Laboratory Measurements of Multi-Frequency and Broadband Acoustic Scattering from Turbulent and Double-Diffusive Microstructure. High-Frequency Broadband Acoustic Scattering from Non-Linear Internal Waves during SW06

Abstract

Abstract : The long-term goal of this research is to understand high-frequency broadband acoustic backscattering from small-scale physical processes, such as internal waves, turbulence, and microstructure, in shallow, stratified coastal waters. The primary objective of the proposed research was to measure high-frequency broadband acoustic backscattering in highly stratified, energetic environments and to determine the contribution to scattering from temperature and salinity microstructure. Testing the validity of existing scattering models and the initial development of new, and/or extension of existing, simple physics-based scattering models was a secondary objective of this work. To accomplish the stated objectives, high-frequency broadband (150-600 kHz) acoustic backscattering measurements were performed during the generation, propagation, and dissipation of non-linear internal waves in August 2006 as a part of the SW06/NLIWI experiment. Almost coincident microstructure measurements were collected by Jim Mourn with a profiling microstructure instrument, Chameleon. The contribution to scattering from biological organisms was quantified using a multiple-opening and closing net and environmental sensing system (MOCNESS), from which the zooplankton taxa, size, and depth (in coarse vertical bins) can be determined.