Details of a Researcher

Optical Characterization of Coastal Waters with Atmospheric Correction Errors: Insights from SGLI and AERONET-OC

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

Higa, H; Muto, M; Salem, SI; Kobayashi, H; Ishizaka, J; Ogata, K; Toratani, M; Takahashi, K; Maupin … Show more authors

REMOTE SENSING 16 ( 19 ) 2024.10

Observations of water optical properties during red tide outbreaks off southeast Hokkaido by GCOM-C/SGLI: implications for the development of red tide algorithms

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

Siswanto, E; Luang-on, J; Ogata, K; Higa, H; Toratani, M

REMOTE SENSING LETTERS 15 ( 2 ) 121 - 132 2024.2

STUDY OF THE INTERACTION BETWEEN SOIL WATER CONTENT AND GROUND ELEVATION CHANGES IN THE SWASH ZONE

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

OHKAWARA Tomoya, SUZUKI Takayuki, HAYASHI Tomoki, BANNO Masayuki, HIGA Hiroto

Japanese Journal of JSCE 80 ( 17 ) n/a 2024

FIELD SURVEY OF WAVE-INDUCED PRESSURE FLUCTUATIONS IN THE SANDBAR LAYERS

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

The swash zone experiences constant changes in wave conditions due to tidal changes and the wave run-up and backwash, leading to fluctuations in soil water content. Therefore, the purpose of this study is to elucidate the interactions between soil water content and elevation changes that occur along with these wave conditions. Field surveys were conducted in the swash zone to measure soil water content and ground elevation change using a laser distance meter at the same location, and the relationship between the two was investigated. The results showed that soil water content varied periodically in response to tidal level and wave run-up. Furthermore, each period of soil water content change was divided into time interval, and the relationship with ground elevation change was examined for each interval. It was found that during the rapid increase in soil water content during flood tide, sediment deposition increased with shorter durations of the period, and during the soil water content stabilization at high level around high tide, sediment deposition increased with longer durations of the period.

KATO Yusuke, SUZUKI Takayuki, ISLAM Md Shofiqul, HIGA Hiroto

Japanese Journal of JSCE 80 ( 17 ) n/a 2024

ASSESSMENT OF REGIONAL CHARACTERISTICS FOR COASTAL DISASTER PREVENTION INFRASTRUCTURE CONSIDERING WELL-BEING AND ECOSYSTEMS IN JAPANESE COASTAL AREAS

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

In this study, pore water pressure in the coastal sandbar layers was measured alongside waves and sandbar profile changes to explore the correlation between sandbar profile change and fluctuation in pore water pressure. In this analysis, negligible changes in sandbar profiles were compared with erosion phases, and accretion phases. The results indicate that pore water pressure fluctuations in the sandbar decayed more rapidly with increasing depth during erosion and accretion phases compared to the phases with almost negligible change. Additionally, a comparison between the vertical pressure gradient and wave steepness revealed that the pressure gradient tended to fluctuate significantly when wave steepness ranged between 0.02 to 0.04 during erosion and accretion phases. During erosion and accretion phases, the fluctuations in the vertical pressure gradient were dominated by upward pressure propagation, suggesting a possible loosening of compaction within the sand layer.

KOBAYASHI Kohtaroh, HIGA Hiroto, SUZUKI Takayuki, MÄLL Martin

Japanese Journal of JSCE 80 ( 17 ) n/a 2024

DYNAMIC TRIAL MEASUREMENTS OF DENSITY CHANGES IN SAND LAYERS USING AN X-RAY CT

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

This study developed a framework for infrastructure assessment, including green infrastructure (GI) and gray infrastructure (GyI), and examined the impact of coastal infrastructure on humans and nature. The results of the survey showed that the well-being was related to the size of the hazard, and the smaller the hazard, the higher the level of satisfaction. The results also indicated that there is a limit to the level of satisfaction that can be obtained through urbanization, and that GI ecosystem services may lead to higher levels of satisfaction. The results of this study suggest the importance of considering the balance between GI and GyI in terms of both well-being and natural demand.

NISHIURA Tomonori, SUZUKI Takayuki, KIKUMOTO Mamoru, MATSUMURA Satoshi, BANNO Masayuki, HIGA Hiroto

Japanese Journal of JSCE 80 ( 17 ) n/a 2024

INVESTIGATING MEGA-CUSP SHAPE EXTRACTION THROUGH AERIAL PHOTOS AND OBJECT DETECTION ALGORITHMS

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

The porosity in the surf zone’s sand layer is known to exhibit variations. However, there are few studies on this, and existing models of sediment transport and topography change do not take into account the spatio-temporal variation of porosity in the sand layer. In this study, experiments were conducted using a tabletop wave generator. Regular waves were generated on the constructed sand slope, and images of the sand layer were taken by an X-ray CT system to measure the spatio-temporal variation of porosity under conditions where the topography was going through constant changes. The recorded images were analyzed to investigate the relationship between the topographic change and the porosity change in the sand layer. As a result, it was confirmed that there were layers with large porosity at the surface during topographic change in both accretion and erosion areas. The thickness of the layers (i.e. with large porosity) were about 4 mm in the accretion area and about 2 mm in the erosion area. The differences in thickness were due to loose sediment deposition and surface scraping in the accretion area and erosion area, respectively, leading to a twofold increase in the former.

HAYUNINGSIH Annisa Farida, SUZUKI Takayuki, MÄLL Martin, BANNO Masayuki, HIGA Hiroto

Journal of JSCE 12 ( 2 ) n/a 2024

Spectral band-shifting of multispectral remote-sensing reflectance products: Insights for matchup and cross-mission consistency assessments

Language：English Publishing type：Research paper (scientific journal) Publisher：公益社団法人土木学会 Joint Work

Mega cusps are critical for risk management due to their connection with rip currents and erosion in the swash zone. This study aims to explore the effectiveness of aerial photos and object detection algorithms in capturing mega cusp shapes, focusing on both edge-based and object-based methods. The research area focused on the Hasaki Coast in Kamisu City, Ibaraki Prefecture, and data were gathered from aerial photos and topographic data sources on June 6th, 2023. Four algorithms—Random Forest, Otsu's, Canny Edge, and Laplacian detection—were utilized to detect mega cusp shapes, extending their use beyond identifying sharp edges of objects such as buildings and roads to extracting smooth features that represent mega cusp shape lines. The Random Forest algorithm closely aligns with topographic data, detecting the mega cusp shape extraction in the area between wet and dry sand after classifying sand pixel colors. Meanwhile, the Otsu’s, Canny Edge, and Laplacian algorithms focus on the sand berm object, which has edges. Edge-based algorithms, such as Canny Edge and Laplacian, concentrate on the top edge of the sand berm, whereas Otsu’s algorithm focuses on the base of the berm sand. Elevation data extracted through Digital Terrain Models (DTM) and GIS tools highlight the importance of detailed examination for understanding mega cusp shape elevations. The Random Forest algorithm provides an average elevation of 1.26 m, similar to the high tide level, with 0.01 standard error of elevation, while Otsu’s, Canny Edge, and Laplacian algorithms yield higher elevations ranging from 2.03 m, 2.25 m, and 2.20 m, respectively, with a larger standard error of position. In conclusion, the study recommends the Random Forest algorithm, a machine learning-based approach, emphasizing its ability to detect the mega cusp object using a training dataset during a neap tide.

Salem, SI; Higa, H; Ishizaka, J; Pahlevan, N; Oki, K

REMOTE SENSING OF ENVIRONMENT 299 2023.12

GLORIA-A globally representative hyperspectral in situ dataset for optical sensing of water quality

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

Lehmann Moritz K., Gurlin Daniela, Pahlevan Nima, Alikas Krista, Anstee Janet, Balasubramanian Sund … Show more authors

SCIENTIFIC DATA 10 ( 1 ) 2023.2

DOI Web of Science PubMed

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

AN EXPERIMENTAL STUDY ON SEDIMENT TRANSPORT OF MIXED SAND NOURISHMENT

MIYAJIMA Tatsuya, SUZUKI Takayuki, HIGA Hiroto

Japanese Journal of JSCE 79 ( 17 ) n/a 2023

FIELD OBSERVATIONS AND ECOLOGICAL MODEL ANALYSIS OF SULFIDE, IRON, AND MANGANESE CIRCULATION BETWEEN WATER AND SEDIMENT IN TOKYO BAY

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

Beach nourishment, which serves as a measure to control beach erosion, has been implemented on numerous beaches. Laboratory experiments have been conducted to study the particle size, location, and structure of beach nourishment. However, further investigation is still needed to understand the sediment transport characteristics of beach nourishment with different mixing ratios. In this study, we conducted laboratory experiments using nourishment beaches formed on a fixed-bed slope with varying mixing ratios. In this study, we conducted laboratory experiments using nourishment beaches formed on a fixed-bed slope with different mixing ratios to clarify the sediment transport characteristics of mixed sand nourishment beaches and compared the results with those of single sand nourishments. The results showed that even when the median particle size of the beach is similar, the discharge of fine-grained sand is suppressed when the median particle size is small and coarse-grained sand is included in a mixed-sand beach, while coarsegrained sand tends to migrate when the median particle size is large and fine-grained sand is included in a mixed-sand beach. Therefore, it is necessary to consider not only the median particle size of beach materials but also the entire grain size distribution, including coarse and fine grain size, when selecting beach materials and studying sediment transport.

HIGA Hiroto, NAKAMURA Satomi, HAYASHI Kohaki, OKADA Teruhisa, INOUE Tetsunori, NAKAMURA Yoshiyuki, … Show more authors

Japanese Journal of JSCE 79 ( 17 ) n/a 2023

STUDY ON DATA ASSIMILATION USING SST OF SATELLITE OBSERVATIONS BY RECYCLE GREEN'S FUNCTION APPROACH IN TOKYO BAY

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

In this study, we focused on the circulation of sulfides, iron, and manganese in the enclosed water area of Tokyo Bay. We conducted field observations and numerical analysis using a three-dimensional coupled model of the pelagic and benthic systems. Through load surveys of rivers, we created a quantitative formula for the forms of Fe and Mn in the Arakawa and Tama rivers and calculated the load of each river. Additionally, analysis of water and sediment samples in the bay revealed an increase in P-Fe in the anoxic bottom layer where H2S was present, suggesting that the formation of oxidized iron resulted from the reaction between H2S and Fe2+. On the other hand, D-Mn was found to be highly concentrated due to leaching from the sediment under anoxic conditions (ORP <-200 mV). In the analysis using the three-dimensional coupled model, there are challenges such as overestimation of H2S in sediments and underestimation of D-Mn in the water column. However, the model was able to generally reproduce the vertical distribution of DO, D-Fe, H2S in the water column, and D-Fe, D-Mn in the sediment.

