Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
Kaoru Ichikawa Last modified date:2019.06.13

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


Presentations
1. Kaoru Ichikawa (RIAM, Kyushu Univ), Osamu Isoguchi(RESTEC), Sea Surface Height estimation in the East China Sea
, CYGNSS Science Team Meeting, 2019.06.
2. Kaoru Ichikawa (RIAM, Kyushu Univ), Shin'ichiro Kako (Kagoshima Univ), Hiroyuki Tomita (ISEE, Nagoya Univ), Typhoon LAN (2017) wind speeds compared with new AMSR2 high-speed product, CYGNSS Science Team Meeting, 2019.06.
3. Shin'ichiro Kako (Kagoshima Univ), Hiroyuki Tomita (Nagoya Univ.), Kaoru Ichikawa (RIAM, Kyushu Univ) , Estimation of typhoon wind speed using CYGNSS observations: A case study of Typhoon Lan in 2017
, Japan Geoscience Union Meeting 2019, 2019.05.
4. Kaoru Ichikawa (RIAM, Kyushu Univ), Tatsuki Okumura (ESST Kyushu Univ), Masanori Konda (Grad. Sch. Sc., Kyoto Univ), Yasuyuki Baba (Dis. Prev. Res. Inst., Kyoto Univ.), GNSS-R altimetry using a Geostationary Satellite, Japan Geoscience Union Meeting 2019, 2019.05.
5. Osamu Isoguchi (RESTEC), Kaoru Ichikawa (RIAM, Kyushu Univ.) , Investigation of sea surface height detection by Global Navigation Satellite System Reflectometry (GNSS-R)
, Japan Geoscience Union Meeting 2019, 2019.05.
6. Xinyu Guo (Ehime University), Takeshi Matsuno (Kyushu University), Tomoharu Senju (Kyushu University), Kaoru Ichikawa (Kyushu University), Takahiro Endoh (Kyushu University), Eisuke Tsutsumi (Kyushu University), Ayako Nishina (Kagoshima University), Hirohiko Nakamura (Kagoshima University), Jing Zhang (Toyama University), Daisuke Hasegawa (Tohoko National Fisheries Research Institute), Naoki Yoshie (Ehime University), Toru Kobari (Kagoshima University), Mixing Processes in the Kuroshio region and their influence on the low-trophic ecosystem, Japan Geoscience Union Meeting 2019, 2019.05.
7. Kaoru Ichikawa (RIAM, Kyushu Univ.), Takuji Ebinuma (Coll. Engin., Chubu Univ.), Kei Yufu (RIAM), Masanori Konda (Grad. Sch. Sc., Kyoto Univ. ), Ryosuke Sakemi (RIAM), , Experimental GNSS-R altimetry on UAVs and vessels , The 20th Pacific-Asian Marginal Seas Meeting, 2019.03.
8. Kaoru Ichikawa (RIAM, Kyushu U), Takuji Ebinuma (Chubu U) and the GROWTH team , GNSS-R Altimetry for Support of Coastal Altimetry, 25 years of Progress in Radar Altimetry Symposium, 2018.09, [URL].
9. Kaoru Ichikawa (RIAM, Kyushu Univ., Japan), XiFeng Wang (Dalian Ocean Univ, China), Coastal Retracking using along-track waveform echograms in Seas of Indonesia, 11th Coastal Altimetry Workshop, 2018.06, [URL], A coastal retracking method using along-track waveform echograms is examined in Seas of Indonesia where complicated topography with numbers of islands prevents full use of satellite altimeters in spite of high depends. In other seas, the method has successfully eliminated bright parabolic shapes in echograms, namely unexpected strong reflection from calm water surface in semi-closed bays within a footprint of an altimeter. But the method is found not properly applicable in Seas of Indonesia. Large areas of high microwave reflectors, or slicks, are intermittently but frequently present in the sea even away from coasts, but they are not accounted in the method which eliminates bright parabolas from single-point reflectors in the echograms. The method is modified to include an additional process to detect presence of slicks in the echograms, which enables to estimate the sea surface height was to estimate the sea surface height in Seas of Indonesia..
10. Tetsutaro TAKIKAWA (Graduate School of Fisheries and Environmental Sciences, Nagasaki University), Akihiko MORIMOTO (CMES, Ehime University), Moeto KYUSHIMA (ISEE, Nagoya University), Kaoru ICHIKAWA (RIAM, Kyushu University), Masashi ITO (Japan Sea National Fisheries Research Institute, Japan Fisheries Research and Education Agency), Kei YUFU (RIAM, Kyushu University), Fortnightly variation of the Tsushima Warm Current on the continental shelf of the southwestern Japan Sea, 15th Annual Meeting Asia Oceania Geosciences Society, 2018.06, [URL].
11. Keisuke Arioshi, Shuhei Nishida, Yuya Machida, Takeshi Iinuma, Hiroshio Uchida, Akira Nagano, Takuya Hasegawa, Toru Miyama, Yasumasa Miyazawa, Masahide Wakita, Tatsu Kuwatani, Kan Aoike, Mikiko Fujita (JAMSTEC), Akira Kuwano-Yoshida (DPRI, Kyoto Univ.), Akiko To (IES, Academia Sinica, Taiwan), and Kaoru Ichikawa (RIAM, Kyushu Univ) , A Total Station Plan Combined with "chikyu" and DONET: a Trial of Simultaneous Observation from Seafloor to Atmosphere
, 15th Annual Meeting Asia Oceania Geosciences Society, 2018.06, [URL].
