湧浪(Swell)又稱為長浪，其能量消散慢因此可以在海上傳遞相當長的距離，而其週期長、動量大的特性則會令湧浪傳遞至海岸邊時有顯著的破壞力，容易造成結構物受損或激起巨大水花(瘋狗浪)，危害岸邊活動民眾。本研究針對台灣周遭海域觀測到的湧浪進行分析，發現其在地域與季節上有差異，資料分析顯示，颱風前後均會傳來湧浪，颱風離開後傳來的湧浪，其波高較颱風前傳來者大了約40%，影響時長也為颱風前傳來者的3倍，顯示颱風離開後的湧浪對海岸衝擊更大。湧浪不僅出現在颱風前後，季風期間亦常出現湧浪，東北季風引起的湧浪影響時長甚至會長達100小時以上，影響程度不容忽視。近年來，中央氣象局有針對湧(長)浪提出警戒，本研究發現，在長浪警戒發布期間，瘋狗浪實際發生的比率有29%；而非長浪警戒期間，瘋狗浪發生比率為11%；此外也發現湧浪能量越大其BFI值越高，顯示湧浪傳入到近岸區域會增加波浪非線性程度。在瘋狗浪發生時湧浪波高分析發現，瘋狗浪發生時平均湧浪波高為平常時的1.62倍，顯示湧(長)浪是造成瘋狗浪的重要因素之一，但並非為唯一影響因子。本研究還發現，在非長浪警戒期間，若發生瘋狗浪，其通常為單一出現，而在長浪警戒期間，瘋狗浪在一小時內出現超過一次以上機率占80%以上。最後本研究透過風湧浪分離方法，獲得湧浪頻譜，以JONSWAP波譜模型套配有良好的結果，並分別得到颱風期間與季風期間平均湧浪譜模型參數，可進一步作為工程評估之用。

Swell with the characteristic of low energy dissipation can propagate for a long distance. The characteristics of long period and large momentum will make the swell have significant destructive power when it is transmitted to the coast. It is easy to cause structural damage or provoke huge splashes (coastal freak wave), harming the people on the shore. This study analyzes the swells around Taiwan waters. Data analysis shows that swells are transmitted before and after the typhoon. After the typhoon leaves, the swell height is about 40% greater before the typhoon. The impacted period of the swell is also three times as much as that before the typhoon. The typhoon swell impact on coast during typhoon left is more significant than during typhoon coming. Moreover, swell induced by monsoon was found in this study. The impacted period of monsoon swell is up to 100 hours in specific case. It shows that the influence of swells during the monsoon cannot be ignored, and it had the different characteristics from typhoon swells. For example, the swell wave height and swell peak period during the typhoon are larger than those during the monsoon, and monsoon had the longer impacted period. In recent years, the Central Meteorological Administration has warned against long waves. This study found that during the warning time, the occurred rate of the coastal freak waves(CFW) is 29%. And the rate during the non-warning time is 11%. In addition, it is also found that the Benjamin-Feir Index (BFI) is directly proportional to the swell energy. It shows that the contraction of swells to the nearshore area will increase the wave nonlinearity. The average swell height during CFW occurred is 1.62 times than usual, shows that swells are one of the important factors causing CFWs. Furthermore, CFWs occurred more than once per hour during the warning time. At last, in this study obtain the parameters of the average swell spectrum model during typhoon and monsoon respectively. The parameters can be used for engineering assessment in the future.

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