SHINOHARA Yuta, HIGA Hiroto, OKADA Teruhisa, SUZUKI Takayuki

Japanese Journal of JSCE 79 ( 17 ) n/a 2023

ESTIMATING WAVE HEIGHT USING WAVE SOUND FROM AN IC RECORDER AT THE HIRATSUKA COAST, JAPAN

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

In coastal areas, numerical models have been improved in accuracy through data assimilation using water quality measurements and HF radar observations. However, until recently, the limited spatiotemporal resolution of satellite data has hindered its utilization, resulting in few application cases. In recent years, there has been significant improvement in the spatiotemporal resolution of satellite data. Therefore, the use of data assimilation with satellite data is expected to be beneficial for closed water areas. In this study, data assimilation was performed using satellite-observed sea surface temperature (SST) through the reuse of the Green's function method in Tokyo Bay. The aim was to optimize the parameter values related to the heat balance within the numerical model and examine the impact on the reproducibility of water temperature. As a result, the root mean square error (RMSE) between the satellite-observed SST and the calculated water temperature from the numerical model decreased by approximately 26% at maximum, suggesting the effectiveness of satellite data assimilation in coastal areas.

OMATA Yuto, SUZUKI Takayuki, HIGA Hiroto

Japanese Journal of JSCE 79 ( 17 ) n/a 2023

Uncertainty Analysis of Particle Backscattering Coefficient Measurement for Multiple Highly Turbid Water Areas in Ocean Color Remote Sensing

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

Field experiments were conducted at the Hiratsuka coast in Kanagawa prefecture from September 8th to November 7th, 2022, to estimate wave height using wave sound observed by a sound level meter and an IC recorder. The wave sound levels were observed at 55 m landside from the average shoreline position and 11.7 m above the average sea level. Every 10-minute observation (sound level meter, IC recorder, wind speed, wind direction, and air pressure data) was used in the analysis. Wave height can be estimated using the IC recorder as accurately as using the sound level meter (R2 = 0.51), although a slight estimation delay occurs when the observed wave height is high, i.e., approaching a typhoon. However, the observations by the IC recorder included wind noise. Thus, sound pressure corrected based on the windscreen effect made it more accurate to estimate wave height by the IC recorder (R2 = 0.53). Even if the way to reduce wind noise is very simple, the wave height was also sufficiently estimated (R2 = 0.54).

Higa, H; Ideno, R; Salem, SI; Kobayashi, H

SENSORS AND MATERIALS 35 ( 11 ) 3807 - 3828 2023

1D Convolutional Neural Network-based Chlorophyll-a Retrieval Algorithm for Sentinel-2 MultiSpectral Instrument in Various Trophic States

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

Salah, M; Higa, H; Ishizaka, J; Salem, SI

SENSORS AND MATERIALS 35 ( 11 ) 3743 - 3761 2023

An effective process-based modeling approach for predicting hypoxia and blue tide in Tokyo Bay

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

Wang Kangnian, Nakamura Yoshiyuki, Sasaki Jun, Inoue Tetsunori, Higa Hiroto, Suzuki Takayuki, Hafee … Show more authors

COASTAL ENGINEERING JOURNAL 64 ( 3 ) 458 - 476 2022.7

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

A Survey of Case Studies and Recommendations for the Utilization of Satellite Oceanographic Data

SAKUNO Yuji, SAITOH Katsuya, ISHIZAKA Joji, TORATANI Mitsuhiro, HIGA Hiroto, MUKAIDA Akira, TERUI T … Show more authors

Journal of The Remote Sensing Society of Japan 42 ( 2 ) 135 - 142 2022.5

CHARACTERISTICS OF MEGACUSP DEFORMATION AFTER HIGH WAVE EVENTS

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Remote Sensing Society of Japan Joint Work

SUZUKI Takayuki, YASUTA Towa, TABASI Mohammad, HIGA Hiroto

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 78 ( 2 ) I_511 - I_516 2022

AN EXPERIMENTAL STUDY ON THE EFFECTS OF SAND COMPACTION AND SEDIMENT DIAMETERS ON THE TOPOGRAPHY CHANGE OF NOURISHED SAND

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

On sandy beaches, rhythmic features can form near the shoreline, where the characteristics differ from coast to coast. To analyze the dynamics of a large cusp with a wavelength on the order of 100 m, we calculated the cusp wave height (the length from the convex to the concave part of the cusp) from 33 years of ground height measurement data at the Hasaki coast in Ibaraki Prefecture. The relationship between the cusp wave height and wave data was investigated. The results showed that cusp wave heights could be classified into three patterns: increasing, decreasing, and unchanging after high-wave events. Furthermore, these pattern changes were found to be related to the cusp wave height just after the high-wave event. For instance, the cusp wave heights had an increasing trend if the cusp wave height was below 15 m and a decreasing trend for values above that. In addition, the relationship with the wave energy flux of the event was examined. Comparing the increasing and decreasing trends of the cusp wave height, the increasing trend shows larger values for the longshore component of wave energy flux. Although the number of analyzed data is limited, the longshore component of the wave energy flux may influence the fluctuations in the cusp waveheight.

SUZUKI Takayuki, HU Jiayi, YOSHIMURA Natsuki, HIGA Hiroto

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 78 ( 2 ) I_577 - I_582 2022

IMPROVEMENT OF ATMOSPHERIC CORRECTION ALGORITHM FOR OCEAN COLOR REMOTE SENSING CONSIDERING ABSORPTIVE AEROSOLS

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

Beach nourishment has been implemented in many areas as a measure to control coastal erosion, regardless of the presence or absence of coastal structures. Once beach nourishment is conducted, sediments are gradually discharged into the coast due to erosion by waves. However, the contribution of different grain sizes and the degree of compaction of the beach nourished area, to the amount of discharge, has not yet been fully investigated. In this study, laboratory experiments were conducted using three different grain sizes (0.08 mm, 0.32 mm and 0.70 mm) and varying degrees of initial compaction to clarify the effects of these two factors on the topographic change (erosion) of the nourished sand. The results showed that, as a general trend, the smaller the grain size and the looser the compaction, the larger the erosion. Moreover, when the waves did not overtop the nourishment, the erosion rates of the 0.32 and 0.70 mm median grain sizes were almost the same. Whereas the erosion rate for 0.08 mm median grain size was about twice that of 0.32 and 0.70 mm median grain sizes. When waves overtopped the nourishment, the erosion volume increased as the median grain size decreased, though no significant correlation with the sand compaction ratio was observed.

OGURA Yamato, KOBAYASHI Hiroshi, HIGA Hiroto, IRIE Hitoshi

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 78 ( 2 ) I_1039 - I_1044 2022

MODELING UNDERTOW DISTRIBUTIONS UNDER LOW-WAVE CONDITIONS USING XBEACH

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

We investigated the cause of negative Lw, which is a negative value of water-leaving radiance in ocean color remote sensing, using Tokyo Bay as the target sea area. Comparison of SGLI data from the GCOM-C "Shikisai" satellite and optical properties of atmospheric aerosols measured from the ground showed that absorptive aerosols may be responsible. An optical model of absorptive aerosols was developed from the measured optical properties, and radiative transfer simulations were performed. The radiances of aerosols obtained by the aerosol model used in the standard algorithm for atmospheric correction were overestimated compared to those obtained using the absorptive aerosol. This overestimation was assumed to be the cause of the underestimation of water-leaving radiance, and the SGLI data were corrected. Negative values of normalized water-leaving radiance at 380 nm were eliminated, and chlorophyll-a concentrations generally decreased and high concentration regions disappeared. It was shown that the negative Lw could be eliminated by developing an appropriate optical model of atmospheric aerosols.

BORRIBUNNANGKUN Kullachart, SUZUKI Takayuki, MÄLL Martin, HIGA Hiroto

土木学会論文集B3（海洋開発） 78 ( 2 ) I_127 - I_132 2022

A Simple Approach to Predict the Beach Vulnerability to Storm-induced Erosion in Hasaki Coast, Japan

Language：English Publishing type：Research paper (scientific journal) Publisher：公益社団法人土木学会 Joint Work

In nearshore morphodynamic modeling, the simulation of offshore-directed mean current or so-called undertow is necessary for sediment transport as a significant driver. XBeach model is wildly used in predicting storm impacts on natural coasts, yet in regard to morphodynamic predictions, the undertow simulations have been rarely discussed. Recent improvements in the XBeach undertow prediction have been made by modifying the wave roller model. However, despite the improvements for high-wave conditions, the XBeach still performs poorly in predicting undertow under low-wave conditions, where the water depth is a dominant factor controlling undertow current instead of wave mass flux. To improve the XBeach undertow prediction, this paper proposes a modification based on the water depth effect. XBeach performance was tested by comparing two-dimensional simulations with the field observations during low-wave period conditions at Hasaki coast, Japan. Calibration of model coefficients yielded good results for waves, though low accuracy for the simulated undertow. Here, the individual contributions of Stokes drift and Lagrangian velocity (wave forcing term) were respectively modified by including a water depth coefficient. This adjustment caused the undertow’s water depth to be considered from under the wave trough level. The temporal undertow comparisons show a small improvement in the whole period and the accuracy correlates with tidal elevation. When the comparisons of undertow spatial distribution were considered at the different water levels, the undertow results were significantly improved especially at low tide, with an increase in accuracy from bad to fair.

THILAKARATHNE Salika, SUZUKI Takayuki, MÄLL Martin, HIGA Hiroto, MALEK Md Abdul

土木学会論文集Ｂ２（海岸工学） 78 ( 2 ) I_985 - I_990 2022

Performance of JAXA's SGLI standard ocean color products for oceanic to coastal waters: chlorophyll a concentration and light absorption coefficients of colored dissolved organic matter

Language：English Publishing type：Research paper (scientific journal) Publisher：公益社団法人土木学会 Joint Work

While coastal areas hold various social and economic activities, they are highly vulnerable to frequent hazards that cause instabilities to community lives. An index-based approach, established on set criteria, is commonly used to quantify and analyze the vulnerability towards specific hazards. This study aims to assess the performance of a simple linear regression model in predicting storm-induced erosion and to propose a vulnerability assessment tool, a Beach Vulnerability Index (BVI). Hourly wave and water level observations and daily beach profile data from 1993 to 2000 were collected at Hasaki Oceanographic Research Station (HORS), Japan and hourly tidal predictions were also used in the present study. Data-driven linear regression models were trialled on the eight-year data set for predicting storm-induced beach erosion. Shoreline change (dSL) and volume change (dV) were used as the main indicators of beach erosion. Wave energy flux, initial shoreline position, and maximum surge were selected as input variables for the regression models by using a correlation analysis. To quantify the shoreline change vulnerability (VIdSL) and volume change vulnerability (VIdV) to storm-induced erosion, five vulnerability classes were defined based on the first 5 years of shoreline and volume change data. BVIs were then calculated using VIdSL and VIdV in the testing period. During the study period, 48 storms were identified of which the first 38 were used to create two regression models. R2 values of 0.58 and 0.52 were achieved for dSL and dV during the training period and during testing, they were 0.48 and 0.52 respectively. Majority of BVI predictions were slightly over-estimated, for a vulnerability study, this is preferable to having under-estimations. In conclusion, linear regression models provided moderate predictions of beach erosion measurements and adequate predictions of beach vulnerability.

