This study investigates the characteristics of far-field internal tides (ITs) radiating from the Luzon Strait based on subsurface mooring observations. Measurements indicate that both diurnal and semidiurnal ITs are active at the mooring station, but the diurnal ITs are relatively stronger, with their energy approximately four times that of the semidiurnal ITs. The diurnal ITs exhibit pronounced temporal variations, consisting of 55% coherent and 45% incoherent components and the two components can generate a phase difference of 0.4 \(\pi\) after long-range propagation. In contrast, the incoherent components of semidiurnal ITs account for 84%, giving rise to a more intricate temporal variability. Throughout the observation period, the ratios of horizontal kinetic energy to available potential energy for both diurnal and semidiurnal ITs deviate from their theoretical values and show significant temporal variations, indicating notable IT interference. Additionally, we find that at certain short-term periods, the IT energy show rapid enhancements, and the contributions of the IT energy of each mode are adjusted. To explain these observations, we employed the ray-tracing method to simulate the propagation properties of ITs under different background conditions. The ray-tracing results suggest that internal tidal rays originating from the Luzon Strait are refracted in diverse directions due to the influences of the Kuroshio and mesoscale eddies, which ultimately reduce the coherence of the ITs, increase internal tidal energy, adjust the energy contributions of each mode, and promote IT interference in the far-field. These findings highlight the challenges in accurately predicting far-field ITs in the South China Sea.
