南海北部M2内潮与中尺度涡能量的数值研究

Numerical Study About the Energy of M2 Internal Tides and Mesoscale Eddies in the Northern South China Sea

基于真实地形下的三维数值模拟结果,对南海北部的M2内潮、中尺度涡能量以及两者相互作用过程进行了研究。结果显示,M2内潮冬季稍强于夏季,在吕宋海峡生成的能量,冬季(12.2 GW)比夏季(11.6 GW)强5.2%,传入南海的能通量,冬季(4.2 GW)比夏季(3.8 GW)强10.5%,内潮能通量的空间分布在冬夏两季基本保持一致。中尺度涡的模拟结果显示,在南海内冷涡与暖涡个数相当(8个/a),冷涡的平均存活周期约为40 d,比暖涡的31 d长。当冷涡出现时,内潮非锁相部分的能通量大小及水平动能均出现明显增强现象,冷涡对内潮传播射线的汇聚作用是主要原因;M2内潮和中尺度涡相互作用期间可以激发或抑制高模态内潮,也存在无显著影响的情况。

Based on a three-dimensional numerical simulation with real topography,the M2 internal tides and mesoscale eddies energy in the northern South China Sea(SCS)as well as their interaction were studied.The results show that the M2 internal tides are slightly stronger in winter than in summer.For example,the generated energy of M2 internal tides in the Luzon Strait in winter(12.2 GW)is 5.2%stronger than that in summer(11.6 GW),and the M2 baroclinic energy flux into the SCS in winter(4.2 GW)is 10.5%stronger than that in summer(3.8 GW),although the spatial distribution of M2 baroclinic energy flux is basically the same in winter and summer.The simulation results of mesoscale eddies show that the number of cold eddies is equal to that of warm eddies(8/a)in the SCS,and the average lifetime of cold eddies(40 days)is longer than that of warm eddies(31 days).When the cold eddies appear in the sea,both the M2 internal tides incoherently baroclinic energy flux and incoherently horizontal kinetic energy are obviously enhanced,the prime reason is the convergence of M2 internal tide radiation ray by the cold eddies.The interaction between the internal tides and the mesoscale eddies can increase or decrease the higher-mode internal tides,or it may have little effect.