3. Results 



3.1 Horizontal Velocities 



Dynamic heights were calculated and adjusted to give transports equal to those de- 

 termined from the curl of the wind stress (see appendix II for a numerical example). These 

 adjusted heights are shown as lines of equal geopotential through the area of the investi- 

 gation (figs. 23 through 54). The selected contour interval is 0.01 dynamic meter, a value 

 which is uncertain in the upper levels where the paucity of stations must result in excessive 

 smoothing of the dynamic topography. But this interval is used throughout to facilitate 

 comparison of all levels. 



3.1.1 Velocities in 1961. — In figures 23 through 28, the wind-driven geostrophic trans- 

 port for September 1961 was used to obtain reference values for dynamic height calcula- 

 tions based on oceanographic observations made during that month. Geopotential 

 anomalies at the 250, 500, 1,000, 2,000, 4,000, and 5,000 meter levels are presented. The 

 geostrophic transport for these figures was determined from the difference between wind- 

 driven total transport and Ekman transport. Figure 29 shows the geopotential anomalies 

 at 5,000 meters calculated from the September 1961 oceanographic data and the wind- 

 driven geostrophic transport which was computed from the tabulated geostrophic transport 

 function. Figures 30 through 32 show the results of a comparison of the flow computed 

 from the geostrophic transport function in August 1961. 



The flow pattern was generally zonal, especially in the upper layers. North of about 

 40° N, the direction of flow was easterly at 250, 500, and 1,000 meters, but reversed to 

 westerly at 2,000, 4,000, and 5,000 meters. South of 30° N. a significant southerly flow 

 occurred at 250 and 500 meters. At 2,000 meters, and below, the flow conformed to the 

 trend of the bottom contours along the Hawaiian Island Rise. The deep velocities were 

 westerly north of the rise and easterly south of it. Figures 28 and 29 can be used to com- 

 pare the consequences of using the wind-driven flow with and without consideration of 

 Ekman divergence to obtain reference values for dynamic heights. No significant differ- 

 ences are noted. An analysis of the oceanographic observations used in these determina- 

 tions (or of other observations in the same area) shows the water structure leading to 

 baroclinic transport to vary only slightly. A comparison between September 1961 oceano- 

 graphic data adjusted for transports from the wind stresses of September (figs. 26, 27, and 

 28) and then of August (figs. 30, 31, and 32) gives an indication of the variations in the 

 barotropic velocity. 



The flow at 4,000 and at 5,000 meters tended to conform to the isobaths. This ten- 

 dency was evident both at the Hawaiian Island Rise and near the Aleutian Trench. 



3.1.2 Velocities in 1962. — The oceanographic observations in 1962 comprise a single 

 section along the 160°W meridian. By adjusting the values of the dynamic heights to 

 yield transports equal to the geostrophic transports arising from different wind stress dis- 

 tributions, an evaluation is made of the effects of (a) estimating wind stress from a monthly ■ 

 mean of atmospheric pressure distributions contrasted to estimating it from twice-daily 

 reports of pressure distribution and taking a monthly mean of these values, and (b) using 

 different drag coefficients in combination with the two alternate methods of finding the 

 mean monthly stress values. Figures 33 through 38 show the geopotential topography 

 adjusted to geostrophic transport arising from wind stresses based on a drag coefficient 

 of 0.0026 and the mean pressure distribution for September 1961. Figure 39 is based on 

 the same drag coefficient but the average of two daily reports of atmospheric pressure 



10 



