Publishing type：Research paper (scientific journal)  

© 2020 Elsevier Ltd A model of the beach process of marine plastics was proposed based on the assumption of the beaching and backwashing flux balance, and its applicability was examined by means of time-invariant linear system analysis and particle tracking experiments with respect to the ratio between the residence time of plastics on a beach (τr) and the period of nearshore current variability (T0). Based on the theory, the balance was expected to hold when τr/T0 was much smaller than 1; however, good agreement was obtained between the theory and the particle tracking method for much larger values of τr/T0. The parameters, which are diagnostically given in the model, will be prognostically decided by the coastal dynamics in the future to develop robust beach process models. Nevertheless, we believe that a diagnostic approach would be another pillar in the strategy for estimating the amounts and distributions of marine plastics in the coming years.

DOI： 10.1016/j.marpolbul.2020.110910

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> This study develops how to assimilate tsunami currents observed by high frequency ocean radars in three dimensional current modeling for the projection of tsunami debris in case the Nankai Trough Megathrust earthquake occurs. Regional Ocean Modeling System (ROMS) is used for the assimilation in Osaka Bay with forcings of tides, freshwater, and wind as well as tsunami currents in three dimensional coordinates. In order to assimilate the tsunami component of the surface currents with the consideration of a tsunami's momentum, high-frequency component is extracted from the observed surface velocities using discrete wavelet transform and assimilated to all vertical layers by nudging. This pragmatic approach better represents both of currents and surface elevation.</p>

DOI： 10.2208/kaigan.75.I_1315

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> Recent researches on tsunami detection with high-frequceny ocean surface radars revealed that the tsunami-detection performance with high-frequecny ocean surface radar (HF radar) strongly depends on the sea surface state and ionospheric condition, means that to realize tsunami early warning system using HF radars, we need to comprehend the seasonal variation of the tsunami detection performance based on longterm radar observations in different sea surface and/or ionospheric conditions. Here, we examined the seasonal variation based on virtual tsunami observation experiments using one-year (2014) HF radar observation data obtained at the west coast of Kii Peninsula and a tsunami simulation for a <i>M_w</i> 9.0 Nankai Trough earthquake. We concluded that the tsunami detection performance on the continental shelf slope depends on ionospheric conditions as well as sea surface state.</p>

DOI： 10.2208/kaigan.75.I_1309

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

Microplastics have adverse effects on marine life. This study examined the abundance and size of microplastics as well as their polymer types in the surface water and the bottom and beach sediments of Hiroshima Bay. The fragmentation process and sinking factors of foamed polystyrene (FPS) microplastics were also examined. Serious FPS pollution spread out not only in the beach sediments but also in the bottom sediments. The average size of FPS particles in the bottom sediments was significantly smaller than that of beached FPS particles. Field emission scanning electron microscopy images suggest that large amounts of microsized or nanosized FPS fragments are likely to be generated from the margins of beached FPS microplastics. X-ray computed tomography images show that FPS microplastics from the bottom sediments had tunnel-like structures inside the particle. Based on these images, FPS microplastics in the bottom sediments were susceptible to biofouling and soil deposition.

DOI： 10.1016/j.marpolbul.2018.05.036

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© 2018 by the authors. The tsunami generated by the 2011 Tohoku-Oki earthquake was the first time that the velocity fields of a tsunami were measured by using high-frequency oceanographic radar (HF radar) and since then, the development of HF radar systems for tsunami detection has progressed. Here, a real-time tsunami detection method was developed, based on virtual tsunami observation experiments proposed by Fuji et al. In the experiments, we used actual signals received in February 2014 by the Nagano Japan Radio Co., Ltd. radar system installed on the Mihama coast and simulated tsunami velocities induced by the Nankai Trough earthquake. The tsunami was detected based on the temporal change in the cross-correlation of radial velocities between two observation points. Performance of the method was statistically evaluated referring to Fuji and Hinata. Statistical analysis of the detection probability was performed using 590 scenarios. The maximum detection probability was 15% at 4 min after tsunami occurrence and increased to 80% at 7 min, which corresponds to 9 min before tsunami arrival at the coast. The 80% detection probability line located 3 km behind the tsunami wavefront proceeded to the coast as the tsunami propagated to the coast. To obtain a comprehensive understanding of the tsunami detection probability of the radar system, virtual tsunami observation experiments are required for other seasons in 2014, when the sea surface state was different from that in February, and for other earthquakes.

DOI： 10.3390/rs10071126

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Blackwell Publishing Ltd  

Tsunami waves and the subsequent natural oscillations generated by the 2011 Tohoku earthquake were observed by two high-frequency (HF) radars and four tidal gauge records in Ise Bay. The radial velocity components of both records increased abruptly at approximately 17:00 (JST) and continued for more than 24 h. This indicated that natural oscillations followed the tsunami in Ise Bay. The spectral analyses showed that the tsunami wave arrivals had periods of 16–19, 30–40, 60–90, and 120–140 min. The three longest periods were remarkably amplified. Time-frequency analysis also showed the energy increase and duration of these periods. We used an Empirical Orthogonal Function (EOF) to analyze the total velocity of the currents to find the underlying oscillation patterns in the three longest periods. To verify the physical properties of the EOF analysis results, we calculated the oscillation modes in Ise Bay using a numerical model proposed by Loomis. The results of EOF analysis showed that the oscillation modes of 120–140 and 60–90 min period bands were distributed widely, whereas the oscillation mode of the 30–40 min period band was distributed locally. The EOF spatial patterns of each period showed good agreement with the eigenmodes calculated by the method of Loomis (1975). Thus, the HF radars were capable of observing the tsunami arrival and the subsequent oscillations.

