Surthce elevation is tile basic data for geo-science. It is difficult to retrieve tidal-flats＇ elevation from a single Re- mote Sensing （RS） image because of the complicated sediment dynanical environment and huge ...Surthce elevation is tile basic data for geo-science. It is difficult to retrieve tidal-flats＇ elevation from a single Re- mote Sensing （RS） image because of the complicated sediment dynanical environment and huge spatial difference in tidal-flats＇ moisture content. A Digital Elevation Model （DEM） construction method for inconstant inter-tidal zone based on high tempo-resolution MODIS data set in a short period is proposed in a ease study on the Dongsha Sandbank of the Jiangsu Radial Tidal Sand-ridges. In the present study, a batch-preprocessing method based on image partition to handle massive MODIS IB images is developed and applied to 8163 scenes of MODIS images. The dataset of short-period and muhi-temporal MODIS images for inter-tidal flats＇ DEM inversion is selected and the usability of MODIS dataset is analyzed. Shorelines of the Dongsha Sandbank are extracted by use of batch supervised classification. In accord with tidal- 0 level forecasted by the Chenjiawu Tidal Gauge Station at the overpass moment of each RS image, DEMs of inter-tidal flats in January and sutmner（Jul, Aug and Sept）, 2003 are built under ArcG1S9.2. Studies show that： （1） The dataset of short-duration and muhi-phase MODIS images can be used to retrieve the historical DEM of tidal-flats at changeful tidal flats. （2） Aualysis on usability of MODIS images from Aqua and Terra indicates that there are more usable and higbquality MODIS images in spring, autumn and winter, but less in summer. Therefore, the period for building inter-tidal fiats＇ DEM is suggested to be one month in spring, autumn and winter and three months in summer.展开更多
This study focuses on dynamic mechanism behind the formation of the freshwater zone around the Meimao Sandbank by use of 3D numerical simulation.The Meimao Sandbank is located along the southern bank of the South Pass...This study focuses on dynamic mechanism behind the formation of the freshwater zone around the Meimao Sandbank by use of 3D numerical simulation.The Meimao Sandbank is located along the southern bank of the South Passage in the Changjiang(Yangtze River) estuary,which is considered as a freshwater resource for Shanghai City.Interaction between runoff and tide is the main mechanism of the freshwater zone formation.However,the freshwater zone often suffers from saltwater intrusion in dry season.Tidal oscillation is stronger during spring tides,able to carry freshwater farther seaward.Therefore,it is more likely to occur during the ebb of a spring tide in dry seasons.In addition,the water zone is sensitive to runoff:when runoff decreases,it disappears,and vice versa.The northerly winds favor the formation of the freshwater zone.展开更多
Based upon the long-term observation of field data, a two-dimensional numerical model is applied to simulating the tidal flow covering from the neap tide to spring tide in the radial sandbank area in the southern Yell...Based upon the long-term observation of field data, a two-dimensional numerical model is applied to simulating the tidal flow covering from the neap tide to spring tide in the radial sandbank area in the southern Yellow Sea. From the development of tidal current ridges under the hydrodynamic action, multi-purpose analysis and study are carried out, which include the propagation process of tidal wave, the distributions of tidal wave energy rate and tidal range, the tidal ellipses and traces. It is shown that the tidal current is the major dynamic factor for the formation and development of the radial sandbanks, and the differences of tidal wave energy rate and current strength determine the distinct plane shapes of ridges and troughs in this region.展开更多
In order to study the tidal current ridges, a three-dimensional numerical model is, for the first time, applied to studying the hydrodynamic circumstance with Houbolt’ s spiral assumption in the radial sandbank area....In order to study the tidal current ridges, a three-dimensional numerical model is, for the first time, applied to studying the hydrodynamic circumstance with Houbolt’ s spiral assumption in the radial sandbank area. It successfully reveals that the radial sandbanks are molded by to-and-fro tidal current as well as the subtransverse circulation current, and that both contribute to maintaining the interior dynamic balance of the sandbanks. It is also found that the subtransverse circulation current would not always appear in pair within the ridges. These discoveries enrich the theoretical results in hydrodynamics of tidal current ridges.展开更多
A coupled 2-D numerical model for hydrody-namic-sediment transport wasestablished and applied to simulate the tides, tidal currents and sediment movement in the submarineRadial Sandbank area of the southern Yellow Sea...A coupled 2-D numerical model for hydrody-namic-sediment transport wasestablished and applied to simulate the tides, tidal currents and sediment movement in the submarineRadial Sandbank area of the southern Yellow Sea. With a high-resolution topography dataset used inthe model, the simulation reproduced a fine-structured current field and e-rosion-siltationdistribution. The modeled results show that, in the area of Radial Sandbanks, reversing tidalcurrent and seabed erosion occurs within troughs while tidal current with more rotary feature anddeposition occurs above sandbanks, which indicates the tidal-induced formation of the RadialSandbanks. During a tidal period, associating with the variation of current speed, erosionalternates with siltation. The seabed deformation depends on the relative strength of erosion andsiltation in a tidal period.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos .40701117 andJ0630535)
