Surface Currents Observation in the Sea off Fukushima
with Two HF Ocean Surface Radars
Shin'ichi Sakai*, Masafumi Mizutori*, Hiroshi Kuroiwa** and Akitsugu Nadai***
* Central Research Institute of Electric Power Industry
** National Space Development Agency of Japan
*** Okinawa Radio Observatory, Communications Research Laboratory
Abstract
Central Research Institute of Electric Power Indus try (CRIEPI) and
Okinawa Radio Observatory(ORO), Communications Research
Laboratory(CRL) has observed ocean surface currents in the sea off
Fukushima by two ORO/CRL HF ocean surface radars(HFOSR) from
March 5 to April 3, 1993. The synthetic ocean surface current
velocities by two HFOSRs were compared with the field data
simultaneously observed by seven current meters to estimate the
applicability of ORO/CRL HFOSR to the monitoring of ocean surface
currents. The correlation of both data varied with the locations of
current meters where a cross angle of each HFOSR beam and water
depth varied. Except for two current meter stations which HFOSR’s
beam was obstructed by lands, the correlation showed good
agreement with the mean rms difference 8.8 cm/s in speed and 43.3°
in direction. The characteristics of ocean surface currents and the
response of ocean surface currents to wind forcing in the sea off
Fukushima were discussed from a series of HFOSR data.
1. Introduction
Okinawa Radio Observatory(ORO), Communications Research Laboratory(CRL) has
developed high frequency ocean surface radar(HFOSR) since 1987, and completed the
first ORO/CRL HFOSR in 1988 and the second one in 1991.
Tokuda et al. (1993) observed ocean surface currents in the sea off Tanegashima for
about a month with two ORO/CRL HFOSRs locating at Tanegashima and Yakushima
respectively. They compared the radial surface current velocities measured by each
HFOSR with that by a current meter moored 13m below the surface. Their result showed
good agreement with respect to correlation coefficient and the standard deviation.
Central Research Institute of Electric Power Industry (CRIEPI) and ORO/CRL
cooperated to measure the ocean surface currents in the sea off Fukushima (see Figure 1)
by two ORO/CRL HFOSRs and by eight moored current meters from 5 March to 3 April
1993. In the following sections, we estimate the applicability and practicability of HFOSR
to the monitoring of surface ocean currents by comparing the synthetic ocean surface
current velocities by two ORO/CRL HFOSRs with the data by current meters. The
characteristics of currents in the sea off Fukushima and the influence of wind forcing to
the surface currents are also discussed.