DOI： 10.1029/2017JC013626

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

&nbsp;In the 2011 Tohoku earthquake tsunami disaster, the oceanographic radars installed at the coastal area of Japan and USA observed the tsunami, which proved the possibility for tsunami observation by using oceanographic radar. After the Tohoku tsunami, studies by using oceanographic radar were reported, but the research topics were mainly on tsunami observation and detection. Quantitative evaluations such as the estimation of wave peak is important in order that oceanographic radar contributes to tsunami disaster prevention and mitigation. In this study, the method to estimate a wave peak of tsunami by using a single oceanographic radar was examined and applied for a tsunami scenario in the Nankai Trough. The tsunami numerical modeling for the tsunami source of <i>M</i>w9.1 and 8.6 in the Nankai Trough was carried out and gave radial velocity distributions to be observed by oceanographic radar. The wave peak was estimated by using the radial velocity distribution and was compared with the wave peak calculated by the outputted water distribution. As a result, the location of the wave peak is estimated well. And the water level of the wave peak is estimated with an error range of -20% to 10%.

DOI： 10.2208/kaigan.74.I_511

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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

The combination of a high-frequency ocean surface radar and a tsunami detection method should be assessed as the onshore-offshore distribution of tsunami detection probability, because the probability will vary in accordance with the signal-to-noise ratio (SNR) and the tsunami magnitude in addition to the radar system specifications. Here, we statistically examine the tsunami detection distance based on virtual tsunami observation experiments by using signals received by a high-frequency radar in February 2014 installed on the southern coast of Japan and numerically simulated velocities induced by a Nankai Trough earthquake. In the experiments, the Doppler frequencies associated with the simulated velocities were superimposed on the receiving signals of the radar, and the radial velocities were calculated from the synthesized signals by the fast Fourier transform. Tsunami arrival was then detected based on the temporal change in the cross-correlation of the velocities, before and after tsunami arrival, between two points 3 km apart along a radar beam. We found that the possibility of tsunami detection primarily depends on the kinetic energy ratio between tsunami current and background current velocities. The monthly average detection probability is over 90% when the energy ratio exceeds 5 (offshore distance: 9 km &lt;= L &lt;= 36 km) and reduces to 50% when the energy ratio is approximately 1 (L = 42 km) over the shelf slope. The ratio varied with the background current physics and SNR, which was mainly affected by ocean surface wave heights and ionospheric electron density.

DOI： 10.1007/s10872-017-0428-y

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

&nbsp;We developed a real-time tsunami detection technique and verified its performance based on a virtual tsunami observation experiment proposed by Fuji et al. (2015). We supposed that a tsunami caused by a Nankai Trough earthquake (Japan cabinet office's fault model case 3) happened at 6:00 on February 1, 2014. We used receiving signals observed on the same day by a HF radar installed on the Mihama coast in Wakayama prefecture and numerically simulated tsunami velocities induced by Nankai Trough earthquake. We found that the tsunami wavefront was detected 13 minutes after tsunami occurance at 31.5 km offshore in the case that the threshold of cross-correlation, which was calculated by observed velocities , was top 1%. The results show that larger threshold enables us to detect the wavefront earlier.

DOI： 10.2208/kaigan.73.I_1615

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

&nbsp;We attempted to observe the 2015 Illapel Earthquake Tsunami in Japan by using the oceanographic radar, however we could not detect it. Hence, we carried out numerical modeling of the tsunami and showed that the tsunami velocity was smaller than the observable velocity of the radar. On the other hand, a numerical experiment of the 1960 Chile Earthquake Tsunamis indicated that the radar could have detected it. Further, we conducted a virtual tsunami experiment including background noise and observation flow. The experiment result showed that the tsunami detection distance was 25.5 km when cross-correlation calculating period and distance were 3 hours and 3 km.

DOI： 10.2208/kaigan.73.I_433

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Residence times of microplastics were estimated based on the dependence of meso- and macrolitter residence times on their upward terminal velocities (UTVs) in the ocean obtained by one- and two-year mark-recapture experiments conducted on Wadahama Beach, Nii-jima Island, Japan. A significant linear relationship between the residence time and UTV was found in the velocity range of about 0.3-0.9 ms(-1), while there was no significant difference between the residence times obtained in the velocity range of about 0.9-1.4 ms(-1). This dependence on the UTV would reflect the uprush-backwash response of the target items to swash waves on the beach. By extrapolating the linear relationship down to the velocity range of microplastics, the residence times of microplastics and the 1D onshore-offshore diffusion coefficients were inferred, and are one to two orders of magnitude greater than the coefficients of the macroplastics.

DOI： 10.1016/j.marpolbul.2017.05.012

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DOI： 10.2208/jscejhe.73.I_1225

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DOI： 10.2208/kaigan.72.I_463

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

&nbsp;A tsunami generated by &ldquo;The 2011 off the Pacific coast of Tohoku Earthquake&rdquo; was observed by two oceanographic radars in Ise Bay. This tsunami generated the natural oscillation with period bands of 120-140, 60-90 and 30-40 min in the Bay. To clarify these oscillation modes, we used an EOF analysis on the total velocity data and numerical calculation proposed by Loomis. From the results, we showed that the oscillation modes of 120-140 and 60-90 min period bands were comparatively wide-area oscillation, whereas the oscillation mode of 30-40 min period bands was extremely local oscillation.

