2017 Vol. 39, No. 9
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2017, 39(9): .
Abstract:
2017, 39(9): 1-14.
doi: 10.3969/j.issn.0253-4193.2017.09.001
Abstract:
The South Indian Ocean is a region abundant of mesoscale eddies. We analyzed statistical characteristics of mesoscale eddies in the South Indian Ocean(10°-35°S, 50°-120°E) based on merged satellite altimetry data as well as Argo profile data. The results show that eddy frequency is distinctly high in the band area between 18°-30°S; eddy radius tend to increase from the south the north; the radius, eddy kinetic energy, energy intensity and vorticity of long-lived eddies firstly increased and then decreased as eddies evaluate during their lifespans. Most eddies propagate westward while their meridional movement is not significant and long-lived cyclonic eddies (CEs) and anticyclonic eddies (AEs) have poleward (equatorward) deflections, respectively. The mean propagation speed of eddies is 5.9 cm/s and the magnitude present a feature of zonal distribution. Under the mixing layer, CE (AE) represent consistent negative (positive) temperature anomaly and there exist two cold (warn) cores with negative (positive) temperature anomaly, respectively. The salinity structure of CE presented as ‘positive-negative’ salinity anomaly structure, while it is opposite for AE. Eddies' influence on temperature and salinity could reach more than 1 000×104 Pa.
The South Indian Ocean is a region abundant of mesoscale eddies. We analyzed statistical characteristics of mesoscale eddies in the South Indian Ocean(10°-35°S, 50°-120°E) based on merged satellite altimetry data as well as Argo profile data. The results show that eddy frequency is distinctly high in the band area between 18°-30°S; eddy radius tend to increase from the south the north; the radius, eddy kinetic energy, energy intensity and vorticity of long-lived eddies firstly increased and then decreased as eddies evaluate during their lifespans. Most eddies propagate westward while their meridional movement is not significant and long-lived cyclonic eddies (CEs) and anticyclonic eddies (AEs) have poleward (equatorward) deflections, respectively. The mean propagation speed of eddies is 5.9 cm/s and the magnitude present a feature of zonal distribution. Under the mixing layer, CE (AE) represent consistent negative (positive) temperature anomaly and there exist two cold (warn) cores with negative (positive) temperature anomaly, respectively. The salinity structure of CE presented as ‘positive-negative’ salinity anomaly structure, while it is opposite for AE. Eddies' influence on temperature and salinity could reach more than 1 000×104 Pa.
2017, 39(9): 15-25.
doi: 10.3969/j.issn.0253-4193.2017.09.002
Abstract:
The mean state and low frequency variability of Kuroshio in the east of Taiwan is investigated by quantitatively analyzing the 23-year (1993-2015) surface Absolute Dynamic Topography (ADT) data. The mean state of Kuroshio is given, with a flowing width of around 136 km and surface transport of about 7.75×104 m2/s, the standard deviation of the width and surface transport are 28 km and 2.14×104 m2/s, respectively. The results indicate that the Kuroshio east of Taiwan shows both seasonal and interannual variability significantly. Results of power spectrum analysis indicate that the primary periods of the Kuroshio surface transport in east of Taiwan are 1 and 2.8 years respectively. Spatially, the Kuroshio surface transport in southeast of Taiwan has a relatively larger variability than that in the northeast of Taiwan. Correlation and composite analysis shows that PTO(Philippines-Taiwan Oscillation)has a significant correlation with the interannual variability of Kuroshio. The PDO-induced relative intensity of the anticyclonic and cyclonic eddy is the dominant factor controlling the interannual variability of Kuroshio in east of Taiwan.
The mean state and low frequency variability of Kuroshio in the east of Taiwan is investigated by quantitatively analyzing the 23-year (1993-2015) surface Absolute Dynamic Topography (ADT) data. The mean state of Kuroshio is given, with a flowing width of around 136 km and surface transport of about 7.75×104 m2/s, the standard deviation of the width and surface transport are 28 km and 2.14×104 m2/s, respectively. The results indicate that the Kuroshio east of Taiwan shows both seasonal and interannual variability significantly. Results of power spectrum analysis indicate that the primary periods of the Kuroshio surface transport in east of Taiwan are 1 and 2.8 years respectively. Spatially, the Kuroshio surface transport in southeast of Taiwan has a relatively larger variability than that in the northeast of Taiwan. Correlation and composite analysis shows that PTO(Philippines-Taiwan Oscillation)has a significant correlation with the interannual variability of Kuroshio. The PDO-induced relative intensity of the anticyclonic and cyclonic eddy is the dominant factor controlling the interannual variability of Kuroshio in east of Taiwan.
