Exercise in downscaling on sea surface temperature along Chinese coast   总被引：3，自引：0，他引：3  

王荣  孙松  孙松  王克  王克  李超伦 《中国海洋湖沼学报》2000,18(2):110-116

ＩＮＴＲＯＤＵＣＴＩＯＮＡｎｔａｒｃｔｉｃｋｒｉｌｌ(ＥｕｐｈａｕｓｉａｓｕｐｅｒｂａＤａｎａ)ｉｓａｋｅｙｏｒｇａｎｉｓｍｏｆｔｈｅＡｎｔａｒｃｔｉｃｍａｒｉｎｅｅｃｏｓｙｓｔｅｍａｎｄａｐｏｔｅｎｔｉａｌｆｉｓｈｅｒｙｒｅｓｏｕｒｃｅ.Ｉｔｈａｓｂｅｅｎｔｈｅｓｕｂｊｅｃｔｏｆｍｕｃｈｒｅｓｅａｒｃｈ.Ｄｅｓｐｉｔｅｔｈｅｌｏｎｇｈｉｓｔｏｒｙｏｆｒｅｓｅａｒｃｈｄａｔｉｎｇｂａｃｋｔｏｔｈｅ1930’ｓ,ｔｈｅｒｅａｒｅｓｔｉｌｌｑｕｅｓｔｉｏｎｓａｂｏｕｔｉｔｓｐｏｐｕｌａｔｉｏｎｓｔｒｕｃｔｕ…  相似文献   

Dating Gondwanan continental crust at the Rio Grande Rise,South Atlantic     

Roberto Ventura Santos  Carlos Eduardo Ganade  Christian M. Lacasse  Iago S. L. Costa  Ivo Pessanha  Eugenio P. Frazo  Elton L. Dantas  Jos A. Cavalcante 《地学学报》2019,31(5):424-429

Crystalline continental rocks and associated crust‐contaminated basaltic rocks were unexpectedly dredged on the crest and at seamounts of the Rio Grande Rise, South Atlantic. Zircon U–Pb ages of one gabbro (ca. 2,200 Ma) and four granitoids (between ca. 1,430–480 Ma) indicate that the breakup of SW Gondwana left behind continental fragments of dominantly African age. These rocks may have been incorporated into the oceanic lithosphere by complex processes including rifting and interaction of the Tristan‐Gough mantle plume with hyperextended continental margins. Until ca. 80–70 Ma, the Rio Grande Rise and an old portion of the Walvis Ridge formed a conjugate pair of aseismic ridges, and the Tristan‐Gough plume was positioned at the Mid‐Atlantic Ridge. The finding of continental rock fragments in one of these conjugate pairs opens new perspectives on the mechanisms of continental break‐up, the nature of this conjugate pair, and the geodynamic evolution of rifted Gondwana margins in the South Atlantic.  相似文献   

A transparent aqueous-saturated sand surrogate for use in physical modeling   总被引：3，自引：0，他引：3  

Ivan L. Guzman  Magued Iskander  Eduardo Suescun-Florez  Mehdi Omidvar 《Acta Geotechnica》2014,9(2):187-206

This paper presents the geotechnical properties of a new family of synthetic transparent soils made of fused quartz, saturated with a matched refractive index water-based sucrose solution, suitable for modeling the behavior of sand in small-scale model tests. The dry density ranged between 1,134 and 1,358 kg/m³. The peak angle of friction was found to range from 46° to 57°. The average hydraulic conductivity was 1.7 × 10^?5 cm/s. The compressibility index (C _c) ranged from 0.34 to 0.57. The main advantage of fused quartz over available sand surrogates made of silica gel is that its solid structure better models the behavior of natural sand. The matching pore fluids are inert and non-toxic, which facilitates their use in educational settings. The availability of a safe and easy-to-use transparent sand permits measurement of three-dimensional deformation patterns and flow characteristics in controlled research experiments. The introduction of an aqueous solution permits the use of two immiscible pore fluids, one made of mineral oil and the other made of a sucrose solution, for modeling multiphase flow problems, as well as coupled flow-deformation problems.  相似文献   