12. Keisuke Arioshi, Shuhei Nishida, Yuya Machida, Takeshi Iinuma, Hiroshio Uchida, Akira Nagano, Takuya Hasegawa, Toru Miyama, Yasumasa Miyazawa, Masahide Wakita, Tatsu Kuwatani, Kan Aoike, Mikiko Fujita (JAMSTEC), Akira Kuwano-Yoshida (DPRI, Kyoto Univ.), Akiko To (IES, Academia Sinica, Taiwan), and Kaoru Ichikawa (RIAM, Kyushu Univ), A total station plan combined with "Chikyu" and DONET: A trial of simultaneous observation from seafloor to atmosphere, 2018 European Geosciences Union General Assembly, 2018.04, [URL].
13. Hiroto Iuchi, Naoya Suzuki, Takenobu Michida (Kindai Univ), Takuji Waseda (The Univ of Tokyo), Hitoshi Tamura (Port and Airport Res Inst), Kaoru Ichikawa (Kyushu Univ) , Effect of observation tower on variability of the wind stress --Field observation and numerical simulation--, AGU Ocean Science Meeting 2018, 2018.02, [URL].
14. Keisuke Ariyoshi, Toru Miyama, Masahide Wakita, Yasumasa Miyazawa, Hiroshio Uchida, Akira Nagano, Shuhei Nishida, Yuya Machida, Tatsu Kuwatani, Takuya Hasegawa, Mikiko Fujita, Kan Aoike (JAMSTEC), Akira Kuwano-Yoshida (DPRI, Kyoto Univ), Kaoru Ichikawa (RIAM, Kyushu Univ), Akiko To (Academia Sinica, Taiwan), A total station plan combined with "Chikyu" and DONET: simultaneous observation from seafloor to atmosphere, AGU Ocean Science Meeting 2018, 2018.02, [URL].
15. K Ichikawa, @XF Wang , Coastal retracking using along-track echograms and its dependency on coastal topography, AGU Fall meeting 2017, 2017.12, [URL].
16. Hiroto Inouchi, Takeuchi Takemoto, Naoya Suzuki, Takuji Waseda, Hitoshi Tamura, 市川 香, Numerical Simulation of Wind Flow around an Ocean Observation Tower
--First Assensment of the Applicability of Numerical Simiulation --, JpGU-AGU Joint Meeting 2017, 2017.05.
17. Tetsutaro Takikawa, Akihiko Morimoto, Moeto Kyushima, Kaoru Ichikawa, Masashi Ito, Kei Yufu, Fortnightly variation of the Tsushima Warm Current after passing through the Tsushima Straits associated with internal tide, 19th Pacific-Asian Marginal Seas Meeting, 2017.04.
18. XiFeng Wang, Kaoru Ichikawa, Comparison with the coastal sea surface height retrieved from along-track Jason-2 continous waveforms and the HF ocean radar data in the Tsushima Strait
, 10th Coastal Altimetry Workshop, 2017.02, [URL], A new algorithm is proposed to retrieve sea surface height (SSH) from Jason-2 waveforms contaminated near coastal areas. Unlike the other algorithms such as ALES that detect contamination in each single waveform independently, continuous waveforms along a track are used at once to detect contamination referring consistency with adjacent points. In this study, Jason-2 waveforms near Tsushima Island, Japan are processed and found closer SSH retrieval to the coast than the other algorithms. The obtained SSH is compared with surface velocity observed by the HF ocean radar data in which tidal and wind-driven current components have been removed separately. Spatial smoothing is found necessary for better comparison, which emphasises importance of closer SSH retrieval in coastal areas, especially in narrow channels where the number of altimeter data tends to be insufficient..
19. Yukito Kitazawa, Kaoru Ichikawa, Hiroaki Akiyama, Takuji Ebinuma, Osamu Isoguchi, Noriaki Kimura, Masanori Konda, Nobuyuki Koguchi, Hitoshi Tamura, Hiroyuki Tomita, Yutaka Yoshikawa, Takuji Waseda, Progress Report on the GROWTH (GNSS Reflectometry for Ocean Waves, Tides and Height) Research Project
, American Geophysical Union 2016 Fall Meeting, 2016.12, [URL].
20. Kaoru Ichikawa, Kentaro Yokoo, XiFeng Wang, CT Liu, 松野 健, HW Chen, Kenichi Fukudome, DJ Doong, Volume transport variations in the Taiwan Strait in relation with the cross- and along-strait pressure gradients, Ocean Surface Topography Science Team (OSTST) Meeting 2016, 2016.11, Since 2008, an ADCP has been deployed at the bottom of “TaiMa” ferry, crossing the Taiwan Strait daily, to observe the volume transport in the strait. The obtained volume transport is linearly related well to the cross-strait sea level difference determined by tide gauges, and also approximately agrees with the along-track component of the wind stress without significant time lags. These suggest that the along-strait wind stress balances with the frictional force of the along-strait geostrophic current, which is proportional to the cross-strait sea level difference. Furthermore, discrepancy of the volume transport from the linear relationship with the along-strait local wind stress is compared with the SSHA field around Taiwan and Jason-2 along-track PISTACH altimetry data. Unfortunately, the SSHA filed is not reliable enough in the strait due to sparse sampling, Nevertheless, significant SSHA to the south of Taiwan, as a result of the Kuroshio variations caused by interaction with westward-propagating mesoscale eddies, are found related with such wind-independent volume transport variations with periods of several weeks..
