84 
3. Observation 
3.1 Observation with HFOSR 
Each ORO/CRL HFOSR was set at Ohkuma and Hirono (#1 and #2, see Figure 1). 
HFOSR#l at Ohkuma scanned from 90° to 172.5° and HFOSR#2 at Hirono from 7.5° to 
90° clockwise to the north at an interval of 7.5°. In the observation period, there was 
intermittent period of data loss of HFOSR#2 early in March because of the failure of radar 
control personal computer. Finally the data from 18 March to 3 April 1993 were used for 
an analysis. HFOSR data were in good condition from near the coast to 75 km off the 
coast at this time. 
When the current velocity changes vertically, the velocity from the surface to the depth 
1/2 ;r times of the wavelength of the ocean surface current influence the phase velocity of 
the ocean surface wave (Barrick et al., 1977). Therefore the ocean surface current by 
HFOSR can be defined as an average from the surface to the depth of about lm. 
The synthetic ocean surface velocities were calculated by two radial velocity 
components measured by each HFOSR once every 2 hours without timely interpolating. 
As the radial space resolving power of HFOSR was 1.5 km, the synthetic surface velocity 
was spatially interpolated in 1 km X 1 km grid map. 
3.2 Observation with moored current meter 
The current velocities were measured by moored P-RCM4 current meters at 2 meter 
depth below the surface every 15 minutes. The location of the current meters from about 1 
km to 8 km off the coast as shown in Figure 1. ORO/CRL HFOSR#l could not measure 
the radial current velocity around at the St.7 firmly obstructed by the land. Therefore the 
current meter data except for at St. 7 were used and timely averaged in 2 hours running 
mean for comparison with the synthetic current velocities by HFOSR. 
4. Comparison of both data 
Table 2 Results of comparison and correlation of ocean surface velocities 
Station of 
Current 
Meter 
RMS 
Difference 
Correlation 
Coefficient 
Mean 
Residual 
STD 
of Residual 
Regression Analysis 
Gradient 
Intercept 
Speed 
Dir 
Speed 
Dir 
Speed 
Dir 
Speed 
Dir 
Speed 
Dir 
Speed 
Dir 
St.cl 
7.10 
37.65 
0.87 
0.92 
5.08 
21.12 
6.41 
33.51 
0.92 
0.96 
4.58 
15.10 
St.c2 
22.40 
60.30 
0.55 
0.87 
11.36 
38.26 
16.96 
51.07 
1.02 
0.97 
14.35 
31.06 
St.c3 
8.44 
45.70 
0.94 
0.90 
4.39 
27.87 
5.64 
44.24 
1.12 
0.98 
4.07 
11.00 
St.c4 
7.25 
46.43 
0.86 
0.89 
4.78 
26.34 
5.94 
38.38 
0.74 
0.92 
7.22 
21.48 
St.c5 
42.21 
85.02 
0.33 
0.76 
21.03 
45.58 
28.44 
60.55 
1.40 
0.74 
27.02 
44.03 
St.c6 
8.25 
29.36 
0.87 
0.95 
5.75 
18.31 
7.54 
29.39 
1.08 
1.02 
1.63 
1.88 
St.c8 
12.96 
57.11 
0.71 
0.82 
9.30 
37.23 
12.10 
56.98 
1.08 
0.93 
3.30 
-4.11 
Mean 
15.52 
51.65 
0.73 
0.87 
8.81 
30.67 
11.86 
44.87 
1.18 
0.93 
8.88 
17.21 
Mean 
Except 2, 5 
8.80 
43.25 
0.85 
0.90 
5.86 
26.17 
7.53 
40.50 
1.17 
0.96 
4.16 
9.89 
Table 2 shows the result of comparison of both velocities and of correlation analysis. 
The number of the data was 171 respectively. The rms differences of speed at St.cl, 
St.c3, St.c4, St.c6 and St.c8 are small less than 10 cm/s, indicating good agreement of