2019 Vol. 41, No. 3
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2019, 41(3): .
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2019, 41(3): .
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2019, 41(3): 1-11.
doi: 10.3969/j.issn.0253-4193.2019.03.001
Abstract:
Diapycnal mixing due to wind-generated near-inertial internal wave breaking plays an important role in the ocean interior mixing. However, the effects of its parameterization on the simulation in oceanic model remain to be studied progressively. In this paper, a diapycnal mixing parameterization due to wind-generated near-inertial wave breaking is implemented to the Modular Ocean Model (MOM) below the ocean surface boundary layer. Simulation results show that the proposed scheme can effectively improve the upper 1 000 m temperature and salinity deviations simulated by MOM4, especially in the ventilation areas of the North Pacific Ocean and the North Atlantic Ocean. Numerical experiments show that the near-inertial wave breaking may be one of the most important mechanisms to maintain the oceanic ventilation processes. It makes temperature colder, salinity fresher and isopyncal layer depth deeper in the ventilation area. The maintenance of ventilation processes extends the impact of the subpolar gyre to the subtropical gyre in the North Pacific. Therefore, the simulated temperature and salinity in the source region of the North Pacific Intermediate Water and the eastern part of the subtropical gyre are closer to the observation. Meanwhile, the simulation of the North Atlantic Ocean overturning circulation intensity is more reasonable.
Diapycnal mixing due to wind-generated near-inertial internal wave breaking plays an important role in the ocean interior mixing. However, the effects of its parameterization on the simulation in oceanic model remain to be studied progressively. In this paper, a diapycnal mixing parameterization due to wind-generated near-inertial wave breaking is implemented to the Modular Ocean Model (MOM) below the ocean surface boundary layer. Simulation results show that the proposed scheme can effectively improve the upper 1 000 m temperature and salinity deviations simulated by MOM4, especially in the ventilation areas of the North Pacific Ocean and the North Atlantic Ocean. Numerical experiments show that the near-inertial wave breaking may be one of the most important mechanisms to maintain the oceanic ventilation processes. It makes temperature colder, salinity fresher and isopyncal layer depth deeper in the ventilation area. The maintenance of ventilation processes extends the impact of the subpolar gyre to the subtropical gyre in the North Pacific. Therefore, the simulated temperature and salinity in the source region of the North Pacific Intermediate Water and the eastern part of the subtropical gyre are closer to the observation. Meanwhile, the simulation of the North Atlantic Ocean overturning circulation intensity is more reasonable.
2019, 41(3): 12-22.
doi: 10.3969/j.issn.0253-4193.2019.03.002
Abstract:
The surface radiation and turbulent fluxes over 82°N drifting ice in the Arctic Ocean in summer were measured from August 7 to August 14 during the Chinese National Arctic Research Expedition in 2016 (CHINARE2016). The results show that the surface albedo of drifting ice range from 0.64 to 0.92 with an average of 0.78. Four different snow/ice albedo parameterizations (PW79, HIRHAM, ARCSYM and CCSM3) which are used in a variety of climate models are evaluated by comparing with the in-situ observations, the most complex CCSM3 scheme agreed best with the observations, but cannot well capture the rapid increasing of albedo which is induced by snowfall. The average sensible heat flux, latent heat flux and net radiation over the snow/ice surface are 1.73 W/m2, 5.55 W/m2 and 18.10 W/m2, respectively. The melting rate of ice surface is (0.30±0.22) cm/d, which shows that the drifting ice is gaining heat and under rapidly melting. The average momentum flux over the ice surface is 0.098 (kg·m/s)/(m2·s). The momentum flux has a good correlation with the wind speed and the correlation coefficient reached 0.80.
