The vessel and procedures have been described in previous reports, particularly 

 those by Cromwell (1951 and 1954). The method of plotting station datai' and construction of 

 the vertical sections closely follows that of Montgomery (1954). 



Some Results of Hugh M. Smith Cruise 15 



Meteorological observations : Routine meteorological observations were recorded 

 during the cruise. Entries were made at each of the 10-mile interval bathythermograph lower- 

 ings and at each of the oceanographic stations. The U.S.N. Hydrographic Office Oceanographic 

 Log Sheet B (H. O. Pub. 606c) was used. These data are on file at Pacific Oceanic Fishery 

 Investigations, the Scripps Institution of Oceanography, and at the U. S. Navy Hydrographic Office. 



Because the zonal circulation and upwelling are primarily wind activated, the wind 

 data from each leg of the cruise are given in figure 2. The data from which the arrows were 

 drawn are listed in table 2. Unless there was a sudden change in speed or direction within in- 

 crements of one degree of latitude, the speed and direction were averaged for each 60 miles. 

 In figure 2, the direction, as given by the arrow, is to the nearest 10 ; the length is proportional 

 to the speed. The figure at the base of the arrow indicates the number of observations used in 

 obtaining, independently, the average speed and direction. 



Temperatures : Vertical temperature sections for the four station lines along 140°W. 

 longitude are shown on figures 3 through 6. These cross sections were constructed from bathy- 

 thermograph lowerings made at 10-mile intervals. The isotherms are at intervals of 2°F. The 

 depth of penetration is indicated by the small horizontal dash. The surface temperatures, as 

 measured in a sannple drawn with a bucket, are shown in the top pamel. Thermograph records, 

 giving a continuous trace of the surface temperature for the cruise, are available in POFI files. 



Referring further to figures 3 to 6, and reading from north to south (right to left), 

 we see evidence of the Equatorial Countercurrent (downward slope of the isotherms from the 

 northern limit of the section to approximately 4-1 /2°N. latitude); the South Equatorial Current 

 (4-1/2 N. to southern limit of the section) and the equatorial divergence and upwelling (doming 

 of the isotherms, centered at or near the Equator). The effect of this upwelling on the temper- 

 ature of surface waters is evidenced in the surface-temperature curve in the upper panel. No 

 well defined convergence, or front, as seen in some previous sections in this region (Cromwell 

 1953, 1954), was found. 



One striking feature of the temperature sections in this area is the well defined 

 thermocline in the region of the Countercurrent. The role which temperature plays with respect 

 to density in this region is evident when these sections are compared with those for sigma-t, 

 figures 8-11. 



Attention is directed to the temperature inversions beneath the Equator on figures 3, 

 4, and 6. As the isotherms are at 2°F. intervals auid the resulting isotherms are drawn for the 

 even temperatures, this inversion is not shown in figure 5. Had the 69° isotherm been shown 

 it would have been evident. 



_!_/ The data for the Hugh M. Smith oceanographic cruises have been punched onto IBM cards; 

 the calculations (sigma-t at interpolated depths and A£)) performed on the Card Progrann 

 Calculator jind the observed, interpolated, and calculated data, as appropriate, tabulated 

 directly onto the stencils. The procedures for the IBM calculations of these oceanographic 

 data were formulated by the Division of Oceanography, U.S.N. Hydrographic Office, 

 Washington 25, D. C. We wish to acknowledge with appreciation their assistance. 