DOI： 10.2208/kaigan.72.I_1723

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

We propose a belt transect setting strategy for mark-recapture experiments (MREs) to evaluate the time-independent 1D diffusion coefficient (&lt; D-p0 &gt;) of marine litter in the cross-shore direction that determines the backwashing flux of the litter, based on two-year MREs for plastic floats (PFs) on Wadahama Beach, Nii-jima Island, Japan. When the alongshore width of the belt transect (L-t) was of the order of, or longer than, the length scale of wave-induced nearshore current circulation (L-c), the PFs were rarely transported alongshore across the selected transects prior to being backwashed offshore. Thus, the transect residence time became longer and showed a much weaker dependence on the transect position, in contrast to when L-t was even shorter than L-c. We therefore obtained the diffusion coefficients close to the value of (&lt; D-p0 &gt;) when we set L-t to the order of, or longer than, L-c. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2016.05.016

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

A tsunami generated by "The 2011 off the Pacific coast of Tohoku Earthquake" was observed by two high frequency ocean surface radars (HF radars) and four tide gauges installed on Ise Bay. The tsunami wave arrived initially at 16: 50 was observed by tide gauge which is installed on the mouth of the Bay. This wave propagation was also observed by HF radars installed on the inner part of the Bay. Therefore, these observations were considered to be correlated. The result of spectral analysis, the tsunami wave had energy with period bands of 120-140, 60-90 and 30-40 min. In comparison to the previous study suggest that these 60-90 and 30-40 min periods oscillations were attributed to the tsunami source fault.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A key factor for determining the residence time of macroplastics on a beach is the process by which the plastics are backwashed offshore (backwash process). Here, we deduced the backwash process of plastic fishing floats on Wadahama Beach based on the analysis of two-year mark-recapture experiments as well as nearshore current structures revealed by sequential images taken by za webcam installed at the edge of a cliff behind the beach. The analysis results revealed the occurrence of a combination of offshore currents and convergence of alongshore currents in the surf zone in storm events around a submerged breakwater off the northern part of the beach, where 48% of the backwashed floats were last found. We conclude that the majority of the floats on the beach were transported alongshore and tended to concentrate in the convergence zone, from where they were backwashed offshore by the nearshore currents generated in the events. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2015.10.060

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

We established a method for evaluating beach cleanup effects (BCEs) based on a linear system analysis, and investigated factors determining BCEs. Here we focus on two BCEs: decreasing the total mass of toxic metals that could leach into a beach from marine plastics and preventing the fragmentation of marine plastics on the beach. Both BCEs depend strongly on the average residence time of marine plastics on the beach (tau(r)) and the period of temporal variability of the input flux of marine plastics (1). Cleanups on the beach where tau(r) is longer than Tare more effective than those where tau(r) is shorter than T. In addition, both BCEs are the highest near the time when the remnants of plastics reach the local maximum (peak time). Therefore, it is crucial to understand the following three factors for effective cleanups: the average residence time, the plastic input period and the peak time. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2014.12.026

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IAHR-INT ASSOC HYDRO-ENVIRONMENT ENGINEERING RESEARCH  

Most marine debris are primarily supplied from inland areas; however, few monitoring data exist for floating-litter transport from rivers to the ocean due to the absence of appropriate monitoring methods. In this study, we developed an automatic and continuous monitoring technique for floating-litter transport L in rivers by using an image monitoring and processing technique in which different types of litter (scatter-type and mass-type) are separately analyzed. The results indicated that L evaluated by the present methods was in good agreement with the observed data in the Mogami River, Yamagata, Japan, demonstrating the fundamental performance of the present monitoring method.

DOI： 10.2208/jscejhe.71.I_1225

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

This study examines the possibility of detecting the first wave of a tsunami by oceanographic radar based on a virtual tsunami observation experiment. Radial velocities obtained by tsunami simulation are converted into modulating signals and superimposed on signals measured by oceanographic radar installed on the Mihama coast. Then the radial velocities are calculated from the combined signals which are to be measured by oceanographic radar. We call this procedure 'virtual tsunami experiment', and use it to investigate the possibility of tsunami detection using cross-correlation between two observation points in a radial direction. When the cross-correlation increases significantly and in a correlated manner with the passage of the first tsunami wave, we judge that the oceanographic radar has detected the tsunami at the points where the correlation is calculated. We found that the location of the furthest-offshore points where the first wave was detected by the radar depends on the distance between the two observation points. The dependence of the distance of tsunami detection on the distance between the two points is also discussed.

DOI： 10.2208/kaigan.71.I_337

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IAHR-INT ASSOC HYDRO-ENVIRONMENT ENGINEERING RESEARCH  

Most marine debris are primarily supplied from inland areas; however, few monitoring data exist for floating-litter transport from rivers to the ocean due to the absence of appropriate monitoring methods. In this study, we developed an automatic and continuous monitoring technique for floating-litter transport L in rivers by using an image monitoring and processing technique in which different types of litter (scatter-type and mass-type) are separately analyzed. The results indicated that L evaluated by the present methods was in good agreement with the observed data in the Mogami River, Yamagata, Japan, demonstrating the fundamental performance of the present monitoring method.

DOI： 10.2208/jscejhe.71.I_1225

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Large quantities of plastic litter are expected to wash ashore along the beaches of the East Asian marginal seas in the coming decade. Litter quantities were predicted using three techniques: a particle tracking model (PTM) used in conjunction with two-way PTM experiments designed to reveal litter sources, an inverse method used to compute litter outflows at each source, and a sequential monitoring system designed to monitor existing beach litter using webcams. Modeled year-to-year variation in litter quantities indicated that the amount of litter would continue to increase in the East Asian marginal seas if the level of outflow remains constant in the coming decade. The study confirms that about 3% of all East Asian beaches may potentially experience a 250-fold increase in the amount of plastic beach litter washed ashore in the next 10 years. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2014.01.057

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

This study investigates the horizontal and residual circulations in Tokyo Bay using field observations, numerical simulations, and theoretical analysis. Numerical simulations show that the observed deepening of isopycnals and associated anticyclonic horizontal circulation in the bay head are mainly driven by negative wind stress curl. The effects of river discharge, surface heat fluxes, and tides are found to be small. Under strong wind events, the wind stress curl over the bay head can be large enough to make the surface Ekman layer strongly nonlinear. Theoretical and numerical analyses show that, under large negative wind stress curl, the nonlinearity tends to induce positive pumping velocity (at the base of the surface mixed layer) that counteracts the Ekman pumping; however, the typical duration of wind events in the bay head is not long enough to induce positive pumping under negative wind stress curl. These results and historical wind data suggest that the average horizontal circulation and residual circulation immediately below the surface mixed layer in Tokyo Bay are, respectively, cyclonic and convergent in summer but anticyclonic and divergent in winter.

