The Bohai Sea(BS)is the unique semi-closed inland sea of China,characterized by degraded water quality due to significant terrestrial pollution input.In order to improve its water quality,a dedicated action named“Uph...The Bohai Sea(BS)is the unique semi-closed inland sea of China,characterized by degraded water quality due to significant terrestrial pollution input.In order to improve its water quality,a dedicated action named“Uphill Battles for Integrated Bohai Sea Management”(UBIBSM,2018–2020)was implemented by the Chinese government.To evaluate the action effectiveness toward water quality improvement,variability of the satelliteobserved water transparency(Secchi disk depth,Z_(SD))was explored,with special emphasis on the nearshore waters(within 20 km from the coastline)prone to terrestrial influence.(1)Compared to the status before the action began(2011–2017),majority(87.3%)of the nearshore waters turned clear during the action implementation period(2018–2020),characterized by the elevated Z_(SD)by 11.6%±12.1%.(2)Nevertheless,the improvement was not spatially uniform,with higher Z_(SD)improvement in provinces of Hebei,Liaoning,and Shandong(13.2%±16.5%,13.2%±11.6%,10.8%±10.2%,respectively)followed by Tianjin(6.2%±4.7%).(3)Bayesian trend analysis found the abrupt Z_(SD)improvement in April 2018,which coincided with the initiation of UBIBSM,implying the water quality response to pollution control.More importantly,the independent statistics of land-based pollutant discharge also indicated that the significant reduction of terrestrial pollutant input during the UBIBSM action was the main driver of observed Z_(SD)improvement.(4)Compared with previous pollution control actions in the BS,UBIBSM was found to be the most successful one during the past 20 years,in terms of transparency improvement over nearshore waters.The presented results proved the UBIBSM-achieved remarkable water quality improvement,taking the advantage of long-term consistent and objective data record from satellite ocean color observation.展开更多
大气^(210)Po、^(210)Bi和^(210)Pb的沉降通量是海洋中核素示踪颗粒物动力学过程(颗粒有机碳输出、颗粒物输运)的基础参数,为揭示我国近海地区^(210)Po、^(210)Bi和^(210)Pb活度浓度的时空变化规律并估算其沉降入海通量,本文于2016年9...大气^(210)Po、^(210)Bi和^(210)Pb的沉降通量是海洋中核素示踪颗粒物动力学过程(颗粒有机碳输出、颗粒物输运)的基础参数,为揭示我国近海地区^(210)Po、^(210)Bi和^(210)Pb活度浓度的时空变化规律并估算其沉降入海通量,本文于2016年9月至翌年2月和2021年9-11月分别对上海及厦门地区近地表大气气溶胶中^(210)Po、^(210)Pb和^(210)Bi的活度浓度进行了连续观测;基于^(210)Po-^(210)Pb活度比(^(210)Po/^(210)Pb)和^(210)Bi-^(210)Pb活度比(^(210)Bi/^(210)Pb)两种示踪法计算了气溶胶颗粒物的滞留时间,并利用一维简单气溶胶沉降速率模型估算了3种核素以大气沉降方式输入东海的通量。结果显示,2016年上海秋、冬两季^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.11~1.27 m Bq/m^(3)、0.45~1.83 m Bq/m^(3)和1.12~6.10 m Bq/m^(3);2021年秋季厦门^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.05~0.85 m Bq/m^(3)、0.83~2.52 m Bq/m^(3)和0.17~1.32 m Bq/m^(3),上海近地表气溶胶中3种核素的活度浓度秋季平均值比厦门地区高。利用^(210)Po/^(210)Pb和^(210)Bi/^(210)Pb计算得到上海和厦门近地面大气的气溶胶滞留时间存在显著差异,基于^(210)Po/^(210)Pb计算上海气溶胶滞留时间均值为(94±54)d,基于^(210)Bi/^(210)Pb计算上海气溶胶滞留时间均值为(6.4±4.8)d,造成这种差异的原因很可能是两种示踪法本身具有的系统性差异。本文基于一维简易气溶胶沉降速率模型估算了上海地区的^(210)Pb、^(210)Bi和^(210)Po的大气沉降入东海的通量,其在秋季期间的变化范围分别为0.1~26.35 Bq/(m^(2)·d)、0.04~7.91 Bq/(m^(2)·d)和0.01~5.49 Bq/(m^(2)·d)。基于模型估算的^(210)Po、^(210)Bi和^(210)Pb沉降通量与研究区域的实际观测值接近一致,表明利用一维简易气溶胶沉降速率模型间接估算法在替代观测站直测核素的沉降入海通量方面具有一定可行性。展开更多
Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those...Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those traps were formed is not clear, which inhibits further exploration for this type of reservoir. In order to solve the problem, we take as an example nearshore subaqueous fans in the upper part of the fourth member of the Shahejie Formation (Es4s) on the north slope of the Minfeng Subsag in the Dongying Sag. Combining different research methods, such as core observation, thin section examination, scanning electron microscope (SEM) observation, fluid-inclusion analysis, carbon and oxygen isotope analysis of carbonate cements, and analysis of core properties, we studied the genetic mechanisms of diagenetic traps on the basis of diagenetic environment evolution and diagenetic evolution sequence in different sub/micro-facies. Conglomerate in Es4s in the north Minfeng Subsag experienced several periods of transition between alkaline and acidic environments as "alkaline-acidic-alkaline-acidic-weak alkaline". As a result, dissolution and cementation are also very complex, and the sequence is "early pyrite cementation / siderite cementation / gypsum cementation / calcite and dolomite cementation- feldspar dissolution / quartz overgrowth quartz dissolution / ferroan calcite cementation / ankerite cementation / lime-mud matrix recrystallization / feldspar overgrowth carbonate dissolution / feldspar dissolution / quartz overgrowth / pyrite cementation". The difference in sedimentary characteristics between different sub/micro-facies of nearshore subaqueous fans controls diagenetic characteristics. Inner fan conglomerates mainly experienced compaction and lime-mud matrix recrystallization, with weak dissolution, which led to a reduction in the porosity and permeability crucial to reservoir formation. Lime-mud matrix recrystallization results in a rapid decrease in porosity and permeability in inner fan conglomerates in middle-to-deep layers. Because acid dissolution reworks reservoirs and hydrocarbon filling inhibits cementation, reservoirs far from mudstone layers in middle fan braided channels develop a great number of primary pores and secondary pores, and are good enough to be effective reservoirs of hydrocarbon. With the increase of burial depth, both the decrease of porosity and permeability of inner fan conglomerates and the increase of the physical property difference between inner fans and middle fans enhance the quality of seals in middle-to-deep layers. As a result, inner fan conglomerates can be sealing layers in middle-to-deep buried layers. Reservoirs adjacent to mudstones in middle fan braided channels and reservoirs in middle fan interdistributaries experienced extensive cementation, and tight cemented crusts formed at both the top and bottom of conglomerates, which can then act as cap rocks. In conclusion, diagenetic traps in conglomerates of nearshore subaqueous fans could be developed with inner fan conglomerates as lateral or vertical sealing layers, tight carbonate crusts near mudstone layers in middle fan braided channels as well as lacustrine mudstones as cap rocks, and conglomerates far from mudstone layers in middle fan braided channels as reservoirs. Lime-mud matrix recrystallization of inner fan conglomerates and carbonate cementation of conglomerates adjacent to mudstone layers in middle fan braided channels took place from 32 Ma B.R to 24.6 Ma B.P., thus the formation of diagenetic traps was from 32 Ma B.R to 24.6 Ma B.R and diagenetic traps have a better hydrocarbon sealing ability from 24 Ma B.P.. The sealing ability of inner fans gradually increases with the increase of burial depth and diagenetic traps buried more than 3,200 m have better seals.展开更多
A three-dimensional nearshore circulation model was developed by coupling CH3D, a three-dimensional hydrodynamic model and REF/DIF, a nearshore wave transformation model. The model solves the three-dimensional wave-av...A three-dimensional nearshore circulation model was developed by coupling CH3D, a three-dimensional hydrodynamic model and REF/DIF, a nearshore wave transformation model. The model solves the three-dimensional wave-averaged equations of motion. Wave-induced effects on circulation were introduced in the form of radiation stresses, wave-induced mass transport, wave-induced enhancement of bottom friction and wave-induced turbulent mixing. Effects of breaking waves were considered following Svendsen (1984a and 1984b) and Stive and Wind (1986). The model was successfully tested against the analytical solution of longshore currents by Longuet and Higgins (1970). The model successfully simulated the undertow as observed in a laboratory experiment by Stive and Wind (1982). In addition, the model was applied to a physical model by Mory and Hamm (1997) and successfully reproduced the eddy behind a detached breakwater as well as the longshore current on the open beach and the contiguous eddy in the open area of the wave tank. While the qualitative agreement between model results and experimental observations was very good, the quantitative agreement needs to be further improved. Albeit difficult to explain every discrepancy between the model results and observations, in general, sources of errors are attributed to the lack of understanding and comprehensive description of following processes: (1)the horizontal and vertical distribution of radiation stress, especially for breaking waves;(2)the detailed structure of turbulence;(3)Wave-current interaction (not included at this moment); and (4)the wave-current boundary layer and the resulting bottom shear stress.展开更多
