depth but was much smaller in area. The 



Eastern North Pacific High was centered 500 

 to 600 miles northwest of, and was equal in 

 area and intensity to, the normal cells for 

 July and August. Inspection of the daily wea- 

 ther maps showed that this was the result of a 

 series of unusually intense (up to 1,047 mb. ) 

 slow-moving highs which began to appear dur- 

 ing the last week of February and continued 

 to occur during the first three weeks of March. 

 As a result of this unusual pressure distribu- 

 tion, the northern limit of the northeast trades 

 was at about the same position as the normal 

 southern limit of the westerlies. The northerly 

 migration of the trade wind belt is also shown 

 by the winds observed during the cruise (fig. 

 5). The winds were almost entirely easterly 

 after station 54, which was occupied on Febru- 

 ary 23. The only exceptions were shifts of 

 short duration which occurred when fronts 

 passed over the vessel. As during February, 

 all of the fronts were generated by the lows 

 which formed in the Hawaiian Islands area 

 (fig. 6). 



CURRENTS 



Geopotential Anomalies (Dynamic Heights) 

 and Geostrophic Currents 



Since the discussion of the various 

 fields of an ocean area is more understandable 

 when the general character of the flow pattern 

 has been established, the geopotential anoma- 

 lies and the dynamic topography and geostrophic 

 currents will be discussed first. The geopo- 

 tential anomalies in dynamic meters of the 

 standard isobaric levels relative to the 1, 000- 

 decibar surface for each north-south transect 

 are shown in figures 7-16, and the dynamic 

 topography of the 0-, 100-, 200-, 400-, and 

 600-decibar (m. ) surfaces are shown in figures 

 17-21. 



Before discussing the circulation 

 pattern depicted by these plots, a review of 

 the assumptions made and procedures used 

 in their construction is in order. In addition 

 to the assumption that the 1, 000-decibar sur- 

 face is the level of no motion, it is assumed 

 that the cross-sections and contours represent 

 a synoptic picture, although the time interval 

 between the first and last station was 2 months. 

 The curves were drawn to fit the observed data, 



and in a few cases, such as the trough in the 



o , o 



upper 100 meters between 25 and 26 N. lati- 

 tude on 165 W. longitude, features have been 

 drawn in from differences in density indicated 

 by the bathythermograph temperatures. This 

 procedure gives a more confused current 



pattern than the usual smoothed curves, but it 

 is probably much closer to the actual conditions. 

 At stations 31 and 89 and at stations 55 and 85, 

 which were less than 60 miles apart but were 

 occupied 17 to 20 days apart, the heights and 

 positions were averaged. 



The dynamic topography of the sea 

 surface, figure 17, shows that the general flow, 

 except for the area just north of the Hawaiian 

 Islands, is in an east-southeasterly direction. 

 A number of both cyclonic and anticyclonic eddies 

 are superimposed on this flow, the greatest num- 

 ber and most intense eddies occurring in the 



northeastern part of the area. The concentration 



r o 



is well to the east of 155 W. longitude, where 



the spacing of the transects was reduced from 5 

 degrees to 2 degrees of longitude, so they cannot 

 be merely attributed to the increase in the station 

 concentration. Neither can they be attributed to 

 local winds or internal waves since the largest 

 and most intense eddies, e.g., the large anti- 

 cyclonic eddy centered at station 66, were not 

 associated with storm passages and extended over 

 two or more stations or transects. In the area 

 just north of the Hawaiian Islands a narrow ridge 



of greater than 1.9 dynamic meters occurs. It 



o 

 extends as far east as 155 W. longitude and cor- 

 responds very closely to the February-March 

 position of the center of the Subtropical Converg- 

 ence.!' indicated on the German Hydrographic 

 Office (prepared by Schott) (Deutsche Seewarte 

 1942) current charts. 



The principal changes in the dynamic 

 topography with depth (figs. 17-21) are the grad- 

 ual northward shift of the ridge which delineates 

 the transition from eastward to westward flow 

 and the broadening of the ridge with depth. In the 

 western part of the area the center of the ridge 



shifts from just north of the Hawaiian Islands at 



o 

 the surface to approximately 30 N. on the 600- 

 decibar surface. To the east it is apparently 

 south of the area at the surface and shifts rapidly 

 to the north below the 100-decibar surface so that 

 it lies within the area as far east as 147 W. on 

 the 400-decibar surface. A further shift to the 

 north is indicated on the 600-decibar surface, but 

 the two large anticyclonic eddies break the ridge 

 into two parts which correspond to the "Y" shape 

 of the Subtropical Convergence shown in the 

 German Hydrographic Office current chart 

 (Deutsche Seewarte 1942) and to the lobations 

 which occur in the dynamic topography of the 

 Carnegie data (Sverdrup et al. 1945, fig. 246). 



— "Subtropical Convergence" refers to the 

 zone of convergence between the easterly flowing 

 water to the north and the westerly flowing water 

 to the south. 