2017, 39(9): 26-39.
doi: 10.3969/j.issn.0253-4193.2017.09.003
Abstract:
Based on the observed data of current and suspended sediment concentration (SSC) during the flood season (13-14 and 16-17, August, 2007), by the means of measured data analysis and the TELEMAC-2D numerical model, this article reveals the spatial distribution characteristics of SSC in the Lingdingyang Esturay:in the longitudinal direction along west channel, SSC decrease first, then increase, and then decrease again from bay head to open sea; laterally, west channel, east channel and the north of the middle flat are higher SSC areas; the maximal center of SSC is located on the northwest of Neilingding Island. The model of longitudinal material transport reveals that the main reasons of net suspended sediment transport are advection, tidal asymmetry and vertical circulation. The effects of tidal current, runoff with sediment transport, solid boundary and topography condition are the main reasons for the 2D distribution characteristics of SSC in the Lingdingyang Estuary.
Based on the observed data of current and suspended sediment concentration (SSC) during the flood season (13-14 and 16-17, August, 2007), by the means of measured data analysis and the TELEMAC-2D numerical model, this article reveals the spatial distribution characteristics of SSC in the Lingdingyang Esturay:in the longitudinal direction along west channel, SSC decrease first, then increase, and then decrease again from bay head to open sea; laterally, west channel, east channel and the north of the middle flat are higher SSC areas; the maximal center of SSC is located on the northwest of Neilingding Island. The model of longitudinal material transport reveals that the main reasons of net suspended sediment transport are advection, tidal asymmetry and vertical circulation. The effects of tidal current, runoff with sediment transport, solid boundary and topography condition are the main reasons for the 2D distribution characteristics of SSC in the Lingdingyang Estuary.
2017, 39(9): 40-50.
doi: 10.3969/j.issn.0253-4193.2017.09.004
Abstract:
Synthetic Aperture Radar (SAR) plays an important role in typhoon wind field retrieval, but due to the influence of the rainfall on the radar signal, the inversion precision of sea surface wind field will decline. In this paper, we analysis the rain effect to the 2014 typhoon Rammasun by using RADARSAT-2 SAR data, quasi-synchronous rainfall data and reanalysis data. The damping from rainfall to the water surface is simulated by rain rate and incident angle. Rain-induced attenuation and raindrop volumetric scattering was also evaluated. It is found that the rain effect to the sea surface perturbation is much complex than the other two factors, and the signal attenuation increases with the increases of rainfall and incident angle, raindrop volumetric scattering and rain-induced sea surface damping increase with the increase of rainfall, but with the decrease of incident angle. The experimental results also indicate that the model can improve the SAR wind measurement accuracy under rainfall conditions.
Synthetic Aperture Radar (SAR) plays an important role in typhoon wind field retrieval, but due to the influence of the rainfall on the radar signal, the inversion precision of sea surface wind field will decline. In this paper, we analysis the rain effect to the 2014 typhoon Rammasun by using RADARSAT-2 SAR data, quasi-synchronous rainfall data and reanalysis data. The damping from rainfall to the water surface is simulated by rain rate and incident angle. Rain-induced attenuation and raindrop volumetric scattering was also evaluated. It is found that the rain effect to the sea surface perturbation is much complex than the other two factors, and the signal attenuation increases with the increases of rainfall and incident angle, raindrop volumetric scattering and rain-induced sea surface damping increase with the increase of rainfall, but with the decrease of incident angle. The experimental results also indicate that the model can improve the SAR wind measurement accuracy under rainfall conditions.
