Contributions of Atlantic tropical cyclones to monthly and seasonal rainfall in the eastern United States 1960�C2007     

Ricardo C. Nogueira  Barry D. Keim 《Theoretical and Applied Climatology》2011,103(1-2):213-227

Tropical cyclone activity in the North Atlantic Basin experiences great variability on intra-annual, interannual, and interdecadal timescales. George Cry found that TC rainfall presents an intra-seasonal pattern over the eastern USA, contributing up to 40% of total monthly rainfall. This study replicates much of what was done by Cry using a denser rain gauge network and more sophisticated techniques for analysis. Rainfall data for this study come from 717 stations from the Historical Climate Network covering 31 states to capture the tropical cyclone (TC) contribution in monthly and seasonal precipitation in the eastern USA. Results showed that September has the highest TC rainfall contribution and the coastal regions of North Carolina, Virginia, and Alabama receive more than 30% of monthly rainfall totals from TCs. Comparisons between 1931?C1960 and 1960?C2007 study periods show that the storm track density shifted slightly eastward, which explains some of differences between the two analyses.  相似文献   

Climate change in the Paraná state,Brazil: responses to increasing atmospheric CO 2 in reference evapotranspiration     

Lucas da Costa Santos  Jefferson Vieira Jos&#;  Fabiani Denise Bender  Daniel Soares Alves  Pablo Ricardo Nitsche  Elton Fialho dos Reis  Rubens Duarte Coelho 《Theoretical and Applied Climatology》2020,140(1):55-68

The hydrological variable evapotranspiration (ET) is challenging to estimate because it cannot be measured directly in natural environments (except in small plots). The uncertainties associated with the models used for its prediction have increased under climate change conditions. We studied the influence of stomatal resistance on ET estimates using the Penman-Monteith method as projected by three general circulation models in two emission scenarios (RCP4.5 and RCP8.5) for future climates throughout the twenty-first century (2010–2039, 2040–2069, and 2070–2099). We also investigated the probable ET rate changes in relation to the current (30 years average, 1980–2009) climate conditions for the Paraná state in the southern region of Brazil. The results were regionalized to help policymakers assess climate change impacts and design adaptation measures. ET increases of up to 15% were found in future climate conditions, which may lead to a significant increase in the water demand for agricultural crops. However, we believe that plant morphophysiological changes may occur under atmospheric CO2 enrichment conditions and that a possible reduction in stomatal conductance will result in lower ET increases than those obtained with the traditional Penman-Monteith method. When considering future climate scenarios, we propose the equation be adjusted to consider stomatal resistance as a function of CO2 concentrations.  相似文献   

Post-depositional tectonic modification of VMS deposits in Iberia and its economic significance     

Ricardo Castroviejo  Cecilio Quesada  Miguel Soler 《Mineralium Deposita》2011,46(5-6):615-637

The original stratigraphic relationships and structure of VMS deposits are commonly obscured by deformation. This can also affect their economic significance, as shown by several Iberian Pyrite Belt (IPB, SW Iberia) examples. The contrasting rheologic properties of the different lithologies present in an orebody (massive sulphide, feeder stockwork, alteration envelope, volcanic and sedimentary rocks) play a major role in determining its overall behaviour. Variscan thin-skinned tectonics led to stacking of the massive pyrite and stockwork bodies in duplex structures, resulting in local thickening and increased tonnage of minable mineralization. Furthermore, differential mechanical behaviour of the different sulphide minerals localised the detachments along relatively ductile sulphide-rich bands. The result was a geochemical and mineralogical reorganisation of most deposits, which now consist of barren, massive pyrite horses, bounded by base metal-rich ductile shear zones. Metal redistribution was enhanced by mobilisation of the base metal sulphides from the initially impoverished massive pyrite, through pressure-solution processes, to tensional fissures within the already ductile shear zones. In NW Iberia, VMS deposits were also strongly overprinted by the Variscan deformation during emplacement of the Cabo Ortegal and órdenes allochthonous nappe complexes, but no stacking of the orebodies was produced. Original contacts were transposed, and the orebodies, their feeder zones and the country rock acquired pronounced laminar geometry. In lower-grade rocks (greenschist facies, Cabo Ortegal Complex), solution transfer mechanisms are common in pyrite, which remains in the brittle domain, while chalcopyrite shows ductile behaviour. In higher-grade rocks (amphibolite facies, órdenes Complex), metamorphic recrystallisation overprints earlier deformation textures. The contrasting behaviour of the IPB and NW Iberian deposits is explained by key factors that affect their final geometry, composition and economics, such as pre-deformation structure, size and mineralogical composition of the orebody and associated lithologies, temperature, crustal level, deviatoric stress and availability of a fluid phase during deformation and the style and rate of deformation.  相似文献   

