珠江口伶仃洋风暴潮传播特性及影响因素数值模拟研究——以台风“山竹”为例

Simulation of storm surge and analysis of the factors around Lingdingyang Bay, Pearl River Estuary: Take typhoon Mangkhut as an example

中文关键词:  风暴潮  数值模拟  台风  伶仃洋

英文关键词:storm surge  numerical model  typhoon  Lingdingyang

中文摘要:

      基于FVCOM海洋模式对珠江口伶仃洋内及周边海域的风暴潮增水传播过程进行研究。首先建立珠江口河口风暴潮模型，采用超强台风“山竹”作为典型案例进行风暴潮过程模拟，对模型的计算结果进行验证，发现模型通过率定后结果和测站潮位结果比较吻合。然后对伶仃洋在“山竹”登陆前后的风暴潮增水过程的时空分布及变化特征进行分析。从伶仃洋湾口到湾顶取了12个点进行时间序列分析，发现除了因距离外海远近不同导致的相位差异外，基本特征相似，符合国际上类似海湾内的风暴潮增水波动特征，可分为初震段、主震段和余震段。为了进一步研究台风参数差异对伶仃洋风暴潮增水的影响，本文基于“山竹”超强台风的特征参数，设计了一系列变化条件下的数值试验，发现：(1)台风的登陆时间会影响到风暴潮增水和天文潮之间的相位关系，进而影响到增水的大小。基本规律是如果风暴潮增水极值正好在天文潮高潮位，风暴潮增水就会削弱。相反风暴潮增水正好在天文潮低潮位，风暴潮增水就会增强；(2)台风中心压差决定了台风风力的大小，从而影响风暴潮增水。但是在同一海湾内的影响在空间上并不是相同的，在较浅区域影响大而较深区域影响小；(3)台风的路径会对风暴潮增水产生较大影响。基于“山竹”的路径，如果往西平移，会导致湾内增水上升段前移，而如果往东平移，会引起湾内增水下降的延迟。在同样的登陆点，当台风行进路线和海岸线之间的夹角较小时，会增强伶仃洋内的风暴潮增水。

英文摘要:

      A numerical study based on FVCOM model was carried out to investigate the storm surge behavior induced by Typhoon Mangkhut in and around Lingdingyang Bay, Pearl River Estuary. Through elaborate calibration, the simulation results matched well with the measurements on the tidal-gauge stations. The validated Typhoon Mangkhut simulation was used to study spatial and temporal behavior of the storm surge. Specifically, hourly spatial distribution of surge evolvement before the typhoon landfall and the time series of the surge from twelve location points in and around Lingdingyang Bay were chosen for analysis. Moreover, a series of artificial typhoons were designed by shifting some parameters of the original typhoon including the landfall time, central pressure deficit, landfall location and moving direction, to study the influence mechanism caused by the typhoon uncertainties. Results show that the influence mechanism by landfall time is dominated by the rule of tide-surge interaction, which supports the lowest surge on the tidal high level and vice versa. It also shows that the response of the surge to the same shift of the pressure deficit for a typhoon is uneven in space, more sensitive near the shallow coast and less in the deep sea. Though shifting and rotating the track of the original typhoon, we find that a west shift of the track makes the ascending surge advanced and an east shift of the track makes the receding surge delayed. A decrease of the angle between the coast and the moving direction can enlarge the maximum surge and an increase of the angle induces the opposite result. This research helps us improve our understanding of how a typical northwesterly moving typhoon-induced storm surge behaves in the coastal regions near the Lingdingyang Bay and Pearl River Estuary.