Rapports entre la pluviosité et l’écoulement dans le Brésil subtropical et le Brésil tropical atlantique

Rochefort, Michel

doi:10.4000/books.iheal.7929

Cited by 5 publications

(4 citation statements)

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“…obtained mean values of 2400 m 3 s −1 between 1984 and 2002. Extreme discharge events of 25,000 and 16,000 m 3 s −1 were observed by Rocherfort [1958]. The influence of the South Atlantic anticyclone and polar origin anticyclones contributes to the high spatial variability of the wind circulation at synoptic time scales over the area.…”

Section: Physics and Sedimentologic Aspects Of The Study Regionmentioning

confidence: 91%

Dynamics of the Patos Lagoon coastal plume and its contribution to the deposition pattern of the southern Brazilian inner shelf

et al. 2010

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[1] The southern Brazilian shelf (SBS) is a region influenced by fresh water. The initial deposition of suspended sediments carried by this fresh water presents important ecological consequences for the area. The aim of this study was to investigate the contribution of the Patos Lagoon coastal plume to the deposition pattern observed along the inner continental shelf by providing estimates of estuarine-shelf suspended sediment exchange. The study was carried out through three-dimensional numeric modeling experiments on coupled hydrodynamic and morphodynamic processes. Results were analyzed using the dynamic method proposed by Garvine (1995) to study persistent plumes. The results were also analyzed using wavelet analysis. Results showed that the Patos Lagoon coastal plume behaves as a hypopycnal plume covering the first meters of the water column. The Patos Lagoon presents a dominant ebb condition with a mean discharge of 2088 m 3 s −1 and an exportation rate of suspended matter of approximately 1.3 × 10 7 t yr −1 . In the adjacent coastal region deposition prevails in sheltered regions up to 10 m deep, with enrichment in silt reaching up to 10% in the deceleration region of the Patos Lagoon coastal plume. The dynamic balance indicates a behavior typical of small to average-sized plumes, with a well-developed displacement along the coast that is mainly controlled by the alongshore wind component. The Coriolis force and bed shear stress present significant contributions during periods of moderate to high freshwater discharge when large-scale plumes are formed. Transversally to the coast the force balance is associated with the Coriolis effect and wind influence, with a less important contribution from bed shear stress. The inner continental shelf adjacent to the Patos Lagoon entrance is dominantly influenced by plume occurrence. In this region northeasterly winds induce the formation of southwestward currents near the coast. These currents deflect around jetties and generate recirculation zones to the south. The formation of a cyclonic eddy occurs in this area and creates convergence zones that intensify the vertical velocities promoting the deposition of suspended sediments.

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Section: Physics and Sedimentologic Aspects Of The Study Regionmentioning

confidence: 91%

Dynamics of the Patos Lagoon coastal plume and its contribution to the deposition pattern of the southern Brazilian inner shelf

et al. 2010

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“…[7] Extreme discharge events of 25,000 and 16,000 m 3 s −1 have been observed by Rocherfort [1958] during El Niño phenomena. Wind action is the most effective forcing on the Patos Lagoon circulation over synoptic timescales [Möller et al, 2001].…”

Section: Study Areamentioning

confidence: 99%

Straining and advection contributions to the mixing process in the Patos Lagoon estuary, Brazil

Marques¹,

Fernandes²,

Rocha³

2011

J. Geophys. Res.

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[1] The estuarine area of coastal lagoons and freshwater-influenced regions presents periodically stratified and destratified conditions. The Patos Lagoon, one of the most important hydrological resources in South America, is located in the southernmost part of Brazil and exhibits such variable conditions. Therefore the aim of this study was to investigate the contributions of straining and advection to the modulation of stratification conditions in the Patos Lagoon estuarine region using potential energy anomaly budgets. This study was based a three-dimensional hydrodynamic numerical model that provided information for the potential energy anomaly equation and wavelet analysis. Results from the potential energy anomaly time series revealed strong variability over a timescale of several days following local wind action and the river discharge pattern. Each part of the estuary exhibited contrasting regimes that were spatially distributed with a different balance of terms. The upper part was dominated by along-shore currents associated with east-west wind component and gravitational flux. Contribution from cross-shore advection became important in the middle part of the estuary, where there was an increase in superficial area observed. The lower region was controlled by the north-south wind component being influenced by advection, cross-shore straining, and transversal circulation, suggesting that current velocity maintained transversal pressure gradients and further circulation. Nonlinear interactions between deviations in the dispersion terms and vertical density and velocity were important everywhere but were associated with modulation effects.

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“…The freshwater provided by these rivers performs a pattern associated with regions of temperate climate, presenting variations in inter-annual timescales [19]. Extreme events of discharge of 25.000 e 16.000 m 3 •s −1 were observed by [19,20] respectively.…”

Section: Introductionmentioning

confidence: 99%

The Temporal Variability of the Freshwater Discharge and Water Levels at the Patos Lagoon, Brazil

Marques¹

2012

IJG

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The direct influence of freshwater discharge along the coastal regions is observed in several processes following a wide spectrum on spatial and temporal variability. The knowledge of relative importance of this physical forcing is fundamental by the correct management of the coastal sites and the understanding of consequences associated with processes of climatic order is one point deserves some investigation. The major part of the studies in the Patos Lagoon, located in the southernmost part of Brazil, is limited to investigate the effects in synoptic time scales. In this way, the objective of this study is to investigate the long term variability pattern of the Patos Lagoon discharge and water levels indentifying long term trends through wavelet analysis. The results indicated that El Niño (La Niña) events promote the intensification (decrease) of the freshwater intensity in the principal river tributaries of the Patos Lagoon following scales from 16 to 120 months (from 1.3 to 10 years). The most energetic cycle is centered in periods of 64 months (5.3 years). The longer events reflect the long term response of the non linear dynamics in Equatorial Pacific changing the precipitation pattern, principally during winter and at the end of spring and early autumn. The non-linear long term trend indicates a pattern with values of discharge normally above (below) the mean after (before) 1970’s. An increasing trend starting after 1970 possibly indicates a longer term cycle influencing the interannual variability of the Patos Lagoon discharge. The seasonality is maintained in climatic monthly means obtained after and before 1970’s, but, with mean increase around 364 m3·s?1 in freshwater discharge with reduced amplitude of the seasonal cycle

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Rapports entre la pluviosité et l’écoulement dans le Brésil subtropical et le Brésil tropical atlantique

Cited by 5 publications

References 0 publications

Dynamics of the Patos Lagoon coastal plume and its contribution to the deposition pattern of the southern Brazilian inner shelf

Dynamics of the Patos Lagoon coastal plume and its contribution to the deposition pattern of the southern Brazilian inner shelf

Straining and advection contributions to the mixing process in the Patos Lagoon estuary, Brazil

The Temporal Variability of the Freshwater Discharge and Water Levels at the Patos Lagoon, Brazil

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