S层波段多普勒雷达表层流信息提取方法研究

发布时间：2018-10-22 20:17

【摘要】：表层流是海洋中重要的运动现象,了解和掌握表层流的运动规律,将有助于研究海洋表层流的形成、成长、传播以及衰退等机制,也对近岸区域的水产业、运输业以及排污等意义重大。目前已经有许多的表层流探测设备,其中,微波多普勒雷达具有时空分辨率高、抗干扰性能好、全天候工作、体积小等优点,应用前景良好。本文基于武汉大学无线电海洋遥感实验室独立研发的S波段多普勒雷达为平台,针对海洋表层流信息提取方法进行了研究,扩展S波段多普勒雷达的探测功能。S波段多普勒雷达发射的电磁波与海表面的毛细波产生布拉格散射,而小尺度的毛细波受大尺度重力波的调制作用,携带着重力波的特征信息。基于重力波频率与波数的耗散关系,可以提取表层流信息。目前基于微波多普勒雷达表层流信息提取的研究有双频测流技术和速度序列时间平均的方法,对于岸基单站S波段多普勒雷达提取表层流的研究,本文根据重力波频率与波数的耗散关系,通过对雷达测量的二维径向速度序列进行处理,提取表层流信息。论文首先介绍了 S波段多普勒雷达的表层流信息提取算法:通过对雷达测量的二维径向速度序列进行二维傅里叶变换得到频率波数谱,计算得到功率谱后,提出带通滤波结合自适应阈值的方法选择离散的待拟合数据点,依据重力波频率与波数的耗散关系,基于加权最小二乘原则可以拟合得到重力波耗散关系曲线,从而提取径向流速值。通过雷达六根天线数据提取的六个径向流速值,可以合成矢量流,得到流速和流向信息。然后基于表层流提取算法,进行了仿真分析,基于仿真数据验证了算法的正确性。通过已知的海浪谱模型,并且将表层流因素考虑进去,可以仿真得到加入表层流信息的二维径向速度。基于仿真数据,采用单天线径向流速提取算法与合成矢量流的方法,计算得到的结果与理论值的误差很小,仿真结果表明算法正确。最后通过对S波段多普勒雷达实测的数据进行处理,来提取表层流信息。针对实测数据中存在奇异点的问题,通过分析时空二维多普勒谱参数的特征,提出先时间后空间去除奇异点的数据预处理方法,其中空间采用滑窗自适应门限检测奇异点。数据预处理后,由单天线实测数据可以提取径向流速值,利用提取的六天线径向流速值可以合成矢量流。结合遮浪岛和朱家尖的实测数据,采用多点数据分析和全天数据分析,结果表明算法具有可行性。
[Abstract]:Surface current is an important movement phenomenon in the ocean. Understanding and mastering the motion law of surface current will be helpful to study the formation, growth, propagation and decline of ocean surface current, and also to aquatic industry in coastal area. Transportation and sewage are of great significance. At present, there are many surface current detection equipments, among which microwave Doppler radar has the advantages of high space-time resolution, good anti-jamming performance, all-weather operation, small volume and so on. Based on the S-band Doppler radar developed independently by the Radio Marine remote Sensing Laboratory of Wuhan University, this paper studies the method of extracting ocean surface current information. The electromagnetic wave emitted by S band Doppler radar and the capillary wave on the sea surface produce Bragg scattering, while the small scale capillary wave is modulated by the large scale gravity wave. Carries the characteristic information of gravity waves. Based on the dissipative relation between gravity wave frequency and wave number, surface flow information can be extracted. At present, the research based on microwave Doppler radar surface laminar flow information extraction has dual-frequency current measurement technology and velocity series time averaging method, for shore-based single-station S-band Doppler radar extraction of surface flow. According to the dissipative relation between the frequency of gravity wave and the wave number, the surface flow information is extracted by processing the two-dimensional radial velocity series measured by radar. Firstly, the paper introduces the surface flow information extraction algorithm of S-band Doppler radar. The frequency wavenumber spectrum is obtained by the two-dimensional Fourier transform of the two-dimensional radial velocity series measured by the radar, and the power spectrum is obtained by calculating the power spectrum. The method of bandpass filter combined with adaptive threshold is proposed to select discrete data points to be fitted. According to the dissipative relation between the frequency of gravity wave and the number of waves, the curve of dissipation relation of gravity wave can be fitted based on the weighted least square principle. Thus the radial velocity is extracted. The vector flow can be synthesized from the six radial velocity values extracted from the data of six radar antennas and the information of velocity and flow direction can be obtained. Then, based on the surface flow extraction algorithm, the simulation analysis is carried out, and the correctness of the algorithm is verified based on the simulation data. Based on the known wave spectral model and taking into account the surface flow factors, the two-dimensional radial velocity with the surface current information can be simulated. Based on the simulation data, the radial velocity extraction algorithm of single antenna and the synthetic vector flow method are adopted. The error between the calculated results and the theoretical values is very small. The simulation results show that the algorithm is correct. Finally, the surface flow information is extracted by processing the measured data of S band Doppler radar. In order to solve the problem of singularity in measured data, by analyzing the characteristics of space-time two-dimensional Doppler spectral parameters, a new method of data preprocessing is proposed, in which the sliding window adaptive threshold is used to detect singularities. After data preprocessing, the radial velocity can be extracted from the measured data of single antenna, and the vector flow can be synthesized by using the extracted radial velocity of six antennas. Combined with the measured data of Yalang Island and Zhu Jia-jian, the multi-point data analysis and all-day data analysis are used. The results show that the algorithm is feasible.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN958

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