Influence of water column statistics and environmental parameters on time-domain simulations of SWARM 95 experimental data

Abstract

During the 1995 SWARM experiment acoustic data were collected at two different VLAs from an airgun source aboard the R/V Cape Hatteras. Intense nonlinear internal wave activity occurred during approximately 1 h of this data. The received signals contain significant variability, particularly of their intensity and time-frequency composition. Efforts to simulate the variability observed in the experimental data by using parabolic equation calculations and simplified analytic models have indicated the importance of bottom physical properties. Results from both methods show sensitivity to the structure of the bottom sound speed as well as the statistics of the internal waves that were present. Bottom properties are estimated from core data taken near the site and other previous studies in the area. To analyze the effects of the internal waves successfully, necessary modifications to these properties are described. Water column statistics are investigated using thermister data taken during the experiment. These statistical quantities will be compared with observed variability in the received signals. Analysis of these features provides relationships between internal wave variability and broadband interference patterns, intensity variations, and modal amplitude and arrival structure. [Work supported by ONR.]