Profiling measurement of internal tides in Bali Strait by reciprocal sound transmission

Abstract

A reciprocal sound transmission experiment was carried out during June 10–13, 2015 along a cross-strait line in the Bali Strait with strong tidal currents to measure the vertical section structures of the range-averaged current and temperature at a 3 min interval. The five-layer structures of the range-averaged current and temperature in the vertical section were reconstructed by regularized inversion of the travel time data for two rays. The hourly-mean current showed the generation of nonlinear internal tides with amplitudes of 1.0–1.5 ms^-1 and periods of 6 h superimposed on semi-diurnal internal tides with amplitudes decreasing from the upper to lower layer. The hourly-mean temperature was characterized by variations with amplitudes of 1.0–1.5°C and periods of 6 and 8 h. The current variations showed an out-of-phase relation between the upper and lower layers while the temperature data varied in-phase for all five layers. The two–day-mean current and temperature showed a stratified structure, varying from -0.6 to -0.1 ms^-1 and from 23.8 to 28.0°C, respectively. The five-layer current and temperature were significantly above the inversion errors.