Matsuoka Atsushi, Campbell Janet W., Hooker Stanford B., Steinmetz Francois, Ogata Kazunori, Hirata … Show more authors

JOURNAL OF OCEANOGRAPHY 78 ( 4 ) 187 - 208 2021.10

Current Status and Future Prospects of Satellite Sensors for Ocean Visualization

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

SAKUNO Yuji, SAITOH Katsuya, ISHIZAKA Joji, TORATANI Mitsuhiro, HIGA Hiroto, MUKAIDA Akira, HORI Ma … Show more authors

Journal of The Remote Sensing Society of Japan 41 ( 2 ) 181 - 188 2021.5

REPRODUCTION OF THE SUPPRESSION EFFECT OF IRON ON SULFIDE RELEASE : VERIFICATION OF THE SUPPRESSION EFFECT OF IRON

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Remote Sensing Society of Japan Joint Work

ANALYSIS OF ARCUATULA SENHOUSIA DISTRIBUTION CHRACTERIS-TICS USING UAV AERIAL IMAGES IN THE ARIAKE SEA TIDAL FLAT FISHING GROUND

Hiroto HIGA, Yasushi ICHIMURA, Takashi MIYATSUJI and Takayuki SUZUKI

Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 2021.5 [Reviewed]

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

In this study, we devised a monitoring method for simultaneously estimating elevation, median grain size (D50), and Arcuatula senhousia distribution using Unmanned Aerial Vehicle (UAV) aerial images of tidal flat fisheries in the Konagai sight frontage of Isahaya City, Nagasaki Prefecture. The elevation of the tidal flat was estimated using Agisoft photoscan, and the D50 was estimated based on the reflectance obtained from the aerial images. In the elevation estimation, the bias was about 0.017m, and the D50 was correlated with the reflectance with R2=0.615 (N=9). The detection accuracy of the Arcuatula senhousia distribution was found to be more than 70% at an altitude of 5~20m with 12-megapixel camera and decreased to less than 50% at an altitude of 30m or higher, and more than 60% at an altitude of 40m with 50-megapixel camera and decreased to less than 60% at an altitude of 50m. In addition, by examining the relationship between the estimated spatial distribution of each parameter, we were able to identify the area where Arcuatula senhousia tends to occur.

海色リモートセンシングにおける沿岸域の複雑な光学特性を考慮した合成データ構築法の提案

比嘉紘士, 藤田夏菜子, Salem Ibrahim Salem, 中村由行, 鈴木崇之

土木学会論文集B2(海岸工学) 77 ( 2 ) 2021 [Reviewed]

Language：English Publishing type：Research paper (scientific journal) Publisher：公益社団法人土木学会 Joint Work

本研究では，沿岸域の複雑な光学特性を考慮した海色リモートセンシングのための合成データの構築方法を提案した．合成データの構築にあたり，東京湾で収集した固有光学特性（IOPs），水質の実測値を使用し，放射伝達計算の有効性を確認した．また，階層クラスタリングによりIOPsと水質項目を関連づけて分類し，生物光学モデルに組み込むことで植物プランクトンの種の変遷，陸域と内部生産起源の有色溶存有機物（CDOM）や無機態懸濁物質とデトリタスとの光学特性の違いを表現可能な合成データの構築法を考案した．作成したRrs，IOPsの合成データは，実測値との比較や既存のIOPs推定アルゴリズムへの適用を通して，概ね現実に則した合成データが作成されたことが確認できた．

東京湾奥部における湧昇時連続観測からみた水塊構造に関する考察

林宏樹, 遅乃文, 比嘉紘士, 岡田輝久, 今村正裕

土木学会論文集B2(海岸工学) 77 ( 2 ) 2021 [Reviewed]

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人土木学会 Joint Work

砂の締固めが養浜形状変化に及ぼす影響に関する実験的研究

鈴木崇之, 吉村那月, 比嘉紘士, 中村由行

土木学会論文集B2(海岸工学) 2021 [Reviewed]

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人土木学会 Single Work

RGB 画像を用いた西表島相良川河口域マングローブ林の過去40年間の分布変化の解析と海面上昇による影響

中村航, 中村由行, 藤本潔, 鈴木崇之, 比嘉紘士

土木学会論文集B2(海岸工学) 2021 [Reviewed]

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人土木学会 Joint Work

沿岸部高層建築物や UAV 等を利用した青潮動態のモニタリング

遠藤雅実, 比嘉紘士

日本水環境学会年会講演集 55 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

東京湾における青潮発生時の鉄，マンガン，硫黄の動態に関する研究

CHI NAIWEN, 中村由行, 比嘉紘士, 岡田輝久

日本水環境学会年会講演集 55 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

東京湾における水中物質の構成変化を考慮した海色変化の計算

藤田夏菜子, 比嘉紘士, Salem Ibrahim Salem

日本水環境学会年会講演集 55 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

内湾堆積物における硫化物動態のモデル化と鉄散布による溶出抑制効果の検証

持田史佳, 中村由行, 井上徹教, 比嘉紘士

日本水環境学会年会講演集 55 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

MOCHIDA Fumika, NAKAMURA Yoshiyuki, INOUE Tetsunori, HIGA Hiroto, SUZUKI Takayuki

Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research) 77 ( 7 ) III_241 - III_250 2021

AN EXPERIMENTAL STUDY ON THE EFFECT OF SAND COMPACTION ON THE TOPOGRAPHY CHANGE OF SAND NOURISHMENT

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

In eutrophic waters such as Mikawa Bay, the bottom water becomes anoxic in summer, and sulfide is leached into the bottom water due to sulfate reduction in the sediment surface layer, leading to environmental problems such as blue tide.As a method to improve the bottom sediment environment, the addition of iron materials to the bottom sediment, inspired by the natural phenomenon of iron curtain (removal of hydrogen sulfide by reaction with iron), has been devised, but its quantitative evaluation has not yet been achieved.In this study, we developed a sediment model focusing on the sulfur circulation process to quantitatively evaluate the inhibitory effect of iron addition on sulfide release, and performed reproducible calculations of sulfide elution experiments.In this study, we developed a sediment model focusing on the sulfur cycling process in order to quantitatively evaluate the effect of iron addition to the sediment.

SUZUKI Takayuki, YOSHIMURA Natsuki, HIGA Hiroto, NAKAMURA Yoshiyuki

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 77 ( 2 ) I_589 - I_594 2021

SYNTHETIC DATA GENERATION METHOD FOR OCEAN COLOR REMOTE SENSING CONSIDERING COMLEX OPTICAL PROPERTIES OF COASTAL AREAS

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

Beach nourishments are implemented in many areas for the countermeasure against coastal erosion. Regarding the investigation of beach nourishment, laboratory experiments focusing on the particle size, mixing ratio, and cross-shore location of beach nourishments have been conducted. However, it cannot say that it is sufficient to examine how much the initial compaction degree of nourishment area contributes to the topography changes of the nourished area. Therefore, we conducted laboratory experiments to investigate the effect of the initial compaction of the beach nourishment on the erosion (topographical change) of the nourished area due to waves. The results revealed that the lower degree of compaction of the beach nourishment, the more significant erosion (topographical change) occurred immediately after wave generation, and the difference in erosion rate between the compacted and loose nourished sand was about twice. Moreover, when the wave overtopped the beach nourishment area, the influence of the compaction degree of the nourished area on the erosion volume is smaller than when it does not overtop the nourished area. On the other hand, when the waves did not overtop the beach nourishment area, it was found that even if the topography shape after the experiment was the same, the degree of compaction of the remaining topography was different.

HIGA Hiroto, FUJITA Kanako, SALEM Salem Ibrahim, SUZUKI Takayuki, NAKAUMURA Yoshiyuki

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 77 ( 2 ) I_391 - I_396 2021

WAVE HEIGHT ESTIMATION BY USING WAVE SOUND FROM AN IC RECORDER AT THE HASAKI COAST, JAPAN

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

In this study, we proposed a method for generating synthetic data for ocean color remote sensing that takes into account the complex optical properties of coastal areas. In order to calculate the synthetic data, radiative transfer simulations were carried out based on inherent optical properties (IOPs), and measured water quality data collected in Tokyo Bay, and the effectiveness of the radiative transfer model was confirmed. In addition, the IOPs and water quality items were categorized by hierarchical clustering, and the model was incorporated into a bio-optical model to develop the synthetic data set that can represent phytoplankton species changes, colored dissolved organic matter (CDOM) from terrestrial and internal production sources, and differences in optical properties between inorganic suspended solids and detritus. The synthetic data of Rrs and IOPs were compared with the measured data and applied to the existing IOPs estimation algorithm, and it was confirmed that the synthetic data were generally in accordance with reality.

SUZUKI Takayuki, ARAKI Daichi, HIGA Hiroto, NAKAMURA Yoshiyuki

Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 77 ( 2 ) I_673 - I_678 2021

A STUDY OF WATER MASS STRUCTURE FROM CONTINUOUS OBSERVATION OF UPWELLING EVENT AT THE INNER PART OF TOKYO BAY

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

Field experiments were conducted at the Hasaki Oceanographical Research Station (HORS), located on the Hasaki coast in Ibaraki prefecture, to investigate the correlation between sound pressure levels and wave heights. The wave sound levels were observed 114 m landside from the average shoreline position and 11.6 m above the average sea level. The observed hourly data from October 20th to November 17th 2020 were used in the analysis. First, the significant wave height was estimated using the data measured by the sound level meter. It was confirmed that the estimation results show an almost similar trend compared to the previous studies (R2 = 0.51). Next, significant wave height values were estimated with an IC recorder. The sound pressure level and relative deviation by the IC recorder and wind speed were used to estimate the wave height. However, the highest correlation coefficient was R2 = 0.15. Therefore, relationship formula was derived between the significant wave height and the IC recorder's sound pressure level using the preceding 1.5 days data. Furthermore, the formula was used to estimate the significant wave height for the following 12 hours. As a result, although there was a slight time delay, it was found that the wave heights can be estimated with a good accurately (R2 = 0.64).

HAYASHI Koki, NAIWEN Chi, HIGA Hiroto, SUZUKI Takayuki, IMAMURA Masahiro, OKADA Teruhisa, NAKAMURA … Show more authors

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 77 ( 2 ) I_367 - I_372 2021

ANALYSIS OF ARCUATULA SENHOUSIA DISTRIBUTION CHRACTERISTICS USING UAV AERIAL IMAGES IN THE ARIAKE SEA TIDAL FLAT FISHING GROUND

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

Through continuous observations conducted during upwelling event in the inner part of Tokyo Bay in 2020, a remarkable two peaks of turbidity was observed just above and below the intermediate anoxic layer. Formation mechanism of the two peaks of turbidity, which was coincide with higher elemental sulpfur concentration, was discussed by comparing TS diagram of data set in the navigation channel obtained between the short period. By employing area wide monitoring-post data sets, intrusion of the oceanic water into the lower layer of the Tokyo Bay and successive continuous blow of northerly wind were attributed to the cause of the upwelling event and formation of blue tide.

