Reflection of the K₁ internal tides (ITs) in the northern South China Sea (SCS) is investigated using a high-resolution three-dimensional numerical model. The simulated results indicate that the westward K₁ ITs generated at the Luzon Strait (LS) first impact the continental slope in the northern SCS, and thereafter are reflected. There is a total of 0.31 GW of K₁ energy that are reflected, suggesting a weak reflection considering 3.54 GW of westward K₁ energy from the LS. Two reflected K₁ beams are revealed. The southeast one is the more energetic and can propagate across the deep basin, agreeing with that extracted from satellite altimeter data. The eastward one propagates toward the LS, but it is absent in altimeter results because of its lower intensity. Both the two reflected beams are radiated from the supercritical region in shallow water. Different from the incident waves that are dominated by mode-1, the reflected waves exhibit a multimodal structure. Contribution of high modes to reflected waves is comparable to that of mode-1. Moreover, modal content is different for the two reflected beams, with higher proportion of high-mode energy flux for eastward reflected beam. In contrast to the K₁ ITs, no remarkable reflected O₁ ITs are detected from either simulated or altimeter results. This is due to the weak generation of O₁ ITs at the LS, which leads to less O₁ energy reaching the continental slope. The results of this work can provide essential insight on IT dynamics in the SCS.

K₁内潮在南海北部大陆坡的反射

中文摘要：使用高分辨率的三维数值模式研究K₁内潮（ITs）在南海北部的反射。模拟结果显示，在吕宋海峡西部生成的西向K₁内潮首先影响南海北部的大陆坡，而后被反射。吕宋海峡的西向K₁内潮能量为3.54 GW，共有0.31 GW的K₁内潮能量被反射，这表明反射作用较弱。研究两个反射的K₁束发现东南向的K₁束能量较大，可以传播到深海盆，这卫星高度计数据提取的结果一致。东北向的K₁束向吕宋海峡传播，但由于其强度较低，在高度计结果中不存在。两束反射波都是从浅水超临界区辐射出来的。与入射波以第一模态占主不同，反射波表现出多模态结构。高模态对反射波的贡献与第一模态相当。此外，两束反射波的模态含量不同，东向反射波的高模态能量通量占比更高。与K₁内潮相比，无论是模拟结果还是高度计结果都没有检测到明显的O₁内潮反射。这是由于吕宋海峡处生成的O₁较弱，导致到达大陆坡的O₁能量较少。这项工作的结果为了解南海的内潮动力学提供必不可少的观点。