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Cite this paper: |
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CHEN Ping, YIN Qiaohua, HUANG Ping. Effect of non-Gaussian properties of the sea surface on the low-incidence radar backscatter and its inversion in terms of wave spectra by an ocean wave spectrometer[J]. Journal of Oceanology and Limnology, 2015, 33(5): 1142-1156 |
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Effect of non-Gaussian properties of the sea surface on the low-incidence radar backscatter and its inversion in terms of wave spectra by an ocean wave spectrometer |
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| CHEN Ping1,2, YIN Qiaohua1,2, HUANG Ping1,2 |
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1 Science and Technology on Multi-spectral Information Processing Laboratory, Wuhan 430074, China;
2 School of Electronic Information and Communications, Huazhong University of Science and Technology, Wuhan 430074, China |
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| Abstract: |
| The principle of ocean wave spectrometers was first presented several decades ago to detect the directional wave spectrum with real-aperture radar (Jackson, 1981).To invert wave spectra using an ocean wave spectrometer, for simplicity, the hydrodynamic forcing and wave-wave interaction effect are neglected and a Gaussian slope probability density function (pdf) is used to calculate the normalized backscattering cross-section (σ0) of the ocean surface.However, the real sea surface is non-Gaussian.It is not known whether the non-Gaussian property of the sea surface will affect the performance of the inversion of the wave spectrum if following existing inversion steps and methods.In this paper, the pdf of the sea surface slope is expressed as a Gram-Charlier fourth-order expansion, which is quasi-Gaussian.The modulation transfer function (MTF) is derived for a non-Gaussian slope pdf.The effects of non-Gaussian properties of the sea surface slope on the inversion process and result are then studied in a simulation of the SWIM (Surface Waves Investigation and Monitoring) instrument configuration to be used on the CFOSAT (China-France Oceanography Satellite) mission.The simulation results show that the mean trend of σ0 depends on the sea slope pdf, and the peakedness and skewness coefficients of the slope pdf affect the shape of the mean trend of σ0 versus incidence and azimuth;owing to high resolution of σ0 in the range direction, MTF obtained using the mean trend of σ0 is almost as accurate as that set in the direct simulation;in the inversion, if ignoring the non-Gaussian assumption, the inversion performances for the wave spectrum decrease, as seen for an increase in the energy error of the inverted wave slope spectrum.However, the peak wavelength and wave direction are the same for inversions that consider and ignore the non-Gaussian property. |
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| Key words:
slope probability density of the sea surface|ocean wave spectrometer|non-Gaussian|directional wave spectrum|energy error
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| Received: 2014-07-01 Revised: 2014-09-19 |
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