Subduction metamorphism of serpentinite‐hosted carbonates beyond antigorite‐serpentinite dehydration (Nevado‐Filábride Complex,Spain)     

Manuel D. Menzel  Carlos J. Garrido  Vicente Lpez Snchez‐Vizcaíno  Kroly Hidas  Claudio Marchesi 《Journal of Metamorphic Geology》2019,37(5):681-715

At sub‐arc depths, the release of carbon from subducting slab lithologies is mostly controlled by fluid released by devolatilization reactions such as dehydration of antigorite (Atg‐) serpentinite to prograde peridotite. Here we investigate carbonate–silicate rocks hosted in Atg‐serpentinite and prograde chlorite (Chl‐) harzburgite in the Milagrosa and Almirez ultramafic massifs of the palaeo‐subducted Nevado‐Filábride Complex (NFC, Betic Cordillera, S. Spain). These massifs provide a unique opportunity to study the stability of carbonate during subduction metamorphism at P–T conditions before and after the dehydration of Atg‐serpentinite in a warm subduction setting. In the Milagrosa massif, carbonate–silicate rocks occur as lenses of Ti‐clinohumite–diopside–calcite marbles, diopside–dolomite marbles and antigorite–diopside–dolomite rocks hosted in clinopyroxene‐bearing Atg‐serpentinite. In Almirez, carbonate–silicate rocks are hosted in Chl‐harzburgite and show a high‐grade assemblage composed of olivine, Ti‐clinohumite, diopside, chlorite, dolomite, calcite, Cr‐bearing magnetite, pentlandite and rare aragonite inclusions. These NFC carbonate–silicate rocks have variable CaO and CO₂ contents at nearly constant Mg/Si ratio and high Ni and Cr contents, indicating that their protoliths were variable mixtures of serpentine and Ca‐carbonate (i.e., ophicarbonates). Thermodynamic modelling shows that the carbonate–silicate rocks attained peak metamorphic conditions similar to those of their host serpentinite (Milagrosa massif; 550–600°C and 1.0–1.4 GPa) and Chl‐harzburgite (Almirez massif; 1.7–1.9 GPa and 680°C). Microstructures, mineral chemistry and phase relations indicate that the hybrid carbonate–silicate bulk rock compositions formed before prograde metamorphism, likely during seawater hydrothermal alteration, and subsequently underwent subduction metamorphism. In the CaO–MgO–SiO₂ ternary, these processes resulted in a compositional variability of NFC serpentinite‐hosted carbonate–silicate rocks along the serpentine‐calcite mixing trend, similar to that observed in serpentinite‐hosted carbonate‐rocks in other palaeo‐subducted metamorphic terranes. Thermodynamic modelling using classical models of binary H₂O–CO₂ fluids shows that the compositional variability along this binary determines the temperature of the main devolatilization reactions, the fluid composition and the mineral assemblages of reaction products during prograde subduction metamorphism. Thermodynamic modelling considering electrolytic fluids reveals that H₂O and molecular CO₂ are the main fluid species and charged carbon‐bearing species occur only in minor amounts in equilibrium with carbonate–silicate rocks in warm subduction settings. Consequently, accounting for electrolytic fluids at these conditions slightly increases the solubility of carbon in the fluids compared with predictions by classical binary H₂O–CO₂ fluids, but does not affect the topology of phase relations in serpentinite‐hosted carbonate‐rocks. Phase relations, mineral composition and assemblages of Milagrosa and Almirez (meta)‐serpentinite‐hosted carbonate–silicate rocks are consistent with local equilibrium between an infiltrating fluid and the bulk rock composition and indicate a limited role of infiltration‐driven decarbonation. Our study shows natural evidence for the preservation of carbonates in serpentinite‐hosted carbonate–silicate rocks beyond the Atg‐serpentinite breakdown at sub‐arc depths, demonstrating that carbon can be recycled into the deep mantle.  相似文献   

