HUGH M. SMITH CRUISE 10 



Cruise 10 of the Hufih U. Smith, July 19-31, 1951, was the first of a 

 series of five cruises to investigate the general hydrographic conditions in the 

 offshore waters of the Hawaiian Islands. Thirty-three stations were occupied at 

 the positions shown in figure 11. Casts to 1,200 m. were made at all stations 

 except 15, lb, 20, and 21, where casts were made to approximately 50 m. above the 

 bottom. Stations 19 and 33 vvere occupied at approximately the same position. The 

 data from the two were averaged in constructing the station plots, since both 

 fitted into the time sequence when compared to adjacent stations. Stations 8A and 

 8 were also occupied at approximately the same position, but in this case the time 

 Interval between 8 and all the surrounding stations was less than for 8A so only 8 

 was used. 



The solid lines on the station plot (fig. 11) indicate the lines along 

 which profiles of dynamic height, temperature, sigma-t, salinity, and dissolved 

 oxygen have been drawn. 



The order and method of presenting the data are the same as for cruise 1. 



General Wind Pattern 



The weather maps for the cruise period show the well-developed Eastern 

 North Pacific High which is typical of summer conditions. However, comparison of 

 the computed winds (table 4) with the average winds (table IJ shows that the forces 

 were normal for July but that an abnormally large percentage of observed winds were 

 from the east. The computed velocities vary from 9 to 20 knots, with 16 of the 23 

 values being within the 11-16 Jtnot range of the Beaufort 4 average for the month. 

 Out of 23 observations, lb or 70 percent show east winds, although the normal for 

 the month is only 30 percent. V»hen the wind directions were transformed into cur- 

 rent direction by the 45° cum sole rule, they were 5° to 50° to the right of the 

 295°T mean for July (table 2). 



Dynamic Topography and Geostrophic Currents 



The dynamic height cross sections are shown in figure 12 and the dynamic 

 topography of the upper 3OO decibars (m. ) in figure 13. Because of uncertainty as 

 to the effect of land masses on the topography, no attempt was made to construct 

 the topography Inshore of stations, except in areas where there were strong indica- 

 tions that the flow should follow a definite pattern because of the physical con- 

 figuration of the land masses and the circulation in the surrounding area. For 

 example, the contours were drawn in the area south of Hawaii because the topography 

 to the east and south indicates a strong flow parallel to the south coast of that 

 island due to the divergent effect of the island barrier. In this and similar 

 cases the contours are dotted. 



The topography shows that the circulation on the northeast or windward 

 side and on the southwest or leeward side of the island chain is completely dif- 

 ferent. On the windward side of the islands the circulation was quite confused 

 (figs. 12 and I3). The flow was westerly all along the section from station 27 

 to station 30, with the highest velocities occurring between stations 27 and 28. 

 The flow between stations 30 and 32 was easterly, but it turned again to the west 

 north of station 32. In the area north of Oahu the flow was deflected northwest- 

 ward along the islands. 



On the leeward side two large cyclonic eddies dominated the circulation 

 pattern (figs. 12 and 13), one centered at station 23 and the other at station 10. 

 The one west of Hawaii, centered at station 23, was much farther north than during 

 cruise 1. The slopes of the surfaces in the eddy centered at station 10 were so 

 great that it seems reasonable to assume that it was a case where external effects 

 such as tides or internal waves were in phase witi; the effect of the horizontal 

 motion. 



11 



