2020 Vol. 42, No. 1
Display Method:
2020, 42(1): .
Abstract:
2020, 42(1): 1-11.
doi: 10.3969/j.issn.0253-4193.2020.01.001
Abstract:
Two moorings (Station A, 20.736°N, 117.745°E, 1 249 m; Station B, 20.835°N, 117.56°E, 848 m) were located near the Dongsha Islands in the northern of the South China Sea from August to September 2014. Based on the measured data, we have studied the characteristics of near-inertial oscillations (NIOs) induced by typhoons, and analyzed the modulation of mesoscale warm eddy on the near-inertial frequency and its influence on the distribution and propagation of near-inertial kinetic energy (NIKE).The frequency of the NIOs at Station A (B) is 0.659 2 circle per day< at depths shallower than 142 (175) m with a redshift of 7.2% (7.6%) from the local initial frequency of 0.710 1 (0.713 3) circle per day, which is consistent with their background vorticities. The mesoscale warm eddy changes the stratification, which causes the NIKE of the two stations modified by 0.5−3 times in different stratifications. The refraction effect of stratification on energy makes the NIKE relatively concentrate with small decay between 158 and 223 m at Station B but rapidly decrease at Station A. The vertical group velocities of near-inertial internal waves at Station A and Station B are approximately 15.2 m/d and 14.1 m/d. Ignore the loss of NIKE in horizontal direction, their vertical propagation causes approximately 47% and 38% of NIKE decay in vertical direction, respectively.spectively.
Two moorings (Station A, 20.736°N, 117.745°E, 1 249 m; Station B, 20.835°N, 117.56°E, 848 m) were located near the Dongsha Islands in the northern of the South China Sea from August to September 2014. Based on the measured data, we have studied the characteristics of near-inertial oscillations (NIOs) induced by typhoons, and analyzed the modulation of mesoscale warm eddy on the near-inertial frequency and its influence on the distribution and propagation of near-inertial kinetic energy (NIKE).The frequency of the NIOs at Station A (B) is 0.659 2 circle per day< at depths shallower than 142 (175) m with a redshift of 7.2% (7.6%) from the local initial frequency of 0.710 1 (0.713 3) circle per day, which is consistent with their background vorticities. The mesoscale warm eddy changes the stratification, which causes the NIKE of the two stations modified by 0.5−3 times in different stratifications. The refraction effect of stratification on energy makes the NIKE relatively concentrate with small decay between 158 and 223 m at Station B but rapidly decrease at Station A. The vertical group velocities of near-inertial internal waves at Station A and Station B are approximately 15.2 m/d and 14.1 m/d. Ignore the loss of NIKE in horizontal direction, their vertical propagation causes approximately 47% and 38% of NIKE decay in vertical direction, respectively.spectively.
2020, 42(1): 12-21.
doi: 10.3969/j.issn.0253-4193.2020.01.002
Abstract:
Based on the repeated short-term shipboard Acoustic Doppler Current Profiler (ADCP) surveys of three sections around the coastal area of Hongyanhe Nuclear Power Station, the L-curve method was used to separate tidal and residual current. The relationship between the movement of water masses and the direction of residual currents was analyzed and the characteristics of tidal currents were compared with literatures. Regression analysis of flow field verified that L-curve method for de-tiding under this situation was reasonable. The results suggested that: (1) The tidal current characteristics separated by L-curve method were in good agreement with the previous observations, and the semi-diurnal and diurnal tidal current components can be separated effectively, but all of data used in this paper were less than typical diurnal period. Therefore, the results of diurnal current and dynamic analysis of the flow field were still unreasonable. We need to use observations with longer time and more repetitions to correct the deficiency. (2) The residual currents flew to southward nearshore and northward offshore, which was consistent with colder saltier water intruding from south in deep water and warm fresh water run from north along the coastline. (3) The regression values derived from the L-curve method were highly correlated with the measured instantaneous velocity. The root mean square error (RMSE) was about 6 cm/s, and the relative error was about 10%. L-curve method can be extended to de-tide at any critical sections to obtain the important information such as coastal circulation variation and material transport fluxes to estimate the water exchange and resident time.
