| Summary: | Super Typhoons Maria (2018) and Lekima (2019) were adopted for this case study, although they only passed the northern offshore waters of Taiwan without making landfall. A direct modification technique was employed to create the atmospheric conditions for a wave-circulation model to hindcast large typhoon-driven waves. The radius of the modified scale (<i>R<sub>trs</sub></i>) for a hybrid typhoon wind plays an important role in the significant wave height (SWH) simulations during the passage of typhoons. The maximum increment in peak SWH reached 3.0 m and 5.0 m in the deep ocean for Super Typhoons Maria (2018) and Lekima (2019), respectively if the <i>R<sub>trs</sub></i> was increased from 4 × <i>R<sub>max</sub></i> (radius of the maximum wind) to 7 × <i>R<sub>max</sub></i>. The SWHs induced by the typhoon winds in the surf zone were more sensitive to different wave-breaking formulations used in the wave-circulation model. The maximum difference in peak SWH reached 2.5 m and 1.2 m for Super Typhoons Maria (2018) and Lekima (2019), respectively, when the wave-breaking formulations of BJ78 (proposed by Battjes and Janssen in 1978) and CT93 (proposed by Church and Thornton in 1993) were introduced to the wave-circulation model. The SWH simulations in the surf zone were insensitive to the wave-breaking criterion (<i>γ</i>) during the passage of typhoons. In shallow nearshore waters, the utilization of a constant <i>γ</i> for the wave-circulation model always produces peak SWHs that are smaller than those using <i>γ</i> based on local steepness or peak steepness.
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