中国物理B ›› 2010, Vol. 19 ›› Issue (5): 54103-054103.doi: 10.1088/1674-1056/19/5/054103

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Study of scattering from time-varying Gerstners sea surface using second-order small slope approximation

张彦敏1, 王运华2, 郭立新3   

  1. (1)Department of Physics, Ocean University of China, Qingdao 266100, China; (2)Ocean Remote Sensing Key Laboratory of Ministry of Education, Ocean University of China, Qingdao 266003, China; (3)School of Science, Xidian University, Xi'an 710071, China
  • 收稿日期:2009-09-12 修回日期:2009-10-20 出版日期:2010-05-15 发布日期:2010-05-15
  • 基金资助:
    Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No.~40906088), the National Natural Science Foundation of China (Grant No.~60971067) and Specialised Research Fund for the Doctoral Program of Higher Education (Grant No.~200804231021).

Study of scattering from time-varying Gerstners sea surface using second-order small slope approximation

Zhang Yan-Min(张彦敏)a), Wang Yun-Hua(王运华)b), and Guo Li-Xin(郭立新)c)   

  1. a Department of Physics, Ocean University of China, Qingdao 266100, China; b Ocean Remote Sensing Key Laboratory of Ministry of Education, Ocean University of China, Qingdao 266003, China; c School of Science, Xidian University, Xi'an 710071, China
  • Received:2009-09-12 Revised:2009-10-20 Online:2010-05-15 Published:2010-05-15
  • Supported by:
    Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No.~40906088), the National Natural Science Foundation of China (Grant No.~60971067) and Specialised Research Fund for the Doctoral Program of Higher Education (Grant No.~200804231021).

摘要: Backscattered fields from one-dimensional time-varying Gerstners sea surface are calculated utilising the second-order small slope approximation. It is well known that spectral properties of the backscattered echoes relate to the velocity of the small elementary scatterers on sea surface profiles. Therefore, modeling Doppler spectra from the ocean requires an accurate description of the sea surface motion. The profile of nonlinear Gerstners sea surface shows vertical-skewness of sea waves, it is sharper at the crest and flatter at the trough than linear waves, and its maximum slope position is closer to the crest than to the trough. Furthermore, the horizontal component of the small elementary scatterers orbit velocity on the sea surface, which yields noticeable influence on Doppler spectra, can be obtained conveniently by Gerstners sea surface model. In this study, the characteristics of Doppler spectra of backscattered fields from time-varying Gerstners sea surface are investigated and the dependences of the Doppler frequency and the Doppler bandwidth on the parameters, such as the wind speed, the radar frequency, the incident angle, etc. are discussed. It is shown that the Doppler bandwidth of microwave scattered fields from Gerstners sea surface is considerably broadened. For the case of high frequency backscattered fields, the values of the higher-order spectrum peaks are larger than those obtained by linear sea surface.

Abstract: Backscattered fields from one-dimensional time-varying Gerstners sea surface are calculated utilising the second-order small slope approximation. It is well known that spectral properties of the backscattered echoes relate to the velocity of the small elementary scatterers on sea surface profiles. Therefore, modeling Doppler spectra from the ocean requires an accurate description of the sea surface motion. The profile of nonlinear Gerstners sea surface shows vertical-skewness of sea waves, it is sharper at the crest and flatter at the trough than linear waves, and its maximum slope position is closer to the crest than to the trough. Furthermore, the horizontal component of the small elementary scatterers orbit velocity on the sea surface, which yields noticeable influence on Doppler spectra, can be obtained conveniently by Gerstners sea surface model. In this study, the characteristics of Doppler spectra of backscattered fields from time-varying Gerstners sea surface are investigated and the dependences of the Doppler frequency and the Doppler bandwidth on the parameters, such as the wind speed, the radar frequency, the incident angle, etc. are discussed. It is shown that the Doppler bandwidth of microwave scattered fields from Gerstners sea surface is considerably broadened. For the case of high frequency backscattered fields, the values of the higher-order spectrum peaks are larger than those obtained by linear sea surface.

Key words: Gerstners sea surface, electromagnetic scattering, Doppler spectra, second-order small slope approximation

中图分类号:  (Electromagnetic wave propagation)

  • 92.60.Ta
92.10.Fj (Upper ocean and mixed layer processes) 92.10.Hm (Ocean waves and oscillations) 92.60.Gn (Winds and their effects)