Based on the repeated short-term shipboard Acoustic Doppler Current Profiler (ADCP) surveys of three sections around the coastal area of Hongyanhe Nuclear Power Station, the L-curve method was used to separate tidal and residual current. The relationship between the movement of water masses and the direction of residual currents was analyzed and the characteristics of tidal currents were compared with literatures. Regression analysis of flow field verified that L-curve method for de-tiding under this situation was reasonable. The results suggested that: (1) The tidal current characteristics separated by L-curve method were in good agreement with the previous observations, and the semi-diurnal and diurnal tidal current components can be separated effectively, but all of data used in this paper were less than typical diurnal period. Therefore, the results of diurnal current and dynamic analysis of the flow field were still unreasonable. We need to use observations with longer time and more repetitions to correct the deficiency. (2) The residual currents flew to southward nearshore and northward offshore, which was consistent with colder saltier water intruding from south in deep water and warm fresh water run from north along the coastline. (3) The regression values derived from the L-curve method were highly correlated with the measured instantaneous velocity. The root mean square error (RMSE) was about 6 cm/s, and the relative error was about 10%. L-curve method can be extended to de-tide at any critical sections to obtain the important information such as coastal circulation variation and material transport fluxes to estimate the water exchange and resident time.
2020, 42(1): 22-30.
doi: 10.3969/j.issn.0253-4193.2020.01.003
Abstract:
There are hundreds of islands and reefs in Nansha Islands. Most of them are characterized by steep seaward slope and gentle outer reef flat. The wave-facing topography of reefs were generalized to a pair of slopes. FUNWAVE-TVD was adopted to simulate shoaling and breaking. Breaking wave heights simulated by the model were analyzed. The slope of seaward slopes has little influence on surf. The breaking wave height on the outer reef flat only increases slightly as the slope increases. The water depth at the turning of the seaward slope and the out reef flat (i.e. the turning point of the slope) has relatively obvious influence on the surf. The breaking wave height decreases with the increasing of water depth at the turning point. The breaker height will also increase with the increasing of incident wave height and wave period. Five statistical models of breaking wave heights compared with the simulating results. Three types of new statistical models are also established based on the simulating result. The results of error calculation show that these models have good applicability.
There are hundreds of islands and reefs in Nansha Islands. Most of them are characterized by steep seaward slope and gentle outer reef flat. The wave-facing topography of reefs were generalized to a pair of slopes. FUNWAVE-TVD was adopted to simulate shoaling and breaking. Breaking wave heights simulated by the model were analyzed. The slope of seaward slopes has little influence on surf. The breaking wave height on the outer reef flat only increases slightly as the slope increases. The water depth at the turning of the seaward slope and the out reef flat (i.e. the turning point of the slope) has relatively obvious influence on the surf. The breaking wave height decreases with the increasing of water depth at the turning point. The breaker height will also increase with the increasing of incident wave height and wave period. Five statistical models of breaking wave heights compared with the simulating results. Three types of new statistical models are also established based on the simulating result. The results of error calculation show that these models have good applicability.
2020, 42(1): 31-39.
doi: 10.3969/j.issn.0253-4193.2020.01.004
Abstract:
In this paper, two numerical models of elliptic mild-slope equation for coastal wave propagation in coastal zones are compared and analyzed. The two numerical models are developed by using finite volume method respectively on adaptive quadtree mesh and triangular unstructured mesh. The numerical models are firstly used to simulate wave propagation and deformation on circle and elliptic shores, and the computational efficiencies are compared and analyzed based on the numerical results. The numerical results show that both of the two numerical models are effective in simulating coastal wave propagation and deformation. Compared with the numerical model on unstructured triangular mesh, the numerical model on quadtree mesh is more concise and easy for numerical implementation as it does not involve complex cross-terms due to model transformation in the process of numerical discretization. What’s more, the numerical model on quadtree mesh is more efficiency in saving computing time and storage space.
In this paper, two numerical models of elliptic mild-slope equation for coastal wave propagation in coastal zones are compared and analyzed. The two numerical models are developed by using finite volume method respectively on adaptive quadtree mesh and triangular unstructured mesh. The numerical models are firstly used to simulate wave propagation and deformation on circle and elliptic shores, and the computational efficiencies are compared and analyzed based on the numerical results. The numerical results show that both of the two numerical models are effective in simulating coastal wave propagation and deformation. Compared with the numerical model on unstructured triangular mesh, the numerical model on quadtree mesh is more concise and easy for numerical implementation as it does not involve complex cross-terms due to model transformation in the process of numerical discretization. What’s more, the numerical model on quadtree mesh is more efficiency in saving computing time and storage space.
2020, 42(1): 40-45.
doi: 10.3969/j.issn.0253-4193.2020.01.005
Abstract:
Transoceanic tsunami guided by oceanic ridges can propagate to tens of thousands of kilometers away in the form of trapped waves, which threatens the safety in far field. MIKE21-BW was used to simulate trapped waves propagation over ocean ridge with curved degree varying from 0° (straight ridge) to 90° (right-angle ridge) and the energy distribution was examined. The results show that when the trapped waves propagate to the bend of ocean ridge, a little part of the energy leaks out of it and scatters in the other area as free waves. Some of the energy is reflected back and propagate along the ocean ridge in the opposite direction, and it increases with the curved angle of the ocean ridge. The other energy continues to propagate along the curved ocean ridge and it increases with the curved angle of the ocean ridge.
