南海北部台风海浪谱的双峰性和成长性

本论文通过对南海北部三次台风过境期间基于浮标观测的海浪谱进行分析，发现虽然大部分成熟的台风海浪谱为单峰结构，但实际上在台风海浪的成长和衰减阶段，双峰谱占据了很大的比例。双峰谱的形成主要是由于风浪和涌浪的叠加以及不同波分量之间的非线性相互作用，我们可以通过能量密度的成长率对谱型变化进行高效的预报。此外，台风海浪的主要波向依赖于台风中心相对观测点的位置，而波向的分散情况在相距台风中心较远的区域无明显规律。本文提出了一个新的六参数波浪谱型拟合双峰谱，其拟合效果相较于前人的谱型更好。通过验证，形状参数和谱宽度之间的理论关系依然适用于单个谱峰。通过分析谱参量的变化特征，证明了谱参量不仅与台风强度和台风路径相关，还存在很强的交互相关。最后通过拟合海浪谱数据，本文得到了台风影响下海浪有效波高和有效周期之间的成长关系，这对海洋工程实际应用具有重要意义。

Bimodality and growth of the spectra of typhoon-generated waves in northern South China Sea

Buoy-based observations of wave spectra during the passage of three typhoons in the northern South China Sea are examined. Though most spectra of mature typhoon-generated waves are unimodal, double-peaked spectra account for a significant proportion during the growing and decaying stages. This is due either to the superposition of swells on local wind waves or to the mechanism of nonlinear interaction between different wave components. The growth rate of energy density is an effective way to predict spectrum variation. The dominant wave direction depends on the location of the typhoon center to the site, but the direction spread shows no regularity in distant regions. In this study, a new six-parameter spectral formula is proposed to represent double-peaked spectra and is shown to provide a better fit than previous models. The theoretical relationship between shape parameter and spectral width is still applicable to each peak. The characteristics of the variations of spectral parameters are analyzed. It is demonstrated that the spectral parameters are not only related to the typhoon intensity and typhoon track, but also have strong intercorrelations. Moreover, the growth relation between significant wave height and significant wave period is obtained to fit the typhoon-generated waves.