132 



WIND CURRENTS AND WIND WAVES 



the south by a trough Une that probably represented a line of divergence. 

 This inshore current to the north may not have been an effect of the 

 wind only, however, but may have represented a countercurrent that 

 developed when variable winds blew (p. 204). 



In June, northwesterly winds had prevailed for several months, 

 carrying the light surface water out to a distance of about 150 km from 

 the coast, where the swift current followed the boundary between the 

 light offshore water and the denser upwelled water. Within both types 

 of water several eddies appeared. 



Similar considerations apply to conditions in the open ocean. Take 

 the case of a stationary anticyclone in the Northern Hemisphere. Over 



Fig. 34. A. Geopotential topography of the sea surface off southern California 

 relative to the 500-decibar surface in February, 1938, after a period with westerly or 

 southwesterly variable winds. B. Topography and corresponding currents in June 

 after a period with prevailing northwesterly winds. 



the ocean the direction of the wind deviates but little from the direction 

 of the isobars, so that the total transport of the wind will be nearly 

 toward the center of the anticyclone. Light surface water will therefore 

 accumulate near the center of the anticyclone and a distribution of mass 

 will be created which will give rise to a current in the direction of the 

 wind. Similarly, the surface water will be transported away from the 

 center of a cyclone, at which heavier water from subsurface depths must 

 rise. Again a field of mass is created, and associated with it will be a 

 current running in the direction of the wind. 



Mention has so far been made only of the direction of the wind, but 

 the total transport depends also upon the square of the wind velocity and 

 upon the latitude. In order to find the actual convergences due to 

 wind, it is therefore necessary to take into account both the velocity and 

 the latitude. An attempt in this direction has been made by Mont- 

 gomery, who finds that in the North Atlantic Ocean the region of maxi- 

 mum convergence lies to the south of the anticyclone. 



