2017 Vol. 39, No. 1
Display Method:
2017, 39(1): .
Abstract:
2017, 39(1): .
Abstract:
2017, 39(1): 1-10.
doi: 10.3969/j.issn.0253-4193.2017.01.001
Abstract:
A hyperbolic mild-slope equation wave propagation model was united with a depth-averaged 2D tidal flow model and the wave effect on flow is generated by radiation stresses of waves added to the tidal flow model. The wave induced current in the Modaomen estuary in the dry season was investigated for the first time by the model with the topography measured in 2011. The numerical results show that during the ebb tide the seaward currents are reduced by the opposing wave and two stagnant zones arise inside the shoaling water of the mouth bar, the seaward currents in east and west shoals also decrease, but the seaward currents inside the east and west deep grooves increase. During the flood tide the landward currents are increased by the following wave and a washover zone arise inside the mouth bar, the landward currents in east and west shoals also increase, but the landward currents inside the east and west deep grooves reduce at the same time.
A hyperbolic mild-slope equation wave propagation model was united with a depth-averaged 2D tidal flow model and the wave effect on flow is generated by radiation stresses of waves added to the tidal flow model. The wave induced current in the Modaomen estuary in the dry season was investigated for the first time by the model with the topography measured in 2011. The numerical results show that during the ebb tide the seaward currents are reduced by the opposing wave and two stagnant zones arise inside the shoaling water of the mouth bar, the seaward currents in east and west shoals also decrease, but the seaward currents inside the east and west deep grooves increase. During the flood tide the landward currents are increased by the following wave and a washover zone arise inside the mouth bar, the landward currents in east and west shoals also increase, but the landward currents inside the east and west deep grooves reduce at the same time.
2017, 39(1): 11-27.
doi: 10.3969/j.issn.0253-4193.2017.01.002
Abstract:
Different decaying characteristics for two types of El Niño and their relationships with the summer rainfall in China were investigated by using 743 stations daily precipitation data from China Meteorological Administration, NCEP circulation reanalysis datasets and the monthly mean Met Office Hadley Center sea surface temperature (SST) analyses data. Based on the evolution of the SST anomalies (SSTA) across the equator(5°S-5°N), two types of decaying patterns are identified for EP-El Niño:(1) An evolution pattern that SSTA decaying from east to west (E-W). The positive SSTA larger than 0.5℃ first disappear in offshore of South America and the disappearance extends to the west. (2) An evolution pattern that SSTA decaying from west to east (W-E). The positive SSTA larger than 0.5℃ first disappear in the central Pacific and the disappearance extends to the east. The decaying evolution of CP-El Niño is classified into three patterns:(1) A symmetric (S)-decaying pattern whose SSTA grows and decays symmetrically with respect to a peak phase, (2) A prolonged(P)-decaying pattern that is followed by a EP-El Niño type, (3) An abrupt(A)-decaying pattern that is followed by a EP-La Niña type. In the following summer of EP-El Niño in two different decaying patterns, there are almost completely opposite rainfall anomalies in North China, South China,the region between and the upstream area of the Yangtze River and the Yellow River Valley (they are called the Two River for short). In the following summer for E-W pattern, suppressed rainfall appears in the region between and the upstream area of the Two River, while the rainfall in North China is abundant and rainfall of the area to the south of the Yangtze River is slightly more. However, there are significantly positive anomalies in the region between and the upstream area of the Two River with the center of positive anomalies located along the Yangtze River, but the negative rainfall anomalies in most region of South China and North China for W-E pattern. As for three decaying patterns of CP-El Niño, the positive anomalies are present in the region between the Huaihe River and the Yellow River Valley for S pattern, in the Yangtze River Valley for P pattern, while in the lower reaches of the Yellow River for A pattern. Rainfall in the Northeast China, especially in the northern of Northeast China, is below normal for S and A pattern, while above normal for P pattern. In the Southwest China, wet (dry) signal appears for S (A) pattern. And in the northern of Northwest China,there is less (more) precipitation for A pattern (S and P pattern). Different distribution of summer rainfall anomalies in the decaying phase of El Niño is closely associated with their different decaying patterns. When inspecting the impacts of the two types of El Niño on the following summer rainfall, it would be better to consider their different decaying patterns in view of the larger significant area and T-inspection value of rainfall anomalies. All these will provide important reference for the short-term climate prediction of summer rainfall.