The surface radiation and turbulent fluxes over 82°N drifting ice in the Arctic Ocean in summer were measured from August 7 to August 14 during the Chinese National Arctic Research Expedition in 2016 (CHINARE2016). The results show that the surface albedo of drifting ice range from 0.64 to 0.92 with an average of 0.78. Four different snow/ice albedo parameterizations (PW79, HIRHAM, ARCSYM and CCSM3) which are used in a variety of climate models are evaluated by comparing with the in-situ observations, the most complex CCSM3 scheme agreed best with the observations, but cannot well capture the rapid increasing of albedo which is induced by snowfall. The average sensible heat flux, latent heat flux and net radiation over the snow/ice surface are 1.73 W/m2, 5.55 W/m2 and 18.10 W/m2, respectively. The melting rate of ice surface is (0.30±0.22) cm/d, which shows that the drifting ice is gaining heat and under rapidly melting. The average momentum flux over the ice surface is 0.098 (kg·m/s)/(m2·s). The momentum flux has a good correlation with the wind speed and the correlation coefficient reached 0.80.
2019, 41(3): 23-34.
doi: 10.3969/j.issn.0253-4193.2019.03.003
Abstract:
Based on the global merged altimeter wave height database (1991-2016), the characteristics of hazardous waves in the South China Sea (SCS) are investigated. The hazardous waves in the SCS can be classified into typhoon waves and non-typhoon waves in accordance with the inducing weather system. In terms of this classifying standard, a factor termed as typhoon wave weight factor (W) is defined to reveal the quantitative relationship between the typhoon waves and the non-typhoon waves. In accordance with quantitative analysis of the hazardous waves, it is revealed that hazardous waves in different regional oceans are highlighted with different statistical characteristics. Based on the annual extreme waves sampled from the merged altimeter wave data, extreme value analysis is carried out to predict the return period wave height in the SCS. It is proved that there is significant correlation between the W and the types of GEV.
Based on the global merged altimeter wave height database (1991-2016), the characteristics of hazardous waves in the South China Sea (SCS) are investigated. The hazardous waves in the SCS can be classified into typhoon waves and non-typhoon waves in accordance with the inducing weather system. In terms of this classifying standard, a factor termed as typhoon wave weight factor (W) is defined to reveal the quantitative relationship between the typhoon waves and the non-typhoon waves. In accordance with quantitative analysis of the hazardous waves, it is revealed that hazardous waves in different regional oceans are highlighted with different statistical characteristics. Based on the annual extreme waves sampled from the merged altimeter wave data, extreme value analysis is carried out to predict the return period wave height in the SCS. It is proved that there is significant correlation between the W and the types of GEV.
2019, 41(3): 35-43.
doi: 10.3969/j.issn.0253-4193.2019.03.004
Abstract:
The wave directional distribution has a significant effect on the wave propagation and its interaction with offshore structures. Most of the researches are based on unidirectional waves. In order to study the effect of directional distribution on the wave run-up on cylinders, a numerical modeling of multidirectional waves interaction with an array of cylinders was established based on the linear theory of wave interacts on an array of cylinders combined the method to generate multidirectional wave. A wave basin experiment was carried out, and the numerical calculation results were verified by the results of the physical experiment. The wave run-up around cylinders was calculated systematically, the results show that wave directional distribution has significant effects on wave run-up, and the effect is also based on the position around the cylinders. In the engineering design, if the calculation is based on unidirectional wave, it may underestimate or overestimate the wave run-up around the cylinders.
The wave directional distribution has a significant effect on the wave propagation and its interaction with offshore structures. Most of the researches are based on unidirectional waves. In order to study the effect of directional distribution on the wave run-up on cylinders, a numerical modeling of multidirectional waves interaction with an array of cylinders was established based on the linear theory of wave interacts on an array of cylinders combined the method to generate multidirectional wave. A wave basin experiment was carried out, and the numerical calculation results were verified by the results of the physical experiment. The wave run-up around cylinders was calculated systematically, the results show that wave directional distribution has significant effects on wave run-up, and the effect is also based on the position around the cylinders. In the engineering design, if the calculation is based on unidirectional wave, it may underestimate or overestimate the wave run-up around the cylinders.
