69
degrees step. We employed two HF ocean radars at Sawara site and Kinaoshi site in
order to observe current vectors (Fig. 1). Sea echoes over the range of 90 km can be
detected by our system in good conditions(Ohno et al., 1993). A doppler spectrum
obtained at every 1.5 km in the range direction. Ocean currents of all radar beam
directions were obtained every two hours. In order to study COC, we made maps of
daily-mean ocean current vectors with neglecting of tidal components by operation of 25
hours running mean..
2.2 Satellite observation and image analysis
NOAA-12 Advanced Very High Resolution Radiometer (AVHRR) data were
collected from January to March 1995. These data were received at the Meteorological
Satellite Center of Japan Meteorological Agency. For the AVHRR thermal infrared data,
in-flight calibration was first carried out and the calibrated data then processed to remove
geometric distortions by use of an procedure described by Saitoh (1995). A digitized
coast line and geographical mark were superimposed on the geometric corrected image.
By using infrared images, It is able to identify Coastal Oyashio water mass because it is
relatively low temperature to warm adjacent waters.
3. Results and Discussion
The data shown in Fig.2 of the synoptic views of surface currents provided by the
radar system from January 21 to 24, 1995. Distribution of Coastal Oyashio water is
shown in Fig.3 in January 22 and 24, 1995. On January 22, COC flows with speed of 10
cm/s to 20 cm/s from the east to the west in the mouth of the Funka Bay (Fig.2 b). On
January 22, Coastal Oyashio water do not reach to offshore of Muroran (Fig. 3a). After
two days, Coastal Oyashio water arrives to the mouth of the Funka Bay and some water
intrudes to the Bay (Fig. 3b). There is a time lag of about two days between the
movement of Coastal Oyashio water and the change of COC, then we can identify the
intrusion of Coastal Oyashio water from infrared images on January 24.
Fig. 4 and Fig.5 are also time series views of surface currents and distribution of
Coastal Oyashio water in the period of early March, 1995, respectively. COC flows
with speed of over 50 cm/s from the east to the west in the mouth of the Funka Bay in
March 1 (FIg.4 b). There is also a time lag of about two days between the appearance of
strong westward surface currents and the intrusion of Coastal Oyashio water to the
Funka Bay. These are at least two evidences of the intrusion of Coastal Oyashio water
to the Bay in the period of this study.
The time series of daily averaged surface currents at PI is compared with daily