2017, 39(9): 51-57.
doi: 10.3969/j.issn.0253-4193.2017.09.005
Abstract:
By combining Particle Swarm Optimization (PSO) with BP neural network, the initial weights and thresholds of BP neural network classification are optimized by utilizing PSO with strong robustness and global searching ability. Extracting six main feature vectors of sandy, rocks and mud in the seabed sonar images based on the data of side scan sonar in the Zhujiang Estuary Delta, using the PSO-BP method to classify seabed sediment. The experiment shows that the accuracy of the sediments classification is more than 90%, higher than the accuracy about 70% which using BP neural network only. It proves that the PSO-BP method can be effectively applied to the identification and classification of sediment seabed.
By combining Particle Swarm Optimization (PSO) with BP neural network, the initial weights and thresholds of BP neural network classification are optimized by utilizing PSO with strong robustness and global searching ability. Extracting six main feature vectors of sandy, rocks and mud in the seabed sonar images based on the data of side scan sonar in the Zhujiang Estuary Delta, using the PSO-BP method to classify seabed sediment. The experiment shows that the accuracy of the sediments classification is more than 90%, higher than the accuracy about 70% which using BP neural network only. It proves that the PSO-BP method can be effectively applied to the identification and classification of sediment seabed.
2017, 39(9): 58-70.
doi: 10.3969/j.issn.0253-4193.2017.09.006
Abstract:
Concentrations of dissolved amino acid (THAA), dissolved organic carbon (DOC) and chlorophyll a(Chl a) were determined in five transects of the northern South China Sea (NSCS) in June 2015. The results showed that the concentrations of THAA ranged from 0.40 to 1.95 μmol/L, with an average of (0.80±0.40) μmol/L. THAA concentrations exhibited a decreasing trend from the nearshore to offshore stations, indicating that terrestrial input plays an important role in affecting the distributions of THAA. The vertical distribution of THAA concentrations displayed a decreasing trend from the surface layer to the bottom layer. The present study found that the concentrations of THAA were negatively correlated to the D-amino acids (D-Glu and D-Ala), but positively correlated to Asp/β-Ala and Glu/γ-Aba ratios. Our results indicated that the bacterial consumption was an important factor influencing the concentration of THAA in the NSCS. The contribution of bacterial organic carbon to DOC was (29.32 ±14.32)% in the NSCS, exhibiting increasing trends from the nearshore to offshore sites and from the surface waters to the bottom waters. High values of carbon normalized yields of amino acids (THAA-C%), reactivity index and degradation index (DI) were found in the area near the Zhujiang Estuary. With the increasing of the water depth, the values of the degradation factors were significantly decreased, reflecting the higher degradation extent of organic matter in the bottom waters.
Concentrations of dissolved amino acid (THAA), dissolved organic carbon (DOC) and chlorophyll a(Chl a) were determined in five transects of the northern South China Sea (NSCS) in June 2015. The results showed that the concentrations of THAA ranged from 0.40 to 1.95 μmol/L, with an average of (0.80±0.40) μmol/L. THAA concentrations exhibited a decreasing trend from the nearshore to offshore stations, indicating that terrestrial input plays an important role in affecting the distributions of THAA. The vertical distribution of THAA concentrations displayed a decreasing trend from the surface layer to the bottom layer. The present study found that the concentrations of THAA were negatively correlated to the D-amino acids (D-Glu and D-Ala), but positively correlated to Asp/β-Ala and Glu/γ-Aba ratios. Our results indicated that the bacterial consumption was an important factor influencing the concentration of THAA in the NSCS. The contribution of bacterial organic carbon to DOC was (29.32 ±14.32)% in the NSCS, exhibiting increasing trends from the nearshore to offshore sites and from the surface waters to the bottom waters. High values of carbon normalized yields of amino acids (THAA-C%), reactivity index and degradation index (DI) were found in the area near the Zhujiang Estuary. With the increasing of the water depth, the values of the degradation factors were significantly decreased, reflecting the higher degradation extent of organic matter in the bottom waters.
