The Prompt Report of the Oceanographic Condition indicates that the Kuroshio was flowing in the straight path at the time of each cruise. However, the daily variation of the sea level difference shown in Fig.2 suggests that the status of the Kuroshio flow was somewhat different, cruise by cruise: the sea level difference at the time of Cruise I was near to or smaller than 25 cm, suggesting that the flow nature would be similar to that at the time of the large meander path. The sea level difference is high and stable at the time of Cruise II. It had decreased considerably during Cruise III, but it still remained above the threshold value of 25 cm. In Cruise IV, the sea level difference was very stable, but its value was only slightly higher than the threshold value.

　

Fig.3. Current distributions in the period from June 24 to June 25 (Cruise II) for three depths of 5 m (upper figure), 25 m (middle figure) and 75 m (lower figure). The current vector is given as an average value over each observation time of 1 min. length, which contains 4-5 raw observed data points. The current data at 75 m along Line A were erroneous as the measurement was made near the bottom (not shown here). The magnitude of the current vector is indicated at the left-lower corner of the figure (in kt = 0.5 m/s).

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