Transoceanic tsunami guided by oceanic ridges can propagate to tens of thousands of kilometers away in the form of trapped waves, which threatens the safety in far field. MIKE21-BW was used to simulate trapped waves propagation over ocean ridge with curved degree varying from 0° (straight ridge) to 90° (right-angle ridge) and the energy distribution was examined. The results show that when the trapped waves propagate to the bend of ocean ridge, a little part of the energy leaks out of it and scatters in the other area as free waves. Some of the energy is reflected back and propagate along the ocean ridge in the opposite direction, and it increases with the curved angle of the ocean ridge. The other energy continues to propagate along the curved ocean ridge and it increases with the curved angle of the ocean ridge.
2020, 42(1): 46-53.
doi: 10.3969/j.issn.0253-4193.2020.01.006
Abstract:
In September 2015, Typhoon Chan-hom passed over the buoy named QF111 that can record the ocean temperature and current in the Yellow Sea. Affected by the typhoon, the drop of the sea surface temperatures is obvious, the cooling rate is in 2−4℃, and there formed low temperature patches below 20℃ at the right side of the typhoon path. The current increased during the transit of the typhoon, the velocity is up to 1.2−1.5 m/s, presenting the characteristics of reinforcement from the surface to the bottom. The result that wind did the work to the ocean indicates that wind always input the energy to the ocean, it reached the largest during typhoon transited, and the rotate power spectrum analysis results show that the energy from the wind spread to the ocean interior. The inertial oscillation inspired by the typhoon damp faster in the Yellow Sea, according to the evolution of the inertia horizontal kinetic energy, the e-folding time of the inertial oscillation is about two days.
In September 2015, Typhoon Chan-hom passed over the buoy named QF111 that can record the ocean temperature and current in the Yellow Sea. Affected by the typhoon, the drop of the sea surface temperatures is obvious, the cooling rate is in 2−4℃, and there formed low temperature patches below 20℃ at the right side of the typhoon path. The current increased during the transit of the typhoon, the velocity is up to 1.2−1.5 m/s, presenting the characteristics of reinforcement from the surface to the bottom. The result that wind did the work to the ocean indicates that wind always input the energy to the ocean, it reached the largest during typhoon transited, and the rotate power spectrum analysis results show that the energy from the wind spread to the ocean interior. The inertial oscillation inspired by the typhoon damp faster in the Yellow Sea, according to the evolution of the inertia horizontal kinetic energy, the e-folding time of the inertial oscillation is about two days.
A statistical analysis on cyclonic gale processes along Chinese Antarctic Research Expedition routes
2020, 42(1): 54-66.
doi: 10.3969/j.issn.0253-4193.2020.01.007
Abstract:
Using the meteorological observation data and SeaSpace polar-orbiting satellite images collected on the R/V Xuelong, in conjunction with the ERA-Interim reanalysis data, this paper studies the cyclonic gale processes (CGPs) that occurred in the 19th to 34th Chinese Antarctic Research Expedition (CHINARE-Antarctic). The characteristics of the number, occurrence interval, intensity, and spatial distribution are analyzed statistically. And the relationship between occurrence interval of CGPs and the Antarctic Oscillation (AAO) is discussed. The Southern Ocean cyclones have frequent and strong impacts on the CHINARE-Antarctic routes. A significant positive correlation can be seen between CGPs number and the time duration of voyages. On average, there are about 18 (4) CGPs (strong ones) per voyage, which occurs once every 6.5(30) days, and the average wind speed during CGPs reaches Beaufort wind scale 8, while the maximum of which can reach scale 12. However, the number, occurrence interval and maximum wind speed of CGPs vary significantly during different voyages. There is a negative correlation between the occurrence interval of CGPs and the austral summer AAO index, which is significant for the CGPs appeared over the poleward side of 55°S. AAO adjusts the strength of the mid-high latitude pressure regime and affects the number and active area of cyclone activities, which in turn affects the number and frequency of CGPs. The CGPs can occur in any segment of the Southern Ocean and Polar Region, with the most frequent occurrence over the circumpolar westerly in 45°~60°S, especially in the strong pressure gradient zone produced by the combination of the low-pressure system and the northern subtropical high. In the four key expedition areas around Antarctica, the CGP and strong CGP over the Amundsen Sea occur most frequently because of the strong Amundsen Sea Low, followed by the Antarctic Peninsula, while the Prydz Bay and Ross Sea CGPs are significantly lower than the former two regions. Compared with the Prydz Bay, the Ross Sea is less susceptible to cyclones due to its southernmost position.