Nearshore wind speeds retrieved by WindSat are validated by a comparison with the moored buoy observations near the U.S. west and east coasts. A 30 min and 25 km collection window is used for the WindSat wind data and...Nearshore wind speeds retrieved by WindSat are validated by a comparison with the moored buoy observations near the U.S. west and east coasts. A 30 min and 25 km collection window is used for the WindSat wind data and buoy measurements from ]anuary 2004 to December 2014. Comparisons show that the overall root-mean-square error is better than 1.44 m/s near the U.S. coasts, and the result for the east coast is better than that for the west coast. The retrieval accuracy of the descending portions is slightly better than that of the ascending portions. Most buoy-to-buoy variations are not significantly correlated with the coastal topography, the longitude and the distance from the shore or satellite-buoy separation distance. In addition, comparisons between a polarimetric microwave radiometer and a microwave scatterometer are accomplished with the nearshore buoy observations from 2007 to 2008. The WindSat-derived winds tend to be lower than the buoy observations near the U.S. coasts. In contrast, the QuikSCAT-derived winds tend to be higher than the buoy observations. Overall, the retrieval accuracy of WindSat is slightly better than that of QuikSCAT, and these satellite-derived winds are sufficiently accurate for scientific studies.展开更多
The offshore turbine system was installed on a floating platform moored in Hakata Bay, offshore of Fukuoka, Japan. An identical turbine system was also installed at the adjacent waterfront. The separation of the two t...The offshore turbine system was installed on a floating platform moored in Hakata Bay, offshore of Fukuoka, Japan. An identical turbine system was also installed at the adjacent waterfront. The separation of the two turbines was 3.7 km. Wind flow tends to be more stable and the average wind speed is often larger in offshore areas than adjacent land areas at typical wind turbine hub height. This study focused on the wind condition of a nearshore area to clarify the advantages of nearshore wind farming. Prior to field experiment, wind conditions were predicted by using numerical simulation. It is useful for estimating topographical effect in nearshore areas. Next, field verification test was done by directly comparing wind data obtained from the identical wind turbine systems installed at an offshore location and the adjacent waterfront over the same extended period. The corresponding power output of these turbines was also compared. The data set exhibits 23% larger annual average wind speed at the offshore location and smaller turbulent intensity, resulting doubled annual power production.展开更多
Satellite remote sensing technique offers a wide range of information, and is one of the tools for ocean wave observation. This paper discusses the limitations of Synthetic Aperture Radar (SAR) images in wave field an...Satellite remote sensing technique offers a wide range of information, and is one of the tools for ocean wave observation. This paper discusses the limitations of Synthetic Aperture Radar (SAR) images in wave field analysis. It is found that the wave field analysis is affected by the gray value distribution of image and the relationship between satellite travel and wave propagation directions. Since human activities and coastal engineering are performed in nearshore areas, some issues are discussed for nearshore SAR image analysis. Several case studies show that the wave parameters estimated from nearshore SAR images are quite different from in situ measurements, suggesting that the wave information derived from nearshore SAR images cannot appropriately represent the wave characteristics. One of the reasons is that the wave field is non homogeneous in the nearshore area.展开更多
