Accuracy and sensitivity analysis for 54 models of computing hourly diffuse solar irradiation on clear sky     

Viorel Badescu  Christian A. Gueymard  Sorin Cheval  Cristian Oprea  Madalina Baciu  Alexandru Dumitrescu  Flavius Iacobescu  Ioan Milos  Costel Rada 《Theoretical and Applied Climatology》2013,111(3-4):379-399

Fifty-four broadband models for computation of solar diffuse irradiation on horizontal surface were tested in Romania (South-Eastern Europe). The input data consist of surface meteorological data, column integrated data, and data derived from satellite measurements. The testing procedure is performed in 21 stages intended to provide information about the sensitivity of the models to various sets of input data. There is no model to be ranked “the best” for all sets of input data. However, some of the models performed better than others, in the sense that they were ranked among the best for most of the testing stages. The best models for solar diffuse radiation computation are, on equal footing, ASHRAE 2005 model (ASHRAE 2005) and King model (King and Buckius, Solar Energy 22:297–301, 1979). The second best model is MAC model (Davies, Bound Layer Meteor 9:33–52, 1975). Details about the performance of each model in the 21 testing stages are found in the Electronic Supplementary Material.  相似文献   

Efficient methods for computing observation impact in 4D-Var data assimilation     

Alexandru Cioaca  Adrian Sandu  Eric de Sturler 《Computational Geosciences》2013,17(6):975-990

This paper presents a practical computational approach to quantify the effect of individual observations in estimating the state of a system. Such a methodology can be used for pruning redundant measurements and for designing future sensor networks. The mathematical approach is based on computing the sensitivity of the analyzed model states (unconstrained optimization solution) with respect to the data. The computational cost is dominated by the solution of a linear system, whose matrix is the Hessian of the cost function, and is only available in operator form. The right-hand side is the gradient of a scalar cost function that quantifies the forecast error of the numerical model. The use of adjoint models to obtain the necessary first- and second-order derivatives is discussed. We study various strategies to accelerate the computation, including matrix-free iterative solvers, preconditioners, and an in-house multigrid solver. Experiments are conducted on both a small-size shallow-water equations model and on a large-scale numerical weather prediction model, in order to illustrate the capabilities of the new methodology.  相似文献   

Waste rock dump investigation at Roşia Montană gold mine (Romania): a geostatistical approach   总被引：1，自引：1，他引：0  

Diego Servida  Sara Comero  Mara Dal Santo  Luisa de Capitani  Giovanni Grieco  Pietro Marescotti  Silvia Porro  Ferenc Lázár Forray  Ágnes Gál  Alexandru Szakács 《Environmental Earth Sciences》2013,70(1):13-31

Ro?ia Montan?, the largest European gold mine, could be re-opened. Environmental problems led to severe pollution of the Ro?ia and Abrud Rivers. The two main potentially toxic element (PTE) sources in mine sites are, in general, the abandoned underground workings and the piles of waste rock. Since the composition of waste rocks is often heterogeneous, this study faces the problem of estimating their mineralogical and chemical features starting from a set of sampling point. Twenty-five samples were collected on the main waste dump of the Ro?ia Montan? mine following a virtual squared grid (knots distance about 25 m). Grain size, color, bulk chemistry, mineralogy, acid mine drainage potential and a set of selected PTE (Ag, As, Cu, Ni, Pb and Zn) concentrations were determined on each sample. In a first approximation two main waste rock groups were identified: WR1 bulk composition is dacite-dominated, while WR2 is andesite-dominated. In both of them the concentrations of PTEs are below the regulatory limits for soils, with the exception of As. In terms of acid mine drainage, WR1 has a net acid-producing potential, while WR2 has a net neutralizing potential. The anisotropy of WR properties were analysed by means of semi-variograms and displayed with contour maps. Application of positive matrix factorization for the analysis of all the data relative to waste rocks allowed defining, in a semi-quantitative way, the factors controlling pollution and their spatial distribution. The processing of score matrix G factor associated with the geostatistical elaboration promises to be a powerful tool to discern the composition of mine dumps and support the exploitation and remediation phases.  相似文献   

Y Leonis: light curve solution revised and search for photometric variations of the primary minima     

Vlad Turcu  Alexandru Pop  Alexandru Marcu  Dan Moldovan 《Astrophysics and Space Science》2011,331(1):105-113