DOI： 10.1002/2013JC009396

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Blackwell Publishing Ltd  

This study investigates the horizontal and residual circulations in Tokyo Bay using field observations, numerical simulations, and theoretical analysis. Numerical simulations show that the observed deepening of isopycnals and associated anticyclonic horizontal circulation in the bay head are mainly driven by negative wind stress curl. The effects of river discharge, surface heat fluxes, and tides are found to be small. Under strong wind events, the wind stress curl over the bay head can be large enough to make the surface Ekman layer strongly nonlinear. Theoretical and numerical analyses show that, under large negative wind stress curl, the nonlinearity tends to induce positive pumping velocity (at the base of the surface mixed layer) that counteracts the Ekman pumping
however, the typical duration of wind events in the bay head is not long enough to induce positive pumping under negative wind stress curl. These results and historical wind data suggest that the average horizontal circulation and residual circulation immediately below the surface mixed layer in Tokyo Bay are, respectively, cyclonic and convergent in summer but anticyclonic and divergent in winter. © 2014. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013JC009396

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

Two oceanographic Radars targeting tsunamis had been installed in Wakayama Prefecture in Japan. To study observation capabilities of the radars on far field and near field tsunamis, numerical experiments were carried out. After starting the operation of the radars, nine earthquakes occurred in the observation area, however, they were too small to be observed by the radars. Parameter study on near field tsunamis showed the radars can observe earthquake of Mw 7 and very shallow Mw 6. As a far field tsunami, the 2012 Haida Gweii Earthquake Tsunami arrived at Japan, however, the radars could not detect it because of very small velocity. Parameter study on far field tsunamis showed the main energy of tsunamis off Canada propagates northward, and Oshika Peninsula is suitable to observe the tsunamis.

DOI： 10.2208/kaigan.70.I_356

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Other Link： http://hdl.handle.net/10112/8854

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The exponential decay of the amount of new litter on Wadahama Beach, Nii-jima Island, Japan revealed by 20-month mark-recapture experiments demonstrates a linear response of the beach to the input of target items. Here we show the amplitude and phase characteristics of the beach as a time-invariant linear input/output system and discuss the hydrodynamic and geomorphological factors that would determine the characteristics with the aid of a diffusion equation. The characteristics are fully determined by the residence time of the items (tau(r) = 209 days) and can be described as functions of the ratio of tau(r) to the period of input variability. The decay is reproduced well by the analytical solution of the equation with a constant diffusion coefficient (D), whose order was estimated by tau(r) and the backshore width. Generally, D would depend on hydrodynamical statistics and beach geomorphology as well as the dimensions and density of the items. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2013.09.049

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

We numerically estimated the inflow flux of terrestrial grass, which is the main floating macro-debris, into Tokyo Bay from April 2008 to March 2009 based on a two-way particle-tracking model and an inverse method applying a Lagrange multiplier. In the estimation, we used surface current velocities derived by high-frequency ocean radar and the quantity of grass collected by clean-up vessels which are operated daily in the bay. At least 2115 m(3) yr(-1) of the grass flowed into the bay annually, and the contribution of a flood event to the inflow flux of grass was larger than that of the inflow flux of freshwater. We show that 39% of the annual inflow flux of grass into the bay was collected, and 61% flowed out of the bay or sank to the seabed. The numerical estimation in this study will be useful to establish a system for predicting patches of floating macro-debris in the bay, and to evaluate the effects of river development or clean-up along river banks and flood plains in the upper reaches. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ecss.2013.09.005

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DOI： 10.2208/kaigan.69.I_436

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DOI： 10.2208/jscejhe.69.I_769

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We have developed a technique for detecting the pixels of colored macro plastic debris (plastic pixels) using photographs taken by a webcam installed on Sodenohama beach, Tobishima Island, japan. The technique involves generating color references using a uniform color space (CIELUV) to detect plastic pixels and removing misdetected pixels by applying a composite image method. This technique demonstrated superior performance in terms of detecting plastic pixels of various colors compared to the previous method which used the lightness values in the CIELUV color space. We also obtained a 10-month time series of the quantity of plastic debris by combining a projective transformation with this technique. By sequential monitoring of plastic debris quantity using webcams, it is possible to clean up beaches systematically, to clarify the transportation processes of plastic debris in oceans and coastal seas and to estimate accumulation rates on beaches. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2012.06.006

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As a first step toward understanding the marine litter balance in Tokyo Bay, we confirmed the applicability and accuracy of the two-way particle-tracking model (PTM) and the inverse method using a Lagrange multiplier developed by Isobe et al. (2009) and Kako et al. (2010) for the East China Sea using high-frequency ocean surface radar-derived surface current velocities and a drifting litter collection database managed by the Ministry of Land, Infrastructure, Transport and Tourism. We focused on how the accuracy of these methods depends on horizontal diffusivity (HD). We found that the two-way PTM and the inverse method are applicable to Tokyo Bay: the errors of identifying marine litter sources by the two-way PTM are within 10 km, and the estimating marine litter inflows are 0.9 to 1.6 times the true inflows. The errors of identifying the sources depend on the HD: the possibility of incorrect identification by the two-way PTM increases with larger HD. In addition, the errors depend on the strengths of the horizontal dispersion field produced by horizontal velocity shear. The possibility is also high for current fields with strong horizontal velocity shear. Also, when the HDs are larger than the corresponding true HDs, the inflows are overestimated. However, the dependence of the estimation on HD is not linear: if the HDs are larger than twice the true diffusivities, estimated inflows are less than twice the true inflows. Even if the HDs are one order of magnitude greater than the true diffusivities, the estimated inflows are smaller than six to seven times the true inflows.

