Gradient of the Cost Function Via the Adjoint Method for Underwater Acoustic Inversion

Abstract

The acoustic propagation problem in the ocean is modeled via the wide angle parabolic equation with a Neumann to Dirichlet map bottom boundary condition. An environment consisting of the water column, a sediment layer and the semi-infinite sub-bottom region is considered. The derivatives of a new cost function with respect to the unknown environmental parameters are calculated analytically via the adjoint operator and incorporated numerically in an inversion scheme. Full geoacoustic inversion for eight bottom parameters is performed successfully, using experimental field data from the Yellow Shark experiment, for the first time according to the authors’ knowledge. Adjoint inversion for the water SSP, using the EOFs, is also presented and validated with simulated data.