Different decaying characteristics for two types of El Niño and their relationships with the summer rainfall in China were investigated by using 743 stations daily precipitation data from China Meteorological Administration, NCEP circulation reanalysis datasets and the monthly mean Met Office Hadley Center sea surface temperature (SST) analyses data. Based on the evolution of the SST anomalies (SSTA) across the equator(5°S-5°N), two types of decaying patterns are identified for EP-El Niño:(1) An evolution pattern that SSTA decaying from east to west (E-W). The positive SSTA larger than 0.5℃ first disappear in offshore of South America and the disappearance extends to the west. (2) An evolution pattern that SSTA decaying from west to east (W-E). The positive SSTA larger than 0.5℃ first disappear in the central Pacific and the disappearance extends to the east. The decaying evolution of CP-El Niño is classified into three patterns:(1) A symmetric (S)-decaying pattern whose SSTA grows and decays symmetrically with respect to a peak phase, (2) A prolonged(P)-decaying pattern that is followed by a EP-El Niño type, (3) An abrupt(A)-decaying pattern that is followed by a EP-La Niña type. In the following summer of EP-El Niño in two different decaying patterns, there are almost completely opposite rainfall anomalies in North China, South China,the region between and the upstream area of the Yangtze River and the Yellow River Valley (they are called the Two River for short). In the following summer for E-W pattern, suppressed rainfall appears in the region between and the upstream area of the Two River, while the rainfall in North China is abundant and rainfall of the area to the south of the Yangtze River is slightly more. However, there are significantly positive anomalies in the region between and the upstream area of the Two River with the center of positive anomalies located along the Yangtze River, but the negative rainfall anomalies in most region of South China and North China for W-E pattern. As for three decaying patterns of CP-El Niño, the positive anomalies are present in the region between the Huaihe River and the Yellow River Valley for S pattern, in the Yangtze River Valley for P pattern, while in the lower reaches of the Yellow River for A pattern. Rainfall in the Northeast China, especially in the northern of Northeast China, is below normal for S and A pattern, while above normal for P pattern. In the Southwest China, wet (dry) signal appears for S (A) pattern. And in the northern of Northwest China,there is less (more) precipitation for A pattern (S and P pattern). Different distribution of summer rainfall anomalies in the decaying phase of El Niño is closely associated with their different decaying patterns. When inspecting the impacts of the two types of El Niño on the following summer rainfall, it would be better to consider their different decaying patterns in view of the larger significant area and T-inspection value of rainfall anomalies. All these will provide important reference for the short-term climate prediction of summer rainfall.
2017, 39(1): 28-35.
doi: 10.3969/j.issn.0253-4193.2017.01.003
Abstract:
Focusing on the inconsistent phenomenon between wind stress direction and wind direction on the air-sea interface, we designed comprehensive observation at the Bohe Station of the South China Sea from February 4 to March 12, 2015. The wind stress was calculated by using the eddy correlation method, the deviation angle between the wind stress and wind vector was analyzed under 3 different atmospheric stability conditions. Furthermore, the parametric relationship between the angle and wind speed was proposed under the stable atmospheric stability condition. Results showed that the stress vector is to the left of the wind for the air stable condition, besides, the deviation angle decreases with the increase of inverse wave age and wind speed, while the stress vector is generally to the right of the wind for the unstable case. The wind stress vector depends on not only the sea surface winds, but also on the surface waves and atmospheric stable conditions.
Focusing on the inconsistent phenomenon between wind stress direction and wind direction on the air-sea interface, we designed comprehensive observation at the Bohe Station of the South China Sea from February 4 to March 12, 2015. The wind stress was calculated by using the eddy correlation method, the deviation angle between the wind stress and wind vector was analyzed under 3 different atmospheric stability conditions. Furthermore, the parametric relationship between the angle and wind speed was proposed under the stable atmospheric stability condition. Results showed that the stress vector is to the left of the wind for the air stable condition, besides, the deviation angle decreases with the increase of inverse wave age and wind speed, while the stress vector is generally to the right of the wind for the unstable case. The wind stress vector depends on not only the sea surface winds, but also on the surface waves and atmospheric stable conditions.
