extrapolated backwards to day 1. Consequently, ex- 

 pected values for day 1 through day 60 have no validity. 

 Interpolated values could have been obtained if the har- 

 monic analyses were carried out from July 1967 to July 

 1968. A 90-day gap, however, permits meaningful sum- 

 mation only to R = 2 in Equation (3) which, as is evident 

 from Figures 5, 6, and 7, would resolve only a small por- 

 tion of the variance. 



After the winter of 1968, the longest gap in the data 

 series of about 20 days occurred in 1969, limiting signifi- 

 cant interpolation for this gap to n = 9 in the summa- 

 tion of Equation (4). In general, all coefficients to n = 12 

 that are tabulated in Appendix I can be used to evaluate 

 the harmonic function for time spans, including those in 

 1966 and 1967, where data gaps are 15 days or less. 



Results of the Harmonic Analyses 



Within the limitations discussed in the previous sec- 

 tion the harmonic coefficients tabulated in Appendix I 

 can be used in Equation (3) to obtain smoothed values of 

 the temperature, salinity, and depth at any of the desig- 

 nated levels from the sea surface to ct, 27.4. This calcula- 

 tion was performed and the results were tabulated in Ap- 

 pendix II for the first of each month of each of the years 

 1966 through 1971. The values for the 1966 and 1967 

 periods were computed by summing the harmonic series 

 to the 3d harmonic, while the values for the succeeding 

 years were computed to the 12th harmonic. In addition, 

 the values for the 366th day for each analysis period are 

 included to allow the month-to-month changes in prop- 

 erties to be computed for the entire year. Because har- 

 monic analyses were performed for individual years, the 

 expected values on the 366th day of one year may not 

 match up with the corresponding values on the first day 

 of the following year. 



In order to facilitate the computation of dynamic 

 heights at the surface and acceleration potentials at ct, 

 levels relative to 1,000 dB, interpolated temperatures, 

 salinities, and a, values at 1,000 m are included in the 

 tabulations of Appendix II. 



OCEANOGRAPHIC CONDITIONS AT 

 OWS-V 



The Oceanographic Setting 



In addition to heat exchange and wind induced flow 

 processes, variability in surface properties and vertical 

 structure is affected by shifts of the ocean system 

 relative to the geographically fixed location, variations 

 in the intensity of currents, and eddies. A description of 

 the oceanographic setting of OWS-V, therefore, will aid 

 qualitative interpretations of the low frequency oceano- 

 graphic variations in the time series presented in this 

 report. 



OWS-V is located in waters downstream of the 

 Kuroshio, called the Kuroshio Extension (Sverdrup et 

 al. 1942). Summaries of the oceanographic conditions of 

 this region have been given by Masuzawa (1972) and 



Kawai (1972). These articles supplement the earlier 

 work of Fleming (1955), Muromtsev (1958), Uda (1963), 

 Barkley (1968), and others. 



The surface distributions of temperature and salinity 

 of the North Pacific Ocean have been presented in 

 numerous atlases and other publications such as that 

 produced by the Japan Hydrographic Association 

 (1975). These show that isopleths of temperature and 

 salinity are generally zonal in the vicinity of OWS-V. 

 Meridional temperature gradients range from about 

 0.4°C per degree of latitude in summer to 0.9°C per de- 

 gree of latitude in winter. Salinities at OWS-V tend to 

 be highest in late winter and early spring when the 

 meridional gradient is about 0.04%. per degree of 

 latitude. Lowest salinities occur from July to October 

 when the meridional gradient is about 0.09%. per degree 

 of latitude. 



Charts of the dynamic topography of the North 

 Pacific Ocean prepared by Reid (1961) and Wyrtki 

 (1975) show that OWS-V is located in the eastward ex- 

 tension of the Kuroshio. These charts, however, are 

 based on smoothed, long-term averages and do not ex- 

 hibit the nature of the flow near OWS-V that mate- 

 rially affects the variability of oceanographic properties 

 at the station. The dynamic topography presented by 

 Kawai (1972), based on observations during the summer 

 and fall of 1957, is reproduced in Figure 10. The tightly 

 packed isopleths of dynamic height show the meander- 

 ing nature of the Kuroshio Extension between lat. 32° 

 and 38°N. Eddies abound both to the south and to the 

 north of this current. 



The existence of eddylike features associated with the 

 Kuroshio current system has been well documented in 

 the literature. The confluence area of the Kuroshio and 

 Oyashio has been called the "Transition Area" by Uda 

 (1938) or the "Perturbed Area" by Kawai (1972). 

 Barkley (1968) drew attention to the eddy structure of 

 this area, and Bernstein and White (1977) have shown 

 that the baroclinic mesoscale eddy energy in this ju-ea is 

 an order of magnitude higher than that east of long. 

 170°W. 



In the illustration (Fig. 10), OWS-V is located within 

 the meandering current. It is conceivable that at various 

 times the current could pass either to the north or to the 

 south of the station, but OWS-V would remain in an 

 area of eddy-induced variability. This variability makes 

 analysis of the vertical temperature and salinity dis- 

 tribution difficult if these properties are presented as a 

 function of depth. However, if these properties are 

 presented as a function of density (isentropic format) 

 current and eddy-induced variability is reflected only in 

 the depth distribution of isopycnals. 



Meridional and zonal sections of the salinity and 

 depth as a function of o; are useful in describing the 

 baroclinic setting. A meridional section of hydrographic 

 stations was occupied in April 1971 at long. 168°E 

 (Roden 1972). Although this section lies to the east of 

 OWS-V, it reflects the characteristic meridional distri- 

 butions to be found at the longitude of the station. The 

 dominant feature in the salinity section (Fig. 11, upper 



13 