2017, 39(9): 71-82.
doi: 10.3969/j.issn.0253-4193.2017.09.007
Abstract:
As an effective tracer of sediment provenance, continental weathering and oceanic currents evolution, clay mineral has been widely used in palaeoenvironmental research of the South China Sea in the recent years. The general character of spatial distribution of clay minerals in the surface sediments of the South China Sea basin has been established. However, there remains no detailed knowledge about the distribution and sources of clay minerals in the northwestern South China Sea, which is possibly influenced by terrigenous materials input from both of the Zhujiang River and Hainan Island. Here we analyze assemblages and crystallinity of the clay minerals in the surface sediments of this area, and further investigate the sediment provenance of clay minerals. The clay mineral assemblage in sediments of the northwestern South China Sea mainly consists of illite (average~45%), with associated smectite (~27%) and kaolinite (~21%). Chlorite (~6%) is present in lesser amounts. On the spatial scale of this area, smectite is characterized by higher contents in the southwest South China Sea and lower in the northeast of the study area. On the contrary, illite contents are higher in the northeast and lower in the southwest. The percentage of kaolinite shows a decreasing trend from the coast to the shelf, while the contents of chlorite shows an increasing trend. Generally, clay mineral assemblage in the surface sediments of the study area is distinct from the modern Zhujiang River sediments, but it is more similar to the old Zhujiang River mouth sediments deposited about 2.5 ka ago. Moreover, the seismic and sediment core studies revealed a very low sedimentation rate (4 cm/ka) and thin muddy sediments (<0.6 m) on the surface of the continental shelf of the northwestern South China Sea since the Holocene. Therefore, we suggest that the surface sediment in this area is possibly resulted from reworked old materials which were mainly transported from the old Zhujiang River in the late Holocene. In addition to the old Zhujiang River, the small rivers in the northern Hainan Island could also have contributed smectite to its surrounding area. Further analysis using kaolinite/illite ratio and illite chemical index confirms that the Zhujiang River is the main provenance of illite, kaolinite and chlorite in the study area. Besides, Taiwan and Hainan Island may also provide a minor contribution of illite/chlorite-rich and kaolinite-rich sediments, respectively. This result will be helpful for the future studies especially about the sediment processes from source to sink and palaeoenvironmental evolution in the northwestern South China Sea.
As an effective tracer of sediment provenance, continental weathering and oceanic currents evolution, clay mineral has been widely used in palaeoenvironmental research of the South China Sea in the recent years. The general character of spatial distribution of clay minerals in the surface sediments of the South China Sea basin has been established. However, there remains no detailed knowledge about the distribution and sources of clay minerals in the northwestern South China Sea, which is possibly influenced by terrigenous materials input from both of the Zhujiang River and Hainan Island. Here we analyze assemblages and crystallinity of the clay minerals in the surface sediments of this area, and further investigate the sediment provenance of clay minerals. The clay mineral assemblage in sediments of the northwestern South China Sea mainly consists of illite (average~45%), with associated smectite (~27%) and kaolinite (~21%). Chlorite (~6%) is present in lesser amounts. On the spatial scale of this area, smectite is characterized by higher contents in the southwest South China Sea and lower in the northeast of the study area. On the contrary, illite contents are higher in the northeast and lower in the southwest. The percentage of kaolinite shows a decreasing trend from the coast to the shelf, while the contents of chlorite shows an increasing trend. Generally, clay mineral assemblage in the surface sediments of the study area is distinct from the modern Zhujiang River sediments, but it is more similar to the old Zhujiang River mouth sediments deposited about 2.5 ka ago. Moreover, the seismic and sediment core studies revealed a very low sedimentation rate (4 cm/ka) and thin muddy sediments (<0.6 m) on the surface of the continental shelf of the northwestern South China Sea since the Holocene. Therefore, we suggest that the surface sediment in this area is possibly resulted from reworked old materials which were mainly transported from the old Zhujiang River in the late Holocene. In addition to the old Zhujiang River, the small rivers in the northern Hainan Island could also have contributed smectite to its surrounding area. Further analysis using kaolinite/illite ratio and illite chemical index confirms that the Zhujiang River is the main provenance of illite, kaolinite and chlorite in the study area. Besides, Taiwan and Hainan Island may also provide a minor contribution of illite/chlorite-rich and kaolinite-rich sediments, respectively. This result will be helpful for the future studies especially about the sediment processes from source to sink and palaeoenvironmental evolution in the northwestern South China Sea.
