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U.S. Navy researchers have improved a standard synthetic ocean modeling system with mixed layer depth (MLD) data. The patented technology is available via license agreement to companies that would make, use, or sell it commercially.
The properties of ocean waters, especially the transmission and reception of sound underwater, affect the planning and execution of numerous underwater applications, both military and civilian. Military underwater sonar depends on sound energy as the primary method of detecting and locating submarines and mines. Commercial shipping and fishing industries also utilize sonar making knowledge of underwater sound speed equally essential. Sound speed underwater is dependent on the water’s temperature, salinity, and pressure. As the temperature decreases, so does the speed of sound. As the water pressure increases with growing depth, so does the speed of sound.
The Navy’s Modular Ocean Data Assimilation System (MODAS) can be used to estimate the Sonic Layer Depth (SLD) of an area of interest using synthetic profiles of the ocean’s temperature and salinity. However, modeled estimates of the SLD based on such synthetic profiles lead to a shallow bias in the estimates of the sonic layer depth and a corresponding high bias in estimates of the minimum cutoff frequency (MCF) of acoustic signals propagated in the surface acoustic duct.
Navy researchers have improved upon this method by using mixed layer depth (MLD) values in addition to predicted values of temperature and salinity from MODAS. This new computer model compares the actual MLD for the area of interest, for example, as obtained from remote sensing, to an MLD predicted from a synthetic profile, and determines which is deeper. The method then derives a modified temperature and salinity profile by setting the temperature and salinity equal to the surface values at depths less than or equal to that MLD and using an algorithm to estimate temperature and salinity at depths below the MLD.
- More accurately reflects the actual temperature and salinity at the MLD and provides a more precise temperature and salinity gradient than conventional synthetic profiles
- More accurately estimates the sound speed gradient and the SLD as well as the associated transmission loss in the acoustic duct
- Businesses can commercialize the technology by licensing U.S. Patent 8,032,314 from the Navy
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