Richard Lee Culver
Appl. Res. Lab., Penn State Univ., P.O. Box 30, State College, PA 16803
Planning Systems, Inc., McLean, VA 22102
Understanding and being able to predict high-frequency (10- to 100-kHz) acoustic scattering in the ocean for bistatic geometries (transmitter and receiver not collocated) has become increasingly important in recent years. For example, bistatic surface and bottom scattering must be understood in order to predict the angular dependence or spatial coherence of acoustic signals which have propagated through a shallow water channel. A high-frequency ocean surface scattering experiment conducted by Dahl and Jessup in 1992 using FLIP utilized an omnidirectional source and a line array receiver to measurement out-of-plane scattering at wind speeds up to 7 m/s. Estimates of low grazing angle bistatic scattering strength have been derived from these measurements, and are shown to compare favorably to theory developed by S. T. McDaniel. The McDaniel model utilizes composite-roughness theory to predict surface shape effects and includes attenuation and isotropic scatter by subsurface resonant bubbles. Bubble scattering is predicted to be the dominant mechanism at medium to high wind speeds and low grazing angles, and the FLIP experiment data offer evidence that this is the case.