Data/hora: 10/06/2024 12:00:35

Provedor de dados: | Institutional Archive of Ifreme (ArchiMer)
País: | France
Título: | The influence of quasi resonant internal waves on the radar imaging mechanism of shallow sea bottom topography
Autores: | Hennings, I; Metzner, M; De Loor, Gp.
Data: | 2002-03
Ano: | 2002
Palavras-chave: | Mécanisme des images radar; Topographie des fond marins; Stratification; Ondes internes; Radar imaging mechanism; Sea bottom topography; Stratification internal wave; Strain rate.
Resumo: | During previous field experiments in the North Sea it was often assumed that the water column in such shallow coastal tidal waters is vertically well mixed and stratification was neglected when discussing the Normalized Radar Cross Section modulation caused by the sea floor. In this paper the influence of quasi resonant internal waves with the sea bed on the radar imaging mechanism of submarine sand waves itself is investigated. In situ data of the tidal cur-rent velocity and several water quality parameters such as sea surface temperature, fluorescence. and beam transmittance were measured in the Southern Bight of the North Sea in April 1991. Simulations of the total NRCS modulation caused by sand waves and internal waves as a function of the current gradient or strain rate induced by the internal wave current field at the sea surface have been carried out using the quasi-steady approximation and linear internal wave theory. As a first approximation the strain rate depending on stratification was calculated using the two-layer model. These simulations demonstrate that at least a density difference between the two layers of the order of Delta(Q) approximate to 1 kg m(-3) is necessary for a sinusoidal thermocline to effect the total NRCS modulation considerably. The NRCS modulation as a function of wind friction velocity has been calculated independently and is discussed with regard to the strain rate of the surface current field caused by the superimposed imaging mechanisms of sand waves and internal waves. It turned out that the existence of a surface roughness-wind stress feedback mechanism cannot be excluded. (C) 2002 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS. All rights reserved.
Tipo: | Text
Idioma: | Inglês

Identificador:

http://archimer.ifremer.fr/doc/00322/43322/42932.pdf

DOI:10.1016/S0399-1784(02)01186-6

http://archimer.ifremer.fr/doc/00322/43322/

Editor: | Gauthier-villars/editions Elsevier
Formato: | application/pdf
Fonte: | Oceanologica Acta (0399-1784) (Gauthier-villars/editions Elsevier), 2002-03 , Vol. 25 , N. 2 , P. 87-99

Fonte:

2002 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

info:eu-repo/semantics/openAccess

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