The interest in the study of the Algol binary system Y Leonis is justified not only by its light curve having a very deep primary minimum, and pulsating character of its primary component, but also by the complex behavior of its O–C curve which is featured by the presence of long and short time scale modulations. Taking into account the previously inferred K spectral type of the secondary component, one may expect that one of the involved periodicities could be related to magnetic cycles of this star. We gave the Wilson-Devinney solution of the eclipse light curve using our observational data obtained during 2009. The long- and short-term photometric variability of Y Leo is approached both through literature data and new CCD data. Even though these data are scarce, they revealed significant variability in the maximum and minimum brightness of this binary system at long time-scale. The nature of the rapid photometric variations during the deepest phase of primary minima can hardly be explained only by weak δ Scuti pulsations of the primary component which is still visible in partial eclipses.  相似文献   

The summer surface urban heat island of Bucharest (Romania) retrieved from MODIS images     

Sorin Cheval  Alexandru Dumitrescu 《Theoretical and Applied Climatology》2015,121(3-4):631-640

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Calculating snow-avalanche return period from tree-ring data     

Flaviu Meseșan  Ionela G. Gavrilă  Olimpiu T. Pop 《Natural Hazards》2018,94(3):1081-1098

The return period is a key element used for snow-avalanche characterization. To calculate the return period, historical data regarding past snow-avalanche activity are required. In mountain areas where past snow avalanches are poorly documented, dendrogeomorphic approaches constitute a reliable method for the reconstruction of past snow avalanches at the temporal scale of living trees. This paper presents an automated method for calculating the snow-avalanche return period using a digital elevation model and the location of the trees disturbed by every reconstructed snow-avalanche occurrence. Unlike the existing method, the method we propose requires neither the calculation of return period for every sampled tree nor the use of interpolation. This new method is based on the determination of spatial extent for every past snow-avalanche occurrence using the upslope area algorithm. The number of past snow-avalanche occurrences is calculated for every pixel of the path. The chronology length is divided by the number of past snow-avalanche occurrences to obtain the return period. In the present paper, both the proposed method and the existing method are applied to calculate the return period for three confined snow-avalanche paths located in Parâng Mountains, part of the Romanian Carpathians. Results are compared and discussed.  相似文献   

On the selection of GMPEs for Vrancea subcrustal seismic source   总被引：2，自引：0，他引：2  

Radu Vacareanu  Florin Pavel  Alexandru Aldea 《Bulletin of Earthquake Engineering》2013,11(6):1867-1884

The Vrancea subcrustal seismic source is characterized by large magnitude ( $M_{W} \ge 7$ ) intermediate-depth earthquakes that occur two or three times during a century on average. In this study several procedures are used to grade four candidate ground motion prediction equations proposed for Vrancea source in the SHARE project. In the work of Delavaud et al. (J Seismol 16(3):451–473, 2012) four ground motion prediction models developed for subduction zones (Zhao et al. in Bull Seism Soc Am 96(3):898–913, 2006; Atkinson and Boore in Bull Seism Soc Am 93(4):1703–1729, 2003; Youngs et al. in Seism Res Lett 68(1):58–73, 1997; Lin and Lee in Bull Seism Soc Am 98(1):220–240, 2008) are suggested as suitable for Vrancea subcrustal seismic source. The paper presents the appropriateness analysis of the four suggested ground motion prediction equations done using a dataset of 109 triaxial accelerograms recorded during seven Vrancea seismic events with moment magnitude $M_{W}$ between 5.4 and 7.4, occurred in the past 35 years. The strong ground motions were recorded in Romania, as well as in Bulgaria, Republic of Moldova and Serbia. Based on the ground motion dataset several goodness-of-fit measures are used in order to quantify how well the selected models match with the recorded data. The compatibility of the four ground motion prediction models with respect to magnitude scaling and distance scaling implied by strong ground motion dataset is investigated as well. The analyses show that the Youngs et al. (Seism Res Lett 68(1):58–73, 1997) and Zhao et al. (Bull Seism Soc Am 96(3):898–913, 2006) ground motion prediction models have a better fit with the data and can be candidate models for Probabilistic Seismic Hazard Assessment.  相似文献   

ROCADA: a gridded daily climatic dataset over Romania (1961–2013) for nine meteorological variables     

Alexandru Dumitrescu  Marius-Victor Birsan 《Natural Hazards》2015,78(2):1045-1063

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The study of binary systems with pulsating components using the frequency-modulation theory     

Alexandru Pop  Vlad Turcu 《Astrophysics and Space Science》1993,204(2):233-241

The effect of the orbital motion on the light curve of a pulsating star has been evaluated by means of the amplitude and phase spectra synthesis based on the instantaneous pulsation phase concept. The role of the binary system's geometry (circular or eccentric orbit) and the possibility of binarity diagnosis are also emphasized.  相似文献   

Publisher's announcement     

Alexandru Baltag  Lawrence Moss 《Surveys in Geophysics》1990,11(4):iii-iii

Publisher's announcement  相似文献