2017, 39(1): 36-45.
doi: 10.3969/j.issn.0253-4193.2017.01.004
Abstract:
The sound field frequency-range interference patterns of sea-surface source in deep water are discussed based on ray theory. Approximate formulae of the sound field frequency-range interference patterns in the shadow zone are provided. In the shadow zone, the interference cycle decreases with the increase of the depth of the receiver and increases with the increase of the propagation range. As a result, the source range can be extracted from the interference cycle of the sound intensity using a single hydrophone. The sound field interference patterns caused by sea-surface broadband noise sources in the shadow zone have been observed in a deep sea experiment in the South China Sea. The availability of the shadow zone sound field interference structure in the passive source range estimation is verified by experimental data. Compared with conventional matched field passive source localization method, this method doesn't need seafloor acoustic parameters and large scale computing of replica fields.
The sound field frequency-range interference patterns of sea-surface source in deep water are discussed based on ray theory. Approximate formulae of the sound field frequency-range interference patterns in the shadow zone are provided. In the shadow zone, the interference cycle decreases with the increase of the depth of the receiver and increases with the increase of the propagation range. As a result, the source range can be extracted from the interference cycle of the sound intensity using a single hydrophone. The sound field interference patterns caused by sea-surface broadband noise sources in the shadow zone have been observed in a deep sea experiment in the South China Sea. The availability of the shadow zone sound field interference structure in the passive source range estimation is verified by experimental data. Compared with conventional matched field passive source localization method, this method doesn't need seafloor acoustic parameters and large scale computing of replica fields.
2017, 39(1): 46-51.
doi: 10.3969/j.issn.0253-4193.2017.01.005
Abstract:
According to drilling data, two layer's model is established by corresponding physical properties. Based on topographic data, here we use ANSYS software to simulate the gravitational stress field of TAG hydrothermal field. The result shows that, the hydrothermal vent locations are corresponding to the low stress area of the maximum horizontal stress. The stress of the active TAG doom area are characterized by local stress low surrounding by relative stress high, and the inactive MIR doom area without typical hydrothermal vent topography features located on unclosed area of the maximum horizontal stress low. Based on these conclusions, we predicted five places where the hydrothermal liquid probably flew out. According to drilling result, significant anhydrite was recovered in these areas, indicating that gravitational stress could be used for hydrothermal activity prediction.
According to drilling data, two layer's model is established by corresponding physical properties. Based on topographic data, here we use ANSYS software to simulate the gravitational stress field of TAG hydrothermal field. The result shows that, the hydrothermal vent locations are corresponding to the low stress area of the maximum horizontal stress. The stress of the active TAG doom area are characterized by local stress low surrounding by relative stress high, and the inactive MIR doom area without typical hydrothermal vent topography features located on unclosed area of the maximum horizontal stress low. Based on these conclusions, we predicted five places where the hydrothermal liquid probably flew out. According to drilling result, significant anhydrite was recovered in these areas, indicating that gravitational stress could be used for hydrothermal activity prediction.
2017, 39(1): 52-63.
doi: 10.3969/j.issn.0253-4193.2017.01.006
Abstract:
Based on the drilling data of the 15 wells in the Qiongdongnan Basin and "Xike-1" well in the Shi Island of Xisha Islands, combining with the seismic section through those wells, this passage systematically analyzed the subsiding (sediments filling) rates of Qiongdongnan Basin, the developing rates of the Xisha Islands' reefs and their variation features. Additionally, the coupling relationships among the Qinghai-Tibet Plateau uplifting, the Qiongdongnan Basin subsiding and the Xisha Islands' reefs developing were also discussed. The former three exhibit a high degree of consistency in development time and process. The ancient seawater Sr isotopic composition of the South China Sea composition provides an important evidence for this consistency. The changes of the sediment accumulation rates in the shallow water can better reflect the changes of the basin subsiding rates in comparison to the deep water. The processes of Qiongdongnan Basin subsiding (sediments accumulation) and Xisha Islands' reefs developing can both be divided into three stages, corresponding to the three phases of the Qinghai-Tibet Plateau uplifting, they are:23-16 Ma BP, 16-5.5 Ma BP, 5.5 Ma BP-today respectively in chronological order. In comparison, the coupling relationship between the reefs developing process and Qinghai-Tibet Plateau uplifting is more closely. In the rapid uplifting stage of the Qinghai-Tibet Plateau, the basin sedimentary filling (sediments accumulation) rates and the reefs growth rates accelerated correspondingly, and 87Sr/86Sr ratios of the South China Sea increased. It indicates that the Qinghai-Tibet Plateau uplifting is the main factor that impacted the basin subsidence (sedimentary fill), reefs development and ancient seawater Sr isotopic composition in the Qiongdongnan Basin even the entire South China Sea.
