Shadow zone mapping using parabolic equation method in the Bali Strait Waters

Abstract

Shadow Zone is an area where sound waves cannot penetrate a water column due to deflection. This study aims to map the shadow zone based on oceanographic parameters in the Bali Strait. The data used are temperature, salinity, and depth for 31 days in the East Season (July) in the Bali Strait at two stations from the results of numerical modeling downloaded from the website https://marine.copernicus.eu/. Shadow zone simulation uses the parabolic equation method with certain parameter limits. The vertical temperature profile shows that the deeper the water is, the lower the temperature, whereas salinity is the opposite. The sound velocity is affected by the parameters of temperature and salinity. At the location of the 25 m transducers, the undetected medium beam is narrower than the location of the 110 m transducers so that the shadow zone with a 110 m transducer position has a broader area. The Shadow zone area in the northern Bali Strait is effectively detected using a frequency of 100 Hz. In comparison, in the southern part of the Bali Strait, it is effectively seen at a frequency of 38 Hz, with the respective transducer positions used at a depth of 25 and 110 m.