Inner shelf response to storm track variations over the east LeiZhou Peninsula, China

The LeiZhou Peninsula is situated at the southern tip of mainland China with frequent tropical cyclone activity. Its special feature of large-scaled westward concaved coastline results in complex storm-induced hydrodynamic processes in a variety of spatial scales. Statistics show that the surge distributions in the east LeiZhou Peninsula are sensitive to the landfall location and moving direction of the storm tracks. This paper provides a detailed assessment to investigate the nearshore and coastal responses to different tropical cyclone behaviours in this region. A high-resolution integrally-coupled wave and circulation model (FVCOM-SWAVE) on a large-domain unstructured mesh containing the northern South China Sea is applied in this study. The model is validated by observed water level records during three typical typhoon events of Krovanh (2003), Kai-tak (2012) and Mujigae (2015). Induced by the right-handed cyclone wind rotation at the northern hemisphere, surges at ZhanJiang and NanDu perform as set-up processes when the storm lands to the south of the ZhanJiang Bay and as mixtures of slight set-up and medium set-down when the storm lands to the north of the ZhanJiang Bay. For set-up cases, the storm tracks with moving direction of WNW (α = 10° ∼ 30°) are more likely to cause heavy surges. Complex coastal morphology has great impacts on the surge distributions. For outer-bay coastlines, the area at the distance of 1 × RMW ∼ 1.5 × RMW right to the cyclone track is most dangerous prone to high surge. For inner-bay areas, three high-risk regions-the NanSan Channel, the HuGuang branch of the ZhanJiang Bay and west coast of the LeiZhou Bay-are more likely to generate violent surges because of their westward narrowing-down configurations. Protected by a narrow entrance oriented to ESE, surge variations in the ZhanJiang Bay are less sensitive to the variations of landfall location and moving direction than that in the LeiZhou Bay.