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Zhang, D.*; Hu, X.*; Chen, T.*; Abernathy, D. L.*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Kofu, Maiko; Foley, B. J.*; Yoon, M.*; Choi, J. J.*; et al.
Physical Review B, 102(22), p.224310_1 - 224310_10, 2020/12
Times Cited Count：6 Percentile：31.26(Materials Science, Multidisciplinary)Onitsuka, Go*; Yanagi, Tetsuo*; Uno, Itsushi*; Kawamura, Hideyuki; Yoon, J.-H.*; Yamanaka, Yasuhiro*
Engan Kaiyo Kenkyu, 50(1), p.45 - 51, 2012/08
A seasonal variation of phytoplankton concentration is remarkable in the surface layer of the Japan Sea, because of a seasonal variation of solar radiation and nutrient. While, it is suggested that atmospheric perturbation such as typhoon effects a lower level ecosystem in the surface layer. An effect of atmospheric perturbation on the lower level ecosystem was estimated by means of an ocean general circulation model and a lower level ecosystem model in this study. Results of numerical experiments suggested that the atmospheric perturbation enhances a primary production in the Japan Sea.
Kawamura, Hideyuki; Ito, Toshimichi; Hirose, Naoki*; Takikawa, Tetsutaro*; Yoon, J.-H.*
Journal of Oceanography, 65(4), p.439 - 454, 2009/08
Times Cited Count：5 Percentile：14.69(Oceanography)This study aims at reproducing branches of the Tsushima Warm Current making use of an ocean general circulation model, which is important for movement of pollutants in the Japan Sea. The model was laterally exerted by volume transports measured by ADCP through the Tsushima Straits and the Tsugaru Strait. Sea level variation measured by coastal tide-stations as well as satellite altimeters is assimilated into the numerical model. It was demonstrated that an assimilation of sea level variation at the coastal tide-stations is useful to simulate oceanic condition in the nearshore region.
Hirose, Naoki*; Kawamura, Hideyuki; Lee, H. J.*; Yoon, J.-H.*
Journal of Oceanography, 63(3), p.467 - 481, 2007/06
Times Cited Count：30 Percentile：52.61(Oceanography)This study estimates and forecasts a realistic change of the Japan Sea by assimilating satellite measurements into an eddy-resolving circulation model. Suboptimal but feasible assimilation schemes of approximate filtering and nudging play essential roles in a system. The sequential updates of error covariance significantly outperforms the asymptotic covariance due to irregular sampling patterns from multiple altimeter satellites. The best estimate shows an average rms difference of 1.2 
C only to the radiometer data, and also explain about half of sea level variances measured by the microwave observation. It is demonstrated that a forecast persistency strongly depends on variable, depth, and location.
Kawamura, Hideyuki; Yoon, J.-H.*; Ito, Toshimichi
Journal of Oceanography, 63(2), p.243 - 253, 2007/04
Times Cited Count：13 Percentile：26.42(Oceanography)Water masses in the subsurface and intermediate layer are formed vigorously due to strong winter convection in the Japan Sea. Taking it into account that a part of pollutants is carried into the layer below the sea surface together with such water masses, it is significant to estimate a formation rate and turnover time of water masses to study a fate of pollutants. This study aims to estimate the formation rate and turnover time of water masses by using a three-dimensional ocean circulation model and particle chasing method. The total formation rate of water masses below the sea surface amounts to about 3.63 Sv in the Japan Sea. The formation rates of the Upper portion of the Japan Sea Proper Water (UJSPW) and Japan/East Sea Intermediate Water (JESIW) are estimated to be about 0.37 and 1.51 Sv, respectively. An estimate of turnover time shows that the UJSPW and JESIW circulate in the subsurface and intermediate layer with time scales of about 22.6 and 2.1 years, respectively.
Kawamura, Hideyuki; Yoon, J.-H.*; Ito, Toshimichi
Umi To Sora, 80(1), p.37 - 45, 2004/07
The Japan/East Sea Intermediate Water (JESIW) characterized by Salinity Minimum Layer (SML) with dissolved oxygen (DO) maximum was frequently observed in the Japan Sea. It is suggested that the origin of the JESIW is the coastal fresh water along the Primorye and North Korean coasts. The fresh water near the subpolar front along 40N advected from the coastal region has the possibility to sink into intermediate depth. This study aims to understand the formation mechanism of the JESIW by using the three-dimensional nested model. The results show that 1/18-resolution model can reproduce the strong downward velocity with the maximum of about 0.05 cm/s along the subpolar front in the Japan Sea. It results in the patch of low salinity water in the intermediate depth, which is consistent with the observational result. It is indicated that the high-resolution model is useful to reproduce the JESIW, since it can reproduce the meso-scale phenomenon such as baroclinicity near the frontal area, which is an important factor for surface water transport into the intermediate depth.
Onitsuka, Go*; Yanagi, Tetsuo*; Uno, Itsushi*; Kawamura, Hideyuki; Yoon, J.-H.*; Yamanaka, Yasuhiro*
no journal, ,
It is suggested that seasonal variation of phytoplankton concentration in the surface layer is remarkable in the Japan Sea and it is additionally reported that increase of phytoplankton concentration is found due to synoptic scale meteorological perturbation. In this study, effect of synoptic scale meteorological perturbation and deposition of nitrogen from atmosphere on primary production in the Japan Sea is estimated in numerical experiments. Short period oscillation of primary production due to synoptic scale meteorological perturbation is dominant between April and November in the numerical experiments. It is suggested that the primary production in the Japan Sea is supported by supply of nutrient due to synoptic scale meteorological perturbation by about 5% and that from atmosphere by about 2%, respectively.
Kawamura, Hideyuki; Ito, Toshimichi; Hirose, Naoki*; Yoon, J.-H.*; Takikawa, Tetsutaro*
no journal, ,
An assessment system for oceanic environment in the Japan Sea has been developed at Japan Atomic Energy Agency. Realistic reproduction of oceanic condition such as current and temperature is necessary to calculate movement of materials in the ocean. A circulation in the Japan Sea is strongly effected by the Tsushima Warm Current through the Tsushima Straits and the Tsugaru Warm Current through the Tsugaru Strait. In this study, an ocean general circulation model was drived by realistic volume transports of the Tsushima Warm Current and the Tsugaru Warm Current observed by Kyushu University and JAEA, respectively. In addition, the satellite altimeter data and sea surface height at coastal stations were assimilated by the Kalman filter. Model results well reproduced current field along the Japanese coast observed from September to October in 2000.