Using the meteorological observation data and SeaSpace polar-orbiting satellite images collected on the R/V Xuelong, in conjunction with the ERA-Interim reanalysis data, this paper studies the cyclonic gale processes (CGPs) that occurred in the 19th to 34th Chinese Antarctic Research Expedition (CHINARE-Antarctic). The characteristics of the number, occurrence interval, intensity, and spatial distribution are analyzed statistically. And the relationship between occurrence interval of CGPs and the Antarctic Oscillation (AAO) is discussed. The Southern Ocean cyclones have frequent and strong impacts on the CHINARE-Antarctic routes. A significant positive correlation can be seen between CGPs number and the time duration of voyages. On average, there are about 18 (4) CGPs (strong ones) per voyage, which occurs once every 6.5(30) days, and the average wind speed during CGPs reaches Beaufort wind scale 8, while the maximum of which can reach scale 12. However, the number, occurrence interval and maximum wind speed of CGPs vary significantly during different voyages. There is a negative correlation between the occurrence interval of CGPs and the austral summer AAO index, which is significant for the CGPs appeared over the poleward side of 55°S. AAO adjusts the strength of the mid-high latitude pressure regime and affects the number and active area of cyclone activities, which in turn affects the number and frequency of CGPs. The CGPs can occur in any segment of the Southern Ocean and Polar Region, with the most frequent occurrence over the circumpolar westerly in 45°~60°S, especially in the strong pressure gradient zone produced by the combination of the low-pressure system and the northern subtropical high. In the four key expedition areas around Antarctica, the CGP and strong CGP over the Amundsen Sea occur most frequently because of the strong Amundsen Sea Low, followed by the Antarctic Peninsula, while the Prydz Bay and Ross Sea CGPs are significantly lower than the former two regions. Compared with the Prydz Bay, the Ross Sea is less susceptible to cyclones due to its southernmost position.
2020, 42(1): 67-77.
doi: 10.3969/j.issn.0253-4193.2020.01.008
Abstract:
Based on historical meteorological observation data and reanalysis data, the application of LSTM (longs short-term memory) deep neural network in short-term forecasting of sea surface wind speed under supervised learning was studied. Five representative meteorological stations in the offshore were taken as research areas. Twenty-one variables, which has been quality control and preprocessing, were selected as the prediction factors, and two LSTM deep neural network frameworks (OBS_LSTM and ALL_LSTM) were constructed. The 6 h wind speed forecast of WRF model over two-nesting domains in 2017 was included to validate the real performance of the proposed model. The result indicate that, the LSTM wind speed forecast models could significantly reduce the forecast error, RMSE was reduced by 41.3% and 38.8%, and MAE was reduced by 43.0% and 40.0%, respectively; wind speed error statistics and strong wind events comparison shows that, LSTM model can grasp sensitive information such as topography and typhoon, and superior to WRF model. The ALL_LSTM model has the smallest prediction error, good stability and robustness, and OBS_LSTM model has a wider range of application.
Based on historical meteorological observation data and reanalysis data, the application of LSTM (longs short-term memory) deep neural network in short-term forecasting of sea surface wind speed under supervised learning was studied. Five representative meteorological stations in the offshore were taken as research areas. Twenty-one variables, which has been quality control and preprocessing, were selected as the prediction factors, and two LSTM deep neural network frameworks (OBS_LSTM and ALL_LSTM) were constructed. The 6 h wind speed forecast of WRF model over two-nesting domains in 2017 was included to validate the real performance of the proposed model. The result indicate that, the LSTM wind speed forecast models could significantly reduce the forecast error, RMSE was reduced by 41.3% and 38.8%, and MAE was reduced by 43.0% and 40.0%, respectively; wind speed error statistics and strong wind events comparison shows that, LSTM model can grasp sensitive information such as topography and typhoon, and superior to WRF model. The ALL_LSTM model has the smallest prediction error, good stability and robustness, and OBS_LSTM model has a wider range of application.
2020, 42(1): 136-143.
doi: 10.3969/j.issn.0253-4193.2020.01.014
Abstract:
There is a great significance to study the storm surge in the disaster prevention and mitigation of fishing port. This paper constructs a storm surge numerical model with the nested gird at Zhoushan fishing port, and the calculated results of astronomical tide and storm tide are in a good agreement with the practice. Fourteen typhoon paths in 5 directions are designed, and the storm tide level of Zhoushan fishing port is calculated under the typhoon of 12−17 level during the great tide period of August 8−12, 2017. The results show that storm tide peak in SE path on the south side is 35.7% higher than the north E path due to the effect of the shore wind, and the difference can reach 82 cm. The Zhoushan fishing port passes through sea at both ends, and the wind direction is consistent with the east exit door and oblique to the fishing port at 0.5R SE path on the south side typhoon, which is beneficial to the water entering and staying. At this time, the storm tidal level is the highest. The 12 typhoon level of ESE, SE and SSE paths on the south side causes overflow. There is no risk of typhoon landing on the north side, and because of the settlement and other reasons, the seawalls’ defense capacities of two sides are lower than the middle section. According to numerical experiments, when a spur dike is installed on the east side of Xiaogan Island, the probability of overflow under the situation of the 17 typhoon level can be reduced from 26.23% to 10.66%.
