Neural network based daily precipitation generator (NNGEN-P)   总被引：1，自引：0，他引：1  

Jean-Philippe Boulanger  Fernando Martinez  Olga Penalba  Enrique Carlos Segura 《Climate Dynamics》2007,28(2-3):307-324

Daily weather generators are used in many applications and risk analyses. The present paper explores the potential of neural network architectures to design daily weather generator models. Focusing this first paper on precipitation, we design a collection of neural networks (multi-layer perceptrons in the present case), which are trained so as to approximate the empirical cumulative distribution (CDF) function for the occurrence of wet and dry spells and for the precipitation amounts. This approach contributes to correct some of the biases of the usual two-step weather generator models. As compared to a rainfall occurrence Markov model, NNGEN-P represents fairly well the mean and standard deviation of the number of wet days per month, and it significantly improves the simulation of the longest dry and wet periods. Then, we compared NNGEN-P to three parametric distribution functions usually applied to fit rainfall cumulative distribution functions (Gamma, Weibull and double-exponential). A data set of 19 Argentine stations was used. Also, data corresponding to stations in the United States, in Europe and in the Tropics were included to confirm the results. One of the advantages of NNGEN-P is that it is non-parametric. Unlike other parametric function, which adapt to certain types of climate regimes, NNGEN-P is fully adaptive to the observed cumulative distribution functions, which, on some occasions, may present complex shapes. On-going works will soon produce an extended version of NNGEN to temperature and radiation.  相似文献   

Spatial Analysis of Airborne Geophysical Data Applied to Geological Mapping and Mineral Prospecting in the Serra Leste Region, Carajás Mineral Province, Brazil     

Carlos Roberto de Souza Filho  Alfredo Rossetto Nunes  Emilson Pereira Leite  Lena Virgínia Soares Monteiro  Roberto Perez Xavier 《Surveys in Geophysics》2007,28(5-6):377-405

The Serra Leste region, located in the northeast portion of Carajás Mineral Province (PA), hosts important chrome-PGE, Au–Pd–Pt, Cu–Mo–Au, iron, and manganese deposits and occurrences related to different geological settings. We present a regional prospective model with focus on PGE mineralizations based on airborne geophysics (magnetometry, gamma-ray spectrometry and time domain electromagnetometry) and geological data. Geological and geophysics data analysis indicate a plausible correspondence between areas with meta-mafic–ultramafic rocks and low values in gamma spectrometry, mainly for the thorium channel. The meta-ultramafic units of the complexes, the main host rock of the PGE mineralization, are well defined by analytic signal from the anomalous magnetic field and by the apparent conductance anomalies derived from the GEOTEM system. The combination of the derivative products with updated geological data of the Serra Leste region and PGE-Luanga deposit enable to establish a regional prospective model for PGE and the identification of new targets within the studied area.  相似文献   

Ages and metallicities of five intermediate-age star clusters projected towards the Small Magellanic Cloud     

Andrés E. Piatti  João F. C. SantosJr  Juan J. Clariá  Eduardo Bica  Ata Sarajedini  Doug Geisler 《Monthly notices of the Royal Astronomical Society》2001,325(2):792-802

Colour–magnitude diagrams are presented for the first time for L32, L38, K28 (L43), K44 (L68) and L116, which are clusters projected on to the outer parts of the Small Magellanic Cloud (SMC). The photometry was carried out in the Washington system C and T ₁ filters, allowing the determination of ages by means of the magnitude difference between the red giant clump and the main-sequence turn-off, and metallicities from the red giant branch locus. The clusters have ages in the range 2–6 Gyr , and metallicities in the range −1.65<[Fe/H]<−1.10, increasing the sample of intermediate-age clusters in the SMC. L116, the outermost cluster projected on to the SMC, is a foreground cluster, and somewhat closer to us than the Large Magellanic Cloud. Our results, combined with those for other clusters in the literature, show epochs of sudden chemical enrichment in the age–metallicity plane, which favour a bursting star formation history as opposed to a continuous one for the SMC.  相似文献   

Analysis of karst hydrodynamics through comparison of dissolved and suspended solids' transport     

Danièle Valdes  Jean-Paul Dupont  Nicolas Massei  Benoît Laignel  Joël Rodet 《Comptes Rendus Geoscience》2005,337(15):1365-1374

In karst systems, rain events often result in a decrease of the conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. This study shows that the comparison of suspended solids and solute transport by the coupled approach of $T\text{–}C$ curves (Turbidity–Conductivity) and autocorrelations gives evidence of the transport processes in the karst network and allows understanding the karst hydrodynamics. To cite this article: D. Valdes et al., C. R. Geoscience 337 (2005).  相似文献   

Cyanobacterial blooms in estuarine ecosystems: characteristics and effects on Laeonereis acuta (Polychaeta, Nereididae)     

da Rosa CE  de Souza MS  Yunes JS  Proença LA  Nery LE  Monserrat JM 《Marine pollution bulletin》2005,50(9):956-964

In January of 2003, a cyanobacterial bloom in the Patos' Lagoon (Southern Brazil) (32 degrees 05'S-52 degrees 12'W) was observed. Water samples were taken to identify the composition and abundance of the bloom, as well as the occurrence of toxins. The effects of this occurrence on the estuarine worm Laeonereis acuta (Polychaeta, Nereididae) was also evaluated. Predominance of cyanobacteria, particularly Anabaena trichomes ( approximately 2.5.10(6) individuals per liter) was observed, and low concentrations of microcystins and anticholinesterasic toxins were detected. Augmented levels of lipid hydroperoxides (LPO) and glutathione-S-transferase activity, and lowering of total protein content were also observed in organisms collected during the bloom event. Although non-toxic, the cyanobacterial bloom could augment the cycle of hyper-oxygenation and hypoxia in the water. During hyperoxia, L. acuta, an oxyconformer, should consume more oxygen, thus augmenting the rate of reactive oxygen species generation. A repeated cycle of hyper-oxygenation and hypoxia would finally induce oxidative stress, as evidenced by the high levels of LPO and glutathione-S-transferase activity.  相似文献   

