Journal of the Marine Biological Association of India

Volume 58 Issue 2

Improved sound speed estimation from XBT profiles: a new approach


P. A. Maheswaran and Dominic Ricky Fernandez

The accurate determination of sound speed in the ocean is an important requirement for naval operations related to acoustic communication and detection of under-water targets. Sound speed profile in the ocean is determined either by measuring directly the sound speed using velocity probes or it derived as a function of temperature, salinity and depth from Conductivity Temperature Depth (CTD) sensors. In some cases the meanmonthly profile of salinity is used to compute sound speed from eXpendable Bathy Thermograph (XBT) profile from onboard a ship. In the present work, an inter-comparison of measured sound velocity profile against that derived from XBT and CTD profiles are carried out. The inter-comparison showed that sound speed estimation using different techniques often coincide, however at salinity dominant locations it differs, i.e.  Sonic Layer Depth (SLD) showed a difference of more than 12 m. For XBT profiles, in place of mean monthly salinity profile, we demonstrate a new approach based on Stommel’s idea of co-variability between temperature and salinity to choose the best salinity corresponding to the available XBT profile. This approach significantly improves the sound speed estimation from XBT profiles even at locations of large salinity variability.



Sound velocity profile, sound speed estimation, XBT, Arabian Sea


Date : 30-12-2016