Internal solitary waves (ISWs) make important contributions to the energy cascade, ocean mixing and material transport in the ocean. However, there are few observational studies on the vertical structure of ISWs. In this article, we describe and analyze 11 ISWs near Dongsha Atoll in the South China Sea directly observed using two-dimensional seismic data. We calculate the vertical structures of these ISWs, and compared them with two theories. We find that three ISWs conform to the linear vertical structure function, four conform to the first-order nonlinear vertical structure function, and the remaining conform to neither function. We use the empirical mode decomposition (EMD) method to analyze reasons for the difference between the observed and theoretical vertical structures. The results show that the vertical structure is mainly determined by nonlinearity, which is an important dynamic characteristics of ISW. Therefore, whether the theory conforms to the observation depends on the ability of theory to describe the nonlinear characteristics of ISWs. In addition, topography and background flow affect the vertical structure.

内部孤立波（ISW）对能量级联，海洋混合和海洋中的物质传输做出了重要贡献。但是，很少有关于ISW垂直结构的观测研究。在本文中，我们描述和分析了使用二维地震数据直接观测到的南海东沙环礁附近的11个ISW。我们计算了这些ISW的垂直结构，并将它们与两种理论进行了比较。我们发现，三个ISW符合线性垂直结构函数，四个符合一阶非线性垂直结构函数，其余ISW都不符合函数。我们使用经验模式分解（EMD）方法来分析观察到的垂直结构与理论垂直结构之间的差异的原因。结果表明，竖向结构主要由非线性决定，这是ISW的重要动力特性。因此，理论是否与观测结果相符取决于理论描述ISW非线性特征的能力。此外，地形和背景流也会影响垂直结构。