| Résumé | Classical scattering theory predicts that the intensity of a saturated, scattered signal will have an exponential probability density function (pdf). However, the classical theory does not account for intermittency of the turbulence, which causes quantities such as the scattering cross section to vary in space and time. The classical theory can be modified to include intermittency by making the strength of the turbulence (i.e., the dissipation rate of turbulent kinetic energy) a local property of the scattering volume. The dissipation rate averaged over the scattering volume has a log-normal pdf. The intermittent theory is compared to measured pdf's obtained for scattering into an outdoor, ground-based, acoustic shadow zone. Deviations from the exponential pdf are observed readily in the data, and are predicted well by the intermittent theory. Intermittency is shown to dramatically increase the probability of measuring large values of the scattered intensity. |
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