極端波浪(extreme wave)指的是在隨機波浪中，一波列中高度較高且不頻繁出現的波浪。本研究參照前人研究結果，將示性波高大於10公尺的波浪定義為極端波浪。過往許多極端波浪的研究多以遙測資料為主，本研究將以實測資料為主，透過分析極端波浪的特性與成因，建立出極端波浪的經驗公式，並推出極端波浪可能的最大值。
本研究蒐集全球各地的實測波浪資料庫，其中以美國NDBC波浪資料庫、以及台灣的波浪資料為主，建立出極端波浪資料庫，收錄接近400筆示性波高大於10公尺的波浪資料，其成因多颱風、颶風等熱帶氣旋所引起，佔極端波浪資料庫中的92%。
透過分析極端波浪的波齡值，本研究發現多數的極端波浪的主要成分皆為風浪，並透過與JONSWAP譜作套配，發現極端波浪多趨近於完全發展波。根據上述條件，利用Young and Vinoth (2013)與Hwang (2016)的颱風風浪經驗公式，比對公式估算值與實測資料的結果，無因次均方根誤差分別為29%與36%，並發現將實測資料帶入兩個公式時，需在風域的計算上做修正，本研究根據實測資料間風域變化，修正Young and Vinoth (2013)中的風域計算，提出等效風域修正係數用以提升經驗公式的計算準確度；根據本研究提出的修正公式，其估算值與實測資料間的誤差降為15%，顯示本研究的修正法能更加準確的估算極端波高。此外利用此修正公式與本研究中的颱風資料估算颱風期間產生的極端波高，其最大值可達到20.7米。

Extreme waves are ocean waves with exceptionally high amplitudes. In this study, waves with significant wave height exceeding 10 meters are defined as extreme waves. By analyzing the characteristics of extreme waves, an empirical formula is developed to estimate the maximum possible extreme wave height.
The study compiles a global database of in-situ wave measurements, with a focus on the US NDBC wave database and wave data from Taiwan. The extreme wave database includes nearly 400 records of waves with significant wave height exceeding 10 meters, with 92% of them being associated with tropical cyclones such as typhoons and hurricanes.
Analyzing the wave age values of extreme waves, the study finds that most extreme waves are primarily wind waves and tend to approach fully developed waves, as indicated by fitting the JONSWAP spectrum. When compared with Mitsuyasu (1975) directional distribution function, it was observed that the rate of wave energy decay with respect to angles is more gradual. Using the typhoon wind-wave empirical formulas proposed by Young and Vinoth (2013) and Hwang (2016) and comparing their estimations with the measured data, the dimensionless root mean square errors (NRMSE) are found to be 29% and 36%, respectively. It is noted that adjustments are required in the fetch calculations when applying these formulas to the measured data. Based on the variations observed in the fetch from the measured data, the study proposes an equivalent wind fetch correction coefficient to enhance the accuracy of the empirical formula. By incorporating this correction, the NRMSE between the estimated values and the measured data is reduced to 15%, demonstrating that the proposed correction method provides more accurate estimates of extreme wave heights. Moreover, using this corrected formula and typhoon data from this study, the estimated maximum extreme wave height during typhoon events can reach up to 20.7 meters.

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