在隨機海洋中，海浪經常是由風浪及湧浪混合而組成。從海洋現場觀測之波浪頻譜中分離出風浪和湧浪的成份，對於波浪理論研究、海浪預報及近岸與離岸工程實務上都有重要之意義。過去風湧浪分離之研究主要從一維波譜進行，然而，風浪或湧浪的判別必須考慮風向和波向之關係，因此，從二維方向波譜來分離風浪和湧浪在物理上更顯合理。Hanson and Phillips (2001)提出了一個基於方向波譜的風湧浪分離方法大致上均可獲得正確結果，NWWIII波浪模式亦採用其方法。然而，本研究發現了Hanson and Phillips (2001)的方法在大風速的情形下高估了風浪成分，這是由於該法假設了無限吹風延時與無限風域的緣故。本文提出一個考慮吹風延時的風湧浪分離修正方法，稱為有限吹風延時法，此方法是基於風浪成長理論所提出。本文選擇了12筆各式氣象、海象條件下的方法波譜進行驗證，分析結果顯示本文的分離結果合理，分離所得的風浪成分符合風浪成長關係式，分離的結果還透過波浪尖銳度分布的檢測與能譜時序列演變的判別，都證實了本文分析結果正確。

The coexistence of wind wave and swell often occurs in the sea. It is necessary to separate wind wave and swell components for engineering design and hazard warnings. Swell separation using a frequency spectrum (1D) was originally proposed and useful. However, the separation of wind wave and swell should consider the misalignment between wave and wind directions. A separation approach based on a directional spectrum (2D) is essential. Hanson and Phillips (2001) proposed a 2D separation method, that has been widely applied, such as being adopted in the WaveWatch III model, and most of the separation results are correct. However, this study found that this may overestimate wind sea energy under strong wind conditions because their method essentially assumed unlimited wind fetch and duration. This study proposed a modification to reflect wind duration when separating wind wave and swell. We used 12 typical directional wave spectra in various marine weather conditions for validation. The wind wave and swell separation by our proposed method obtained reasonable results. The wind wave component is verified to satisfy the wind-generated wave growth function. In addition, the results were re-verified when studying their steepness distribution and spectrum time series.

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