Journal of Oceanography, Vol. 65 (No. 4), pp. 439-454, 2009
Hideyuki Kawamura1*, Toshimichi Ito1, Naoki Hirose2, Tetsutaro Takikawa3 and Jong-Hwan Yoon2
1Research Group for Environmental Science, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Shirakata-shirane, Tokai-mura 319-1195, Japan
2Center for East Asian Ocean-Atmosphere Research, Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
3National Fisheries University, Nagata-honmachi, Shimonoseki 759-6595, Japan
(Received 11 July 2008; in revised form 19 February 2009; accepted 22 February 2009)
Abstract: The branches of the Tsushima Warm Current (TWC) are realistically reproduced using a three-dimensional ocean general circulation model (OGCM). Simulated structures of the First Branch and the Second Branch of the TWC (FBTWC and SBTWC) in the eastern Japan Sea are mainly addressed in this study, being compared with measurement in the period September-October 2000. This is the first numerical experiment so far in which the OGCM is laterally exerted by real volume transports measured by acoustic Doppler current profiler (ADCP) through the Tsushima Straits and the Tsugaru Strait. In addition, sea level variation measured by tide-stations along the Japanese coast as well as satellite altimeters is assimilated into the OGCM through a sequential data assimilation method. It is demonstrated that the assimilation of sea level variation at the coastal tide-stations is useful in reproducing oceanic conditions in the nearshore region. We also examine the seasonal variation of the branches of the TWC in the eastern Japan Sea in 2000. It is suggested as a consequence that the FBTWC is continuous along northwestern Honshu Island in summertime, while it degenerates along the coast between the Sado Strait and the Oga Peninsula in other seasons. On the other hand, a mainstream of the SBTWC exists with meanders and eddies in the offshore region deeper than 1000 m to the north of the Sado Island throughout the year.