*Article* **Distribution and Source Sites of Nonlinear Internal Waves Northeast of Hainan Island**

**Jianjun Liang 1,2,\*, Xiao-Ming Li 1,2 and Kaiguo Fan <sup>3</sup>**


**Abstract:** The distribution and source sites of nonlinear internal waves (NLIWs) northeast of Hainan Island were investigated using satellite observations and a wavefront propagation model. Satellite observations show two types of NLIWs (here referred to as type-S and type-D waves). The type-S waves are spaced at a semidiurnal tidal period and the type-D waves are spaced at a diurnal tidal period. The spatial distribution of the two types of NLIWs displays a sandwich structure in which the middle region is influenced by both types of NLIWs, and the northern and southern regions are governed by the type-S and type-D waves, respectively. Solving the wavefront model yields good agreement between simulated and observed wavefronts from the Luzon Strait to Hainan Island. We conclude that the NLIWs originate from the Luzon Strait.

**Keywords:** internal waves; South China Sea; Hainan Island