HIGA Hiroto, ICHIMURA Yasushi, MIYATSUJI Takashi, SUZUKI Takayuki

Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 77 ( 2 ) I_697 - I_702 2021

ANALYSIS ON MANGROVES DISTRIBUTION CHANGE OVER THE LAST 40 YEARS BY USING RGB IMAGES OF AIRA RIVER MOUTH IN ITIOMOTE ISLAND, JAPAN AND EFFECT BY SEA LEVEL RISE

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

In this study, we devised a monitoring method for simultaneously estimating elevation, median grain size (D50), and Arcuatula senhousia distribution using Unmanned Aerial Vehicle (UAV) aerial images of tidal flat fisheries in the Konagai sight frontage of Isahaya City, Nagasaki Prefecture. The elevation of the tidal flat was estimated using Agisoft photoscan, and the D50 was estimated based on the reflectance obtained from the aerial images. In the elevation estimation, the bias was about 0.017m, and the D50 was correlated with the reflectance with R2 =0.615 (N=9). The detection accuracy of the Arcuatula senhousia distribution was found to be more than 70% at an altitude of 5~20m with 12-megapixel camera and decreased to less than 50% at an altitude of 30m or higher, and more than 60% at an altitude of 40m with 50-megapixel camera and decreased to less than 60% at an altitude of 50m. In addition, by examining the relationship between the estimated spatial distribution of each parameter, we were able to identify the area where Arcuatula senhousia tends to occur.

NAKAMURA Wataru, NAKAMURA Yoshiyuki, FUJIMOTO Kiyoshi, SUZUKI Takayuki, HIGA Hiroto

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 77 ( 2 ) I_925 - I_930 2021

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

To analyze the mangroves distribution change in Aira river mouth in Iriomote Island and the effects of sea level rise, the growing ground heights of four mangroves species were measured. As a result of analyzing the tidal observation records in Ishigaki Island, the sea level rise rate was about 2.3 mm/year, and the annual inundation period of the ground height where the tallest mangroves were growing was 3288 hours for A. marina, 2424 hours for S. alba, 2040 hours for R. stylosa, and 1584 hours for B. gymnorhiza. As a result of analyzing the images of Aira river mouth taken in the past, the mangrove forest expanded from 5.24 ha in 1978 to 7.74 ha in 2017, and the R. stylosa forest transitioned to the B. gymnorhiza forest, and the S. alba growing on the tidal flat to the R. stylosa forest. By analyzing the tidal observation records in Ishigaki island and the estimated distribution of mangrove species in Aira river mouth, the sediment accumulation rate of mangrove species in Aira river mouth is about 3.85 mm/year, which is higher than the sea level rise rate of 2.3 mm/year, indicating that the distribution of mangrove species has been expanding.

DEVELOPMENT OF ATMOSPHERIC CORRECTION METHOD FOR COALSTAL AREA USING GCOM-C / SGLI

Taiga NAKAYAMA, Hiroto HIGA, Kazunori OGATA, Mitsuhiro TORATANI

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 76 ( 2 ) I_1111 - I_1116 2020.7 [Reviewed]

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

In ocean color remote sensing by satellites on the coastal areas, the atmospheric correction which is preprocessing calculation for satellite image analysis, causes the error, which has been one of the main issue of water quality estimation. Our objectives in this study are to improve the estimation accuracy of remote sensing reflectance(Rrs) by developing the atmospheric correction algorithm suitable for coastal areas using SGLI (Second generation Global Imager) mounted on GCOM-C (Global Change Observation Mission – Climate) . Firstly, we constructed the in- water models based on the in-situ values of Specific Inherent Optical Properties (SIOPs) of Tokyo Bay and incorporated them into the conventional atmospheric correction algorithm. Thereby, the estimation accuracy of the aerosol reflectance was improved by the developed atmospheric correctin algorithm suitable for Tokyo Bay. As a result, in comparison with the calculation results of the conventional atmospheric correction algorithm, the mean normalized bias was improved as from 498.3% to 68.6% at 380 nm, 447.7% to 117.0% at 412 nm, 338.3% to 113.9% at 443 nm, and 137.6% to 32.6% at 490 nm, 64.5% to 11.2% at 530 nm, 32.8% to 14.2% at 565 nm, and 50.1% to 10.1% at 673.5 nm.

DEVELOPMENT OF BIO-OPTICAL MODEL BASED ON OPTICAL CLASSIFICATION OF IN-WATER MATTERS AND VERIFICATION OF AN ESTIMATION METHOD FOR INHERENT OPTICAL PROPERTIES IN TOKYO BAY

Kanako FUJITA, Hiroto HIGA, Yoshiyuki NAKAMURA, Takayuki SUZUKI

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 76 ( 2 ) I_1375 - I_1380 2020.7 [Reviewed]

An estimation method for blue tide distribution in Tokyo Bay based on sulfur concentrations using Geostationary Ocean Color Imager (GOCI)

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

Since ocean color changes complicatedly because in-water matter compositions change by internal production or river discharges in coastal areas, estimation errors happen on remote sensing reflectance (Rrs) simulation by bio-optical model. In this study, the optical properties of phytoplankton, tripton, and CDOM classified by hierarchical classification and developed bio-optical model considering changes of in-water matter compositions. As a result, the developed model could calculate Rrs with high accuracy compared to the previous model. Furthermore, applied the Rrs simulation by the developed model to Qusai Analytical Algorithm, it was found that CDOM, tripton and the difference of dominant phytoplankton largely affect the estimation accuracy of absorption coefficients and the logarithmic trend between the input value.

Higa Hiroto, Sugahara Shogo, Salem Salem Ibrahim, Nakamura Yoshiyuki, Suzuki Takayuki

ESTUARINE COASTAL AND SHELF SCIENCE 235 2020.4 [Reviewed]

LABORATORY STUDY OF MIXED-SEDIMENT TRANSPORT AND ESTIMATION OF SPATIAL DISTRIBUTION OF FINE GRAVEL DUE TO INUNDATION FLOW

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

Blue tide, which occurs in eutrophic semi-enclosed bays, is recognized as an important environmental problem because it causes mass mortality of fish and shellfish. In Tokyo Bay, which is a typical eutrophic semi-enclosed bay in Japan, fishery damage due to blue tide is frequently reported. Continuous monitoring is needed for effective water environment management and conservation because blue tides can be too short in duration to observe in the course of field observations. The aim of this study is to develop a model for estimating the distribution of blue tide based on sulfur concentration, which is a key element associated with blue tide. Using real-time data from the Geostationary Ocean Color Imager (GOCI) to estimate sulfur concentrations, we can clearly identify the spatial distributions of blue tides. We developed an empirical model using in situ measurement of sulfur and remote sensing reflectance to obtain sulfur concentration (R2 = 0.851). The developed model was applied to GOCI images acquired shortly after field observations during a blue tide on 24 August 2015 in Tokyo Bay in order to validate the accuracy of the sulfur estimation. Estimated and measured sulfur concentration showed less difference when the time between the start of field observations and GOCI image capture was comparatively small (R2 = 0.704). Further, the blue tide distributions could be estimated by applying the developed model to other images acquired during blue tide occurrences at other dates and years. In conclusion, spatial distributions of blue tide in Tokyo Bay can be adequately estimated based on sulfur concentration determined from GOCI images.

SUZUKI Takayuki, KANEKO Aya, HIGA Hiroto, NAKAMURA Yoshiyuki

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 76 ( 2 ) I_589 - I_594 2020 [Reviewed]

INITIAL ACCURACY VALIDATION AND DISTRIBUTION CHARACTERISTICS OF HIGH-RESOLUTION SST IN TOKYO BAY BY THE SATELLITE "SHIKISAI"

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

In this study, laboratory experimental tests were performed in a small two-dimensional wave flume. Specific quantities of mixed sediment, i.e., medium sand (d50 = 0.64 mm), coarse sand (d50 = 1.59 mm), and fine gravel (d50 = 4.05 mm), were placed near the shoreline of the landside, and these sediments were pushed landward due to the inundation flow of the transient wave. The spatial distributions of each sediment were investigated, and those of fine gravel in the mixed sediment were estimated. The spatial distributions of fine sand and coarse sand could be separated using a color clustering method by adopting colored sand for coarse sand. The results revealed that the spatial distributions of medium sand and fine gravel are farther transported compared with each uniform material case. However, the spatial distributions of coarse sand cannot be obtained a clear difference with its uniform case. The spatial distribution of fine gravel in mixed sediment can be estimated by tuning the shape of a uniform material using the ratio of medium sand in the mixed sediment.

Other Link： https://ci.nii.ac.jp/naid/130007935934

SAKUNO Yuji, HIGA Hiroto, TORATANI Mitsuhiro, KOBAYSHI Hiroshi

Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 76 ( 2 ) I_702 - I_707 2020 [Reviewed]

SPATIAL VARIABILITY OF MICROPLASTICS IN THE FUJISAWA COAST AND PRELIMINARY EXPERIMENTAL INVESTIGATION OF ITS REMOVAL

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

The objectives of this study are to validate SST (Sea Surface Temperature) of GCOM-C SGLI (commonly known as "Shikisai") in Tokyo Bay and to investigate the characteristics of monthly average SST. SGLI-derived SST was compared 210 samples with in-situ SST at three station in Tokyo bay from January 2019 to August 2019 at 11:00 AM synchronized with satellite within 30 minutes. As a result, the accuracy of SGLI SST in the bay was calculated with a standard deviation of 0.90 °C and a bias of - 0.27 °C when cloud removal was performed using the quality flag. The SST data derived from SGLI had an acquisition rate of 9 to 33% each month. Furthermore, as a feature of the monthly mean SST distribution, SGLI data well captures the front, especially at the bay mouth in January and February.

Other Link： https://ci.nii.ac.jp/naid/130007910235

SUZUKI Takayuki, MIYAZAKI Rei, HIGA Hiroto, NAKAMURA Yoshiyuki

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 76 ( 2 ) I_1171 - I_1176 2020 [Reviewed]

ANALYZE THE COASTAL STORM IMPULSE (COSI) PARAMETER AND BEACH EROSION AT HASAKI COAST, JAPAN

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

The presence of microplastics (MP) in oceans and beaches have become an issue of concern globally. The distribution of MP on coasts should be known to understand the movement of MP. In this study, the spatial and temporal variation of MP at the Fujisawa coast, Japan, was observed in spring and autumn. The results revealed that the presence of MP on the coast was 93 per m2 at the coast. Even on the same coast, the spatial and temporal variation existed, and the movement of MP on the beach may be significantly affected by the wind force. Moreover, more than 90 % of MP in the sand could be removed using a simple removal technique.

