Resumo em Espanhol:
Se efectuaron relevamientos gravimétricos areales que cubren la profunda cuenca intermontana de Ischigualasto-Villa Unión y que abarcan el norte de la Precordillera Andina y una importante porción de las Sierras Pampeanas Occidentales. A partir de los datos observados se prepararon cartas de anomalías de Bouguer (AB) y de anomalías de Bouguer afectadas por corrección geológica (ABcg). La cuenca se ubica en un ambiente tectónico complejo que contamina fuertemente el campo gravimétrico. El presente estudio apunta a interpretar la geometría 3D de la cuenca sedimentaria mediante análisis de los datos gravimétricos. La separación del efecto gravimétrico del depósito sedimentario es una tarea compleja que se resolvió empleando: i- el método de suavizado gráfico sobre la AB y ii- filtrados numéricos sobre la ABcg (AB corregida por los efectos sedimentarios de cuencas vecinas a la estudiada). Este análisis permite inferir que en el centro y norte de la cubeta las anomalías gravimétricas se deben, principalmente, al efecto del paquete sedimentario, mientras que en el sur de la misma, prevalecen efectos positivos en corteza debidos, muy probablemente, a intrusiones de rocas máficas. Por inversión gravimétrica de la anomalía residual se preparó un modelo gravimétrico, apoyado en datos sísmicos, que proporciona potencias sedimentarias de hasta 9 km en la región central de la cuenca.Resumo em Inglês:
Areal gravimetric surveys were carried out in the Ischigualasto-Villa Unión intermontane deep basin, the north of the Andean Precordillera, and in a wide portion of the western Sierras Pampeanas. Maps of Bouguer anomalies (AB) and Bouguer anomalies "affected by geological reduction" (ABcg) were derived from the observed data. The basin is located in a complex tectonic setting that strongly contaminates the gravity field. The present study aims to interpret the 3D geometry of the sedimentary basin through gravity data analysis. The separation of the gravimetric effect of the sedimentary filling is a complex task presently solved by employing: i- a graphical smoothing method from AB; and ii- numerical filterings from ABcg (AB corrected by the sedimentary filling effect of neighboring basins). This analysis permits to deduce that in the center and north of the basin the gravity anomalies should be mainly the result of the sedimentary filling effect, whereas in the south of the basin positive effects in the crust prevail due most likely to mafic intrusive rocks. A gravity model supported by seismic data that provides sedimentary thicknesses of up to 9 km in the central region of the basin was formulated by using gravimetric inversion of the residual anomaly.Resumo em Espanhol:
Se usa la serie incompleta de valores horarios de la foF2 sobre Concepción (36.8º S; 73.0º O), observados en el intervalo 1958 - 1989, para determinar inicialmente una serie completa de valores horarios de foF2 que pueden considerarse representativos de condiciones geomagnéticas quietas, pero que toma en cuenta las dependencias de la foF2 con la estación del año y con el nivel de actividad solar. Luego se propone un algoritmo para calcular valores horarios faltantes en el intervalo, en que sí se toma en cuenta el nivel de actividad geomagnética observado en las horas correspondientes, usando un índice de actividad geomagnética ponderado. Como evidentemente no se puede determinar la bondad del algoritmo propuesto para las horas en que no ha sido posible medir la foF2, se compara los valores horarios calculados con los observados, para días en que no hay ningún valor faltante, y que se consideran representativos de diferentes estaciones del año y niveles de actividad solar y geomagnética. Se encuentra que las diferencias no son significativas a excepción de días de equinoccio y verano en condiciones geomagnéticas muy perturbadas.Resumo em Inglês:
A complete series of hourly values of foF2 considered representative of geomagnetic quiet conditions is determined using the incomplete series of observed hourly values at Concepción (36.8º S; 73.0º W) in the 1 March 1958 - 1 July 1989 interval. This series takes into account known seasonal and solar activity level dependencies. Then a simple algorithm is proposed to calculate the missing hourly values of the original series, which takes into account the geomagnetic activity level for the corresponding hours, in terms of a weighted geomagnetic activity index. Since there is no way to assert the goodness of the proposed algorithm when there is no observed foF2 values, calculated and observed values are compared for a few days for which they do exist. Days considered representative of different seasons and levels of solar and geomagnetic activity are used. It is found that differences between calculated and observed values are not significant except for equinox and summer conditions at high geomagnetic activity level.Resumo em Português:
A energética dos distúrbios de alta freqüência é estudada por compostos dos sistemas ciclônicos. Os mapas compostos são construídos com dados filtrados da altura geopotencial em 1000 hPa para os dias em que a anomalia negativa no ponto base 70o W, 45o S estava abaixo de dois desvios padrões. Foram obtidos 61 compostos de sistemas ciclônicos. A distribuição espacial da energia potencial disponível dos distúrbios de alta freqüência é similar àquela obtida para os ciclones extratropicais do Hemisfério Norte. O ciclo de energia das anomalias filtradas com passa alta mostra que esses distúrbios crescem por conversões baroclínicas. Durante a fase de crescimento, fluxos de energia chegando na região e as fontes não conservativas são também importantes, embora a instabilidade barotrópica parece ter um papel importante sobre o oceano Pacífico durante essa fase. No estágio maduro, o distúrbio começa a decair barotropicamente e a energia radiativa é exportada para fora da região.Resumo em Inglês:
The energetics of the high frequency disturbances over South America are studied using composite maps of cyclone systems. The composite maps are constructed with filtered geopotential height data at 1000 hPa for the days when negative anomalies at the base grid point 70° W, 45° S exceeded two standard deviations below the mean. The cyclone system composite has 61 cases. The spatial distribution of the available potential energy of the high frequency disturbances is similar to what is seen for the Northern Hemisphere extratropical cyclones. The energy cycle of the high-pass filtered anomalies showed that these disturbances grow by baroclinic conversion. During the growing phase, energy fluxes coming into the region and nonconservative sources are also important, although barotropic instability seems to play some role over the Pacific Ocean. At the mature stage the disturbances showed barotropic decay and radiate energy out of the region.Resumo em Português:
A acurácia de dois algoritmos computacionais (códigos) simplificados para avaliação das componentes do balanço de radiação terrestre (radiação de onda longa), eficientes sob o ponto de vista computacional, é analisada a partir de comparações com cálculos de referência. Os dois códigos foram concebidos a partir de aproximações sobre a transferência de radiação de onda longa na atmosfera. O primeiro deles foi desenvolvido no Instituto Astronômico e Geofísico da Universidade de São Paulo (IAG-USP; São Paulo, SP), fornecendo irradiâncias ao longo da atmosfera a partir das radiâncias integradas sobre todo o espectro terrestre e previamente calculadas pela versão 7 do código de transferência radiativa Low Resolution Transmittance (LOWTRAN-7). O segundo código encontra-se incluído no modelo de circulação geral do Center for Ocean-Land-Atmosphere Studies (COLA; USA) e tem sido empregado no Centro de Previsão do Tempo e Estudos Climáticos do Instituto Nacional de Pesquisas Espaciais (CPTEC/INPE; Cachoeira Paulista, SP). Resultados obtidos com ambos os códigos são comparados com cálculos de referência efetuados respeitando-se a influência de milhares de linhas de absorção associadas aos três compostos moleculares mais relevantes à transferência de radiação de onda longa na atmosfera (vapor d’água, dióxido de carbono e ozônio). Todas as comparações foram efetuadas para condições atmosféricas hipotéticas, sugeridas no âmbito do programa ICRCCM (Intercomparison of Radiative Codes used in Climate Models). Os efeitos associados ao dióxido de carbono são bem reproduzidos pelo código CPTEC/COLA e, a menos de condições atmosféricas relativamente frias, também pelo código desenvolvido no IAG-USP. Os efeitos associados ao ozônio são subestimados por ambos os códigos mas sobretudo pelo CPTEC/COLA, que não inclui linhas de absorção situadas fora da região 980-1100 cm-1. Testes de sensibilidade realizados sobre os efeitos da absorção continuum associada ao vapor d’água mostram que estes efeitos podem ser bem avaliados desde que sejam consideradas as duas componentes desta absorção (self, dependente da pressão parcial do vapor d´água, e foreign, dependente da pressão do ar seco). Considerando-se condições atmosféricas hipotéticas contendo os três principais absorvedores moleculares, a irradiância descendente à superfície pode ser sistematicamente subestimada pelo código empregado no CPTEC/INPE. Estudos futuros devem avaliar a acurácia absoluta destes (e de outros) códigos, considerando a disponibilidade de medições da irradiância descendente à superfície mediante o emprego de pirgeômetros bem calibrados num sítio onde sejam efetuadas sondagens atmosféricas capazes de fornecer os perfis verticais de temperatura do ar e de concentração dos principais absorvedores.Resumo em Inglês:
