Kyushu University Academic Staff Educational and Research Activities Database
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Kaoru Ichikawa Last modified date:2017.12.05

Associate Professor / Interdisciplinary Graduate School of Engineering Sciences, Department of Earth System Science and Technology, Environmental Metrology
Division of Earth Environment Dynamics
Research Institute for Applied Mechanics

Graduate School

Academic Degree
Field of Specialization
Physical Oceanography
Outline Activities
Researches for providing synoptic views of ocean currents in coastal and marginal seas, where small and fast-moving phenomena are dominant, are conducted by mainly analyzing remote sensing (satellite and ocean radar) data; they include development of the coastal altimetry, sea surface height measurements by the GPS interferometry, cheap & robust surface drifting buoys, and monitoring system using reflected GNSS signals at the sea surface.
Such synoptic views will be used to study the movement/diffusion of materials/physical properties in the upstream Kuroshio area, which could be caused by variations of the Kuroshio due to interaction with westward-propagating mesoscale eddies in the Pacific Ocean originated from far eastern areas.

Except these research activities, I have committed educational activities in Interdisciplinary Graduate School of Engineering Science, and academic/social activities as a council member of Japan Oceanographic Society and Japan-French Oceanographic Society.
Research Interests
  • GNSS Reflectometry of Ocean Waves, Tides and Height
    keyword : GNSS Reflectometry, Sea surface height, Sea surace waves, full-time monitoring
  • Sea surface dynamic height measurements in coastal areas and degree of the geostrophy
    keyword : coastal area, GPS, satellite altimetry, geostrophic current, wind-driven current, tidal current
  • Optimal analysis of satellite altimetry data
    keyword : altimetry, optimal interpolation, objective mapping, satellite oceanography
    1988.04~2002.03A series of data processing methods are investigated to utilize satellite altimetry data in physical oceanography. They include improvement of marine geoid data by oceanographic observational data and removement of orbit error by an optimal interpolation method..
  • Interaction between mesoscale eddies and the Kuroshio
    keyword : Kuroshio Extension, mesoscale eddies, satellite altimetry, detached ring
    1993.04Using satellite altimetry data, interactions between mesoscale eddies and the Kuroshio and the Kuroshio Extension have been investigated. A series of phenomena, as pinching off of a cyclonic cold ring from the Kuroshio Extension, westward propagation of the ring, and coalescense of the ring into the Kuroshio, is clearly described. In addition, variations of the volume transport and position of the Kuroshio due to offshore mesoscale eddies are investigated..
  • Impacts of offshore variations on coastal sea level changes
    keyword : coastal sea level, mesoscale eddies, western boundary current, satellite altimetry
    2002.04Impacts of offsore variations are investigated on coastal sea level variations longer than a month. Offshore variations are determined from satellite altimetry data, and compared with coastal sea level variations measured by tide gauges. Mesoscale eddies dominates variations on islands in an open ocean. Meanwhile, effect of Kuroshio variations is found more important to coastal sea levels south of Japanese main islands..
Current and Past Project
  • Various oceanic parameters such as sea surface height, winds and sea ice, are important for monitoring global environmental changes, and also they are necessary for weather forecast, maritime route determination, fishing, and ocean drilling. Satellites have provided wide and repeated observations that would be never acquired by research vessels alone, but due to limited number of expensive satellites, they still cannot capture fast-moving or rapidly-changing phenomena, such as the Tsunami propagation and the growth of typhoons. Meanwhile, new remote sensing technique using micro satellites that measure reflection of GNSS signals (GNSS-R) can provide all-time global observations, although its accuracy is less than the expensive special satellites. Such frequent observations would be most useful to monitor fast-moving or rapidly-changing significant signals, which are often related with disasters. In this project, fundamental relationships between GNSS-R and sea-truth data are obtained by in situ observations, and close cooperation between researchers of the ocean and space would be established.
  • Detection of Coastal Velocity Variations in the Tsushima Strait, CNES-ISRO SARAL/AltiKa Project;
    This proposal consists of two major targets. The first and fundamental one is to evaluate performances of the Ka-band altimeter in the coastal region and to establish proper data processing methods for estimation of coastal surface geostrophic velocity anomaly, by comparisons with the high-resolution surface velocity data obtained by the High-Frequency (HF) radar system located in the Tsushima Strait between Japan and Korea. The other and advanced target is to study causes and effects of the velocity variations in the Tsushima Strait by extending the spatially limited observation area of the HF radar system using multiple AltiKa sub-satellite tracks.
  • Variations of flow fields in the western North Pacific and surrounding marginal seas, CNES-EUMETSAT Ocean Surface Topography Science Team;
