The nonlinear effects on the characteristics of gravity wave packets: dispersion and polarization relations

By analyzing the results of the numerical simulations of nonlinear propagat ion of three Gaussian gravity-wave packets in isothermal atmosphere individ ually, the nonlinear effects on the characteristics of gravity waves are st udied quantitatively. The analyses show that during the nonlinear propagati on of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, th ough nonlinear effects exist, the time variations of the frequencies of gra vity wave packets are close to those derived from the dispersion relation a nd the amplitude and phase relations of wave-associated disturbance compone nts are consistent with the predictions of the polarization relation of gra vity waves. This indicates that the dispersion and polarization relations b ased on the linear gravity wave theory can be applied extensively in the no nlinear region.