Synthetic aperture radar (SAR) images acquired by the First and Second European Remote Sensing Satellite (ERS1/2) over coastal waters near estuaries often show sea surface signatures of river outflow fronts. In particular, the analysis of several SAR images showing the Rhine outflow region indicates that the outflow front is visible as a line of high radar backscatter. Location and form of the outflow front depend strongly on tidal phase and Rhine discharge. In order to simulate the dynamics of the Rhine plume in the outflow region, a two-layer, nonlinear numerical model based on the hydrostatic shallow water equation has been developed. Due to a numerical technique for moveable lateral boundaries, the model allows for the simulation of localized layers with an outcropping interface (front). The model is forced by imposing tidal and residual transport and river discharge at the open boundaries. The evolution of the Rhine plume as calculated by the numerical model is discussed with respect to tidal phase and Rhine discharge. Using a simple radar backscatter model relating the surface velocity convergence and shear to the relative radar backscatter, it is shown that the observed signatures of the Rhine outflow front can be explained by the variation of the surface velocity convergence and shear as calculated by the numerical model.

The Rhine outflow studied by the analysis of ERS1/2 SAR data and numerical simulations

RUBINO, Angelo;
1997

Abstract

Synthetic aperture radar (SAR) images acquired by the First and Second European Remote Sensing Satellite (ERS1/2) over coastal waters near estuaries often show sea surface signatures of river outflow fronts. In particular, the analysis of several SAR images showing the Rhine outflow region indicates that the outflow front is visible as a line of high radar backscatter. Location and form of the outflow front depend strongly on tidal phase and Rhine discharge. In order to simulate the dynamics of the Rhine plume in the outflow region, a two-layer, nonlinear numerical model based on the hydrostatic shallow water equation has been developed. Due to a numerical technique for moveable lateral boundaries, the model allows for the simulation of localized layers with an outcropping interface (front). The model is forced by imposing tidal and residual transport and river discharge at the open boundaries. The evolution of the Rhine plume as calculated by the numerical model is discussed with respect to tidal phase and Rhine discharge. Using a simple radar backscatter model relating the surface velocity convergence and shear to the relative radar backscatter, it is shown that the observed signatures of the Rhine outflow front can be explained by the variation of the surface velocity convergence and shear as calculated by the numerical model.
Proceedings of the 3rd ERS Symposium, Florence, Italy, 14-21 March
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10278/33033
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