2019, 41(3): 44-51.
doi: 10.3969/j.issn.0253-4193.2019.03.005
Abstract:
Due to the instability modulation (Benjamin-Feir instability) and nonlinear wave-wave interaction, the distribution of waves deviates from the Rayleigh distribution under the linear hypothesis. Numerical simulation of waves in different initial conditions by using High-Order Spectral model, compares the Rayleigh distributions in the linear theory and the modified Edgewood Rayleigh distribution (MER distribution) and the distribution based on the Gram-Charlier expansion (GC distribution) with wave height data. Results show that in the process of wave propagation skewness changed little and kurtosis increased gradually. Wave distribution is accord with Rayleigh distribution in smaller significant wave height. Wave distribution is accord with MER and GC distribution while significant wave height increased. The wave height distribution is more close to the Rayleigh distribution than the narrow spectrum under the condition of wide spectrum.
Due to the instability modulation (Benjamin-Feir instability) and nonlinear wave-wave interaction, the distribution of waves deviates from the Rayleigh distribution under the linear hypothesis. Numerical simulation of waves in different initial conditions by using High-Order Spectral model, compares the Rayleigh distributions in the linear theory and the modified Edgewood Rayleigh distribution (MER distribution) and the distribution based on the Gram-Charlier expansion (GC distribution) with wave height data. Results show that in the process of wave propagation skewness changed little and kurtosis increased gradually. Wave distribution is accord with Rayleigh distribution in smaller significant wave height. Wave distribution is accord with MER and GC distribution while significant wave height increased. The wave height distribution is more close to the Rayleigh distribution than the narrow spectrum under the condition of wide spectrum.
2019, 41(3): 52-61.
doi: 10.3969/j.issn.0253-4193.2019.03.006
Abstract:
The vertical mixing induced by waves affects the structure of the upper ocean, which dominates the atmosphere-ocean coupling system through air-sea exchanges. Hence waves have an important effect on climate prediction. Based on the First Institute of Oceanography Earth System Model (FIO-ESM), a group of prediction experiments are conducted. One of the experiments is coupled with the wave model and the other is not. The prediction results in 2016 are applied to study the effects of wave-induced mixing on the seasonal prediction of the North Pacific sea surface temperature (SST). Considering the wave-induced mixing, the prediction error is significantly reduced at high latitudes of the North Pacific. The predicted sea surface temperature anomaly (SSTA) can be improved by 1℃ near (45°N, 150°E). The climate model well predicts the meridional distribution of SSTA, especially the distribution characteristics during 25°-45°N. Then, the heat budgets of the two experiments are analyzed to find the reason for this improvement. The result indicates that the vertical mixing is the main influencing factor. The wave-induced mixing causes SST to reduce substantially at high latitudes and to increase slightly at low latitudes in 2016, which plays a key role in SST seasonal prediction in the North Pacific.
The vertical mixing induced by waves affects the structure of the upper ocean, which dominates the atmosphere-ocean coupling system through air-sea exchanges. Hence waves have an important effect on climate prediction. Based on the First Institute of Oceanography Earth System Model (FIO-ESM), a group of prediction experiments are conducted. One of the experiments is coupled with the wave model and the other is not. The prediction results in 2016 are applied to study the effects of wave-induced mixing on the seasonal prediction of the North Pacific sea surface temperature (SST). Considering the wave-induced mixing, the prediction error is significantly reduced at high latitudes of the North Pacific. The predicted sea surface temperature anomaly (SSTA) can be improved by 1℃ near (45°N, 150°E). The climate model well predicts the meridional distribution of SSTA, especially the distribution characteristics during 25°-45°N. Then, the heat budgets of the two experiments are analyzed to find the reason for this improvement. The result indicates that the vertical mixing is the main influencing factor. The wave-induced mixing causes SST to reduce substantially at high latitudes and to increase slightly at low latitudes in 2016, which plays a key role in SST seasonal prediction in the North Pacific.