The reliability of two computationally-efficient, simplified radiation codes employed to evaluate the components of the budget of terrestrial radiation is assessed from comparisons with benchmark calculations, performed with higher accuracy by reference codes. A number of approximations about the longwave radiative transfer in the atmosphere was assumed in the conception of both simplified codes. The first one was developed at the Instituto Astronômico e Geofísico da Universidade de São Paulo (Institute of Astronomy and Geophysics, University of São Paulo (IAG-USP; São Paulo, SP); it provides irradiances throughout the atmosphere from radiances integrated over the whole terrestrial spectrum and previously computed by running the version 7 of the Low Resolution Transmittance radiative transfer code (LOWTRAN-7). The second simplified code under consideration is included in the general circulation model developed at the Center for Ocean-Land-Atmosphere Studies (COLA; USA), which runs at the Centro de Previsão do Tempo e Estudos Climáticos (CPTEC; Cachoeira Paulista, SP) for numerical weather forecasting and climate studies. Benchmark calculations employed in this study were obtained by other groups through careful line-by-line spectral integration under hypothetical atmospheric conditions, prescribed in the scope of the program Intercomparison of Radiative Codes used in Climate Models (ICRCCM). Only the effects due to the emission / absorption by water vapor, carbon dioxide and ozone are analyzed. The effects due to the carbon dioxide are well reproduced by the code CPTEC/COLA and, excepting relatively cold atmospheric conditions, by the code developed at IAG-USP. The effects due to the ozone are underestimated by both simplified codes but mainly by the CPTEC/COLA, once the ozone bands situated outside the region 980-1100 cm-1 were neglected in its development. Sensitivity tests concerning the water vapor continuum absorption indicate that its both components ("self", related to the water vapor partial pressure, and "foreign", related to the dry air pressure) must be considered in order to obtain reliable water vapor absorption estimates. Under hypothetical atmospheric conditions and assuming the occurrence of the three main molecular absorbers, downward longwave irradiances at the surface can be systematically underestimated by the code CPTEC/COLA. Future studies must include not only comparisons between results provided by simplified radiation codes and the respective benchmark calculations under many atmospheric profiles obtained from soundings, but also comparisons between these results and measurements obtained with pyrgeometers near the sounding site.Resumo em Inglês:
Geomagnetic Deep Sounding (GDS) is an electromagnetic method of geophysics, which is capable of imaging the Earth’s interior in terms of electrical conductivity using natural geomagnetic transient variations. The method is particularly suited to map geological structures marked by large lateral conductivity contrasts. An overview of the methodology is presented for a magnetometer array study undertaken within and around the intracratonic Parnaíba Basin, north-northeast Brazil. The article describes the sequential steps of data processing, the results of numerical modeling, and the related geological/tectonic implications of the inferred conductivity distribution. In the initial stages of data processing, an advanced robust regression technique is applied to derive transfer functions used to diagnose the lateral conductivity distribution in the study region. The presentation of the transfer functions in the form of induction arrows helps to identify regions of enhanced conductivity. Contour plots and pseudo-sections of the anomalous vertical fields, estimated from the hypothetical event analysis on transfer functions, are essential to characterize the orientation and dimensionality