Kyushu University Academic Staff Educational and Research Activities Database
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yoshinobu wakata Last modified date:2018.07.02



Graduate School
Undergraduate School
Other Organization
Other


E-Mail
Academic Degree
Doctorate of Science
Field of Specialization
Dynamics of ocean and atmosphere
Outline Activities
Ocean turbulence is investigated using Large Eddy Simulation (LES). Furthermore, the dynamic processes in the East China Sea has been researched through the numerical general circulation model, simple theoretical model, and satellite data analysis.
Research
Research Interests
  • Numerical Simulation of Ocean turbulence
    keyword : ocean turbulence, Large Eddy Simulation
    2009.01.
  • Simulation of Venusian Atmosphere
    keyword : Venusian Atmosphere
    2000.03~2010.12.
  • Interannual variability of Kuroshio volume transport
    keyword : Kurohio volume transport
    1997.04Interannual variability of Kuroshio volume transport was investigated by an ocean general circulation model and a theoretical simple model..
  • Seasonal variability of Sea surface height
    keyword : Sea surface height, seasonal variability
    1999.01~2002.03The seasonal variability of sea surface height in the Pacific ocean was investigated through the Satellite data analysis and model simulation..
  • Resonance of equatorial Kelvin waves
    keyword : equatorial waves, Kelvin waves, resonance
    1997.01~2001.03The Kelvin wave, excited by an intraseasonal wind forcing with a 40-day period over the western Pacific Ocean, was simulated using an ocean general circulation model, and was investigated by the use of spectral analysis..
  • Frequency-wavenumber spectra of equatorial waves detected from satellite altimeter data
    keyword : equatorial waves, Kelvin waves, Rossby waves
    2005.06~2009.03The sea surface height anomaly in the Pacific equatorial area was separated into equatorial modes using satellite altimeter data. The power-spectral density (PSD) was obtained for the east-west wavenumber and frequency for each separated mode. The PSD distribution was compared with the theoretical dispersion curve for the equatorial modes derived by Matsuno (1966). The low-order Rossby modes have a high-density distribution that is slightly lower than the theoretical dispersion curve, but the Kelvin mode and the higher Rossby modes have high-density distribution that almost matches each dispersion curve. Results of analyses of satellite observational data show that wave motion near the equator mainly shows characteristics of equatorial waves, especially for a short time scale..
  • Ocean dynamics of East China Sea
    keyword : East China Sea, sea surface height
    2005.03Variability of the flow field in the East China Sea is investigated using an ocean general circulation model and satellite altimeter data..
Academic Activities
Books
1. T. Yamagata, Y. Wakata, Ocean-Atmosphere Interactions, Kluwer Aca. Pub., Chap.5, 143-195, 2003.02.
Papers
1. Yoshinobu Wakata, LES study of vertical eddy diffusivity estimation in bottom boundary layers, Journal of Physical Oceanography, Accepted, 2018.07.
2. 和方 吉信, Some properties of tidal currents estimated from analytical and LES simulation studies, Journal of oceanography, DOI 10.1007/s10872-013-0204-6, 69, 737-751, 2013.11, Some features of tidal current ellipses near the ocean floor are estimated from the bottom-limit solutions of the tidal equations with constant eddy viscosity. It is verified that a clockwise rotating ellipse becomes broad descending through the bottom boundary, whereas a counterclockwise ellipse becomes narrow except near the critical latitude. The major axis of an ellipse near the floor is directed 45° leftward (rightward) against that of the overlying tidal flow ellipse poleward from the critical latitude in the northern (southern) hemisphere. Equatorward from the critical latitude, the major axis near the floor lines up with that of the overlying tidal current ellipse in both hemispheres. The retrograde rotating hodograph against the overlying clockwise tidal hodograph appears near the floor around the critical latitude. These features are confirmed from the numerical studies using the large eddy simulation model. The deflection of the major axis poleward from the critical latitude is a little smaller, about 19°. Furthermore, the effects of nontraditional Coriolis force resulting from the horizontal component of the earth-rotating vector on the development of turbulence were investigated. When the diurnal tidal current is directed westward, the effective vertical eddy viscosity becomes maximum with developing turbulence. While in the case of a semidiurnal tide, a northward tidal current is preferred for turbulence development..
3. Y. Wakata, Dependence of seafloor boundary layer thickness on the overlying flow direction: a large eddy simulation study, Journal of Oceanography, DOI 10.1007/s10872-011-0068-6, 67, 667-673, 2011.10.
4. Y. Wakata, Seasonal Variability of the Sea Surface Height in the East China Sea along the China Coast: A Model Study, Journal of Oceanography, 65, 281-286, 2009.04.
5. A. Kido and Y. Wakata, Multiple equilibrium states appearing in a Venus-like atmospheric general circulation model, J. Meteor. Soc. Japan, 86, 969-979, 2008.12.
6. Y. Wakata, Frequency-wavenumber spectra of equatorial waves detected from satellite altimeter data, Journal of Oceanography, 63, 483-190, 2007.06.
7. Y. Wakata,T. Setou, I. Kaneko, H. Uchida, S. Imawaki, Interannual variability of the Kuroshio transport passing through the 137°E meridian in an OGCM related to the North Pacific windstress, Journal of Oceanography, 25-35, 2006.02.
8. M. Ioualalen, Y. Wakata, Y, Kawahara, Y. Gouriou, D. Varillon, Variability of the sea surface salinity (SSS) in the western tropical Pacific: On the ability of an OGCM to simulate the SSS, and on the sampling of an operating merchant ship SSS network, Journal of Oceanography, 10.1023/A:1022876708829, 59, 1, 105-111, 2003.01.
Membership in Academic Society
  • Advanced Marine Science and Technology Society
Awards
  • Seasonal variability of sea surface height in the East China Sea and the Yellow Sea
Educational
Educational Activities
Ocean-Atmosphere Interactions, Kluwer Acad. Pub. Chap.5 143-193