VARIATION OF THE KUROSHIO NEAR THE JAPAN ISLANDS 623 



The most distinguished one was seen irom March to April, 1952. 

 The period was 20-30 days and the wave height was 30-50 cm. As the 

 number of waves is only a tew, it can not be decided whether this is a 

 durable phenomenon or not. But it is clear that this is due to the trans- 

 lation of the Kuroshio from the large range of variations. 



From May to September 1952, there appeared a periodic change of 

 sea level of much smaller amplitude than the former one. Figure 12 

 shoAvs the 5-day moving average of mean sea level. The mean of wave 

 height was 5 cm. over a period of 14 days. As the amplitude of this 

 wave is rather small, it is not possible to conclude that this is due to the 

 oscillation of the Kuroshio. But it may not be the wave of astronomical 

 origin, for if it is one of the astronomical tide, it must appear in every 

 time and place. Whether this wave is progressive or not, and also its 

 wave length and velocity, can not be decided on account of lack of ma- 

 terials. 



(iii) In September 1951 and 1952 the Kuroshio was to the north of 

 Hachijo-sima in both cases. But the monthly mean level was higher 

 about 34 cm. in 1952 than in 1951, and the difference between Hachijo- 

 sima and Ito was 27 cm. in two cases. The difference of sea levels on 

 both sides of the Kuroshio is proportional to the mean velocity of the 

 Kuroshio. Therefore, this means that the Kuroshio was stronger in 

 September 1952 than in 1951. In fact, from the observation, the Kuro- 

 shio was very strong in the summer of 1952 as compared with usual 

 years. Hachijo-sima is not the most suitable position to know the 

 strength of the Kuroshio, for it often comes out of the stream. 



It may be very important for oceanography to know the annual 

 and secular variation of the Kuroshio by observation of sea level at 

 some adequate places. 



Conclusion 

 We have described some example of variation of the Kuroshio, but 

 the variation of the Kuroshio can not be cleared up without the co- 

 operation of the scientists of all nations around the Pacific, for the 

 Kuroshio is only a fraction of the great circulation of the Pacific Ocean. 



References 



M. Uda. On the Correlated Fluctuation of the Kuroshio Current and the 

 Cold Water Mass. 



C. O'D. ISEi-iN. Preliminary Report on Long Period Variations in the Trans- 

 port of the Gulf Stream System. Papers in Phys. Oceanogr. and Meteor. 

 Vol. VIII, No. 1. 



E. C. La Fond. Variations of Sea, Level on the Pacific Coast of the United 

 States. Jour. Marine Research. Vol, 2. 1939, 