    The primary aim of this proposal is to understand variations of flow fields in the western North Pacific and surrounding marginal seas. Heat and volume transport of the Kuroshio and Oyashio current systems will be investigated by combining altimetry data with in situ observations and numerical models. At the same time, variations of the flow fields in the East China Sea and the Sea of Okhotsk will be also investigated. Those variations would be expected to have a possible relationship between the Kuroshio and Oyashio current systems, but they have not been described well due to their small-scale nature in marginal seas. Use of HF radar data with high spatio-temporal resolutions and improved accuracy of the altimetry data in marginal seas together with dense coverage by multi-satellite use would provide better insights of such variations.
    In this proposal, we shall continue in situ observations. They include hydrographic and mooring field observations, HF radars, and drifters. They are used for basic oceanographic studies, and may be eventually used as calibration/validation data for Jason-2/OSTM by any other OST-ST groups. Similarly, we shall maintain operational real-time Japan-GODAE data products produced by operating an ocean data assimilation system of JMA. Meanwhile, assimilated results from a more com-prehensive model will be used for basic studies.In addition, gravity changes due to huge oceanic motions such as a large Kuroshio meander will be examined by use of a dense network of accurate gravity field measurements in Japan. We intend to obtain new understandings of circulations in the western North Pacific through those aspiring studies.
  • "Study on the influence of global warming and rapid economic growth in the marine and atmospheric environments in the East Asia", RIAM, Kyushu University
Academic Activities
1. Fluid Dynamics to study Global Environment
Masayuki Oikawa, Masashi Kashiwagi, Keita Iga, Kaoru Ichikawa, Tetsuo Yanagi
Ed: Department of Earth System Science and Technology, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University.
1. XiFeng Wang, Kaoru Ichikawa, Coastal Waveform Retracking for Jason-2 Altimeter Data Based on Along-Track Echograms around the Tsushima Islands in Japan
, Remote Sensing, 9, 7, 2017.07.
2. XiFeng Wang, Kaoru Ichikawa, Effect of High-Frequency sea waves on wave period retrieval from radar altimeter and buoy data, Remote Sensing, 8, 764, 2016.09, [URL].
3. Akira Nagano, Kaoru Ichikawa, Hiroshio Ichikawa, Masanori Konda, Kiyoshi Murakami, Volume transports proceeding to the Kuroshio Extension region and recirculating in the Shikoku Basin, Journal of Oceanography, 69, 3, 2013.05, [URL].
4. Ichikawa Kaoru, Wen Chang Yang, Akihiko Morimoto, Yoshikawa Yutaka, Shigeo Sugitani, Wen-Shan Chiang, Jian-Wu Lai, En Yu Liang, Cho-Teng Liu, Chang-Wei Lee, Kei Yufu, Moeto Kyushima, Satoshi Fujii, Senjyu Tomoharu, Yoshihiko Ide, Preliminary results of the Japan-Taiwan joint survey on combining ocean radar data in the Kuroshio upstream region, Ocean Science Journal, 48, 1, 2013.03, [URL].
5. Akira Nagano, Kaoru Ichikawa, Hiroshio Ichikawa, H Tomita, H Tokinaga, Masanori Konda, Stable volume and heat transports of the North Pacific subtropical gyre revealed by identifying the Kuroshio in synoptic hydrography south of Japan, Journal of Geophysical Research, 115, C09002, 14pp, 115, C09002, doi:10.1029/2009JC005747, 2010.09.
6. Kaoru Ichikawa, Synoptic flow structures in the confluence region of the Kuroshio and Ryukyu current, Journal of Geophysical Research, Vol. 114, C06007, doi:10.1029/2008JC005213, 2009.06.
7. Kaoru Ichikawa, Kuroshio variations in the upstream region as seen by HF radar and satellite altimetry data, International Journal of Remote Sensing, 29(21), 6317-6326, doi:10.1080/01431160802175454, 2008.11.
8. Tokeshi, R., K. Ichikawa, S. Fujii, K. Sato and S. Kojima, Estimating the geostrophic velocity obtained by HF radar observations in the upstream area of the Kuroshio, Journal of Oceanography, Vol 63(4), 711-720, 2007.06.
9. Kaoru Ichikawa, Flow of abyssal water into Wake Island Passage: Properties and transports from hydrographic surveys, Journal of Geophysical Research, Vol. 112, C04008, doi:10.1029/2006JC004000, 2007.04.
10. Kaoru Ichikawa, Influence of the Kuroshio fluctuations on sea level variations along the south coast of Japan, Journal of Oceanography, 61, 5, 61, 979-985, 2005.09, [URL].
11. K. Ichikawa, N. Gohda, M. Arai and A. Kaneko, Variations of the Subtropical Counter-Current as seen by repeated ADCP and satellite altimetry data, Proceedings of The Indonesia Ocean Forum 2005 and the 13th PAMS/JECSS Workshop, 161-164, 2005.07.
12. Kaoru Ichikawa, Estimating the Kuroshio axis south of Japan using combination of satellite altimetry and drifting buoys, Journal of Oceanography, 60, 2, Vol. 60, 375-382, 2004.03, [URL].
Works, Software and Database
1. Ocean Flux data sets estimated with satellite remote sensing data. This includes sea surface fluxes such as shortwave radiation, longwave radiation, latent heat, sensible heat and momentum, togather with related quantities as sea-surface air temperature, sea surface height and surface velocity. The data set is available via internet (
1. , [URL].
  • Okada Prize, Japan Oceanographic Society, 2001
Other Educational Activities
  • 2001.03.
Professional and Outreach Activities
Researcher of Japan Agency for Marine-Earth Science and Technology, 2000-2010
Visiting Scientist in Center for Marine Environmental Studies, Ehime University, 2001-
CNES/EUMETSAT Ocean Surface Topography Science Team Principal Investigator, 2006-
CNES/ISRO SARAL/AltiKaScience Team Principal Investigator, 2010-
Member of Marine-Space Cooperation Committee, 2010-
NASA CYGNSS Science Team, Principal Investigator, 2015-
CNES TOSCA_SWOT2016 Science Team, Co investigator, 2015-.