基于X波段雷达的海洋动力学参数提取算法初步研究

Basic Analysis on the Extraction of Ocean Dynamic Parameters with an X-band Radar

从X波段船舶雷达记录的连续雷达图像中,可以获得海浪频谱和海流的信息。在不存在海洋表面流的情况下,雷达图像的三维频谱分布在由静水色散关系确定的平面轨迹上。海流的存在会使三维频谱的能量分布产生相应的多普勒频移,对此频移进行最小二乘拟合,可以确定海流的大小和方向,进而得到有向浪高谱。本文基于通用的海浪谱和方向函数,在考虑阴影调制的情况下仿真海面X波段雷达图像序列,分别对无海流和有海流作用下的三维频谱进行了数值模拟,通过海流产生的多普勒频移拟合出海流,并获得二维图像谱。最后分析了McMaster大学X波段雷达的实测定向海面回波数据,获取了海浪的一维图像频谱。

Ocean wave spectrum and surface currents can be determined from a series of spatial wave images recorded by X-band marine radar. In the absence of surface current, the three-dimensional spectral energy resulted from the series of images will be confined to a trajectory defined by the still water dispersion relationship. The presence of a surface current will make the three-dimensional spectral energy show a corresponding Doppler shift from which the current velocity can be inferred using the least squares method and then the directional wave spectrum can be also obtained. On the basis of conventional wave spectrum and directional function, the paper emulates a series of X-band radar images considering shadow modulation and simulates numerically the three-dimensional spectrum both with and without ocean surface current, calculates the current velocity by virtue of the Doppler shift, and obtains the two-dimensional image spectrum. Finally the paper analyzes the ocean data measured in a fixed staring direction by an X-band radar in McMaster University and obtains the one-dimensional image spectrum.