21. Kaoru Ichikawa, Z.Y. Li, GROWTH team, Wave field observations by GNSS Reflectometry, 8th Program of the East Asian Cooperative Experiments (PEACE), 2016.08, [URL], Reflected signals at the sea surface often cause so-called multipath error in Global Navigation Satellite System (GNSS), such as GPS and GLONASS. However, they can also be used to retrieve surface wave field, i.e. the GNSS Reflectometry (GNSS-R) technique. Down-looking GNSS antennas have been deployed on observatory towers in swell-dominant Hiratsuka and swell-free Lake Biwa, as a part of a project “GNSS Reflectometry for Ocean Waves, Tides and Height (GROWTH)” funded by Japanese Ministry of Education, Culture, Sports, Science and Technology. Since the footprint size is small due to the lower altitude of the antennas, instantaneous reflections represents only a part of a surface wave. Reflected intensity varies with the dominant wave periods (approximately 2-3 seconds) in Lake Biwa, indicating variations of the sea surface slope. Meanwhile, high-frequency intensity variations were observed in Hiratsuka, which were mainly caused by interferometric variations induced by changes of the path length between the sea surface and the antennas due to sea surface elevations of swells. Wave field observations by other methods, including wave gauges, GNSS wave gauge drifters, altimeters and SAR imagery are also reviewed for comparisons with GNSS-R..
22. Kaoru Ichikawa, Hiroaki Akiyama, Takuji Ebinuma, Osamu Isoguchi, Noriaki Kimura, Yukihito Kitazawa, Masanori Konda, Nobuyuki Kouguchi, Hitoshi Tamura, Hiroyuki Tomita, Yutaka Yoshikawa, Takuji Waseda, Progress Report on the GROWTH (GNSS Reflectometry for Ocean Waves, Tides and Height) Research Project, European Geosciences Union General Assembly 2016, 2016.04.
23. 松野 健, Cho-Teng Liu, 福留 研一, Hsien-Wen Chen, Kaoru Ichikawa, Dong-Jiing Doong, Tomoharu Senjyu, Response of Volume Transport through the Taiwan and Tsushima Straits to the Wind Fields in the East China Sea, 2016 Ocean Sciences Meetin, 2016.02.
24. Kaoru Ichikawa, Variability of the Kuroshio in the upstream region, CLIVAR/JAMSTEC Workshop on the Kuroshio Current and Extension System: Theory, Observations, and Ocean Climate Modelling, 2016.01.
25. Takuji Ebinuma, Kaoru Ichikawa, Takuji Waseda, Yukihito Kitazawa, Hitoshi Tamura, Osamu Isoguchi, Hiroyuki Tomita, GNSS Reflectometry and Multi-Sensor Ocean Wave and Wind Monitoring at Hiratsuka Marine Observation Tower
, International Symposium on GNSS, 2015.11.
26. Xi-Feng Wang, Kaoru Ichikawa, Retrieval of coastal sea surface height from along-track continuous AltiKa data, 9th Coastal Altimetry Workshop and Ocean Surface Topography Science Team Meeting 2015, 2015.10, [URL], Waveforms of satellite altimeters are often contaminated in coastal areas by strong radar reflection from calm water in semi-closed bays or weak reflection from lands. Several algorithms have been proposed to retrieve the sea surface height (SSH) avoiding these contamination in a waveform, but such retrievals are independent for each single waveform and waveforms of the adjacent points have never been referred. In this study, along-track AltiKa 40 Hz data near Tsushima Island, Japan, are processed at once for each cycle to retrieve the coastal SSH accounting contamination in waveforms of the adjacent points. Since the reflection from a point source results in a parabolic shape in an echogram with latitude versus altimeter tracking gate, extremely strong echo values with parabolic shapes are first masked. For each tracking gate at each point, lost echo by land is roughly compensated based on the ratio of the land area in the altimeter’s footprint ring, then the Brown model is fitted to each modified waveform. The retrieved SSH shows reasonable values with no abrupt changes along tracks..
27. Tetsutaro Takikawa, Akihiko Morimoto, Shigeo Sugitani, Moeto Kyushima, Kaoru Ichikawa, Masashi Ito, Satoshi Fujii, Hironori Iwai, Jun Amagai, The Tsushima Warm Current in the southwestern Japan Sea measured by Long Range Ocean Radar and bottom mounted acoustic Doppler current profilers, 12th Annual Meeting Asia Oceania Geosciences Society, 2015.08, [URL], The Tsushima Warm Current flows through the Tsushima Straits into the continental shelf of the southwestern Japan Sea extending from the East China Sea. And then, the Tsushima Warm Current meets cold water in the lower layer in the deep basin of the Japan Sea. Previous studies have proposed some current patterns after passing through the Tsushima Straits, such as the single-meander, double-branch, and triple-branch patterns. However, the mean current paths and its variability are not yet fully understood. Long Range Ocean Radar has been measuring the sea surface current in the southwestern Japan Sea to observe the branches of the Tsushima Warm Current since May 2014. The frequency of radar is 9.2 MHz. The Long Range Ocean Radar can measure approximately 200 km range from the radar site, and its horizontal resolution is approximately 7 km along the beam. The sampling data interval is 30 minutes or 1 hour. The radar can measure the first branch of the Tsushima Warm Current along the Japanese coast and the second branch along the continental slope (about 200-m isobath). A set of five bottom mounted acoustic Doppler current profilers (ADCPs) with temperature sensor were deployed across the Tsushima Warm Current in the radar observation area from June to July 2014. During the ADCP observation period, the bottom cold water less than 8 degree C intruded over the continental shelf. The Tsushima Warm Current intensified on the continental shelf in the vicinity of the bottom temperature front..
28. Kaoru Ichikawa, Takuji Ebinuma, Hiroaki Akiyama, Yukihito Kitazawa, JAPAN's GNSS-R Research Team, Overview of JAPAN's GNSS-R Research Program for Ocean Observations
, 26th International Union of Geodesy and Geophysics, General Assembly, 2015.06.
29. Kaoru Ichikawa, Takuji Ebinuma, Hiroaki Akiyama, Yukihito Kitazawa, JAPAN's GNSS-R Research Team, Overview of GNSS-R Research Program for Ocean Observations at Japan
, GNSS+R 2015 Workshop, 2015.05.
