南海西北陆坡区内潮与近惯性内波观测研究

通过对2006年南海西北部海域近3个月的全水深流速观测资料的分析，研究了该海区正压潮、内潮及近惯性内波的时空分布特征。结果表明，全日内潮明显强于半日内潮，且最大潮流均出现在海洋上层；内潮的主轴方向基本沿东南-西北方向，近似与局地等深线垂直；内潮能量显示出明显的时间长度约为半月的大小潮调制周期；全日内潮的coherent部分占全日内潮能量的70%，而半日内潮的coherent部分占半日内潮能量的53%；进一步研究发现半日内潮主要由第一模态主导，而全日内潮第三模态能量占总能量的比例仅次于第一模态且量值上与之相当；强风过程可激发出强的近惯性运动，暖涡使得近惯性内波能量更有效地向海洋深层传播，冷涡则不利于近惯性内波能量向下传播。

Observation of internal tides and near-inertial internal waves on the continental slope in the northwestern South China Sea

The temporal variability and vertical distribution of barotropic tides, internal tides and near-inertial internal waves (NIW) were investigated on the basis of 3-month moored acoustic Doppler current profiler observations on the continental slope in the northwestern South China Sea in 2006. The diurnal baroclinic constituents are found to be more prominent than the semidiurnal baroclinic ones at mooring site, which are same with the barotropic tides, and amplitudes of the internal tides are stronger in the thermocline, and then decreases with depth. Almost all the major axes of the internal tidal ellipses are perpendicular to the local isobaths, that is, along the southeast-northwest direction approximately. Spring-neap oscillations of about 14 days can be seen at mooring site during observational periods. The coherent diurnal (semidiurnal) internal tidal motions could explain 70% (53%) of the total energy in the diurnal (semidiurnal) tidal band. Further analysis demonstrates that the semidiurnal internal tides are dominated by the first mode, whereas the diurnal internal tides show a variable multimodal structure:the third mode plays a secondary role and is comparable to the first mode. During the passage of Typhoon, the NIW became more energetic. Mesoscale warm eddies are the chimneys through which the near-inertial wind work penetrates rapidly into the deep ocean, and then cold eddies could probably inhibit the downward propagation of the near-inertial wind work.