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Haszpra L.,Hungarian Meteorological Service | Haszpra L.,Geodetic and Geophysical Institute | Barcza Z.,Eötvös Loránd University | Barcza Z.,Institute of Ecology and Botany | And 3 more authors.
Atmospheric Measurement Techniques | Year: 2015

Planetary boundary layer (PBL) CO2 mole fraction data are needed by transport models and carbon budget models as both input and reference for validation. The height of in situ CO2 mole fraction measurements is usually different from that of the model levels where the data are needed; data from short towers, in particular, are difficult to utilize in atmospheric models that do not simulate the surface layer well. Tall-tower CO2 mole fraction measurements observed at heights ranging from 10 to 115 m above ground level at a rural site in Hungary and regular airborne vertical mole fraction profile measurements (136 vertical profiles) above the tower allowed us to estimate how well a tower of a given height could estimate the CO2 mole fraction above the tower in the PBL. The statistical evaluation of the height-dependent bias between the real PBL CO2 mole fraction profile (measured by the aircraft) and the measurement at a given elevation above the ground was performed separately for the summer and winter half years to take into account the different dynamics of the lower troposphere and the different surface CO2 flux in the different seasons. The paper presents (1) how accurately the vertical distribution of CO2 in the PBL can be estimated from the measurements on the top of a tower of height H; (2) how tall of a tower would be needed for the satisfaction of different requirements on the accuracy of the estimation of the CO2 vertical distribution; (3) how accurate of a CO2 vertical distribution estimation can be expected from the existing towers; and (4) how much improvement can be achieved in the accuracy of the estimation of CO2 vertical distribution by applying the virtual tall-tower concept. © 2015 Author(s).


Rakyta P.,Budapest University of Technology and Economics | Vigh M.,Eötvös Loránd University | Csordas A.,Eötvös Loránd University | Csordas A.,MTA ELTE Theoretical Physics Research Group | Cserti J.,Eötvös Loránd University
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

Silicene systems, due to the buckled structure of the lattice, manifest remarkable intrinsic spin-orbit interaction triggering a topological phase transition in the low-energy regime. Thus, we found that protected edge states are present in silicene antidots and dots, being polarized in valley-spin pairs. We have also studied the effect of the lattice termination on the properties of the single electron energy levels and electron density distribution of silicene antidots and dots situated in a perpendicular magnetic field. Our calculations confirmed that the topological edge states are propagating over the perimeter of the antidot/dot for both ideal or realistic edge termination containing roughness on the atomic length scale. The valley polarization and the slope of the energy lines as a function of the magnetic field is, however, reduced when the antidot or dot has a rough edge. © 2015 American Physical Society.


Galsa A.,Eötvös Loránd University | Herein M.,Eötvös Loránd University | Herein M.,MTA ELTE Theoretical Physics Research Group | Drahos D.,Eötvös Loránd University | Herein A.,Budapest University of Technology and Economics
Journal of Applied Geophysics | Year: 2016

Three-dimensional finite element numerical model calculations have been carried out to investigate the quantitative effect of the eccentric position of a normal resistivity borehole probe used in practice. Detailed calculations were done between the point-wise analytical solution and numerical solution to verify the results obtained from the finite element method for a normal probe with finite-length cylindrical electrodes. In the borehole the pattern of the current flowing out from current electrode A is efficiently influenced by the eccentricity. For high-resistivity rock the current density is decreased, while for low-resistivity rock it is increased toward the wall side. On the other hand, the eccentricity does not affect considerably the apparent resistivity calculated from electrode potentials. In most geological situations the deviation is less than 2%. However, in infrequent cases when the true resistivity of the rock is extremely low and/or the distance between the potential and current electrodes is very small the effect of the eccentricity can exceed even 10%. © 2016 Elsevier B.V.