Based on the drilling data of the 15 wells in the Qiongdongnan Basin and "Xike-1" well in the Shi Island of Xisha Islands, combining with the seismic section through those wells, this passage systematically analyzed the subsiding (sediments filling) rates of Qiongdongnan Basin, the developing rates of the Xisha Islands' reefs and their variation features. Additionally, the coupling relationships among the Qinghai-Tibet Plateau uplifting, the Qiongdongnan Basin subsiding and the Xisha Islands' reefs developing were also discussed. The former three exhibit a high degree of consistency in development time and process. The ancient seawater Sr isotopic composition of the South China Sea composition provides an important evidence for this consistency. The changes of the sediment accumulation rates in the shallow water can better reflect the changes of the basin subsiding rates in comparison to the deep water. The processes of Qiongdongnan Basin subsiding (sediments accumulation) and Xisha Islands' reefs developing can both be divided into three stages, corresponding to the three phases of the Qinghai-Tibet Plateau uplifting, they are:23-16 Ma BP, 16-5.5 Ma BP, 5.5 Ma BP-today respectively in chronological order. In comparison, the coupling relationship between the reefs developing process and Qinghai-Tibet Plateau uplifting is more closely. In the rapid uplifting stage of the Qinghai-Tibet Plateau, the basin sedimentary filling (sediments accumulation) rates and the reefs growth rates accelerated correspondingly, and 87Sr/86Sr ratios of the South China Sea increased. It indicates that the Qinghai-Tibet Plateau uplifting is the main factor that impacted the basin subsidence (sedimentary fill), reefs development and ancient seawater Sr isotopic composition in the Qiongdongnan Basin even the entire South China Sea.
2017, 39(1): 64-75.
doi: 10.3969/j.issn.0253-4193.2017.01.007
Abstract:
To achieve a more robust understanding of the transport pattern of silt components in offshore areas, the grain size characteristics of 783 surface samples of fine-grained sediments are used to interpret the sediment transport pathways and predominant sedimentological conditions offshore the Shandong Peninsula, Yellow Sea. Based on the variation in the grain size composition, a regional "silt fractionation" was observed, and the very fine silt (VFSt) and the fine silt (FSt) displayed similar dynamic behaviors to that of the clay fraction during transportation and deposition, and these silts all acted as flocs. By contrast, the coarse silt (CSt) was primarily transported and deposited as single grains, indicating that the CSt content was the environmentally sensitive component in the sediments in the study area. The sediments displayed complicated sources based on the grain size analysis. In the northern part of the study area, the fine-grained sediment primarily originated from the Huanghe River Estuary (suspended or reworked, whereas in the eastern Shandong Peninsula, the sediments of the mud wedge were primarily composed of Huanghe-derived sediments and characterized by CSt-enriched, and in the southern Shandong Peninsula, the sediments primarily originated from the small rivers nearby. The marine fronts in the study area were thought to be the major factor controlling the settling and deposition of coarse silt. Further study should be carried out on the mechanisms that the fronts control the deposition of silty fractions in shelf settings.
To achieve a more robust understanding of the transport pattern of silt components in offshore areas, the grain size characteristics of 783 surface samples of fine-grained sediments are used to interpret the sediment transport pathways and predominant sedimentological conditions offshore the Shandong Peninsula, Yellow Sea. Based on the variation in the grain size composition, a regional "silt fractionation" was observed, and the very fine silt (VFSt) and the fine silt (FSt) displayed similar dynamic behaviors to that of the clay fraction during transportation and deposition, and these silts all acted as flocs. By contrast, the coarse silt (CSt) was primarily transported and deposited as single grains, indicating that the CSt content was the environmentally sensitive component in the sediments in the study area. The sediments displayed complicated sources based on the grain size analysis. In the northern part of the study area, the fine-grained sediment primarily originated from the Huanghe River Estuary (suspended or reworked, whereas in the eastern Shandong Peninsula, the sediments of the mud wedge were primarily composed of Huanghe-derived sediments and characterized by CSt-enriched, and in the southern Shandong Peninsula, the sediments primarily originated from the small rivers nearby. The marine fronts in the study area were thought to be the major factor controlling the settling and deposition of coarse silt. Further study should be carried out on the mechanisms that the fronts control the deposition of silty fractions in shelf settings.
