Wave height measurement in the Taiwan Strait with a portable high frequency surface wave radar
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摘要: 高频地波雷达作为一种重要的海态遥感设备, 已经受到越来越多的关注. 强外部噪声和因混叠导致的一阶和二阶谱区的错误划分, 是使用基于二阶谱和一阶谱积分之比的传统方法提取浪高时产生较大误差的两个主要因素. 针对此问题, 在浪高估计中引入了两个新的指标, 一是二阶连续谱最大值与一阶谱峰值之比, 二是二阶谐振峰与一阶谱峰之比. 与传统指标一样, 两个新指标与浪高均具有强相关性, 基于此提出了两个估计浪高的半经验模式. 所有三种模式得到的浪高估计组合在一起并施以平滑给出最终的浪高估计. 这种方法应用于高频地波雷达OSMAR-S历时近三个月的现场实验中. 该雷达是由武汉大学于2006年开发的便携式高频地波雷达. OSMAR-S测量的有效浪高与作为比对数据的由Oceanweather公司提供的浪高数据之间的相关系数为0.74, 方均根误差为0.77m. 新提出的方法对浪高估计得到了明显的改善, 使OSMAR-S浪高测量的实用化又向前迈进了一步.Abstract: As an important equipment for sea state remote sensing, high frequency surface wave radar (HFSWR) has received more and more attention. The conventional method for wave height inversion is based on the ratio of the integration of the second-order spectral continuum to that of the first-order region, where the strong external noise and the incorrect delineation of the first- and second-order doppler spectral regions due to spectral aliasing are two major sources of errors in the wave height. To account for these factors, two more indices are introduced to the wave height estimation, i.e., the ratio of the maximum power of the second-order continuum to that of the Bragg spectral region (RSCB) and the ratio of the power of the second harmonic peak to that of the Bragg peak (RSHB). Both indices also have a strong correlation with the underlying wave height. On the basis of all these indices an empirical model is proposed to estimate the wave height. This method has been used in a three-months long experiment of the ocean state measuring and analyzing radar, type S (OSMAR-S), which is a portable HFSWR with compact cross-loop/monopole receive antennas developed by Wuhan University since 2006. during the experiment in the Taiwan Strait, the significant wave height varied from 0 to 5 m. The significant wave heights estimated by the OSMAR-S correlate well with the data provided by the Oceanweather Inc. for comparison, with a correlation coefficient of 0.74 and a root mean square error (RMSE) of 0.77 m. The proposed method has made an effective improvement to the wave height estimation and thus a further step toward operational use of the OSMAR-S in the wave height extraction.
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Key words:
- wave height /
- high frequency surface wave radar /
- field experiment /
- comparison /
- Taiwan Strait
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