A MODAL INVERSION SCHEME FOR OCEAN ACOUSTIC TOMOGRAPHY

An inversion scheme based on normal-mode representation of the acoustic field is applied in ocean acoustic tomography for a range-dependent reconstruction of the sound speed variations at a vertical slice. The scheme is based on the assumption that modal phase can be measured by suitable mode filtering at some range from the sound source. Two cases have been considered. The first of them makes no use of oceanographic information on the variability to be recovered, while the second one makes use of empirical orthogonal functions (EOFs) that describe sound speed variations in the ocean. The data used in the applications presented in this paper are synthetic ones. It is shown that both modal inversion schemes can be used for the recovery of range-dependent sound speed variations of compact support in the ocean, provided that a range dependent background environment is used to describe an initial guess of the variations. The scheme is more powerful when EOFs are used.