Other Link： https://ci.nii.ac.jp/naid/130007935767

MALEK Md Abdul, SUZUKI Takayuki, HIGA Hiroto, NAKAMURA Yoshiyuki

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 76 ( 2 ) I_1061 - I_1066 2020 [Reviewed]

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

Other Link： https://ci.nii.ac.jp/naid/130007910167

沿岸域・湖沼における水色リモートセンシングのための固有光学特性の解析

瀧英人, 比嘉紘士, 中村由行, 鈴木崇之

日本水環境学会年会講演集 54 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

Global -scale Retrieval of Inherent Optical Properties using Machine Learning

Hiroto Higa, Salem Ibrahim Salem

The 8th Asian/17th Korea-Japan workshop on ocean color (8th AWOC/17th KJWOC) 32 2020

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

Validation of Inherent Optical Properties Algorithms Considering GCOM-C SGLI bands using in situ Dataset

Ryuya Matsushita, Hiroto Higa, Salem Ibrahim Salem, Joji Ishizaka

he 8th Asian/17th Korea-Japan workshop on ocean color (8th AWOC/17th KJWOC) 24 2020

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

A suggestion for SGLI Atmospheric Correction Model by Considering Absorptive Aerosol in Tokyo Bay

Taiga Nakayama, Hiroto Higa, Mitsuhiro Toratani

The 8th Asian/17th Korea-Japan workshop on ocean color (8th AWOC/17th KJWOC) 26 2020

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

Development of Ocean Color Datasets for an Optically Complex Coastal Area

Kanako Fujita, Hiroto Higa, Salem Ibrahim Salem

The 8th Asian/17th Korea-Japan workshop on ocean color (8th AWOC/17th KJWOC) 31 2020

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

GCOM-C/SGLI検証のための大気・水中の連続光学観測

比嘉紘士, 中山大雅, 高橋邦明, 村岡秀夫

日本リモートセンシング学会学術講演会論文集 177 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本リモートセンシング学会 Joint Work

Development of Simulated In-Situ Bio-optical Dataset for Satellite Data Product Classification

Maulidya N.I.B., Hiroto Higa, Salem Ibrahim Salem, Takayuki Suzuki

The 7th Asian/16th Korea-Japan workshop on ocean color (7th AWOC/16th KJWOC) P-09 2020

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

A Suggestion of An Atmospheric Correction Method for Specific Coastal Areas

Taiga Nakayama, Hiroto Higa, Mitsuhiro Toratani

The 7th Asian/16th Korea-Japan workshop on ocean color (7th AWOC/16th KJWOC) 0-03-04 2020

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

Elucidating Back-Scattering Properties in Coastal Areas and Lakes by using Hydroscat-6p and Radiative Transfer Simulatio

Hiroto Higa, Hidehito Taki, Salem Ibrahim Salem

The 7th Asian/16th Korea-Japan workshop on ocean color (7th AWOC/16th KJWOC) 0-03-01 2020

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

Attempts to Improve the Simulation of Phytoplankton Absorption Spectra for Various Trophic Statuses

Salem Ibrahim Salem, Hiroto Higa, Joji Ishizaka, Kazuo Oki

The 7th Asian/16th Korea-Japan workshop on ocean color (7th AWOC/16th KJWOC) 0-03-03 2020

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

Development of bio-optical model considering the variation in dominant species of phytoplankton by hierarchical clustering, Japan

Kanako Fujita, Hiroto Higa, Salem Ibrahim Salem

The 7th Asian/16th Korea-Japan workshop on ocean color (7th AWOC/16th KJWOC) 0-03-04 2020

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

階層クラスタリングによる植物プランクトンの光学的特徴分類に基づいた生物光学モデルの構築

藤田夏菜子, 比嘉紘士, Salem Ibrahim Salem

日本リモートセンシング学会学術講演会論文集 67 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本リモートセンシング学会 Joint Work

特定の沿岸域に対するGCOM-C/SGLIの大気補正手法の提案

比嘉紘士, 中山大雅, 緒方一紀, 虎谷充浩, Salem Ibrahim Salem

日本リモートセンシング学会学術講演会論文集 67 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本リモートセンシング学会 Joint Work

静止海色衛星による硫黄の光学特性に基づいた青潮推定手法の開発

比嘉紘士, 中村航

Japan Geoscience Union Meeting 2019 (JpGU2019) pACG45-07 2020

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

GCOM-C SGLIデータによる西日本豪雨直後の瀬戸内海の水質・赤潮分布特性

作野裕司, 比嘉紘士, 小林拓, 虎谷充浩

Japan Geoscience Union Meeting 2019 (JpGU2019) ACG45-08 2020

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

東京湾におけるGCOM-C/SGLIを利用した大気-水中結合アルゴリズムの開発

中山大雅, 比嘉紘士, 緒方一紀

Japan Geoscience Union Meeting 2019 (JpGU2019) ACG45-05 2020

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

沿岸域、湖沼における放射伝達シミュレーションによる後方散乱係数の不確実性に関する解析

瀧英人, 比嘉紘士, 中村由行, 鈴木崇之

Japan Geoscience Union Meeting 2019 (JpGU2019) 2020

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

Toward a global retrieval of in-water optical properties using Deep Neural Network

Salem Ibrahim Salem, Hiroto Higa, Kazuo Oki, Taikan Oki

Japan Geoscience Union Meeting 2019 (JpGU2019) ROMBUNNO.ACG45-04 2020

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

生態系モデルを用いた東京湾における青潮の再現

伊藤大樹, 中村由行, 比嘉紘士, 鄭雅倫

日本水環境学会年会講演集 54 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

DEVELOPMENT OF A BLUE TIDE ESTIMATION METHOD BASED ON OPTICAL PROPERTIES OF SULFUR BY GEOSTATIONARY OCEAN COLOR SATELLITE

Hiroto HIGA, Wataru NAKAMURA, Shogo SUGAHARA, Yoshiyuki NAKAMURA, Takayuki SUZUKI

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 75 ( 2 ) I_1057 - I_1062 2019.7 [Reviewed]

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

In this study, we developed a sulfur estimation model for blue tide distributions using geostationary ocean color imager (GOCI) data. In order to develop the sulfur estimation model, Rrs with blue tides, and light absorption coefficient and backscattering coefficient of sulfur particles were figured out by conducting field observations in Tokyo Bay and laboratory experiments. Based on the measured sulfur optical properties, we developed a bio-optical model which was incorporated sulfur as a variable and then Rrs with fluctuation of sulfur concentrations could be calculated. A sulfur estimation model based on QAA_v6 improved by the results of the calculated Rrs of blue tides was developed. Compared to the estimated sulfur by GOCI data with the measured sulfur, it was possible to estimate sulfur concentrations with high accuracy when the difference between satellite data acquisition time and stating time of sampling in the field was small. Furthermore, it was captured that spatial distributions of sulfur concentration have changed with every 1-hour interval with the change of wind condition.

沿岸域における水色リモートセンシングの水質誤差要因の解析

中山大雅, 比嘉紘士, 作野裕司

日本水環境学会年会講演集 54 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

静止海色衛星による硫黄の光学特性に基づいた青潮推定手法の提案

中村航, 比嘉紘士, 中村由行

日本水環境学会年会講演集 54 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

GCOM-C/SGLI OCEAN STANDARD PRODUCTS AND EARLY VALIDATION RESULTS

Toratani Mitsuhiro, Ogata Kazunori, Suzuki Koji, Ishizaka Joji, Hirawake Toru, Hirata Takafumi, Isa … Show more authors

2019 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS 2019) 4741 - 4744 2019

Web of Science

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

A consideration for estimation of Chl-a and turbidity by using red and near infra-red wavelengths in coastal areas and lakes

Hidehito Taki, Hiroto Higa, Yoshiyuki Nakamura, Takayuki Suzuki

The 14th Pan Ocean Remote Sensing Conference(PORSEC2018) 2018.11 [Reviewed]

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

Intergrading multispectral satellite data with deep neural for retrieval of the inherent and apparent optical properties in a global scal

Salem Ibrahim Salem, Hiroto Higa, Kazuo Oki, Taikan Oki

The 14th Pan Ocean Remote Sensing Conference(PORSEC2018) 2018.11 [Reviewed]

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

FIELD OBSERVATIONS OF CROSS-SHORE SEDIMENT TRANSPORT AND SEABED MIXING DEPTHS USING FLUORESCENT SAND TRACERS

Takayuki SUZUKI, Kiichi TAJIMA, Hiroto HIGA, Yoshiyuki NAKAMURA, Shinichi YANAGISHIMA

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 74 ( 2 ) I_763 - I_768 2018.7 [Reviewed]

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

Cross-shore sediment transport and the sediment mixing of inner-surf and outer-surf zones were investigated using field data observed at a dissipative sandy beach. The field observations were conducted in May 2017 for 12 days. During the observations, since an outer bar did not exist, the sediment on the offshore side of the surf zone moved toward the shoreline. Moreover, the sediment in the surf zone moved to the offshore side of the surf zone because of undertow. The mixing depths were observed from sand cores using fluorescent sand tracers. The results indicate that the mixing depths in the surf zone were approximately 31 cm, and its spatial distribution was estimated using the wave breaking height considering the wave breaking zone. The mixing depth on the offshore side of the surf zone may be correlated with the ripple height.

A SALINITY ESTIMATION METHOD USING GEOSTATIONARY OCEAN COLOR IMAGER IN EUTROPHICATED COASTAL AREAS

Hiroto HIGA, Tomohiro FUKUDA, Yoshiyuki NAKAMURA, Takayuki SUZUKI

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 74 ( 2 ) I_1465 - I_1470 2018.7 [Reviewed]

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

In this study, we developed a method to estimate spatial salinity distributions based on a relationship between absorption coefficients of color dissolved organic matter (aCDOM) and Salinity, by estimating aCDOM using COMS/GOCI in eutrophicated coastal areas. Using Bio-Optical model, which was developed by in situ optical data collected at an inner part of Tokyo Bay, the aCDOM estimation accuracy was evaluated against changes of Chlorophyll-a (Chl-a) and non-algal particles (NAP). As a result, an aCDOM estimation model based on a ratio of remote sensing reflectance, Rrs(660 nm)/Rrs(490 nm) was effective when Chl-a is low concentration. Moreover, an aCDOM estimation model based on Rrs(550 nm)/Rrs(660 nm) could estimate aCDOM adequately when Chl-a is high concentration. Therefore, a switching method for the two aCDOM estimation models as using threshold values from Chl-a spatial distributions, which is preliminarily estimated by applying a field observation result assimilation FLH to GOCI images, was suggested. In comparison with in situ salinity and estimated salinity, the relationship was R2=0.71, RMSE=1.04(N=114) and it could be available to estimate salinity with high accuracy more than previous methods.

EFFECTS OF ORGANIC CONTENT ON WATER CONTENT OF BOTTOM SEDIMENT IN EUTOROPHIC COASTAL AND BRACKISH WATER REGION

Keita HATTORI, Yoshiyuki NAKAMURA, Tetsunori INOUE, Hiroto HIGA, Ryoji NAITO, Tomonari OKADA

Journal of Environmental Engineering Research 74 ( 7 ) III_43 - III_51 2018 [Reviewed]

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

既往の研究において,様々な水域の底泥で,有機物量を示す指標と含水比が高い相関を持つことが知られている.しかしながら,複数の水域の底泥調査データを比較・検討した例は少なく,有機物量と含水比の関係性は経験的なものにとどまっている.そこで本研究では富栄養化した複数の海域・汽水域の底泥調査データを解析し,有機物量と含水比の関係性を検証した.解析の結果,主として河口域周辺のデータを除き,TOCと含水比の関係性は水域ごとに大きな違いは見られず,酷似した関係性を示した.加えて,有機物量の変化に応じて含水比がどのように影響を受けるかを検証するために,有機物を過酸化水素水によって分解した底泥試料を作成し,それらを試験管に再堆積させ含水比を測定することにより,有機物量が含水比に及ぼす影響を実験的に調べた.実験の結果,有機物を分解したサンプルは含水比が減少し,有機物量によって含水比が変化することが実験的に明らかになった.以上の結果から,一次生産由来の有機物量は堆積過程の支配因子であり,底泥表層の含水比に強く影響を与えることが明らかとなった.