2019, 41(3): 62-75.
doi: 10.3969/j.issn.0253-4193.2019.03.007
Abstract:
A dramatic increase in the sea reclamation works around the Bohai bay since 2000 has resulted in a change in the tidal field near the engineering area, which influenced both the spatial and temporal distribution of the high temperature concentrated salt water discharged in the sea. A three-dimensional mathematical model based on the different shoreline and topographic conditions in 2000 and 2015 was established to stimulate the high temperature concentrated salt water discharged in the sea by three power plants along the Bohai Bay. The results of stimulations show that great changes have taken place in the characteristics of both the tidal filed and the transport and diffusion of high temperature concentrated water in the Bohai Bay during the last ten years. With the completion of the project, the average salinity of the Bohai Bay increased by 0.203 and the average temperature increased by 0.105℃, in the meanwhile both the transport and diffusion rate of high concentrated salt water in the sea area near the Caofeidian increased significantly. Given the condition the flow of the drain increased to 12.7 m3/s, the highest temperature in the bay reached 26.46℃, which is 2.72℃ higher than that in 2015. This model can accurately simulate and predict the salinity and temperature distribution of the effluent and provide the theoretical basis for the locations of outlets of the power plants.
A dramatic increase in the sea reclamation works around the Bohai bay since 2000 has resulted in a change in the tidal field near the engineering area, which influenced both the spatial and temporal distribution of the high temperature concentrated salt water discharged in the sea. A three-dimensional mathematical model based on the different shoreline and topographic conditions in 2000 and 2015 was established to stimulate the high temperature concentrated salt water discharged in the sea by three power plants along the Bohai Bay. The results of stimulations show that great changes have taken place in the characteristics of both the tidal filed and the transport and diffusion of high temperature concentrated water in the Bohai Bay during the last ten years. With the completion of the project, the average salinity of the Bohai Bay increased by 0.203 and the average temperature increased by 0.105℃, in the meanwhile both the transport and diffusion rate of high concentrated salt water in the sea area near the Caofeidian increased significantly. Given the condition the flow of the drain increased to 12.7 m3/s, the highest temperature in the bay reached 26.46℃, which is 2.72℃ higher than that in 2015. This model can accurately simulate and predict the salinity and temperature distribution of the effluent and provide the theoretical basis for the locations of outlets of the power plants.
2019, 41(3): 76-85.
doi: 10.3969/j.issn.0253-4193.2019.03.008
Abstract:
Under-ice acoustic propagation is studied based on the acoustic propagation experiment data acquired on the Arctic on 6th August 2017. Using Burke-Twersky (BT) model and ray theory, multipath arrival structure of under-ice sound propagation, the phenomenon of rapid attenuation of received sound intensity, and low temporal correlation coefficient are analyzed and explained. The experimental results show that the received signal is consist by small-angle multiple-reversals sound rays, sound rays with one bottom reflection and sound rays with twice bottom reflection. And the intensity of small-angle multiple-reversals sound rays is significantly greater than sound rays with bottom reflection. The movement of experimental ice station causes the rapid attenuation of sound propagation signal's intensity and correlation during the experiment, and the maximum of the intensity attenuation can be as great as 20 dB. The conclusion above is verified by simulation.
Under-ice acoustic propagation is studied based on the acoustic propagation experiment data acquired on the Arctic on 6th August 2017. Using Burke-Twersky (BT) model and ray theory, multipath arrival structure of under-ice sound propagation, the phenomenon of rapid attenuation of received sound intensity, and low temporal correlation coefficient are analyzed and explained. The experimental results show that the received signal is consist by small-angle multiple-reversals sound rays, sound rays with one bottom reflection and sound rays with twice bottom reflection. And the intensity of small-angle multiple-reversals sound rays is significantly greater than sound rays with bottom reflection. The movement of experimental ice station causes the rapid attenuation of sound propagation signal's intensity and correlation during the experiment, and the maximum of the intensity attenuation can be as great as 20 dB. The conclusion above is verified by simulation.
