Language：English  

Together with direct Global Navigation Satellite System (GNSS) signals, the signals reflected at the water surface can be received by an unmanned aerial vehicle (UAV). From the range difference between two GNSS signal paths, the height of the UAV above the water level can be geometrically estimated using the weighted least squares method, called GNSS reflectometry (GNSS-R) altimetry. Experimental low-cost GNSS-R altimetry flights with a UAV were conducted at the coast of Lake Biwa, Japan. Although the height estimated by the GNSS-R altimeter included large short-term noises up to 8 m amplitude, it agreed well with the UAV altitude measured by the post-processed kinematic positioning. By selecting better weight functions in the least square method and using sufficient temporal averaging, the GNSS-R altimetry achieved accuracy in the order of 0.01 m if a sufficient number of GNSS satellites with high elevation angles were available. The dependency of the results on the weight functions is also discussed.

DOI： 10.3390/s19050998

Repository Public URL： http://hdl.handle.net/2324/2231023

Language：Others  

Complementary Remote Sensing Observations of the Tsushima Warm Current Patterns

DOI： 10.1007/978-3-319-94067-0_10

Other Link： https://www.springer.com/jp/book/9783319940656

Repository Public URL： http://hdl.handle.net/2324/2231038

Language：Others  

Remote Sensing of the Kuroshio Current System

DOI： 10.1007/978-3-319-94067-0_11

Other Link： https://www.springer.com/jp/book/9783319940656

Repository Public URL： http://hdl.handle.net/2324/2231030

Language：English   Publishing type：Research paper (scientific journal)  

Although the Brown mathematical model is the standard model for waveform retracking over open oceans, due to heterogeneous surface reflections within altimeter footprints, coastal waveforms usually deviate from open ocean waveform shapes and thus cannot be directly interpreted by the Brown model. Generally, the two primary sources of heterogeneous surface reflections are land surfaces and bright targets such as calm surface water. The former reduces echo power, while the latter often produces particularly strong echoes. In previous studies, sub-waveform retrackers, which use waveform samples collected from around leading edges in order to avoid trailing edge noise, have been recommended for coastal waveform retracking. In the present study, the peaky-type noise caused by fixed-point bright targets is explicitly detected and masked using the parabolic signature in the sequential along-track waveforms (or, azimuth-range echograms). Moreover, the power deficit of waveform trailing edges caused by weak land reflections is compensated for by estimating the ratio of sea surface area within each annular footprint in order to produce pseudo- homogeneous reflected waveforms suitable for the Brown model. Using this method, altimeter waveforms measured over the Tsushima Islands in Japan by the Ocean Surface Topography Mission (OSTM)/Jason-2 satellite are retracked. Our results show that both the correlation coefficient and root mean square difference between the derived sea surface height anomalies and tide gauge records retain similar values at the open ocean (0.9 and 20 cm) level, even in areas approaching 3 km from coastlines, which is considerably improved from the 10 km correlation coefficient limit of the conventional MLE4 retracker and the 7 km sub-waveform ALES retracker limit. These values, however, depend on the topography of the study areas because the approach distance limit increases (decreases) in areas with complicated (straight) coastlines.

DOI： 10.3390/rs9070762

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2009JC005747

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：Others  

Language：Japanese  

Authorship：Lead author,　Corresponding author   Language：Japanese  

DOI： https://doi.org/10.32211/lamer.62.1-2_13

Repository Public URL： https://hdl.handle.net/2324/7339189

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.32211/lamer.61.3-4_345

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English  

DOI： 10.1016/j.celrep.2023.112884

Web of Science

PubMed

DOI： 10.1109/MEMS49605.2023.10052502

Web of Science

Language：English  

DOI： 10.3164/jcbn.20-172

Web of Science

PubMed

DOI： 10.1109/CBS55922.2023.10115380

Web of Science

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2020JC017141

Language：Japanese  

「ちきゅう」&DONETのトータル観測ステーション計画(経過報告)

Language：English   Publishing type：Research paper (other academic)  

DONET (Dense Oceanfloor Network system for Earthquakes and Tsunamis) has been developed and installed around Nankai Trough, which is motivated by the 2004 Sumatra-Andaman Earthquake. DONET contains pressure gauges as well as seismometers, which is expected to detect crustal deformations driven by peeling off subduction plate coupling process. From our simulation results, leveling changes are different sense among at the DONET points even in the same science node. On the other hand, oceanic fluctuations such as melting ice masses through the global warming has so large scale as to cause ocean bottom pressure change coherently for all of DONET points especially in the same node. This difference suggests the possibility of extracting crustal deformations component from ocean bottom pressure data by differential of stacking data. However, this operation cannot be applied to local-scale fluctuations related to ocean mesoscale eddies and current fluctuations, which affect ocean bottom pressure through water density changes in the water column (from the sea surface to the bottom). Recently, Kuroshio current path has been changed drastically, which significantly affect ocean bottom pressures at DONET station points. Therefore, we need integral analysis by combining seismology, ocean physics and tsunami engineering so as to decompose into crustal deformation, oceanic fluctuations and instrumental drift, which will bring about high precision data enough to find geophysical phenomena. Since DONET has been and will be connected to long-term borehole observatories constructed in the Nankai Trough under the Integrated Ocean Drilling Program (IODP) by using the deep-sea drilling vessel Chikyu, we have to discuss the best way to do simultaneous observation from seafloor to atmosphere by taking advantage of this chance.

DOI： 10.1109/OCEANSKOBE.2018.8559382

Language：Others   Publishing type：Research paper (other academic)  

A Total Station Plan Combined with “D/V Chikyu” and DONET:Simultaneous Observation from Seafloor to Atmosphere

DOI： 10.1109/oceanskobe.2018.8559382

Language：English  

DOI： 10.1002/essoar.9ba3ca568e624190.f2914573e2c248dd.1

Language：Japanese  

Language：Japanese  

Language：Japanese  

同期掃引によるバイスタティクレーダ受信方式

Language：Japanese  

Satellite Observations : Taiwan Warm Current and Kuroshio Branch Current northeast of Taiwan as seen by along-track altimetry data

Language：English   Publishing type：Research paper (scientific journal)  

Wave periods estimated from satellite altimetry data behave differently from those calculated from buoy data, especially in low-wind conditions. In this paper, the geometric mean wave period is calculated from buoy data, rather than the commonly used zero-crossing wave period. The geometric mean wave period uses the fourth moment of the wave frequency spectrum and is related to the mean-square slope of the sea surface measured using altimeters. The values of obtained from buoys and altimeters agree well (root mean square difference: 0.2 s) only when the contribution of high-frequency sea waves is estimated by a wavenumber spectral model to complement the buoy data, because a buoy cannot obtain data from waves having wavelengths that are shorter than the characteristic dimension of the buoy.

DOI： 10.3390/rs8090764

Other Link： http://www.mdpi.com/2072-4292/8/9/764

Repository Public URL： http://hdl.handle.net/2324/2231046

Language：Japanese  

Repository Public URL： http://hdl.handle.net/2324/2348784

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The water characteristics of the East China Sea depend on influxes from river run-off, the Kuroshio, and the Taiwan Strait. A three-year observation using an acoustic Doppler current profiler (ADCP) operated on a ferry provides the first nearly continuous data set concerning the seasonal flow pattern and the volume transport from the Taiwan Strait to the East China Sea. The observed volume transport shows strong seasonality and linkage to the along-strait wind stress. An empirical regression formula between the volume transport and wind was derived to fill the gaps of observation so as to obtain a continuous data set. Based on this unique data set, the three-year mean of monthly volume transport is north-eastward throughout the year, large (nearly 3 Sv) in summer and low (nearly zero) in winter. The China Coastal Current flows southward in winter, while the northward-flowing Taiwan Strait Current may reverse direction during severe northeasterly winds in the winter or under typhoons. The sea level difference across Taiwan Strait is closely correlated to the transport through the strait, and their relation is found seasonally nearly stable. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.csr.2015.12.010

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

We analyze a concurrent simulation result of the ocean circulation and tidal currents using a data-assimilative ocean general circulation model covering the Western North Pacific with horizontal resolution of 1/36 degrees to investigate possible interactions between them. Four sites of active M-2 internal tide variability in open ocean (hot spots), such as Tokara Strait, Izu Ridge, Luzon Strait, and Ogasawara Ridge, are detected from both the satellite observation and the simulation. Energy cycle analysis of the simulated M-2 baroclinic tide indicates two types of the hot spots: dissipation (Tokara Strait and Izu Ridge) and radiation (Luzon Strait and Ogasawara Ridge) dominant sites. Energy conversion from barotropic to baroclinic M-2 tides at the hot spots is modulated considerably by the lower-frequency changes in the density field. Modulation at the two spots (Tokara Strait and Izu Ridge) is affected by the Kuroshio path variation together with the seasonal variation of the shallow thermocline. At the other two sites, influence from changes in the relatively deep stratification through the Kuroshio intrusion into South China Sea (Luzon Strat) and mesoscale eddy activity (Ogasawara Ridge) is dominant in the modulation.

DOI： 10.1002/2015JC010739

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

The seasonal sea surface height variation in the Tsushima Strait in 2011 winter was reported to be properly observed by the GPS on the ferryboat “New Camellia”, but larger variations in the eastern channel were found, which are inconsistent with the other observations. By replacing the 4-constituent tidal model to the 8-constituent one, this inconsistency was modified. Spatial variations of the relatively minor P1 and K2 constituents, which are aliased as long-term variations by the daily sampling, result in the pseudo signal in the eastern channel.

Language：Japanese  

Satellite altimeters in the early 21st Century

Language：Japanese  

Decadal Vision in Oceanography (I)-Discussions in the physical oceanography subgroup of the future planning committee, The Oceanographic Society of Japan-

Language：Japanese  

Decadal Vision in Oceanography (I) : Discussions in the physical oceanography subgroup of the future planning committee, The Oceanographic Society of Japan(Decadal Vision in Oceanography-Special issue of "Oceanography in Japan"-)

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Temporal variations of the sea surface dynamic height (SSDH) in 2011 winter are determined from tide gauge records at Pusan and Hakata by applying a tide-killer filter. The SSDH in the Tsushima Strait are also obtained by the GPS receiver mounted on the ferry “New Camellia” that crosses the Tsushima Strait almost every day. Generally, the tidal SSDH decreases in winter due to the cooling steric heights, but the SSDH at Pusan tends to increase in time with respect to that at Hakata, suggesting decrease of the eastward speed of the Tsushima current. This temporal tendency is also recognized in the GPS-determined SSDH; the long-term SSDH variations within the Tsushima Strait suggest that the eastward Tsushima current decreases both in the Eastern and Western Channel and that this tendency is clearer in the Eastern Channel.

Language：English   Publishing type：Research paper (scientific journal)  

The volume transport of the Kuroshio, the western boundary current of the North Pacific subtropical gyre, varies vigorously due to merging of disturbances propagating from the entire North Pacific. Taking into account the recirculation in the Shikoku Basin by the zonal observation line at 30A degrees N to the west of the Izu-Ogasawara Ridge, we estimated the volume transport in the top 1,000 m layer toward the Kuroshio Extension region. The volume transport of the local recirculation gyre in the Shikoku Basin increases associated with the westward extension of the gyre, particularly in the period of the large meandering path of the Kuroshio south of Japan. Meanwhile, most of the transport variations toward the Kuroshio Extension region correspond to those of the Kuroshio transport on the continental slope south of Japan, which vary independently of those of the recirculation gyre.

DOI： 10.1007/s10872-013-0173-9

Other Link： http://link.springer.com/article/10.1007/s10872-013-0173-9

Language：Japanese  

対馬海峡における長期流況モニタリング

Language：English   Publishing type：Research paper (scientific journal)  

With full-depth LADCP velocity data collected in a wide area southeast of Kyushu, Japan, large velocity currents, occasionally exceeding 15 cm s-1, were observed in a thick, 500.1,500 m, near-homogeneous density layer below approximately 3,000 m depth around the steep topographies. The currents were found not to flow along the topographic contours, and to be strongly ageostrophic.
The directions of the bottom-layer currents are rather related with phase of the semi-diurnal tides, suggesting deeply intruded internal tides generated at the steep topographies.

