706 Main Features of General Oceanic Circulation and their Physical Exploration 



Two of the waves have large periods and in these the flow is in geostrophic equili- 

 brium; they are the barotropic and baroclinic Rossby waves. The other four waves, 

 two of which are barotropic and the other two baroclinic, are inertial-gravitational 

 waves resulting from an imperfect balance between the pressure and the Coriolis force. 

 In general, the barotropic waves are pure gravitational waves with a velocity of propa- 

 gation \/{g{D-i^ + D^)} the baroclinic waves are pure inertial waves with a period of a 



WAVE NUMBER 5 CM"' 



WAVE LENGTH, KM 



Fig. 340. The velocity and frequency of all the various free waves, which may occur in a 

 two-layered ocean (according to Veronis and Stommel, 1956). 



half a pendulum day 2ttJ /; at the short branch in their connection on the right (see 

 Fig. 340) are ordinary internal waves at the boundary surface with periods of between 

 1 h and 1 day. 



This derivation of all possible wave types from a single equation is extremely interes- 

 ting and instructive. Two types of disturbances in time will be taken for a study of 

 wind-driven motions. In the first case they are forced waves generated by a moving 

 wave-wind system. This wind system as to the order of magnitude shall be comparable 

 with atmospheric disturbances as are shown in 5-day average charts. This corresponds 



