Wave height estimation using the singular peaks in the sea echoes of high frequency radar
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摘要: 高频雷达提取浪高的主流方法依赖于回波二阶谱,非常容易受到外部干扰的影响。为提高高频雷达尤其是小口径雷达浪高估计的精度和探测距离,我们转而研究幅度常常超过其它二阶谱分量的奇异谱。通过便携式高频地波雷达OSMAR-S实测数据和现场浮标风浪数据,分析了对Bragg频率归一化频率分别为1、√2和1/√2三类奇异峰谱值随浪高的幅度响应。分析表明奇异谱幅度响应与一个新模型吻合很好,可以用于提升浪高估计的性能。以浮标数据为基准,雷达在10 km距离上浪高估计值的相关系数达到0.90,均方根误差(RMSE)低至0.35 m。对不同距离拟合性能的进一步分析表明√2峰拟合更好且有效距离能够达到40 km,相关系数为0.78,RMSE为0.62 m。这些结果显示了新模型和浪高估计方法的有效性,为高频雷达测量海面浪高提供了新的途径。Abstract: The popular methods to estimate wave height with high-frequency (HF) radar depend on the integration over the second-order spectral region and thus may come under from even not strong external interference. To improve the accuracy and increase the valid detection range of the wave height measurement, particularly by the small-aperture radar, it is turned to singular peaks which often exceed the power of other frequency components. The power of three kinds of singular peaks, i.e., those around ±1, ±√2 and ±1/√2 times the Bragg frequency, are retrieved from a one-month-long radar data set collected by an ocean state monitoring and analyzing radar, model S (OSMAR-S), and in situ buoy records are used to make some comparisons. The power response to a wave height is found to be described with a new model quite well, by which obvious improvement on the wave height estimation is achieved. With the buoy measurements as reference, a correlation coefficient is increased to 0.90 and a root mean square error (RMSE) is decreased to 0.35 m at the range of 7.5 km compared with the results by the second-order method. The further analysis of the fitting performance across range suggests that the √2 peak has the best fit and maintains a good performance as far as 40 km. The correlation coefficient is 0.78 and the RMSE is 0.62 m at 40 km. These results show the effectiveness of the new empirical method, which opens a new way for the wave height estimation with the HF radar.
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