SECT. 3] 



EQUATORIAL CURRENT SYSTEMS 



237 



"the fallacious generalization from a given longitude" is as dangerous in tropical 

 oceanography as it is in tropical meteorology. 



A . Wind Stress 



There is marked seasonal and longitudinal variation in the winds and the 

 wind stress. A region of light variable winds, separating strong easterly trades, 

 is to be found only in the Atlantic and in a 2000-mile band in the central Pacific. 

 This picture does not hold true for 70% of the equatorial oceans, namely, the 

 Indian Ocean and the Pacific Ocean east of 120°W and west of 155°W (Fig. 1). 



It is, therefore, to be expected that the great zonal currents are not constant 

 (Fig. 2). In both the Atlantic and Pacific Oceans, the South Equatorial Current 



30* 60 90° 120° 



I >l2.5m/sec CD 4.4-2.5 



! 12.5-9.4 CD 2.5-1.0 



I 9.4-6.7 CD <I.O 

 t 6.7-4.4 



150° 

 JULY 



Fig. 1. Direction and magnitude of the mean surface wind in January and July. (After 

 Mintz and Dean, 1952.) 





30' 60° 90° 120* 150* .I60» 150° 120* 90* 60° 30* 0° 



SUMMER 



Fig. 2. Current chart for the tropical ocean areas. "Winter" and "summer" refer to 

 northern winter and summer respectively. The chart is derived mainly from that of 

 Schott (1943). The only major changes are those of the equatorial undercurrents in 

 the Atlantic and Pacific (wiggly lines) and the Pacific South Equatorial Counter- 

 current. 



