578 



Basic Principles of the General Oceanic Circulation 



gives a schematic representation of the water movements expected according to these 

 theoretical considerations. 



Between 30° N. and 30° S. the north-east and south-east trade winds give rise to the 

 broad North Equatorial and South Equatorial Current of the Northern and Southern 

 Hemisphere, respectively. The maximum intensity is reached in the regions where the 



Polar current 



Polar, front 



West winddrift 



Norttiern subtropicol 

 convergence 



North equatorial 

 current 



Soutti equatorial 

 current 



Souttiern subtropicol 

 convergence 



West winddrift 



Polor front 



Polar current 



Fig. 264. Schematic representation of the hydrosphere as a circular vortex. Current zones 

 and position of the main boundary surface and of the isobaric surfaces (with a strong 

 exaggeration of the vertical scale). {W, current towards west; E, current towards east). 



trade winds are most strongly developed ; their intensity decreases toward the regions 

 of high atmospheric pressure in the subtropics and also towards the equator. They are 

 deflected 45° cum sole from the wind direction and must be associated with a water 

 transport towards the poles. Water will therefore be piled up at their polar boun- 

 daries (in about 30° latitude) and therefore a pressure gradient will be generated in 

 the troposphere towards the equator. Sea level and the isobaric surfaces will be de- 

 pressed at the equator and will rise from here towards the poles. If there is no motion 