There is a great significance to study the storm surge in the disaster prevention and mitigation of fishing port. This paper constructs a storm surge numerical model with the nested gird at Zhoushan fishing port, and the calculated results of astronomical tide and storm tide are in a good agreement with the practice. Fourteen typhoon paths in 5 directions are designed, and the storm tide level of Zhoushan fishing port is calculated under the typhoon of 12−17 level during the great tide period of August 8−12, 2017. The results show that storm tide peak in SE path on the south side is 35.7% higher than the north E path due to the effect of the shore wind, and the difference can reach 82 cm. The Zhoushan fishing port passes through sea at both ends, and the wind direction is consistent with the east exit door and oblique to the fishing port at 0.5R SE path on the south side typhoon, which is beneficial to the water entering and staying. At this time, the storm tidal level is the highest. The 12 typhoon level of ESE, SE and SSE paths on the south side causes overflow. There is no risk of typhoon landing on the north side, and because of the settlement and other reasons, the seawalls’ defense capacities of two sides are lower than the middle section. According to numerical experiments, when a spur dike is installed on the east side of Xiaogan Island, the probability of overflow under the situation of the 17 typhoon level can be reduced from 26.23% to 10.66%.
2020, 42(1): 78-89.
doi: 10.3969/j.issn.0253-4193.2020.01.009
Abstract:
In this study, sediment grain size of a core retrieved from Shandong mud wedge has been tested. On the basis of 210Pb dating, the impacts of channel shifts and changes of annual sediment load of the Yellow River on the sedimentary characteristics of the remote depositional zone over the past 100 years have been studied by analyzing the temporal changes of grain size in the core, Yellow River's annual sediment load, particle size of suspended sediment in the lower reaches of the Yellow River, Yellow River estuary location, and replacement index of coastal current intensity. The results show that grain size of sediments in the study area is affected by characteristics of sediments input of the Yellow River and strength of coastal hydrodynamics. During the period 1884−1939 AD and 1947−1999 AD, the variation of grain-size characteristics in the area was mainly affected by strength of the coastal current. During the period 1939−1947 AD and 1999−2012 AD, sediments in this area were obviously coarsened, and their correlation with the coastal current intensity weakened. Such a coarsening trend of sediment is likely attributed to the insufficient sediment input of the Yellow River, because the Yellow River was cut down at the Huayuankou during 1938−1947 AD and the annual sediment load of the Yellow River was continuous lowering since the end of the 1990s. Different from proximal depositional zone, grain-size characteristics of this remote offshore depositional area was not sensitive to the channel shifts in the lower reaches of the Yellow River. A certain delay also existed in the response of sediment grain size to the reduction of annual sediment load. The reason was that sediment in this area was subjected to resuspension and complex material mixing. Channel shifts of the Yellow River and change of sediment load were still factors that could not be ignored for evolution of sedimentary characteristics of remote depositional zone.
In this study, sediment grain size of a core retrieved from Shandong mud wedge has been tested. On the basis of 210Pb dating, the impacts of channel shifts and changes of annual sediment load of the Yellow River on the sedimentary characteristics of the remote depositional zone over the past 100 years have been studied by analyzing the temporal changes of grain size in the core, Yellow River's annual sediment load, particle size of suspended sediment in the lower reaches of the Yellow River, Yellow River estuary location, and replacement index of coastal current intensity. The results show that grain size of sediments in the study area is affected by characteristics of sediments input of the Yellow River and strength of coastal hydrodynamics. During the period 1884−1939 AD and 1947−1999 AD, the variation of grain-size characteristics in the area was mainly affected by strength of the coastal current. During the period 1939−1947 AD and 1999−2012 AD, sediments in this area were obviously coarsened, and their correlation with the coastal current intensity weakened. Such a coarsening trend of sediment is likely attributed to the insufficient sediment input of the Yellow River, because the Yellow River was cut down at the Huayuankou during 1938−1947 AD and the annual sediment load of the Yellow River was continuous lowering since the end of the 1990s. Different from proximal depositional zone, grain-size characteristics of this remote offshore depositional area was not sensitive to the channel shifts in the lower reaches of the Yellow River. A certain delay also existed in the response of sediment grain size to the reduction of annual sediment load. The reason was that sediment in this area was subjected to resuspension and complex material mixing. Channel shifts of the Yellow River and change of sediment load were still factors that could not be ignored for evolution of sedimentary characteristics of remote depositional zone.
