全南海内潮生成与传播的数值模拟研究

Modelling of Internal Tides Originating and Propagating in the South China Sea

利用边界八分潮驱动的MITgcm模式,对整个南海海区的内潮进行了数值模拟研究。结果表明:在吕宋海峡出现因内潮引起的强烈等密面起伏,其振幅可以达到30m;在西沙群岛西侧海域和南海南部陆架、陆坡坡折处也出现因内潮引起的小振幅等密面起伏,振幅可达到10m以上,这表明该两处海域也是南海内潮的可能源地。通过断面分析,验证了西沙群岛西侧海域和南海南部陆架、陆坡坡折处均有内潮射线产生。内潮能通量的分析表明,吕宋海峡处大潮期间东传的平均斜压潮能功率为11.4GW,西传的斜压潮能功率为14.6GW;在西沙群岛西侧海域,东南方向传播的斜压潮能功率为0.28GW,西北方向传播的斜压潮能功率为0.08GW;在西沙群岛西侧海域和南海南部陆架、陆坡坡折处海域的斜压潮能通量的量级可达20kW/m。在南海南部陆架、陆坡坡折处海域,东北方向传播的内潮能通量为0.54GW。通过分析上述三个典型海域内潮能通量的时间序列发现,第一模态内潮在吕宋海峡的传播相速度可达3.1m/s,在南海中部的传播速度可达2.2m/s;在上述三处内潮源地均有高模态内潮产生。

In this paper,relying on the boundary eight-tides drive,the model MITgcm is used to make a numerical simulation of the whole of the south China sea of internal tides.The results show that there are strong vertical isopycnal displacement accompanied by internal tide in the Luzon Strait,and its amplitude can reach 30 mand propagate in the east-west direction.At the same time,small amplitude is also found in the west coast of the Xisha Islands and the southern shelf-slope of the South China Sea,and its amplitude can reach 10 myet.These vertical isopycnal displacements indicate that the two areas are also possible generated sources of internal tide in the South China Sea.Cross-section analysis shows that both the west coast of the Xisha Islands and the southern shelf-slope of the South China Sea have internal tide-ray generation.Based on the analysis of the internal tidal flux,we find that the baroclinic tidal energy flux in the east of the Luzon Strait reaches 11.4 GW,while that in the west reaches 14.6 GW.In the west of the Xisha Islands,the internal tidal energy fluxes in the southeastern direction is 0.28 GW,while in the northwestern direction is 0.08 GW.The magnitude of the internal tidal energy flux in the west coast of the Xisha Islands and the southern shelf-slope of the South China Sea is 20 kW/m.In the southern shelf-slope of the South China Sea,the internal tidal flux is 0.54 GW.By observing the time series of tidal energy fluxes in each region,it is found that the velocity of tidal energy flux in the Luzon Strait can reach 3.1 m/s,and the propagation velocity can reach 2.2 m/s in the middle of the South China Sea.High modes of internal tide were generated in the above three generated sources.