DOI： doi:10.1007/s10872-013-0170-z

Language：English   Publishing type：Research paper (scientific journal)  

With full-depth LADCP velocity data collected in a wide area southeast of Kyushu, Japan, large velocity currents, occasionally exceeding 15 cm s(-1), were observed in a thick, 500-1,500 m, near-homogeneous density layer below approximately 3,000 m depth around the steep topographies. The currents were found not to flow along the topographic contours, and to be strongly ageostrophic. The directions of the bottom-layer currents are rather related with phase of the semi-diurnal tides, suggesting deeply intruded internal tides generated at the steep topographies.

DOI： 10.1007/s10872-013-0170-z

Language：English   Publishing type：Research paper (scientific journal)  

Japanese and Taiwanese institutes have collaborated to obtain ocean radar data with significantly increased coverage in the upstream Kuroshio region. An international joint survey was conducted in June 2012, in which intensive in situ observations were performed within the radar coverage. Details of the joint survey are presented in this paper with brief descriptions of preliminary results on the surface and subsurface currents near and within the Kuroshio.

DOI： 10.1007/s12601-013-0011-4

Other Link： http://link.springer.com/article/10.1007%2Fs12601-013-0011-4

Language：English   Publishing type：Research paper (scientific journal)  

Subsurface current structures east of Amami-Oshima Island based on LADCP observation

Language：English  

DOI： 10.5270/esa.sp-710.altimetry2012

Language：English  

DOI： 10.5270/esa.sp-710.altimetry2012

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Repository Public URL： http://hdl.handle.net/2324/27147

Language：English  

Ageostrophic velocity component is estimated by subtracting the geostrophic velocity determined from the along-track Jason-1/2 data from the surface velocity observed by long-range ocean radars in the upstream region of the Kuroshio operated by NICT, Japan. Assuming that the ageostrophic component is dominated by the wind-driven surface flow, the speed factor, or the ratio of the speed of the wind-driven flow to the wind speed, and the deflection angle with respect to the wind direction are estimated by the least square method and the QuikSCAT data. Both the speed factor and the deflection angle change seasonally; the former ranges from approximately 1 to 1.5% and tends to be largest in winter, although the changes would be less significant with respect to the accuracy of the velocity data. Meanwhile, the latter varies from 20 to 80 degree clockwise from the wind direction and becomes largest in summer. This tendency is obvious in the offshore region, but insignificant within the Kuroshio. The results would be discussed with possible seasonal variations of the eddy viscosity due to the vertical stratification and wind drag coefficient.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

We conducted synoptic hydrographic surveys three times under distinctly different conditions of the Kuroshio in the region off the southern coast of Japan; the large-meander (October 2004) and non-large-meander (September 2005 and September 2006) states. As a result of the water mass analysis, we could separate the volume and heat transports of the North Pacific subtropical gyre from the local recirculation gyre and mesoscale eddies. Despite the different flow conditions of the Kuroshio, the volume transport and the volume transport-averaged temperature of the subtropical gyre fluctuate within the ranges of 23.3-29.0 x 10(6) m(3) s(-1) and 17.3-17.6 degrees C, respectively, which are quite stable with respect to those for the Kuroshio south of Japan estimated in the past studies. Taking into account the decrease in the volume transport-averaged temperature in the North Pacific interior region, the net heat transport of the subtropical gyre across the latitude of 30 degrees N was estimated to be between 0.19 and 0.22 x 10(15) W.

DOI： 10.1029/2009JC005747

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English  

Language：English  

Language：Others  

Synoptic flow structures in the confluence region of the Kuroshio and the Ryukyu Current

DOI： 10.1029/2008JC005213

Language：English   Publishing type：Research paper (scientific journal)  

In the southeastern region of Kyushu, Japan, the Kuroshio from the East China Sea encounters the Ryukyu Current from the east of the Ryukyu Islands. By analyzing synoptic sections of water properties and geostrophic velocity in August 2004 and October 2005, we distinguished the waters in the Kuroshio southeast of Kyushu to be separated into an offshore region and a shallow onshore one. The onshore water is derived from the East China Sea, while the offshore water originates from both the east of Amami-Oshima Island and the interior region of the North Pacific. The water mass transport from the east of Amami-Oshima Island may become equivalent to that of the Kuroshio in the East China Sea as in October 2005. The volume transport-averaged temperature of the Kuroshio southeast of Kyushu is significantly lower than that in the East China Sea because of the confluence with the colder Ryukyu Current east of the Amami-Oshima Island.

DOI： 10.1029/2008JC005213

Language：English   Publishing type：Research paper (scientific journal)  

In the southeastern region of Kyushu, Japan, the Kuroshio from the East China Sea encounters the Ryukyu Current from the east of the Ryukyu Islands. By analyzing . synoptic sections of water properties and geostrophic velocity in August 2004 and October 2005, we distinguished the waters in the Kuroshio southeast of Kyushu to be. separated into an offshore region and a shallow onshore one. The onshore water is derived from the East China Sea, while the offshore water originates from both the east of Amami-Oshima Island and the interior region of the North Pacific. The water mass transport from the east of Amami-Oshima Island may become equivalent to that of the Kuroshio in the East China Sea as in October 2005. The volume transport-averaged temperature of the Kuroshio southeast of Kyushu is significantly lower than that in the East China Sea because of the confluence with the colder Ryukyu Current east of the Amami-Oshima Island. Copyright 2009 by the American Geophysical Union.

DOI： 10.1029/2008JC005213

Language：English   Publishing type：Research paper (scientific journal)  

A quasiperiodic variation of 100-110 days in the Kuroshio path off Cape Ashizuri, resulting from the passage of small meanders, was detected by observation with moored current meters during 1993-1995. TOPEX/POSEIDON altimeter data covering 9 years showed that the quasiperiodic variation period was not persistent and modulated twice, with a 110-day period from mid-1993 to late 1996, a 150-day period from late 1996 to mid-1999, and a 110-day period from mid-1999 to late 2001. The quasiperiodic variations of the Kuroshio path migration were contemporaneous with the quasiperiodic arrivals of mesoscale eddies from the east along 27-32A degrees N over the same 110- and 150-day period quasiperiodic variations. The periodic arrivals of the eddies configure the periodic variations of the Kuroshio path and its inter-annual modulation.

DOI： 10.1007/s10872-009-0007-y

Language：English   Publishing type：Research paper (scientific journal)  

A quasiperiodic variation of 100-110 days in the Kuroshio path off Cape Ashizuri, resulting from the passage of small meanders, was detected by observation with moored current meters during 1993-1995. TOPEX/POSEIDON altimeter data covering 9 years showed that the quasiperiodic variation period was not persistent and modulated twice, with a ∼110-day period from mid-1993 to late 1996, a ∼150-day period from late 1996 to mid-1999, and a ∼110-day period from mid-1999 to late 2001. The quasiperiodic variations of the Kuroshio path migration were contemporaneous with the quasiperiodic arrivals of mesoscale eddies from the east along 27-32°N over the same ∼110- and ∼150-day period quasiperiodic variations. The periodic arrivals of the eddies configure the periodic variations of the Kuroshio path and its inter-annual modulation.

DOI： 10.1007/s10872-009-0007-y

Language：English   Publishing type：Research paper (scientific journal)  

Variations of the position and speed of the Kuroshio are studied by a combination of high-resolution high-frequency (HF) ocean radar data and wide-coverage altimetry data. The speed of the Kuroshio and its position are determined along 123.35° E northeast of Taiwan from daily maps of surface geostrophic velocity estimated from HF radar data from August 2001 to February 2005. These two are found to be well correlated for mesoscale variations with periods of a few months, as the Kuroshio tends to be faster (or slower) when its axis moves south (or north). This tendency is significant in summer when the Kuroshio is seasonally intensified and well-defined in the HF radar data. By taking correlation with the sea surface dynamic height anomaly observed by satellite altimeters, these Kuroshio variations in the East China Sea are found to be induced by merging of mesoscale eddies from the east at 21° N and by coincident Kuroshio meanders east of Taiwan.

DOI： 10.1080/01431160802175454

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Variations of velocity and transport associated with coastal cyclonic eddies off Shikoku, Japan estimated from moored current meter and IES data,
Koji KAKINOKI, Shiro IMAWAKI, Kaoru ICHIKAWA, Shin-ichiro UMATANI and Motohiko KASHIMA,
RIAM Reports, 135, 53-59

Language：English   Publishing type：Research paper (other academic)  

Beneath the Kuroshio south of Shikoku, there exist bottom currents, flowing in the different direction from the Kuroshio. In order to examine their horizontal and vertical characteristics, we analyzed four current data sets obtained by lowered acoustic Doppler current profilers (LADCP) in the region south of Shikoku during 2004-2006. While the surface Kuroshio in the top 700-m layer flows eastward, the bottom currents flow toward the left-hand side of the surface Kuroshio, i.e., to the inshore side. This vertical current structure is found to be maintained even when the Kuroshio moves offshore to the deep-ocean due to the propagation of the small meander of the Kuroshio.

DOI： 10.1109/OCEANSKOBE.2008.4530977

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Experimental Estimate of Geostrophic Current from Trajectory Data of Sea-Surface Drifting Buoys
Daisuke AMBE and Kaoru ICHIKAWA,
RIAM Reports, 135, 83-88.

Repository Public URL： http://hdl.handle.net/2324/14188

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Tidal Currents North of the Yaeyama Islands as seen by HF radars
Kaoru ICHIKAWA, Ryoko TOKESHI and Shoichiro KOJIMA
RIAM Reports, 135, 77-81

Repository Public URL： http://hdl.handle.net/2324/14187

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Interannual variability of mesoscale eddy activity at the subtropical fronts region and its influence on the generation of Kuroshio large meander,
Motohiko KASHIMA, Kaoru ICHIKAWA and Makoto SATAKE,
RIAM Reports, 135, 61-67

Language：English   Publishing type：Research paper (scientific journal)  

Two inverted echo sounders were maintained on coastal and offshore sides of the Kuroshio south of Japan from October 1993 to July 2004. Applying the gravest empirical mode method, we obtained a time series of geostrophic transport. Estimated transports generally agree well with geostrophic transports estimated from hydrography. Their agreement with the hydrographic transports is better than that of transports estimated from satellite altimetry data. The geostrophic transport is expressed as the surface transport per unit depth multiplied by the equivalent depth. The geostrophic transport varies mostly with the surface transport and fractionally with the equivalent depth. Seasonal variation of the geostrophic transport has a minimum in March and a maximum in September, with a range of about one fifth of the total transport.

DOI： 10.1007/s10872-008-0030-4

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (other academic)  

Beneath the Kuroshio south of Shikoku, there exist bottom currents, flowing in the different direction from the Kuroshio. In order to examine their horizontal and vertical characteristics, we analyzed four current data sets obtained by lowered acoustic Doppler current profilers (LADCP) in the region south of Shikoku during 2004-2006. While the surface Kuroshio in the top 700-m layer flows eastward, the bottom currents flow toward the left-hand side of the surface Kuroshio, Le, to the inshore side. This vertical current structure is found to be maintained even when the Kuroshio moves offshore to the deep-ocean due to the propagation of the small meander of the Kuroshio.

DOI： 10.1109/OCEANSKOBE.2008.4530977

Language：Japanese   Publishing type：Research paper (scientific journal)  

Taiwan Warm Current and Kuroshio Branch Current northeast of Taiwan as seen by along-　track altimetry data,
Kaoru Ichikawa and Daisuke Ambe

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2007JC004561

Language：English  

Reply to comment by Xie-Hua Zhu et al. on "Current system east of the Ryukyu Islands''

DOI： 10.1029/2007JC004561

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Repository Public URL： http://hdl.handle.net/2324/26847

Language：English   Publishing type：Research paper (scientific journal)  

A method to extract geostrophic current in the daily mean HF radar data in the Kuroshio upstream region is established by comparison with geostrophic velocity determined from the along-track altimetry data. The estimated Ekman current in the HF velocity is 1.2% (1.5%) and 48 degrees (38 degrees)-clockwise rotated with respect to the daily mean wind in (outside) the Kuroshio. Furthermore, additional temporal smoothing is found necessary to remove residual ageostrophic currents such as the inertial oscillation. After removal of the ageostrophic components, the HF geostrophic velocity agrees well with that from the altimetry data with rms difference 0.14 (0.12) m/s in (outside) the Kuroshio.

