The mode-2 internal solitary waves (ISWs) generated by mode-2 internal tide (IT) are identified by mooring observations in the northern South China Sea (SCS) from 2016 to 2017. Two mode-2 ISWs with a re-appearance period of 24.9 h observed on 29 and 30 July 2016 are characterized by type-b ISWs. They occurred when the isotherms compressed obviously in the vertical direction. Modal decomposition of IT horizontal currents shows that the vertical compression of the isotherms is mainly caused by diurnal mode-2 IT. The analysis of the role of the density stratification reveals that a deeper and thinner pycnocline is favorable for generation of mode-2 ISWs rather than pycnocline intensity. By comparing the mode-2 nonlinear, dispersion coefficients and the Ursell numbers calculated based on the stratification associated with different kinds of ITs with the observation results, it is shown that the diurnal mode-2 IT plays a crucial role in the generation of the mode-2 ISWs. When the diurnal mode-2 IT interacts with the semidiurnal IT and causes a deeper and thinner pycnocline, the mode-2 ISWs are easily excited.

根据2016年至2017年在南海北部（SCS）的系泊观测，确定了由模式2内潮（IT）产生的模式2内孤立波（ISW）。两次重现期的模式2 ISW 2016年7月29日至30日观察到的24.9 h的特征是b型ISW。当等温线在垂直方向明显压缩时，它们就会发生。IT水平电流的模态分解表明，等温线的垂直压缩主要是由昼夜模式2 IT引起的。对密度分层作用的分析表明，更深和更薄的比可可啉有利于模式2 ISW的产生，而不是比可可可强度更高。通过比较模式2非线性，色散系数和基于与不同类型IT相关的分层计算的Ursell数与观察结果表明，昼夜模式2 IT在模式2 ISW的产生中起着至关重要的作用。当昼夜模式2 IT与半昼夜IT相互作用并导致更深和更薄的比考克林时，模式2 ISW很容易被激发。