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10578331

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DOI： 10.2208/kaigan.68.I_196

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DOI： 10.2208/kaigan.68.I_1471

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

Signals from the tsunami waves induced by the March 11, 2011 moment magnitude (M-w) 9.0 Tohoku-Oki earthquake and from subsequent resonances were detected as radial velocity variability by a high-frequency ocean surface radar (HF radar) installed on the eastern coast of the Kii Channel, at a range of about 1000 km from the epicenter along the eastern to southern coasts of Honshu Island. A time-distance diagram of band-passed (9-200 min) radial velocity along the beam reveals that the tsunami waves propagated from the continental shelf slope to the inner channel as progressive waves for the first three waves, and then natural oscillations were excited by the waves; and that the direction of the tsunami wave propagation and the axis of the natural oscillations differed from that of the radar beam. In addition, spectral analyses of the radial velocities and sea surface heights obtained in the channel and on the continental shelf slope suggest complex natural oscillation modes excited by the tsunami waves.
The major advantage of the HF radars as tsunami detection is early warning as the tsunami is still far offshore. There is no doubt on this importance beside still technical and operational studies are needed. Our results adds a new role of the HF radars to measure the detailed surface current fields with high spatiotemporal resolution toward understanding detailed processes of resonant response to tsunami waves in coastal regions. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ecss.2011.08.009

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This study attempts to establish a system for hindcasting/forecasting the quantity of litter reaching a beach using an ocean circulation model, a two-way particle tracking model (PTM) to find litter sources, and an inverse method to compute litter outflows at each source. Twelve actual beach survey results, and satellite and forecasted wind data were also used. The quantity of beach litter was hindcasted/forecasted using a forward in-time PTM with the surface currents computed in the ocean circulation model driven by satellite-derived/forecasted wind data. Outflows obtained using the inverse method was given for each source in the model. The time series of the hindcasted/forecasted quantity of beach litter were found consistent with the quantity of beach litter determined from sequential webcam images of the actual beach. The accuracy of the model, however, is reduced drastically by intense winds such as typhoons which disturb drifting litter motion. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2010.10.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER METEOROLOGICAL SOC  

The dependence of wind-driven current (WDC) on wind stress direction in a small semienclosed, homogeneous rotating basin is investigated using a linear steady-state analytical model based on Ekman solutions. The model is applicable to the middle of the basin (midbasin), and the current is driven by a constant wind stress of an arbitrary direction. The WDC is made up of wind stress-driven current (WSDC) and pressure-driven current (PDC) components. The laterally varying water depth of the basin confines the total volume transport in the longitudinal direction while the wind stress-driven volume transport changes direction according to the wind stress direction. Therefore, the pressure-driven volume transport or, equivalent, the pressure gradient depends on the wind stress direction: the relationship between the pressure gradient and the wind stress is anisotropic. As a result, the midbasin WDC is also dependent on the wind stress direction. The dependence varies according to the lateral position and Ekman number E. For large E (small rotation), the longitudinal volume transport is generally proportional to the longitudinal wind stress component. Hence, the ratio of the volume transport driven by the wind stress of direction theta (theta &gt; 0) to that driven by the longitudinal wind stress (theta = 0) becomes cos theta. For small E (large rotation), the ratio becomes larger than cos theta. The extent to which each component of wind stress contributes to the generation of the pressure gradient to satisfy no-net-longitudinal and no-lateral transports is determined by a wind stress-pressure gradient transformation matrix, whose components depend on the lateral position and E.

DOI： 10.1175/2010JPO4363.1

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Language：Japanese   Publishing type：Research paper (other academic)   Publisher：日本海洋学会  

有明海湾奥の循環流の実体を明らかにするために,海底設置型ADCPによる流速連続観測を行なった。得られたデータから残差流成分を抽出し,上層残差流の変動の原因を推定するため,潮汐,河川流量,風を独立変数とする重回帰分析を行なった。その検証を数値モデルにより行ない,さらに,湾奥全域の残差流場がどのように変動しているかを考察した。その結果,冬季における太良町沖の上居残差流は,長軸方向については潮汐の変動の影響を,短軸方向成分については風の変動の影響を,強く受けることが示された。また,小長井町沖の残差流は,成層期には風の変動の影響を強く受けることが示された。さらに,潮汐・河川流量・風の変動が湾奥全域の残差流に及ぼす影響を数値モデルによって解析した。その結果,大潮時には地形に対応した水平循環,小潮時にはエスチャリー循環のパターンが卓越することが明らかになった。また,河川の変動による影響は成層期にのみ見られた。さらにまた,風による影響は季節によって異なるが,その原因は風の変動の大きさが変わったことによるだけではなく,残差流の応答特性自体が変化していることにもよっており,同じ風の変動を与えても引き起こされる残差流は季節によって異なったものとなることも解明された。

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：COASTAL EDUCATION & RESEARCH FOUNDATION  

Trans-boundary pollution is carried by currents and other flows. Litter from river basins flow into the sea, and currents and winds spread them along the coast. In Japan, many citizen groups, community based organizations, fishermen, divers, national and local governments, CBO and an international NGO have continued to clean up beaches, riverbanks and the sea bottom for some decades. Most of these activities are voluntary, but the costs accrued by local governments progressively multiplied. Beach and river litter have become serious social problems. Therefore, scientific and systematic countermeasures, multi-sectoral collaboration and international collaboration are essential.