of the electrical conductive structures of the region. The analysis of various frequency and polarization parameters indicates that an anomalous behavior of the magnetovariational field, with periods longer than one hour, is determined by currents induced in the seawater, and perhaps in the raised asthenosphere beneath the oceanic region. Yet, anomalous signatures observed at periods shorter than one hour are primarily controlled by concentrated currents in two inland conductive structures. They are the Parnaíba Basin Conductivity Anomaly (PBCA), that follows the trend of the Transbrasiliano Lineament in the eastern part of the Parnaíba Basin, and the LINK anomaly, that extends from the central part of the basin to the Marajó Graben. A non-uniform thin sheet modeling has mapped the lateral extent and estimated the depth-integrated conductances of PBCA and LINK to be of the order of 2000 S and 1000 S, respectively. The overall pattern of the inferred conductivity distribution helps to visualize the LINK anomaly as relics of a probable sedimentary channel connecting the Parnaíba Basin and Marajó Graben, and which could have acted as a gateway for sea transgressions during early stages of the basin evolution. The combined inversion and forward modeling of the GDS response functions provides the PBCA structural cross-section as an ensemble of a graben-like structure in the basement and a highly conducting block confined to the deeper central part of the basin, with an embedded resistive body in the middle. The existence of a broad conducting block confined to the central part of the basin is also consistent with magnetotelluric data, and the graben-like structure in the basement is corroborated by aeromagnetic data. The origin of graben-like structures in the basement could be possibly related to an extensional tectonism, whereas the resistive body is tentatively interpreted as a diabase dike or a recrystallized magmatic body intruded during a Cretaceous magmatic event. Carbon bearing sediments are suggested as an alternative to hydrated siliciclastic sediments to account for the high conductivity of the central block. A hydrothermal event associated with the Cretaceous magmatic activity may be the likely process to produce carbon through the pyrolysis of hydrocarbon-saturated Paleozoic sediments.Resumo em Português:
Neste trabalho foram encontradas duas características para a identificação da advecção de ar quente: a curvatura anticiclônica da massa de nuvens e a presença de uma quantidade maior de nuvens Cirrus na fronteira desta massa. Estes resultados foram obtidos através da análise integrada de dados de satélites e de dados sinóticos convencionais. As nuvens observadas localizavam-se na periferia norte e noroeste do anticiclone, no cavado de um ciclone, ou no campo de pressão baixa e difusa que, geralmente, é apresentado como sendo uma linha de instabilidade nas cartas sinóticas. Em algumas situações, forma-se um ciclone, em outras, ocorre o processo de frontogênese ou a regeneração de um ciclone velho. Os dados de satélite permitiram a identificação e determinação das regiões com advecção de ar quente com uma antecedência de 24 a 48 horas em relação ao dados sinóticos.Resumo em Inglês:
The paper presents a study of cloudiness having the typical structure: the anticyclone curvature of the cloud’s mass and a large quantity of cirrus clouds on the cloudiness’ border. The integrated analysis of conventional and satellite data has shown that this cloudiness structure is observed in synoptic situations of warm air advection. This cloudiness was localized in the northerly and northwesterly periphery of the anticyclone, in the trough of the cyclone, or in the diffuse pressure field, generally presented as lines of instability in synoptic maps. Sometimes, as a result of the warm advection, it is observed frontogenesis, cyclogenesis or the regeneration of the old cyclone. The satellite data enables the discrimination of warm air advection regions earlier (24-48 h) than the synoptic maps.Resumo em Inglês:
The United Nations Convention on the Law of the Sea (UNCLOS) - also known as "The Law of the Sea" - defines the important concepts of territorial sea, exclusive economic zone, and continental shelf. Although these terms apply to distinct regions of the sea, there are many misunderstandings and confusion in using the correct name when referring to a particular portion of the ocean. We intend to give the reader some insights about these names and their correct use