Impacts of Binary-interacted Typhoons Tembin and Bolaven in 2012 on Surges and Waves over the East China Sea

Typhoon-induced storm surges and waves are highly related with typhoon track and associated wind stresses and atmospheric pressures at sea surface. The effects of binary interaction may alter typhoon tracks and even forward speed, which might influence waves and surge heights in the ocean. In the present study, we execute a series of numerical experiments to investigate how isolated and binary typhoons would impact the ocean waves and generated surges offshore and nearshore. The responses of binary typhoons to sea level rise and land subsidence are also discussed. The Typhoon Tembin and Typhoon Bolaven influenced the East China Sea with equivalent intensity of tropical storm and Category 2, respectively, on the Saffir–Simpson hurricane wind scale. The Weather Research and Forecasting (WRF) model is utilized to hindcast the layered wind and atmospheric pressure fields above sea/land surface. Two synthetic scenarios isolating these individual typhoons are designed to investigate the potential impacts of the binary-interacted typhoons. By coupling with the SCHISM–WWMIII modelling system, the corresponding surge–tide–wave processes are solved and validated with measurements at tidal gauge and wave buoy stations. At the same time, The spatial-varied future relative sea level rise (RSLR) by the end of the century is projected from satellite altimeter data-based sea level analysis and is adjusted for the influence of the Glacial Isostatic Adjustment (GIA) using the ICE-6G/VM5a model. The results indicate that the surge and wave heights induced by these two typhoons were not exacerbated significantly, as the hours influencing the Yellow Sea by Typhoon Tembin were about 30 hours later than Typhoon Bolaven. We also present the spatial distribution of nonlinear responses of storm surge induced extreme sea levels to RSLR, implicating the regions of exacerbation and attenuation, respectively, due to future sea level trend. The present study helps identifying distribution patterns by binary-interacted typhoons and enhancing assessment accuracy of potential coastal hazards and flood risk.