(M 1 ) y = - -j* , (M 1 ) x = (18) 



according to Ekman. 



The wind induced gradient current is a non-divergent current 

 only as a first approximation. As an effect of internal friction 

 there must be a slight deviation from the direction parallel to 

 the isobars. The average angle of deviation (from high to low 

 pressure) in the gradient layer may be denoted by a. Let u be 



o 



the zonal component of the geostrophic current in the case of no 

 internal friction, then 



pu 



g 



1 dp 



and 







U g = / pu g dz = - J f U dz 

 -D -D 



5? 



Suppose that the actual total horizontal mass transport, U, in 

 the gradient current is deflected slightly from the direction of 

 U by the angle a, as schematically indicated in figure 4. The 



O 



magnitude of a was estimated as l°-2° in higher latitudes and 

 5°-6° in lower latitudes (Neumann, 1952). 



Fig. ii. The difference vector U - U g represents approximately the aniso- 

 baric mass transport to balance the mass transport Mn in the layer 

 of frictional influence. 



25 