Validation of wavelength band set of SGLI and OLCI to estimate chlorophyll-a concentration

Taiga Nalkayama, Hiroto Higa

The 6th Asian/15th Korea-Japan workshop on ocean color (6th AWOC/15th KJWOC) 41 2018

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

Modeling of Optical Properties for Blue Tides Considering Light Scattering of Sulfur Colloid Particles in Tokyo Bay

Wataru Nakamura, Hiroto Higa

The 6th Asian/15th Korea-Japan workshop on ocean color (6th AWOC/15th KJWOC) 14 2018

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

Consideration the spectral characteristics of Backscattering coefficient in coastal areas and lakes

Hidehito Taki, Hiroto Higa, Yoshiyuki Nakamura, Takayuki Suzuki

The 6th Asian/15th Korea-Japan workshop on ocean color (6th AWOC/15th KJWOC) 4 2018

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

An Estimation Method of Salinity Distribution based on Optical Property of Color Dissolved Organic Matter using COMS/GOCI in a Heavily Eutrophic Coastal Area, Tokyo Bay, Japan

Hiroto Higa, Tomohiro Fukuda

The 6th Asian/15th Korea-Japan workshop on ocean color (6th AWOC/15th KJWOC) 8 2018

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

A STUDY OF SEDIMENT MOVEMENTS DURING CALM WAVE CONDITIONS USING FLUORESCENT SAND TRACERS

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 73 ( 2 ) I_667 - I_672 2017.7 [Reviewed]

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

Sediment transport mechanisms in swash, inner-surf and outer-surf zones have been investigated. The authors conducted field surveys in 2014 and 2015 during storm conditions in order to analyze the cross-shore and vertical sediment movements by using fluorescent sand tracers. However, there is a space to investigate sediment movements in the area from the swash zone to the outer-surf zone during calm wave conditions. In this study, the field experiments were conducted in the season of relatively mild wave condition. Five colored fluorescent sand tracers were installed on the seabed in the five different cross-shore locations, and sand cores were collected after surtain duration. Also, wave height, current velocity and wind speed were observed during the experiments. From the results we found that the onshore ward direction of the sediment transport was dominant in the surf zone. Although the sediment also transported offshore ward, the sediment was found until at the offshore end of the trough region. Even during the mild wave conditions, the longshore current velocity was relatively large in the area around trough and outer-bar crest. The sediment movement in the onshore region and offshore region of the outer-bar moved without the correlation, however, the outer-bar formed by both regions of sediments.

Assessment of chlorophyll-a algorithms considering different trophic statuses and optimal bands

Salem Ibrahim Salem, Hiroto Higa, Hyungjun Kim, Hiroshi Kobayashi, Kazuo Oki, Taikan Oki

sensors 17 ( 8 ) 1476 2017.7 [Reviewed]

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI Joint Work

Numerous algorithms have been proposed to retrieve chlorophyll-a concentrations in Case 2 waters; however, the retrieval accuracy is far from satisfactory. In this research, seven algorithms are assessed with different band combinations of multispectral and hyperspectral bands using linear (LN), quadratic polynomial (QP) and power (PW) regression approaches, resulting in altogether 43 algorithmic combinations. These algorithms are evaluated by using simulated and measured datasets to understand the strengths and limitations of these algorithms. Two simulated datasets comprising 500,000 reflectance spectra each, both based on wide ranges of inherent optical properties (IOPs), are generated for the calibration and validation stages. Results reveal that the regression approach (i.e., LN, QP, and PW) has more influence on the simulated dataset than on the measured one. The algorithms that incorporated linear regression provide the highest retrieval accuracy for the simulated dataset. Results from simulated datasets reveal that the 3-band (3b) algorithm that incorporate 665-nm and 680-nm bands and band tuning selection approach outperformed other algorithms with root mean square error (RMSE) of 15.87 mg·m−3, 16.25 mg·m−3, and 19.05 mg·m−3, respectively. The spatial distribution of the best performing algorithms, for various combinations of chlorophyll-a (Chla) and non-algal particles (NAP) concentrations, show that the 3b_tuning_QP and 3b_680_QP outperform other algorithms in terms of minimum RMSE frequency of 33.19% and 60.52%, respectively. However, the two algorithms failed to accurately retrieve Chla for many combinations of Chla and NAP, particularly for low Chla and NAP concentrations. In addition, the spatial distribution emphasizes that no single algorithm can provide outstanding accuracy for Chla retrieval and that multi-algorithms should be included to reduce the error. Comparing the results of the measured and simulated datasets reveal that the algorithms that incorporate the 665-nm band outperform other algorithms for measured dataset (RMSE = 36.84 mg·m−3), while algorithms that incorporate the band tuning approach provide the highest retrieval accuracy for the simulated dataset (RMSE = 25.05 mg·m−3).

APPLICATION OF FORESHORE BEACH PROFILE CHANGE MODEL CONSIDERING THE EFFECT OF BEACH SLOPE

Naoto MITOURIDA, Takayuki SUZUKI, Hiroto HIGA

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 73 ( 2 ) I_577 - I_582 2017.7 [Reviewed]

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

Beach profile change in the foreshore zone was affected by wave-induced cross-shore sediment transport. Until now, the characteristics of cross-shore sediment transport in the swash zone at the Hasaki coast, Japan have been investigated, and a foreshore beach profile change model was proposed. The model was applied to the Hasaki coast, and it is reported that the shoreline change and the ground elevation change were reproduced with enough accuracy. In order to apply this model to different coasts, however, it needs to include the effect of beach slope on the wave characteristics. In the present study, the model was modified that the unknown parameters were used in the estimate equation of the maximum wave runup height, and the modified model was applied to the different coast with steep beach slope, i.e. coarse sediment diameter. The results were verified with observed field data and found that the model can correctly reproduce the ground elevation and shoreline changes. Thus it is suggested that the model could be used for different coasts by using parameters related to the sediment diameter of the coasts.

A STUDY ON UPWELLING EVENTS WITH AND WITHOUT BLUE TIDE FORMATION IN TOKYO BAY

Kazuya MIYASHITA, Yoshiyuki NAKAMURA, Hiroto HIGA, Yoji TANAKA, Hikaru ITO, Takuya IKEZU, Kazunori … Show more authors

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 73 ( 2 ) I_1213 - I_1218 2017.7 [Reviewed]

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

We conducted continuous quay side observations and four times on-board observation in the inner part of Tokyo Bay from August to September in 2016 to find several upwelling events. One of four on-board observations corresponded to just before a blue tide event when surface water color changed to milky white, and other two corresponded to just before and in the peak of mild upwelling events without any color changes. Analysis based on the TS diagram revealed that the origin of water mass of the quay side during the blue tide event was the water mass upwelled from off shore side of near the bottom of the Chiba navigation channel containing sulfide ion. While during the mild upwellig events, the upwelled water mass came from relatively shallower layer of the channel without elemental sulfur nor sulfide. However, formation of elemental sulfur actively occurred in the deeper part of the navigation channel during the event.

Evaluation of MERIS Chlorophyll-a Retrieval Processors in a Complex Turbid Lake Kasumigaura over a 10-Year Mission

Salem Ibrahim Salem, Marie Hayashi Strand, Hiroto Higa, Hyungjun Kim, Komatsu Kazuhiro, Kazuo Oki, … Show more authors

remote sensing 9 ( 10 ) 1022 2017.7 [Reviewed]

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI Joint Work

The chlorophyll-a (Chla) products of seven processors developed for the Medium Resolution Imaging Spectrometer (MERIS) sensor were evaluated. The seven processors, based on a neural network and band height, were assessed over an optically complex water body with Chla concentrations of 8.10–187.40 mg∙m−3 using 10-year MERIS archival data. These processors were adopted for the Ocean and Land Color Instrument (OLCI) sensor. Results indicated that the four processors of band height (i.e. the Maximum Chlorophyll Index (MCI_L1); and Fluorescence Line Height (FLH_L1)); neural network (i.e. Eutrophic Lake (EUL); and Case 2 Regional (C2R)) possessed reasonable retrieval accuracy with root mean square error (R2) in the range of 0.42–0.65. However, these processors underestimated the retrieved Chla > 100 mg∙m−3, reflecting the limitation of the band height processors to eliminate the influence of non-phytoplankton matter and highlighting the need to train the neural network for highly turbid waters. MCI_L1 outperformed other processors during the calibration and validation stages (R2 = 0.65, Root mean square error (RMSE) = 22.18 mg∙m−3, the mean absolute relative error (MARE) = 36.88%). In contrast, the results from the Boreal Lake (BOL) and Free University of Berlin (FUB) processors demonstrated their inadequacy to accurately retrieve Chla concentration > 50 mg∙m−3, mainly due to the limitation of the training datasets that resulted in a high MARE for BOL (56.20%) and FUB (57.00%). Mapping the spatial distribution of Chla concentrations across Lake Kasumigaura using the seven processors showed that all processors—except for the BOL and FUB—were able to accurately capture the Chla distribution for moderate and high Chla concentrations. In addition, MCI_L1 and C2R processors were evaluated over 10-years of monthly measured Chla as they demonstrated the best retrieval accuracy from both groups (i.e. band height and neural network, respectively). The retrieved Chla of MCI_L1 was more accurate at tracking seasonal and annual variation in Chla than C2R, with only slight overestimation occurring during the springtime.

ESTIMATION OF SALINITY DISTRIBUTIONS BASED ON THE OPTICAL PROPERTY OF COLOR DISSOLVED ORGANIC MATTER BY THE GEOSTATIONARY OCEAN CLOLOR SATELLITE IN TOKYO BAY

Hiroto HIGA, Tomohiro FUKUDA, Kazuya MIYASHITA, Yoshiyuki NAKAMURA, Takayuki SUZUKI

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 73 ( 2 ) I_1237 - I_1242 2017.7 [Reviewed]

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

In order to estimate salinity distributions based on the optical properties of color dissolved organic matter using the geostationary ocean color satellite in Tokyo Bay, aCDOM(440) estimation model was developed using optical observation data in the field and the estimation application range of the estimated aCDOM(440) was evaluated using the developed bio-optical model for Tokyo Bay. As a result, the aCDOM(440) estimation error increased with increase of light absorption coefficient for particles but it was applicable to estimate salinity relatively after applying the model to GOCI image. Furthermore, the estimated salinity maps showed a situation that low salinity water mass near Edogawa estuarine area spreaded out to Funabashi and Urayasu offshore sides. In addition, when river discharges increased, it was confirmed that low salinity water mass spreaded from the estuarine areas of Arakawa, Sumida and Tama rivers to Kawasaki offshore and it was gradually mixed with high salinity water mass.

CHARACTERISTICS OF SEABED SURFACE SEDIMENT MOVEMENTS USING FLUORESCENT SAND TRACERS

Takayuki SUZUKI, Asumi KAWAGOE, Shinichi YANAGISHIMA, Hiroto HIGA

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 73 ( 2 ) I_594 - I_599 2017.7 [Reviewed]

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

The field experiments were conducted to investigate the characteristics of sediment movements during a short time duration. The focusing area is from the swash zone to the offshore side of the bar. At the Hasaki coast, Japan, five colored fluorescent sand tracers were installed on the seabed at different cross-shore locations, around every 50 m, from near the shoreline to the offshore side of the bar. During the experiments, seven times of seabed surface sediment samplings were conducted every 10 m of cross-shore distance from 1 hour to 144 hours after the installation of the fluorescent sand tracers. From the analysis, the sediments in the surf zone were spread in the area from near the shoreline to the onshore side of the bar within one hour after the installation. The fluctuation of the centroid of the fluorescent sand distribution was correlated with that of the wave breaking point. The sediment movements at the offshore side of the bar had a correlation with the value of the offshore wave energy flux.

