Abstract
The Rossby and gravity waves are discussed on a rotating sphere. The YanaiMaruyama waves observed in the Tropical Pacific are considered as the so-called tidal motion of the second kind k=4 and n=4 or n=6, where k is the wave number in the longitudinal direction and n is the order of the latitudinal eigenfunction. In case where k=4 and n=4, the equivalent depth h is estimated as h∼O (10 m) if we assume that the period of disturbances is about 5 days and the disturbances are confined to the neighbourhood of the equator. On the other hand we have h∼O (1 km) in case where k=4 and n=6 and the disturbance becomes a global one. The results of numerical computation in case where k=4 and n= 6 are shown.
As the mutual interaction of disturbances between middle latitudes and tropics, the simple consideration whether the disturbances are external or internal on the horizontal plane is put in the discussion when the zonal current has a horizontal shear.