Rakyta P.,Budapest University of Technology and Economics | Tovari E.,Budapest University of Technology and Economics | Csontos M.,Budapest University of Technology and Economics | Csonka S.,Budapest University of Technology and Economics | And 3 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

An experimental method for detection of bound states around an antidot formed by a hole in a graphene sheet is proposed via measuring the ballistic two-terminal conductance. In particular, we consider the effect of bound states formed by a magnetic field on the two-terminal conductance and show that one can observe Breit-Wigner-like resonances in the conductance as a function of the Fermi level close to the energies of the bound states. In addition, we develop a numerical method utilizing a reduced computational effort compared to the existing numerical recursive Green's function methods. © 2014 American Physical Society.


Haszpra T.,MTA ELTE Theoretical Physics Research Group | Horanyi A.,Hungarian Meteorological Service | Horanyi A.,European Center for Medium Range Weather Forecasts
Idojaras | Year: 2014

There are several types of uncertainties related to the simulation of the dispersion of pollutants in the atmosphere. For a dispersion forecast, one of the most important error sources is the meteorological data produced by a numerical weather prediction model and utilized bythe dispersion model. In this paper, we will present the results of an ensemble dispersion forecast created by using an ensemble meteorological forecast and the high-resolution forecast for 2.5 days. The dispersion simulations are carried out by the RePLaT Lagrangian dispersion model for particles of different radii. Significant deviations appear both in the extension and location of the ensemble of pollutant clouds consisting of particles of the same size. Differences appear also between the dispersion scenarios which use the unperturbed meteorological forecasts with different resolutions. The difference among the ensemble members increases for small particles. The area where at least one ensemblemember predicts pollutant is much larger than the area covered by the pollutant cloud of the high-resolution forecast. © 2014, Hungarian Meteorological Service. All rights reserved.


Palma G.,University of Santiago de Chile | Niedermayer F.,University of Bern | Racz Z.,MTA ELTE Theoretical Physics Research Group | Riveros A.,University of Santiago de Chile | Zambrano D.,Federico Santa María Technical University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016

The zero-temperature, classical XY model on an L×L square lattice is studied by exploring the distribution ΦL(y) of its centered and normalized magnetization y in the large-L limit. An integral representation of the cumulant generating function, known from earlier works, is used for the numerical evaluation of ΦL(y), and the limit distribution ΦL→∞(y)=Φ0(y) is obtained with high precision. The two leading finite-size corrections ΦL(y)-Φ0(y)≈a1(L)Φ1(y)+a2(L)Φ2(y) are also extracted both from numerics and from analytic calculations. We find that the amplitude a1(L) scales as ln(L/L0)/L2 and the shape correction function Φ1(y) can be expressed through the low-order derivatives of the limit distribution, Φ1(y)=[yΦ0(y)+Φ0′(y)]′. Thus, Φ1(y) carries the same universal features as the limit distribution and can be used for consistency checks of universality claims based on finite-size systems. The second finite-size correction has an amplitude a2(L)∝1/L2 and one finds that a2Φ2(y)a1Φ1(y) already for small system size (L>10). We illustrate the feasibility of observing the calculated finite-size corrections by performing simulations of the XY model at low temperatures, including T=0. © 2016 American Physical Society.


Drotos G.,Eötvös Loránd University | Drotos G.,MTA ELTE Theoretical Physics Research Group | Bodai T.,University of Hamburg | Tel T.,Eötvös Loránd University | Tel T.,MTA ELTE Theoretical Physics Research Group
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016

In nonautonomous dynamical systems, like in climate dynamics, an ensemble of trajectories initiated in the remote past defines a unique probability distribution, the natural measure of a snapshot attractor, for any instant of time, but this distribution typically changes in time. In cases with an aperiodic driving, temporal averages taken along a single trajectory would differ from the corresponding ensemble averages even in the infinite-time limit: ergodicity does not hold. It is worth considering this difference, which we call the nonergodic mismatch, by taking time windows of finite length for temporal averaging. We point out that the probability distribution of the nonergodic mismatch is qualitatively different in ergodic and nonergodic cases: its average is zero and typically nonzero, respectively. A main conclusion is that the difference of the average from zero, which we call the bias, is a useful measure of nonergodicity, for any window length. In contrast, the standard deviation of the nonergodic mismatch, which characterizes the spread between different realizations, exhibits a power-law decrease with increasing window length in both ergodic and nonergodic cases, and this implies that temporal and ensemble averages differ in dynamical systems with finite window lengths. It is the average modulus of the nonergodic mismatch, which we call the ergodicity deficit, that represents the expected deviation from fulfilling the equality of temporal and ensemble averages. As an important finding, we demonstrate that the ergodicity deficit cannot be reduced arbitrarily in nonergodic systems. We illustrate via a conceptual climate model that the nonergodic framework may be useful in Earth system dynamics, within which we propose the measure of nonergodicity, i.e., the bias, as an order-parameter-like quantifier of climate change. © 2016 American Physical Society.