Spatiotemporal Variation of Turbidity Based on Landsat 8 OLI in Cam Ranh Bay and Thuy Trieu Lagoon, Vietnam

Nguyen Hao Quang, Jun Sasaki, Hiroto Higa, Nguyen Huu Huan

water 9 ( 8 ) 570 2017.6 [Reviewed]

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI Joint Work

In recent years, seagrass beds in Cam Ranh Bay and Thuy Trieu Lagoon have declined from 800 to 550 hectares, resulting insignificantly reducing the number of fish catch. This phenomenon is due to the effect of the degradation of water environment. Turbidity is one of the most important water quality parameters directly related to underwater light penetration which affects the primary productivity. This study aims to investigate spatiotemporal variation of turbidity in the waters with major factors affecting its patterns using remote sensing data. An algorithm for turbidity retrieval was developed based on the correlation between in situ measurements and a red band of Landsat 8 OLI with R2 = 0.84 (p < 0.05). Simulating WAves Nearshore (SWAN) model was used to compute bed shear stress, a major factor affecting turbidity in shallow waters. In addition, the relationships between turbidity and rainfall, and bed shear stress induced by wind were analyzed. It was found that: (1) In the dry season, turbidity was low at the middle of the bay while it was high in shallow waters nearby coastlines. Resuspension of bed sediment was a major factor controlling turbidity during time with no rainfall. (2) In the rainy season or for a short time after rainfall in the dry season, turbidity was high due to a large amount of runoff entering into the study area.

Multi-Algorithm Indices and Look-Up Table for Chlorophyll-a Retrieval in Highly Turbid Water Bodies Using Multispectral Data

Salem Ibrahim Salem, Hiroto Higa, Hyungjun Kim, Komatsu Kazuhiro, Hiroshi Kobayashi, Kazuo Oki, Tai … Show more authors

remote sensing 9 ( 6 ) 2017.5 [Reviewed]

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI Joint Work

Many approaches have been proposed for monitoring the eutrophication of Case 2 waters using remote sensing data. Semi-analytical algorithms and spectrum matching are two major approaches for chlorophyll-a (Chla) retrieval. Semi-analytical algorithms provide indices correlated with phytoplankton characteristics, (e.g., maximum and minimum absorption peaks). Algorithms' indices are correlated with measured Chla through the regression process. The main drawback of the semi-analytical algorithms is that the derived relation is location and data limited. Spectrum matching and the look-up table approach rely on matching the measured reflectance with a large library of simulated references corresponding to wide ranges of water properties. The spectral matching approach taking hyperspectral measured reflectance as an input, leading to difficulties in incorporating data from multispectral satellites. Consequently, multi-algorithm indices and the look-up table (MAIN-LUT) technique is proposed to combine the merits of semi-analytical algorithms and look-up table, which can be applied to multispectral data. Eight combinations of four algorithms (i.e., 2-band, 3-band, maximum chlorophyll index, and normalized difference chlorophyll index) are investigated for the MAIN-LUT technique. In situ measurements and Medium Resolution Imaging Spectrometer (MERIS) sensor data are used to validate MAIN-LUT. In general, the MAIN-LUT provide a comparable retrieval accuracy with locally tuned algorithms. The most accurate of the locally tuned algorithms varied among datasets, revealing the limitation of these algorithms to be applied universally. In contrast, the MAIN-LUT provided relatively high retrieval accuracy for Tokyo Bay (R2 = 0.692, root mean square error (RMSE) = 21.4 mg m−3), Lake Kasumigaura (R2 = 0.866, RMSE = 11.3 mg m−3), and MERIS data over Lake Kasumigaura (R2 = 0.57, RMSE = 36.5 mg m−3). The simulated reflectance library of MAIN-LUT was generated based on inherent optical properties of Tokyo Bay; however, the MAIN-LUT also provided high retrieval accuracy for Lake Kasumigaura. MAIN-LUT could capture the spatial and temporal distribution of Chla concentration for Lake Kasumigaura.

A sulfur estimation method to capture blue tide distributions by satellite remote sensing in Tokyo Bay, Japan

Hiroto HIGA, Yoshiyuki NAKAMURA, Takayuki SUZUKI

International Symposium on Remote Sensing(ISRS2015) 2017.5 [Reviewed]

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

底泥含水比と他の底質指標との普遍的な相関性について

服部啓太, 中村由行, 比嘉紘士, 鈴木崇之

日本水環境学会年会講演集 51 21 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

海色リモートセンシングによる青潮分布検出のための硫黄濃度推定手法の提案

比嘉紘士, 中村由行, 鈴木崇之

海洋理工学会平成29年度春季大会 31 - 34 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：海洋理工学会 Joint Work

霞ヶ浦における衛星リモートセンシングを用いた白濁現象の空間的動態に関する解析

比嘉紘士, 中村由行, 五十嵐貴之

日本水環境学会年会講演集 51 278 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

人工衛星による有色溶存有機物推定に基づいた東京湾への河川水流入過程に関する一考察

福田智弘, 比嘉紘士, 中村由行, 鈴木崇之

日本水環境学会年会講演集 51 173 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

現地観測に基づいた東京湾湾奥部における貧酸素水塊形成および湧昇現象の考察

宮下寿哉, 中村由行, 比嘉紘士, 田中陽二

日本水環境学会年会講演集 51 170 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

3D モデルによる青潮の数値解析とその対応策の検討

伊藤比伽留, 中村由行, 比嘉紘士, 田中陽二

日本水環境学会年会講演集 51 169 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

STATISTICAL ANALYSIS OF THE HORIZONTAL DISTRIBUTION CHARACTERISTICS OF SEDIMENT QUALITIES IN PORT OF NAGOYA

Journal of Japan Society of Civil Engineers Ser G (Environmental Research) 72 ( 7 ) III_55 - III_65 2016.12 [Reviewed]

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

FIELD OBSERVATION OF BLUE TIDE UPWELLING AND OUTFLOW TO MIDDLE LAYER IN TOKYO BAY

Yoji TANAKA, Yoshiyuki NAKAMURA, Hiroto HIGA, Yoshirou UNO, Tomoaki KARUBE, Hikaru ITO, Shogo SUGAH … Show more authors

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 72 ( 2 ) I_1237 - I_1242 2016.7 [Reviewed]

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

The purpose of this study is to analyze the relationship between high turbidity and sulfur, and transfer of a blue tide after upwelling. We achieved ship observations of a blue tide at 24th August 2015 on the inner part of Tokyo Bay. Upwelling water of the blue tide outflowed to the middle layer for analyzing a composition of the blue tide water. It was considered that a density of upwelling water decreased slightly due to mix with around surface water. The blue tide water drifted on a pycnocline for wind driven current and density current. There was a definite positive correlation between turbidity and sulfur from analysis of water samples. Therefore, high turbidity indicates the particulate sulfur element in a blue tide. It was found from the analysis of automatic water quality measurement systems that an upwelling of high density water was not always to produce extensive blue tide. An occurrence of large-scale blue tide may depend on an accumulation of hydrogen sulfide on a flat bottom area of the bay.

A STUDY OF SEDIMENT MOVEMENTS DURING A STORM USING TWO DIAMETERS FLUORESCENT SAND

Yu INAMI, Takayuki SUZUKI, Masayuki BANNO, Hiroto HIGA, Yoshiyuki NAKAMURA, Shin-ichi YANAGISHIMA

72 ( 2 ) I_1237 - I_1242 2016.7 [Reviewed]

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

The field experiments were conducted at Hasaki Coast, Japan to investigate the sediment cross-shore and vertical movements in the area of the swash zone to the offshore end of the surf zone using fluorescent sand. In the experiments, two diameters of fluorescent sand were installed in the coast for two locations in different colors, in the surf zone and the offshore end of the surf zone. After one storm pass through the site, nine vertical sand cores were collected. During the experiments, wave data and beach profile data were also observed. The cores subdivided after scanning by an X-ray scanner, and the vertical distributions of sediment diameter and the number of fluorescent sand were analyzed. When an offshore bar was not formed, fine sand located at the offshore side of the bar also contributes to the berm formation. The coarse sand located at the offshore side of the bar, however, does not contribute to the berm formation. The moving behavior of coarse sand was different from that of fine sand, and it was suggested that the coarse sand was immediately transported by near-bed motions of waves and currents during the storm.

A PROPOSED METHOD OF MONITORING FLOW FIELD AND MASS BUDGET IN ESTUARY

Yoshimu KUSUMOTO, Yukio KOIBUCHI, Hiroto HIGA, Junichiro MANO

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 72 ( 2 ) I_1225 - I_1230 2016.7 [Reviewed]

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

While recreational waterfront in urban area has been developed, chronical water quality degradation such as red tide and sewage water inflow has been occurred. Monitoring flow field around estuaries is required for appropriate water management. However, it is technically challenging to measure or calculate river discharge in estuaries due to complexity of its flow structure. This study discusses a method of measuring discharge of two-layered flow field by a stationary H-ADCP at Odaibakaihin park. Firstly, in a preliminary survey by an ADCP, a phase shift was observed in tidal velocity components of upper layer and lower layer in the vertical direction, which can be utilized to detect boundary of two layers and to determine thickness of the upper layer. The H-ADCP was settled upward in an angle of 1.5 degrees. Current profiles across the boundary were monitored, and river discharge of two-layered flow field was simultaneously calculated. In addition, a water quality meter combined with two pumping devices was vertically arrayed to observe water properties of multiple layers. Freshwater discharge could be quantified by relating flow rate and salinity of upper layer. This proposed monitoring method enables to monitor discharge of respective water layers and will expand more observatories effectively along analogous estuaries.

RETRIEVING BLUE TIDE DISTRIBUTIONS BASED ON A TURBIDITY ESTIMATION METHOD USING THE COMS/GOCI

比嘉紘士, 中村由行, 田中陽二, 管原庄吾, 虎谷充浩, 伊藤比加留, 鈴木崇之

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 72 ( 2 ) I_1759 - I_1764 2016 [Reviewed]

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

In order to estimate blue tide distributions by satellite remote sensing, we carried out a synchronous observation using a ship and GOCI satellite on 24th. Aug, 2015. In the ship observation, we measured optical properties of the blue tide and Turbidity detected light scattering of sulfur colloids of the blue tide at each station. Based on the observed optical properties and the Turbidity, blue tides estimation model was developed and was applied to a GOCI image to evaluate the estimation accuracy. As a result, the developed model estimated the blue tide distribution of 24th, Aug, 2015 with high accuracy and then it was also capable of estimating blue tide distributions captured in other GOCI images with high accuracy. Hence, the model is expected not only figuring out blue tide distributions but also to be utilized as a monitoring technic for the blue tides.

