2014 Vol. 36, No. 11
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2014, 36(11): 1-11.
doi: 10.3969/j.issn.0253-4193.2014.11.001
Abstract:
Using high resolution data,the surface current variation within half-year time scale in active region of the Kuroshio in East China Sea is studied in this paper. The major results are as follows: (1) The northeast Taiwan area and near Tokara Strait region are two regions with the most remarkable variation of the surface current of Kuroshio in East China Sea (ECS). (2) There are the surface current variations within half-year time scale in two regions,the quasi-periodic transformation between anomalous cyclonic vortex and anomalous anticyclonic vortex is basic feature of the surface current variation. The spectrum peaks of the quasi-periodic transformation are mainly at 50 to 70 days and 90 to 140 days.(3)The actions of anomalous cyclonic vortex and anomalous anticyclonic vortex are closely related to the current axle variations of the Kuroshio in East China Sea,the action of anomalous cyclonic vortex (anticyclonic vortex) is accompanied with the flinching to southeast (the pushing on northwestwards) of the Kuroshio current axle. (4) In northeast of Taiwan area,the 50 to 70 days oscillation of the Kuroshio in East China Sea is mainly originated from the Kuroshio mesoscale fluctuation; the 90 to 140 days oscillation is mainly influenced by the mesoscale eddies from east of Taiwan. Analogously,the 50 to 70 days oscillation of the Kuroshio in East China Sea is mainly originated from the Kuroshio mesoscale fluctuation at upper reaches of the Kuroshio; the 90 to 140 days oscillation is mainly influenced by the mesoscale eddies from east of the Pyukyu gunto.
Using high resolution data,the surface current variation within half-year time scale in active region of the Kuroshio in East China Sea is studied in this paper. The major results are as follows: (1) The northeast Taiwan area and near Tokara Strait region are two regions with the most remarkable variation of the surface current of Kuroshio in East China Sea (ECS). (2) There are the surface current variations within half-year time scale in two regions,the quasi-periodic transformation between anomalous cyclonic vortex and anomalous anticyclonic vortex is basic feature of the surface current variation. The spectrum peaks of the quasi-periodic transformation are mainly at 50 to 70 days and 90 to 140 days.(3)The actions of anomalous cyclonic vortex and anomalous anticyclonic vortex are closely related to the current axle variations of the Kuroshio in East China Sea,the action of anomalous cyclonic vortex (anticyclonic vortex) is accompanied with the flinching to southeast (the pushing on northwestwards) of the Kuroshio current axle. (4) In northeast of Taiwan area,the 50 to 70 days oscillation of the Kuroshio in East China Sea is mainly originated from the Kuroshio mesoscale fluctuation; the 90 to 140 days oscillation is mainly influenced by the mesoscale eddies from east of Taiwan. Analogously,the 50 to 70 days oscillation of the Kuroshio in East China Sea is mainly originated from the Kuroshio mesoscale fluctuation at upper reaches of the Kuroshio; the 90 to 140 days oscillation is mainly influenced by the mesoscale eddies from east of the Pyukyu gunto.
2014, 36(11): 12-20.
doi: 10.3969/j.issn.0253-4193.2014.11.002
Abstract:
The largest tidal range 9.39 m was observed on October 17, 2012 at Xintiaoyugang station which is one of 4 tide-gauge stations along coast of the radial sand ridges, southern Yellow Sea. It confirms that the historical tidal range 9.28 m in Xiaoyangkou in 1980's is reliable and the largest tidal range record in this sea area is renewed. Reasons of the largest tidal range are expressed from two aspects. One is "movable standing tidal wave" that is the hydrodynamic cause by hydrodynamic simulation modeling. The other is "the water diversion"(Erfenshui) that is the dynamic geomorphic reason by remote sensing interpretation. As the results, "Jump Rope" effect of the synchronous water level along Tiaozini tidal flat and the largest tidal range of 9.39 m is reasonable and effective. Even more, the maximum tidal range in this area could be 9.62 m if statistical method can be changed. The largest tidal range of radial sand ridges in this paper has reference value and innovation of the tidal characteristics in the whole coast of China.
The largest tidal range 9.39 m was observed on October 17, 2012 at Xintiaoyugang station which is one of 4 tide-gauge stations along coast of the radial sand ridges, southern Yellow Sea. It confirms that the historical tidal range 9.28 m in Xiaoyangkou in 1980's is reliable and the largest tidal range record in this sea area is renewed. Reasons of the largest tidal range are expressed from two aspects. One is "movable standing tidal wave" that is the hydrodynamic cause by hydrodynamic simulation modeling. The other is "the water diversion"(Erfenshui) that is the dynamic geomorphic reason by remote sensing interpretation. As the results, "Jump Rope" effect of the synchronous water level along Tiaozini tidal flat and the largest tidal range of 9.39 m is reasonable and effective. Even more, the maximum tidal range in this area could be 9.62 m if statistical method can be changed. The largest tidal range of radial sand ridges in this paper has reference value and innovation of the tidal characteristics in the whole coast of China.
