Numerical simulation on surge due to landfall of typhoon in the Yangtze Estuary: Ampil (No. 1810) as an example

Typhoon Ampil, with limited magnitude of storm surge, is the most powerful tropical cyclone making landfall in the Yangtze Estuary since 1990. Based on the global atmospheric reanalysis data ERA-Interim, a high-resolution nested numerical model, coupled with storm surge and astronomical tide, is established to study the features of the storm surge induced by Typhoon Ampil, as well as the cause in the Yangtze Estuary. The results show that the storm surge is mainly distributed in the north branch of the Yangtze Estuary while an obvious set-down process is observed in the south branch after the landfall. The landing location of the typhoon clarifies the difference in surge patterns between the north and south branches. Besides the effect of the onshore wind of the gradient wind field, the translation wind has a greater impact on the surge on the right side of the typhoon track and is found to increase the average magnitude of the surge by an additional 26.8% along the coast of the Lianxinggang gauge station in ebb tide conditions. Apart from the intensity, the typhoon track is also one of the important factors affecting the magnitude of the storm surge in the Yangtze Estuary.