FISHERY BULLETIN: VOL. 72, NO. 4 

 60° 70'. 



Figure 7. — Geopotential anomaly, in joules per kilogram (dynamic decimeters), at the sea surface relative to 500 db in February- 

 April 1968. EASTROPAC cruises r/!owa.s Washington 75, David Starr Jordan 76, and Rockaway 77. The position of the intertropical 

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



DISCUSSION 



As was noted earlier, geopotential anomaly 

 computed from oceanographic data contains 

 short-period nongeostrophic fluctuations of the 

 mass field, but there is no way of removing them 

 from the data. Consequently, not all of the fea- 

 tures indicated by the present maps may be real. 

 Despite this problem, EASTROPAC data are 

 unique in their time and space coverage and in 

 the close spacing of stations on tightly coordi- 

 nated ship tracks and, thus, reveal some interest- 



ing features that have not been observed previ- 

 ously. 



A zonal discontinuity of the North Equatorial 

 Countercurrent in the months when the ITCZ lies 

 near its southernmost position is suggested by 

 the monthly average drift charts (U.S. Navy 

 Hydrographic Office, 1947; Wyrtki, 1965); how- 

 ever, the present maps (Figures 1, 2, and 7) are 

 the first to show it on the basis of quasi-synoptic 

 oceanographic data from the entire eastern inter- 

 tropical North Pacific. (It is highly unlikely that 

 the breakup of the Countercurrent as shown on 



1084 



