Abstract: General waveactivity density is used to diagnose the rainfall event of the landing of typhoon Morakot. The results show that the anomaly of the wave-activity density corresponds with the observed 6-h accumulated surface rainfall. High resolution simulation data is used to analyze the wave characteristics of the landing of typhoon Morakot, the low wavenumber structures that dominated the distribution of the asymmetric convection, and the amplitude of the two-wavenumber waves that occurred during landfall. The strong convergence and divergence of the asymmetric wind shows characteristics of gravity inertial waves. The mesoscale waves that induced mixing happened between the eye wall and the eye.