2019, 41(3): 86-95.
doi: 10.3969/j.issn.0253-4193.2019.03.009
Abstract:
Accretion of oceanic crust has experienced the mantle partial melting by decompression, melt extraction, migration and focusing into the oceanic crust, which emplaced in the oceanic crust forming of dike and erupted on the bottom of sea after fractional crystallization. The dramatic variation of crustal thickness along the ultraslow mid-ocean ridge and ammagmatic segmentation is concerned to be the typical characteristics to others. Based on previous studies of melt generation key factors and migration model of mid-ocean ridge basalt, this paper discussed the process of melt at ultraslow mid-ocean ridge and analyzed the key factors controlling the crustal thickness. Besides, this process and its result is constrained by geophysical and geochemical observation. The result shows that the crustal thickness along the ultraslow mid-ocean ridge is constrained by melt volume and lateral migration collectively. Among this process, mantle potential temperature, mantle compositions and spreading velocity controlled the melt volume. The segmentation of ultraslow mid-ocean ridge and the corresponding permeability barrier construct guide the migration and focusing of melt.
Accretion of oceanic crust has experienced the mantle partial melting by decompression, melt extraction, migration and focusing into the oceanic crust, which emplaced in the oceanic crust forming of dike and erupted on the bottom of sea after fractional crystallization. The dramatic variation of crustal thickness along the ultraslow mid-ocean ridge and ammagmatic segmentation is concerned to be the typical characteristics to others. Based on previous studies of melt generation key factors and migration model of mid-ocean ridge basalt, this paper discussed the process of melt at ultraslow mid-ocean ridge and analyzed the key factors controlling the crustal thickness. Besides, this process and its result is constrained by geophysical and geochemical observation. The result shows that the crustal thickness along the ultraslow mid-ocean ridge is constrained by melt volume and lateral migration collectively. Among this process, mantle potential temperature, mantle compositions and spreading velocity controlled the melt volume. The segmentation of ultraslow mid-ocean ridge and the corresponding permeability barrier construct guide the migration and focusing of melt.
2019, 41(3): 96-105.
doi: 10.3969/j.issn.0253-4193.2019.03.010
Abstract:
Tasman Sea lies in the Southwest Pacific, among the Pacific Plate, Indo-Australia Plate, and Antarctica Plate, where geotectonic background is intricate. It is one of the most important waters for global oil and gas resource exploration, but research on the region is rare in domestic. We identify tectonic elements around the Tasman Sea Basin based on the free air gravity anomaly published on the International Gravimetric Bureau. Predecessors' research about the Tasman Sea usually focused on the part north of the Resolution Ridge, but we suggest that the Tasman Sea is supposed to include region south of the Resolution Ridge, west of the Macquarie Ridge and east of the Tasman Fault Zone. This region is transformed by intrusion and spreading of the Southeast Indian Ocean Ridge along boundary between the Southwest Pacific Plate and Indo-Australia Plate (the Macquarie Ridge) since about 50 Ma BP. Results show that three class-ltectonic elements in this region and adjacent area are as follows: Eastern Continental Margin of Australia, Zealandia and Tasman Sea Basin (including Western Sub-Basin, Eastern Sub-Basin, and Southern Sub-Basin). In addition, we make 11 evolution process maps of the Tasman Sea by using global crustal age data supplied by the Professor Dietmar Müller of Sydney University. The process shows that evolution of Tasman sea can be divided into four phases: Mesozoic intra-continental rift phase (90-83 Ma BP); expansion phase of the Tasman Sea (83-61 Ma BP); stop expansion phase of north of the Tasman Sea (61-52 Ma BP), transformation of southern sub-basin (52 Ma BP to present).