2017, 39(1): 76-88.
doi: 10.3969/j.issn.0253-4193.2017.01.008
Abstract:
New evidence of the geomorphic evolution in the Yalu River estuary and coupling effects between water, sand, estuarine deposit and coastal development were explored, based on the analysis of 210Pb and 137Cs dating and the granularity of the 5 sediment cores collected from the Main Branch of the Yalu River estuary and the formerly studied 4 sediment cores collected in the tidal flat of western coasts and the West Branch. The results indicated that the fluvial action and the tidal action individually dominated the different sedimentary periods in the Main Branch;and the deposit dominated by the tidal action in the Main Branch was in accord with those in the West Branch and the adjacent western coasts in the Yalu River estuary. The material sources in the Main Branch were different from the West Branch and the western coasts. For the sedimentary records in the Main Branch, West Branch and the western coasts were all coupled with the environmental changes, the human activities, and the watershed events like the floods, and the responding time was basically synchronous. 5 obvious "event signals" appeared the sedimentary records, and the year of 1960 was the most important time when the estuarine geomorphy changed greatly.
New evidence of the geomorphic evolution in the Yalu River estuary and coupling effects between water, sand, estuarine deposit and coastal development were explored, based on the analysis of 210Pb and 137Cs dating and the granularity of the 5 sediment cores collected from the Main Branch of the Yalu River estuary and the formerly studied 4 sediment cores collected in the tidal flat of western coasts and the West Branch. The results indicated that the fluvial action and the tidal action individually dominated the different sedimentary periods in the Main Branch;and the deposit dominated by the tidal action in the Main Branch was in accord with those in the West Branch and the adjacent western coasts in the Yalu River estuary. The material sources in the Main Branch were different from the West Branch and the western coasts. For the sedimentary records in the Main Branch, West Branch and the western coasts were all coupled with the environmental changes, the human activities, and the watershed events like the floods, and the responding time was basically synchronous. 5 obvious "event signals" appeared the sedimentary records, and the year of 1960 was the most important time when the estuarine geomorphy changed greatly.
2017, 39(1): 89-95.
doi: 10.3969/j.issn.0253-4193.2017.01.009
Abstract:
The liquefaction of silty seabed is one of the disasters that would threaten the stability of offshore platforms, subsea pipelines and other marine structures. The boundary wave pressure caused by liquefied soil to the following seabed is a significant parameter when it comes to the calculation of pore water pressure and the liquefaction depth which should be taken into account during the structures design. Boundary wave pressure expressions with viscidity of seabed soil considered are deducted in this study, basing on the wave-induced silty seabed liquefaction top-down progressive mode and double fluid wave theory. The analysis of comparison with the boundary wave pressure without viscidity of seabed soil is also submitted. The results indicate that the viscidity of liquefied soil is a great factor of influencing the boundary wave pressure, and then would affect the determination of the liquefaction depth.
The liquefaction of silty seabed is one of the disasters that would threaten the stability of offshore platforms, subsea pipelines and other marine structures. The boundary wave pressure caused by liquefied soil to the following seabed is a significant parameter when it comes to the calculation of pore water pressure and the liquefaction depth which should be taken into account during the structures design. Boundary wave pressure expressions with viscidity of seabed soil considered are deducted in this study, basing on the wave-induced silty seabed liquefaction top-down progressive mode and double fluid wave theory. The analysis of comparison with the boundary wave pressure without viscidity of seabed soil is also submitted. The results indicate that the viscidity of liquefied soil is a great factor of influencing the boundary wave pressure, and then would affect the determination of the liquefaction depth.
