Polarimetric SAR Response Analysis Of Ocean Internal Waves And Its Inversion Application

Ocean internal waves are phenomena of underwater fluctuations that frequently occur in the global seas,and they have a non-negligible impact on the energy mixing,nutrient transportation,and engineering construction in the ocean.Insuit observations show that the generation and propagation of internal waves are accompanied by large amplitude changes.At the same time,as an underwater phenomenon,it will change the rough undulations of the sea surface,thereby changing the scattering characteristics of the sea surface.At present,remote sensing methods have been used to study the generation source,generation mechanism,temporal and spatial distribution,and propagation characteristics of internal waves,but there are few studies on the rough changes and scattering characteristics of the sea surface caused by internal waves.In this paper,the polarimetric SAR is mainly used to analyze the sea surface scattering characteristics of internal waves,calculate the sea surface roughness change caused by internal waves,and to explore the relationship between it and its amplitude.First of all,based on the theory of polarimetric SAR,the polarization features that have a better effect on internal wave detection are screened and analyzed the polarization scattering characteristics of the surface.Then,based on the fully polarized images,the extended Bragg wave scattering model is used to inversely calculate the sea surface roughness change caused by internal waves.Finally,the half-amplitude width of the internal wave is obtained from the optimal polarization feature images and the amplitude inversion is performed to analyze the relationship between the amplitude of the internal wave and the change of the sea surface tilt caused by it.The main conclusions are as follows:(1)Internal waves have good polarimetric SAR response performance.Compared with a uniform sea surface,the sea surface that it acts on has a stronger polarization scattering power.The scattering mechanism is mainly surface scattering,and it also contains weak body scattering characteristics;the depolarization effect of internal waves is stronger than that of the sea surface and there is a cross Polarization effect,and will produce a certain degree of rough titlt on the sea surface.(2)Among the characteristic features of fully polarized SAR,the surface scattering coefficient Odd,Lambda,total polarization power Span,coherence matrix eigenvalue?1,polarization entropy H,and average scattering angle are good for internal wave detection.Among the characteristic features of compact polarized SAR,Lambda,total polarization power Span,coherence matrix eigenvalue ?1,polarization entropy H and Stokes parameters StokesgO and Stokesg3 have good internal wave response effects.(3)Internal waves can cause changes in the rough titlt of the sea surface.Based on the X-Bragg model,an index of relative changes in the sea surface caused by internal waves ?? is constructed,and the value calculated using fully polarized SAR images ranges from 0 to 30%.Preliminary experiments show that the rough tilt change index?? can be used as an indicator for internal wave detection and identification in polarized SAR images.(4)The polarization feature images can be used to obtain the half-amplitude width of the internal waves and invert the internal waves amplitude accordingly.There is a positive correlation between the sea surface rough titlt change caused by internal waves and its amplitude.The larger the amplitude of the internal waves,the larger the sea surface rough titlt change value.