On the Sensitivity of Typhoon Wave Simulations to Tidal Elevation and Current

Shih-Chun Hsiao,Lee-Yaw Lin,Wei-Bo Chen,Han-Lun Wu,Chih-Hsin Chang

doi:10.3390/jmse8090731

Abstract

The sensitivity of storm wave simulations to storm tides and tidal currents was investigated using a high-resolution, unstructured-grid, coupled circulation-wave model (Semi-implicit Cross-scale Hydroscience Integrated System Model Wind Wave Model version III (SCHISM-WWM-III)) driven by two typhoon events (Typhoons Soudelor and Megi) impacting the northeastern coast of Taiwan. Hourly wind fields were acquired from a fifth-generation global atmospheric reanalysis (ERA5) and were used as meteorological conditions for the circulation-wave model after direct modification (MERA5). The large typhoon-induced waves derived from SCHISM-WWM-III were significantly improved with the MERA5 winds, and the peak wave height was increased by 1.0–2.0 m. A series of numerical experiments were conducted with SCHISM-WWM-II and MERA5 to explore the responses of typhoon wave simulations to tidal elevation and current. The results demonstrate that the simulated significant wave height, mean wave period and wave direction for a wave buoy in the outer region of the typhoon are more sensitive to the tidal current but less sensitive to the tidal elevation than those for a wave buoy moored in the inner region of the typhoon. This study suggests that the inclusion of the tidal current and elevation could be more important for typhoon wave modeling in sea areas with larger tidal ranges and higher tidal currents. Additionally, the suitable modification of the typhoon winds from a global atmospheric reanalysis is necessary for the accurate simulation of storm waves over the entire region of a typhoon.

Highlights

Extreme waves and storm surges resulting from typhoons are usually regarded as destructive disasters that present a great hazard to navigational safety and coastal and nearshore infrastructures and can flood low-lying areas along the coast [1,2,3]
The wind speeds at 10 m above the sea surface and the sea-level pressures during Typhoon Soudelor from 1–15 August in 2015 as extracted from ERA5 served as atmospheric forcing for scale Hydroscience Integrated System Model (SCHISM)-Wind Wave Model version III (WWM-III)
The ERA5 winds were modified using the direct modification method expressed in Equation (12), and the typhoon winds derived from modified ERA5 (MERA5) were imposed in SCHISM-WWM-III to compare the resulting storm wave simulation performance with that achieved using the ERA5 winds

Summary

Introduction

Extreme waves and storm surges resulting from typhoons are usually regarded as destructive disasters that present a great hazard to navigational safety and coastal and nearshore infrastructures and can flood low-lying areas along the coast [1,2,3]. To mitigate the disaster risk in both nearshore and coastal regions, many researchers have put considerable effort into the improvement of storm wave and storm surge modeling [2,3,4]. To achieve this goal, it is important to enhance the predictive capabilities of the typhoon storm surge and wave models used for emergency preparedness and risk evaluation. The contributions of waves to a storm surge or storm tide through radiation-stress-induced forces can be examined by coupling a circulation model with a wave model [9,10]. A comprehensive understanding of the interactions between storm waves, tidal current, and tidal elevation would be of great interest to coastal and ocean engineers and oceanographers

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Conclusion