ~ 100) spectroscopy is challenging because the wavelength resolution is too low to detect narrow lines in most cases. Yet, the number of degrees of freedom and diversity of spectral features are too high for regular spectral energy distribution (SED) fitting techniques to be convenient. Here we present a new SED-fitting-based routine for redshift determination that is optimized for MIR low-resolution spectroscopy. Its flexible template scaling increases the sensitivity to slope changes and small-scale features in the spectrum, while a new selection algorithm called maximum combined pseudo-likelihood (MCPL) provides increased accuracy and a lower number of outliers compared to the standard maximum-likelihood (ML) approach. Unlike ML approach, the MCPL approach searches for local (instead of absolute) maxima of a 'pseudo-likelihood' (PL) function, and combines results obtained for all the templates in the library to weed out spurious redshift solutions. The capabilities of the MCPL approach are demonstrated by comparing its redshift estimates to those of the regular ML approach and to the optical spectroscopic redshifts of a sample of 491 Spitzer/Infrared Spectrograph spectra from extragalactic sources at 0 < z < 3.7. The MCPL approach achieves a redshift accuracy Δ(z)/(1 + z) < 0.005 for 78 per cent of the galaxies in the sample compared to 68 per cent for the ML approach. The rate of outliers [Δ(z)/(1 + z) > 0.02] is 14 per cent for the MCPL approach and 22 per cent for the ML approach. χ 2 values for ML solutions are found to correlate with the signal-to-noise ratio of the spectra, but not with redshift accuracy. By contrast, the peak value of the normalized combined PL (γ) is found to provide a good indication on the reliability of the MCPL solution for individual sources. The accuracy and reliability of the redshifts depend strongly on the MIR SED. Sources with significant polycyclic aromatic hydrocarbon emission obtain much better results compared to sources dominated by active galactic nucleus continua. Nevertheless, for a given γ the frequency of accurate solutions and outliers is largely independent of their SED type. This reliability indicator for MCPL solutions allows to select subsamples with highly reliable redshifts. In particular, a γ > 0.15 threshold retains 79 per cent of the sources with Δ(z)/(1 + z) < 0.005 while reducing the outlier rate to 3.8 per cent. © 2012 The Author Monthly Notices of the Royal Astronomical Society. © 2012 RAS.

Herranz D.,Institute Fisica Of Cantabria | Herranz D.,University of Cantabria | Vielva P.,Institute Fisica Of Cantabria | Vielva P.,University of Cantabria
IEEE Signal Processing Magazine | Year: 2010

A tutorial on the detection, parameter estimation and statistical analysis of compact sources in Cosmic microwave background (CMB) observations is discussed. CMB anisotropies are extremely weak, and people cannot observe them directly, they observe instead a mixture of CMB and other astrophysical sources of radiation that lie along the line of sight of CMB photons. The CLEAN algorithm uses a simple iterative procedure to find the positions and strengths of these sources, going from the brightest intensity point in the image, fitting it to a source template profile, subtracting it from the data and iterating the whole process until some convergence criterion is met. Another critical aspect of compact source detection in CMB images is the spatial modeling of the image background. Another interesting possibility is to use time-frequency representations to transform the data to better characterize the signature of compact sources as compared to the generalized noise.

Frias M.D.,University of Cantabria | Minguez R.,University of Cantabria | Gutierrez J.M.,Institute Fisica Of Cantabria | Mendez F.J.,University of Cantabria
Climatic Change | Year: 2012

This paper analyzes changes of maximum temperatures in Europe, which are evaluated using two state-of-the-art regional climate models from the EU ENSEMBLES project. Extremes are expressed in terms of return values using a time-dependent generalized extreme value (GEV) model fitted to monthly maxima. Unlike the standard GEV method, this approach allows analyzing return periods at different time scales (monthly, seasonal, annual, etc). The study focuses on the end of the 20th century (1961-2000), used as a calibration/validation period, and assesses the changes projected for the period 2061-2100 considering the A1B emission scenario. The performance of the regional models is evaluated for each season of the calibration period against the high-resolution gridded E-OBS dataset, showing a similar South-North gradient with larger values over the Mediterranean basin. The inter-RCM changes in the bias pattern with respect to the E-OBS are larger than the bias resulting from a change in the boundary conditions from ERA-40 to ECHAM5 20c3m. The maximum temperature response to increased green house gases, as projected by the A1B scenario, is consistent for both RCMs. Under that scenario, results indicate that the increments for extremes (e. g. 40-year return values) will be two or three times higher than those for the mean seasonal temperatures, particularly during Spring and Summer in Southern Europe. © 2011 Springer Science+Business Media B.V.

Larger L.,University of Franche Comte | Soriano M.C.,University of the Balearic Islands | Brunner D.,University of the Balearic Islands | Appeltant L.,Vrije Universiteit Brussel | And 4 more authors.
Optics Express | Year: 2012

Many information processing challenges are difficult to solve with traditional Turing or von Neumann approaches. Implementing unconventional computational methods is therefore essential and optics provides promising opportunities. Here we experimentally demonstrate optical information processing using a nonlinear optoelectronic oscillator subject to delayed feedback. We implement a neuro-inspired concept, called Reservoir Computing, proven to possess universal computational capabilities. We particularly exploit the transient response of a complex dynamical system to an input data stream. We employ spoken digit recognition and time series prediction tasks as benchmarks, achieving competitive processing figures of merit. © 2012 Optical Society of America.

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