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

The mechanism of a characteristic sea level response (barotropic coastal ocean response) to wind field fluctuation around the tip of the Izu Peninsula observed during the middle of December 2000 to the middle of January 2001 was investigated based on three types of numerical experiments using the Princeton Ocean Model with various parameters. The response was characterized by the relaxation of sea level falling (rising) during eastward upwelling (westward downwelling) favorable wind regime. Analyses of quasi-realistic numerical model results in terms of the vertically integrated momentum balances and vorticity balance for the barotropic mode revealed that: 1) development/abatement of two anomalous circulations generated around the tip of the Izu Peninsula controls the sea level response through the acceleration/deceleration of a quasi-geostrophic barotropic coastal current between the circulations; 2) nonlinear vorticity advection by the Kuroshio Current and by the coastal current, coupled with vorticity diffusion, decelerates the quasi - geostrophic coastal current in the latter half of the wind regimes, which induces the relaxation of sea level rise/fall. The results of the quasi-realistic numerical experiment suggest that an analysis of the vorticity balance for the barotropic mode contributes to a better understanding of sea level responses to wind in coastal regions with strong currents and complex topography. In addition, a numerical experiment with idealized spatially uniform density stratification and a quasi-realistic wind field shows that if the Kuroshio Current had been shifted far offshore from the Izu Peninsula during the observation period, westward propagating continental shelf waves would have controlled the coastal sea level response.

DOI： 10.1007/s10872-008-0051-z

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Language：Japanese  

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Other Link： http://id.nii.ac.jp/1141/00046590/

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

The Kyushu Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism has placed four High-Frequency Oceanic Radar (HF radar) at the Ariake Sea since 2005. The system named "The Ariake Sea current and ocean wave information system" provides the real-time information on surface currents and waves on the Internet.<BR>This paper presents the results of the comprehensive investigations on (1) the accuracy of HF radar observation, (2) the expansion of the current observation area, and (3) the improvement of the ocean wave observation. These inclusive studies come to the conclusions that the accuracy of ocean radar was verified satisfactory, and the expected improvements of the system for measuring currents as well as waves were successfully achieved.

DOI： 10.2208/prooe.24.849

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

The Kyushu Regional Development Bureau, Ministry of Land, Infrastructure and Transport has placed four High-Frequency Oceanic Radar System (HF radar) at the Ariake Sea with the aim of regenerating environmental condition, and has observed the surface current and ocean wave situations since 2005.<BR>The paper presents (1) the result of study for precision of HF radar observation, (2) the real-time informing system by internet named "The Ariake Sea current and ocean waves information system", and (3) the development of "The sea garbage movement prediction system" utilized the surface current observation information by the system with the aims of the improving the sea garbage collecting service by the Advanced Anti-Pollution Vessel "KAIKI" as well as the progress of the installing the system. As result of the development, the precision is verified appropriately, and the system has been operated since April, 2007.

DOI： 10.2208/prooe.23.709

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer Netherlands  

This study demonstrates the existence of an ecological network of short-necked clam larvae in Tokyo Bay. It also shows that the whole Tokyo Bay ecosystem may be improved if suitable spawning grounds, even if they are small, are conserved and restored. Thus, our strategy for zoning the primary implementation area in the Tokyo Bay Restoration Plan is justified. It should be noted that this paper has only introduced the fate of pelagic larvae in one spawning case. Further observations and numerical studies will be needed to clarify how the advection of pelagic larvae contributes to the reproduction of shortnecked clams. It will also be necessary to study how pelagic short-necked clam larvae respond to factors such as water temperature and salinity, the temporal variation of their specific gravity, and to add these results in the pelagic shortnecked clam larvae model. Beside this uncertainty, inherent in any ecosystem model, this study demonstrates the importance of an ecological network in Tokyo Bay. © 2006 Springer.

DOI： 10.1007/1-4020-3655-8_3

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer Netherlands  

In Tokyo Bay (Figure 1), the river discharge into the head of the bay gives rise to horizontal density gradients that lead to an estuarine circulation (Nakayama, 2005) as shown in chapter of "Circulation Phenomena in Tokyo Bay". If the oceanic water, i.e. the Kuroshio warm water, approaching to the bay and it is denser than the bay bottom water, then a classical estuarine circulation prevails whereby there is an outflow of bay waters at the surface and an inflow of oceanic water in the lower layer. However, fluctuations of the circulations in the bay can occur on time scales ranging from a few days to a few months due to the effects of climate and/or Kuroshio current fluctuations in the time scales. As a result, the depth at which oceanic water intrudes is also though to vary with oceanic and climate conditions. Yanagi et al. (1989) measured the water quality at the mouth of Tokyo Bay. They suggested that a three-layer circulation may exists whereby the Kuroshio water flows into the middle layer of the bay where the water density is the same, while highly turbid water flows out from the bay in the surface layer and lower layer. If this hypothesis is correct, then the inflow of oceanic water into the middle layer should have a significant effect on the behavior of the hypoxic water mass that develops in the lower layer of the bay during the summer. In September 1998, the intrusion of oceanic water into the middle layer of Tokyo Bay occurred intermittently. At this time, Hinata et al. (2001) used ADCP (Acoustic Doppler Current Profiler) observations and water quality observations to take direct measurements of the flow structures inside the bay and the heat/material flux between the bay and ocean. This chapter revisits the observations of Hinata et al. (2001) to describe the three-dimensional flow structures inside the bay and the heat and material flux between the bay and ocean that occur when oceanic water intrudes into the middle layer inside the bay during the summer. (figure presented).