DOI： 10.1007/s10872-007-0062-1

Language：Others   Publishing type：Research paper (scientific journal)  

2007 June

DOI： 10.1029/2006jc003917

Language：English   Publishing type：Research paper (scientific journal)  

The Ryukyu Current System (RCS) is a northeastward current southeast of the Ryukyu Islands. The variation of current structure in the RCS region was investigated on the basis of the absolute geostrophic velocity estimated by inverse calculation using hydrographic data. Three realizations of the RCS are examined from cruises in May, September, and October 2002. It was found that the current structure in the RCS region is divided into upper and lower layers by an isopycnal surface of 26 σθ. The currents in both layers proceed northeastward along the eastern slope, east of the Ryukyu Islands. The current in the upper layer merges with the inflow from the interior region, resulting in larger northeastward volume transport southeast of Amami-Oshima Island than southeast of Okinawa Island. The volume transport from the east reaches more than 40% of that southeast of Amami-Oshima Island. On the other hand, the current in the lower layer is not affected by inflow from the east. It is also found that the upper RCS gains heat mainly through the advection of warm water from the east, resulting in an increase in the downstream temperature by about 0.5°C on average. Copyright 2007 by the American Geophysical Union.

DOI： 10.1029/2006JC003917

Language：English   Publishing type：Research paper (scientific journal)  

[1] The Ryukyu Current System (RCS) is a northeastward current southeast of the Ryukyu Islands. The variation of current structure in the RCS region was investigated on the basis of the absolute geostrophic velocity estimated by inverse calculation using hydrographic data. Three realizations of the RCS are examined from cruises in May, September, and October 2002. It was found that the current structure in the RCS region is divided into upper and lower layers by an isopycnal surface of 26 sigma(theta). The currents in both layers proceed northeastward along the eastern slope, east of the Ryukyu Islands. The current in the upper layer merges with the inflow from the interior region, resulting in larger northeastward volume transport southeast of Amami-Oshima Island than southeast of Okinawa Island. The volume transport from the east reaches more than 40% of that southeast of Amami-Oshima Island. On the other hand, the current in the lower layer is not affected by inflow from the east. It is also found that the upper RCS gains heat mainly through the advection of warm water from the east, resulting in an increase in the downstream temperature by about 0.5 degrees C on average.

DOI： 10.1029/2006JC003917

Language：English   Publishing type：Research paper (scientific journal)  

[1] Water mass characteristics and volume transports of abyssal water flowing northward into Wake Island Passage in the North Pacific Ocean were examined by carrying out high-quality hydrographic surveys in May 2003, October 2004, and December 2005 along with mooring observations from May 2003 to December 2005. Close linear relationships between potential temperature (theta) and salinity, dissolved oxygen, and silicate were seen below theta approximate to 1.1 degrees C (approximate to 4000 m). The relationships above theta approximate to 1.1 degrees C were scattered and were separated into relatively salty, oxygen-rich, silicate-poor water to the south, and water with the opposite properties to the north. The results suggested that there was a boundary between water masses at theta approximate to 1.1 degrees C in the deep passage. In addition to the three hydrographic sections, two hydrographic sections previously surveyed in the deep passage in 1975 and 1999 were reexamined for transport estimates. Geostrophic calculations relative to the theta = 1.1 degrees C surface indicated northward transports of the abyssal water from 0.5 to 2.2 Sv (1 Sv = 10(6) m(3) s(-1)) below this surface. When 1-year mean estimated velocities at theta = 1.1 degrees C surface were used for reference, mean transport from the five estimates increased from 1.4 to about 4 Sv. The temperature of abyssal water colder than 1.1 degrees C was found to have increased by an average of 0.012 degrees C between 1975 and 2005. This warming is greater than double the standard deviation from the temporal mean temperature profile obtained from mooring observations.

DOI： 10.1029/2006JC004000

Language：English   Publishing type：Research paper (scientific journal)  

[1] Water mass characteristics and volume transports of abyssal water flowing northward into Wake Island Passage in the North Pacific Ocean were examined by carrying out high-quality hydrographic surveys in May 2003, October 2004, and December 2005 along with mooring observations from May 2003 to December 2005. Close linear relationships between potential temperature (theta) and salinity, dissolved oxygen, and silicate were seen below theta approximate to 1.1 degrees C (approximate to 4000 m). The relationships above theta approximate to 1.1 degrees C were scattered and were separated into relatively salty, oxygen-rich, silicate-poor water to the south, and water with the opposite properties to the north. The results suggested that there was a boundary between water masses at theta approximate to 1.1 degrees C in the deep passage. In addition to the three hydrographic sections, two hydrographic sections previously surveyed in the deep passage in 1975 and 1999 were reexamined for transport estimates. Geostrophic calculations relative to the theta = 1.1 degrees C surface indicated northward transports of the abyssal water from 0.5 to 2.2 Sv (1 Sv = 10(6) m(3) s(-1)) below this surface. When 1-year mean estimated velocities at theta = 1.1 degrees C surface were used for reference, mean transport from the five estimates increased from 1.4 to about 4 Sv. The temperature of abyssal water colder than 1.1 degrees C was found to have increased by an average of 0.012 degrees C between 1975 and 2005. This warming is greater than double the standard deviation from the temporal mean temperature profile obtained from mooring observations.

DOI： 10.1029/2006JC004000

Language：English   Publishing type：Research paper (scientific journal)  

Water mass characteristics and volume transports of abyssal water flowing northward into Wake Island Passage in the North Pacific Ocean were examined by carrying out high-quality hydrographic surveys in May 2003, October 2004, and December 2005 along with mooring observations from May 2003 to December 2005. Close linear relationships between potential temperature (θ) and salinity, dissolved oxygen, and silicate were seen below θ ≈ 1.1°C (≈4000 m). The relationships above θ 1.1°C were scattered and were separated into relatively salty, oxygen-rich, silicate-poor water to the south, and water with the opposite properties to the north. The results suggested that there was a boundary between water masses at θ ≈ 1.1°C in the deep passage. In addition to the three hydrographic: sections, two hydrographic sections previously surveyed in the deep passage in 1975 and 1999 were reexamined for transport estimates. Geostrophic calculations relative to the θ = 1.1°C surface indicated northward transports of the abyssal water from 0.5 to 2.2 Sv (1 SV = 106 m3 s-1) below this surface. When 1-year mean estimated velocities at θ = 1.1°C surface were used for reference, mean transport from the five estimates increased from 1.4 to about 4 Sv. The temperature of abyssal water colder than 1.1°C was found to have increased by an average of 0.012°C between 1975 and 2005. This warming is greater than double the standard deviation from the temporal mean temperature profile obtained from mooring observations. Copyright 2007 by the American Geophysical Union.

DOI： 10.1029/2006JC004000

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The relationship between the vertical profile of current on the bottom slope southeast of Okinawa Island and the offshore meso-scale eddy propagated from the east was examined by combined use of the data obtained by a moored upward-looking ADCP (Acoustic Doppler Current Profiler), PIES (Inverted Echo Sounder with Pressure gauge), hydrographic surveys and satellite altimetry during a period from November 2000 to August 2001. The variability of current component parallel to the isobath in the layer over 600 m is found to be markedly different from that in the layer below 600 m. The current variability in the upper and the lower layer can be well explained by the first and second modes of the EOF (Empirical Orthogonal Function) decomposition. The PIES and the sea surface height anomaly data suggest that the first mode represents the surface-trapped current associated with the approach of the offshore meso-scale eddy from the east, whereas the second mode has a bottom-intensified structure. The second mode velocity tends to delay to the first mode. The hydrographic data derived from CTD (Conductivity-Temperature-Depth meter) and PIES data along the line across the isobath suggest that the second mode component is generated by the interaction between the meso-scale eddy and the bottom topography.

DOI： 10.1007/s10872-006-0024-z

Language：English   Publishing type：Research paper (international conference proceedings)  

A method has been developed to monitor the surface velocity by combining satellite altimetry data and repeated acoustic Doppler current profiler (ADCP) observations. First, geostrophic velocity calculated from the altimetry data is compared with the ADCP observations, resulting in their good agreement after adjusting their spatial scales. Then, a set of observations of the temporal mean velocity is obtained by subtracting the altimetry velocity anomaly from the ADCP observations. Regularly sampled time series of surface velocity can be determined by adding the averaged mean velocity and the altimetry anomaly components, which describes variations of the Kuroshio and the Subtropical Countercurrent well.

DOI： 10.1109/IGARSS.2005.1525966

Language：English   Publishing type：Research paper (international conference proceedings)  

Correlation between the Kuroshio and coastal sea level south of Japan is examined during a non-large meander period using the altimetry and tide gauge data after removing the steric height component. The sea level varies uniformly in a region bounded by the coast and the mean Kuroshio axis, which stretches for several hundreds kilometers along the coast. These variations are related with the Kuroshio velocity, as coastal sea level decreases (or increases) when the Kuroshio is faster (or slower).

DOI： 10.1109/IGARSS.2005.1525968

Language：English   Publishing type：Research paper (international conference proceedings)  

The Kuroshio axes south of Japan was detected by [1] every 10 days from October 1992 to December 2000 from the sea-surface velocity field obtained by combining satellite altimeter and sea-surface drifter data. The axes was obtained by tracking the maximum current speed position of respective points in the Kuroshio. That axes clearly expresses the effect of the bottom topography; three modes were observed when the Kuroshio ran over the Izu Ridge. The axis was very stable to the south of Tosa-bae,' off the Kii Channel.

DOI： 10.1109/IGARSS.2005.1525967

Language：English   Publishing type：Research paper (scientific journal)  

The correlation between the Kuroshio and coastal sea level south of Japan has been examined using the altimetry and tide gauge data during the period 1992-2000. The sea level varies uniformly in a region bounded by the coast and the mean Kuroshio axis, which stretches for several hundred kilometers along the coast. These variations are related with the Kuroshio velocity, as coastal sea level decreases (or increases) when the Kuroshio is faster (or slower). To the east of the Kii Peninsula, where sea level variations are different from these to the west, movement of the Kuroshio axis additionally affects coastal sea level variations.

DOI： 10.1007/s10872-006-0014-1

Other Link： http://www.terrapub.co.jp/journals/JO/abstract/6105/61050979.html

Language：English   Publishing type：Research paper (scientific journal)  

In February 2002, a subsurface mesoscale eddy with extraordinary features was detected at a depth of about 300 dbar in the southeast of Okinawa ( a part of the Ryukyu Islands). The water mass occupying this subsurface eddy is characterized as the North Pacific Subtropical Mode Water (NPSTMW) with salinity maximum and thick thermostad; its temperature, salinity and potential density at the core of the eddy are 18.4 degrees C, 34.81 and 25.06 sigma(theta), respectively. Thickness and width of the eddy are about 300 m and 100 km, respectively. Mixing between the eddy and the surrounding water mass is also found. Such eddy with the NPSTMW has never been detected during ten years.

DOI： 10.1029/2005GL023842

Other Link： http://www.agu.org/pubs/crossref/2005/2005GL023842.shtml

Language：English   Publishing type：Research paper (scientific journal)  

A nine-year-long record of the northeastward volume transport (NVT) in the region southeast of Okinawa Island from 1992 to 2001 was estimated by an empirical relation between the volume transport obtained from the ocean mooring data and the sea surface height anomaly difference across the observation line during 270 days from November 2000. The NVT had large variations ranging from -10.5 Sv (1 Sv = 10(6) m(3)s(-1)) to 30.0 Sv around its mean of 4.5 Sv with a standard deviation of 5.5 Sv. This large variation was accompanied by mesoscale eddies from the east, having a pronounced period from 106 to 160 days. After removal of the eddy, NVT was found to fluctuate from 2 Sv to 12 Sv with a quasi-biennial period.

