The role of sea surface drag in a coupled surge and wave model for Typhoon Haiyan 2013
The role of sea surface drag in a coupled surge and wave model for Typhoon Haiyan 2013
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DOI：
10.1016/j.ocemod.2015.06.004
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发表时间：
2015-12
期刊：
影响因子：
3.2
通讯作者：
Sooyoul Kim;N. Mori;H. Mase;T. Yasuda
中科院分区：
文献类型：
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作者：
Sooyoul Kim;N. Mori;H. Mase;T. Yasuda
本文利用涌浪耦合模式，研究了风速限制的波浪相关阻力系数(CD)对2013年登陆菲律宾莱特湾沿岸的超强台风“海燕”的涌浪产生的影响。此外，我们还考察了出现最大风速的半径(Rmax)的变化对风速的影响。由于缺乏观测数据，在使用参数风压模式时，准确确定这一半径对海燕风压场至关重要。计算结果表明，半径在40~50公里范围内，随着半径的变窄，涌浪和波高减小。我们对浪涌和波浪能级的计算使用了Janssen方法的修正版本(Janssen，1989,1991)，并采用阶跃函数来使CD在指数波增长项中趋于平稳。在目前的方法中，风速被限制在一定的阈值内；在该值以下，用对数风廓线估计有效粗糙度。用新的修正方法，研究了大风限速波浪相关阻力CD(<；70m/S)对海燕涌浪和海浪高度的影响。当Rmax=50 km时，在25m/S处使CD平坦，在涌浪高度(6.5m)和波高(海湾内外分别为7m和17m)方面与测量资料有很好的一致性。数值试验表明，风速在25-30m/S范围内的平坦化可以较准确地预报海燕风暴潮和浪涌耦合模式中的波浪场。研究表明，本文提出的风速在25-30m/S风速范围内平坦的方法在浪涌耦合模式中适用于超强台风条件。
The present study investigates how the wind speed-limited wave dependent drag coefficient (C D) influences the surge and wave generation of Super Typhoon Haiyan, which struck the coasts of the Leyte Gulf, in the Philippines (2013), using a coupled surge and wave model. In addition, we examine the effect of changes of the radius (R max) at which the maximum wind speed occurs. Accurate determination of this radius is crucial to the Haiyan wind and pressure field when using a parametric wind and pressure model because of lack of observation data. The calculation results show that the radius ranges from 40 km to 50 km: as the radius becomes narrower, the surge and wave heights are reduced. Our calculation of surge and wave levels uses a modified version of Janssen’method (Janssen, 1989, 1991) with a step function applied to level off C D in the exponential wave growth term. In the present method, the wind speeds are limited to a certain threshold; below this value the effective roughness is estimated with a logarithmic wind profile. With the newly modified method, we investigate the effect of the wind speed-limited wave dependent drag C D for high winds (< 70 m/s) on the Haiyan surge and wave levels. When leveling off C D at 25 m/s for R max= 50 km good agreement with survey data is obtained in terms of surge level (6.5 m) and wave heights (7 m and 17 m inside and outside of the gulf). The numerical experiments suggest that leveling off at wind speeds of 25–30 m/s results in the accurate prediction of Haiyan storm surge and wave levels in the coupled surge and wave model. The study demonstrates the applicability of the present method of leveling off at wind speeds of 25–30 m/s in a coupled surge and wave model for super typhoon conditions.