The applied tomography experiment of 1990

The feasibility of an operational tomography capability has been demonstrated. Daily inversions of acoustic travel time data produced sound speed profiles that were successfully integrated into the standard Navy operational product for the NW Atlantic. Improved estimates of the sound speed (and thus temperature) reduced the error variance approximately 20 percent along the source-receiver vector. The resultant temperature fields, produced on a daily basis, have been reformulated as synthetic bathythermographs for input to the Optimal Thermal Interpolation System at the Fleet Numerical Oceanography Center. Sound speed fields based on tomographic results change predicted convergence zone ranges by about 10 km, corresponding changes in local acoustic intensity of 10 with dB or greater. In addition, acoustic transmissions from Bermuda through the Gulf Stream were used to estimate the position of the Gulf Stream in real time. The precision (using air-dropped expendable bathythermograph (AXBT) data as ground truth) is better than 10 km under certain circumstances. This information can be used by the Operational Oceanography Center to improve estimates of Gulf Stream frontal location, which are presently based on IR satellite images. The transmissions from Bermuda northward are continuing. The deployment of six acoustic sources south of Bermuda in 1991 will improve the horizontal resolution.