Abstract
Semidiurnal tides are important factor to vertical mixing, substance transportin and exchange of sea water in semi-enclosed bay. The present work is intended to declare the variation of M2 and S2 tidal amplification the inner part and the outer part of Ariake Bay, Ise Bay and Tokyo Bay by using the harmonic analytical tidal data. As a result of this research, it becomes clear that i)a negative Kendall's rank correlation not only the M2 tidal amplification and the M2 tidal amplitude at the outer sea, but also between the S2 tidal amplification and the M2 tidal amplitude is found in Ariake Bay and Tokyo Bay., ii)the M2 tidal amplitude in 2000s was the smallest value over the past 30 years.
