since in a stratified ocean a "zero layer" (layer of no motion) 

 for the wind driven circulation must develop, which may be con- 

 sidered as the lower boundary of the circulation, where the velo- 

 city of the wind d riven currents vanishes. Therefore, the "zero 

 layer" can also be replaced by a rigid but frictionless boundary, 

 and the necessary resistance in order to balance the driving 

 forces is brought about only by the virtual internal friction. 



The wind driven circulation in an ocean with a variable 

 depth, D, of the currents is analyzed, and it is found that the 

 relative change of the depth D with latitude equals the relative 

 change of the Coriolis parameter in the large scale planetary 

 circulation. This suggests that the ocean reacts to the planetary 

 vorticity effect in such a way that it rather tends to adjust its 

 level of no motion for the wind driven circulation than to dis- 

 place the whole gyre with relatively high current velocities to 

 the west. Since the depth of the layer of no motion for the wind 

 driven circulation is also strongly related to the vertical den- 

 sity stratification, the mechanism of mutual adjustments between 

 the current systems and the mass distribution, as it is finally 

 observed in the oceans, appears rather complicated. 



For a quantitative study of the wind driven ocean circulation 

 knowledge of the wind stress at the sea surface, and of the virtual 

 internal friction is necessary. Both of these important forces 

 have been discussed in detail in this report. With regard to the 

 internal friction a simple expression corresponding to Guldberg- 

 Mohn's expression was used, and coefficients of virtual internal 

 friction were determined. It seems that a more general treatment 



iii 