2014, 36(11): 21-29.
doi: 10.3969/j.issn.0253-4193.2014.11.003
Abstract:
Combining the Satellite altimeter data and SODA temperature-salinity data,in this paper we have simulated the long-term trends and the spatial distribution of the sea level of South China Sea (SCS) during the 21st century with the POP model. The forcing field of the POP model is the predicted global simulation results of CCSM4 (Community Climate System Model version4) model under the Representative Concentration Pathways Scenarios (RCP4.5). The simulated results show that the average sea level in the last ten years of 21st century of the South China Sea would rise by 15 to 39 cm compared to that in the last ten years of 20th century. The significant sea level increase would locate in areas such as the eastern and southeastern of Indo-China Peninsula,and the east and west sides of Luzon Strait. The maximum rise could reach up to 39 cm. If the influence of the melting glaciers such as Greenland sheet and Antarctica sheet was considered,the total rise of the south China sea level during the 21st century could reach 35 to 75 cm. The significant increase of the steric sea level would locate in areas such as the deep-water basin in the east of Luson Island,the waters between the Guangdong Coastal Current and Luzon Cold Eddy and the southeastern of Indo-China Peninsula. The total steric sea level change mainly came from thermal steric sea level,while the contribution of halo steric was small. The steric sea level rise rate was relatively low in the southern and western of South China Sea,e.g. a downward trend was shown on the northwest of Kalimantan Island,in the gulf of Thailand and on the west of Hainan Island.
Combining the Satellite altimeter data and SODA temperature-salinity data,in this paper we have simulated the long-term trends and the spatial distribution of the sea level of South China Sea (SCS) during the 21st century with the POP model. The forcing field of the POP model is the predicted global simulation results of CCSM4 (Community Climate System Model version4) model under the Representative Concentration Pathways Scenarios (RCP4.5). The simulated results show that the average sea level in the last ten years of 21st century of the South China Sea would rise by 15 to 39 cm compared to that in the last ten years of 20th century. The significant sea level increase would locate in areas such as the eastern and southeastern of Indo-China Peninsula,and the east and west sides of Luzon Strait. The maximum rise could reach up to 39 cm. If the influence of the melting glaciers such as Greenland sheet and Antarctica sheet was considered,the total rise of the south China sea level during the 21st century could reach 35 to 75 cm. The significant increase of the steric sea level would locate in areas such as the deep-water basin in the east of Luson Island,the waters between the Guangdong Coastal Current and Luzon Cold Eddy and the southeastern of Indo-China Peninsula. The total steric sea level change mainly came from thermal steric sea level,while the contribution of halo steric was small. The steric sea level rise rate was relatively low in the southern and western of South China Sea,e.g. a downward trend was shown on the northwest of Kalimantan Island,in the gulf of Thailand and on the west of Hainan Island.
2014, 36(11): 30-37.
doi: 10.3969/j.issn.0253-4193.2014.11.004
Abstract:
High-resolution storm surge forecast is one of the newest trends in the field of storm surge forecast. In this paper,a new high-resolution forecast model that covered the whole China's coastal areas was constructed,which have overcome the drawback of previous sub-regional numerical forecast model. The grid resolution near coastal areas was about 300 meters. Parallel computation was employed. The accuracy and computation time met the requirements of operational forecast through the numerical tests of typical typhoon storm surge in 2012 and 2013. 24 hours typhoon forecasts of Five agencies were also utilized to carry out the tests. The results showed that the most accurate storm surge forecast result is obtained according to China Meteorological Administration's typhoon forecast in 2013. The conclusion provided an important reference for the future storm surge forecast.
High-resolution storm surge forecast is one of the newest trends in the field of storm surge forecast. In this paper,a new high-resolution forecast model that covered the whole China's coastal areas was constructed,which have overcome the drawback of previous sub-regional numerical forecast model. The grid resolution near coastal areas was about 300 meters. Parallel computation was employed. The accuracy and computation time met the requirements of operational forecast through the numerical tests of typical typhoon storm surge in 2012 and 2013. 24 hours typhoon forecasts of Five agencies were also utilized to carry out the tests. The results showed that the most accurate storm surge forecast result is obtained according to China Meteorological Administration's typhoon forecast in 2013. The conclusion provided an important reference for the future storm surge forecast.