30. Akihiko Morimoto, Shigeo Sugitani, Tetsutaro Takikawa, Moeto Kyushima, Kaoru Ichikawa, Satoshi Fujii, Hironori Iwai, Jun Amagai, Observation of the Tsushima Warm Current paths using Long Range Ocean Radar, 18th Pacific-Asian Marginal Seas Meeting , 2015.04, The Tsushima Warm Current (TWC) separates into 3 branches in the southwestern part of Japan Sea. Variations in the branches and its dynamics have been investigated for a long time. However, the branching of the TWC has been debated. In order to understand the branching of the TWC, current data with high spatial and temporal resolution are needed. We use the Long Range Ocean Radar (LROR) developed by National Institute of Information and Communications Technology, Japan to monitor sea surface current of the area where branch currents may exist. The frequency of the LROR is 9.2 MHz with sweep width of 22 kHz. Observational range of the Long Range Ocean Radar is approximately 200 km from Radar site, and its spatial and temporal resolutions are 7 km along the beam and 30 minutes, respectively. The LROR have been installed at northern tip of Tsushima Island and Aishima Island. Sea surface current measurement using LROR was conducted from 11 June to 8 September. We also conducted GPS buoy trajectory and mooring of current meters in the observed area of the LROR to validate accuracy of the LROR data. Correlation coefficients between radial velocities of Tsushima Radar and current velocities 10 m below the sea surface observed by ADCP were 0.34 - 0.59. The correlation coefficients were smaller than previous studies, and maximum correlation coefficients appeared at front side of the Radar. This fact implied that data processing, especially beam forming should be improved. In the presentation, we will discuss the accuracy of the LROR data and branches of the TWC for 3 months using reprocessed LROR data..
31. Kaoru Ichikawa, High Density Satellite Observation
, Future Prospects of Coastal Ocean Observations and Modeling in Japan, 2015.04.
32. Kaoru Ichikawa, Takuji Ebinuma, Hiroaki Akiyama, Yukihito Kitazawa, JAPAN's GNSS-R Research Team, Overview of GNSS-R Research Program for Ocean Observations at Japan, European Geophysical Union General Assembly 2015, 2015.04, [URL].
33. Wang Xi Feng, Kaoru Ichikawa, Wave frequency estimation under low-wind conditions
, Ocean Surface Topography Science Team Meeting, 2014 , 2014.10, Wave frequency has been empirically estimated from altimetry sigma_0 and SWH data by comparing with buoy wave observations. Under low-wind conditions, however, this relationship cannot be used since sigma_0, which is proportional to the inverse of the mean square slope (MSS), is more sensitive to waves with shorter wavelength (or higher frequency) that the large buoys cannot detect. In this study, the MSS for such high-frequency waves missed in buoy observations is estimated from the wind speed. The compensated MSS for the buoy observations by these estimations agrees well with the altimetry MSS. In turn, the estimated MSS for the high-frequency waves are removed from the altimetry MSS data to correctly estimate the wave frequency for longer-frequency waves such as swells..
34. Evaluation of land effects in coastal areas in satellite altimetry observations
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35. Hiroshi Ichikawa, Akira Nagano, Hiroyuki Tomita, Kaoru Ichikawa, Masanori Konda, Seasonality in the relations of volume transport proceeding to the Kuroshio Extension region with sea surface net heat flux, Asia Oceania Geosciencies Society Meeting, 2014, 2014.08, [URL].
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37. Presence Estimation of Giant Squids at a deep ocean off Ogasawara islands
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38. Satoshi Fujii, Kaoru Ichikawa, Oceanographic radar situations in Japan, Pacific Asia HF Radar System Network Workshop, 2014.04.
39. Kaoru Ichikawa, WC Yang, A. Morimoto, Yutaka Yoshikawa, S Sugitani, WS Chiang, JW Lai, EY Liang, CT Liu, CW Lee, S. Fujii, The Japan-Taiwan joint survey on combining ocean radar data in the Kuroshio upstream region
, 2nd Ocean Radar Conference for Asia-Pacific, 2014.04.
40. A. Morimoto, S Sugitani, T Takikawa, M. Kyushima, S. Fujii, Kaoru Ichikawa, Introduction of the Tsushima Warm Current observation using the Long Ranger Ocean Radar, 2nd Ocean Radar Conference for Asia-Pacific, 2014.04.
41. Kaoru Ichikawa, Kazushi Motomura, Akihiko Morimoto, Kenichi Fukudome, Yutaka Yoshikawa, Seasonal variations of the surface geostrophic Tsushima warm current determined by GPS on a ferryboat
, Ocean Science Meeting 2014, 2014.02, In the Tsushima/Korea Strait, the subsurface velocity has been monitored by the ADCP mounted on the ferryboat "New Camellia", but no measurements are available in the surface 18-m layer. The surface velocity is measured by the ocean radar system in the strait, but it includes ageostrophic wind-driven currents. The surface geostrophic velocity could be determined by spatial gradients of the sea surface dynamic height, but the satellite altimeters do not work properly in coastal areas. In this study, a new experiment to obtain the surface geostrophic velocity by the GPS system mounted on "New Camellia" is introduced. Winter (summer) decrease (increase) of the Tsushima warm current is well captured by the GPS-determined velocity as the other observations, but the variation ratio between the eastern and western Tsushima/Korea Strait Channels is found different from the ADCP velocity at the 18-m depth..
42. Takeshi Matsuno, C.T. Liu, Kenichi Fukudome, HW Chen, K. Ichikawa, Seasonal variations of volume transport through Taiwan and Tsushima Straits and net transport across the shelf break of the East China Sea
, Ocean Science Meeting 2014, 2014.02, Ocean structure and the transports of energy and various materials in the East Asian marginal seas are controlled by branch currents, roughly speaking, of the Kuroshio such as Taiwan and Tsushima Warm Currents. Particularly, in the East China Sea, the current passing through Taiwan Strait strongly affects the mass transport over the shelf region accompanied with the Kuroshio intrusion and Changjiang Diluted Water. We obtained time series of the volume transport through Taiwan Strait for longer than 4 years with ship mounted ADCP installed on a ferry boat across the strait. Comparing them with the variations through Tsushima Strait, we estimated the net transport across the shelf break. In summer, the net transport is reduced to mostly zero. The wind field provided by JRA25 suggests that the offshoreward Ekman transport across the shelf break is enhanced in the upper layer. Then, we deduced onshore transport of the Kuroshio subsurface water into the shelf region. This project was supported by MEXT/JST, ONR and Kyushu University..