In 1994,Townend proposed a method to calculate the relative changes in various wave characteristics and structure-related parameters due to sea level rise for regular waves.The method was extended to irregular waves b...In 1994,Townend proposed a method to calculate the relative changes in various wave characteristics and structure-related parameters due to sea level rise for regular waves.The method was extended to irregular waves by Cheon and Suh in 2016.In this study,this method is further extended to include the effect of future change in offshore wave height and the sea level rise.The relative changes in wavelength,refraction coefficient,shoaling coefficient,and wave height in nearshore area are presented as functions of the relative changes in water depth and offshore wave height.The calculated relative changes in wave characteristics are then used to estimate the effect of sea level rise and offshore wave height change on coastal structures by calculating the relative changes in wave run-up height,overtopping discharge,crest freeboard,and armor weight of the structures.The relative changes in wave characteristics and structure-related parameters are all expressed as a function of the relative water depth for various combinations of the relative changes in water depth and offshore wave height.展开更多
基金The fund supported by Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) under contract No. SML2021SP313the fundamental research funds for the Central Universities of Sun Yat-Sen University under contract No.23xkjc019the fund supported by China-Korea Joint Ocean Research Center of China under contract No. PI-2022-1-01
文摘The Bohai Sea(BS)is the unique semi-closed inland sea of China,characterized by degraded water quality due to significant terrestrial pollution input.In order to improve its water quality,a dedicated action named“Uphill Battles for Integrated Bohai Sea Management”(UBIBSM,2018–2020)was implemented by the Chinese government.To evaluate the action effectiveness toward water quality improvement,variability of the satelliteobserved water transparency(Secchi disk depth,Z_(SD))was explored,with special emphasis on the nearshore waters(within 20 km from the coastline)prone to terrestrial influence.(1)Compared to the status before the action began(2011–2017),majority(87.3%)of the nearshore waters turned clear during the action implementation period(2018–2020),characterized by the elevated Z_(SD)by 11.6%±12.1%.(2)Nevertheless,the improvement was not spatially uniform,with higher Z_(SD)improvement in provinces of Hebei,Liaoning,and Shandong(13.2%±16.5%,13.2%±11.6%,10.8%±10.2%,respectively)followed by Tianjin(6.2%±4.7%).(3)Bayesian trend analysis found the abrupt Z_(SD)improvement in April 2018,which coincided with the initiation of UBIBSM,implying the water quality response to pollution control.More importantly,the independent statistics of land-based pollutant discharge also indicated that the significant reduction of terrestrial pollutant input during the UBIBSM action was the main driver of observed Z_(SD)improvement.(4)Compared with previous pollution control actions in the BS,UBIBSM was found to be the most successful one during the past 20 years,in terms of transparency improvement over nearshore waters.The presented results proved the UBIBSM-achieved remarkable water quality improvement,taking the advantage of long-term consistent and objective data record from satellite ocean color observation.
文摘大气^(210)Po、^(210)Bi和^(210)Pb的沉降通量是海洋中核素示踪颗粒物动力学过程(颗粒有机碳输出、颗粒物输运)的基础参数,为揭示我国近海地区^(210)Po、^(210)Bi和^(210)Pb活度浓度的时空变化规律并估算其沉降入海通量,本文于2016年9月至翌年2月和2021年9-11月分别对上海及厦门地区近地表大气气溶胶中^(210)Po、^(210)Pb和^(210)Bi的活度浓度进行了连续观测;基于^(210)Po-^(210)Pb活度比(^(210)Po/^(210)Pb)和^(210)Bi-^(210)Pb活度比(^(210)Bi/^(210)Pb)两种示踪法计算了气溶胶颗粒物的滞留时间,并利用一维简单气溶胶沉降速率模型估算了3种核素以大气沉降方式输入东海的通量。结果显示,2016年上海秋、冬两季^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.11~1.27 m Bq/m^(3)、0.45~1.83 m Bq/m^(3)和1.12~6.10 m Bq/m^(3);2021年秋季厦门^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.05~0.85 m Bq/m^(3)、0.83~2.52 m Bq/m^(3)和0.17~1.32 m Bq/m^(3),上海近地表气溶胶中3种核素的活度浓度秋季平均值比厦门地区高。利用^(210)Po/^(210)Pb和^(210)Bi/^(210)Pb计算得到上海和厦门近地面大气的气溶胶滞留时间存在显著差异,基于^(210)Po/^(210)Pb计算上海气溶胶滞留时间均值为(94±54)d,基于^(210)Bi/^(210)Pb计算上海气溶胶滞留时间均值为(6.4±4.8)d,造成这种差异的原因很可能是两种示踪法本身具有的系统性差异。本文基于一维简易气溶胶沉降速率模型估算了上海地区的^(210)Pb、^(210)Bi和^(210)Po的大气沉降入东海的通量,其在秋季期间的变化范围分别为0.1~26.35 Bq/(m^(2)·d)、0.04~7.91 Bq/(m^(2)·d)和0.01~5.49 Bq/(m^(2)·d)。基于模型估算的^(210)Po、^(210)Bi和^(210)Pb沉降通量与研究区域的实际观测值接近一致,表明利用一维简易气溶胶沉降速率模型间接估算法在替代观测站直测核素的沉降入海通量方面具有一定可行性。