DOI： 10.1007/s10872-005-0004-8

Other Link： http://reo.nii.ac.jp/journal/HtmlIndicate/Contents/SUP0000001000/JOU0001000364/ISS0000122419/ART0001624220/ART0001624220.pdf

Language：Japanese   Publishing type：Research paper (scientific journal)  

Aliasing in repeat observations with inacculate sampling intervals, Kaoru Ichikawa, Oceanography in Japan

Language：Japanese   Publishing type：Research paper (scientific journal)  

Monitoring of the surface currents by repeated ADCP observations and satellite altimeters, K. Ichikawa, N. Gohda, M. Arai and A. Kaneko, Kaiyo Monthly

Language：Japanese   Publishing type：Research paper (scientific journal)  

Review: Kuroshio Variation Prediction Experiments, S. Imawaki and K. Ichikawa, Kaiyo Monthly

Language：Japanese   Publishing type：Research paper (scientific journal)  

Estimation of the Kuroshio axis south of Japan by combining satellite altimetry data and drifting buoy trajectories, D. Ambe, S. Imawaki, H. Uchida, and K. Ichikawa

Language：English   Publishing type：Research paper (scientific journal)  

By tracking the locally strongest part of the sea-surface velocity field, which was obtained by integrating data of satellite altimeters and surface drifting buoys, we extracted the Kuroshio axis south of Japan every 10 days from October 1992 to December 2000. The obtained axes clearly express the effect of the bottom topography; three modes were observed when the Kuroshio ran over the Izu Ridge. The axis was very stable to the south of 'Tosa-bae,' off the Kii Channel. Mean current speed at the Kuroshio axis gradually increased from 0.65 m/s south of Kyushu to 1.45 m/s off Enshu-nada.

DOI： 10.1023/B:JOCE.0000038343.31468.fe, 10.1023/b:joce.0000038343.31468.fe

Other Link： http://reo.nii.ac.jp/journal/HtmlIndicate/Contents/SUP0000001000/JOU0001000364/ISS0000095179/ART0001104011/ART0001104011.pdf

Language：English   Publishing type：Research paper (scientific journal)  

By tracking the locally strongest part of the sea-surface velocity field, which was obtained by integrating data of satellite altimeters and surface drifting buoys, we extracted the Kuroshio axis south of Japan every 10 days from October 1992 to December 2000. The obtained axes clearly express the effect of the bottom topography; three modes were observed when the Kuroshio ran over the Izu Ridge. The axis was very stable to the south of 'Tosa-bae,' off the Kii Channel. Mean current speed at the Kuroshio axis gradually increased from 0.65 m/s south of Kyushu to 1.45 m/s off Enshu-nada.

DOI： 10.1023/B:JOCE.0000038343.31468.fe

Language：English   Publishing type：Research paper (scientific journal)  

A method has been developed to monitor the surface velocity field by combining repeated acoustic Doppler current profiler (ADCP) observations and satellite altimetry data. The geostrophic velocity anomaly is calculated from the sea surface height anomaly field estimated from the altimetry data by an optimal interpolation. It has been confirmed that this accurately observes the smoothed velocity anomaly field when the interpolation scales are set according to the spatio-temporal sampling pattern of the altimeter used. The velocity anomaly obtained from the altimetry data is subtracted from the repeated ADCP observations to estimate temporal mean velocity along the ship tracks. Regularly sampled, nine-year time series of surface velocity can then be obtained by adding the computed mean velocity and the altimetry anomaly components. This clearly illustrates surface velocity fluctuations such as the movement of the Kuroshio axis due to its meandering and an increase of the interannual variability of the Subtropical Countercurrent toward its downstream region.

DOI： 10.1023/B:JOCE.0000038342.87237.e3

Other Link： http://reo.nii.ac.jp/journal/HtmlIndicate/Contents/SUP0000001000/JOU0001000364/ISS0000095179/ART0001104010/ART0001104010.pdf

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1023/A:1026106904472

Other Link： http://reo.nii.ac.jp/journal/HtmlIndicate/Contents/SUP0000001000/JOU0001000578/ISS0000014507/ART0000164779/ART0000164779.pdf

Language：English  

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Engineering Sciences Reports, Kyushu University

Language：Japanese   Publishing type：Research paper (scientific journal)  

Sea-surface variations as seen by satellite altimetry, K. Ichikawa, Oceanography in Japan

Language：Japanese  

Language：Japanese  

Variation of the Kuroshio in the Tokara Strait induced by meso-scale eddies

Language：English   Publishing type：Research paper (scientific journal)  

Introduction of Japanese Ocean Flux data sets with Use of Remote sensing Observations (J-OFURO)

DOI： 10.1023/A:1015845321836

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

The challenge of predicting the Japanese coastal ocean motivated Frontier Observational Research System for Global Change (FORSGC) and the Japan Marine Science and Technology Center (JAMSTEC) to start a multiyear observational programme in the upstream Kuroshio in November 2000. This field effort, the Kuroshio Observation Program (KOP), should enable us to determine the barotropic and baroclinic components of the western boundary current system, thus, to better understand interactions of the currents with mesoscale eddies, the Kuroshio instabilities, and path bimodality. We, then, will be able to improve modeling predictability of the mesoscale, seasonal, and inter-annual processes in the midstream Kuroshio near the Japanese main islands by using this knowledge. The KOP is focused on an enhanced regional coverage of the sea surface height variability and the baroclinic structure of the mainstream Kuroshio in the East China Sea, the Ryukyu Current east of the Ryukyu's, and the Kuroshio recirculation. An attractive approach of the KOP is a development of a new data acquisition system via acoustic telemetry of the observational data. The monitoring system will provide observations for assimilation into extensive numerical models of the ocean circulation, targeting the real-time monitoring of the Japanese coastal waters.

Language：English   Publishing type：Research paper (scientific journal)  

Temporal variations of the Kuroshio volume transport in the Tokara Strait and at the ASUKA line are decomposed by phase-propagating Complex EOF modes of high-resolution sea surface dynamic topography (SSDT) field during the first tandem period of TOPEX/POSEIDON and ERS-1 (from October 1992 to December 1993). Both variations are dominated by a mode with nearly semi-annual cycle, which indicates a series of interactions between the Kuroshio and meso-scale eddies. Namely, northern part of a westward-propagating meso-scale eddy at 23°N is captured into the southern side of the Kuroshio at the south of Okinawa, then it moves downstream along the Kuroshio path passing the Tokara Strait, and reaches to the ASUKA line where it merges with another eddy propagating from the east at 30°N. The variation at the ASUKA line is, however, less dominated by this mode; instead, it includes the SSDT variations in the south of Shikoku and the east of Kyushu which would be directly affected by eddies from the east without passing the Tokara Strait. On the other hand, the same analysis for movements of the Kuroshio axis in the Strait indicates that they are governed by short-term variations locally confined to the Kuroshio in the East China Sea without being induced by meso-scale eddies. This results, however, seem to depend strongly on a time scale of interest. It is suggested that the long-term movements of the Kuroshio axis in the Strait would demonstrate coincidence with SSDT variation in the south of Japan.

DOI： 10.1023/A:1011174720390

Language：English  

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Other Link： http://www.terrapub.co.jp/journals/JO/abstract/5701/57010055.html

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

In order to assess the influence of offshore meso-scale eddies in coastal areas facing to the Kuroshio, temperature data in the Bungo Channel and altimetry sea surface height (SSH) data are analyzed. It is east of Okinawa, far away from the Bungo Channel, where the SSH variation is most strongly correlated with the coastal temperature changes with periods of several weeks to months. Complex empirical orthogonal function analysis of the SSH variation indicated strong coherency with the coastal temperature for a train of meso-scale eddies propagating northeastward from east of Okinawa to south of Shikoku, suggesting that variations of the Kuroshio in front of the Bungo Channel induce the coastal temperature changes. However, in areas other than east of Okinawa and south of Shikoku, larger SSH variations which would not correlate well with the coastal temperature variations are detected showing that cross correlation with the coastal temperature is not significant in these regions.

Language：Japanese   Publishing type：Research paper (other academic)  

Velocity variations in the western North Pacific, N. Gohda, K. Ichikawa, M. Arai, H. Zheng and Y. Zhu, Kaiyo Monthly

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Summer hydrographic surveys from 1993 to 1997 in the area south of the Kuril Islands in the northwestern subarctic Pacific showed the existence of anticyclonic eddies south of the Bussol' Strait at almost the same location but with variable sizes and intensities depending on the year. Every eddy had a cold, low salinity and low potential vorticity core, suggesting a strong influence from the Okhotsk Sea water. Two formation processes and annual variations were found with satellite data analyses. One is the case where eddies are locally formed south of the Bussol' Strait and intensified from summer to fall with the supply of Okhotsk Sea water as observed in 1993. In the other case, Kuroshio warm-core rings that had translated northeastward are arrested near the Bussol' Strait and amplified with the supply of Okhotsk Sea water as seen from summer to autumn in 1995. In winter, eddies tend to move northeastward with decay. The 1992 eddy moved northeastward then northward in winter and was eventually absorbed into the East Kamchatka Current. Mechanisms of the northeastward movements and the formations of the Bussol' eddies were discussed. A pseudo-P effect due to deep northeastward currents along the Kuril-Kamchatka Trench could be responsible for the northeastward movement. Since the volume transport of the coastal Oyashio water along the southern Kuril Islands is constrained by the potential vorticity difference between the Okhotsk Sea and the western subarctic gyre (WSAG), eddies could be generated and intensified when a outflow rate from the Okhotsk Sea exceeds the critical transport. The observed annual variations of the eddy evolution might be explained by the critical transport variation associated with an annual change of the WSAG.

DOI： 10.1175/1520-0485(2000)030<1137:CCAESO>2.0.CO;2

Other Link： http://ams.allenpress.com/amsonline/?request=get-abstract&doi=10.1175%2F1520-0485(2000)030%3C1137:CCAESO%3E2.0.CO%3B2

Language：English   Publishing type：Research paper (scientific journal)  

Summer hydrographic surveys from 1993 to 1997 in the area south of the Kuril Islands in the northwestern subarctic Pacific showed the existence of anticyclonic eddies south of the Bussol' Strait at almost the same location but with variable sizes and intensities depending on the year. Every eddy had a cold, low salinity and low potential vorticity core, suggesting a strong influence from the Okhotsk Sea water. Two formation processes and annual variations were found with satellite data analyses. One is the case where eddies are locally formed south of the Bussol' Strait and intensified from summer to fall with the supply of Okhotsk Sea water as observed in 1993. In the other case, Kuroshio warm-core rings that had translated northeastward are arrested near the Bussol' Strait and amplified with the supply of Okhotsk Sea water as seen from summer to autumn in 1995. In winter, eddies tend to move northeastward with decay. The 1992 eddy moved northeastward then northward in winter and was eventually absorbed into the East Kamchatka Current. Mechanisms of the northeastward movements and the formations of the Bussol' eddies were discussed. A pseudo-P effect due to deep northeastward currents along the Kuril-Kamchatka Trench could be responsible for the northeastward movement. Since the volume transport of the coastal Oyashio water along the southern Kuril Islands is constrained by the potential vorticity difference between the Okhotsk Sea and the western subarctic gyre (WSAG), eddies could be generated and intensified when a outflow rate from the Okhotsk Sea exceeds the critical transport. The observed annual variations of the eddy evolution might be explained by the critical transport variation associated with an annual change of the WSAG.