Accretion of Grenvillian terranes to the southwestern border of the R��o de la Plata craton, western Argentina     

Ricardo Varela  Miguel A. S. Basei  Pablo D. Gonz��lez  Ana M. Sato  Maximiliano Naipauer  Mario Campos Neto  Carlos A. Cingolani  Vinicius T. Meira 《International Journal of Earth Sciences》2011,100(2-3):243-272

A comprehensive review of the geological, geochronological, and isotopic features of the Mesoproterozoic Grenvillian terranes attached to the southwest of the Río de la Plata craton in Early Paleozoic times is presented in this paper. They are grouped into the northern (sierras de Umango, Maz and del Espinal and surroundings), central (Sierra de Pie de Palo, southern Precordillera and Frontal Cordillera), and southern (San Rafael and Las Matras Blocks) segments. The Mesoproterozoic basement consists mainly of arc related, intermediate to acidic and mafic?Cultramafic rocks of 1,244?C1,027?Ma, with juvenile, Laurentian affinity. Exception to it is the Maz Group, with a protracted history and reworked character. They are affected by 846?C570?Ma, extensional magmatism in the northern and central segments, which represents the Neoproterozoic breakup of the Rodinia supercontinent. Successive passive margin sedimentation is registered in Late Neoproterozoic (~640?C580?Ma) and Cambro-Ordovician (~550?C470?Ma) times. The southern segment is noted for the younger sedimentation alone, and for showing the exclusive primary unconformable relationship between the Mesoproterozoic basement and Early Ordovician cover. The effects of Early Paleozoic Famatinian orogeny, associated with the collisions of Cuyania and Chilenia terranes, are recorded as main phase (480?C450?Ma), late phase (440?C420?Ma), and Chanic phase (400?C360?Ma). Among them, the tectonothermal climax is the Ordovician main phase, to which klippe and nappe structures typical of collisional orogens are related in the northern and central segments. Preliminary data allow us to suggest a set of paired metamorphic belts, with an outboard high-P/T belt, and an inboard Barrowian P/T belt.  相似文献   

GIS-based mapping for marine geohazards in seabed fluid leakage areas (Gulf of Cadiz, Spain)     

