台风“马鞍”影响北部湾水动力的数值模拟分析

Numerical Simulation Analysis of the Influence of Typhoon Ma-on on the Water Dynamics of Beibu Gulf

关键词:  台风  风暴潮  近岸西向流  FVCOM  北部湾

Key words:  Typhoon  storm surge  western current in coastal area  Beibu Gulf  FVCOM

摘要:

影响和登陆北部湾北部的台风，对其近岸海洋动力环境产生的影响不容忽视。本研究基于防城港近海实测潮位与海流数据，利用水动力模型FVCOM构建了北部湾三维风暴潮数值模型，模拟了台风“马鞍”期间北部湾近岸水动力环境变化。模拟结果表明，风暴潮最大增水为78 cm，此后水位出现一次增水振幅为25 cm的余震动；台风过境期间，北部湾近岸余流从表到底由东北向转变为西南向，流速迅速增大，出现西向风暴射流，强流区的流核主要分布在距离近岸 0~20 km之间、 10 m 水深以内的海域，且基本沿着 10 m 等深线分布。通过对动量方程各项的分析发现，正压梯度力项、时间变化项、水平对流项以及垂直扩散项变化显著，其中，正压梯度力变化是近岸西向风暴射流产生的重要因素之一。研究结果为近海生态环境保护提供了重要的理论依据。

Abstract:

Typhoons affecting and landing in the northern of Beibu Gulf, rendered their consequential influence on the proximal hydrodynamic milieu incontestably substantial and exigent for thorough consideration. Based on the observation of tide level and current in Fangchenggang, a three-dimensional numerical model of the Beibu Gulf was constructed to simulate the variation of the coastal hydrodynamic environment during Typhoon "Ma-on" , which combined with the hydrodynamic model FVCOM and Ueno Takeo typhoon wind field model. The results showed that the maximum storm surge elevation simulated by the model was 78 cm, and then there was a residual vibration of the water level, with increase water level was 25 cm. The variation of the direction of the residual current from surface to bottom in the coastal sea area of Beibu Gulf was from northeast to southwest, with a rapid increase in velocity and the appearance of the westward storm jet. The flow core of the strong westward storm jet was distributed between 0~20 km and within 10 m depth in the coastal sea area. The analysis of the momentum equation showed that barotropic pressure gradient, time variation, horizontal advection and vertical diffusion changed significantly, and the variation of positive pressure gradient force was one of the important factors causing the formation of westward storm jet in the coastal area. The research results could provide an important theoretical basis for the study of the variation of the storm surge in the Beibu Gulf and the protection of coastal ecological environment.