DOI： 10.1175/1520-0485(2000)030<1137:CCAESO>2.0.CO;2

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (other academic)  

Evaluation of advection heat flux at the sea surface, K. Ichikawa and S. Imawaki, Kiyo Monthly

Language：Japanese   Publishing type：Research paper (other academic)  

Movement of warm-core rings off Tohoku as seen by satellite altimetry, K. Ichikawa, Kaiyo Monthly

Language：English   Publishing type：Research paper (scientific journal)  

Co-tidal and co-range charts of eight major constituent tides in the East China Sea and the Yellow Sea are drawn from the results of the harmonic analysis of TOPEX/POSEIDON altimetric data. Those of M₂, S₂, K₁ and O₁ constituents agree well with the traditional ones estimated from tide gauge data at coastal stations. Those Of N₂ and K₂ are similar to those of M₂ constituent and those of P₁ are similar to K₁ constituent, respectively. The amplitude of S_a constituent is large and its phase leads in the shallow part of the East China Sea and the Yellow Sea. The altimetric data from TOPEX/POSEIDON manifest very useful not only in the open ocean dynamics study but also in the coastal ocean dynamics study including tidal phenomena.

Language：English   Publishing type：Research paper (scientific journal)  

Seasonal variation in the surface circulation of the East China Sea and the Yellow Sea is investigated using altimetric data of TOPEX/POSEIDON and numerical model output. In the Yellow Sea an anticlockwise circulation develops during summer and a clockwise one during winter. In the East China Sea an anticlockwise circulation occurs during winter. Such results coincide well with those obtained by the numerical experiment and drifter buoys experiment. (C) 1997 Elsevier Science Ltd.

DOI： 10.1016/S0278-4343(96)00054-4

Language：English   Publishing type：Research paper (scientific journal)  

Optimal interpolation method is applied to Geosat altimetry data both to remove orbit error and to separate temporal mean sea surface dynamic topography (SSDT) from temporal fluctuations around the mean. Loss of long-wavelength oceanic signals at orbit error reduction procedure is smaller in this method thao that in conventional collinear methods, but the areal average height over the study domain is still removed as the orbit error. The fluctuation SSDT is quantitatively esaluated by sea level data from tide gauge stations at Japanese islands. The correlation coefficient of the two sea-level variations is 0.83 when the loss of the areal average is compensated by the seasonal variation of the areal average height determined from the climatological monthly-mean SSDT. In addition, the improvement of the geoid model by combined use of Seasat altimetry data and hydrographic data is validated through the estimated temporal mean SSDT. In a local area where hydrographic data contemporary with the Seasat mission exist, the geoid model has been significantls improved so that the absolute SSDT can be determined from combination of the altimetrs data and geoid model; the absolute SSDT describes the onset event of a quasi-stationary large meander of the Kuroshio south of Japan very wed. Outside this local area, however, errors of several tens of centimeters still remain in the improved geoid model.

DOI： 10.1007/BF02236532

Language：English   Publishing type：Research paper (scientific journal)  

Surface velocities determined from trajectory of a drifting buoy from March through November 1987 are compared with surface geostrophic velocities determined from sea surface dynamic topography (SSDT) obtained from altimetry data with the aid of long-term hydrographic observation data. In general, these velocities show similar temporal variations in both zonal and meridional components, except in a period when obvious error is found in the altimetric SSDT field. When the buoy was trapped by several mid-ocean meso-scale eddies, the comparison is especially good. Systematic discrepancy is found, however, when the buoy was in the Kuroshio region, because of using both temporally and spatially smoothed mean SSDT estimated from hydrographic data
instead, surface geostrophic velocities determined from the altimetric SSDT referred to the improved geoid model result in better comparison. © 1995 Journal of the Oceanographic Society of Japan.

DOI： 10.1007/BF02235462

Language：Others  

Comparison of surface velocities determined from altimeter and drifting buoy data

DOI： 10.1007/BF02235462, 10.1007/bf02235462

Language：English   Publishing type：Research paper (scientific journal)  

The Geosat radar altimeter data during the first year of its exact repeat mission are analyzed to investigate the behavior of individual anomalies of sea surface dynamic topography (SSDT) and their statistical properties in the Kuroshio Extension region. The SSDT anomalies are compared with mesoscale anomalies of sea surface temperature (SST) derived from satellite radiometer data. Remarkable baroclinic anomalies are detected in the time series of both SSDT and SST, and their westward propagation is clearly traced. -from Authors

DOI： 10.1029/94JC02255

Language：English   Publishing type：Research paper (scientific journal)  

The Geosat radar altimeter data during the first year of its exact repeat mission are analyzed to investigate the behavior of individual anomalies of sea surface dynamic topography (SSDT) and their statistical properties in the Kuroshio Extension region. The SSDT anomalies are compared with mesoscale anomalies of sea surface temperature (SST) derived from satellite radiometer data. Remarkable baroclinic anomalies are detected in the time series of both SSDT and SST, and their westward propagation is clearly traced. The pinching-off of a Kuroshio Extension meander at 147 degrees E is clearly seen as the coalescence of two cyclonic anomalies which had moved fairly constantly westward without changing their relative positions, Westward propagation is statistically dominant in the SSDT and SST anomaly held, Approximate agreement between SSDT and SST anomalies suggests the baroclinic nature of the anomalies. The westward phase speed of SSDT anomalies is faster than the theoretical phase speed of the baroclinic first-mode long Rossby wave in the upstream region of the Kuroshio Extension. In the downstream region it is consistent with the theoretical value but is somewhat faster around 35 degrees N. In the area between 170 degrees E and 180 degrees, SSDT anomalies have a structure like plane waves with major axis oriented NW-SE in the northern part and NE-SW in the southern part. The distribution of the Reynolds stress suggests the tendency of acceleration of the mean current by those anomalies. This strong acceleration tendency at 170 degrees E-180 degrees may be related to bathymetry.

DOI： 10.1029/94JC02255, 10.1029/94jc02255

Language：English   Publishing type：Research paper (scientific journal)  

The sea surface dynamic topography (SSDT; sea surface height relative to the geoid) is approximately estimated by combining the temporal fluctuation of SSDT determined from altimetry data with the climatological mean SSDT calculated from hydrographic data. This approximated SSDT, or composite SSDT, is obtained in the area southeast of Japan for the first year (1986-1987) of the Geosat Exact Repeat Mission. Variations in the Kuroshio Current System are well described by the composite SSDT. In particular, a complete life history of a cyclonic ring is observed for the first time in this region, namely, westward propagation of a southward meander of the Kuroshio Extension, its pinching-off to form a cyclonic ring, the ring's westward movement, its coalescence with the Kuroshio, and its eastward advection. All available hydrographic data and cloud-free satellite infrared images support the existence of this series of phenomena.

DOI： 10.1029/94JC01139, 10.1029/94jc01139

Language：English   Publishing type：Research paper (scientific journal)  

The sea surface dynamic topography (SSDT) sea surface height relative to the geoid) is approximately estimated by combining the temporal fluctuation of SSDT determined from altimetry data with the climatological mean SSDT calculated from hydrographic data. This approximated SSDT, or composite SSDT, is obtained in the area southeast of Japan for the first year (1986-1987) of the Geosat Exact Repeat Mission. Variations in the Kuroshio Current System are well described by the composite SSDT. In particular, a complete life history of a cyclonic ring is observed for the first time in this region, namely, westward propagation of a southward meander of the Kuroshio Extension, its pinching-off to form a cyclonic ring, the ring's westward movement, its coalescence with the Kuroshio, and its eastward advection. All available hydrographic data and cloud-free satellite infrared images support the existence of this series of phenomena. -Authors

Language：English   Publishing type：Research paper (scientific journal)  

The sea surface dynamic topography (the sea surface height relative to the geoid
hereafter abbreviated SSDT) can be divided into the temporal mean SSDT and the fluctuation SSDT around the mean. We use the optimal interpolation method to reduce the satellite radial orbit error and estimate the fluctuation SSDT southeast of Japan from Seasat altimetry data during the 17-day near-repeat mission. The fluctuation SSDT is further combined with the mean geopotential anomalies estimated from hydrographic data during the Seasat mission in order to give the approximated total SSDT, called here the composite SSDT (the approximated mean plus fluctuation SSDT's). The fluctuation SSDT is in accord with the low-frequency sea-level fluctuation recorded at tide gauge stations in the Japanese islands. The composite SSDT describes thoroughly variations of the location of the Kuroshio axis south of Japan determined on the basis of the GEK (Geomagnetic Electro-Kinematograph) surface velocities and the horizontal temperature distribution. The composite SSDT also agrees with oceanic variations east of Japan found in the temperature distribution at the depth of 200 m. These results confirm that the SSDT derived from altimetry data can provide fairly precise synoptic views of low-frequency oceanic phenomena. © 1992 Journal of the Oceanographic Society of Japan.

DOI： 10.1007/BF02239003

Language：Others  

Fluctuation of the sea surface dynamic topography southeast of Japan as estimated from Seasat altimetry data

DOI： 10.1007/BF02239003, 10.1007/bf02239003

Language：English   Publishing type：Research paper (scientific journal)  

Optimal interpolation technique is applied to satellite altimetry data in order to recover a sea surface elevation signal from the data, which includes a large satellite radial orbit error, also to make a map of temporal mean sea surface dynamic topography (SSDT, the mean surface height relative to the geoid). The method is applied to Seasat data for a study area southeast of Japan, for which a fairly precise gravimetric geoid is available. Estimated mean elevation field relative to the best available geoid qualitatively shows existence of the Kuroshio in a limited local area close to Honshu, Japan. But for the whole of the area studied, the elevation field is much more rugged than expected mean SSDT and appears to include a relatively large geoid error; namely, the mapped mean sea surface elevation field cannot describe the mean SSDT field. Instead, correction of the provided geoid is evaluated by this altimetrically estimated elevation field together with the mean SSDT estimated from hydrographic data.

DOI： 10.1080/01490419209388039

Responsible for pages：ISBN 978-4-621-30776-2, 758pp   Language：Japanese   Book type：Scholarly book

Language：Japanese  

CiNii Books

Language：Japanese   Book type：General book, introductory book for general audience

Language：English   Book type：Scholarly book

A wide variety of marginal basins, ranging from polar to equatorial regions, and a few sizeable enclosed basins, can all be included among the Asian Seas. The Arctic Ocean shelf seas off Siberia; the sheltered basins along the Pacific Ocean’s western rim; the coastal seas of the northernmost Indian Ocean, including the semi-enclosed Red Sea and Persian Gulf; the Caspian Sea, the remnants of the Aral Sea and a score of brackish or freshwater lakes, such as Lake Balkhash and Lake Baykal; all exhibit a multiplicity of environmental features and processes. Understanding the peculiarities of such a large and varied collection of marine and coastal types requires integrated observation systems, among which orbital remote sensing must play an essential role. This volume reviews the current potential of Earth Observations in assessing the many Asian seascapes, using both passive and active techniques in diverse spectral regions, such as measuring reflected visible and near-infrared sunlight and surface emissions in the thermal infrared and microwave range, or surface reflection of transmitted radar pulses in the microwave range. An in-depth evaluation of the available spectral regions and observation techniques, as well as of novel multi-technique methods, ensures that suitable tools are indeed accessible for exploring and managing the wealth of resources that the Asian Seas have to offer.

DOI： 10.1007/978-3-319-94067-0_11

Language：Others   Book type：Scholarly book

Event date： 2024.5

Language：English   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2024.4

Language：English   Presentation type：Oral presentation (general)  

Venue：The Berkeley Hotel, Bankok   Country：Thailand  

The Kuroshio, the western boundary current of the North Pacific, has stably taken a large meandering path south of Japan since August 2017. Variations of the wind Sverdrup transport and mesoscale eddy activities are considered major causes of the large meander, but the significant bottom topography of the Izu-Ogasawara Ridge should be one of the key factors controlling formation and deformation of the large meander of the Kuroshio. However, because of the absence of dense satellite altimeter tracks over the Izu Ridge, sea surface height (SSH) and geostrophic velocity observations over the Izu Ridge are not frequent, which would prevent accurate prediction of non-linear rapid Kuroshio path changes. Therefore, since 2022 June, we have deployed the Global Navigation Satellite System (GNSS) receivers on the ferryboat “Tachibana Maru” (Tokai Kisen, 5681t) cruising between Takeshiba Port, Tokyo to Hachijo-jima Island, which crosses the Kuroshio over the Izu Ridge twice a day. Using precise point positing (PPP) and post processed kinematic (PPK) positioning referring to fixed land GNSS stations operated by the Geospatial Information Authority of Japan, SSH variations along ship tracks are determined. After removing the EGM08 geoid height, along-route sea surface dynamic height (SSDH) variations are obtained of several tends of centimeters. The measured SSDH describes variations of the Kuroshio axis position due to its meanders, together with presence of branch currents. However, better geoid model is required, especially around islands, to increase the accuracy of absolute geostrophic velocity.

