Analysis of internal tidal characteristics in the layer above 450 m from acoustic Doppler current profiler observations in the Luzon Strait

摘要: The characteristics of internal tides in the upper layer Luzon Strait are investigated on basis direct-observation current data recorded April 25 and September 26, 2008 by an acoustic Doppler profiler. Spectral analysis energy estimation show that diurnals semidiurnals carry most tides. Values depth-integrated total E for three frequency bands diurnal, semidiurnal, high frequencies 31, 6.9, 3.4 kJ·m, respectively. Near-inertial peaks only present baroclinic component. behavior typical tidal (i.e., O1, K1, M2, MK3, M4) near-inertial is basically consistent with linear wave theory, which predicts E+(ω)/E−(ω)=(ω−f)2/(ω+f)2 at depths above 66 m, while not all prominent components coincide well relation field other depths. Examinations depth structures temporal variations surface both mixed type, having diurnal inequality spring-neap fortnight periods. K1 O1 have comparable cross- along-shelf components, M2 S2 propagate toward shelf northern South China Sea as beams. amplitude phase vary time, but appear to dominated first mode, resemble second-mode structures. minor major axis ratios close expected values f/ω thermocline.