Proceeding to the two southernmost stations (5 30'S. and 7 S. ) in figure 21, the 

 T-S curves are characterized by the salinity maximum above 200 meters. This maximum is 

 present at these latitudes on all longitudes we have sampled, i.e., 140°W. to the 180th meridian 

 (figure 25). That this high salinity with its origin from the subtropical convergence is continuous 

 to the west of the 180th meridian can be seen from figure 30(b) of Mao and Yoshida (1953). 



One particularly outstanding feature of figures 20 and 21, is the rather sudden tran- 

 sition in the T-S relationship between 1 N. latitude and the Equator. This suggests that the layer 

 of salinity maximum is eradicated very near the Equator by processes associated with the equa- 

 torial divergence and upwelling. 



Several similar stations within 1 north or south of the Equator and at various longi- 

 tudes are shown in figure 26. The nnethod of selecting the stations included in this figure was to 

 choose the station, along the particular meridiaji, with the lowest surface temperature. Thus, 

 their positions were near the center of the equatorial divergence. It is interesting to note that 

 two of the stations thus selected ( Hugh M. Smith cruise 15, station 11 and Hugh M. Smith cruise 

 16, station 18) show evidence of extension of the tongue of high salinity from the south; two are 

 intermediate (Hugh M. Snaith cruise 5, station 22 and Hugh M. Smith cruise 14, station 24) and 

 the fifth station, nunnber 34 for Hugh M. Smith cruise 5, suggests that processes associated with 

 the divergence have limited the northward extent of the high salinity tongue. 



Figure 27 serves as a summary of the T-S relationships discussed above. An aver- 

 age curve for the stations at 19 N. , 7 N. , the Equator, and 7 S. are shown. The T-S curves for 

 the Equatorial Pacific and the Western North Pacific Central waters, as taken from figure 209 B, 

 page 741 of The Oceans (Sverdrup, et al. 1942) have been included as broken lines. 



Discussion 



Thus far, this report has been concerned primarily with presenting the. data from 

 each of the legs of cruise 15 of the Hugh M. Smith and describing some of the more prominent 

 features revealed by these data. Figures 28 to 31 were prepared to describe some of the tem- 

 poral changes. For each field, temperature (figure 28), salinity (figure 29), sigma-t (figure 30) 

 and phosphate -phosphorus (figure 31), selected isopleths have been plotted for the first and 

 fourth legs of the cruise (stations 1-17 amd 45-60). 



In the upper panel of figure 28, we have plotted the surface temperatures as read 

 from the bucket thermometer at each bathythermograph lowering (solid line, stations 1-17; 

 broken line, stations 45-60). In the lower panel, the 60°, 70 , and 80 F. isotherms, for the 

 two sections, are plotted against depth as smoothed curves. These isotherms were originally 

 plotted in figures 3 and 6. At least four features are of interest: 



1. The slope of the isotherms associated with the Countercurrent is greater in the 

 fourth than in the first leg, suggesting an increased easterly flow of the Counter- 

 current. 



2. The 80 isotherm - surface intercepts for the fourth section have moved to the 

 north and south of those for the first section. This change is reflected in the 

 surface temperatures (upper pamel). 



3. The 70 isotherm, lying below the surface at the Equator, shows considerably 

 more "doming" in the fourth section. 



4. The trough in the 60 and 70 isotherms, centered under the Equator in the 

 first section, has shifted to the south in the fourth. 