2017, 39(9): 83-89.
doi: 10.3969/j.issn.0253-4193.2017.09.008
Abstract:
Methane emission from seabed is a wide phenomenon around the world. Gas bubble plumes were observed in the Multi-Beam(MB) water column echo image with the newly (2016) acquired data in the north slope of South China Sea. Gas bubbles manifest themselves as flares on the MB image, and have the diameter of about 30 to 50 m. Plumes emanating from the~1 380 m depth seabed to the~650 m depth, resulting heights of >700 m. On the sub-bottom profile passing through the plume, we found the acoustic blanking zone which may indicate the gas migration pathway, but no clear anomalies were observed in the water column. This may be explained by the low resolution of the sub-bottom profiler image or the intermittence of the gas seepage. Lacking of multi-channel seismic and geochemistry data, we cannot further infer the formation mechanism of the gas plumes. The discovery of gas bubble plumes in the north slope of south china may improve our understanding of the methane seepage on the passive continental marginal, and the formation and dissociation of gas hydrates.
Methane emission from seabed is a wide phenomenon around the world. Gas bubble plumes were observed in the Multi-Beam(MB) water column echo image with the newly (2016) acquired data in the north slope of South China Sea. Gas bubbles manifest themselves as flares on the MB image, and have the diameter of about 30 to 50 m. Plumes emanating from the~1 380 m depth seabed to the~650 m depth, resulting heights of >700 m. On the sub-bottom profile passing through the plume, we found the acoustic blanking zone which may indicate the gas migration pathway, but no clear anomalies were observed in the water column. This may be explained by the low resolution of the sub-bottom profiler image or the intermittence of the gas seepage. Lacking of multi-channel seismic and geochemistry data, we cannot further infer the formation mechanism of the gas plumes. The discovery of gas bubble plumes in the north slope of south china may improve our understanding of the methane seepage on the passive continental marginal, and the formation and dissociation of gas hydrates.
2017, 39(9): 90-100.
doi: 10.3969/j.issn.0253-4193.2017.09.009
Abstract:
Based on the results of field surveys, the spatial and temporal dynamics of sandy coastal geomorphology along the eastern Laizhou Bay over the last 60 years was investigated using the comprehensive methods of digital shoreline analysis, remote sensing and geographic information system technologies. The data mainly derived from the nautical charts, topographic maps and high resolution remote sensing images which measured and imaged in different periods. The results show that there are significant spatial-temporal variations in both the sandy coast shoreline migration and the subaqueous slope erosion-deposition evolution along the eastern Laizhou Bay. The alternate regulation of forward and backward for shoreline migration is caught in this study. There is a remarkable non-linear characteristic in the time process. The proportion of the erosional shoreline is fluctuated and phased from 1959 to 2013. The average annual evolution rate of eroded coast is divided into two stages by 1985. The erosion rate decreased from the maximum value of 4.95 m/a (during the period of 1959-1969) to minimum value 1.97 m/a (1969-1985) at prophase. In the late period, the erosion rate increased from 1.97 m/a to 4.43 m/a (1985-1998), and the coast was in serious erosion state since then. The characteristics of shoreline migration in four headland bays are not consistent with overall trend. At the same time, the scouring strips distribute alternating with the silting of the subaqueous slope. The trend of scouring and silting evolution was basically opposite in the same coast between the periods of 1959-1985 and 1985-2008. Further analysis indicate that there are 5 alternations of erosion and deposition and the changes of rate of erosion and siltation, under the control of geomorphic effects of anthropogenic activities such as sediment trapping by reservoirs, fishing culture in supratidal zone and coastal engineering, in the east of Laizhou Bay during recent 60 years.
