Quantitative evaluation of the exchange processes of momentum and seawater associated with Kuroshio frontal waves

首先，一个两层的数值模式被用来调查大陆架环流迫使沿沿着陆架边缘的西部边界流。经过长期积分，模式达到平衡状态，在大陆架上发现长期平均流的交替带。西边界流伴随着锋面波，由于扩散拉伸作用，产生垂直动量传递。地形Rossby波在陆架斜坡上由垂直动量传递激发。此后，波的能量通过共振相互作用继续流向较低频率极限。沿陆架波数也为零，以满足地形Rossby波的频散关系。其次，利用1998-2001年5月的观测结果，结合数值模式，探讨了东海陆架边缘黑潮次表层海水盐度偏低的可能原因。观测结果表明，5月份在24.5 σ_θ等密度面以上的地层中，总是出现低盐水的次表层侵入，而在黑潮锋面涡（或波）的波谷附近则出现盐度逆温。数值模拟结果表明，当锋面波捕获低盐度水时，由于斜压不稳定性的影响，锋面波中的等盐线在上下层之间存在相位滞后，陆架水在槽中以盐度逆温的形式存在。该研究还为河流的膨胀提供了物理解释，通过进行数值实验，其中河流羽流是由沿海淡水源引起的。

First, a two-layer numerical model is used to investigate the continental-shelf circulation forced by western boundary currents along shelf edges. After long-term integration, the model reaches the equilibrium state in which alternating bands of long-term mean currents are found over the continental shelf. The western boundary current is accompanied by frontal waves, and so vertical momentum transfer occurs because of to the diffusive stretching. Topographic Rossby waves are excited on the shelf slope by the vertical momentum transfer. Thereafter, energy of the waves proceeds to flow toward the lower-frequency limit by resonant interactions. The along-shelf wavenumber also vanishes to satisfy the dispersion relation of the topographic Rossby wave. As a consequence, the alternating bands of mean current are found over the continental shelf.Second, the possible origin and cause of the less saline shelf water detected in the Kuroshio subsurface layer around the shelf edge of the East China Sea are investigated using observational results obtained in May 1998-2001 in conjunction with a numerical model. The observations show that subsurface intrusions of less saline water are always detected in May in layers above 24.5 σ_θ isopycnal surface, and that salinity inversions are detected around the trough of the Kuroshio frontal eddy (or wave). Numerical models demonstrate that, when the frontal wave captures the less saline water, the shelf water takes the form of a salinity inversion in the trough because isohalines in the frontal wave have a phase lag between the upper and lower layers in consequence of the baroclinic instability.Third, this study also provides a physical interpretation for the ballooning of river-plume bulges by conducting numerical experiments in which a river plume is induced by a coastal freshwater source.