基金co-funded by the National Natural Science Foundation of China (41102058)the National Science and Technology Special Grant (2011ZX05006-003)the Fundamental Research Funds for the Central Universities (12CX04001A)
文摘Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those traps were formed is not clear, which inhibits further exploration for this type of reservoir. In order to solve the problem, we take as an example nearshore subaqueous fans in the upper part of the fourth member of the Shahejie Formation (Es4s) on the north slope of the Minfeng Subsag in the Dongying Sag. Combining different research methods, such as core observation, thin section examination, scanning electron microscope (SEM) observation, fluid-inclusion analysis, carbon and oxygen isotope analysis of carbonate cements, and analysis of core properties, we studied the genetic mechanisms of diagenetic traps on the basis of diagenetic environment evolution and diagenetic evolution sequence in different sub/micro-facies. Conglomerate in Es4s in the north Minfeng Subsag experienced several periods of transition between alkaline and acidic environments as "alkaline-acidic-alkaline-acidic-weak alkaline". As a result, dissolution and cementation are also very complex, and the sequence is "early pyrite cementation / siderite cementation / gypsum cementation / calcite and dolomite cementation- feldspar dissolution / quartz overgrowth quartz dissolution / ferroan calcite cementation / ankerite cementation / lime-mud matrix recrystallization / feldspar overgrowth carbonate dissolution / feldspar dissolution / quartz overgrowth / pyrite cementation". The difference in sedimentary characteristics between different sub/micro-facies of nearshore subaqueous fans controls diagenetic characteristics. Inner fan conglomerates mainly experienced compaction and lime-mud matrix recrystallization, with weak dissolution, which led to a reduction in the porosity and permeability crucial to reservoir formation. Lime-mud matrix recrystallization results in a rapid decrease in porosity and permeability in inner fan conglomerates in middle-to-deep layers. Because acid dissolution reworks reservoirs and hydrocarbon filling inhibits cementation, reservoirs far from mudstone layers in middle fan braided channels develop a great number of primary pores and secondary pores, and are good enough to be effective reservoirs of hydrocarbon. With the increase of burial depth, both the decrease of porosity and permeability of inner fan conglomerates and the increase of the physical property difference between inner fans and middle fans enhance the quality of seals in middle-to-deep layers. As a result, inner fan conglomerates can be sealing layers in middle-to-deep buried layers. Reservoirs adjacent to mudstones in middle fan braided channels and reservoirs in middle fan interdistributaries experienced extensive cementation, and tight cemented crusts formed at both the top and bottom of conglomerates, which can then act as cap rocks. In conclusion, diagenetic traps in conglomerates of nearshore subaqueous fans could be developed with inner fan conglomerates as lateral or vertical sealing layers, tight carbonate crusts near mudstone layers in middle fan braided channels as well as lacustrine mudstones as cap rocks, and conglomerates far from mudstone layers in middle fan braided channels as reservoirs. Lime-mud matrix recrystallization of inner fan conglomerates and carbonate cementation of conglomerates adjacent to mudstone layers in middle fan braided channels took place from 32 Ma B.R to 24.6 Ma B.P., thus the formation of diagenetic traps was from 32 Ma B.R to 24.6 Ma B.R and diagenetic traps have a better hydrocarbon sealing ability from 24 Ma B.P.. The sealing ability of inner fans gradually increases with the increase of burial depth and diagenetic traps buried more than 3,200 m have better seals.
