Ocean Acoustic Tomography Experiment using Explosive Charges for Measurements of Mesoscale Oceanic Variability in the East Sea
Jungyul Na
Department of Earth and Marine Sciences, Hanyang University, Ansan, Kyunggi-do, 425-79L Korea
najy0252@email.hanyang.ac.kr
1. Introductron
Ocean acoustic tomography (OAT) based on the arrival time perturbations was proposed by Munk and Wunsch (1979) as a tool for monitoring large-scale structure of the ocean interior. In general, OAT experiments require fixed source-receiver system in order to obtain absolute magnitude of sound velocity fluctuations. Recently, the technologies of real-time tomographic survey were suggested in variety of ways and diversity of applications (Lynch et al., 1992). We apply a new method of the real-time tomography using explosive changes as sources and a fixed vertical line array (VLA) and sonobuoy as a receiver, called “SUS-OAT” .
The sonobuoy which is deployed close to the explosive source can provide a source can provide a source spectrum from which a shock wave and bubble pulse information are available. This rapidly deployable SUS-OAT system can be used to locate any sub-surface temperature anomaly such as “Warm eddy” in the East Sea when the sea surface temperature field is so diffusive that no airborne sensor can detect any anomaly. The exact explosion time and detonation depth are calculated by empirical formula (Arons 1948; Blaik and Christian, 1965; Chapman, 1985), so that we can observe the exact arrival times of ray path. Since the time interval between the shock wave and the first bubble pulse,termed the first bubble period, is a sensitive function of charge weight and depth (Cole, 1948), the depth of explosion is computed inversely by exact measurement of the first bubble period.
In this paper, we report the results of the SUS-OAT experiment to observe the mesoscale variability of the oceanic structure that was carried out in the Ulleung Basin of the East Sea/Japan Sea.
