双频便携式高频海洋雷达远程浪场反演方法研究

After more than forty years of development, high-frequency ocean radar (HFOR) has been widely accepted in ocean surface current measurement. However, the wave inversion is still troubled by problems such as distance limitation and bad robustness, which were further aggravated after the introduction of compact antenna for easing the site selection and deployment of HFOR. Moreover, a new problem about wave-field inversion is risen due to the broaden antenna beam..An integrated wave measurement scheme is proposed by using two radar frequencies and two algorithms. The two algorithms are respectively applicable to high and low sea state according to the radar echo difference. In low or moderate sea state, the power of first-order backscatter of radar echo is unsaturated with wave-height increasing. Hence, we can achieve wave-field inversion from the first-order spectra by establishing the relationship between first-order spectra power and wave-height. To calibrate the effect of variables in radar equation, e.g. system parameters, radio propagation attenuation etc., the dual-frequency data will be employed. In higher sea state, it’s common to observe some discrete spikes (also called line spectra) superposed upon the continuum of second-order spectra. The line spectra is strong enough to enable the remote wave measurement, provided that the scattering model being derived between the line spectra and wave-height. The line spectra also make it available to estimate wave-field with super-resolution algorithm. Besides, dual-frequency is also helpful in solving the wave-height limitation caused by the second-spectra saturation in very high sea state. Based on the above two algorithms, we can achieve the remote wave-field measurement over a large-range sea state. The proposed algorithms have been proven to be right by previous research and experimental results. The work to be carried out will speed up the process of operational wave measurement with HFOR, and will also promote the application of HFOR in ocean surface monitoring.

经过四十余年的发展，高频海洋雷达已成功实现海流的业务化探测，但在海浪反演上却始终面临探测距离近、稳健性差等问题困扰，特别是为便于高频海洋雷达的推广而引入小型化天线之后，上述问题更加突出，且天线波束变宽更带来了浪场探测的难度。.本项目根据不同海况下雷达回波特性的差异，提出了双频率/双算法相结合的综合海浪探测方案。中低海况下基于海浪一阶散射功率的非饱和特性，通过双频率雷达数据解决雷达方程的标校问题，结合海洋观测数据，建立强一阶谱与浪高的关系模型，实现远程浪场反演；高海况下，利用二阶谱中可进行超分辨估角的强线谱成分，建立新的散射关系模型，实现浪场反演，并通过双频融合解决极高海况下二阶谱饱和的问题；将两种算法相结合，实现多海况探测。已进行的预先研究验证了上述方法解决海浪探测问题的可行性。本项目的开展对于加快高频海洋雷达海浪探测的业务化进程，促进其在海洋环境监测领域的推广和应用具有重要意义。

经过四十余年的发展，高频海洋雷达已成功实现海流的业务化探测，但在海浪反演上却始终面临探测距离近、稳健性差等问题困扰，特别是为便于高频海洋雷达的推广而引入小型化天线之后，上述问题更加突出，且天线波束变宽更带来了浪场探测的难度。本项目根据不同海况下雷达回波特性的差异，提出了双频率/双算法相结合的综合海浪探测方案。项目围绕实现多海况条件下的远距离浪场反演目标，重点开展了以下研究：.1）针对高频雷达信号处理中突出的天线方向图畸变问题，提出基于无人机信号源的天线方向图快速、精确测量方法；进一步地，针对相干信号源估计问题，提出了基于数据协方差矩阵重构降低信号相关性的方法，为浪场反演中的超分辨率方位估计奠定了基础。.2）通过理论推导、数值计算、试验观测，研究了海浪-电磁波散射中的一、二阶Bragg效应及散射截面和波高之间的定量关系，揭示了雷达回波谱中一、二阶奇异峰的形成机理，建立了一、二阶奇异谱峰幅度与波高之间的关系模型；在此基础上，分别提出了基于双频一阶峰比值的浪场反演方法、基于二阶与一阶奇异峰比值的浪场反演方法。.3）深入研究了回波谱一、二阶奇异峰与波高、雷达频率之间的关系，根据这种差异关系，提出了双频、双算法融合的联合浪场反演方法，以及浪场数据质量控制方法。.4）项目还开展了大量试验观测去验证算法的有效性，通过将雷达测量得到的浪场数据与浮标、气象模型数据进行对比发现，近岸70km范围内，雷达浪高测量结果与浮标结果吻合良好，二者精度均高于数值模型。.项目相关成果已发表SCI论文19篇，申请发明专利4项。本项目的研究将使便携式高频雷达海浪探测能力从现有10km以内单点测量提升至70km浪场测量，加快高频雷达海浪探测的业务化进程，有效弥补卫星遥感、数值气象模型等在近岸观测的不足，为沿岸数十公里海域的海洋环境监测、数值气象模型同化、灾害预报、风浪新能源利用等提供基础数据支撑。