Abstract (Invited)

Infrasound Generation at Sea Surface Wave Blockage

K.A.Naugolnykh (N.N. Andreyev Acoustics Institute, Moscow, Russia)

e-mail: Konstantin.naugolnykh@noaa.gov

Two counter-traveling gravity-capillary waves of the same frequency, forming a standing wave on the surface, give rise to a sound wave traveling away from the sea surface [M. S. Longuet-Higgins, 1950; L. M. Brekhovskikh, 1966]. In general, nonlinear interaction of surface gravity-capillary waves propagating in opposite directions may result in radiation of a sound wave that propagates from the surface of the ocean. [V. V. Goncharov, K. A. Naugolnykh, and S. A. Rybak, 1977]. The frequency and the wave number of the radiated wave are determined by the synchronism conditions. The surface waves propagating in the opposite directions can be generated by the action of the wind on the remaining swell of a cyclone. Also progressive gravity-capillary waves superimposed on the flow produced by the finite-amplitude dominant wave can be blocked at the points where the group velocities balance the convection by the larger-scale flow generating the reflected wave. Both effects lead to the low frequency sound generation both in the atmosphere and ocean.

Section : 6