DOI： 10.1007/1-4020-3655-8_5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The mechanisms of the periodic Kuroshio warm water intrusion (KWWI) into Sagami Bay through the Oshima West Channel (OWC) and the fluctuation of the current field in the bay were investigated using high-frequency oceanic radar observation data, satellite imagery, and meteorological data. During the period from 15 December 2000 to 16 January 2001 the Kuroshio took a nonlarge meander path, looping south around the Kii Peninsula and then turning sharply north toward the Izu Peninsula (IP). Kuroshio warm water (KWW) then flowed into Sagami Bay periodically through the OWC on a synoptic timescale of 8-11 days. Statistical analysis of the data indicated that the occurrence of the KWWI and the variability in the Kuroshio front were highly coherent with wind velocity field fluctuations corresponding to the passage of cyclones across northern Japan. When southward to southwestward winds dominated in and around Sagami Bay, the Kuroshio front approached the southern coast of the IP, and then the KWW strongly intruded into the bay through the OWC. When eastward to northeastward winds prevailed, the front moved offshore about 10-20 km, ending the KWWI. The distances of the Kuroshio front movements were consistent with the internal radius of the deformation estimated from conductivity-temperature-depth data collected off the IP, suggesting that the Kuroshio front movement was induced by the onshore-offshore surface Ekman transport associated with the wind velocity field regime shift corresponding to the passage of cyclones. In addition, examination of the vorticity dynamics in the northern part of the bay based on radar-derived surface current data indicated that the cyclonic circulation generated in the bay was enhanced due to the transport of the positive relative vorticity by the KWWI plus the horizontal convergence accompanied by the stretching of the vorticity.

DOI： 10.1029/2004JC002300

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Language：Japanese  

HF radar and Acoustic Doppler Current Profiler (ADCP) observations are made to measure the horizontal distribution of the M2 tidal current in Tokyo Bay. In order to clarify the accuracy of the HF radar-derived M2 tidal current, we compare the harmonic constants from the HF radars with those from the ADCPs at four stations. The comparison reveals that the accuracy strongly depends on the azimuthal difference in the radar beams and the distance from the HF radars due to the observational errors in the azimuthal direction. The M2 tidal current ellipse from the four HF radars are consistent with those from the ADCPs, indicating that at least four HF radars are required to monitor the M2 tidal current field in the bay. From the results from four HF radars, the phase of the M2 tidal current in the bay is generally between 60-70 degrees, while the phase proceeds at 20-40 degrees off Futtsu Point. In contrast with the previous studies, the phase in the eastern region does not proceed compared to the western region.

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10578082

Language：Japanese  

The majority of the benthos are pelagic in their larval stages. The short-necked clam, Ruditapes philippinarum, which is widely distributed on sandy tidal flats across Japan and is a commercially important shellfish, has a planktonic larval stage, which lasts 2 to 3 weeks after hatching. In this stage, most clam larvae are able to disperse over wide areas with the currents and then settle on new habitats on other shores. In the case of Tokyo Bay, reclamation of the tidal flats and shallows has brought a marked decrease in the harvest of the clam. To recover the clam populations on the shores of Tokyo Bay, the creation of suitable habitats for the clam and the preservation of their environment are very important. We also need to understand how local populations of the clam are maintained through wide dispersal ranges over tidal flats during the larval stages. In this paper, we show the dynamics of larval dispersal of the clam in Tokyo Bay introducing the results of field plankton surveys conducted by the National Institute for Land and Infrastructure Management Ministry of Land and the National Research Institute of Fisheries and Environment of Inland Sea in 2001. The spatial distribution of the larval abundance of the clam was investigated at 65 stations along the entire range of Tokyo Bay on August 2, 6, 10 and October 15, 19, 23, in 2001. Identification of the larvae of the clam was performed using the monoclonal antibody technique. A large number of small D-shaped larvae were found shortly after hatching in the sea waters around the Banzu, Futtu, and Sanmaizu-Haneda in August and the Sanbanze, Sanmaizu-Haneda, and Kanazawa areas in October indicating that spawning populations in these areas probably contributed greatly to the larval supply in the bay. Moreover, the smallest size larvae also occurred abundantly around the Yokohama and Chiba port areas, suggesting that these port regions may play an important role in the transport of larvae into Tokyo Bay.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Variability in water-exchange time between Tokyo Bay and the Pacific Ocean during winter is investigated based on the results of intensive field observation from November 2000 to March 2001. Water-exchange time between Tokyo Bay and the Pacific Ocean during winter mainly depends on the strength of northerly monsoon, being about 16 days under the weak monsoon and about 12 days under the strong monsoon. Moreover, it becomes longer by about I day in spring tide and shorter in neap tide due to the coupling effect of estuarine circulation and vertical mixing. Water-exchange time also varies depending on the open-ocean condition. When the warm water mass approaches from the Pacific Ocean to the mouth of Tokyo Bay through the eastern channel of Sagami Bay, which connects Tokyo Bay and the Pacific Ocean, water-exchange time becomes longer by about 2 days because the warm water mass is blocked in the surface layer at the bay mouth. On the other hand, when the warm water mass approaches to the mouth of Tokyo Bay through the western channel of Sagami Bay, water-exchange time becomes shorter by about I day because the warm water mass intrudes into the middle or lower layers of Tokyo Bay. Such different behavior of warm water mass at the mouth of Tokyo Bay is due to the difference in density of approaching warm water masses, that is, the density of the warm water mass through the eastern channel is smaller than that of the warm water mass through the western channel of Sagami Bay.

