In this paper, the author attempts to make clear the physical meanings of the internal and gravitational waves by using the dimensionless equations of motion. The small scale disturbances in the typhoon or near the frontal surface are also dicussed in connection with the Rossby number. Since the effect of horizontal divergence or convergence is large compared with the vorticity in such cases, the internal gravitational wave whose character changes when the condensation occurs predominates. As a numerical example, we discuss how the initial small scale disturbances develop with increasing time in the case where the divergence of horizontal velocity is considerably larger than the vorticity.