2017, 39(1): 96-103.
doi: 10.3969/j.issn.0253-4193.2017.01.010
Abstract:
Based on potential flow theory, a numerical wave flume was founded to model the interaction of nonlinear waves and dual or triple submerged horizontal cylinders by using a time-domain higher-order boundary element method. The mixed Eulerian-Lagrangian technique was used for the refresh of free surface, and the 4th-order Runga-Kutta scheme was adopted for the time advance. The two-point method was adopted to separate the higher free harmonics from the downstream waves. Then the effects of interval of submerged objects and distribution scheme on the higher free harmonics were investigated. Meanwhile, physical tests were carried out for higher harmonics induced by multiple submerged objects in a wave flume. Good agreements between the numerical results and experimental data were obtained. It was found that higher free harmonic amplitude oscillates periodically with the variation of the interval in the dual cylinder system. And the reoccurrence interval is near to half wave length. In the triple cylinder system, higher free harmonics amplitude oscillates periodically with the first interval but decreases with the second interval.
Based on potential flow theory, a numerical wave flume was founded to model the interaction of nonlinear waves and dual or triple submerged horizontal cylinders by using a time-domain higher-order boundary element method. The mixed Eulerian-Lagrangian technique was used for the refresh of free surface, and the 4th-order Runga-Kutta scheme was adopted for the time advance. The two-point method was adopted to separate the higher free harmonics from the downstream waves. Then the effects of interval of submerged objects and distribution scheme on the higher free harmonics were investigated. Meanwhile, physical tests were carried out for higher harmonics induced by multiple submerged objects in a wave flume. Good agreements between the numerical results and experimental data were obtained. It was found that higher free harmonic amplitude oscillates periodically with the variation of the interval in the dual cylinder system. And the reoccurrence interval is near to half wave length. In the triple cylinder system, higher free harmonics amplitude oscillates periodically with the first interval but decreases with the second interval.
2017, 39(1): 104-110.
doi: 10.3969/j.issn.0253-4193.2017.01.011
Abstract:
Compared with the mild slope equation, the bottom curvature and slope-squared terms are contained in the modified mild slope equation, which increases the complexity of solving the equation numerically. In this paper, the physical domain is divided into a finite inner region and an infinite outer region. The inner region of a variable depth is studied with the modified mild slope equation, and the outer region has a constant water depth, the velocity potential satisfying the Helmholtz equation. The bottom curvature and slope-squared terms in the equation are evaluated from the input bathymetry at each node of every element using the interpolation functions. With the boundary matching method and Gaussian elimination technique, the finite element equations are established and solved. Then, wave transformation over a Homma Island and a circular shoal is simulated respectively, and the results agree well with analytical solutions and experimental data, verifying the validity of the FEM model in this paper. Meanwhile, the comparison between the numerical and experimental results indicates the modified mild slope equation can provide more accurate predictions than the mild slope equation for wave propagation over relatively steep bathymetry.
Compared with the mild slope equation, the bottom curvature and slope-squared terms are contained in the modified mild slope equation, which increases the complexity of solving the equation numerically. In this paper, the physical domain is divided into a finite inner region and an infinite outer region. The inner region of a variable depth is studied with the modified mild slope equation, and the outer region has a constant water depth, the velocity potential satisfying the Helmholtz equation. The bottom curvature and slope-squared terms in the equation are evaluated from the input bathymetry at each node of every element using the interpolation functions. With the boundary matching method and Gaussian elimination technique, the finite element equations are established and solved. Then, wave transformation over a Homma Island and a circular shoal is simulated respectively, and the results agree well with analytical solutions and experimental data, verifying the validity of the FEM model in this paper. Meanwhile, the comparison between the numerical and experimental results indicates the modified mild slope equation can provide more accurate predictions than the mild slope equation for wave propagation over relatively steep bathymetry.