2014, 36(11): 38-45.
doi: 10.3969/j.issn.0253-4193.2014.11.005
Abstract:
In recent years,the area of sea ice have been substantially reduced in the Arctic Ocean. The reason behind this is still in debate. Based on the data of hydrology and remote sensing satellite from 2003 to 2011,the relationship of Pacific Water and sea ice in the Canada Basin were studied. Spatial distributions of potential temperature of Pacific Water and sea ice concentration in 2006 were compared with those in 2007. It was found that the warm Pacific Water anomalies entered the central Canada Basin in January to March 2007,which probably led to the melting of sea ice in the summer of 2007. Between 2003 and 2011,it was found that the potential temperature of Pacific Water and sea ice concentration were negatively correlated in the central Canada Basin. In August 2007,the spatial correlation was also found to be negative in the central Canada Basin. It might indicate that the inflow of warm Pacific Water anomalies transferred the heat upwardly. To a certain extent, the heat melted the sea ice and triggered the ice-albedo feedback,which resulted in the decline of sea ice area. Therefore,Pacific Summer Water,which travels through the Bering Strait into the Arctic Ocean,plays an important role in the reduction of sea ice area in the Arctic Ocean.
In recent years,the area of sea ice have been substantially reduced in the Arctic Ocean. The reason behind this is still in debate. Based on the data of hydrology and remote sensing satellite from 2003 to 2011,the relationship of Pacific Water and sea ice in the Canada Basin were studied. Spatial distributions of potential temperature of Pacific Water and sea ice concentration in 2006 were compared with those in 2007. It was found that the warm Pacific Water anomalies entered the central Canada Basin in January to March 2007,which probably led to the melting of sea ice in the summer of 2007. Between 2003 and 2011,it was found that the potential temperature of Pacific Water and sea ice concentration were negatively correlated in the central Canada Basin. In August 2007,the spatial correlation was also found to be negative in the central Canada Basin. It might indicate that the inflow of warm Pacific Water anomalies transferred the heat upwardly. To a certain extent, the heat melted the sea ice and triggered the ice-albedo feedback,which resulted in the decline of sea ice area. Therefore,Pacific Summer Water,which travels through the Bering Strait into the Arctic Ocean,plays an important role in the reduction of sea ice area in the Arctic Ocean.
2014, 36(11): 46-56.
doi: 10.3969/j.issn.0253-4193.2014.11.006
Abstract:
The effects of sea spray on the air-sea heat and momentum fluxes have been investigated using the data of Kuroshio extension buoy observation (KEO) and the satellite remote sensing during the passage of typhoon YAGI in the waters south of Japan in September 2006. Firstly,the effects of spray on the air-sea heat fluxes are analyzed quantitatively. The results show that the heat exchanges between the atmosphere and the ocean,especially the latent exchange,are significantly enhanced due to the existence of the spray during the typhoon passage. The impact of the spray on the heat fluxes is stronger with smaller wave age and bigger wind speed. Subsequently,the momentum analysis shows that the spray enhances the momentum transfer from the atmosphere to ocean during the typhoon passage. When the winds reach to the typhoon strength,the spray-induced momentum fluxes are comparable with the interfacial momentum. At such high wind speeds,the ultimate saturation suspension layer formed by the spray droplets in the surface layer can actually restrain the momentum exchange from wind to the sea surface and thus decrease the growth rate of the total momentum fluxes.
The effects of sea spray on the air-sea heat and momentum fluxes have been investigated using the data of Kuroshio extension buoy observation (KEO) and the satellite remote sensing during the passage of typhoon YAGI in the waters south of Japan in September 2006. Firstly,the effects of spray on the air-sea heat fluxes are analyzed quantitatively. The results show that the heat exchanges between the atmosphere and the ocean,especially the latent exchange,are significantly enhanced due to the existence of the spray during the typhoon passage. The impact of the spray on the heat fluxes is stronger with smaller wave age and bigger wind speed. Subsequently,the momentum analysis shows that the spray enhances the momentum transfer from the atmosphere to ocean during the typhoon passage. When the winds reach to the typhoon strength,the spray-induced momentum fluxes are comparable with the interfacial momentum. At such high wind speeds,the ultimate saturation suspension layer formed by the spray droplets in the surface layer can actually restrain the momentum exchange from wind to the sea surface and thus decrease the growth rate of the total momentum fluxes.