43. Y. Miyazawa, SM Varlamov, X. Guo, K. Ichikawa, T. Miyama, M2 internal tide variability modulated by ocean circulation processes south of Japan, Ocean Science Meeting 2014, 2014.02, We conduct a concurrent simulation of the ocean circulation and explicit tide using a data assimilative ocean general circulation model covering the western North Pacific with horizontal resolution of 1/36 deg. to investigate possible interactions between them. Four sites of active M2 internal tide variability in open ocean (hot spots): Tokara Strait, Izu Ridge, Bashi Strait, and Ogasawara Ridge, are detected from both the satellite observation and simulation. Energy analysis of the simulated M2 internal tide indicates two types of the hot spots: dissipation (Tokara Strait and Izu Ridge) and radiation (Bashi Strait and Ogasawara Ridge) dominant sites, depending on difference in depths with active internal tide generation. Changes in density field due to mixed layer process, Kuroshio path variation, and mesoscale eddy activity considerably modulate energy conversion from external to internal M2 tides at the hot spots and radiation of M2 internal tide energy from them, suggesting a dynamical link from shallow to deep oceans through internal tide variablity..
44. Kaoru Ichikawa, Yutaka Yoshikawa, 福留 研一, Akihiko Morimoto, Jong-Hwan Yoon, Ageostrophic components in the coastal sea surface height obtained from the GPS on a ferryboat, Ocean Surface Topography Science Team Meeting, 2013.10.
45. Kaoru Ichikawa, Kenichi Fukudome, Akihiko Morimoto, Jong-Hwan Yoon, Coastal sea surface height variations as seen by GPS on a ferryboat, IAHS/IAPSO/IASPEI Joint Assembly, 2013.07, [URL], Satellite altimeters have provided valuable sea surface height (SSH) observations in open oceans, but their use is unfortunately limited in coastal regions by many technical reasons, including contaminations by lands reflections and larger complicated tides. Moreover, even if those problems were solved, the temporal sampling interval of the satellite altimeters is too coarse for smaller-scale coastal phenomena. Thus, in this study, complementary observations of the coastal SSH using Global Positioning System (GPS) are examined.
Since August 2010, the SSH across the Tsushima Strait between Japan and Korea has been observed every 30 seconds using a real-time kinematic (RTK) GPS receiver mounted on a ferryboat New Camellia that serves daily round trips across the strait. The observed SSH includes high-frequency fluctuations that would be caused by wind waves. They can be smoothed out by averaging the SSH over the ship route, although the averaging periods are required to be longer than approximately eight minutes since ordinary wind waves are aliased by the 30-second sampling intervals as long-period waves.
By removing tidal and geoid heights estimated by best-available local models, we determined the sea surface dynamic height (SSDH). The obtained SSDH regularly includes undulations with approximately 20km wavelength, which is equivalent to that of the internal semi-diurnal tides in this region. The larger-scale SSDH variations are well agreed with the dynamic heights calculated from the de-tided velocity observed at the 18m depth by the acoustic Doppler current profiler (ADCP) mounted on the same ferryboat. Those comparisons are further used for the improvement of the local tidal and geoid models.
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46. Akira Nagano, Kaoru Ichikawa, Hiroshi Ichikawa, Masanori Konda, K. Murakami, Volume transport toward the Kuroshio Extension region, a "hot spot" area in the North Pacific
, IAHS/IAPSO/IASPEI Joint Assembly, 2013.07, [URL], The western boundary current of the North Pacific subtropical gyre, the so-called Kuroshio, is considered to play a critical role in the global climate system due to the huge northward heat transport. In particular, the transport toward the active heat releasing Kuroshio Extension region, called ""hot spot"" area in the North Pacific, is important. However, significant disturbances in the entire North Pacific such as mesoscale eddy and recirculations have made the estimation of the transport difficult. Therefore, we carried out a one-year inverted echo sounder observation of the recirculation transport in the Shikoku Basin by the zonal observation line at 30°N to the Izu-Ogasawara Ridge that is a natural eastern boundary of the recirculation gyre, and extended the duration of the time series by satellite altimeter data. By removing the Shikoku Basin local recirculation transport, we estimated the volume transport in the top 1000-m layer toward the hot spot area. Most of the transport variations toward the hot spot area correspond to those of the Kuroshio transport on the continental slope south of Japan, which vary independently from those of the local recirculation gyre. Also, the volume transport toward the hot spot area was found to vary on shorter timescales than a decadal one, being affected from the transport variation of the western North Pacific regional recirculation gyre that would include the northeastward flow of the Ryukyu Current System in the Philippine Sea.
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47. Kaoru Ichikawa, Altimetry in Marginal Seas and Coastal Waters
, 2nd French-Japanese Workshop on the scientific utilization of sapce-based Earth Observation Data, 2013.05.
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54. Strait flow survey with efficient tide-removal strategy.
55. International cooperative study for monitoring of the Taiwan Warm Current and circulation on the shelf region in the East China Sea.
56. Improvement of velocity estimation methos for the long-range ocean radars.
57. Evaluation of altimetry-derived Taiwan Warm Currents.
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67. 九州大学.
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69. Satellite Observations: Taiwan Warm Current and Kuroshio Branch Current northeast of Taiwan as seen by along-track altimetry data, K. Ichikawa.
