Numerical Simulation Study Of M₂ Internal Tides Generation And Propagation In The Luzon Strait

Internal tide is a important oceanographic phenomena which is a weakly nonlinear tide-generated internal waves.The Luzon Strait is primary deep passage connecting South China Sea (SCS) to the northwest Pacific Ocean and blocked by two meridional ridges at depths that are the Luzon islandarc and Hengchun searidge. M2 Barotropic tides propagate predominantly westward from the Pacific Ocean,impinge on two merdional ridges,and generate vigorous internal tides.In this arcticle, with introduction of the so-called internal-tide vicosity and some amendment of the parameters,the z-coordinate primitive-equations ocean model HAMSOM is used to simulate the M2 internal tides generation and propagation in the Luzon Strait. The results show that:(1)The amplitude upper 250m of the M2 internal tides generated in the Luzon strait is maximum at the thermocline. The internal tides near island slopes is stronger than the other areas and the maximum amplitude there is about 40m.(2)The island slope areas in the northwest of Itbayat island, the southwest of Batan islands and the northwest of Babuyan islands are the generation source areas of the M2 internal tides.(3)The M2 internal tides generated in the strait propagate eastward and westward. The westward internal tide energy at the west of Batan islands travel slantingly downwards and returns to seasurface after the reflection on the Heng-Chun Ridge, which returns to bottom after the second reflection on the seasurface.This phenomenon shows destructive interference characteristic between different modes of internal tides.The westward energy divides into two branches,one branch generated in the northwest of Babuyan Islands directly turns into the sea basin, the other branch generated in the island slope areas of Itbayat island and Batan islands travels to the South China Sea shelf like a beam.When arriving in 118°E,a part of this energy turns into the sea basin, and the rest part travels northwest to coast area of China. Continental shelf and slopes have a important function of energy dissipation. The highest internal tide energy in the Luzon Strait is at the northwest of Itbayat island,which travels to the Pacific Ocean. But in the east of 122°E, the eastward internal tide energy travels to the Pacific Ocean like a beam.In order to make the simulation of M2 internal tide generated in the Luzon Strait more accurate,we also. extract first mode M2 internal tide signal from the altimeter data and calculated the internal energy flux.The results show that the results of model is reasonable.