2017, 39(1): 111-120.
doi: 10.3969/j.issn.0253-4193.2017.01.012
Abstract:
In order to determine the absolute bias of HY-2A sea surface height (SSH) and monitor the on-orbit working conditions of HY-2A Satellite altimeter, we conducted the absolute calibration experiments in the Qianliyan and Dangan area of China. In this study we adopted two independent methods which are deploying the GNSS buoy under satellite tracks for simultaneous observation and using the tide gauge data combined with the precise geoid model. In addition, for verifying the accuracy of the GNSS buoy calibration method, the Jason-2 and Saral Satellite altimeters, which were already calibrated by international calibration sites, were also calibrated using the same GNSS buoy. The SSH accuracy of the GNSS buoy is estimated to be about 2 cm by comparison with the tide gauge data. The absolute biases of Jason-2 and Saral calibrated by the GNSS buoy are 5.7 cm and -2.3 cm, which are in accordance with the results of the international calibration sites. According to the GNSS buoy the SSH absolute biases for HY-2 are determined to be -65 cm in September 2014 and -91 cm in May 2015, which are changed significantly for the two experiments. Thus in order to quantify the drift velocity of HY-2A SSH and assess the on-orbit working conditions of HY-2A Satellite altimeter more accurately, we used long time series of tide gauge data of the Qianliyan oceanic station to calibrate the cycles 56 to 73 of HY-2A. The drift phenomenon of HY-2A SSH is confirmed by the long-time series altimeter data and the drift velocity is estimated to be -51 cm/a. By the regression analysis with 95% confidence coefficient, the GNSS buoy calibration result of HY-2A is in good accordance with the result from the tide gauge data. From the result of this paper, we conclude that under the condition of no dedicate calibration site the altimeter absolute bias could be determined by GNSS buoy with flexibility and high accuracy and the drift of absolute bias could be quantified by the tide gauge data combined with the precise geoid mode.
In order to determine the absolute bias of HY-2A sea surface height (SSH) and monitor the on-orbit working conditions of HY-2A Satellite altimeter, we conducted the absolute calibration experiments in the Qianliyan and Dangan area of China. In this study we adopted two independent methods which are deploying the GNSS buoy under satellite tracks for simultaneous observation and using the tide gauge data combined with the precise geoid model. In addition, for verifying the accuracy of the GNSS buoy calibration method, the Jason-2 and Saral Satellite altimeters, which were already calibrated by international calibration sites, were also calibrated using the same GNSS buoy. The SSH accuracy of the GNSS buoy is estimated to be about 2 cm by comparison with the tide gauge data. The absolute biases of Jason-2 and Saral calibrated by the GNSS buoy are 5.7 cm and -2.3 cm, which are in accordance with the results of the international calibration sites. According to the GNSS buoy the SSH absolute biases for HY-2 are determined to be -65 cm in September 2014 and -91 cm in May 2015, which are changed significantly for the two experiments. Thus in order to quantify the drift velocity of HY-2A SSH and assess the on-orbit working conditions of HY-2A Satellite altimeter more accurately, we used long time series of tide gauge data of the Qianliyan oceanic station to calibrate the cycles 56 to 73 of HY-2A. The drift phenomenon of HY-2A SSH is confirmed by the long-time series altimeter data and the drift velocity is estimated to be -51 cm/a. By the regression analysis with 95% confidence coefficient, the GNSS buoy calibration result of HY-2A is in good accordance with the result from the tide gauge data. From the result of this paper, we conclude that under the condition of no dedicate calibration site the altimeter absolute bias could be determined by GNSS buoy with flexibility and high accuracy and the drift of absolute bias could be quantified by the tide gauge data combined with the precise geoid mode.
2017, 39(1): 121-129.
doi: 10.3969/j.issn.0253-4193.2017.01.013
Abstract:
Coastline is boundary line of land and sea, it is also an ecotone between land ecosystem and marine ecosystem. This paper employ GF-1 Satellite remote sensing images to monitor land boundary line at time of high tide and low tide, and create a tidal zone completeness index. The coastline is divided into natural coastline, artificial coastline with basic ecological function, artificial coastline with part ecological function, artificial coastline with limited ecological function, artificial coastline with few ecological function and artificial coastline with none ecological function based on tidal zone completeness index. Then the ecological index of coastline is established to evaluate the ecological condition of coastline in regional scale. The coastline in Yingkou is dominated by artificial coastline with none ecological function, natural coastline and artificial coastline with few ecological function. Their length is account for 45.74%, 18.31% and 15.53% of total coastline in Yingkou. The ecological index of coastline for total region is 0.29, and exist difference in sub-regions of Xicheng, Liaobian, Gaizhoubei, Bayuquan, Gaizhounan with value of 0.55, 0.17, 0.40, 0.10 and 0.55.
