# Effect of Tide Level Change on Typhoon Waves in the Taiwan Strait and Its Adjacent Waters
## 6 Conclusions  
In this study, a numerical model was developed using SWAN based on the wind field model of Typhoon Mekhala (2006). Tidal data were included in the calculation of the wave model, and the simulation results were validated by actual measurements. It was found that the inclusion of tidal factors could improve the accuracy of typhoon predictions. Typhoon Maria (0607) was used as an example to explore the effect of different tidal levels on typhoon waves. The incoming tide of Typhoon Maria was varied on the time axis to examine its impact, and the main conclusions obtained were as follows:  
1. The simulation results of Typhoon Mekkhala were verified using measured data of significant wave height and wind speed at verification points during the calculation time. The results indicated that the simulated significant wave height and the measured values followed the same change process. The peak time of the wave was also consistent with the time when the typhoon had the greatest impact on the verification point. These findings suggest that the SWAN model is more accurate when coupling tide-level data compared to uncoupled tide-level data.
2. The simulation results of Typhoon Maria were optimized by adjusting the tidal level to better match the actual situation. Based on this, the tidal level during the typhoon's approach was shifted on the time axis. When the high tide phase coincided, the simulated significant wave height at the verification point was higher compared to that without the influence of the tidal level. As a result, the wave height increased, posing a greater danger to shore buildings. Conversely, when the typhoon landed during low tide, the significant wave heights at both verification points decreased by 0.37 m and 0.07 m, respectively.
3. The significant wave height of Typhoon Maria during a high-tide landing differed significantly from that during a low-tide landing. At the Beishuang buoy, the maximum significant wave height difference was 0.71 m (20%), while at the No. 4 buoy, the difference was 0.29 m (3%). The tidal level height had a significant influence on the typhoon's landing, and the tidal level height at the time of the typhoon's landing was positively correlated with the significant wave height of the typhoon wave.
4. The significant wave heights of the verification buoys, Beishuang and No. 4, show significant differences under the influence of different tidal heights. This is because the water depth at the No. 4 buoy is 63 m, which is 2.5 times deeper than that of the northern double buoys (18 m). Therefore, the reference value of significant wave height before the tide level is taken into account is larger for No. 4, amplifying the influence of tide level height on the Beishuang buoy.  
Conceptualization, C.C. and H.X.; methodology, H.X.; software, H.X.; validation, H.X.; writing--original draft preparation, C.P.; writing--review and editing, C.P.; visualization, T.W.; supervision, M.W.; project administration, C.C.; funding acquisition, C.C. All authors have read and agreed to the published version of the manuscript.  
The work was financially supported by the National Natural Science Foundation of China (Grant No. 51809047); the National Natural Science Foundation of China (Grant No. U22A20585); and the Fujian Provincial Natural Science Foundation (Grant No. 2019)05029).  
Data Availability Statement: Data will be made available on request.  
The authors declare no conflict of interest.