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Science South Building, Nagoya University   Country：Japan  

Unmanned Aerial Vehicles (UAVs) can provide cloud-free wide views of the sea surface from viewpoints much higher than ships. Although the coverage area size of an UAV is narrower than those of airplanes and satellites, UAVs, especially multi-copters, have another advantage that they can approach close to the sea surface. In order to use these two advantages of UAVs, we try to start a new type of operations, i.e., “Search and Sample” observations. As a prototype, water sampler is attached to the bottom of a waterproof multi-copter (SprashDrone 3+, SwellPro Co. Ltd.) which can land on the sea surface, so that the sampler can be placed on the sea surface of a target place (e.g., thermal front, red tide area, floating marine debris) detected by visible or infrared cameras on the multi-copter, and take a sample of the surface water by remotely closing the rids of the sampler bottle. This system can be efficiently operated from the land to sample coastal areas far away from ship ports, or to sample middle of lakes. The UAV can take off from and land on a ship or sea surface near a ship, even when she is under another position-keeping operation, e.g. CTD or turbulence measurements. In addition, since several multi-copters can be operated at once, the system can take many points in a short time.
Details of the prototype system will be introduced in the presentation.

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：San Juan Convention Center   Country：Puerto Rico  

Event date： 2023.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Universite de Caen Normandie   Country：France  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学吉田キャンパス   Country：Japan  

Daily observations of the Kuroshio around the Izu Ridge (I)

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Espaces Vanel, Toulouse   Country：France  

Event date： 2023.6

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン   Country：Japan  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2023.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Beverly Hills, Conrad Bangkok   Country：Thailand  

Event date： 2023.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Universidad de Cadiz   Country：Spain  

Other Link： https://www.coastalaltimetry.org/NikalWebsitePortal/coastal-altimetry-workshop/esa/

Event date： 2022.10 - 2022.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Venice   Country：Italy  

Other Link： https://ostst-altimetry-2022.com/

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：China  

Event date： 2022.5 - 2022.6

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Although synoptic wind fields around typhoons and cyclones are vital for understanding, our observations are limited. At present, only AMSR2 and CYGNSS satellites can provide synoptic observations in areas of high winds. The CYGNSS system, comprises eight microsatellites that measure reflected GNSS signals at the sea surface, estimates wind speeds continuously (at 12 min intervals), which can provide temporally averaged field in contrast to AMSR2 snapshot wind observations. In 2021, CYGNSS has modified its wind speed retrieval algorithm (Version 3.1) to include significant wave height (SWH) correction. Since wind direction and wave propagation directions vary around a moving typhoon, SWH field becomes significantly complex and asymmetric around the typhoons. In this presentation, we investigate effects of SWH corrections on CYGNSS winds around typhoons Jebi and Trami, by comparing previous version (Version 3.0) and new version products. In general, new products accounting SWH correction show right-strengthened wind patterns around typhoon centres, which are consistent with AMSR2 winds and numerical models results (ERA5 and CFSRv2). These improvements, however, are not the same in two typhoons whose movement speeds are different; fast-moving Jebi shows more significant improvements. Dependencies on moving speeds and direction of the typhoon centre, and maximum wind speeds will be further examined with other typhoon cases.

Other Link： https://www.jpgu.org/meeting_e2022/

Event date： 2022.2

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Korea, Republic of  

Event date： 2022.2

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Korea, Republic of  

Event date： 2021.10

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

沿岸域用に新たに計算されたJason-2の海面高度と，J-OFURO3データセットの海面水温を，マカッサル海峡内で比較した。海面高度の季節変動は流量の変動とよく一致しており，季節風に起因するインド洋側の水位変化と同期していたが，海面水温の季節変化とは一致していなかった。一方，季節内変動は海面高度と海面水温の変動の相関が高く，傾圧的変動が支配的であることが示唆される。海峡内の海面水温の季節内変動の伝搬特性を見ると，西岸を南から北に伝搬するケルビン波的な傾向が一部に認められた。

Event date： 2021.9 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス   Country：Japan  

Event date： 2021.9 - 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス   Country：Japan  

Event date： 2021.9 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス   Country：Japan  

Event date： 2021.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

名古屋大学宇宙地球環境研究所の研究集会として開催している「小型衛星による海洋観測」が，宇宙工学と地球観測の分野のニーズとシーズのマッチングの場として，どのように貢献してきたかを紹介する。

Event date： 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：online   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：online   Country：Japan  

Event date： 2020.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.5 - 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.2

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：San Diego   Country：United States  

Event date： 2020.2

Language：English   Presentation type：Oral presentation (general)  

Venue：ESRIN, Frascati   Country：Italy  

A new coastal retracking algorithm is applied to 20Hz Jason-2 data along four tracks in the slick-rich Sulawesi Sea in Indonesia, which alters effective footprint sizes by referring along-track series of waveforms in order to eliminate inhomogeneous microwave reflectance within the footprint. The method successfully reduce occurrence of abnormal sea surface height (SSH) measurements possibly caused by slicks, which could remain even after temporal and/or spatial smoothing procedures. Significant SSH variations in the Sulawesi Sea are revealed strongly correlated with ENSO events; positive (or negative) SSH anomaly is found along all tracks in El Nino (or La Nina) periods. In the 2009/10 El Nino period, significant negative SSHA signals were located in the eastern half of the Sulawesi Sea, suggesting presence of the Indonesian through flow from the Pacific to the Indian Ocean. Meanwhile, in the 20014/15 El Nino period, it was the western side of the Sulawesi Sea where significant negative SSHAs were found, which would suggest effect of the South China Sea through flow into the Sulawesi Sea through Makassar Strait.

Other Link： https://www.coastalaltimetry.org/

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学楽友会館   Country：Japan  

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学研究所共同館2   Country：Japan  

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学研究所共同館2   Country：Japan  

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学研究所共同館2   Country：Japan  

Event date： 2019.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡国際会議場   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山国際会議場，富山市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山国際会議場，富山市   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Hawaii Convention Center, Honolulu   Country：United States  

Other Link： http://www.oceanobs19.net/

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Hawaii Convention Center, Honolulu   Country：United States  

Other Link： http://www.oceanobs19.net/

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Domaine du Haut Carre, Bordeaux   Country：France  

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Ann Arbor, Michigan, USA   Country：Japan  

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Ann Arbor, Michigan, USA   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2019.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2019.3

Language：English  

Venue：International Convention Center Kaohsiung, Taiwan   Country：Japan  

Event date： 2019.3

Language：Japanese  

Venue：名古屋大学宇宙地球環境研究所   Country：Japan  

Event date： 2019.2

Language：Japanese  

Venue：横浜市横浜港大さん橋ホール   Country：Japan  

Event date： 2019.1

Language：Japanese  

Venue：九大応力研   Country：Japan  

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学理学部1号館   Country：Japan  

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学吹田キャンパスコンベンションセンター   Country：Japan  

Event date： 2018.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Ponta Delgada, Sao Miguel Island   Country：Portugal  

Other Link： https://www.altimetry2018.org/

Event date： 2018.6

Language：English   Presentation type：Oral presentation (general)  

Venue：ESRIN, Frascati   Country：Italy  

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.

Other Link： https://nikal.eventsair.com/QuickEventWebsitePortal/11th-coastal-altimetry-workshop/esa

Repository Public URL： http://hdl.handle.net/2324/1935834

Event date： 2018.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Honolul, Hawaii   Country：United States  

Other Link： http://www.asiaoceania.org/aogs2018/public.asp?page=home.htm

Event date： 2018.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Honolul, Hawaii   Country：United States  

Other Link： http://www.asiaoceania.org/aogs2018/public.asp?page=home.htm

Event date： 2018.5

Language：Japanese  

Venue：幕張メッセ   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

The sea surface height (SSH) is an important variable in the physical oceanography, which can provide various information such as tides, tsunami, surface geostrophic currents and the heat content of sea surface water. Satellite altimeters have been widely used to measure SSH, but their observations are spatially limited only to the satellite tracks and temporally intermittent. In this study, we have deployed a real-time kinematic (RTK) Global Navigation Satellite System (GNSS) system to D/V Chikyu in order to examine an alternative method to obtain SSH. As far as the vessel stays within about 100km from lands, the RTK GNSS would provide the height of the antenna in a geodetic coordinate, so that SSH in the given coordinate can be obtained if the vertical distance of the antenna from the sea surface are known. The antenna was originally deployed about 36m above the sea surface, but its height would change due to the draft of the vessel. In this study, this height is determined using GNSS reflectometry (GNSS-R). Since the intensity of the received signal is subject to the interferometric intensity variations between the direct and reflected signals, the time scale of the intensity variations of the received signal provides the change rate of the path length of the reflected signal during a GNSS satellite movement. The antenna height can be determined using this change rate and a simple geometry.

Event date： 2018.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Vienna   Country：Austria  

Other Link： https://www.egu2018.eu/

Event date： 2018.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Oregon Convention Center, Portland, Oregon   Country：United States  

Other Link： https://osm.agu.org/2018/

Event date： 2018.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Oregon Convention Center, Portland, Oregon   Country：United States  

Other Link： https://osm.agu.org/2018/

Event date： 2017.12

Language：English   Presentation type：Oral presentation (general)  

Venue：New Orleans Convention Center   Country：United States  

Other Link： https://fallmeeting.agu.org/2017/

Event date： 2017.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所   Country：Japan  

Event date： 2017.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台国際センター   Country：Japan  

Event date： 2017.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台国際センター   Country：Japan  

Event date： 2017.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台国際センター   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学宇治キャンパス防災研究所連携研究棟3F大セミナー室   Country：Japan  

Event date： 2017.7

Language：Japanese  

Venue：名古屋大学   Country：Japan  

Event date： 2017.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東海大学山中湖セミナーハウス   Country：Japan  

Event date： 2017.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2017.5

Language：English   Presentation type：Oral presentation (general)  

Venue：幕張メッセ   Country：Japan  

Event date： 2017.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Seogwipo KAL Hotel, Jeju   Country：Korea, Republic of  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス，富山   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス 研究所共同館1-301号室   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス 研究所共同館1-301号室   Country：Japan  

Event date： 2017.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Sant' Apollonia Auditorium, Florence   Country：Italy  

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.

Other Link： http://www.coastalaltimetry.org/

Event date： 2017.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九大筑紫地区筑紫ホール   Country：Japan  

Event date： 2016.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所，春日市，福岡県   Country：Japan  

Event date： 2016.12

Language：English   Presentation type：Oral presentation (general)  

Venue：The Moscone Center, San Francisco, California   Country：United States  

Other Link： https://agu.confex.com/agu/fm16/meetingapp.cgi

Event date： 2016.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島大学   Country：Japan  

Event date： 2016.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島大学   Country：Japan  

Event date： 2016.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Espace Encan, La Rochelle   Country：France  

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.

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：呉生涯学習センター，広島   Country：Japan  

GNSS衛星の海面での反射信号を計測するGNSS Reflectometry (GNSS-R)手法について，実観測例を交えながら解説する

Event date： 2016.9

Language：Japanese  

Venue：鹿児島大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：鹿児島大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：鹿児島大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：鹿児島大学   Country：Japan  

Event date： 2016.9

Language：Japanese  

Venue：鹿児島大学   Country：Japan  

Event date： 2016.8

Language：English   Presentation type：Oral presentation (general)  

Venue：POI Far East Branch, Vladiostok   Country：Russian Federation  

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.

