### ASA 126th Meeting Denver 1993 October 4-8

## 2pUW7. Parabolic equation average propagation in the presence of rapid
range variation in a sediment layer.

**Roger M. Oba
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*Acoust. Simulation, Code 7181, Naval Res. Lab., Stennis Space Center, MS
39529-5004
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The routine for computing the average solution to the generalized
parabolic equation [R. M. Oba, J. Acoust. Soc. Am. 90, 2300(A) (1991)] in the
water works for propagation with sediments modeled by fluid layers. It can be
used in a ``marching algorithm'' from one range step to another, especially if
they are statistically independent. Because the algorithm relies upon analytic
forms of matrices for horizontal propagation of vertical modes, a natural limit
exists when (a) the sediment variation is rapid compared with wavelength and
depth, (b) the sediment variation is statistically independent in each range
step, and (c) the probability distribution over the velocity profile ensemble
in each range step is identical. Its application to the case where the
probability distribution can be parametrized by one variable is demonstrated.
This approach has advantages over averages of multiple runs of deterministic
models over realizations of sediment velocities. Features of the average
solution transmission loss and phase change, preserved by this algorithm, will
be discussed. [Work supported by ONR/NRL-SSC and ONR Young Navy Scientist
Program.]