Based on the results of field surveys, the spatial and temporal dynamics of sandy coastal geomorphology along the eastern Laizhou Bay over the last 60 years was investigated using the comprehensive methods of digital shoreline analysis, remote sensing and geographic information system technologies. The data mainly derived from the nautical charts, topographic maps and high resolution remote sensing images which measured and imaged in different periods. The results show that there are significant spatial-temporal variations in both the sandy coast shoreline migration and the subaqueous slope erosion-deposition evolution along the eastern Laizhou Bay. The alternate regulation of forward and backward for shoreline migration is caught in this study. There is a remarkable non-linear characteristic in the time process. The proportion of the erosional shoreline is fluctuated and phased from 1959 to 2013. The average annual evolution rate of eroded coast is divided into two stages by 1985. The erosion rate decreased from the maximum value of 4.95 m/a (during the period of 1959-1969) to minimum value 1.97 m/a (1969-1985) at prophase. In the late period, the erosion rate increased from 1.97 m/a to 4.43 m/a (1985-1998), and the coast was in serious erosion state since then. The characteristics of shoreline migration in four headland bays are not consistent with overall trend. At the same time, the scouring strips distribute alternating with the silting of the subaqueous slope. The trend of scouring and silting evolution was basically opposite in the same coast between the periods of 1959-1985 and 1985-2008. Further analysis indicate that there are 5 alternations of erosion and deposition and the changes of rate of erosion and siltation, under the control of geomorphic effects of anthropogenic activities such as sediment trapping by reservoirs, fishing culture in supratidal zone and coastal engineering, in the east of Laizhou Bay during recent 60 years.
2017, 39(9): 101-109.
doi: 10.3969/j.issn.0253-4193.2017.09.010
Abstract:
Quaternary newly deposited loose seabed soil widely distributes in offshore area in the world. Wave-induced residual liquefaction in loose seabed floor brings great risk to the stability of offshore structures in extreme climate. In this study, wave & current-induced residual liquefaction in loose seabed floor has been investigated comprehensively adopting FSSI-CAS 2D incorporating Pastor-Zienkiewicz-Mark Ⅲ(PZⅢ) soil model which is a validated integrated numerical model. The time history of wave & current-induced pore pressure, effective stress, stress angle are discussed. The variation process of progressive liquefactionis illustrated in detail. The computational results confirm that the wave & current-induced liquefaction in loose seabed soil is progressively downward, initiating at seabed surface. Besides, it is found that vertical distribution of oscillatory pore pressure, and time history of stress angle could be taken as indirect indicator to judge the occurrence of wave-induced residual liquefaction. The developing process of the progressive liquefaction is analyzed by stress statement data of seabed soil.
Quaternary newly deposited loose seabed soil widely distributes in offshore area in the world. Wave-induced residual liquefaction in loose seabed floor brings great risk to the stability of offshore structures in extreme climate. In this study, wave & current-induced residual liquefaction in loose seabed floor has been investigated comprehensively adopting FSSI-CAS 2D incorporating Pastor-Zienkiewicz-Mark Ⅲ(PZⅢ) soil model which is a validated integrated numerical model. The time history of wave & current-induced pore pressure, effective stress, stress angle are discussed. The variation process of progressive liquefactionis illustrated in detail. The computational results confirm that the wave & current-induced liquefaction in loose seabed soil is progressively downward, initiating at seabed surface. Besides, it is found that vertical distribution of oscillatory pore pressure, and time history of stress angle could be taken as indirect indicator to judge the occurrence of wave-induced residual liquefaction. The developing process of the progressive liquefaction is analyzed by stress statement data of seabed soil.
2017, 39(9): 110-120.
doi: 10.3969/j.issn.0253-4193.2017.09.011
Abstract:
In order to retrieve Arctic sea ice drift maps, the maximum cross correlation (MCC) method is applied to the 37 GHz vertically polarized brightness temperature data taken from the scanning microwave radiometer onboard the HY-2 Satellite of China. A validation of our sea-ice drift products during winters 2012 and 2013 with the IABP buoys shows a good accuracy, with the root mean square errors in ice drift speed and ice drift direction being 1.12 cm/s and 16.37°, respectively, thus demonstrating the practicability of the brightness temperature data from HY-2 Satellite scanning microwave radiometer in retrieving sea ice motion. Using the 91 GHz vertically polarized brightness temperature data from Special Sensor Microwave Imager/Sounder radiometers onboard the Defense Meteorological Satellite Program, and employing a Laplacian of the Gaussian filter, the sea ice drift production obtained by MCC method are found to be better in quality than those obtained by French Research Institute for Exploitation of the Sea.
