Coastal Hazards Caused by Different Extreme Storms in the Bohai Sea, China

The Bohai Sea, a semi-enclosed epicontinental sea, suffers different storms frequently, mainly tropical cyclones in summer/autumn and cold waves in winter/spring. The extreme storms can cause severe coastal hazards such as flooding, coastal structures and ocean platforms failures. A numerical model is set up for the Bohai Sea using MIKE21 with coupled hydrodynamic and wave modules. Observed data of water levels, velocities and wave are used to make model calibration. Based on this model, three typical tropical cyclones and cold waves are simulated. Then the major characteristics of summer tropical cyclones and winter cold waves are discussed. Affected by the tropical cyclone, the water levels of Laizhou Bay and Bohai Bay increase and that of Liaodong Bay decreases. Influenced by the cold wave coupled with an extratropical cyclone, the water levels of Laizhou Bay and Bohai Bay decrease firstly and then increase, which is contrary to the variation trend of water level at Liaodong Bay. Under the single cold wave weather, the water level increases at Laizhou Bay, decreases at Liaodong Bay, and firstly increases then decreases at Bohai Bay. The maximum of surge level caused by cold wave coupled with extratropical cyclone is smaller than that induced by tropical cyclone and single cold wave weather.