An assessment of the latent and sensible heat flux on the simulated regional climate over Southwestern South Atlantic Ocean     

Michelle Simões Reboita  Rosmeri Porfírio da Rocha  Tércio Ambrizzi  Ernesto Caetano 《Climate Dynamics》2010,34(6):873-889

A Regional Climate Model (RegCM3) 10-year (1990–1999) simulation over southwestern South Atlantic Ocean (SAO) is evaluated to assess the mean climatology and the simulation errors of turbulent fluxes over the sea. Moreover, the relationship between these fluxes and the rainfall over some cyclogenetic areas is also analyzed. The RegCM3 results are validated using some reanalyses datasets (ERA40, R2, GPCP and WHOI). The summer and winter spatial patterns of latent and sensible heat fluxes simulated by the RegCM3 are in agreement with the reanalyses (WHOI, R2 and ERA40). They show large latent heat fluxes exchange in the subtropical SAO and at higher latitudes in the warm waters of Brazil Current. In particular, the magnitude of RegCM3 latent heat fluxes is similar to the WHOI, which is probably related to two factors: (a) small specific humidity bias, and (b) the RegCM3 flux algorithm. In contrast, the RegCM3 presents large overestimation of sensible heat flux, though it simulates well their spatial pattern. This simulation error is associated with the RegCM3 underestimation of the 2-m air temperature. In southwestern SAO, in three known cyclogenetic areas, the reanalyses and the RegCM3 show the existence of different physical mechanisms that control the annual cycles of latent/sensible heating and rainfall. It is shown that over the eastern coast of Uruguay (35°–43°S) and the southeastern coast of Argentina (44°–52°S) the sea-air moisture and heat exchange play an important role to control the annual cycle of precipitation. This does not happen on the south/southeastern coast of Brazil.  相似文献   

Seawater density variations in the North Atlantic and the Atlantic meridional overturning circulation     

Chunzai Wang  Shenfu Dong  Ernesto Munoz 《Climate Dynamics》2010,34(7-8):953-968

Seawater property changes in the North Atlantic Ocean affect the Atlantic meridional overturning circulation (AMOC), which transports warm water northward from the upper ocean and contributes to the temperate climate of Europe, as well as influences climate globally. Previous observational studies have focused on salinity and freshwater variability in the sinking region of the North Atlantic, since it is believed that a freshening North Atlantic basin can slow down or halt the flow of the AMOC. Here we use available data to show the importance of how density patterns over the upper ocean of the North Atlantic affect the strength of the AMOC. For the long-term trend, the upper ocean of the subpolar North Atlantic is becoming cooler and fresher, whereas the subtropical North Atlantic is becoming warmer and saltier. On a multidecadal timescale, the upper ocean of the North Atlantic has generally been warmer and saltier since 1995. The heat and salt content in the subpolar North Atlantic lags that in the subtropical North Atlantic by about 8–9 years, suggesting a lower latitude origin for the temperature and salinity anomalies. Because of the opposite effects of temperature and salinity on density for both long-term trend and multidecadal timescales, these variations do not result in a density reduction in the subpolar North Atlantic for slowing down the AMOC. Indeed, the variations in the meridional density gradient between the subpolar and subtropical North Atlantic Ocean suggest that the AMOC has become stronger over the past five decades. These observed results are supported by and consistent with some oceanic reanalysis products.  相似文献   

Palaeomagnetic study of Permocarboniferous glacial varves from the Itarare Subgroup, southern Brazil     

A. M. Sinito  D. A. Valencio  M. Ernesto  I. G. Pacca 《Geophysical Journal International》1981,67(3):635-640

Summary. A sequence of 167 glacial varves from Itu, State of São Paulo (Brazil), has been sampled for palaeomagnetic analysis. Since the varve thicknesses permit individual measurements, an attempt was made to compare annual palaeomagnetic results with recent observatory data. Inclination and declination plots show larger variations than those displayed by the present geomagnetic field. This could, however, be due to sedimentation factors since it may be assumed that the pattern of the present geomagnetic field variations is not greatly different from that of the Permocarboniferous field. In the next paper (Ernesto & Pacca) the experimental data are submitted to spectral analysis and the results support some of the hypotheses raised in this work.  相似文献   

Strong-motion accelerograph array in Santiago,Chile, and preliminary evaluation of site effects     