Other Link： http://peace.poi.dvo.ru/eng/home/index.html

Event date： 2016.8

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Country：Japan  

Event date： 2016.6 - 2016.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学低温研究所   Country：Japan  

Event date： 2016.6 - 2016.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学低温研究所   Country：Japan  

Event date： 2016.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Viena   Country：Austria  

Event date： 2016.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡工業大学   Country：Japan  

Event date： 2016.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東大本郷キャンパス   Country：Japan  

Event date： 2016.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東大本郷キャンパス   Country：Japan  

平塚の海岸沖1km地点にある平塚海洋観測塔の屋上(海上21m)に，上向きと下向きのGNSSアンテナを設置して，GNSSの直達信号と反射信号の連続観測を開始した。また，海面反射強度を支配する海面傾斜に寄与の大きい短波長の風波の波高を計測するべく，容量式波高計も設置した。講演時には，ラジオゾンデによる大気の鉛直プロファイルが得られた2015年12月2日の結果を中心に，GNSS-R反射波の受信強度と波浪スペクトル・風速間の関係と，海面高度の変動の計測精度について報告する。

Event date： 2016.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Ernest N. Morial Convention Center, New Orleans   Country：United States  

Event date： 2016.1

Language：English   Presentation type：Oral presentation (general)  

Venue：JAMSTEC, Yokohama   Country：Japan  

Event date： 2015.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：琉球大学   Country：Japan  

Event date： 2015.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所   Country：Japan  

Event date： 2015.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所   Country：Japan  

Event date： 2015.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎大学   Country：Japan  

Event date： 2015.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Miyako-Messe   Country：Japan  

Event date： 2015.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hyatt Regency Reston, VA   Country：United States  

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.

Other Link： https://joss.ucar.edu/meetings/2015/ocean-surface-topography-science-team-meeting

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学, 松山市   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学, 松山市   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学, 松山市   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学, 松山市   Country：Japan  

海岸付近において衛星高度計のwaveform が汚染されるため、沿岸専用アルゴリズムが必要となる。これまでの研究では、各地点の瞬間のwaveformから海面高度を求めるアルゴリズムを工夫している。本研究では、連続的なwaveform時系列を用い、汚染源との位置関係を考慮することで、高精度に汚染部分を判定する。対馬付近のAltiKa 40Hz データの解析を通して、waveform 時系列からcalm waterの汚染をマスクして海面高度を求めることで、精度が1m程度改善できた。されに、footprint中の陸地面積の増加によるtrailing edgeの急減を補正することで、20cm 程度の海面高度のノイズを消すことができた。

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学, 松山市   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学, 松山市   Country：Japan  

沿岸海洋学における衛星観測の例として，沿岸域でも利用できる海面高度計の進展について説明する。

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学西新プラザ   Country：Japan  

陸上に住む我々にとって、海で何が起きているかを知る手段は限られています。これまで，どんな方法で海洋が観測されてきたかを説明しつつ，残された課題について解説します。特に、広大な海を俯瞰する上空からの視点の果たしてきた役割を強調しつつ、近年の「超小型衛星」や「無人機（ドローン）」などの、研究者や中小の事業者が自分の研究費・資金で「宇宙や空」からの視点を手に入れられる機会について、海洋学からの期待を説明します。

Event date： 2015.9

Language：Japanese   Presentation type：Symposium, workshop panel (public)  

Venue：九州大学西新プラザ   Country：Japan  

流れや温度などを測る海洋物理学や，地球環境などの視点から，現象の把握に必要な時空間スケールと，観測範囲や観測期間について紹介する

Event date： 2015.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Suntec Singapore Convention and Exhibition Centre   Country：Singapore  

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.

Other Link： http://www.asiaoceania.org/aogs2015

Event date： 2015.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学低温科学研究所   Country：Japan  

Event date： 2015.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学低温科学研究所   Country：Japan  

Event date： 2015.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学低温科学研究所   Country：Japan  

Event date： 2015.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学低温科学研究所   Country：Japan  

Event date： 2015.6 - 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Prague Congress Center   Country：Czech Republic  

Event date： 2015.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学筑紫地区共通管理棟   Country：Japan  

Event date： 2015.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Potsdam   Country：Germany  

Event date： 2015.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Naha City Bunka Tenbusu Center, Naha   Country：Japan  

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.

Event date： 2015.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Tohoku University, Sendai   Country：Japan  

Event date： 2015.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Vienna   Country：Austria  

Other Link： http://www.egu2015.eu

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京海洋大学，品川   Country：Japan  

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京海洋大学，品川   Country：Japan  

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京海洋大学，品川   Country：Japan  

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：第十一管区海上保安本部,那覇   Country：Japan  

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学野依記念講堂   Country：Japan  

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学野依記念講堂   Country：Japan  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所   Country：Japan  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所   Country：Japan  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所   Country：Japan  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：琉球大学   Country：Japan  

東シナ海は，台湾海峡と対馬海峡の流入出のほか，黒潮や河川水などの影響を受けて複雑な流況を呈している。短波海洋レーダと衛星海面高度計による海流計測の現状と，新型海面高度計などの新規ミッションの計画について紹介する。

Event date： 2014.10

Language：English  

Venue：Steigenberger Inselhotel, Konstanz   Country：Germany  

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.

Event date： 2014.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎大学水産学部，長崎   Country：Japan  

Evaluation of land effects in coastal areas in satellite altimetry observations

Event date： 2014.7 - 2014.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Royton Sapporo Hotel, Sapporo   Country：Japan  

In the mid- and high-latitude region, seasonal variation components are dominant in atmospheric and oceanic variables. For understanding the role of the Kuroshio in the North Pacific atmosphere-ocean interaction system, we examined the seasonality in the relations of volume transport (VKE) proceeding to the Kuroshio Extension (KE) region with sea surface net heat flux (HFN) in the KE region and climate indices such as NPI and others by calculating lagged cross-correlations among their 1-year-interval 3-month-mean time series for each month of the year from 1994 to 2006. VKE is the monthly mean volume transport estimated by combined use of 1-year-long IES data and multi-year satellite altimeter data. HFN is the monthly and area mean satellite-derived J-OFURO2 sea surface net heat flux in the area of 142.5°E to 152.5°E and 32.5°N to 38.5°N. It is found that February (JFM mean) VKE leads HFN by 3 months with statistically significant correlation (r=+0.766, p=0.0023) while January HFN leads VKE by 29 months with statistically significant correlation (r=-0.816, p=0.0022). September VKE has the highest correlation (r=+0.935, p=0.0001) with NINO3.4 before 40 months, and July VKE has the second highest correlation (r=+0.873, p=0.0002) with WPI before 12 months among the climate indices of NPI, WPI, AO, PDO, NPGO and NINO3.4 while December HFN has the highest correlation (r=+0.860, p=0.0002) with NPI after 2 months, and January HFN has the second highest correlation (r=-0.839, p=0.0006) with NINO3.4 before 6 months. It is confirmed in this study that KVE dominates HFN in a specific season, i.e., winter VKE leads HFN by 3 months. Close relation of winter HFN with VKE after 29 months might be explained by SLP response such as winter NPI delaying HFN by 2 months and summer WPI leading VKE by 12 months while VKE and HFN are strongly affected by NINO3.4.

Other Link： http://www.asiaoceania.org/aogs2014/public.asp?page=home.htm

Event date： 2014.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学低温科学研究所，札幌   Country：Japan  

Event date： 2014.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学筑紫キャンパス，春日   Country：Japan  

Presence Estimation of Giant Squids at a deep ocean off Ogasawara islands

Event date： 2014.4

Language：English   Presentation type：Symposium, workshop panel (public)  

Venue：Grand Hi-Lai Hotel, Kaohsiung, Taiwan   Country：Taiwan, Province of China  

Event date： 2014.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Grand Hi-Lai Hotel, Kaohsiung, Taiwan   Country：Taiwan, Province of China  

Event date： 2014.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Grand Hi-Lai Hotel, Kaohsiung, Taiwan   Country：Taiwan, Province of China  

Event date： 2014.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京海洋大学，品川，東京   Country：Japan  

Event date： 2014.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京海洋大学，品川，東京   Country：Japan  

Event date： 2014.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京海洋大学，品川，東京   Country：Japan  

Event date： 2014.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Hawaii Convention Center, Honolulu, Hawaii   Country：United States  

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.

Event date： 2014.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Hawaii Convention Center, Honolulu, Hawaii   Country：United States  

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.

Event date： 2014.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Hawaii Convention Center, Honolulu, Hawaii   Country：United States  

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.

Event date： 2013.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所，春日，福岡   Country：Japan  

Event date： 2013.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：情報通信研究機構沖縄電磁波研究センター，名護，沖縄   Country：Japan  

Event date： 2013.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Millennium Harvest House Hotel, Boulder, Colorado   Country：United States  

Event date： 2013.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学，札幌   Country：Japan  

Event date： 2013.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学，札幌   Country：Japan  

Event date： 2013.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京農工大小金井キャンパス，小金井   Country：Japan  

Event date： 2013.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Gothenburg Convention Center   Country：Sweden  

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.

Other Link： http://iahs-iapso-iaspei2013.com/

Event date： 2013.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Gothenburg Convention Center   Country：Sweden  

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.

Other Link： http://iahs-iapso-iaspei2013.com/

Event date： 2013.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北大低温研   Country：Japan  

Event date： 2013.5

Language：English   Presentation type：Oral presentation (general)  

Venue：CNES Headquaters, Paris   Country：France  

Event date： 2013.3

Venue：東京海洋大学品川キャンパス   Country：Japan  

Event date： 2013.3

Venue：東京海洋大学品川キャンパス   Country：Japan  

Event date： 2013.3

Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所   Country：Japan  

Event date： 2013.2

Presentation type：Oral presentation (general)  

Venue：情報通信研究機構沖縄電磁波技術センター   Country：Japan  

Event date： 2013.2

Presentation type：Oral presentation (general)  

Venue：情報通信研究機構沖縄電磁波技術センター   Country：Japan  

NICTの与那国島の遠距離海洋レーダは，単体では視線方向流速しか計測できないが，台湾のTORIが運用する海洋レーダと組み合わせることで，黒潮上流域の全域をカバーする流速場の観測を提供することが可能となる。ただし，両レーダは計測方式が異なるため，両者の合成は単純ではない。さらに，対象海域には，強流域である黒潮に加え，現象の時空間スケールが大きく異なる外洋と沿岸を含んでおり，作成したデータの評価すら容易ではないと考えられる。そこで，日本と台湾の研究グループは，2012年6月に互いに研究観測船を準備して，黒潮上流域全体で現場観測を行った。本発表では，観測の概要と，結果の一部を紹介する。特に，観測船から放流したGPS付漂流ブイの軌跡から求めた流速を用いて，異なる曳航帯深度での比較による水平流速の鉛直構造の違いや，NICTとTORIの各々のレーダの視線方向流速との比較による流速場の誤差特性についての議論を行う。

Event date： 2012.12

Presentation type：Oral presentation (general)  

Venue：RIAM, Kyushu Univ, Kasuga   Country：Japan  

Event date： 2012.12

Presentation type：Oral presentation (general)  

Venue：RIAM, Kyushu Univ, Kasuga   Country：Japan  

Event date： 2012.12

Presentation type：Oral presentation (general)  

Venue：RIAM, Kyushu Univ, Kasuga   Country：Japan  

Event date： 2012.12

Presentation type：Oral presentation (general)  

Venue：水産大学校講義棟，下関   Country：Japan  

Event date： 2012.11

Presentation type：Oral presentation (general)  

Venue：Nagoya University, Nagoya   Country：Japan  

Event date： 2012.11

Presentation type：Oral presentation (general)  

Venue：Nagoya University, Nagoya   Country：Japan  

By international collaboration of the Japanese and Taiwanese institutes, ocean radar data with significantly wide coverage in the upstream Kuroshio region have been preliminary obtained. Meanwhile, intensive in situ observations within the radar coverage were conducted in June 2012 as the international join survey by the Japanese Research Vessel Tansei-maru and the Taiwanese R/V Ocean Researcher-2. Details of the joint survey are presented in this presentation, with brief descriptions of preliminary results on the surface and subsurface currents near and within the upstream Kuroshio. Especially, trajectories of the surface drifters with and without drogues at 15-m depth exhibit clear influence of the surface wind-driven currents, even in the Kuroshio region.

