Internal waves in a summer pycnocline of the East China Sea

The bottom-mounted acoustic Doppler current profiler (ADCP) data obtained over a 70-h period in the East China Sea, about 80 miles to the southwest of the Jeju Island, are used to study internal waves in relation to tidal cycle. The spectral densities of the horizontal velocities followed E (h) aEuro parts per thousand f (-aEuro parts per thousand 1) between f (0) aEuro parts per thousand 0.8 cph and the buoyancy frequency, where f (0) is a transition point connecting the f (-aEuro parts per thousand 1) subrange and the steep falloff of energy from the semidiurnal spectral maximum at f (M2) toward higher frequencies. Manifestation of large-amplitude internal waves in the pycnocline has been mostly observed during a transition phase from high to low barotropic tide.