Coastline is boundary line of land and sea, it is also an ecotone between land ecosystem and marine ecosystem. This paper employ GF-1 Satellite remote sensing images to monitor land boundary line at time of high tide and low tide, and create a tidal zone completeness index. The coastline is divided into natural coastline, artificial coastline with basic ecological function, artificial coastline with part ecological function, artificial coastline with limited ecological function, artificial coastline with few ecological function and artificial coastline with none ecological function based on tidal zone completeness index. Then the ecological index of coastline is established to evaluate the ecological condition of coastline in regional scale. The coastline in Yingkou is dominated by artificial coastline with none ecological function, natural coastline and artificial coastline with few ecological function. Their length is account for 45.74%, 18.31% and 15.53% of total coastline in Yingkou. The ecological index of coastline for total region is 0.29, and exist difference in sub-regions of Xicheng, Liaobian, Gaizhoubei, Bayuquan, Gaizhounan with value of 0.55, 0.17, 0.40, 0.10 and 0.55.
2017, 39(1): 130-137.
doi: 10.3969/j.issn.0253-4193.2017.01.014
Abstract:
This paper reviews current fusion techniques used for bathymetry data, introduces the "Splines-in-Tension" interpolation and "remove-restore" techniques for bathymetry fusion. Based on these techniques, high-resolution digital bathymetric model is built using multi-beam, single-beam and historical charts data sets. In addition, facing the lack of error estimates for the interpolated grid points, the paper uses split-sample method to assess the uncertainty of the result for reliability. It shows a satisfied result with error percent about 0.5% both in sparse and dense areas, preserving the detail information of high-resolution data, possessing the vivid characteristics of the sea bottom. The whole techniques can be applied in multi-sources data fusion and combination.
This paper reviews current fusion techniques used for bathymetry data, introduces the "Splines-in-Tension" interpolation and "remove-restore" techniques for bathymetry fusion. Based on these techniques, high-resolution digital bathymetric model is built using multi-beam, single-beam and historical charts data sets. In addition, facing the lack of error estimates for the interpolated grid points, the paper uses split-sample method to assess the uncertainty of the result for reliability. It shows a satisfied result with error percent about 0.5% both in sparse and dense areas, preserving the detail information of high-resolution data, possessing the vivid characteristics of the sea bottom. The whole techniques can be applied in multi-sources data fusion and combination.
2017, 39(1): 138-147.
doi: 10.3969/j.issn.0253-4193.2017.01.015
Abstract:
How to recognize submarine landslides and quickly and accurately obtain their geometric information is the key issue concerned in marine engineering geology, especially in the deep-water sea. According to the terrain morphology formed after landsliding, we proposed in this paper a rapid method to recognize the submarine landslides based on the principle of water depth gradient and programmed using Matlab to conduct the calculation. As a case of the Baiyun deep-water area, north slope of the South China Sea, we recognized marine landslides using the proposed method. Some of these landslides were verified in sub-bottom profiles suggesting the feasibility of the new method. This approch can recognize submarine landslides automatically, so it is efficient and suitable for small landslides with numerous amount. Two factors are shown to influence the recognition result. One is the threshold value in calculation which can be determined through testing in combination with geophysical data, i.e. Sub-bottom profile and sonic image, and the other is the spatial resolution of water depth. A reasonable spatial resolution will be helpful to improve the accuracy of the recognition result.
How to recognize submarine landslides and quickly and accurately obtain their geometric information is the key issue concerned in marine engineering geology, especially in the deep-water sea. According to the terrain morphology formed after landsliding, we proposed in this paper a rapid method to recognize the submarine landslides based on the principle of water depth gradient and programmed using Matlab to conduct the calculation. As a case of the Baiyun deep-water area, north slope of the South China Sea, we recognized marine landslides using the proposed method. Some of these landslides were verified in sub-bottom profiles suggesting the feasibility of the new method. This approch can recognize submarine landslides automatically, so it is efficient and suitable for small landslides with numerous amount. Two factors are shown to influence the recognition result. One is the threshold value in calculation which can be determined through testing in combination with geophysical data, i.e. Sub-bottom profile and sonic image, and the other is the spatial resolution of water depth. A reasonable spatial resolution will be helpful to improve the accuracy of the recognition result.
Email alert
RSS