PubMed | Federico Santa María Technical University, University of Bern, MTA ELTE Theoretical Physics Research Group and University of Santiago de Chile
Type: Journal Article | Journal: Physical review. E | Year: 2016

The zero-temperature, classical XY model on an LL square lattice is studied by exploring the distribution _{L}(y) of its centered and normalized magnetization y in the large-L limit. An integral representation of the cumulant generating function, known from earlier works, is used for the numerical evaluation of _{L}(y), and the limit distribution _{L}(y)=_{0}(y) is obtained with high precision. The two leading finite-size corrections _{L}(y)-_{0}(y)a_{1}(L)_{1}(y)+a_{2}(L)_{2}(y) are also extracted both from numerics and from analytic calculations. We find that the amplitude a_{1}(L) scales as ln(L/L_{0})/L^{2} and the shape correction function _{1}(y) can be expressed through the low-order derivatives of the limit distribution, _{1}(y)=[y_{0}(y)+_{0}^{}(y)]^{}. Thus, _{1}(y) carries the same universal features as the limit distribution and can be used for consistency checks of universality claims based on finite-size systems. The second finite-size correction has an amplitude a_{2}(L)1/L^{2} and one finds that a_{2}_{2}(y)a_{1}_{1}(y) already for small system size (L>10). We illustrate the feasibility of observing the calculated finite-size corrections by performing simulations of the XY model at low temperatures, including T=0.


Drotos G.,Eötvös Loránd University | Drotos G.,MTA ELTE Theoretical Physics Research Group | Jung C.,National Autonomous University of Mexico
Journal of Physics A: Mathematical and Theoretical | Year: 2016

The topic of this paper is hyperbolic chaotic scattering in a three degrees of freedom system. We generalize how shadows in the domain of the doubly differential cross-section are found: they are traced out by the appropriately filtered unstable manifolds of the periodic trajectories in the chaotic saddle. These shadows are related to the rainbow singularities in the doubly differential cross-section. As a result of this relation, we discover a method of how to recognize in the cross section a smoothly deformed image of the chaotic saddle, allowing the reconstruction of the symbolic dynamics of the chaotic saddle, its topology and its scaling factors. © 2016 IOP Publishing Ltd.


Haszpra T.,MTA ELTE Theoretical Physics Research Group
HARMO 2014 - 16th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Proceedings | Year: 2014

Lagrangian dispersion models are useful for simulating the trajectories of pollutants from single sources. A class of these models uses "real particles": particles with fixed, realistic size and density, and the particles are tracked individually. In the presentation we introduce the Real Particle Lagrangian Trajectory (RePLaT) dispersion model. As an extension to other real particle models, RePLaT takes into account the effect of turbulent diffusion and the scavenging of particles by precipitation. A novel feature of the model is the application of the impact of precipitation on individual particles by a random process which depends on precipitation intensity. Since RePLaT tracks realistic particles, it is also suitable for the investigation of the chaotic behavior in dispersion and deposition processes from a dynamical systems point of view. In order to validate RePLaT, we simulated the dispersion of volcanic ash from the Eyjafjallajökull eruptions and the dispersion and deposition of the radioactive particles released during the accident of the FUKushima Nuclear Power Plant. The results of the simulations indicate good agreement with satellite and surface measurements. © Crown Copyright 2014 Dstl.

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