Underwater sound channel in the northeastern East China Sea

Detection of Direction-Of-Arrival in Time Domain Using Compressive Time Delay Estimation with Single and Multiple Measurements

“…The time domain beamforming with CS was applied to the SAVEX15 experimental data, which were gathered in the northeastern East China Sea [ 23 , 24 ]. The experiment site is shallow with an almost-flat bottom and a depth of 100 m. Surprisingly, a sound channel whose minimum sound speed is located near the middle of the water column and which usually exists in deep water, was observed during the experiment.…”

“…Figure 1 shows the MF results according to the vertical line array (VLA) sensors and the DOAs in the time domain using the MF results. The simulation is conducted with the SAVEX15 environment [ 23 , 24 ], where an LFM signal from 0.5 to 2.0 kHz is transmitted from the source. The geoacoustic parameters, including density, sound speed, and attenuation of the sediment, are chosen in reference to the clay and silt, which cause high-reflection loss.…”

Observations Utilizing Korea Ocean Research Stations and their Applications for Process Studies

“…), air-sea interactions (measuring heat, CO 2 , CH 4 , etc. ), typhoons, the surface mixed layer and internal waves (e.g., Nam et al 2018), primary production and ocean acidification, and underwater noise and marine aerosols are ongoing (Choi and Noh 2006;Han et al 2015;Heo et al 2008;Kim and Choi 2006;Lee et al 2006;Moon et al 2016). Each station is equipped with more than 30 types of sensors (Table 1).…”

“…Moored thermistors (50 sensors), acoustic Doppler current profilers (ADCPs; 150 kHz), standard stationary CTDs (26 casts), and underwater CTDs (1,062 casts) were used to measure spatiotemporal variations in the flow and the physical water properties during the experiment. An underwater sound channel (USC) usually observed in deep water [e.g., a deep sound channel or sound fixing and ranging (SOFAR) channel] was discovered in this shallow water in the vicinity of the I-ORS during the experiment (Song et al 2018). The formation of this "thermal" USC is due to a temperature inversion; that is, the water temperature decreases with depth to approximately 40 m (minimum sound speed layer) and then begins to increase (Fig.…”

“…The main purposes of these KORS are for improving comprehensive oceanic and weather observations, providing core scientific information and data for regional and global environmental change studies, investigating typhoon dynamics (Choi et al 2013;Moon and Kwon 2012;Moon et al 2010), providing basic information for fisheries and sea fog prediction (Heo and Ha 2010;Heo et al 2014) as well as regional oceanographic studies (Nam et al 2018;Song et al 2018), functioning as a ground station for satellite oceanic remote sensing (Kang et al 2017), and investigating the movement and distribution of atmospheric constituents such as Asian dust and aerosols (Han et al 2015;Lee et al 2017).…”