2020, 42(1): 144-153.
doi: 10.3969/j.issn.0253-4193.2020.01.015
Abstract:
Based on the measured data in the 30th, 32th of Chinese National Antarctic Research Expedition, combined with the reference data, this study processed 12 groups of data in study area and draw the gravity anomaly map, with all 386 crossovers among these cruises the standard deviation reaching ±1.53×10−5 m/s2. Compared to satellite gravity, the mean value of the difference is 1.49×10−5 m/s2, with the standard deviation is ±3.81×10−5 m/s2. On this basis, we used a frequency domain interface inversion method to calculate the Moho depth. It is contrary to sedimentary basins with low values of gravity anomaly, the gravity of the hinterland in the northern Ross Basin, the Victoria Basin, the Central Trough and the Eastern Basin is high, with a span of 100 km or more. The distribution of the Moho depth is generally high in the south and low in the north, ranging from 10 km to 28 km. Along with the multiple extensions and magmatism in the western part of the Ross Sea, the crustal thickness and Moho depth of the area show increasing differences, with interphase distribution of abnormal high and low values. Combining inverted depth of Moho and Gravity-Seismic inversion interpretation profile, we considered the long-wavelength variation of the gravity anomaly is positively correlated with the fluctuation of the Moho depth. However, the inversion Moho depth does not correspond exactly to the regional gravity field characteristics, so magma underplating and crustal intrusion are still insufficient to cause gravity anomalies or basin geometries in the Ross Sea Basin.
Based on the measured data in the 30th, 32th of Chinese National Antarctic Research Expedition, combined with the reference data, this study processed 12 groups of data in study area and draw the gravity anomaly map, with all 386 crossovers among these cruises the standard deviation reaching ±1.53×10−5 m/s2. Compared to satellite gravity, the mean value of the difference is 1.49×10−5 m/s2, with the standard deviation is ±3.81×10−5 m/s2. On this basis, we used a frequency domain interface inversion method to calculate the Moho depth. It is contrary to sedimentary basins with low values of gravity anomaly, the gravity of the hinterland in the northern Ross Basin, the Victoria Basin, the Central Trough and the Eastern Basin is high, with a span of 100 km or more. The distribution of the Moho depth is generally high in the south and low in the north, ranging from 10 km to 28 km. Along with the multiple extensions and magmatism in the western part of the Ross Sea, the crustal thickness and Moho depth of the area show increasing differences, with interphase distribution of abnormal high and low values. Combining inverted depth of Moho and Gravity-Seismic inversion interpretation profile, we considered the long-wavelength variation of the gravity anomaly is positively correlated with the fluctuation of the Moho depth. However, the inversion Moho depth does not correspond exactly to the regional gravity field characteristics, so magma underplating and crustal intrusion are still insufficient to cause gravity anomalies or basin geometries in the Ross Sea Basin.
2020, 42(1): 154-162.
doi: 10.3969/j.issn.0253-4193.2020.01.016
Abstract:
Using the multi-channel and multibeam bathymetry data collected in the eastern Taiwan sea area in recent years, the sedimentary and filling evolution characteristics of the Huatung Basin since the late Miocene in the eastern Taiwan sea area have been described and analyzed. Through the description of the regional topographic features of the Huatung Basin, the establishment of the sequence stratigraphic framework and the interpretation of seismic profiles, six types of seismic facies are identified in the Huatung Basin since the late Miocene, and their corresponding sedimentary facies types are analyzed, including turbidite fan, turbidite channels, mass transport deposits, sediment wave, slump deformation associated with canyon and deep-water fan. According to the plane distribution of seismic facies and vertical stacked patterns between sedimentary facies, the three phases of sedimentary evolution since the late Miocene in the Huatung Basin were rebuilt, which were mass transport deposits in the late Miocene, followed by sediments failures, erosion and sedimentation of submarine canyons and finally, a large number of sediments were unload and developed sediment wave, turbidite fan and deep water fan.
