The influence of moving speeds, wind speeds, and sea level pressures on after-runner storm surges in the Gulf of Tonkin, Vietnam

摘要

The present study investigates the mechanism of the after-runner surge on the coast of the Gulf of Tonkin, Vietnam, due to Typhoon Kalmaegi 2014 landfalling at Quang Ninh province using a coupled model of surge, wave and tide forced by asymmetric and symmetric wind and pressure fields. It is found that the after-runner surge is mainly caused by tailwinds of the typhoon, generating the maximum surge level along the shore on the left side of the track approximately 11 h delayed. The tailwind is attributed to maximumly 60% of the peak surge. As a result, the wind speed is the predominant factor on the Kalmaegi surge on the north coast, while both the wind speed and the sea level pressure have the identical impact on the west and south coasts. Through the numerical experiments, the slower moving speed results in the higher surge level on the right side of the typhoon, while the faster speed causes the higher surge level on the left side of the track. The stronger wind speed and sea level pressure correlatively generate the higher surge along the whole coast. It means that the asymmetry field is critical to the after-runner storm surge.