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

Though normal mode Rossby waves frequently appear in the troposphere and th e stratosphere, excitation mechanisms of normal mode Rossby waves are not c lear. 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 ci rculation 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 muc h smaller than that with realistic topography. The amplitude of the 5-day w ave grows when the rainfall amplitude in the 5-day range is large. These re sults indicate that heating due to moist convection is most important for e xcitation of the 5-day wave.