ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aUW6. The effect of gradients on high-frequency bottom scattering.

John E. Moe

Darrell R. Jackson

Appl. Phys. Lab., Univ. of Washington, 1013 NE 40th St., Seattle, WA 98195

The first-order perturbation expression for the bistatic scattering cross section of a rough surface [Moe and Jackson, J. Acoust. Soc. Am. (to be published)] is used to study the effect of gradients on high-frequency bistatic bottom scattering. Strong gradients on scales of several centimeters are often observed in shallow-water environments. It is shown that upward refraction or reflection by strong gradients can lead to significant enhancement of high-frequency scattering. This enhancement occurs over a wide range of bistatic angles, but is strongest when the incident and scattered grazing angles are equal. These effects can be explained in terms of the reflection coefficient of the corresponding mean (flat) surface. [Work supported by ONR.]