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排序方式: 共有250条查询结果,搜索用时 140 毫秒
91.
José Tasso Felix Guimarães Marcelo Cancela Lisboa Cohen Marlon Carlos França Luiz Carlos Ruiz Pessenda Eduardo de Jesus Souza Afonso César Rodrigues Nogueira Ronnie Alves 《地球表面变化过程与地形》2013,38(13):1535-1549
The goal of this work was to understand the main hydrodynamic processes acting on tidal flats of the coast of Amapá near the mouth of the Amazon River, and how they change over the short term (~ 20 years). The analysis of morphological and geobotanical units was carried out by applying processing and interpretation methods to optical and synthetic aperture radar (SAR) images, combined with data on water salinity, maximum flood height, sedimentary facies data, rainfall and river discharge. The temporal analysis of morphological and geobotanical units suggests the relative stabilization of savannah, ‘várzea’ and mangrove areas during the drier period and increasing tidal amplitude between 1987 to 1997. The wetter period and decreasing tidal amplitude between 1997 to 2008 led to an increase in the area of ‘várzea’ and lakes over savannah, and the expansion of mangroves mainly over the inundated field and tidal mud/mixed flats. Therefore, the decrease in rainfall index during the drier period is well‐correlated with the reduction of the Calçoene River discharge and jointly with increasing tidal amplitude favored the increase of migration rate of the mud bank and erosion profile along the littoral. It was followed by the increase of the Calçoene River discharge and jointly with decreasing tidal amplitude during the wetter period, favoring the development of mangroves on muddy substrates near the coastline. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
92.
In tide-dominated environments, residual circulation is the comparatively weak net flow in addition to the oscillatory tidal current. Understanding the 3D structure of this circulation is of importance for coastal management as it impacts the net (longer term and event-scale) transport of suspended particles and the advection of tracer quantities. The Dee Estuary, northwest Britain, is used to understand which physical processes have an important contribution to the time-varying residual circulation. Model simulations are used to extract the time-varying contributions of tidal, riverine (baroclinicity and discharge), meteorological, external and wave processes, along with their interactions. Under hypertidal conditions, strong semi-diurnal interaction within the residual makes it difficult to clearly see the effect of a process without filtering. An approach to separate the residual into the isolated process contribution and the contribution due to interaction is described. Applying this method to two hypertidal estuarine channels, one tide dominant and one baroclinic dominant, reveals that process interaction can be as important as the sub-tidal residual process contributions themselves. The time variation of the residual circulation highlights the impact of different physical process components at the event scale of tidal conditions (neap and spring cycles) and offshore storms (wind, wave and surge influence). This gives insight into short-term deviation from the typical estuarine residual. Both channels are found to react differently to the same local conditions, with different short-term change in process dominance during events of high and low energy. 相似文献
93.
Reinaldo A. Petta Sven Sindern Raquel F. Souza Thomas F. C. Campos 《Environmental Earth Sciences》2014,72(6):1843-1852
The study area is one of the most important mineral provinces of the Rio Grande do Norte State (NE Brazil), which has been extensively exploited since 1940. This article presents a geochemical investigation of stream sediments taken in the drainage system between the Brejuí and Barra Verde scheelite mines, and the Gargalheiras municipal reservoir, in Acari city. In addition to the major elements, the trace elements V, Cr, Co, Ni, Cu, Zn, As, Rb, Sr, Zr, Mo, Sn, Ba, W were analyzed and compared to metal levels reported in the literature for the same area. The elements W, Mo, Cu, Sn and in part Zn are enriched in sediments of rivulets forming the drainage system close to the mining district. This is due to emission from uncovered mine waste dumps. Dispersion of elements is controlled by both, aeolian as well as fluvial transport. The concentration of Cu in stream sediments close to the mines reaches toxic levels. At the mouth of the drainage system to the reservoir, the elements W and Mo are still enriched in the stream sediments relative to the geogenic background by factors of 15 and 11, respectively. This indicates the probable influence of mining activity to the reservoir sediments, and mobilization of W and Mo in the reservoir water cannot be ruled out. 相似文献
94.
Amaral Genilda Canuto Pezzopane José Eduardo Macedo de Souza Nóia Júnior Rogério Martínez Manuel Fernández Fonseca Mariana Duarte Silva Gibson Elbya Leão Toledo João Vitor Pezzopane José Ricardo Macedo Klippel Valéria Hollunder Xavier Talita Miranda Teixeira 《Theoretical and Applied Climatology》2022,147(1-2):347-361
Theoretical and Applied Climatology - The climate change endangers many species of the Amazon Forest. An example, in the endangered medicinal species Pilocarpus microphyllus (popularly known as... 相似文献
95.
de Souza Luciana Sandra Bastos Silva Maiara Tatiane Lima Alba Elisiane de Moura Magna Soelma Beserra da Cruz Neto José Francisco de Souza Carlos André Alves da Silva Thieres George Freire 《Theoretical and Applied Climatology》2022,149(1-2):593-602
Theoretical and Applied Climatology - Analysing alternative methods for estimating reference evapotranspiration (ET0) is essential for improving the management of water resources, especially where... 相似文献
96.