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73. Variations of the Kuroshio and mesoscale eddies observed by a HF radar system and satellite altimetry, Ryoko Tokeshi and Kaoru Ichikawa.
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76. Variations of the ocean bottom pressure induced by winds and atmospheric pressure changes, K. Ichikawa, Symposium "Impact from Other Disciplines on Seismology and Geodynamics".
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80. Estimation of surface wind-driven current in the HF radar observations in the Kuroshio upstream area, K. Ichikawa and R. Tokeshi, 2006 1st Air-Sea interaction workshop, [URL].
81. Time-series observations of deep/abyssal currents east of Wake Island (VII)
-- Mesoscale variations in a numerical model --, S. Terahara, K. Ichikawa, A. Ishida and H. Uchida, 2006 OSJ spring meeting.
82. Comparison of velocities in the upstream of the Kuroshio obtained by the HF radar and by the altimetry data, K. Ichikawa, R. Tokeshi, S. Fujii, K. Sato, S. Kojima, March 2006, [URL].
83. Velocity variations in the upstream of the Kuroshio (III) -- estimation of tidal and wind-driven currents --, R. Tokeshi, K. Ichikawa, S. Fujii, K. Sato, S. Kojima, 2006 OSJ spring meeting..
84. Evaluation of volume transport of bottom and abbysal currents through Wake island passage, H. Uchida, T. Fukasawa, I. Kaneko, T. Kono, S. Ayase, H. Yamamoto and K. Ichikawa, 9th Mirai Symposium, Feb, 2006.
85. Comparisons in the upstream of the Kuroshio between the HF radar surface velocity and the geostrophic velocity determined from the satellite altimetry, R. Tokeshi, K. Ichikawa, S. Fujii, K. Satoh and S. Kojima,
"Ocean HF radar meeing", Jan, 2006, [URL].
86. Meso-scale ocean bottom pressure variability around Japan as seen in the ECCO model, Kaoru Ichikawa and Ryo Otuka, Symposium on "Realization of Japanese satellite gravity mission", Dec. 2005..
87. Origin of the Ryukyu current system as seen from velocity structure east of Nansei Islands, Nagano, H. Ichikawa, T. Miura, X.-H. Zhu, K. Ichikawa, M. Konda, Y. Yoshikawa, K. Obama and K. Murakami, 2005 OSJ fall meeting..
88. Sea surface velocity variations as seen by satellite altimetry during the transition period of the Kuroshio large meander state, D. Ambe, S. Imawaki, K. Ichikawa and H. Uchida, 2005 OSJ fall meeting..
89. Velocity variations in the upstream of the Kuroshio (II) -- along-track comparison between satellite altimetry and HF radar normali vecocity components --, R. Tokeshi, K. Ichikawa, S. Fujii, K. Sato, S. Kojima, 2005 OSJ fall meeting..
90. Construction of temporally variable earth gravity model used in simulations of satellite gravity missions, T. Sugano, K. Yamamoto, Y. Fukuda, K. Ichikawa, N. Hirose, T. Nakaegawa, J. Okuno, B. Son, Y. Kuroishi, K. Matsumoto, 2004 Japan Earth Planetary Sicence Joint Meeting.
91. Time-series observations of deep/abyssal currents east of Wake Island (III)
-- Observations outlines and resluts of on-board observations --, H. Uchida, H. Yamamoto, T. Fukasawa, K. Ichikawa, I. Kaneko and T. Kouno, 2005 OSJ spring meeting.
92. Time-series observations of deep/abyssal currents east of Wake Island (IV)
-- Moored CTD observations and results --, H. Uchida, H. Yamamoto, T. Fukasawa, I. Kaneko, T. Kouno and K. Ichikawa, 2005 OSJ spring meeting.
93. Time-series observations of deep/abyssal currents east of Wake Island (VI)
-- Mesoscale variations --, S. Terahara, K. Ichikawa, H. Uchida, H. Yamamoto, T. Fukasawa, I. Kaneko and D. Ambe, 2005 OSJ spring meeting.
94. Response of coastal sea levels to interannual variations of the Kuroshio, Z. Zhang and K. Ichikawa, 2005 OSJ spring meeting.
95. Current variations in the Kuroshio upstream region: comparison between satellite altimetry and HF radar observations, R. Tokeshi, K. Ichikawa, S. Fujii, K. Satoh and S. Kodama, 2005 OSJ spring meeting.
96. Prompt report of moored CTD observations of the deep and bottom layers in the Wake Island passage, H. Uchida, H. Yamamoto, M. Fukasawa, I. Kaneko, T. Kouno, 8th Mirai Symposium.
97. Prompt report of moored current meter observations of the deep and bottom layers in the Wake Island passage, K. Ichikawa, H. Yamamoto, H. Uchida, M. Fukasawa, I. Kaneko, D. Ambe, S. Terahara, 8th Mirai Symposium.
98. Time-series observations of deep/abyssal currents east of Wake Island (V)
-- Moored current meter observations and temporal mean currents --, K. Ichikawa, H. Yamamoto, H. Uchida, T. Fukasawa, I. Kaneko, S. Terahara and D. Ambe, 2005 OSJ spring meeting.
99. Is satellite gravity mission necessary to observe deep-sea currents?, K. Ichikawa, H. Yamamoto, H. Uchida, M. Fukasawa, D. Ambe, Symposium for satellite gravity mission to observe "flow" of the earth.
100. Seasonal variations near the Kuroshio Extension as seen by satellite altimetry, K. Ichikawa and K. Ogawa, Symposium for surface flux near the Kuroshio Extension.
101. High-frequency responses of the barotropic ocean, S. Yoshida, N. Hirose, K. Ichikawa and S. Aoki, Symposium for satellite gravity mission to observe "flow" of the earth.
