油膜覆盖的非线性海面电磁散射多普勒谱特性研究

当海面上方漂浮油膜时，海面的毛细波成分将因油膜的阻尼作用而被破坏.本文采用PM谱，基于Marangoni阻尼效应，建立油膜覆盖的一维Creamer非线性海面模型，并简单分析了油膜的阻尼作用对海面轮廓的影响.在此基础上，利用迭代物理光学方法研究了L波段下该模型的后向散射回波的多普勒谱特性，通过与基于线性模型的海面散射回波多普勒谱对比发现，在大中入射角下，非线性海面散射回波与线性海面多普勒谱的差异不可忽略，说明采用Creamer非线性理论建立海面几何模型的必要性.研究发现，油膜覆盖海面的散射回波的多普勒频移及展宽与干净海面雷达回波的多普勒特性具有明显差异，这表明海面上漂浮的油膜对雷达散射回波的多普勒特性具有显著的影响.数值结果重点分析了入射角、油膜参数以及风速对油膜覆盖海面散射回波多普勒谱展宽和频移的影响规律.

Doppler spectrum simulation of nonlinear ocean covered by oil film

In recent years, marine oil spill has become an important disaster for marine environment. Marine oil spill quantity is an important indicator for evaluating the threat of oil spill. This paper focuses on the Doppler spectrum of one-dimensional (1D) nonlinear ocean covered by oil film. Oil film damps the capillary wave of the ocean, which leads to a smooth profile of the ocean covered by the film. The paper is devoted to the detailed analysis of the electromagnetic magnetic wave scattering from a sea that is covered with oil. More precisely, it focuses on the case of homogeneous oil slicks. This allows better detection of oil spills, as well as possibly an estimation of the amount of oil spilled, as the scattering coefficient depends on the layer thickness. The 1D Creamer nonlinear ocean is proposed based on the PM spectra. The Marangoni damping effect is considered for modeling the contaminated rough ocean surface. First, the influence of oil film on the ocean surface spectrum and geometrical structure are examined briefly in the present study. On this basis, the influence of oil film on the Doppler spectrum signature (in L-band) of the backscattered echo of the clean and contaminated rough ocean are studied in detail based on the iterative physical optics. The results of the Doppler spectrum signature including Doppler shift and spectral bandwidth of the backscattered echo from Creamer nonlinear ocean surface are different from those of the linear ocean surface especially at the big and moderate incident angles, which shows that it is necessary to adopt the Creamer nonlinear model in the paper. The simulation results show that the Doppler spectrum signatures including Doppler shift and spectral bandwidth of the echo from ocean covered by oil film are significantly affected by sea slicks. The influence of some important parameters, such as wind speed, oil-damping values and incident angles on Doppler spectrum signature is investigated and discussed in detail. Moreover, simulation results indicate that the Doppler spectrum signature is a promising technique for the remote sensing of oil films floating on sea surfaces.