Propagation of semi-diurnal internal tides observed off fukushima, along the east coast of Japan

Takeshi Matsuno

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1 Citation (Scopus)


Analysis of current velocity and temperature records obtained from moored buoy systems deployed off the east coast of Japan reveals the intermittent occurrence of semi-diurnal internal tides and their manner of propagation. The internal tidal waves clearly propagate toward the shore, which is confirmed by cross-correlation of the onshore current velocity and temperature between neighboring stations. The propagation speed of the internal tide increases with water depth except in the area furthest offshore. In this area, motions near the second mode seem to occur occasionally, while in the nearshore area the motions for the most part consist of the first mode. Through harmonic analysis, it is shown that the M1 internal motions were not vertically homogeneous. That is, the internal motions are greater at the lower level in the nearshore area while they are greater at the upper level in the offshore area. Pathways along which the energy of the internal tide should propagate are estimated in such a way that the characteristic curves pass through the area over which relatively large onshore/offshore M2 velocity is distributed. The movement of the characteristic ray of a certain phase explains the observed phase velocity estimated from the cross-correlation diagrams. Internal motions around the characteristic ray were pronounced in a rather wide area. Thus, it is suggested that the generation region of the internal tide in the present study area might be relatively wide.

Original languageEnglish
Pages (from-to)138-151
Number of pages14
JournalJournal of the Oceanographical Society of Japan
Issue number4
Publication statusPublished - Aug 1 1991

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Soil Science
  • Engineering(all)
  • Earth-Surface Processes
  • Earth and Planetary Sciences(all)


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