Saburoh Midorikawa  Rafael Riddell  Ernesto Cruz 《地震工程与结构动力学》1991,20(5):403-407

A strong-motion accelerograph array in Santiago, Chile has been installed. One of the sites is located on rock and the other six sites are on soil ground with different surface geology, so that local site effects on ground motions can be studied. As a preliminary evaluation of the site effects, the spectral ratios of weak-motion records at soil sites with respect to the rock site are calculated. The spectral ratios show that the amplification of ground motions with respect to the rock site is approximately 1.25 on dense gravel deposits, 2.5 on stiff pumice ground and 3.5 on soft silt ground.  相似文献   

Line-of-sight and trans-horizon reception at Brébeuf college of two 1240 MHz rotating radars     

Ernesto Gherzi 《Pure and Applied Geophysics》1965,62(1):198-206

Summary The reception of pulses on about 1240 MHz from two rotating radars, one 80 miles, the other over 300 miles distant, is examined. A special periodic fading of the trans-horizon transmission is reported and discussed.  相似文献   

A new collector for sampling volcanic aerosols     

J. P. Toutain  F. Sortino  B. Reynier  B. Dupre  M. Munoz  A. Nonell  M. Polve  S. Chancha Do Vale 《Journal of Volcanology and Geothermal Research》2003,123(1-2):95

A new apparatus, Venturi Effect System (VES), designed for sampling volcanic plumes is described and tested at Vulcano (Italy). This device, together with purified basic NH₄OH solutions, supplies optimal conditions to obtain reliable S_total/Cl/F ratios and enrichment factors for metallic trace elements (MTE). Good concordance for acid gas ratios and metal enrichment factors in both the gas phase and the related plume allows the procedure to be validated. The VES appears in Vulcano conditions as a simple, robust and easily portable apparatus that allows reliable collection of both acid gases and MTE within a single sample and the analysis with current chemical methods (High Pressure Liquid Chromatography, Inductively Coupled Plasma–Mass Spectrometry). This apparatus may be suitable for more difficult volcanoes where only the plume can be sampled.  相似文献   

Fluid heterogeneities and hornblende stability in interlayered graphitic and nongraphitic schists (Tauern Window,Eastern Alps)     

Jane Selverstone  James L. Munoz 《Contributions to Mineralogy and Petrology》1987,96(4):426-440

The assemblage hornblende+white mica occurs in graphite-free schists at two localities in the southwest corner of the Tauern Window, Eastern Alps. In interbedded graphitic layers (1 mm to 1 m thick), however, hornblende is typically replaced by pseudomorphs of biotite+plagioclase +epidote±chlorite+staurolite in the presence of white mica. Garnets adjacent to these pseudomorphs have pronounced growth discontinuities near their rims, in contrast to the continuously zoned garnets in nongraphitic layers. These observations imply that reactions of the type hbl+white micagar+bio+plag+epid±chl±staur +H₂O occurred in the graphitic samples, but that hbl+white mica remained stable in graphite-free layers.Calculation of the equilibrium constants for solid phases in five dehydration equilibria at locality 1 indicates thata(H₂O) in the nongraphitic layers was 6 to 11 times greater thana(H₂O) in the graphitic layers. Similar calculations involving six dehydration equilibria at locality 2 show no difference ina(H₂O) between layers at the conditions of final equilibration. Initial differences in fluid composition maintained between the graphitic and nongraphitic layers caused the hbl+white mica reaction to occur at differentP-T conditions in different horizons of the schists.These data indicate that systematic differences in fluid composition were generated during metamorphism of the interlayered graphitic and non-graphitic schists but were subsequently homogenized at locality 2. The heterogeneities could initially have been produced while the rocks were in theP-T field of CO₂-H₂O immiscibility. Development of a penetrative, layer-parallel shear foliation at this time would have prevented subsequent mixing of the fluids across layers after temperatures exceeded the consolute temperature in the CO₂-H₂O system. Late-stage homogenization of fluids at locality 2 is thought to reflect loss of the buffer capacity of the mineral assemblage in response to total consumption of hornblende.  相似文献   

Modelling the Mixing Function to Constrain Coseismic Hydrochemical Effects: An Example from the French Pyrénées     

Jean-Paul Toutain  Margot Munoz  Jean-Louis Pinaud  Stéphanie Levet  Matthieu Sylvander  Alexis Rigo  Jocelyne Escalier 《Pure and Applied Geophysics》2006,163(4):723-744

