A Numerical Study on Gravity Wave Excited Through Nonresonant Interaction

Abstract

AbstractBy using a 2nd order operator‐splitting scheme and taking a fully nonlinear model, numerical simulation of gravity wave excited through nonresonant interaction in a compressible atmosphere is carried out. The results show that a downward propagating gravity wave packet is excited by two up‐going gravity wave packets owing to the nonresonant interaction. The energy of the excited wave is almost proportional to the energy of the primary wave, and increases slowly with initial energy of the secondary wave growing up, too. Wave energy tends to transfer mainly from the primary wave with highest frequency to other two waves, which isn't completely consistent with the resonant interaction. The characteristic time of the nonresonant interaction depends on the initial positions, wavelengths and frequencies of the primary and secondary wave, however, is independent of their initial amplitudes. The wave vector of the excited wave doesn't strictly satisfy the wave vector matching condition which is predicted by the weakly nonlinear interaction theory, and moreover, the wavelength and frequency of the excited wave are found to vary with time in the propagation. These indicate the weakly nonlinear interaction theory is limited to some extent for the nonresonant interaction.