0908号台风“莫拉克”影响期间福建西沙湾海域台风浪的数值模拟

Numerical simulation of typhoon waves in the waters around Xisha Bay,Fujian during 0908 typhoon Morakot

联合SWAN模型和改进的椭圆型缓坡方程,结合考虑台湾海峡地形效应的改进藤田公式风场模型,建立了台湾海峡及近岸波浪场的数值嵌套模式.边界采用波谱离散驱动,模拟了0908号台风"莫拉克"期间台湾海峡波浪场的演变和崇武西沙湾浅水台风浪传播的物理过程.以实测数据进行单点验证表明,整个模拟过程风速的平均绝对误差为3.38 m/s,波高的平均绝对误差为0.30 m,计算结果较好地反映海峡内波浪对台风的响应过程."莫拉克"台风登陆台湾岛时,台湾海峡有效波高最大值为5.0 m;台风中心进入台湾海峡后,海峡东北部为巨浪到狂涛,有效波高最大值可达10.5 m.接近福建崇武沿岸时,偏E向台风浪向西沙湾内近岸传播,发生浅化、破碎、反射、绕射等变形现象,有效波高最大不足2 m,最小仅为0.2 m,波向趋于SE向,波峰线则趋于与峡湾岸线平行;崇武闽台贸易码头附近,大部分波浪受到阻挡作用发生反射,少部分发生绕射,使得码头以北水域波浪较小,有效波高仅为0.2～0.6 m,对湾内避风坞起到较好的保护作用.

Combining the SWAN model and the modified elliptic type mild-slope equation, the paper proposed the nested wave model of the Taiwan Strait and coastal waters, also included the wind field model based on a modified Fujita formula that considers the terrain effect of the Taiwan Strait. Using the driving of wave spectrum discretiza- tion, it could simulate the evolution of the wave field in the Taiwan Strait and the physical propagation processing of typhoon waves in the Chongwu Xisha Bay during the typhoon Morakot （0908）. Comparision with measured data showed that the mean absolute deviation of the wind in the whole simulation process was 3.38m/s, and that of the wave was 0. 30m, so the simulating results reflected the response of wave in the strait to typhoon well. Morakot land- ed on Taiwan with the maximum significant wave height of 5.0m in the strait. After the typhoon center moved into the strait, the waves of northeast strait became high or very high, and the maximum significant wave height was 10. 5m. Moreover, it occurred that shoaling, wave breaking, reflection, and diffraction when the typhoon center approached Chongwu and the east typhoon wave propagated into Xisha Bay, then the maximum significant wave height was less than 2m and the minimum value was 0.2m. While the wave direction turned into southeast, and the wave crest line approached to be parallel to the fjord coastline gradually. Owing to the blockade by the trade dock, most waves were reflected and a few waves were diffracted into the bay, making the wave around the north dock very small, with a significant wave height of only 0.2 to 0.6m, and it could protect the shelter port in inner bay to a relatively good extent.