On-site measurements show that water waves near islands and reefs in South China Sea exhibit different properties of wave energy distributions with regard to wave frequencies, among which the most prominent factor is the interplay of swells arising from the West Pacific Ocean and the local wind waves. Observations also show that the breaking waves continuously appear, containing more energy in high frequency components, and the nonlinear characteristics of the waves are important in adjusting the energy distribution. These properties may explain the large discrepancies between the well-accepted wave spectra (for example the P-M spectrum, Neumann spectrum, ITTC spectrum etc.) and the measured wave spectra near islands and reefs in South China Sea. Therefore, a new Rational Function Spectrum is proposed in this paper to describe waves near islands and reefs which turns out to show satisfactory accuracy. It well captures wave power distributions in the form of single and double peaks, at low- and high-frequency regions, as well as nonlinear scale power law. Based on the investigation of the measured data near an island in South China Sea, the relation between the parameters used in the Rational Function Spectrum and the statistical parameters of water waves (significant wave height and wave period) is established. It is noted that the wave properties at low- and high- frequencies are controlled by the local wind velocities at the wave growth stage, but remain constant at the wave decay stage. The parameter peak frequency is only dependent on the wave period corresponding to the maximum wave height. The parameter spectral peak is determined from the wave height and the wave period. These relations help to clarify the physical meanings of the parameters used in the Rational Function Spectrum, and thus provide an alternative spectral form to describe random waves near islands and reefs.

现场测量表明，南海岛礁附近的水波在波浪频率上表现出不同的波能分布特性，其中最突出的因素是西太平洋涌浪与局地风的相互作用。波浪。观测还表明，破碎波不断出现，在高频成分中含有较多的能量，波的非线性特性对调整能量分布具有重要意义。这些特性可以解释广为接受的波谱（例如PM谱、诺依曼谱、ITTC谱等）与在南海岛礁附近实测的波谱之间的巨大差异。所以，本文提出了一种新的有理函数谱来描述岛礁附近的波浪，结果显示出令人满意的准确性。它可以很好地捕获低频和高频区域的单峰和双峰形式的波浪功率分布，以及非线性尺度幂律。通过对南海某岛屿附近实测数据的调查，建立了有理函数谱中使用的参数与水波统计参数（有效波高和波周期）之间的关系。值得注意的是，低频和高频的波浪特性在波浪增长阶段受当地风速控制，但在波浪衰减阶段保持不变。参数峰值频率仅取决于对应于最大波高的波周期。参数谱峰由波高和波周期确定。这些关系有助于阐明有理函数谱中使用的参数的物理意义，从而提供一种替代谱形式来描述岛礁附近的随机波。