102. Time-series observations of deep/abyssal currents east of Wake Island (II)
--- in-situ caliblation of the mooring CTD's and error budgets of the volume and heat transport ---, H. Uchida, T. Yamamoto, T. Fukasawa, and K. Ichikawa,
2004 OSJ fall meeting.
103. Mesoscale eddy observed in a mid-depth layer southeast of Okinawa Island, T. Takikawa, H. Ichikawa, K. Ichikawa, M. Konda, X.-H. Zhu, T. Miura, K. Obama, and K. Takeuchi, 2004 OSJ fall meeting.
104. Seasonal variation of the surface velocity near Izu-Ogasawara ridge as seen by the satellite altimetry, K. Ogawa, K. Ichikawa, and S. Imawaki, 2004 OSJ fall meeting.
105. Tips to identify oceanic variations unobservable in the satellite gravity missions, K.Ichikawa, N.Hirose and S.Aoki, 2004 Japan Earth Planetary Sicence Joint Meeting.
106. Time series observation of abyssal and deep currents at the Wake passage (I), -Deployment of mooring systems and CTD observations-, H. Uchida, T. Fukasawa, K. Ichikawa, H. Yamamoto, T. Kouno, T. Yoshikawa, A. Sugimoto,
2004 OSJ spring meeting.
107. Variations of the Kuroshio volume transport around the Nansei Islands, T. Miura, T. Takikawa, X.-H. Zhu, K. Obama, H. Ichikawa, K. Ichikawa, M. Konda, K. Takeuchi and I. Kaneko, 2004 OSJ spring meeting.
108. Observations of the subtropical counter current by repeated ADCP and altimetry data, K. Ichikawa, N. Gohda, M. Arai, A. Kaneko, 2004 OSJ spring meeting.
109. Characteristics and evaluation of the Kuroshio axis distribution estimated from satellite altimetry data and drifter buoys, D. Ambe, S. Imawaki, K. Ichikawa and H. Uchida, 2004 OSJ spring meeting.
110. Changes of oceanic conditions in the Bungo Channel caused by variations of the Kuroshio, K. Miura, A. Kaneda and K. Ichikawa, 2004 OSJ spring meeting.
111. Response of a global barotropic ocean model to atmospheric disturbances, Y. Yoshida, N. Hirose, K. Ichikawa and S. Aoki, Symposium "Precise satellite positioning; A break-through of the dynamics of the Earth by satellite gravity missions".
112. Observations of the Ryukyu current system southeast of Nansei islands (II)
-- subsurface current core southeast of Amami-Ohshima Island --, T. Miura, X.-H. Zhu, K. Obama, H. Ichikawa, K. Ichikawa, M. Konda, K. Takeuchi, I. Kaneko, 2003 OSJ fall meeting.
113. 110-day variation of the Kuroshio path south of Shikoku, M. Kashima, S. Imawaki, S. Itoh, K. Ichikawa, S. Umatani, H. Uchida, S. Setoh, Y. Hashibe, H. Ichikawa and T. Fukasawa, 2003 OSJ fall meeting.
114. Variations of velocity profiles southeast of Amami-Ohshima Island
-- comparison between observed velocity and geostrophic velocity determined by PIES --, X.-H. Zhu, H. Ichikawa, T. Miura, K. Obama, K. Ichikawa, Y. Yoshikawa, H. Nakamura, A. Nishina, F. Kobayashi and I.-S. Han, 2003 OSJ fall meeting.
115. Coastal sea level variations south of Japan due to changes of the Kuroshio velocity, Zhang Z. and K. Ichikawa, OSJ 2003 fall meeting.
116. Sea surface height variations synchronized with sea level difference between Kushimoto and Uragami, Z. Zhang and K. Ichikawa, 2003 OSJ fall meeting.
117. Observations of the Ryukyu current system southeast of Nansei islands, T. Miura, X.-H. Zhu, I.-S. Han, K. Obama, H. Ichikawa, K. Ichikawa, M. Konda, K. Takeuchi, Y. Yoshikawa, J. Ishizaka, I. Kaneko, 2003 OSJ spring meeting.
118. Observations of the Kuroshio volume transport and the Kuroshio path south of Japan, S. Imawaki, K. Ichikawa, S. Umatani, H. Uchida, M. Kashima, D. Ambe, K. Kakinoki, H. Nakamura and A. Nishina, Symposium "Description and Prediction of the Kuroshio variations".
119. Mooring observations southeast of Okinawa Island (V)
-- Monitoring of the volume transport by satellite altimetry --,
X.-H. Zhu, H. Ichikawa, K. Ichikawa, I.-S. Han, J.-H. Park, A. Kaneko, N. Gohda, S. Umatani, 2003 OSJ spring meeting.
120. Variations of surface velocity in the western subtropical gyre, N. Gohda, M. Arai, A. Kaneko and K. Ichikawa, Symposium "Description and Prediction of the Kuroshio variations".
121. Northward current southeast of Nansei islands, T. Miura, H. Ichikawa, I.-S. Han, X.-H. Zhu, K. Ichikawa and Y. Yoshikawa, 6th "Blue Earth" Symposium.
122. Relation between coastal area and the Kuroshio as seen by satellite altimetry, Z. Zhang and K. Ichikawa, Symposium "Effects of offshore variations in coastal areas".
123. Effect of a stable large meander on interactions between the Kuroshio and mesoscale eddies, Z. Zhang and K. Ichikawa, 2002 OSJ fall meeting.
124. Measureing from the space -- ocean observation by remote sensing methods, K. Ichikawa, 2002 Kyushu University Open Campus Seminar "Predictability of environmental change; simulations of ocean and atmosphere in Kyushu".