Using the multi-channel and multibeam bathymetry data collected in the eastern Taiwan sea area in recent years, the sedimentary and filling evolution characteristics of the Huatung Basin since the late Miocene in the eastern Taiwan sea area have been described and analyzed. Through the description of the regional topographic features of the Huatung Basin, the establishment of the sequence stratigraphic framework and the interpretation of seismic profiles, six types of seismic facies are identified in the Huatung Basin since the late Miocene, and their corresponding sedimentary facies types are analyzed, including turbidite fan, turbidite channels, mass transport deposits, sediment wave, slump deformation associated with canyon and deep-water fan. According to the plane distribution of seismic facies and vertical stacked patterns between sedimentary facies, the three phases of sedimentary evolution since the late Miocene in the Huatung Basin were rebuilt, which were mass transport deposits in the late Miocene, followed by sediments failures, erosion and sedimentation of submarine canyons and finally, a large number of sediments were unload and developed sediment wave, turbidite fan and deep water fan.
2020, 42(1): 90-101.
doi: 10.3969/j.issn.0253-4193.2020.01.010
Abstract:
In this paper, we conducted a study on deriving internal wave parameters and sea surface current velocity in the vicinity of Dongsha Island from spaceborne SAR data of TerraSAR-X (TSX), acquired on April 22, 2010. Based on the intensity data of the TSX scene, characteristic half width of the internal wave was obtained through the empirical mode decomposition method. Then amplitude and phase speed of the internal solitary wave were calculated using the two-layer model method and the parameterization method, respectively. The results suggested that the amplitude (approximately 21–39 m) acquired by the parameterization method and the phase speed (approximately 1.06 m/s) obtained by the two-layer model method were consistent with the historical measurements. Furthermore, the Doppler velocity in the research area was calculated using along-track interferometry data of the TSX scene. The M4S model and the direct-separation method were used to extract the sea surface current velocity. The mean sea surface current field of the study area obtained by the two methods were consistent, which were both of approximately 1.10 m/s. The M4S model led to more adjustments to maximum of the surface velocity whereas more adjustments to the minimum values were found in the direct-separation method. Moreover, it was found that the adjustment of surface current retrieval using the M4S model were more in the region of wave crest of the internal waves. Finally, based on the KdV equation, the velocity of internal-wave-induced surface flow is about 0.28 m/s, which contributes 23% to the retrieved sea surface current velocity.
In this paper, we conducted a study on deriving internal wave parameters and sea surface current velocity in the vicinity of Dongsha Island from spaceborne SAR data of TerraSAR-X (TSX), acquired on April 22, 2010. Based on the intensity data of the TSX scene, characteristic half width of the internal wave was obtained through the empirical mode decomposition method. Then amplitude and phase speed of the internal solitary wave were calculated using the two-layer model method and the parameterization method, respectively. The results suggested that the amplitude (approximately 21–39 m) acquired by the parameterization method and the phase speed (approximately 1.06 m/s) obtained by the two-layer model method were consistent with the historical measurements. Furthermore, the Doppler velocity in the research area was calculated using along-track interferometry data of the TSX scene. The M4S model and the direct-separation method were used to extract the sea surface current velocity. The mean sea surface current field of the study area obtained by the two methods were consistent, which were both of approximately 1.10 m/s. The M4S model led to more adjustments to maximum of the surface velocity whereas more adjustments to the minimum values were found in the direct-separation method. Moreover, it was found that the adjustment of surface current retrieval using the M4S model were more in the region of wave crest of the internal waves. Finally, based on the KdV equation, the velocity of internal-wave-induced surface flow is about 0.28 m/s, which contributes 23% to the retrieved sea surface current velocity.
2020, 42(1): 102-112.
doi: 10.3969/j.issn.0253-4193.2020.01.011
Abstract:
The typhoon wind profile information is a curve that directly reflects the relationship between the points at different distances from the typhoon center and the average wind speed. It is an important basis for determining the wind radius at different speed. In this paper, a new typhoon wind profile information extraction method is proposed by using the HY-2A microwave scatterometer sea surface wind field data and the Holland wind field model. We selected 16 typical typhoons during 2012−2017 for application, the results show that the average root mean square error of the 34 kt and 50 kt wind radii is 37.6 km and 18.3 km. This method has good applicability and accuracy. This study has certain practical significance for describing the structural characteristics of typhoon and its potential destructive power and possible range of typhoon.
The typhoon wind profile information is a curve that directly reflects the relationship between the points at different distances from the typhoon center and the average wind speed. It is an important basis for determining the wind radius at different speed. In this paper, a new typhoon wind profile information extraction method is proposed by using the HY-2A microwave scatterometer sea surface wind field data and the Holland wind field model. We selected 16 typical typhoons during 2012−2017 for application, the results show that the average root mean square error of the 34 kt and 50 kt wind radii is 37.6 km and 18.3 km. This method has good applicability and accuracy. This study has certain practical significance for describing the structural characteristics of typhoon and its potential destructive power and possible range of typhoon.
