Numerical Study Of Wave-current Interactions On Waves During Typhoon Processes

Strong winds generate wind-driven current and waves contemporaneously duringa typhoon process. Interactions of current and waves have significant effects on thegrowth and propogation of typhoon wave, and influence the distribution of waves.China is to the west of Northwest Pacific, thus frequently impacted by typhoon.Typhoon and related ocean disaster casuse huge damage to China. So a study ofwave-current interactions (WCI) on wave during typhoon is meaningful for handlingtyphoon disaster.A coupled current-wave model for seas around Taiwan was developed usingwave model SWAN and water dynamic model ADCIRC. No.11super typhoonNanmadol in2011was simulated with this coupled model. The coupled model wasverified with wave and current observatoy near Fujian coast. It was also found thatHolland typhoon wind model cannot account for the effect of Taiwan Island, so thatthe simulated significant wave height inside Taiwan Strait outnumbers actual value.Three typhoons were selected according to statistics of typhoon path impactingTaiwan Island: Typhoon Nanmadol, Typhoon Wong-Fung and Typhoon Wipha. Thsesthree typhoons was simulated using both coupled model and uncoupled model.Difference between significant wave height simulated by uncoupled and coupledmodel was used to analyze the spatial distribution of wave-current interactions onwave height. The result was: in open deep ocean, wave-current interactions decreasedwave height in front-right quarter of typhoon, while increased wave height in typhooncenter and left-rear quarter; when approaching Taiwan Island, the major influencearea stretched towards east coast of Taiwan Island; the distribution inside TaiwanStrait was changed by topography.The mechanism of the above distribution is explained as follow: wind-drivencurrent impeded growth of wind wave, as well as increased swell propagation speed, the two factors formed the “front-right and left-rear” distribution. Taiwan Islandinterdicted normal propagation path of wave and current, so enhanced the abovemechanism.This study increased our understanding of structure of typhoon wave andwave-current interactions. It also indicates the importance of simulation typhoonwave using coupled models. The result can be referenced by other typhoon wavssimulation efforts.