2014, 36(11): 57-63.
doi: 10.3969/j.issn.0253-4193.2014.11.007
Abstract:
Based on assumptions of layered media with equal time layer thickness,a model which can be used to compute the acoustic reflected echo of seawater thermohaline profile is built. The characteristics of the reflected echo of the seawater profile are analyzed in detail. The results are summarized as follows. The amplitude of the reflected echo changes where there is a variation in the thermohaline gradient. The amplitude of reflected echo is proportional to the change range of thermohaline gradient,and the polarity of the echo reflects the change trend of the gradient. The model is used in inversion experimentation of the vertical structure of ocean temperature and salinity. The model is verified by the measurements and overcomes the shortcomings of the previous inversion algorithm which does not facilitate the separation of density and velocity of sound.
Based on assumptions of layered media with equal time layer thickness,a model which can be used to compute the acoustic reflected echo of seawater thermohaline profile is built. The characteristics of the reflected echo of the seawater profile are analyzed in detail. The results are summarized as follows. The amplitude of the reflected echo changes where there is a variation in the thermohaline gradient. The amplitude of reflected echo is proportional to the change range of thermohaline gradient,and the polarity of the echo reflects the change trend of the gradient. The model is used in inversion experimentation of the vertical structure of ocean temperature and salinity. The model is verified by the measurements and overcomes the shortcomings of the previous inversion algorithm which does not facilitate the separation of density and velocity of sound.
2014, 36(11): 64-73.
doi: 10.3969/j.issn.0253-4193.2014.11.008
Abstract:
Traditional detection methods for sea ice are limited by the weather or the high cost of real-time detection. In order to achieve effective real-time detection of sea ice to prevent and mitigate the disaster,in this paper we have studied the possibility of using GPS reflected signals (GPS-R) technique to detect sea ice. We have analyzed the test data in February 2013,which is collected from the GPS signal receiver in the Bohai sea experiment in Tianjin of China. The result shows that the polarization ratio (the ratio of the direct RHCP signals and the reflected LHCP signals) could simulate sea ice concentration. This study is the first one among the domestic research to apply the GPS-R technology to the Bohai sea ice detection experiment.
Traditional detection methods for sea ice are limited by the weather or the high cost of real-time detection. In order to achieve effective real-time detection of sea ice to prevent and mitigate the disaster,in this paper we have studied the possibility of using GPS reflected signals (GPS-R) technique to detect sea ice. We have analyzed the test data in February 2013,which is collected from the GPS signal receiver in the Bohai sea experiment in Tianjin of China. The result shows that the polarization ratio (the ratio of the direct RHCP signals and the reflected LHCP signals) could simulate sea ice concentration. This study is the first one among the domestic research to apply the GPS-R technology to the Bohai sea ice detection experiment.
2014, 36(11): 74-84.
doi: 10.3969/j.issn.0253-4193.2014.11.009
Abstract:
To achieve the improved retrieval parameter of sea ice concentration(SIC) in the Bohai Sea,spectral characteristics of different types of sea ice are obtained and analyzed using in-situ ASD measurements in the Liaodong Bay. Appropriate threshold is thus determined for the retrieval of AVHRR data and then the SIC is calculated. In this paper,muti-band retrieval algorithm based on linear spectral mixture model (LSMM) is used for conducting a series of band experiments. The retrieved SIC using LandSat5-TM data is used to compare with the AVHRR SIC of different combinational algorithms. The results of error quantitative analysis indicate that the mean error (ME) of the algorithms involving band1 is positive,but the ME turns to negative when the algorithms involve band2 instead of band1; the ME of the algorithms which include both of two bands is less than the those which include only band1 or band2; among these algorithms,the 1245 joint-band algorithm has the minimum errors:it is concluded that the 1245 joint-band algorithm can be used for the retrieval of AVHRR SIC in the Bohai Sea.
To achieve the improved retrieval parameter of sea ice concentration(SIC) in the Bohai Sea,spectral characteristics of different types of sea ice are obtained and analyzed using in-situ ASD measurements in the Liaodong Bay. Appropriate threshold is thus determined for the retrieval of AVHRR data and then the SIC is calculated. In this paper,muti-band retrieval algorithm based on linear spectral mixture model (LSMM) is used for conducting a series of band experiments. The retrieved SIC using LandSat5-TM data is used to compare with the AVHRR SIC of different combinational algorithms. The results of error quantitative analysis indicate that the mean error (ME) of the algorithms involving band1 is positive,but the ME turns to negative when the algorithms involve band2 instead of band1; the ME of the algorithms which include both of two bands is less than the those which include only band1 or band2; among these algorithms,the 1245 joint-band algorithm has the minimum errors:it is concluded that the 1245 joint-band algorithm can be used for the retrieval of AVHRR SIC in the Bohai Sea.