2020, 42(1): 113-122.
doi: 10.3969/j.issn.0253-4193.2020.01.012
Abstract:
Polar sea ice affects atmospheric and ocean circulation and it plays an important role in global climate change. The sea ice concentration is one of the important parameters to characterize the temporal and spatial variation of sea ice. The retrieval algorithm of sea ice concentration based on brightness temperature data of FY-3C microwave radiation imager in the polar region was studied. After the time-space matching and linear regression, FY-3C microwave radiometers brightness temperature data was corrected. The atmospheric effects were reduced using two weather filters and sea ice mask. A minimum ice concentration array used in the procedure reduced the land-to-ocean spillover effect. The sea ice concentration product was validated by calculating Arctic and Antarctic sea ice extent and area in 2016−2017. The sea ice extent and area trends of this two years were basically consistent with the NSIDC product, with an average difference of 3%. This research laid the foundation for the release of the polar sea ice concentration business products of China's autonomous satellites, and the products guarantee the continuity of crucial polar sea ice record that might soon be interrupted.
Polar sea ice affects atmospheric and ocean circulation and it plays an important role in global climate change. The sea ice concentration is one of the important parameters to characterize the temporal and spatial variation of sea ice. The retrieval algorithm of sea ice concentration based on brightness temperature data of FY-3C microwave radiation imager in the polar region was studied. After the time-space matching and linear regression, FY-3C microwave radiometers brightness temperature data was corrected. The atmospheric effects were reduced using two weather filters and sea ice mask. A minimum ice concentration array used in the procedure reduced the land-to-ocean spillover effect. The sea ice concentration product was validated by calculating Arctic and Antarctic sea ice extent and area in 2016−2017. The sea ice extent and area trends of this two years were basically consistent with the NSIDC product, with an average difference of 3%. This research laid the foundation for the release of the polar sea ice concentration business products of China's autonomous satellites, and the products guarantee the continuity of crucial polar sea ice record that might soon be interrupted.
2020, 42(1): 123-135.
doi: 10.3969/j.issn.0253-4193.2020.01.013
Abstract:
In the classification of sea ice remote sensing spectral images, labeled samples are obtained difficultly, which leads to difficulty improving the accuracy of sea ice classification. But a large number of unlabeled samples containing abundant information are not fully utilized. In view of this situation, a method combining active learning and semi-supervised learning is proposed to study the classification of sea ice remote sensing spectral images. The active learning part combines BVSB, SOM neural networks and ECBD algorithm to select representative samples containing uncertainty and diversity for training. The semi-supervised learning part integrates the idea of active learning use TSVM to select relatively reliable samples containing information from a large number of unlabeled samples for iterative training. Then, the results of classification and semi supervised classification are used cooperatively to guarantee the correctness of the pseudo-labeled samples through consistency verification. To verify the effectiveness of the method, Hyperion hyperspectral data with a resolution of 30 m in Baffin Bay area (the verification data is Landsat-8 data with a resolution of 15 m) and Landsat-8 data with a resolution of 15 m in Liaodong Bay (the verification data is Google Earth data with a resolution of 4.77 m) area are used for experiments of sea ice classification. The experimental results show that the cooperative classification method can make full use of the information contained in a large number of unlabeled samples in the case of a small number of label samples, and achieve rapid convergence higher classification accuracy (the overall accuracy is 90.003% and 93.288%, respectively), which verifies that the method is suitable for classification of sea ice remote sensing.
In the classification of sea ice remote sensing spectral images, labeled samples are obtained difficultly, which leads to difficulty improving the accuracy of sea ice classification. But a large number of unlabeled samples containing abundant information are not fully utilized. In view of this situation, a method combining active learning and semi-supervised learning is proposed to study the classification of sea ice remote sensing spectral images. The active learning part combines BVSB, SOM neural networks and ECBD algorithm to select representative samples containing uncertainty and diversity for training. The semi-supervised learning part integrates the idea of active learning use TSVM to select relatively reliable samples containing information from a large number of unlabeled samples for iterative training. Then, the results of classification and semi supervised classification are used cooperatively to guarantee the correctness of the pseudo-labeled samples through consistency verification. To verify the effectiveness of the method, Hyperion hyperspectral data with a resolution of 30 m in Baffin Bay area (the verification data is Landsat-8 data with a resolution of 15 m) and Landsat-8 data with a resolution of 15 m in Liaodong Bay (the verification data is Google Earth data with a resolution of 4.77 m) area are used for experiments of sea ice classification. The experimental results show that the cooperative classification method can make full use of the information contained in a large number of unlabeled samples in the case of a small number of label samples, and achieve rapid convergence higher classification accuracy (the overall accuracy is 90.003% and 93.288%, respectively), which verifies that the method is suitable for classification of sea ice remote sensing.
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