An acoustic scattering model for stratification interfaces.

Stable fluid bodies, such as the ocean and atmosphere, are composed of a series of increasingly dense layers, defined by density stratification interfaces in which the medium properties (e.g., temperature, salinity) change. The intensity of the stratification between the layers influences the internal mixing dynamics and entrainment, facilitating the transport of dissolved constituents within the fluid medium. Acoustic systems offer the means for high resolution observations of these interfaces, which allow for continuous data collection over broad spatial scales. Here, a one-dimensional acoustic scattering model is presented for predicting acoustic backscatter from stratification interfaces, which is widely applicable to the acoustic water column data collected with ship-mounted sonars. Model predictions based on hydrographic profiles suggest that in many oceanic cases, the density gradient perturbations can be disregarded, and sound speed perturbations alone drive the majority of the acoustic scattering. A frequency-dependent scattering intensity based on the sharpness of the stratification interface is predicted by the model, suggesting a path to remote estimations of the physical medium properties through broadband acoustic inversion.