Ricardo Le??n  Luis Somoza 《Marine Geophysical Researches》2011,32(1-2):207-223

This paper applies, for the first time in offshore deepwater, a method based on geographic information systems for seafloor susceptibility assessment as a first approach to marine geohazard mapping in fluid leakage areas (slope instabilities, gas escapes, seabed collapses, pockmarks, etc.). The assessment was carried out in a known seabed fluid-flow province located on the Iberian margin of the Gulf of C??diz, Spain. The method (based on statistical bivariate analysis) creates a susceptibility map that defines the likelihood of occurrence of seafloor features related to fluid flow: crater-like depressions and submarine landslides. It is based on the statistical index (Wi) method (Van Westen in Statistical landslide hazard analysis. ILWIS 2.1 for Windows application guide. ITC Publication, Enschede, pp 73?C84, 1997), in which Wi is a function of the cartographic density of seafloor features on ??factor maps??. The factors selected monitor the seafloor??s capability to store and transfer hydrocarbon gases and gravitational instability triggers: geology-lithology, gas hydrate stability zone thickness (temperature, pressure?Cwater depth and geothermal gradient), occurrence of diapirs, proximity to faults or lineaments, and slope angle of the seafloor. Results show that the occurrence of seafloor features related to fluid flow is highest where the factors ??gas source and storage?? and ??pathways of fluid escape?? converge. This means that they are particularly abundant over diapirs in contourite deposits, in the vicinity of faults, and inside theoretical gas hydrate stability fields thinned by warm undercurrents. Furthermore, the submarine landslides located on the Palaeozoic-Toarcian basement are not related to fluid leakage. This methodology provides helpful information for hazard mitigation in regional selection of potential drill sites, deep-water construction sites or pipeline routes. It is an easily applied and useful tool for taking the first step in risk assessment on a regional scale for vast areas where fluid leakage may be present, the geological model is known, and the geologically hazardous features have already been mapped.  相似文献   

Turbiditic levee deposition in response to climate changes: The Var Sedimentary Ridge (Ligurian Sea)     

Stéphan J. Jorry  Isabelle Jégou  Laurent Emmanuel  Ricardo Silva Jacinto  Bruno Savoye 《Marine Geology》2011,279(1-4):148-161

The Var turbiditic system located in the Ligurian Sea (SE France) is an intermediate mud/sand-rich system. The particularity of the Var deep-sea fan is its single channel with abrupt bends and its asymmetric and hyper-developed levee on the right hand side: the Var Sedimentary Ridge. Long-term sediment accumulation on the Var Sedimentary Ridge makes this an ideal target for studying the link between onshore climate change and deep-sea turbidite stratigraphy. This paper focuses on the establishment of the first detailed stratigraphy of the levee, which is used to analyze the timing of overbank deposition throughout the last deglaciation. Main results indicate that high variability in turbidite frequencies and deposition rates along the Var Sedimentary Ridge are determined by two main parameters: 1) the progressive decrease of the levee height controlling the ability of turbidity currents to spill out from the channel onto the levee, and 2) climatic variations affecting the drainage basin, in particular changes in glacial condition since late Last Glacial Maximum to early Holocene. Compared to other deep-water areas, this study confirms the ability of turbiditic systems to record past climatic events on millennial timescales, and underlines the influence of European deglaciation on the observed decrease in turbidite activity in the Var canyon. The presence of a very narrow continental shelf and a single, large channel-levee system makes the Var Sedimentary Ridge a unique example of climate-controlled turbiditic accumulations.  相似文献   

Association announcement     

Ricardo A. Olea 《Mathematical Geosciences》1995,27(3):463-466

  相似文献   

Tree-ring and glacial evidence for the medieval warm epoch and the little ice age in southern South America   总被引：3，自引：0，他引：3  

Ricardo Villalba 《Climatic change》1994,26(2-3):183-197

A tree-ring reconstruction of summer temperatures from northern Patagonia shows distinct episodes of higher and lower temperature during the last 1000 yr. The first cold interval was from A.D. 900 to 1070, which was followed by a warm period A.D. 1080 to 1250 (approximately coincident with theMedieval Warm Epoch). Afterwards a long, cold-moist interval followed from A.D. 1270 to 1660, peaking around 1340 and 1640 (contemporaneously with earlyLittle Ice Age events in the Northern Hemisphere). In central Chile, winter rainfall variations were reconstructed using tree rings back to the year A.D. 1220. From A.D. 1220 to 1280, and from A.D. 1450 to 1550, rainfall was above the long-term mean. Droughts apparently occurred between A.D. 1280 and 1450, from 1570 to 1650, and from 1770 to 1820. In northern Patagonia, radiocarbon dates and tree-ring dates record two major glacial advances in the A.D. 1270–1380 and 1520–1670 intervals. In southern Patagonia, the initiation of theLittle Ice Age appears to have been around A.D. 1300, and the culmination of glacial advances between the late 17th to the early 19th centuries.Most of the reconstructed winter-dry periods in central Chile are synchronous with cold summers in northern Patagonia, resembling the present regional patterns associated with the El Niño-Southern Oscillation (ENSO). The years A.D. 1468–69 represent, in both temperature and precipitation reconstructions from treerings, the largest departures during the last 1000 yr. A very strong ENSO event was probably responsible for these extreme deviations. Tree-ring analysis also indicates that the association between a weaker southeastern Pacific subtropical anticyclone and the occurence of El Niño events has been stable over the last four centuries, although some anomalous cases are recognized.  相似文献   