東京湾奥部における 2015年8月に発生した青潮の船上観測

田中陽二, 比嘉紘士, 伊藤比伽留, 中村由行

日本水環境学会年会講演集 50 135 2016

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

Development of Sulfur Estimation Model for Monitoring of Blue Tides by COMS/GOCI in a semi-Enclosed Water Area

Hiroto Higa, Yoshiyuki Nakamura, Takayuki Suzuki

The 4th Asian/13th Korea-Japan workshop on ocean color (4th AWOC/13th KJWOC) 34 2016

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

Estimating Absorption Coefficients of CDOM using Correction Method for the Atmospheric Correction Error of COMS/GOCI in Tokyo Bay

Tomohiro Fukuda, Hiroto Higa, Yoshiyuki Nakamura, Takayuki Suzuki, Hiroshi Kobayashi

The 4th Asian/13th Korea-Japan workshop on ocean color (4th AWOC/13th KJWOC) 35 2016

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

東京湾における3次元的モニタリングによる青潮・貧酸素水塊の挙動に関する考察

比嘉紘士, 中村由行, 伊藤比伽留, 田中陽二

日本水環境学会年会講演集 50 520 2016

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

霞ヶ浦での白濁現象前後における藻類交代に関する一考察

五十嵐貴之, 中村由行, 比嘉紘士, 梅澤周平

日本水環境学会年会講演集 50 334 2016

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

定点での連続観測により捉えた青潮発生前後の水質変動

伊藤比伽留, 比嘉紘士, 田中陽二, 中村由行

日本水環境学会年会講演集 50 134 2016

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

A suggestion for coastal environment monitoring methods using ocean color remote sensing in Tokyo Bay

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Mitsuhiro TORATANI, Yuji SAKUNO,

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 71 ( 2 ) I_1735 - I_1740 2015.7 [Reviewed]

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

Satellite remote sensing methods of ocean color was developed based on the results of field observations in an eutrophication water area, Tokyo bay. From field observations, it was found that absorption coefficients of phytoplankton and detritus were related to Chl-a and that of color dissolved organic matter (CDOM) to salinity. On the basis of these optical properties, bio-optical model was developed and it showed that aph spectrum around 550nm increased when red tides occurred by the developed model. In addition, using these findings, we developed three parameters, Chl-a estimation model which assimilates observation results, aCDOM estimation model which uses two bands, blue region and red region and ad estimation model, modification of the Quasi-Analytical Algorithm. Furthermore temperature estimation accuracy by MODIS sensor was validated. Thus, it became possible to estimate each of four parameters spatially and simultaneously.

Classification of formation patterns for chlorophyll-a distribution in Tokyo Bay during summer and winter

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Mitsuhiro TORATANI, Yuji SAKUNO,

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 71 ( 2 ) I_1303 - I_1308 2015.7 [Reviewed]

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

Validation of Chlorophyll-a Retrieval Method for GCOM SGLI using a Modified Simple Bio-Optical Algorithm in Tokyo Bay, Japan

Yuji Sakuno, Hiroto Higa, Hiroshi Kobayashi, Yukio Koibuchi, Mitsuhiro Toratani

International Symposium on Remote Sensing (ISRS2015 2015.4 [Reviewed]

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

Numerical Simulation and Remote Sensing for the Analysis of Blue Tide Distribution in Tokyo Bay in September, 2012

Hiroto Higa, Yukio Koibuchi, Hiroshi Kobayashi, Mitsuhiro Toratani, Yuji Sakuno

Journal of Advanced Simulation in Science and Engineering 2 ( 1 ) 1 - 15 2015.3 [Reviewed]

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

To determine the factors contributing to large-scale blue tide occurrences, blue tide distributions captured from satellite images were estimated using the estimation model for blue tides. This model was developed based on the observation results of the optical properties of Tokyo Bay and numerical simulation by a three-dimensional hydrodynamics and ecological model. By complementing the information from the results of both satellite image analysis to estimate the blue tide reflectance and the numerical simulation to calculate the dissolved oxygen (DO) concentration, the upwelling areas of sulfide-containing anoxic water were distinguished from those of non-sulfide-containing anoxic water.

東京湾における有色溶存有機物（CDOM）による湧昇域マッピングの試み

比嘉紘士, 鯉渕幸生, 小林拓, 虎谷充浩, 作野裕司

日本リモートセンシング学会学術講演会論文集 58 51 - 52 2015 [Reviewed]

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本リモートセンシング学会 Joint Work

Varying Factors Affecting the High Concentration of Chlorophyll-a Distribution as Estimated by Satellite Remote Sensing in Tokyo Bay

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Mitsuhiro TORATANI, Yuji SAKUNO,

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 70 ( 2 ) I_1091 - I_1095 2014.7 [Reviewed]

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

In order to determine the behavior of red tide distribution by satellite remote sensing, we found out that the optical properties of Tokyo Bay significantly changes in terms of measured AOP (apparent optical properties) and IOP (inherent optical properties) in field observation. Based on the spectrum variation of measured reflectance, we developed the estimation model of high concentration of Chlorophyll-a (Chl-a). By applying the developed model to satellite images, the spatial variation of high concentration of Chl-a in the bay was discussed in this paper. As a result, Chl-a was gradually increasing from the coast of the bay. It was found that the increment of Chl-a is mainly dependent on the spatial variation of temperature when wind was weak and solar radiation was high.

Clarification of the generation mechanism for blue tide distribution using 3D hydrodynamics and ecological model, and satellite images of Tokyo Bay

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Mitsuhiro TORATANI, Yuji SAKUNO

International Conference on Simulation Technology (JSST2013) 2013.9 [Reviewed]

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

Formation Process of Blue Tide Distribution by Satellite Remote Sensing in Tokyo Bay

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Mitsuhiro TORATANI, Yuji SAKUNO,

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 69 ( 2 ) I_1451 - I_1455 2013.7 [Reviewed]

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

Blue tides, upwelling of anoxic waters, have been a serious environmental problem in Tokyo Bay. It is essential to figure out the behavior of the blue tide distribution occurrence area. To observe the blue tide distribution, the variation of the optical properties for the blue tide was investigated by measuring the backscattering coefficient, the light absorption coefficient and the remote sensing reflectance. Based on the results of the optical properties, we developed the estimation model for blue tide distribution. It was helpful not only monitoring extent of the distribution but also identification of the upwelling region of blue tides because it is able to express color strength of blue tide. In addition, estimated blue tide distribution was verified by 3-dimensional numerical simulation and the reason of the upwelling was understood.

5. A Method for Estimating Blue Tide Distribution by Satellite Remote Sensing in Tokyo Bay, Japan

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Yuji SAKUNO, Mitsuhiro TORATANI

International Symposium on Remote Sensing (ISRS2013), Tokyo Metropolitan area, Japan 2013.5 [Reviewed]

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

Testing the utility of chlorophyll-a retrieval by LCI algorithm in Tokyo Bay using COMS GOCI data

International Symposium on Remote Sensing (ISRS2013), Tokyo Metropolitan area, Japan 2013.5 [Reviewed]

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

猪苗代湖北部水域における水面および水草の分光反射率測定実験-2013年8月

作野裕司, 比嘉紘士, 虎谷充浩, 山口寿史, 村上浩, 尾山洋一, 若林裕之

日本リモートセンシング学会学術講演会論文集 2013

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本リモートセンシング学会 Joint Work

Development of estimation model for high concentrated Chl-a and SS using the correction term of estimated error in coastal area

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Yuji SAKUNO, Mitsuhiro TORATANI

Pan Ocean Remote Sensing Conference (PORSEC)-2012 2012.11 [Reviewed]

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

Investigation on Optical Environmental Properties and Chlorophyll-a Distribution in Tokyo Bay

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Yuji SAKUNO, Mitsuhiro TORATANI, Masahiko ISOBE

Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 68 ( 2 ) I_1486 - I_1490 2012.7 [Reviewed]

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

Remote sensing reflectance (Rrs) and absorption coefficient were measured by carrying out field observation in Tokyo bay to figure out optical properties of high eutrophicated coastal area and to develop estimated model of high concentrated Chlorophyll-a (Chl-a). It was the result that when Rrs of high concentrated Chl-a was observed, green wavelength of Rrs decreases, red wavelength of Rrs increases, and absorption coefficient of the phytoplankton of the green wavelength increases. Based on consideration, we developed estimation model for high concentrated Chl-a using the correction term of estimated error. In the result of verification of suggested model, it could appropriately improve the accuracy. Furthermore, behavior of Chl-a distribution in Tokyo Bay was discussed using the satellite data which was applied for suggested model.

Feasibility study of chlorophyll estimation using GOSAT data

Yuji Sakuno, Hiroshi Kobayashi, Hiroto Higa, Yukio Koibuchi・Mitsuhiro Toratani

The 8th Japan-Korea Workshop on Ocean Color Remote Sensing 2012

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

An estimation method for blue tide distribution based on the light scattering of turbidity

Hiroto Higa, Yoshiyuki Nakamura, Yoji Tanaka, Mitsuhiro Toratani, Hiroshi Kobayashi, Hikaru Ito, Ta … Show more authors

Korea Japan Workshop on Ocean Color Remote Sensing（KJWOC） 39 2012

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

Development of estimation algorithm of high concentrated chlorophyll-a and SS using remote sensing reflectance and inherent optical properties in highly eutrophic coastal area

作野裕司, 小林拓, 比嘉紘士, 鯉渕幸生, 虎谷充浩

Korea Japan Workshop on Ocean Color Remote Sensing（KJWOC） 29 - 31 2012

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

現地観測に基づく秋季の東京湾における濁度による固有光学特性の変動について

比嘉紘士, 鯉渕幸生, 小林拓, 虎谷充浩, 作野裕司

日本リモートセンシング学会学術講演会論文集 53 51 - 52 2012

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本リモートセンシング学会 Joint Work

6. 東京湾におけるリモートセンシング反射率・固有光学特性変動に関する現地観測

比嘉紘士, 鯉渕幸生, 小林拓, 作野裕司, 虎谷充浩

日本水環境学会年会講演集 46 240 2012

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：日本水環境学会 Joint Work

A model for estimating Chlorophyll and SS in coastal area by Satellite Remote Sensing

Hiroto HIGA, Yukio KOIBUCHI, Hiroshi KOBAYASHI, Yuji SAKUNO, Mitsuhiro TORATANI

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 67 ( 2 ) I_1391 - I_1395 2011.7 [Reviewed]

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

In order to estimate accurately Chlorophyll in coastal area which has high concentrations of SS. Field observations of remote sensing reflectance, SS and Chlorophyll were carried out at 4 stations in the head of Tokyo bay. Proposed model contains a correction term which is determined by ratio of remote sensing reflectance at two different wavelengths. Estimation results from this model and field observation resuls showed a good agreement. The error, when applying the previous model to estimating Chlorophyll, was attributed to the lack of consideration on SS.

TESTING THE QUANTITATIVE ASSESSMENT OF OCEAN COLOR UNDER BLUE TIDE CONDITION

Yuji SAKUNO, Hiroshi KOBAYASHI, Hiroto HIGA, Yukio KOIBUCHI, Mitsuhiro TORATANI

Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 67 ( 2 ) I_376 - I_381 2011.5 [Reviewed]