## 3 Results and Discussion
The intricate coastline and shallow shoals in this area can amplify and constrain the storm surge, resulting in higher water levels, as previous studies have also reported ([PERSON] et al., 2023) [21]. In contrast, the smooth and deep topography of the open sea region is unfavorable for the accumulation of storm surges. Figure 10 shows the flow field of the Yellow Sea region and the East China Sea region at 5:00 on 25 July with the low tide level of Daishan station. The extreme water level rise was within the range of 0-5 m. The water level in the southern coastal area of Jiangsu rose to 5 m with a flow direction of SE. The water increase is remarkable in the Yangtze River Estuary and Quanzhou, Fujian, where the coastal water level rose by more than 4 m with a flow direction in the Yangtze River Estuary of SE. This indicates that the nearshore areas were closer to the center of the typhoon, experiencing stronger winds and wave forces, which drove tidal fluctuations. Similar storm surge peaks near the landfall point have been observed in previous typhoon events ([PERSON] et al., 2022) [22]. From Figure 11, the extreme water level rise was 0-3 m at 11:00 a.m. when it was high tide at Daishan station. The affected sea area gradually moved from the Giantang River Estuary to the sea area in southern Jiangsu, and the flow direction was transferred from SE to N. In the Yangtze River Estuary and Quantang River Estuary, the coastal water level rise was more than 2 m, and the flow direction of velocity was W. There was no significant rise in the coastal water level in southern and central Jiangsu and Quanzhou, Fujian. The flow direction in southern Jiangsu was NW, and that in Quanzhou was NE. The water increase was enormous in the Yangtze River Estuary and Quanzhou, Fujian, where the coastal water level rose by more than 4 m. The affected center shifted from the Giantang River Estuary to the southern nearshore area of Jiangsu Province as the typhon moved northwestern and made landfall. In contrast, the storm surge in the southern part of Jiangsu Province and Quanzhou, Fujian, decreased to less than 1 m due to the greater distance from the typhoon center. This demonstrates a pronounced spatial distribution change in storm surges associated with the typhoon's path, consistent with previous research ([PERSON] et al., 2018) [23]. In Figure 12, we observe that at the low tide level at Daishan station, the typhoon had a limited impact, affecting only some sea areas in the eastern Hainan and Southern Yellow Sea. In the Quanzhou Sea area, the water level increased to 5 m with a flow direction of northeast. The extreme water level rise in southern Jiangsu ranged from 0 to 3 m with a flow direction of southeast. Conversely, we observed no significant changes in the extreme water level in the Yangtze River Estuary and Quantang Estuary area. The impact of the typhoon was limited, mainly concentrated in the eastern part of Hainan and the southern Yellow Sea adjacent to the landing area. The storm surge in Quanzhou, Fujian, rose sharply, which may be attributed to the tidal-storm surge resonance amplification effect caused by the port topography of Quanzhou Bay. As depicted in Figure 13, the impact of the typhoon was limited to the Yangtze River and Quantang Estuary area, with the extreme water level ranging from 0 to 4.2 m. The flow direction in this region shifted from west to east. Conversely, there was no notable increase in the coastal water level in southern and central Jiangsu and Quanzhou, Fujian. In southern Jiangsu, the flow direction was westward. Similar to Quanzhou Bay, the river mouth topography acts as a constraint and intensifies the storm surge ([PERSON] et al., 2023) [22]. In contrast, the impact was limited in the southern part of Jiangsu Province and Quanzhou, Fujian, indicating that these areas mainly experienced storm surges during the typhoon's approach and had a lesser impact after the passage.