2014, 36(11): 85-89.
doi: 10.3969/j.issn.0253-4193.2014.11.010
Abstract:
The advanced threshold method was selected for processing the Jason-1 geodetic mission waveform data based on the comparative analysis of four waveform retracking methods. Combined with the retracked ERS-1 and Geosat geodetic mission data,the along-track data were resampled at 2Hz to improve the spatial resolution of coastal areas. Considering the influence of sea surface topography after the data quality control process,a refined 1'×1' resolution gravity field of the China sea and its adjacent sea areas(0°~45°N,100°~140°E) was obtained by remove-restore method and Vening-Meinesz formula. The validation with shipborne data showed that the accuracy of inversion result is about 4 mGal and 10 mGal in open seas and shallow water areas,respectively. Moreover,the inversion result is better than both of the DTU10 model and the V21.1 model.
The advanced threshold method was selected for processing the Jason-1 geodetic mission waveform data based on the comparative analysis of four waveform retracking methods. Combined with the retracked ERS-1 and Geosat geodetic mission data,the along-track data were resampled at 2Hz to improve the spatial resolution of coastal areas. Considering the influence of sea surface topography after the data quality control process,a refined 1'×1' resolution gravity field of the China sea and its adjacent sea areas(0°~45°N,100°~140°E) was obtained by remove-restore method and Vening-Meinesz formula. The validation with shipborne data showed that the accuracy of inversion result is about 4 mGal and 10 mGal in open seas and shallow water areas,respectively. Moreover,the inversion result is better than both of the DTU10 model and the V21.1 model.
2014, 36(11): 90-100.
doi: 10.3969/j.issn.0253-4193.2014.11.011
Abstract:
The previous studies mainly focused on the structure of the basin,structural style and evolution in the northern margin of the South China Sea. Cenzoic magmatism in this region is less known,especially for the deepwater area. Based on the analysis and interpretation of many 2D seismic profiles,the igneous rocks can be divided into three regions,including the Qiongdongnan-Xisha Region,the Shenhu Region,the Dongsha Region. The occurrences in different regions have distinct differences. The igneous rocks of the Qiongdongnan-Xisha Region have an obvious rule of distribution controlled by the dextral Right-step pull-apart basin. The igneous rocks of the Shenhu Region are mainly located in the intersection of the NE and NW faults. There is a high correlation between the extensional stress field caused by the Dongsha Movement and the igneous rocks in the Dongsha Region. As a form of manifestation of internal geodynamics,the magmatism plays an important role in re-moulding the submarine surface topography. There is also an obvious relation among the magmatism,active faults,submarine landslides and shallow gas.
The previous studies mainly focused on the structure of the basin,structural style and evolution in the northern margin of the South China Sea. Cenzoic magmatism in this region is less known,especially for the deepwater area. Based on the analysis and interpretation of many 2D seismic profiles,the igneous rocks can be divided into three regions,including the Qiongdongnan-Xisha Region,the Shenhu Region,the Dongsha Region. The occurrences in different regions have distinct differences. The igneous rocks of the Qiongdongnan-Xisha Region have an obvious rule of distribution controlled by the dextral Right-step pull-apart basin. The igneous rocks of the Shenhu Region are mainly located in the intersection of the NE and NW faults. There is a high correlation between the extensional stress field caused by the Dongsha Movement and the igneous rocks in the Dongsha Region. As a form of manifestation of internal geodynamics,the magmatism plays an important role in re-moulding the submarine surface topography. There is also an obvious relation among the magmatism,active faults,submarine landslides and shallow gas.
2014, 36(11): 101-110.
doi: 10.3969/j.issn.0253-4193.2014.11.012
Abstract:
The Changjiang River discharges large amounts of fine-grained sediments into the East China Sea (ECS) each year. Fine-grained sediment transports far distance and spreads widely when it enter the continental shelf,which makes it an excellent archive to explore the source to sink of sediment from river to continental shelf. In this paper,the ICP-AES method was used to determine the concentration of heavy metals of fine-grained surface sediments of 44 samples collected in the Changjiang Estuary and its adjacent areas. The spatial distribution patterns,sedimentary fluxes,and source to sink of these elements were discussed. The results show: (1) the spatial distribution patterns and sedimentary fluxes of heavy metals in the area are similar,which have high values in the Changjiang Estuary and the inner mud shelf,decreasing dramatically in southeastern direction;(2) The heavy metals in the fine-grained sediments in the study areas mainly originate from the Changjiang River; then they disperse in two ways,one along the inner shelf outside the Zhe-Min coast,the other along the Changjiang River diluted water spreading area and into the outer continental shelf. Our results suggest that the sub-aquatic Changjiang River delta and the inner shelf of ECS are dominant sinks for the heavy metals from the Changjiang River.