文摘Surthce elevation is tile basic data for geo-science. It is difficult to retrieve tidal-flats＇ elevation from a single Re- mote Sensing （RS） image because of the complicated sediment dynanical environment and huge spatial difference in tidal-flats＇ moisture content. A Digital Elevation Model （DEM） construction method for inconstant inter-tidal zone based on high tempo-resolution MODIS data set in a short period is proposed in a ease study on the Dongsha Sandbank of the Jiangsu Radial Tidal Sand-ridges. In the present study, a batch-preprocessing method based on image partition to handle massive MODIS IB images is developed and applied to 8163 scenes of MODIS images. The dataset of short-period and muhi-temporal MODIS images for inter-tidal flats＇ DEM inversion is selected and the usability of MODIS dataset is analyzed. Shorelines of the Dongsha Sandbank are extracted by use of batch supervised classification. In accord with tidal- 0 level forecasted by the Chenjiawu Tidal Gauge Station at the overpass moment of each RS image, DEMs of inter-tidal flats in January and sutmner（Jul, Aug and Sept）, 2003 are built under ArcG1S9.2. Studies show that： （1） The dataset of short-duration and muhi-phase MODIS images can be used to retrieve the historical DEM of tidal-flats at changeful tidal flats. （2） Aualysis on usability of MODIS images from Aqua and Terra indicates that there are more usable and higbquality MODIS images in spring, autumn and winter, but less in summer. Therefore, the period for building inter-tidal fiats＇ DEM is suggested to be one month in spring, autumn and winter and three months in summer.
基金Supported by the Funds for Creative Research Groups of China (No. 40721004)the National Natural Science Foundation of China (No. 40976056)National Major Science and Technology Project of Water Pollution Control and Countermeasures (No. 2008ZX07421-001)
文摘This study focuses on dynamic mechanism behind the formation of the freshwater zone around the Meimao Sandbank by use of 3D numerical simulation.The Meimao Sandbank is located along the southern bank of the South Passage in the Changjiang(Yangtze River) estuary,which is considered as a freshwater resource for Shanghai City.Interaction between runoff and tide is the main mechanism of the freshwater zone formation.However,the freshwater zone often suffers from saltwater intrusion in dry season.Tidal oscillation is stronger during spring tides,able to carry freshwater farther seaward.Therefore,it is more likely to occur during the ebb of a spring tide in dry seasons.In addition,the water zone is sensitive to runoff:when runoff decreases,it disappears,and vice versa.The northerly winds favor the formation of the freshwater zone.
基金Project supported by the National Natural Science Foundation of China (Grant No. 49236120).
文摘Based upon the long-term observation of field data, a two-dimensional numerical model is applied to simulating the tidal flow covering from the neap tide to spring tide in the radial sandbank area in the southern Yellow Sea. From the development of tidal current ridges under the hydrodynamic action, multi-purpose analysis and study are carried out, which include the propagation process of tidal wave, the distributions of tidal wave energy rate and tidal range, the tidal ellipses and traces. It is shown that the tidal current is the major dynamic factor for the formation and development of the radial sandbanks, and the differences of tidal wave energy rate and current strength determine the distinct plane shapes of ridges and troughs in this region.
基金Project supported by the National Natural Science Foundation of China (Grant No. 49236120).
文摘In order to study the tidal current ridges, a three-dimensional numerical model is, for the first time, applied to studying the hydrodynamic circumstance with Houbolt’ s spiral assumption in the radial sandbank area. It successfully reveals that the radial sandbanks are molded by to-and-fro tidal current as well as the subtransverse circulation current, and that both contribute to maintaining the interior dynamic balance of the sandbanks. It is also found that the subtransverse circulation current would not always appear in pair within the ridges. These discoveries enrich the theoretical results in hydrodynamics of tidal current ridges.
文摘A coupled 2-D numerical model for hydrody-namic-sediment transport wasestablished and applied to simulate the tides, tidal currents and sediment movement in the submarineRadial Sandbank area of the southern Yellow Sea. With a high-resolution topography dataset used inthe model, the simulation reproduced a fine-structured current field and e-rosion-siltationdistribution. The modeled results show that, in the area of Radial Sandbanks, reversing tidalcurrent and seabed erosion occurs within troughs while tidal current with more rotary feature anddeposition occurs above sandbanks, which indicates the tidal-induced formation of the RadialSandbanks. During a tidal period, associating with the variation of current speed, erosionalternates with siltation. The seabed deformation depends on the relative strength of erosion andsiltation in a tidal period.
