TSUCHIYA: SURFACE GEOSTROPHIC FLOW 



120" 110 



I SO- 

 SO" njTjT] 



20' 



90° 80' 



'l'|i|'|'M|'|i|'|iM|iMI'|M 



Geopotential Anomaly, J/kg 



db Over 500 db 

 August - September 1967 



70' 



I I I I I L] 30° 



10° 



10° 



20° 



■10 

 9 5 

 9 







''I I ' I I . I . I . I I I I I I I I I I I , I I I I I , I I I I I , I , I I I , I I I I I I I I I I I , I I I I I I I I I I I I I : I . I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I l1 



130° 120° 110° 100° 90° 80° 70° 



Figure 4. — Geopotential anomaly, in joules per kilogram (dynamic decimeters), at the sea surface relative to 500 db in August- 

 September 1967. EASTROPAC cruises Thomas Washington 45, Undaunted 46, and Rockaway 47. The position of the intertropical 

 convergence zone at the eastern and western ends of the map is indicated by triangles. 



The position at the easternmost and westernmost 

 meridional sections is indicated by triangles on 

 each map in Figures 1-7.) 



In February-March 1967 (Figure 1) the North 

 Equatorial Countercurrent is present between 

 lat. 5° and 8°N2 at long. 126° and 119°W, but it is 

 practically missing at long. 112°W and only 

 weakly developed at long. 105°W. At long. 98°W 



^Near the northern edge of the North Equatorial Countercur- 

 rent, flow is usually weak, and the current boundary is not 

 always well defined by the distribution of geopotential anomaly. 

 The northern boundary cited here is that of the band of strong 

 current. Weak eastward flow may extend farther north. 



the Countercurrent is entirely absent. From long. 

 95° to 85°W a strong eastward current, which can 

 be identified as the North Equatorial Counter- 

 current, is found along lat. 5°-6°N between the 

 cyclonic and anticyclonic eddies mentioned ear- 

 lier. In April-May (Figure 2) no countercurrent is 

 found at long. 119°, 112°, and 105°W, but a strong 

 countercurrent is indicated between lat. 4° and 

 7°N at long. 98°W. In April-May the ITCZ starts 

 returning to the north and is located north of lat. 

 6°N. 



The development of the North Equatorial 

 Countercurrent in February- April 1968 (Figure 



1081 



