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| Nouguier, Frederic; Guerin, Charles-antoine; Soriano, Gabriel. |
| This paper is the first in a series of two papers on the use of combined improved hydrodynamic and electromagnetic analytical models for the simulation of the ocean Doppler spectrum at microwave frequencies. Under a linear assumption for the sea surface, we derive statistical expression for the main Doppler characteristics according to asymptotic scattering models. We consider classical models such as the Kirchhoff approximation and the two-scale model, as well as the more recent weighted curvature approximation (WCA). We recover two salient features of Doppler signature in the microwave regime. First, the Doppler characteristics are very sensitive to polarization, with higher mean Doppler shift in horizontal polarization. This is correctly rendered by the... |
| Tipo: Text |
Palavras-chave: Doppler spectrum; Gravity waves; Microwave; Remote sensing; Rough surfaces; Scattering; Sea surface. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00054/16524/14379.pdf |
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| Nouguier, Frederic; Mouche, Alexis; Rascle, Nicolas; Chapron, Bertrand; Vandemark, Douglas. |
| Global colocalized ocean surface measurements using the Global Precipitation Measurement near-nadir dual-frequency Ku- and Ka-band microwave measurements are analyzed and compared. Focusing on the Ka and Ku cross-sections fall-off with incidence angles, the contemporaneous measurements enable to more precisely document differing ocean scattering characteristics for both microwave frequencies. Sensitivity with wind speed and significant wave height is further reported using global comparisons with numerical estimates. As demonstrated, the bifrequency capability can provide direct means to efficiently separate short-scale wave contributions, between mean squared slope and curvature characteristics, and to further gain valuable insights concerning near-nadir... |
| Tipo: Text |
Palavras-chave: Microwave; Radar cross section; Scattering; Spaceborne radar. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00352/46334/47128.pdf |
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| Bertrand, E; Deschamps, A; Virieux, J. |
| An investigation of the teleseismic P -wave coda is performed using the single-scattering approximation. The method allows one to image short-wavelength scale (less than or equal to2 km) velocity and density heterogeneities and structures that are barely detected by traveltime tomography. Source effects are removed by using receiver functions for data interpretation, but the amplitude (especially the sign of the signal) is synthesized. Both broad-band seismological stations in the southwestern Alps (France) and Campanian plain (Italy) are used for the illustration of the proposed method. Because of the large aperture of our arrays, laterally small-scale heterogeneities are difficult to image and we must assume lateral continuity of the detectable... |
| Tipo: Text |
Palavras-chave: Body waves; Broad-band; Crustal structure; Moho discontinuity; P-to-S conversions; Scattering; Waveform analysis. |
| Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/00466/57762/60036.pdf |
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| Kudryavtsev, V; Akimov, D; Johannessen, Johnny; Chapron, Bertrand. |
| [1] A new radar imaging model of ocean current features is proposed. The simulated normalized radar cross section ( NRCS) takes into account scattering from "regular'' surfaces ( by means of resonant Bragg scattering and specular reflections) and scattering from breaking waves. The description of background wind waves and their transformation in nonuniform medium is based on solution of the wave action conservation equation. Wave breaking plays a key role in the radar imaging model. Breaking waves scatter radio waves ( thus directly contributing to the NRCS), provide energy dissipation in wind waves ( thus defining the wave spectrum of intermediate scale waves), and generate short surface waves ( thus affecting Bragg scattering). Surface current,... |
| Tipo: Text |
Palavras-chave: Breaking waves; Scattering; Radar imaging model; Ocean surface current. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-762.pdf |
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| Tran, Ngan; Chapron, Bertrand; Vandemark, D. |
| This letter uses a large ocean satellite data set to document relationships between Ku-band radar backscatter (sigma-0) of the sea surface, near-surface wind speed (U), and ocean wave height (SWH). The observations come from satellite crossovers of the Tropical Rainfall Mapping Mission (TRMM) Precipitation Radar (PR) and two satellite altimeters, namely: 1) Jason-1 and 2) ENVISAT. At these nodes, we obtain TRMM clear-air normalized radar cross-section data along with coincident altimeter-derived significant wave height. Wind speed estimates come from the European Centre for Medium-Range Weather Forecast. TRMM PR is the first satellite to measure low incidence Ku-band ocean backscatter at a continuum of incidence angles from 0 degrees to 18 degrees. This... |
| Tipo: Text |
Palavras-chave: Space borne radar; Scattering; Radar cross section; Altimetry. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3299.pdf |
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| Tenerelli, Joseph; Reul, Nicolas; Mouche, Alexis; Chapron, Bertrand. |
| The "galactic glitter" phenomenon at L-band, i.e., the scattering of celestial sky radiation by the rough ocean surface, is examined here as a potential source of error for sea surface salinity (SSS) remote sensing. We begin by considering the transformations that must be applied to downwelling celestial noise in order to compute the eventual impact on the antenna temperature. Then, outside the context of any particular measurement system, we use approximate scattering models along with a model for the equilibrium wind wave spectrum to examine how the scattered signal at the surface might depend on the geophysical conditions and scattering geometry. It is found that, when the specular point lies far away from the galactic plane, where the incident... |
| Tipo: Text |
Palavras-chave: Scattering; Remote sensing; Radiometry. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3922.pdf |
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| Batista,Lurimar S.; Sampaio,Edson E. S.. |
| The complete and exact solution of the scattering of a TE mode frequency domain electromagnetic plane wave by a vertical dike under a conductive overburden has been established. An integral representation composed of one-sided Fourier transforms describes the scattered electric field components in each one of the five media: air, overburden, dike, and the country rocks on both sides of the dike. The determination of the terms of the series that represents the spectral components of the Fourier integrals requires the numerical inversion of a sparse matrix, and the method of successive approaches. The zero-order term of the series representation for the spectral components of the overburden, for given values of the electrical and geometrical parameters of... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Scattering; Electromagnetic waves; Vertical dike. |
| Ano: 2003 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652003000200007 |
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