125. Mooring observations southeast of Okinawa Island (IV)
-- changes of sea level and current structure around Okinawa due to mesoscale eddies, I.-S. Han, X.-H. Zhu, H. Ichikawa, K. Ichikawa, M. Konda, A. Kaneko,
J.-H. Park, T. Miura, K. Obama and K. Takeuchi, 2002 OSJ fall meeting.
126. Estimation of mean sea surface height field in the North Pacific using satellite altimetry data and drifter buoys data, D. Ambe, S. Imawaki, H. Uchida and K. Ichikawa, 2002 OSJ fall meeting.
127. Amplitude modulation of variations southwest of Kyushu with periods of several months, Y. Sumikawa and K. Ichikawa, 2002 OSJ spring meeting.
128. Mooring observations southeast of Okinawa Island (I)
-- current structure of mesoscale eddies obtained from the mooring data --,
I.-S. Han, X.-H. Zhu, J.-H. Park, H. Ichikawa, A. Kaneko, K. Ichikawa, M. Konda, A. Ostrovskii, N. Gohda and S. Umatani, 2002 OSJ spring meeting.
129. Mooring observations southeast of Okinawa Island (II)
-- results from PIES data --, X.-H. Zhu, J.-H. Park, I.-S. Han, H. Ichikawa, A. Kaneko, K. Ichikawa, M. Konda, A. Ostrovskii, N. Gohda and S. Umatani, 2002 OSJ spring meeting.
130. Changes of coastal water temperature due to meandering of the Kuroshio path, K. Ichikawa and A. Kaneda, 2002 Interdisciplinary Graduate School of Engineering Sciences Seminar.
131. The Kuroshio as seen by bumps in the ocean measured from the space, K. Ichikawa, 16th "University and Science" Symposium.
132. Seasonal change of sea level in the eastern antarctic coastal region and its effect on the grand level change, S. Aoki, K. Ichikawa, T. Ozawa, K. Doi, K. Shibuya, 21th Antarctic Geology Symposium.
133. Spatial representability of coastal sea level changes, K. Ichikawa, 2001 OSJ fall meeting.
134. Kuroshio path variations southwest of Kyushu, using satellite altimetry data and mooring current meter records, Y. Sumikawa, K. Ichikawa, H. Nakamura, H. Ichikawa and A. Nishina, 2001 OSJ fall meeting.
135. Relationship between volume transport of the Kuroshio and coastal sea level changes along southern coast of the western Japan, N. Kunitomi, A. Kaneda, K. Ichikawa, H. Takeoka and N. Koizumi, 2001 OSJ fall meeting.
136. Gravity field and oceanography, K. Ichikawa, Symposium "Scope of the oceanography in 21th century".
137. Comparison of the trajectories of surface drifter buoys with the sea surface height in the Kuroshio recirculation region, J.-H. Park, A. Ostrovskii, K. Ichikawa, H. Noritaka, X.-H. Zhu, I.-S. Han, A. Kaneko, H. Ichikawa, K. Takeuchi.
138. Seasonal changes of grand level and sea level in the eastern antarctic coastal region, S. Aoki, K. Ichikawa, T. Ozawa, Symposium "New age for satellite gravity observations and satellite altimetry".
139. Oceanography and the GRACE mission, K. Ichikawa, Symposium "New age for satellite gravity observations and satellite altimetry".
140. Usability of the satellite altimetry data at high latitude region investigated with SAR data, T. Yamanokuchi, S. Aoki and K. Ichikawa.
141. Spatial representability of the Kuroshio variations in the Tokara Strait, K. Ichikawa, 2001 OSJ spring meeting.
142. Sea surface variations as seen by satellite altimetry data, K. Ichikawa, memorial seminar for 2001 Okada prize.
143. Marine geoid and altimetry, K. Ichikawa, Symposium "Satellite altimetry and satellite gravity missions in new age".
144. Japan Ocean Flux data sets with use of Remote Sensing Observations, M. Kubota, M. Kutuwada, S. Kizu, N. Iwasaka, M. Konda and K. Ichikawa.
145. Comparison among drifter buoy, ADCP observations and geostrophic velocity obtained from the altimetry data, K. Ichikawa and S. Imawaki, Symposium "Intercomparison of surface flux data sets".
146. Temporal and spatial smoothing of ocean satellite data, and their effects to obtained physical parameters -- A case for satellite altimetry, K. Ichikawa, Joint Meeting of Earth and Planetary Science 2000.
147. Surface velocity variations in the western North Pacific, N. Gohda, M. Arai, H. Zheng and K. Ichikawa, Symposium "Toward predictions of the Kuroshio variations".
148. 1-month prediction of the Kuroshio path variation, T. Awaji, M. Komori, T. Kuragano, K. Ichikawa and H. Nakamura, Symposium "Toward predictions of the the Kuroshio variations".
149. Symposium "Satellite altimetry in the 21th century".
150. Interannual variability of sea surface temperature in the eastern North Pacific, K. Suito, K. Ichikawa and S. Imawaki, 1999 OSJ fall meeting.
151. Temperature change in the Bungo Channel related with offshore mesoscale eddies, K. Ichikawa, 1999 OSJ fall meeting.
152. Estimation of advection heat flux at the sea surface, K. Ichikawa and S. Imawaki, 1999 OSJ spring meeting.
153. Asimilation of satellite altimetry data into a 1.5-layer model of the North Pacific, R. Sasaki, M. Kubota, K. Ichikawa and T. Kuragano, Symposimum "Studies on ocean and solid earth using satellite altimetry".
154. Steric height changes due to horizontal heat transport, K. Ichikawa, Symposium "Studies on ocean and solid earth using satellite altimetry".
155. Steric Height Change estimated from seasonal variation of sea surface height, K. Ichikawa, 1998 OSJ fall meeting.
156. Variations of the Kuroshio in the Tokara Strait caused by mesoscale eddies, K. Ichikawa, 1998 OSJ spring meeting.