Ejfect of Wind on the Mass Field and on the Density Current 555 



The method of Tsuchiva is simpler. The equations of motion of the geostrophic 

 current are 



where D is the geodynamic depth. All the quantities in these equations can now be 

 expanded into the Taylor series with respect to y and equation of terms of the same 

 power of V gives, putting /S = df jdy, 



(-)^^0;,.„^-(P)^.„. (1)=0; .^0. (XVn..) 



The distribution of D is easily found from oceanographic data. The east-west com- 

 ponent ?/o of the current velocity at the equator can therefore be obtained from the 

 second equation (XVII. 16) and the north-south component Iq is zero. At the same 

 time {8D/cx)o and (cD/8}^o must be zero. The oceanographic data show that these 

 conditions are fairly well satisfied in most cases. Values ot u and v near the equator 

 can be obtained by substitution of higher-order derivatives of u and v into expansions 

 of these quantities. In a later paper Tsuchiva has also dealt with the effects of the 

 inertia and frictional terms but these do not seem to alter the previous results. In the 

 immediate vicinity of the equator the east-west velocity component of the current 

 is determined by the curvature of the isobaric surface in the meridional vertical 

 section and not by the slope. The geostrophic approximation for the ocean currents 

 can be used much closer to the equator than has so far been done. The method used 

 by Tsuchiva is purely mathematical and not founded on any physical basis. 