The Changjiang River discharges large amounts of fine-grained sediments into the East China Sea (ECS) each year. Fine-grained sediment transports far distance and spreads widely when it enter the continental shelf,which makes it an excellent archive to explore the source to sink of sediment from river to continental shelf. In this paper,the ICP-AES method was used to determine the concentration of heavy metals of fine-grained surface sediments of 44 samples collected in the Changjiang Estuary and its adjacent areas. The spatial distribution patterns,sedimentary fluxes,and source to sink of these elements were discussed. The results show: (1) the spatial distribution patterns and sedimentary fluxes of heavy metals in the area are similar,which have high values in the Changjiang Estuary and the inner mud shelf,decreasing dramatically in southeastern direction;(2) The heavy metals in the fine-grained sediments in the study areas mainly originate from the Changjiang River; then they disperse in two ways,one along the inner shelf outside the Zhe-Min coast,the other along the Changjiang River diluted water spreading area and into the outer continental shelf. Our results suggest that the sub-aquatic Changjiang River delta and the inner shelf of ECS are dominant sinks for the heavy metals from the Changjiang River.
2014, 36(11): 111-119.
doi: 10.3969/j.issn.0253-4193.2014.11.013
Abstract:
In this paper we studied on two methods of seafloor deposition in-situ acoustic detection,i.e.,the transmission measurement and the refraction measurement,analyzed characteristics of 10 kinds of in-situ instruments of seafloor surface sediment acoustic measurement,and discussed the influence of different measurement techniques on the acoustic properties of seafloor sediment. Then,we compared the differences in obtained results between in-situ measurement and laboratorial measurement on the seafloor sediment of the Yellow Sea,analyzed the reason why the in-situ measurement data are generally smaller than laboratorial measurement results. Finally,we suggested that in-situ acoustic measurement is of importance on studying seafloor sediment,and the in-situ measurement techniques for other physical properties need to be improved to match the requirements of in-situ acoustic measurement of seafloor sediment.
In this paper we studied on two methods of seafloor deposition in-situ acoustic detection,i.e.,the transmission measurement and the refraction measurement,analyzed characteristics of 10 kinds of in-situ instruments of seafloor surface sediment acoustic measurement,and discussed the influence of different measurement techniques on the acoustic properties of seafloor sediment. Then,we compared the differences in obtained results between in-situ measurement and laboratorial measurement on the seafloor sediment of the Yellow Sea,analyzed the reason why the in-situ measurement data are generally smaller than laboratorial measurement results. Finally,we suggested that in-situ acoustic measurement is of importance on studying seafloor sediment,and the in-situ measurement techniques for other physical properties need to be improved to match the requirements of in-situ acoustic measurement of seafloor sediment.
2014, 36(11): 120-130.
doi: 10.3969/j.issn.0253-4193.2014.11.014
Abstract:
The experimental study on wave-driven longshore currents on barred beaches and numerical simulations which were based on wave energy conservation equation, were conducted to investigate the cross-shore distribution feature of velocity profiles of mean longshore currents, with emphasis on the second peak of longshore currents. The distribution feature of longshore currents has the velocity profile with bimodal characteristics. The larger one occurs on the middle part of lateral side of barred beaches and the smaller one is close to the shoreline, which corresponds to the first and second wave breaking respectively. The above features have been discussed by considering the effects of wave height, wave type and beach slope. The locations of two peaks and their ratio (i.e., higher one/smaller one) do not depend on wave type and wave height, but the location of barred beaches. Numerical simulations were also performed to compute the measured velocity profile with the emphasis on the effect of several factors such as lateral mixing, bottom friction and surface rollers on numerical results.
The experimental study on wave-driven longshore currents on barred beaches and numerical simulations which were based on wave energy conservation equation, were conducted to investigate the cross-shore distribution feature of velocity profiles of mean longshore currents, with emphasis on the second peak of longshore currents. The distribution feature of longshore currents has the velocity profile with bimodal characteristics. The larger one occurs on the middle part of lateral side of barred beaches and the smaller one is close to the shoreline, which corresponds to the first and second wave breaking respectively. The above features have been discussed by considering the effects of wave height, wave type and beach slope. The locations of two peaks and their ratio (i.e., higher one/smaller one) do not depend on wave type and wave height, but the location of barred beaches. Numerical simulations were also performed to compute the measured velocity profile with the emphasis on the effect of several factors such as lateral mixing, bottom friction and surface rollers on numerical results.
