A numerical experiment of excitation of the 5-day wave by a GCM

Though normal mode Rossby waves frequently appear in the troposphere and the stratosphere, excitation mechanisms of normal mode Rossby waves are not clear. In this study, excitation mechanisms of the 5-day wave, which is one of the normal mode Rossby waves, are investigated by a series of general circulation model (GCM) experiments. The results of the numerical simulation show that the amplitude of the 5-day wave simulated by the GCM with uniform lower boundaries is similar to that with the realistic topography. On the other hand, the amplitude of the 5-day wave without moist convection is much smaller than that with realistic topography. The amplitude of the 5-day wave grows when the rainfall amplitude in the 5-day range is large. These results indicate that heating due to moist convection is most important for excitation of the 5-day wave.