“纳沙”台风期间广西白龙尾近岸海域余流特征及产生机制

Characteristics and Formation Mechanism of the Residual Current in the Coastal Waters of Bailongwei during the Nesat Typhoon

关键词:  余流特征  产生机制  白龙尾海域

Key words:  residual current  formation mechanism  Bailongwei waters

摘要:

[目的]研究"纳沙"台风影响期间广西白龙尾近岸海域余流特征及产生机制,为探讨台风作用下近岸余流的变形和强化提供理论依据。[方法]根据"纳沙"台风期间,广西白龙尾近岸一定点S1站的高分辨率连续实测海流剖面资料,对该观测点各层实测流速流向特征和余流流动特点进行研究。[结果]在无台风期间,观测点各层的余流流速一般小于10 cm/s,表层的余流流速平均值为5.7 cm/s,中层为3.5 cm/s,底层为3.1 cm/s。最大余流流速,表层为16.3 cm/s、中层为14.2 cm/s、底层为12.0 cm/s。在台风登陆期间,观测点表、中、底层最大余流流速分别为39.7 cm/s、32.4 cm/s和20.7 cm/s,最大流速值可达60.9 cm/s,超出正常值3倍以上。随着水深深度的增加,风应力对水体的作用迅速减小,底层低频流流速最大值仅为31.1 cm/s。从余流流向分级图可以看出:无台风期间,表层余流流向为WSW向,中层以下流向为NE向,台风登陆期间,余流流向为SW向。[结论]余流流速大小与方向的变化与风、补偿流、地形有密切关系。

Abstract:

[Objective] To study the characteristics and formation mechanism of the residual current in the coastal waters of Bailongwei during the Nesat Typhoon can provide theoretical basis for the deformation and strengthening of the offshore residual current under the effect of typhoon.[Methods] According to the high resolution continuous current profile data measured on S1 station during the "Nesat" typhoon, which was located in the coastal area of the Guangxi Bailongwei, the characteristics of the measured current velocity and direction at each layer and the characteristics of the residual current of the observation point were studied.[Results] In the period of no typhoon, the residual current velocity at each layer was generally less than 10 cm/s.The average residual current velocities of the surface layer, the middle layer and the bottom layer were 5.7 cm/s, 3.5 cm/s and 3.1 cm/s, respectively.The maximum residual current velocity of the surface layer was 16.3 cm/s, the middle layer was 14.2 cm/s and the bottom layer was 12.0 cm/s.During the landing of the typhoon, the maximum velocities of the residual current were 39.7 cm/s at surface layer, 32.4 cm/s at the middle layer and 20.7 cm/s at the bottom layer.The maximum velocity was up to 60.9 cm/s, which was more than three times over the normal value.With the increasing of the water depth, the effect of the wind stress on the water reduced rapidly, the maximum velocity of the low frequency current was only 31.1 cm/s at the bottom layer.The classification diagrams of the residual current velocity showed that the direction of the residual current was WSW direction at the surface layer and the direction below the middle layer was NE without typhoon, while the residual current direction was SW during typhoon.[Conclusion] The variation of the velocity and direction of the residual current was closely related to the wind, the compensation current and the terrain.