DOI： 10.1007/s10236-003-0055-6

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

発行月不明

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Other Link： http://agriknowledge.affrc.go.jp/RN/2010701535

Language：Japanese   Publisher：生物研究社  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Oceanographic Society of Japan  

Near-surface current measurements by two high-frequency oceanic surface radars of the Frequency Modulated Interrupted Continuous Wave (FMICW) type were carried out during December 2000-March 2001 in order to investigate the characteristics of short-period fluctuations of surface circulation in Sagami Bay induced by Kuroshio wann water (KWW) intrusions. When the KWW intrudes into the bay through Ooshima west channel (OWC), cyclonic and anti-cyclonic circulations are generated in the central part of the bay and in the lee of Ooshima Island, respectively, as suggested by previous studies based on mooring and drifting buoy observations (e.g. Taira and Teramoto, 1986; Iwata and Malsuyama, 1989). These two circulations fluctuate with periods of about 811 days. When the KWW strongly intrudes into the bay from OWC, cyclonic and anti-cyclonic circulations become large and the centers of the circulations move south west ward and northeastward, respectively. In addition, warm water intrudes into the mouth of Tokyo Bay and a coastal front appears at the bay month. Statistical analyses, including standard Empirical Orthogonal Function (EOF) analysis, and satellite infrared images of the Knroshio indicate that the dominant fluctuation of the circulation is caused by temporal change in strength of the KWW intrusion due to small-scale (10-15 km) offshore-inshore movement of the Kuroshio front. This movement is thought to, be due to the Ekman transport induced by a southwestward-northeastward wind.

DOI： 10.5928/kaiyou.12.167

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

DOI： 10.2208/jscej.2001.684_93

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

Field measurements were performed to investigate the effects of Kuroshio Warm Water Intrusion (KWWI) to the mouth of Tokyo Bay on the three dimensional characteristics of currents and material transport in the bay mouth in winter. When KWWI occurs, the bay water with low temperature and low salinity flows toward the ocean in the surface layer, the Kuroshio Warm water with high temperature and high salinity intrudes into the bay in the intermediate layer and the coastal water with low temperature and high salinity flows toward the ocean in the bottom layer. The depth of the KWW intrusions into the bay depends on its density relative to the vertical density profile at the bay. The KWWI transports heat into the bay effectively which is five times as large as the winter-averaged heat flux.

DOI： 10.2208/jscej.2000.656_221

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/proce1989.45.986

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/proce1989.45.416

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DOI： 10.2208/proce1989.45.421

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DOI： 10.2208/proce1989.44.1076

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DOI： 10.2208/proce1989.44.401

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DOI： 10.2208/proce1989.44.456

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/proce1989.43.406

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/proce1989.43.391

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

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DOI： 10.2208/proce1989.42.1226

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：国土技術政策総合研究所  

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J-GLOBAL

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Language：Japanese   Publisher：国土技術政策総合研究所  

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A brief description of previous research projects with respect to beach-litter issues is given in this review. In addition, we introduce our research project, which establishes a beach-litter monitoring system using webcams, and which develops an inverse method to identify litter sources. Also proposed in this review is an effective beach-litter clearance procedure, and possible contributions of oceanographers on the beach-litter issue.

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Other Link： http://id.nii.ac.jp/1141/00048007/

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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J-GLOBAL

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/proce1989.47.426

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To understand the fundamental and overall characteristics of thermal environment in coastal areas, a comparative analysis based on a set of long-term data of water temperature variation has been performed for the Tokyo Bay (semi-closed bay), the Kashima coast (open coast) and the Kasumigaura (lake), which are located under similar weather conditions. The results show that, all through the year, the water temperature variation in the Kasumigaura is governed by the heat flux through the water surface such as solar radiation, whereas that in the Kashima coast is dominated also by the horizontal convection. In Tokyo Bay, in summer, the water temperature variation in the surface mixing layer in the time scale more than one week is mostly governed by the vertical heat flux through the water surface. Since the heat is accumulated in the surface mixing layer and its average depth is comparable to that of the Kasumigaura, the subsurface water temperature in the Tokyo Bay exhibits nearly the same variation with that in the Kasumigaura. In winter, on the other hand, the horizontal heat flux through the baymouth from the Pacific Ocean influences the water temperature even at the head of Tokyo Bay.

DOI： 10.2208/jscej.2000.656_239

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Publisher：土木学会  

DOI： 10.2208/proce1989.47.396

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DOI： 10.2208/jscej.2000.642_87

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Language：Japanese   Publisher：東京工業大学工学部土木工学科  

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/proce1989.46.1001

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DOI： 10.2208/proce1989.46.396

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DOI： 10.2208/proce1989.46.451

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J-GLOBAL

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© 2016 IEICE. A tsunami generated by 'The 2011 off the Pacific coast of Tohoku Earthquake' was observed by two high frequency ocean surface radars (HF radars) and four tide gauges installed on Ise Bay. The tsunami wave arrived initially at 16:50 was observed by tide gauge which is installed on the mouth of the Bay. This wave propagation was also observed by HF radars installed on the inner part of the Bay. Therefore, these observations were considered to be correlated. The result of spectral analysis, the tsunami wave had energy with period bands of 120-140, 60-90 and 30-40 min. In comparison to the previous study suggest that these 60-90 and 30-40 min periods oscillations were attributed to the tsunami source fault.

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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

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

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Language：English   Presentation type：Oral presentation (general)  

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To investigate the characteristics of flow field in the coastal buffer zone (C.B.Z.), velocity measurements in a field were performed both in non-stratified and stratified conditions. The results of the data analysis have shown that in the non-stratified condition wind action, together with tidal motion, may induce unexpectedly large velocity even near the bottom with the magnitude beyond the threshold of the sediment movement, suggesting that the appreciable sediment transport may be caused by these wind-driven currents in C.B.Z.. In the stratified condition, it is revealed that internal tides with baroclinic velocity fluctuation may dominate the cross-shore exchanging motion of water mass.

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Author：Other 

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Author：Other 

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Author：Other 

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Author：Other 

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