文摘A three-dimensional nearshore circulation model was developed by coupling CH3D, a three-dimensional hydrodynamic model and REF/DIF, a nearshore wave transformation model. The model solves the three-dimensional wave-averaged equations of motion. Wave-induced effects on circulation were introduced in the form of radiation stresses, wave-induced mass transport, wave-induced enhancement of bottom friction and wave-induced turbulent mixing. Effects of breaking waves were considered following Svendsen (1984a and 1984b) and Stive and Wind (1986). The model was successfully tested against the analytical solution of longshore currents by Longuet and Higgins (1970). The model successfully simulated the undertow as observed in a laboratory experiment by Stive and Wind (1982). In addition, the model was applied to a physical model by Mory and Hamm (1997) and successfully reproduced the eddy behind a detached breakwater as well as the longshore current on the open beach and the contiguous eddy in the open area of the wave tank. While the qualitative agreement between model results and experimental observations was very good, the quantitative agreement needs to be further improved. Albeit difficult to explain every discrepancy between the model results and observations, in general, sources of errors are attributed to the lack of understanding and comprehensive description of following processes: (1)the horizontal and vertical distribution of radiation stress, especially for breaking waves;(2)the detailed structure of turbulence;(3)Wave-current interaction (not included at this moment); and (4)the wave-current boundary layer and the resulting bottom shear stress.
基金The National Natural Science Foundation of China under contract Nos 41105012 and 41576171
文摘Nearshore wind speeds retrieved by WindSat are validated by a comparison with the moored buoy observations near the U.S. west and east coasts. A 30 min and 25 km collection window is used for the WindSat wind data and buoy measurements from ]anuary 2004 to December 2014. Comparisons show that the overall root-mean-square error is better than 1.44 m/s near the U.S. coasts, and the result for the east coast is better than that for the west coast. The retrieval accuracy of the descending portions is slightly better than that of the ascending portions. Most buoy-to-buoy variations are not significantly correlated with the coastal topography, the longitude and the distance from the shore or satellite-buoy separation distance. In addition, comparisons between a polarimetric microwave radiometer and a microwave scatterometer are accomplished with the nearshore buoy observations from 2007 to 2008. The WindSat-derived winds tend to be lower than the buoy observations near the U.S. coasts. In contrast, the QuikSCAT-derived winds tend to be higher than the buoy observations. Overall, the retrieval accuracy of WindSat is slightly better than that of QuikSCAT, and these satellite-derived winds are sufficiently accurate for scientific studies.
文摘The offshore turbine system was installed on a floating platform moored in Hakata Bay, offshore of Fukuoka, Japan. An identical turbine system was also installed at the adjacent waterfront. The separation of the two turbines was 3.7 km. Wind flow tends to be more stable and the average wind speed is often larger in offshore areas than adjacent land areas at typical wind turbine hub height. This study focused on the wind condition of a nearshore area to clarify the advantages of nearshore wind farming. Prior to field experiment, wind conditions were predicted by using numerical simulation. It is useful for estimating topographical effect in nearshore areas. Next, field verification test was done by directly comparing wind data obtained from the identical wind turbine systems installed at an offshore location and the adjacent waterfront over the same extended period. The corresponding power output of these turbines was also compared. The data set exhibits 23% larger annual average wind speed at the offshore location and smaller turbulent intensity, resulting doubled annual power production.
文摘Satellite remote sensing technique offers a wide range of information, and is one of the tools for ocean wave observation. This paper discusses the limitations of Synthetic Aperture Radar (SAR) images in wave field analysis. It is found that the wave field analysis is affected by the gray value distribution of image and the relationship between satellite travel and wave propagation directions. Since human activities and coastal engineering are performed in nearshore areas, some issues are discussed for nearshore SAR image analysis. Several case studies show that the wave parameters estimated from nearshore SAR images are quite different from in situ measurements, suggesting that the wave information derived from nearshore SAR images cannot appropriately represent the wave characteristics. One of the reasons is that the wave field is non homogeneous in the nearshore area.
基金National Research Foundation of Korea(NRF)funded by Korea Ministry of Science,ICT and Future Planning(NRF-2014R1A2A2A01007921)
文摘In 1994,Townend proposed a method to calculate the relative changes in various wave characteristics and structure-related parameters due to sea level rise for regular waves.The method was extended to irregular waves by Cheon and Suh in 2016.In this study,this method is further extended to include the effect of future change in offshore wave height and the sea level rise.The relative changes in wavelength,refraction coefficient,shoaling coefficient,and wave height in nearshore area are presented as functions of the relative changes in water depth and offshore wave height.The calculated relative changes in wave characteristics are then used to estimate the effect of sea level rise and offshore wave height change on coastal structures by calculating the relative changes in wave run-up height,overtopping discharge,crest freeboard,and armor weight of the structures.The relative changes in wave characteristics and structure-related parameters are all expressed as a function of the relative water depth for various combinations of the relative changes in water depth and offshore wave height.