浙江沿海风暴潮增水对台风移速的响应研究

Study on the response of different moving speeds on storm surge in Zhejiang coastal waters

  • 摘要: 基于MIKE21建立东中国海-浙江沿海嵌套潮流模型,采用修正的Holland风场对1509号台风“Chan-hom”产生的风暴潮进行模拟,通过与实测数据对比验证表明该模型模拟结果合理可靠。基于验证模型,对1949—2020年间2个极端移速台风(低移速台风“Mary”和高移速台风“Kai-tak”)进行模拟分析,为剥离单一移速变量对增水的影响,以1509号台风“Chan-hom”为基础,设置3种台风移速(2倍移速、实际移速及50%移速)对风暴潮增水影响进行研究,得到如下结论:(1)低移速台风尽管登陆时强度低于高移速台风,但对浙江沿海海域的增水影响时间更长,台风“Kai-tak”增水0.5 m及以上的持续时间仅4 h,而“Mary”却长达12 h;(2)台风移速越慢,向岸风影响时间越长,舟山群岛以西至钱塘江海域的增水随着移速的减小呈上升趋势,杭州湾南岸具有较大洪水及内涝隐患;(3)在台风登陆点朱家尖,3种移速下的增水及风速相差不大,最大增水出现在台风登陆前风速最大时刻,而在舟山外海,增水大小受潮位波动影响呈现周期变化,低潮位时增水较大,高潮位时增水较小。

     

    Abstract: A nested tidal model for the East China Sea-Zhejiang coastal waters is built by use of MIKE21, to simulate the storm surge generated by typhoon “Chan-hom” based on Holland wind field model. The comparison of the numerical results and the field measurements shows that the simulated values are reasonable and reliable. Based on the verified model, two typhoons with extreme moving speeds (typhoon “Mary” and “Kai-tak” with low and high moving speeds, respectively) from 1949 to 2020 are simulated and analyzed. To investigate the influence of the moving speed, three different moving speeds (2.0, 1.0 and 0.5 times of the actual moving speed) are studied based on the typhoon case “Chan-hom”. The results show that (1) for the two typhoons with extreme moving speeds, although the landing intensity of low moving speed typhoon is lower than that of high moving speed typhoon, the former has a longer impact on the storm surge in the coastal waters of Zhejiang Province for low moving speed typhoon. The duration of 0.5 m or above water level increase is only 4 h for “Kai-tak”, while for “Mary” the duration of the same water level increase is 12 h. (2) for the three different moving speeds, when the moving speed is slower, the wind direction points to the shore for a longer time, which makes the water level in the area from the west of Zhoushan sea area to the Qiantang River increase due to the decrease of the moving speed. (3) The field data from Zhujiajian observing point shows that the maximum increase of the water level appears as the wind speed reaches the maximum value before landing. There is little difference in the water level increase under the three different moving speeds. At the Zhoushan offshore observing point, the water level changes periodically with the tide level. The water increase is larger at the low tide level, while it is smaller at the high tide level.

     

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