Turbulent Structure of a Simplified Urban Fluid Flow Studied Through Stereoscopic Particle Image Velocimetry     

Bruno Monnier  Sepehr A. Goudarzi  Ricardo Vinuesa  Candace Wark 《Boundary-Layer Meteorology》2018,166(2):239-268

Stereoscopic particle image velocimetry was used to provide a three-dimensional characterization of the flow around a simplified urban model defined by a 5 by 7 array of blocks, forming four parallel streets, perpendicular to the incoming wind direction corresponding to a zero angle of incidence. Channeling of the flow through the array under consideration was observed, and its effect increased as the incoming wind direction, or angle of incidence (AOI), was changed from \(0^{\circ }\) to \(15^{\circ }\), \(30^{\circ }\), and \(45^{\circ }\). The flow between blocks can be divided into two regions: a region of low turbulence kinetic energy (TKE) levels close to the leeward side of the upstream block, and a high TKE area close to the downstream block. The centre of the arch vortex is located in the low TKE area, and two regions of large streamwise velocity fluctuation bound the vortex in the spanwise direction. Moreover, a region of large spanwise velocity fluctuation on the downstream block is found between the vortex legs. Our results indicate that the reorientation of the arch vortex at increasing AOI is produced by the displacement of the different TKE regions and their interaction with the shear layers on the sides and top of the upstream and downstream blocks, respectively. There is also a close connection between the turbulent structure between the blocks and the wind gusts. The correlations among gust components were also studied, and it was found that in the near-wall region of the street the correlations between the streamwise and spanwise gusts \(R_{uv}\) were dominant for all four AOI cases. At higher wall-normal positions in the array, the \(R_{uw}\) correlation decreased with increasing AOI, whereas the \(R_{uv}\) coefficient increased as AOI increased, and at \({\textit{AOI}}=45^{\circ }\) all three correlations exhibited relatively high values of around 0.4.  相似文献   

A Chart for Judging Optimal Sample Spacing for Ore Grade Estimation     

Vanessa Cerqueira Koppe  Ricardo Hundelshaussen Rubio  João Felipe Coimbra Leite Costa 《Natural Resources Research》2017,26(2):191-199

Mineral deposit grades are usually estimated using data from samples of rock cores extracted from drill holes. Commonly, mineral deposit grade estimates are required for each block to be mined. Every estimated grade has always a corresponding error when compared against real grades of blocks. The error depends on various factors, among which the most important is the number of correlated samples used for estimation. Samples may be collected on a regular sampling grid and, as the spacing between samples decreases, the error of grade estimated from the data generally decreases. Sampling can be expensive. The maximum distance between samples that provides an acceptable error of grade estimate is useful for deciding how many samples are adequate. The error also depends on the geometry of a block, as lower errors would be expected when estimating the grade of large-volume blocks, and on the variability of the data within the region of the blocks. Local variability is measured in this study using the coefficient of variation (CV). We show charts analyzing error in block grade estimates as a function of sampling grid (obtained by geostatistical simulation), for various block dimensions (volumes) and for a given CV interval. These charts show results for two different attributes (Au and Ni) of two different deposits. The results show that similar errors were found for the two deposits, although they share similar features: sampling grid, block volume, CV, and continuity model. Consequently, the error for other attributes with similar features could be obtained from a single chart.  相似文献