Tide-induced head fluctuations in coastal aquifers of variable thickness     

Julián Eduardo Cuello  Luis Guarracino 《水文研究》2020,34(21):4139-4146

In this work, a new analytical solution to describe tide-induced head fluctuations in aquifers of variable thickness is presented. The proposed model assumes a finite and confined aquifer with a thickness that increases or decreases quadratically with the distance to the coast. A closed-form analytical solution is obtained by solving a boundary-value problem with both a separation of variables method and a change of variables method. This solution is a generalization of the solution obtained by Cuello et al., Hydrogeological Journal, 2017, 25, 1509–1515. The analytical solution is expressed in terms of the wedging parameter, a parameter that depends on the length and thicknesses at the coast and at the inland edge of the aquifer. Positive values of the wedging parameter describe aquifers with increasing thickness towards land and negative values describe aquifers with a decreasing thickness in the inland direction. The comparison of the new solution and the solution for a finite aquifer with constant thickness indicates that the sign of the wedging parameter enhances or decreases the amplitude of the tide-induced signal. However, the differences in time-lag between both solutions are negligible near the coast. The slope factor, which quantifies the inconsistencies between aquifer diffusivities estimated from attenuation and time-lag data, is computed and analysed. Near the coast, slope factor values greater than one are obtained for negative wedging parameters while slope factor values less than one are obtained for positive wedging parameters. The analysis of the new solution also indicates that more reliable estimates of the hydraulic diffusivity can be obtained from time-lag data.  相似文献   

Petrology of pumices of April 1993 eruption of Lascar (Atacama, Chile)     

Bernard Déruelle  Oscar Figueroa A.  Eduardo Medina T.  Jose Viramonte G.  Mario Maragaño C. 《地学学报》1996,8(2):191-199

Lascar Volcano (Atacama, Chile) erupted on 18–20 April 1993. Several sub-Plinian explosions occurred, and some were mushroom-shaped. The highest column rose up to 23 km. Ash clouds crossed South America eastwards. Dacite pumice falls made of blocks and ashes were deposited on the flanks of the volcano as a result of collapsed columns. The pumice contains phenocrysts of plagioclase, enstatite, augite, biotite, magnetite and ilmenite and small crystals of apatite. The 1992 previous andesite dome inside the crater was destroyed. Banded blocks resulting from mingling of the dacitic pumice and andesite from the dome are found in the pumice flow. Both the lava dome and the pumice are representative of the Lascar high-K magma unit. Dacitic pumice is a product of crystal fractionation of the andesitic magma.  相似文献   

Statistical Study and Prediction of Variability of Erythemal Ultraviolet Irradiance Solar Values in Valencia,Spain     

Gonzalo Gurrea  Vicente Blanca-Giménez  Vicente Pérez  María-Antonia Serrano  Juan-Carlos Moreno  Solar Radiation Group of the Universitat Politècnica de València 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(4):599-610

The goal of this study was to statistically analyse the variability of global irradiance and ultraviolet erythemal (UVER) irradiance and their interrelationships with global and UVER irradiance, global clearness indices and ozone. A prediction of short-term UVER solar irradiance values was also obtained. Extreme values of UVER irradiance were included in the data set, as well as a time series of ultraviolet irradiance variability (UIV). The study period was from 2005 to 2014 and approximately 250,000 readings were taken at 5-min intervals. The effect of the clearness indices on global irradiance variability (GIV) and UIV was also recorded and bi-dimensional distributions were used to gather information on the two measured variables. With regard to daily GIV and UIV, it is also shown that for global clearness index (k_t) values lower than 0.6 both global and UVER irradiance had greater variability and that UIV on cloud-free days (k_t higher than 0.65) exceeds GIV. To study the dependence between UIV and GIV the χ² statistical method was used. It can be concluded that there is a 95% probability of a clear dependency between the variabilities. A connection between high k_t (corresponding to cloudless days) and low variabilities was found in the analysis of bi-dimensional distributions. Extreme values of UVER irradiance were also analyzed and it was possible to calculate the probable future values of UVER irradiance by extrapolating the values of the adjustment curve obtained from the Gumbel distribution.  相似文献   