Otávio Cristiano Montanher Evlyn Márcia Leão de Morais Novo Edvard Elias de Souza Filho 《水文科学杂志》2013,58(13-14):1901-1912
ABSTRACTWe discuss the claim that the Amazon River has been subjected to a noticeable increase in suspended sediment transport (SST) in response to both climate and land-use changes. To study this, both satellite imagery and in situ data were compiled to produce a 32-year time series (1984–2016) of suspended sediment concentration. Both parametric and nonparametric statistics were applied to examine the SST time trend. The results indicate that there has been no statistically significant increase in SST in the last 32 years, independent of the statistical approach. The results indicate that, over the last 32 years at the Óbidos station, in Brazil, a recurring pattern of increase and decrease in SST has occurred, rather than a unidirectional systematic trend. This further explains the increasing trend reported in the literature and indicates that short time series are not recommended for time trend analyses due to the large inter-annual variability. 相似文献
97.
Michael James Friedel Oderson Ant?nio de Souza Filho Fabio Iwashita Adalene Moreira Silva Sueli Yoshinaga 《Hydrogeology Journal》2012,20(6):1061-1080
It is not possible, using numerical methods, to model groundwater flow and transport in the fractured crystalline rock of northeastern Brazil. As an alternative, the usefulness of self-organizing map (SOM), k-means clustering, and Davies-Bouldin techniques to conceptualize the hydrogeology was evaluated. Also estimated was the well yield and groundwater quality across the Juá region. This process relies on relations in the underlying multivariate density function associated with a sparse local set of hydrogeologic (electrical conductivity, geology, temperature, and well yield) and a complete regional set of airborne geophysical (electromagnetic, magnetic, and radiometric) and satellite spectrometric measurements. Resampling of the regional well yield and electrical conductivity estimates provides sufficient resolution to construct variograms for stochastic modeling of the hydrogeologic variables. The combination of these stochastic maps provides a way to identify potential drilling targets for future groundwater development. The data-driven estimation approach, when applied to available airborne electromagnetic and water-well hydrogeologic measurements, provides a low-cost alternative to numerical groundwater flow modeling. In addition to fractured rock environments, the alternative modeling framework can provide spatial parameter estimates and associated variograms for constraints to improve the traditional calibration of equivalent groundwater-porous-media models. 相似文献
98.
Landslide prediction is complex and involves many factors, such as geotechnical, geological, topographical, and even meteorological.
This work presents a methodology by using a Data Mining approach in order to predict landslide occurrences induced by rainfall in Rio de Janeiro city. Landslide and rain data records
from 1998 to 2001 were obtained from field technical reports and 30 automatic rain gauges, respectively. It was also collected
data regarding soil parameters, including urban areas, forest, vulnerability, among others, and totalizing 46 soil variables.
All the information was inserted into a Geographic Information Systems. Clustering (Dendrogram and k-means) and Statistical (Principal Component Analysis and Correlation) techniques were used to regionalize the rain data and select the rain gauges to be input on Artificial Neural Networks , which were used to replace the missing rain values. The landslide volume variable also presented missing values and it
was completed by the k-Nearest Neighbor method. After data preparation, some models were built to predict landslide and rainfall using Data Mining techniques. The obtained model’s performance is also analyzed. 相似文献
99.
Vinicius Aguiar de Souza Levent Kirkayak Katsuyuki Suzuki Hideyuki Ando Hidetoshi Sueoka 《Ocean Engineering》2012
This paper describes an approach to simulate a seven-tier stack consisting of scaled model of a 20 ft ISO freight container and its linking connectors, denominated twist locks, subjected to dynamical load induced by its base. The physical (dimensions, mass, and moments of inertia) and structural (longitudinal, transversal and torsional stiffness) characteristics of the scaled models were decided based on two dimensionless numbers: ratios between gravity force and inertia force, and elastic force divided by inertia force, through experimental and numerical analysis. A series of experiments with controlled parameters were performed using a shaking table test to understand the effects of each variable in the container stack dynamics and present enough data to validate the numerical model. The results of this study indicate that the numerical model built is a promising tool for further study. Moreover, the model is able to predict conditions close to real situations faced by container stacks while storage on a ship's deck. 相似文献
100.
Nivaor Rodolfo Rigozo Cláudio Sergio Lisi Mário Tomazello Filho Alan Prestes Daniel Jean Roger Nordemann Mariza Pereira de Souza Echer Ezequiel Echer Heitor Evangelista da Silva Valderez F. Rigozo 《Pure and Applied Geophysics》2012,169(12):2181-2191
This work investigates the behavior of the sunspot number and Southern Oscillation Index (SOI) signal recorded in the tree ring time series for three different locations in Brazil: Humaitá in Amaz?nia State, Porto Ferreira in S?o Paulo State, and Passo Fundo in Rio Grande do Sul State, using wavelet and cross-wavelet analysis techniques. The wavelet spectra of tree ring time series showed signs of 11 and 22?years, possibly related to the solar activity, and periods of 2–8?years, possibly related to El Ni?o events. The cross-wavelet spectra for all tree ring time series from Brazil present a significant response to the 11-year solar cycle in the time interval between 1921 to after 1981. These tree ring time series still have a response to the second harmonic of the solar cycle (5.5?years), but in different time intervals. The cross-wavelet maps also showed that the relationship between the SOI x tree ring time series is more intense, for oscillation in the range of 4–8?years. 相似文献