台湾东北部地形共振对M2内潮演化影响的数值模拟研究

Effects of topographical resonance on the evolution of M2 internal tides northeast of Taiwan

正压潮流、突变海底地形和稳定层结结构是内潮生成的主要因素。台湾东北部海域地形结构多变,正压潮流较强,形成复杂的内潮场。本文通过ROMS(Regional Ocean Modeling System)模式,研究了台湾东北部海域两源区共振条件下内潮的生成、传播和耗散混合过程。结果表明:在台湾东北部海域,Mien-Hua海底峡谷与I-lan海脊是M2内潮重要的生成源区,源区之间的距离与M2内潮水平波长相当,满足共振条件并增强了内潮的生成和耗散。本文通过敏感性试验,探讨模式水平分辨率与不同季节的层化对源区共振过程的影响,数值实验表明,高分辨率的数值模式可以更好地刻画小尺度的地形结构,对复杂地形条件下内潮生成和传播过程的数值模拟十分必要;不同季节的海水层化结构在本质上不改变两源区间的共振关系,但层化强弱对内潮能量的生成具有一定程度的影响。

Barotropic tides,variable bottom topography,and vertical stratification are important factors influencing the generation of internal tides.Northeast of Taiwan,M2 internal tides are effectively generated over multiple and varying topographical features that form a complex wave field.In this study,we used the Regional Ocean Modeling System to investigate the generation,propagation,and dissipation of the M2 internal tides northeast of Taiwan.The results of our numerical experiments show that the distance between the I-Lan ridge and the Mien-Hua canyon is comparable to the wavelength of M2 internal tides.The barotropic–to–baroclinic energy conversion and dissipation associated with these two sources are effectively amplified by the resonance mechanism.We used sensitive numerical experiments to investigate other factors affecting the generation of M2 internal tides.A higher resolution model can better represent small-scale topographical features,which is important for simulating the distribution of the generation sites.The results also show that stratification influences the generation and propagation of internal tides whereas the effect of the resonance mechanism is negligible.