# Effect of Tide Level Change on Typhoon Waves in the Taiwan Strait and Its Adjacent Waters
## 3 Study Objects and Areas  
The bathymetric data used in this model are sourced from ETOPO1 of NOAA (the National Oceanic and Atmospheric Administration of the United States). The data interpolation method is used to process the topographic bathymetry data. This calculation scale ranges from 18\({}^{\circ}\) N to 30\({}^{\circ}\) N, 116\({}^{\circ}\) E to 128\({}^{\circ}\) E, and its spatial resolution is 1\({}^{\prime}\)\(\times\) 1\({}^{\prime}\). The distribution of water depth is shown in Figure 1. It can be seen from the figure that the seabed topography gradually increases from the inner sea to the outer sea. Additionally, itshows that the seabed water depth increases with the increase in longitude and latitude. The maximum water depth in the study area is about 7500 m, and the water depth in the Taiwan Strait is below 100 m.  
Tyhoon Mekkhala (whose path is shown in Figure 2a) was named in the northeastern part of the South China Sea at T05:00 on 10 August 2020. At this time, the typhoon center was located at 118.5\({}^{\circ}\) E and 19.6\({}^{\circ}\) N. The central pressure reached 998 hPa, and the central wind speed reached 18 m/s. Subsequently, the typhoon continued its northward trajectory, gradually intensifying in strength until it reached its maximum intensity upon making landfall along the coast of Fujian Province, China. The maximum wind speed reached level 12 (33 m/s), and the central pressure reached 980 hPa. After the landfall, Tyhoon Mekkhala shifted to a certain extent and moved to the north. The intensity gradually weakened and finally almost dissipated at 11:00 on 11 August 2020.  
Tyhoon Maria (Figure 2b) made landfall in Lianjiang County, Fujian Province, China, at 01:00 on 11 July 2018. It was at the time of the astronomical spring tide. The high tide level affected the waves generated by the typhoon. Afterward, the intensity and scale of the typhoon gradually decreased, and the direction changed to the northwest. It continued to move at a speed of 29 km/h and finally dissipated in Jiangxi Province, China. Considering that Typhoon Maria made landfall during the astronomical spring tide, this study specifically focuses on Typhoon Maria as a representative case of a typhoon affected by high tide levels. To investigate the impact of tide levels on waves, this study further  
Figure 1: Bathymetric map.  
Figure 2: Track of typhoons: (**a**) Mekkhala and (**b**) Maria.  
examines the scenario where the typhoon's landing time coincides with the low tide level. By translating the tide levels accordingly, the study aims to explore how the convergence of high tide and low tide at the time of typhoon landing influences wave behavior.  
Figure 2 shows the movement path maps of the two typhoons. The thick solid line represents the coastline, and the thin solid line represents the water depth contour.  
The calculation scale of the tide level model in this paper is 18\({}^{\circ}\) N-30\({}^{\circ}\) N and 116\({}^{\circ}\) E-128\({}^{\circ}\) E. The tide level model adopts a triangular mesh, which has 17,564 nodes and 3111 elements. The calculation time (UTC) for simulation verification is from 0:00 on 10 August 2020 to 23:00 on 12 August 2020. The model calculation takes 30 min as a time step, and the output frequency of the calculation results is 1 result per hour.