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Open AccessArticle

The Frequency Selective Effect of Radar Backscattering from Multiscale Sea Surface

1
State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
School of Land Resources and Urban and Rural Planning, Hebei GEO University, Shijiazhuang 050000, China
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(2), 160; https://doi.org/10.3390/rs11020160
Received: 10 December 2018 / Revised: 1 January 2019 / Accepted: 12 January 2019 / Published: 16 January 2019
(This article belongs to the Special Issue Radar Imaging Theory, Techniques, and Applications)
The sea surface essentially contains multiscale roughness with capillary waves of many sizes riding on large-scale waves that are also of many sizes. It is instructive to exploit the effect of radar frequency and observation geometry on the effective roughness scales responsible for radar backscattering so that the scattering mechanism and the scattering source can be better understood and quantitated. Based on common sea spectra and a theoretical scattering model, an attempt is made to attain the above objective. Model predictions, with selective roughness scales, are compared with wide validation data, including L-band radar observations, and predictions from C-band and Ku-band empirical models: geophysical model function (CMOD7) and NASA scatterometer (NSCAT-4) for C- and Ku-bands at different incident angles. Numerical results indicate that effective roughness scales for radar backscattering vary with radar frequency and incidence angle and are related to a portion of sea spectral components; the low limit of which is linearly proportional to the Bragg wavenumber determined by frequency and incidence angle, and the scale factor of the linear relationship is about 0.05. In addition, the root mean square (RMS) height and the correlation length of the effective roughness (i.e., scattering source) derived from the effective roughness decrease gradually as incident angle increases. In particular, the correlation length also linearly depends on the effective wavelength with a coefficient of 3.2. Moreover, these two coefficients are both independent of wind speed, radar frequency, and incident angle. These findings also reveal the essential properties of the spectral components contributing to radar backscattering and its variation with radar frequency and incident angle. View Full-Text
Keywords: radar scattering; effective roughness scale; Bragg wavenumber; sea spectrum radar scattering; effective roughness scale; Bragg wavenumber; sea spectrum
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MDPI and ACS Style

Xie, D.; Chen, K.-S.; Zeng, J. The Frequency Selective Effect of Radar Backscattering from Multiscale Sea Surface. Remote Sens. 2019, 11, 160.

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