## 3 Results
### Tidal Level Changes by the Typhoon  
Figure 9 shows the time history of tidal levels and their difference under Typhoon Fongwong and the no-wind force action at NB1 (positions shown in Figure 1b) located at the mouth of the NB. It indicates the storm surge caused by the typhoon achieves \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Quantity** & **Station** & **Skill** & **Performance** \\ \hline \multirow{7}{*}{Tidal level} & Sheshan & 1.00 & & Excellent \\  & Luchaogang & 1.00 & & Excellent \\  & Dajishan & 1.00 & & Excellent \\  & Daishan & 1.00 & & Excellent \\  & Tanhu & 1.00 & & Excellent \\  & Zhenhai & 1.00 & & Excellent \\ \hline \multirow{7}{*}{Current velocity} & **Stations** & **Surface** & **Bottom** & **Surface** & **Bottom** \\ \cline{2-5}  & NGN4 SD (speed) & 1.00 & 0.95 & Excellent & Excellent \\  & NGN4 SD (direction) & 1.00 & 1.00 & Excellent & Excellent \\  & CS3 SD (speed) & 0.97 & 0.96 & Excellent & Excellent \\  & CS3 SD (direction) & 1.00 & 1.00 & Excellent & Excellent \\  & NC6D (speed) & 1.00 & 0.93 & Excellent & Excellent \\  & NC6D (direction) & 1.00 & 1.00 & Excellent & Excellent \\ \cline{2-5}  & **Profile** & **Surface** & **Middle** & **Bottom** & **Surface** & **Middle** & **Bottom** \\ \hline \multirow{7}{*}{ Salinity} & A3 & 0.82 & 0.63 & 0.70 & excellent & very good & excellent \\  & A4 & 0.95 & 0.92 & 0.97 & excellent & excellent \\  & A5 & 0.97 & 0.90 & 0.95 & excellent & excellent \\  & A6 & 0.51 & 0.32 & 0.78 & very good & good & excellent \\  & A7 & 0.98 & 0.91 & 0.89 & excellent & excellent & excellent \\  & A8 & 0.79 & 0.68 & 0.63 & excellent & excellent & very good \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary _skill_ values of the assessment model performance. Figure 8: The salinity distribution at 00:00 on 15 September 2014.  
a maximum value at 7:00 on 23 September. Although the typhoon caused abnormal changes, the tidal level process showed a semi-diurnal tidal type, and its change also had a semi-diurnal pattern. During the typhoon rising period, the tidal level has an increasing trend, and this increase reaches a peak during the first half of the typhoon stable stage. An obvious negative storm surge appeared around 24 September 2014 due to the wind direction changing from S/SW to W/NW (shown in Figure 3). During the typhoon falling stage, the storm surge becomes weaker as the time passes. Figure 10a shows the time history of the hydrodynamics, surface salinity, wind speed and atmospheric pressure at NB1 and NB2 located at the middle of the NB (positions shown in Figure 1b). For the tidal level, both NB1 and NB2 have the similar semi-diurnal pattern, but the tidal level rising time at NB1 began earlier than that at NB2. Another interesting phenomenon is that the high water (HW) at NB2 is higher than that at NB1; the former has a maximum value of 2.36 m while the latter is 2.10 m. Similarly, the low water (LW) at NB2 is lower than that at NB1. The higher high water at HW and the lower high water at LW at NB2 causes the tidal level range at NB2 to be larger than that at NB1. In general, the tidal level and its range increase toward the upstream area in the NB due to the combined effects of the funnel-shaped plane geometry of the NB and the typhoon (see Figure 9b). Figure 10: Time history of surface salinity (SS), tidal level (TL), current speed (CS), wind speed (WS) and air pressure (AP) at NB1 and NB2 in 2014: (**a**) with typhoon; (**b**) without typhoon. Figure 9: (**a**)Time history of typhoon-induced and astronomic tidal levels; (**b**) the difference in tidal level (DTL) under Typhoon Fongwong and no-wind force action at NB1. To obtain the spatial distribution of the tidal level in the YRE, we present the tidal level contours (Figure 11) at 7:00 on 23 September with the strongest storm surge and at 5:00 on 19 September with the same tidal phase during the typhoon rising period.