Improving storm surge simulations by considering wave-steepness-dependent drag coefficient in the northern East China Sea
Li Zhao, Shuiqing Li, Po Hu, Xingru Feng, Dongxue Mo, Jian Li
Abstract
The northern East China Sea (NECS) is a semienclosed basin that is frequently attacked by tropical cyclones (TCs), and the accompanied storm surges are huge threats to coastal regions. In this study, numerical simulations of storm surges in the NECS are performed in the impacts of wave-induced surface drag (wave drag) and wave radiation stress (wave setup). The wave drag is estimated using a wave-steepness-dependent roughness parameterization. Comparisons with the observations reveal that the numerical simulations can be significantly improved by considering enhanced wave drag. The wave drag accounts for 15-22% increase in the peak storm surge in the southern coastal regions of the Bohai Sea, which is much more significant than the wave setup (accounting for less than 10% increase). Analysis with the wind and wave conditions shows that the significant impact of wave drag is attributed to the shoaling of young fetch-limited waves, which is accumulative toward the shoreline. The impact of different roughness parameterizations, such as wave-age-dependent scaling, is discussed. The results highlight the necessity of considering the influence of wave-enhanced surface drag on surge level in fetch-limited shoaling waters.