Fig. 1

Observed frequency of all typhoons entered into the north South China Sea (colors) and the trajectories of all typhoons that may threat the Chiwan station (gray line) (a). Number of tropical cyclones entered into the north South China Sea and reached typhoon intensity or above every month from 1990 to 2019, of which the black part is the number of typhoons affecting the Chiwan station (b). The observation frequency was calculated by dividing the latitude and longitude by 1°, and calculating the number of tropical cyclones in each cell grid"

Fig. 2

Scatter distribution of annual daily maximum storm surge (a), change of annual maximumstorm surge (b) and increase rate of annual maximum storm Surge during typhoon-free periods (c)"

Fig. 3

Trajectories and intensity of Typhoon Mangkhut in September 2018 (a), The minimum pressure in the center of the typhoon (b), maximum wind speed (c), radius of maximum wind speed (d), distance between the center of typhoon and the Chiwan Station (e), the water level changes observed at the Chiwan Station (f)"

Fig. 4

The trajectories (a, d, g) of the three types of typhoons, the intensification of storm surge at the Chiwan Station (b, e, h), and the scatter plot between the intensification of storm surge at the Chiwan Station and its distance from the center of the typhoon (c, f, i). The colors in Figure a, d and g are the maximum typhoon wind speed observed at the sampling time of each typhoon, and the colors in (b), (e) and (h) are the measured storm surge intensity at the Chiwan Station at the corresponding time"

Fig. 5

Storm surge as a function of distance between the Chiwan station and typhoon center"

Fig. 6

The relationship between storm surge and typhoon intensity when the distance between typhoon center and the Chiwan station is 0~500 km (a~c), 500~1000 km (d~f), 1000~1500 km (g~i) and greater than 2000 km (j~l). The first column shows the relationship between storm surge and the minimum pressure in the center of the typhoon, the second column shows the relationship between storm surge and the maximum wind speed, and the third column shows the relationship between storm surge and the radius of the maximum wind speed. The solid red lines in (a~c) show the linear fitting results"

Fig. 7

Actual storm surge (a, d, g), empirical model fitting storm surge (b, e, h) and their comparison (e, f, i) by considering typhoon intensity (maximum wind speed, maximum wind speed radius and central minimum pressure) and distance from typhoon center"