2014, 36(11): 131-141.
doi: 10.3969/j.issn.0253-4193.2014.11.015
Abstract:
Based on temporal variation of the simulated salinity and current direction,change of the isohaline and freshwater zone at flood slack and ebb slack,this study used the modified numerical 3-D model ECOM-si to analyze sources of saltwater intrusion at the water intake of Qingcaosha Reservoir under normal dynamic condition. The modeled results showed that saltwater-spill-over from the North Branch into the South Branch(SSO) accounts for 69.5%,89.3%,98.5% and 99.5% of the surface saltwater intrusion at the water intake of the Qingcaosha Reservoir during moderate tide following neap tide,spring tide,moderate tide following spring tide and neap tide,respectively,and 34.9%,88.9%,98.5%,99.5% of the bottom saltwater intrusion at the water intake of the reservoir during the same four-type tides mentioned above. Except for the bottom saltwater intrusion mainly from downstream open sea (accounts for 65.1%) during moderate tide following neap tide,the source of the saltwater intrusion at surface and bottom layer at the water intake of the reservoir is mainly from the SSO,especially during moderate tide following spring and neap tide.
Based on temporal variation of the simulated salinity and current direction,change of the isohaline and freshwater zone at flood slack and ebb slack,this study used the modified numerical 3-D model ECOM-si to analyze sources of saltwater intrusion at the water intake of Qingcaosha Reservoir under normal dynamic condition. The modeled results showed that saltwater-spill-over from the North Branch into the South Branch(SSO) accounts for 69.5%,89.3%,98.5% and 99.5% of the surface saltwater intrusion at the water intake of the Qingcaosha Reservoir during moderate tide following neap tide,spring tide,moderate tide following spring tide and neap tide,respectively,and 34.9%,88.9%,98.5%,99.5% of the bottom saltwater intrusion at the water intake of the reservoir during the same four-type tides mentioned above. Except for the bottom saltwater intrusion mainly from downstream open sea (accounts for 65.1%) during moderate tide following neap tide,the source of the saltwater intrusion at surface and bottom layer at the water intake of the reservoir is mainly from the SSO,especially during moderate tide following spring and neap tide.
2014, 36(11): 142-149.
doi: 10.3969/j.issn.0253-4193.2014.11.016
Abstract:
By using the in-situ measuring data, this study developed retrieval models of chlorophyll a (Chl a) and total suspended matter (TSM) for HJ-1 CCD data in the Yellow Sea based on the evolutionary modeling method. The terminal and function set of the evolutionary modeling method were designed to be adapted to retrieval of water constituents, and the transgene operator was employed to insert and maintain the prior knowledge. The average percentage difference (APD) for TSM was 31% (the correlation coefficient R2=0.96), and that for Chla was 33% (R2=0.88). The error sensitivity of the retrieval models was analyzed, and the output errors were generally less than ±10% when introducing ±5% error of remote sensing reflectance. Compared with neural network method, the evolutionary models have higher accuracy and simpler structures. In addition, in-situ data with different seasons was employed to validate the accuracy of the retrieval models. This study shows that the evolutionary modeling method is applicable for retrieval of water constituents from ocean color remote sensed data. Many explicit models with well accuracy and different structures could be obtained automatically, and they are of potential applications for hyperspectral data. Finally, we discussed how to improve the method in the near future.
By using the in-situ measuring data, this study developed retrieval models of chlorophyll a (Chl a) and total suspended matter (TSM) for HJ-1 CCD data in the Yellow Sea based on the evolutionary modeling method. The terminal and function set of the evolutionary modeling method were designed to be adapted to retrieval of water constituents, and the transgene operator was employed to insert and maintain the prior knowledge. The average percentage difference (APD) for TSM was 31% (the correlation coefficient R2=0.96), and that for Chla was 33% (R2=0.88). The error sensitivity of the retrieval models was analyzed, and the output errors were generally less than ±10% when introducing ±5% error of remote sensing reflectance. Compared with neural network method, the evolutionary models have higher accuracy and simpler structures. In addition, in-situ data with different seasons was employed to validate the accuracy of the retrieval models. This study shows that the evolutionary modeling method is applicable for retrieval of water constituents from ocean color remote sensed data. Many explicit models with well accuracy and different structures could be obtained automatically, and they are of potential applications for hyperspectral data. Finally, we discussed how to improve the method in the near future.