Hydrothermal alteration and fluid inclusion study of the Lower Cretaceous porphyry Cu–Au deposit of Tiámaro, Michoacán, Mexico     

Carlos Garza-Gonzlez  Antoni Camprubí  Eduardo Gonzlez-Partida  Germn Arriaga-García  Fernando Rosique-Naranjo 《Journal of Geochemical Exploration》2006,89(1-3):124

The Tiámaro deposit in Michoacán state has been dated as Lower Cretaceous (Valanginian), though most of the porphyry deposits in central Mexico were dated or have an attributed Eocene–Oligocene age. The host rocks belong to a volcanoplutonic complex overlain by red conglomerates. These rocks were intruded by pre-Valanginian plutonic and hypabissal rocks. Propylitic, phyllic, and argillic alteration assemblages developed, and their superimposition draws the evolution of the deposit. Stage I is represented by propylitic assemblages, stage II contains the main ore forming stockworks and both phyllic and argillic assemblages, and stage III contains late carbonatization assemblages. The obtained temperatures and salinities from inclusion fluids are low for a porphyry-type deposit, but we interpret that the known part of the deposit represents the shallow portion of a bigger deposit. The evolution of mineralizing fluids draws a dilution trend of brines from “porphyry-like” to “epithermal-like” stages. The richest ore zone is roughly located between the 300 and 350 °C isotherms, though unnoticed resources may occur at depth.  相似文献   

Eutrophication processes and trophic interactions in a shallow estuary: Preliminary results based on stable isotope analysis (δ13C and δ15N)     

Paulo Cesar Abreu  César S. B. Costa  Carlos Bemvenuti  Clarisse Odebrecht  Wilhelm Graneli  Alexandre M. Anesio 《Estuaries and Coasts》2006,29(2):277-285

Stable isotopes ratios (δ¹³C and δ¹⁵N) were measured in primary producers and consumers of two bays with contrasting eutrophic conditions in the Patos Lagoon estuary, southern Brazil: the Justino bay, a more pristine ecosystem, and the Mangueira bay, a heavily polluted region that receives the Rio Grande city sewage and effluencts of several industries. δ¹³C values of organisms collected in both subsystems were not different, but δ¹⁵N values had significant statistical differences, ca. 3.5‰ higher in the Mangueira bay. It is likely that primary producers and consumers in this subsystem are greatly influenced by higher nitrogen input due to domestic and industrial sewages. The stable isotope analysis also corroborated several trophic interactions previously established by gut content analysis, and due to its higher sensitivity, it was possible to better determine the contributions of different primary producers and detrital fractions to the consumers' diets. It was confirmed that plant detritus represents the main food source for most organisms. The stable isotope analysis also demonstrated that detritivorous benthic organisms in the same habitat have distinct diet compositions, with differential consumption of C3 and C4 plants. This technique showed that some consumers that eat detritus do not have in their stable isotopic signature any relationship with that of plants. It is likely that these consumers assimilate their carbon and nitrogen from other sources like microalgae or microorganisms that colonize decaying plants.  相似文献   

Pollution au plomb dans la Savoie antique (II–IIIe s. apr. J.-C.) en relation avec une installation métallurgique de la cité de Vienne     

Fabien Arnaud  Joël Serralongue  Thierry Winiarski  Marc Desmet  Martine Paterne 《Comptes Rendus Geoscience》2006,338(4):244-252

In Lake Anterne (NW French Alps), the Roman period is characterised by a lead contamination more important than that of the 1970s, due to the use of leaded gasoline. The maximum of this contamination period has been varve-dated 220 AD, i.e., during the optimum of Roman civilization in the Alps. Crossing palaeoenvironmental and archaeological evidences points out the economic importance of the town of Passy for the City of Vienne and yields a new example of lead contamination due to local metallurgical activity rather than distant impact of the exploitation of the Spanish Rio Tinto mine. To cite this article: F. Arnaud et al., C. R. Geoscience 338 (2005).  相似文献   

The 2dF Galaxy Redshift Survey: the power spectrum and the matter content of the Universe     

Will J. Percival  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Stephen Moody  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,327(4):1297-1306

The 2dF Galaxy Redshift Survey has now measured in excess of 160 000 galaxy redshifts. This paper presents the power spectrum of the galaxy distribution, calculated using a direct Fourier transform based technique. We argue that, within the k -space region     , the shape of this spectrum should be close to that of the linear density perturbations convolved with the window function of the survey. This window function and its convolving effect on the power spectrum estimate are analysed in detail. By convolving model spectra, we are able to fit the power-spectrum data and provide a measure of the matter content of the Universe. Our results show that models containing baryon oscillations are mildly preferred over featureless power spectra. Analysis of the data yields 68 per cent confidence limits on the total matter density times the Hubble parameter     , and the baryon fraction     , assuming scale-invariant primordial fluctuations.  相似文献   

Selection of quasar candidates from combined radio and optical surveys using neural networks     

R. Carballo  A. S. Cofiño  J. I. González-Serrano 《Monthly notices of the Royal Astronomical Society》2004,353(1):211-220

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