Typhoon-Induced Ocean Waves and Stokes Drift: A Case Study of Typhoon Mangkhut (2018)

Ocean waves and Stokes drift are generated by typhoons. This study investigated the characteristics of ocean waves and wave-induced Stokes drift and their effects during Typhoon Mangkhut using European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 datasets and observational data. The results revealed that the typhoon generated intense cyclones and huge typhoon waves with a maximum wind speed of 45 m/s, a minimum pressure of 955 hPa, and a maximum significant wave height of 12 m. The Stokes drift caused by typhoon waves exceeded 0.6 m/s, the Stokes depth scale exceeded 18 m, and the maximum Stokes transport reached 6 m2/s. The spatial distribution of 10-m wind speed, typhoon wave height, Stokes drift, Stokes depth, and Stokes transport during the typhoon was highly correlated with the typhoon track. The distribution along the typhoon track showed significant zonal asymmetry, with greater intensity on the right side of the typhoon track than on the left side. These findings provide important insights into the impact of typhoons on ocean waves and Stokes drift, thus improving our understanding of the interactions between typhoons and the ocean environment. This study also investigated the contribution of Stokes transport to the total net transport during typhoons using Ekman-Stokes Numbers as a comparative measure. The results indicated that the ratio of Stokes transport to the total net transport reached up to 50% within the typhoon radius, while it was approximately 30% outside the radius. Strong Stokes transport induced by typhoon waves led to divergence in the transport direction, which resulted in upwelling of the lower ocean as a compensation current. Thus, Stokes transport played a crucial role in the vertical mixing of the ocean during typhoons. The findings suggested that Stokes transport should be paid more attention to, particularly in high latitude ocean regions, where strong winds can amplify its effects.