Fig. 2b shows the time series of the current and temperature at station HI during the same period as those at EN. The increased westward current and steep rise of temperature occurred on January 9, the same day as the thermal front passing at EN. The maximum westward current was 0.52 ms-1 at 5:00 at HI, which is nearly the time of the temperature rise. The westward current at HI and the southward current at EN indicate an anticlockwise current in the bay, as easily seen from the current direction and the observation sites (Fig. 1). The maximum speed was smaller at HI than at EN, and the former led the latter by about 18 h. In the current records at HI (Fig. 2b), the tidal current fluctuations existed through the entire period with amplitude of 0.1-0.2 ms-1 as well.
The signal in relation to the strong current is extracted by the least-squares method for removal of the four major tidal constituents, i.e., M2, S2, K1, and O1 tides, and is shown in Fig. 3. Before January 6, there were weak southward currents at EN and eastward currents at HI. After January 7, the current variations at both sites were similar to each other, and the strong current appeared on January 9. The maximum speed of the current was 0.65 ms-1 at EN and 0.45 ms-1 at HI. Therefore, the signal in relation to the Kyucho already appeared on January 7 at both sites. The current records indicate undulations from January 7 with the period of about 2d, and the maximum on January 9. The undulations continued until January 13, as estimated from the record at HI.
Fig. 3 The time series of currents after removing the tidal signal at EN and HI.