In order to retrieve Arctic sea ice drift maps, the maximum cross correlation (MCC) method is applied to the 37 GHz vertically polarized brightness temperature data taken from the scanning microwave radiometer onboard the HY-2 Satellite of China. A validation of our sea-ice drift products during winters 2012 and 2013 with the IABP buoys shows a good accuracy, with the root mean square errors in ice drift speed and ice drift direction being 1.12 cm/s and 16.37°, respectively, thus demonstrating the practicability of the brightness temperature data from HY-2 Satellite scanning microwave radiometer in retrieving sea ice motion. Using the 91 GHz vertically polarized brightness temperature data from Special Sensor Microwave Imager/Sounder radiometers onboard the Defense Meteorological Satellite Program, and employing a Laplacian of the Gaussian filter, the sea ice drift production obtained by MCC method are found to be better in quality than those obtained by French Research Institute for Exploitation of the Sea.
2017, 39(9): 121-132.
doi: 10.3969/j.issn.0253-4193.2017.09.012
Abstract:
Green tide area information extraction is an important link of the remote sensing monitoring, its result will directly affect the subsequent statistical analysis and the early warning prediction. Now researchers generally extract the green tide area information based on the traditional threshold method, and this approach has many disadvantages such as low efficiency, unstable result and human factors. Against to above-mentioned problem, the dual method and split Bregman projection method based on variational level set method was studied used to the green tide area information extraction in this paper. A new quantization method was proposed, which was used to deal with the green tide information result extracted by the two mentioned methods. Based on the traditional threshold method and the dual method and split Bregman projection method, the experiments of three images were respectively carried out, and extraction results were compared and analyzed. To higher resolution satellite remote sensing data, the experiment results show that not only the extraction efficiency but the accuracy and stability based on variational level set method are all superior to the traditional threshold method.
Green tide area information extraction is an important link of the remote sensing monitoring, its result will directly affect the subsequent statistical analysis and the early warning prediction. Now researchers generally extract the green tide area information based on the traditional threshold method, and this approach has many disadvantages such as low efficiency, unstable result and human factors. Against to above-mentioned problem, the dual method and split Bregman projection method based on variational level set method was studied used to the green tide area information extraction in this paper. A new quantization method was proposed, which was used to deal with the green tide information result extracted by the two mentioned methods. Based on the traditional threshold method and the dual method and split Bregman projection method, the experiments of three images were respectively carried out, and extraction results were compared and analyzed. To higher resolution satellite remote sensing data, the experiment results show that not only the extraction efficiency but the accuracy and stability based on variational level set method are all superior to the traditional threshold method.
2017, 39(9): 133-145.
doi: 10.3969/j.issn.0253-4193.2017.09.013
Abstract:
GOCI satellite data is adopted to retrieve high concentrations of colored dissolved organic matter in coastal waters of Changjiang Estuary. The inversion model is based on QAA-CDOM algorithm and field measured data. The BP neural network was used to fit the relationship between bbp(555) and ap(443), which is used in QAA-CDOM and needs to be optimized for the water in the Changjiang Estuary. The results show that the inversion accuracy is excellent with mean relative error 0.35. Then based on advantage of GOCI's serial imaging, 8 images acquired in March 15, 2014 were inverted and analysed for CDOM daily variations in Changjiang Estuary and its adjacent seawater. The obtained the CDOM variation pattern is that CDOM in Changjiang Estuary and its adjacent seawater is mainly impacted by tides and the discharge of Changjiang. Inside the Changjiang Estuary, due to the effect of Changjiang diluted water, CDOM concentration in high tide is higher than that in the low tide, and it showed gradually decreasing trend from the estuary to the open sea.
GOCI satellite data is adopted to retrieve high concentrations of colored dissolved organic matter in coastal waters of Changjiang Estuary. The inversion model is based on QAA-CDOM algorithm and field measured data. The BP neural network was used to fit the relationship between bbp(555) and ap(443), which is used in QAA-CDOM and needs to be optimized for the water in the Changjiang Estuary. The results show that the inversion accuracy is excellent with mean relative error 0.35. Then based on advantage of GOCI's serial imaging, 8 images acquired in March 15, 2014 were inverted and analysed for CDOM daily variations in Changjiang Estuary and its adjacent seawater. The obtained the CDOM variation pattern is that CDOM in Changjiang Estuary and its adjacent seawater is mainly impacted by tides and the discharge of Changjiang. Inside the Changjiang Estuary, due to the effect of Changjiang diluted water, CDOM concentration in high tide is higher than that in the low tide, and it showed gradually decreasing trend from the estuary to the open sea.
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