Event date： 2012.11 - 2012.10

Venue：IMA House, Kochi   Country：India  

Satellite altimeters have provided valuable sea surface height (SSH) observations in open oceans, but their use is limited in coastal region by many technical reasons, including signal contamination by lands and large complicated tides. Moreover, even for coastal-oriented altimeters such as SARAL/AltiKa, the temporal and spatial sampling intervals of the satellite altimeters are too coarse for smaller-scale coastal phenomena. Thus, in this study, complementary observations of the coastal SSH using GPS are examined, and compared with present coastal altimetry products, together with validations by current observations from ferry-board ADCP and ocean HF radars.

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 whose amplitude reaches to a few meters in windy weather conditions. They would be caused by wind waves, and can be smoothed out by averaging over the ship route, although the averaging periods are required to be longer than approximately eight minutes as long-period waves aliased in the 30-second sampling intervals.
In winter, the cross-strait SSH profiles in daytime cruises agree well with those in night cruises, but they are significantly different in summer. Since the accuracy of the RTK GPS observations is known to decrease in daytime and in summer when activities of the troposphere and ionosphere are higher, we used the data in night cruises only for further analysis.

By removing tidal and geoid heights estimated by available local models, we determined the sea surface dynamic height (SSDH), which is compared with the dynamic height calculated from the 18-m depth de-tided velocity observed by acoustic Doppler current profiler (ADCP) mounted on the same ferryboat. Although patterns of both SSDT profiles, such as positions of peaks and slopes, agree in general, the root-mean-square (rms) difference remains a few decimetres. Excluding errors of tidal and geoid models by obtaining temporal variations of the monthly means, the similarity between two SSDT anomalies is improved as the reduced rms difference of several centimeters. The is significantly better than the comparison between the SSDT anomalies along the nearby Jason-2 sub-satellite track in the Tsushima Strait and the corresponding SSDT anomaly calculated from the surface velocity field observed by the ocean HF radars.

Other Link： http://www.porsec2012.incois.gov.in/

Event date： 2012.9

Presentation type：Oral presentation (general)  

Venue：Venice Convention Centre Palazzo del Casino, Lido, Venice   Country：Italy  

Other Link： http://www.altimetry2012.org/

Event date： 2012.9

Presentation type：Oral presentation (general)  

Venue：Venice Convention Centre Palazzo del Casino, Lido, Venice   Country：Italy  

Other Link： http://www.altimetry2012.org/

Event date： 2012.9

Presentation type：Oral presentation (general)  

Venue：東海大学清水キャンパス，清水，静岡   Country：Japan  

Event date： 2012.9

Presentation type：Oral presentation (general)  

Venue：東海大学清水キャンパス，清水，静岡   Country：Japan  

Event date： 2012.9

Presentation type：Oral presentation (general)  

Venue：東海大学清水キャンパス，清水，静岡   Country：Japan  

Event date： 2012.8

Presentation type：Oral presentation (general)  

Venue：Resorts World Convention Centre   Country：Singapore  

Event date： 2012.8

Presentation type：Oral presentation (general)  

Venue：Resorts World Convention Centre   Country：Singapore  

Event date： 2012.8

Presentation type：Oral presentation (general)  

Venue：東京大学大気海洋研究所   Country：Japan  

船舶観測が不要ではないかという議論は，アルゴ時代に入る前に，既にリモセンによる観測が活発になる時代から行われていた。実際，圧倒的な観測範囲と反復性を誇るリモセンは，特に外洋域では船舶を凌駕するものである。ただ，多くの衛星観測は，海面のすぐ近くにのみ限定されているため，船舶観測と共存する余地が多かった。ただ，深い主温度躍層の動きを反映する海面高度などは，船舶による密度場観測の主要素のみを抽出したような物理量が取得できるため，船舶観測との重複性が指摘されることも多かった。船舶観測としては，１．海面高度計では求めにくい平均流速場の推定，２．亜表層・深層の流速構造，３．高度計がうまく機能しない沿岸域・極域，軌道間のサブメソスケールの渦，などを対象とすることで，折り合いをつけてきたように思われる。ただし，将来的には沿岸高度計などが計画されているので，Altimeter, Argo, Assimilationの組み合わせに対して，船舶がどう向かい合うかを真剣に考える必要があると思われる。

Event date： 2012.7

Presentation type：Oral presentation (general)  

Venue：北海道大学低温科学研究所   Country：Japan  

海面高度は海面の地衡流等を計測する上で重要な物理量だが，外洋域での利用を念頭に開発された衛星海面高度計などでは測定は困難である。本発表シリーズでは，沿岸域の対馬海峡でのGPSを用いた海面高度測定に関しての発表を行う。今回は，前回の初期解析で問題となっていた往路と復路での海面高度の違いに関して考慮した。航路の変化によるジオイドの変動の影響や，喫水変化の効果を検討したが，長期間の時系列を解析することで，往路と復路の違いは夏季にのみ顕著であり，特に昼間の往路の観測結果が大きく違っていることが分かった。これより，夏季の昼間に水蒸気や電離層の活動が活発になり，それによる電波遅延が生じたのが原因であることがうかがえた。

Event date： 2012.5

Presentation type：Oral presentation (general)  

Venue：Mayfield Hotel, Seoul   Country：Korea, Republic of  

Since July 2001, the sea surface currents in the upstream region of the Kuroshio have been monitored by a long-range ocean radar system developed and maintained by the National Institute of Information and Communications Technology (NICT), Japan. The long-term NICT radar data with a wide field of view and sufficient spatial-temporal resolutions have revealed interesting variations of the upstream Kuroshio with various time scales from a few days to a few years; i.e. meander of the Kuroshio in response to the interaction of mesoscale eddies, frontal eddies of the Kuroshio, and extraordinary on-shelf shift of the Kuroshio axis during a typhoon attack.

Other Link： http://korf.kunsan.ac.kr/xe/index.php?mid=orca

Event date： 2012.3

Presentation type：Symposium, workshop panel (public)  

Venue：筑波大学，つくば市   Country：Japan  

日本南方の係留系観測と，海面高度計データから，伊豆海嶺を超えて黒潮続流域に向かう流量・熱流量を推定した。その変動量は，より上流の変動よりも安定していて，これは伊豆海嶺の西側を南下する再循環流によるものであることがわかった。

Event date： 2012.3

Presentation type：Oral presentation (general)  

Venue：筑波大学，つくば市   Country：Japan  

台湾海峡を横断する台馬フェリーに取り付けたADCP流速計のデータを解析し，台湾海峡通過流量を長期モニタリングした結果について調べた。特に，その季節変動特性と，エクマン輸送による流量変化について議論した。

Event date： 2012.3

Presentation type：Oral presentation (general)  

Venue：筑波大学，つくば市   Country：Japan  

九州南東方のパラオ海嶺・トカラ海盆周辺で，吊り下げ式ADCP流速計（LADCP）観測を行ったところ，水深3000m以深の海底付近に非常に強い流れが見つかった。密度成層が非常に弱かったことから，これは地衡流成立した流れではなく，強化流の厚さは粘性境界よりもずっと大きかった。この強化流が，トカラ海盆内に補足された内部潮汐起源の流れである可能性について検討した。

Event date： 2012.3

Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所，春日   Country：Japan  

対馬海峡を横断するフェリー「ニューかめりあ」にGPS受信機を搭載し，海面力学高度分布を測定した。夏季の昼間のデータは水蒸気や電離層による電波遅延の影響でデータの品質が特に悪いことがわかった。夜間のデータのみに限定すると，ある程度の精度で海面力学高度が測定できていることが，ADCP流速計から地衡流を仮定した海面力学高度変動と比較して判明した。

Event date： 2012.3

Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所，春日   Country：Japan  

台湾海峡を横断する台馬フェリーに取り付けたADCP流速計のデータを解析し，台湾海峡通過流量の季節変動特性について調べた

Event date： 2012.3

Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所，春日   Country：Japan  

台湾北東沖の黒潮流軸変動と，台湾東方から西進してくる中規模渦との関係を，比較的単純な数値実験を用いて検討した。接近する中規模渦が高気圧性渦か低気圧性渦かで，各々黒潮流速の強化・弱化と流軸位置の南下・北上が生じるなど対称的な結果が得られたが，高気圧性渦の方が黒潮による移流の効果を受けやすいなど対照性が崩れた結果も見られた。これらの非対称性に対する，渦の非線形性にの効果を検討した。

Event date： 2012.2

Presentation type：Oral presentation (general)  

Venue：名古屋大学   Country：Japan  

名古屋大学とNICTの共同利用の一環として，台湾海洋研究所との共同研究規約を締結した。これにより，与那国島の海洋レーダと，台湾東岸に設置された海洋レーダを併用して黒潮全幅を観測することが可能となる。

Event date： 2012.1

Presentation type：Oral presentation (general)  

Venue：三重大学   Country：Japan  

Event date： 2011.11

Presentation type：Oral presentation (general)  

Venue：北海道大学低温研究所   Country：Japan  

Event date： 2011.10

Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2011.9

Presentation type：Oral presentation (general)  

Venue：九州大学筑紫キャンパス，春日   Country：Japan  

Event date： 2011.6 - 2011.7

Presentation type：Oral presentation (general)  

Venue：Melbourne Convention & Exhibition Center   Country：Australia  

Event date： 2011.6 - 2011.7

Presentation type：Oral presentation (general)  

Venue：Melbourne Convention & Exhibition Center   Country：Australia  

Event date： 2011.4

Venue：GIS NTU convention ceenter   Country：Taiwan, Province of China  

Event date： 2011.3

Venue：東京大学柏キャンパス（紙面発表），千葉   Country：Japan  

Event date： 2011.3

Presentation type：Oral presentation (general)  

Venue：情報通信研究機構沖縄亜熱帯計測技術センター，沖縄県恩納村   Country：Japan  

Event date： 2011.3

Presentation type：Oral presentation (general)  

Venue：情報通信研究機構沖縄亜熱帯計測技術センター，沖縄県恩納村   Country：Japan  

Event date： 2010.12

Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所，春日   Country：Japan  

Event date： 2010.12

Presentation type：Oral presentation (general)  

Venue：九州大学応用力学研究所，春日   Country：Japan  

Event date： 2010.10

Presentation type：Oral presentation (general)  

Venue：FIL Meeting Centre of Feira Internacional de Lisboa, Lisbon   Country：Portugal  

Event date： 2010.10

Presentation type：Oral presentation (general)  

Venue：Factory of Science, University of Porto, Porto   Country：Portugal  

Event date： 2010.9

Presentation type：Oral presentation (general)  

Venue：東京農工大学網走キャンパス   Country：Japan  

Event date： 2010.9

Presentation type：Oral presentation (general)  

Venue：東京農工大学網走キャンパス   Country：Japan  

Event date： 2010.9

Presentation type：Oral presentation (general)  

Venue：東京農工大学網走キャンパス   Country：Japan  

Event date： 2010.7

Presentation type：Oral presentation (general)  

Venue：北海道大学低温科学研究所   Country：Japan  

Event date： 2010.6

Presentation type：Oral presentation (general)  

Venue：Taipei International Convention Center   Country：Japan  

Other Link： http://www.agu.org/meetings/wp10/index.php

Event date： 2010.6

Presentation type：Oral presentation (general)  

Venue：Taipei International Convention Center   Country：Japan  

Other Link： http://www.agu.org/meetings/wp10/index.php

Event date： 2010.3

Presentation type：Oral presentation (general)  

Venue：東京海洋大学   Country：Japan  

Event date： 2010.3

Presentation type：Oral presentation (general)  

Venue：東京海洋大学   Country：Japan