Copyright © The Oceanographic Society of Japan. Observation of the Soya Warm Current Using HF Ocean Radar

Three High Frequency (HF) ocean radar stations were installed around the Soya/La Perouse Strait in the Sea of Okhotsk in order to monitor the Soya Warm Current (SWC). The frequency of the HF radar is 13.9 MHz, and the range and azimuth reso-lutions are 3 km and 5 deg., respectively. The radar covers a range of approximately 70 km from the coast. The surface current velocity observed by the HF radars was compared with data from drifting buoys and shipboard Acoustic Doppler Current Profilers (ADCPs). The current velocity derived from the HF radars shows good agree-ment with that observed using the drifting buoys. The root-mean-square (rms) differ-ences were found to be less than 20 cm s–1 for the zonal and meridional components in the buoy comparison. The observed current velocity was also found to exhibit reason-able agreement with the shipboard ADCP data. It was shown that the HF radars clearly capture seasonal and short-term variations of the SWC. The velocity of the Soya Warm Current reaches its maximum, approximately 1 m s–1, in summer and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is ap-proximately 40 km. The surface transport by the SWC shows a significant correla