Hydraulic response of a tidally forced coastal aquifer, Pontal do Paraná, Brazil     

D. S. Suresh Babu  Atul Kumar Sahai  Mauricio Almeida Noernberg  Eduardo Marone 《Hydrogeology Journal》2008,16(7):1427-1439

The unconfined aquifer supported by the extensive Holocene coastal plain of southern Brazil is found dissected at several places by tidally forced streams. One such unit of coastal plain, falling within the watershed limits of Perequê Stream in Paraná state, was analyzed using MODFLOW to assess the surface and subsurface water components under different stress conditions. The steady-state simulation suggests that ~23,000 m³/day of water forms the total budget of the designated aquifer zone and this zone discharges ~16,000 m³/day across the interface between the freshwater aquifer zone and the sea as direct submarine discharge. The maximum evaporation loss was assumed to be 2,700 m³/day. Any change in effective aquifer storage was insignificant, as there is no large-scale exploitation of local groundwater reserves. A calibration exercise, based on field measurements lasting 1 year, supports validity of the model considered. Simulations representing two different transient conditions point to the dynamic hydraulic response exhibited by the aquifer. A schematic map, showing directions and velocity of subsurface flows, and a three-dimensional model of the groundwater reserve helped to visualize the hydrogeologic changes and to formulate management plans.  相似文献   

Construction and assessment of a logistic regression model applied to short-term forecasting of thunderstorms in León (Spain)     

Jos Luis Snchez  Eduardo García Ortega  Jos Luis Marcos 《Atmospheric Research》2001,56(1-4)

Forecasting thunderstorms is one of the most difficult tasks in weather prediction due to the scarce knowledge on how to characterise the mechanisms taking part in the formation of thunderstorms. New tools based upon the objective recognition of appropriate conceptual models have been developed in the last years. A good example of this are the statistical models, based on variables that characterise the preconvective atmospheric conditions.This paper presents the results obtained by applying a short-term forecast model to thunderstorms during the summer periods in León (Spain). This model makes use of the logistic function as a binary forecasting technique determining storm/no storm. The logistic function used was a combination of 15 previously selected meteorological variables. The model has been constructed with the data collected on 152 occasions, and it has been verified on 77 other occasions.The skill scores obtained show that the use of statistical models combining the data, provided by variables characterizing the preconvective conditions and the triggering mechanisms, represent an important step in the difficult task of short-term thunderstorm forecasting.  相似文献   

The ichthyofauna and abiotic hydrological environment of the Ria de Aveiro,Portugal     

José Eduardo Rebelo 《Estuaries and Coasts》1992,15(3):403-413

The abiotic hydrological environment and the community dynamics of the fish fauna were investigated in the Ria de Aveiro, an estuarine coastal lagoon system (43 km²), which has both marine and fluvial influences. Abiotic hydrological and fish community parameters were recorded routinely during 12 months at ten stations. Temperature ranged between 9.5°C and 26.0°C, salinity between 0.0‰ and 32.0‰, dissolved oxygen between 0.8 mg 1^?1 and 15.4 mg 1^?1, pH between 6.1 and 9.4, and transparency between 4.4% and 100.0%. No significant differences were observed in temperature and dissolved oxygen among stations, or in seasonal variation in transparency. Nineteen thousand thirty-one fish specimens comprising 55 species were sampled. Abundance, biomass, and species richness were highest in summer and late winter at stations near the lagoon entrance. Sedentary species were most numerous, marine migratory species had the highest biomass, and the category “occasional species” had the highest number of species. Atherinidae, Mugilidae, and Gobiidae were the most important families. Eight species represented about 80% of the total fish abundance and biomass but only six species occurred in all the months and at all the stations. It was concluded that the Ria de Aveiro, with high seasonal and spatial abiotic variation, has a very rich and representative fish community compared with temperate and tropical estuaries and estuarine coastal lagoons around the world.  相似文献