锋面通过台湾海峡时引起的快速成长波高推算

HINDCASTING THE RISING WAVE HEIGHT GENERATED BY A FRONT IN TAIWAN STRAIT

每年冬季因中国北方冷空气前缘东移出海南下而形成的锋面是造成台湾海峡内恶劣海况的原因之一,锋面的到临常引发快速增高的波浪,这种海况是目前作业化数值预报模式在操作上不易反映的。经验证明根据元素波模式推衍所得的面积风域法推算波浪,适合于推导季风期间海况的一种方法。本文将锋面期间风域是移动的特性结合面积风域理论,作为推算锋面抵达时推算波高的方法。本文提出加权风场内插法计算各时刻各网格点的风速,使得面积风域理论简化为在网格点的离散计算。文中根据锋面期间实际观测数据计算波能传播速率与风能传授系数等参数,经由案例分析的结果显示这个离散化面积风域法可以合理地推算锋面期间快速成长的波高。

The sea state is strongly affected by the cold front that comes from northern of China during winter season. Waves may grow quickly in a short time with the arrival of a front. Such rapid change of sea state is difficult to be forecasted accurately by operational wave models. The Fetch Area Method (FAM) that derived from elementary waves theory was identified reasonable wave prediction during general winter monsoon season. In this study, the concept of moving fetch of a front is included to modify the formula. A weighted wind interpolation method (WIM) is developed to interpolate the wind vector at all grid in the space domain, in order to discrete the calculation. The parameters of wind power transfer parameter and representative group velocity factor are found from field observations. A typical case of wave generation during front passage is used to verify the presented model showing a reasonable result of the growing wave height.