2014, 36(11): 150-162.
doi: 10.3969/j.issn.0253-4193.2014.11.017
Abstract:
Based on the measured current velocities and suspended sediment concentration data for the tidal channels between the radial sand ridges in the southwestern Yellow Sea,this study analyzed the mechanism of suspended sediment transport in the channels. The flow in the study area was rectilinear,and the suspended sediment concentration was relatively high. The decomposition of sediment fluxes suggested that the Eulerian effect and tidal trapping were the main factors affecting suspended sediment transport. In the Chenjiawu and Xiyang tidal channels,tidal trapping was a dominant mean for suspended sediment transport,and sediments were entrained from the channels by tides,which indicated the existence of the process of seabed scour. In contrast,the main controlling factor for suspended sediment transport in the Kushuiyang channel was the Eulerian effect,and the resuspended sediments were transported towards onshore by the strong tide flow and then piled up at Jiangjiasha and over shoal or intertidal areas on the western coast of Xiyang. Thus,under the circumstances for reducing terrigenous material input,sediments in the radial sand ridges became a new source of material supply and played an important role on the continued accretion of the sand ridges and the adjacent tidal flats.
Based on the measured current velocities and suspended sediment concentration data for the tidal channels between the radial sand ridges in the southwestern Yellow Sea,this study analyzed the mechanism of suspended sediment transport in the channels. The flow in the study area was rectilinear,and the suspended sediment concentration was relatively high. The decomposition of sediment fluxes suggested that the Eulerian effect and tidal trapping were the main factors affecting suspended sediment transport. In the Chenjiawu and Xiyang tidal channels,tidal trapping was a dominant mean for suspended sediment transport,and sediments were entrained from the channels by tides,which indicated the existence of the process of seabed scour. In contrast,the main controlling factor for suspended sediment transport in the Kushuiyang channel was the Eulerian effect,and the resuspended sediments were transported towards onshore by the strong tide flow and then piled up at Jiangjiasha and over shoal or intertidal areas on the western coast of Xiyang. Thus,under the circumstances for reducing terrigenous material input,sediments in the radial sand ridges became a new source of material supply and played an important role on the continued accretion of the sand ridges and the adjacent tidal flats.
2014, 36(11): 163-172.
doi: 10.3969/j.issn.0253-4193.2014.11.018
Abstract:
Shanghai harbor is to be built to an international shipping center,and needs deep-water harbor to meet the continuous increasing cargo transportation demands and larger vessels. Based on nautical charts during 2001 to 2008 and in-situ survey data obtained during 2011 to 2012, this paper discussed the feasibility of natural condition to build an artificial island outside the Changjiang Estuary. The results showed that the sea bed of the study area was stable,and its topography changed little from 2001 to 2008. Seven cross-section profiles showed that there was slight deposition in the upper part but erosion in the lower part, and the transforming depth from deposition to erosion was about -7 m to -10 m. The Hengsha East Shoal expands southeastwards due to the construction of north leading dike of the Changjiang Estuary deep-water navigation channel. The in-situ survey data showed that there was a rotary tidal current during the entire tide phase in winter,and the maximum current velocity was less than 188 cm/s during the flood of spring tide and no more than 134 cm/s during the ebb of neap. The residual current of the observation points showed some differences,e.g.,it was transported into the estuary outside of North Channel,and it was transported toward the sea outside of Northern Passage. The in-situ average suspended sediment concentration was 0.061 kg/m3 to 0.116 kg/m3, corresponding to neap tide and spring tide,respectively. Based on analytical data provided above,we suggested that the hydrodynamic condition and the suspended concentration outside the Changjiang Estuary were suitable to build an artificial island,and weak local siltation could be expected due to rotary tidal current at the east edge of the Hengsha east shoal in the Changjiang Estuary.
Shanghai harbor is to be built to an international shipping center,and needs deep-water harbor to meet the continuous increasing cargo transportation demands and larger vessels. Based on nautical charts during 2001 to 2008 and in-situ survey data obtained during 2011 to 2012, this paper discussed the feasibility of natural condition to build an artificial island outside the Changjiang Estuary. The results showed that the sea bed of the study area was stable,and its topography changed little from 2001 to 2008. Seven cross-section profiles showed that there was slight deposition in the upper part but erosion in the lower part, and the transforming depth from deposition to erosion was about -7 m to -10 m. The Hengsha East Shoal expands southeastwards due to the construction of north leading dike of the Changjiang Estuary deep-water navigation channel. The in-situ survey data showed that there was a rotary tidal current during the entire tide phase in winter,and the maximum current velocity was less than 188 cm/s during the flood of spring tide and no more than 134 cm/s during the ebb of neap. The residual current of the observation points showed some differences,e.g.,it was transported into the estuary outside of North Channel,and it was transported toward the sea outside of Northern Passage. The in-situ average suspended sediment concentration was 0.061 kg/m3 to 0.116 kg/m3, corresponding to neap tide and spring tide,respectively. Based on analytical data provided above,we suggested that the hydrodynamic condition and the suspended concentration outside the Changjiang Estuary were suitable to build an artificial island,and weak local siltation could be expected due to rotary tidal current at the east edge of the Hengsha east shoal in the Changjiang Estuary.
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