Groundwater coseismic transient anomalies are evidenced and characterized by modelling the mixing function F characteristic of the groundwater dynamics in the Ogeu (western French Pyrénées) seismic context. Investigations of water-rock interactions at Ogeu indicate that these mineral waters from sedimentary environments result from the mixing of deep waters with evaporitic signature with surficial karstic waters. A 3-year hydrochemical monitoring of Ogeu springwater evidences that using arbitrary thresholds constituted by the mean ± 1 or 2σ, as often performed in such studies, is not a suitable approach to characterize transient anomalies. Instead, we have used a mixing function F calculated with chemical elements, which display a conservative behavior not controlled by the precipitation of a mineral phase. F is processed with seismic energy release (E_s) and effective rainfalls (R). Linear impulse responses of F to E_s and R have been calculated. Rapid responses (10 days) to rainwater inputs are evidenced, consisting in the recharge of the shallow karstic reservoir by fresh water. Complex impulse response of F to microseismic activity is also evidenced. It consists in a 2-phase hydrologic signal, with an inflow of saline water in the shallow reservoir with a response delay of 10 days, followed by an inflow of karstic water with a response delay of 70 days, the amount being higher than the saline inflow. Such a process probably results from changes in volumetric strain with subsequent microfracturation transient episodes allowing short inflow of deep salted water in the aquifer. This study demonstrates that groundwater systems in such environments are unstable systems that are highly sensitive to both rainfall inputs and microseismic activity. Impulse responses calculation of F to E_s is shown to be a powerful tool to identify transient anomalies. Similar processing is suggested to be potentially efficient to detect precursors of earthquakes when long time-series (5 years at least) are available in areas with high seismicity.  相似文献   

Driving processes and recognition criteria for complex subaerial unconformities in a non-marine succession: Implications for basin margin shaping during forced regressions     

Mariana S. Olivo  Ernesto Schwarz  Gonzalo D. Veiga 《Sedimentology》2020,67(5):2777-2817

A regional sedimentological and sequence stratigraphic analysis is presented in this paper to provide new insights into the morphological complexity and sedimentary mechanisms of unconformities giving shape to basin margins. Although the development of unconformities entails significant sediment delivery to be considered when analysing ‘source to sink’ systems, as well as large palaeogeographical changes related to basin reconfiguration episodes, the complexity that unconformities can reveal towards basin margins has been scarcely explored. A sedimentological and architectural analysis combining outcrop and subsurface datasets shows five palaeoenvironmental evolutionary stages and four key stratigraphic surfaces in a constrained ca 2 Ma Valanginian interval on the southern margin of the Neuquén back-arc basin (Argentina). A complex-type subaerial unconformity was identified, composed in turn of two subaerial unconformities exhibiting both single and composite motifs, different morphologies and facies shifts representative of large palaeogeographical changes. In the studied stratigraphic interval, two erosional stages occur linked to combinations of exclusively non-marine-driven processes involved in unconformities developing. The two subaerial unconformities differ in nature and distribution, representing a novel case of complex unconformities and stratigraphic architectures in non-marine lowstand wedges. The Valanginian complex subaerial unconformity entails a high diachroneity along strike and depositional dip, implying that the hiatus created in landward settings occurred during relative sea-level fall and rise stages during a period longer than in basinward areas. Disagreeing with classical sequential models, two third-order sequence components of a complex lowstand wedge are preserved in proximal settings. Subsidence-controlled accommodation and interplay between second-order and third-order cycles were combined, increasing the prospects of sediment storage and preservation potential of composite sequences towards landward areas. This work improves current comprehension about complex subaerial unconformities formation and related lowstand architectures in proximal settings, providing criteria to understand and revaluate lowstand wedge geometries, particularly for more complex examples, such as the case reported in this contribution.  相似文献   

On the Dynamics and Topology of the Elliptic Rectilinear Restricted 3-Body Problem     

Ernesto A. Lacomba  Jaume Llibre 《Celestial Mechanics and Dynamical Astronomy》2000,77(1):1-15

We study a symmetric collinear restricted 3-body problem, where the equal mass primaries perform elliptic collisions, while a third massless body moves in the line between the primaries, during the time between two consecutive elliptic collisions. After desingularizing binary and triple collisions, we prove the existence of a transversal heteroclinic orbit beginning and ending in triple collision. This orbit is the unique homothetic orbit that the problem possess. Finally, we describe the topology of the compact extended phase space. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献