Tasman Sea lies in the Southwest Pacific, among the Pacific Plate, Indo-Australia Plate, and Antarctica Plate, where geotectonic background is intricate. It is one of the most important waters for global oil and gas resource exploration, but research on the region is rare in domestic. We identify tectonic elements around the Tasman Sea Basin based on the free air gravity anomaly published on the International Gravimetric Bureau. Predecessors' research about the Tasman Sea usually focused on the part north of the Resolution Ridge, but we suggest that the Tasman Sea is supposed to include region south of the Resolution Ridge, west of the Macquarie Ridge and east of the Tasman Fault Zone. This region is transformed by intrusion and spreading of the Southeast Indian Ocean Ridge along boundary between the Southwest Pacific Plate and Indo-Australia Plate (the Macquarie Ridge) since about 50 Ma BP. Results show that three class-ltectonic elements in this region and adjacent area are as follows: Eastern Continental Margin of Australia, Zealandia and Tasman Sea Basin (including Western Sub-Basin, Eastern Sub-Basin, and Southern Sub-Basin). In addition, we make 11 evolution process maps of the Tasman Sea by using global crustal age data supplied by the Professor Dietmar Müller of Sydney University. The process shows that evolution of Tasman sea can be divided into four phases: Mesozoic intra-continental rift phase (90-83 Ma BP); expansion phase of the Tasman Sea (83-61 Ma BP); stop expansion phase of north of the Tasman Sea (61-52 Ma BP), transformation of southern sub-basin (52 Ma BP to present).
2019, 41(3): 106-120.
doi: 10.3969/j.issn.0253-4193.2019.03.011
Abstract:
This paper systematically identified the submarine pockmarks in the southern depression of the Reed Basin in the South China Sea for the first time, based on high-resolution multi-beam bathymetric data and sub-bottom profiles. A total of 81 pockmarks have been identified, and the maximum diameter of them reaches almost 2.4 km, and the maximum depth is 154 m. The types of pockmarks are various: they can be divided into circular, elliptical, elongated and crescent pockmarks based on plane shape; they also fall into isolated pockmarks, pockmark chains and pockmark complex based on their distribution; and they can be divided into normal pockmarks and mega-pockmarks according to their diameters as well. A number of large-scale submarine canyons have been developed in the study area. Canyon erosion has caused instability of stratigraphy in both sides that accelerates the collapse of gas hydrate. Leaked gas has been ejected from the seabed along faults or gas chimneys to form pockmarks. Meanwhile, the turbidity currents, generated by mixing the eroded sediments during the formation of pockmarks with the surrounding water, to a certain extent, have promoted the downward extension of the submarine canyons. The plane shape of the isolated pockmarks in the study area presents in circular or elliptical, then have evolved into elongated or crescent with the influence of gravity flows and canyon erosion, and finally some of them have been merged with each other to form pockmark complex. The pockmark chains are closely related to the formation of the gully, and the pockmark chains spreading in the direction perpendicular to the contour line, can evolve into pockmark gullies with smooth bottom under the scour of the gravity flows. Comparing with the parameters of pockmarks in other areas of the world, it is found that the size of the pockmarks has a close link to the water depth, and it is easier to develop mega-pockmarks in deep water areas.
This paper systematically identified the submarine pockmarks in the southern depression of the Reed Basin in the South China Sea for the first time, based on high-resolution multi-beam bathymetric data and sub-bottom profiles. A total of 81 pockmarks have been identified, and the maximum diameter of them reaches almost 2.4 km, and the maximum depth is 154 m. The types of pockmarks are various: they can be divided into circular, elliptical, elongated and crescent pockmarks based on plane shape; they also fall into isolated pockmarks, pockmark chains and pockmark complex based on their distribution; and they can be divided into normal pockmarks and mega-pockmarks according to their diameters as well. A number of large-scale submarine canyons have been developed in the study area. Canyon erosion has caused instability of stratigraphy in both sides that accelerates the collapse of gas hydrate. Leaked gas has been ejected from the seabed along faults or gas chimneys to form pockmarks. Meanwhile, the turbidity currents, generated by mixing the eroded sediments during the formation of pockmarks with the surrounding water, to a certain extent, have promoted the downward extension of the submarine canyons. The plane shape of the isolated pockmarks in the study area presents in circular or elliptical, then have evolved into elongated or crescent with the influence of gravity flows and canyon erosion, and finally some of them have been merged with each other to form pockmark complex. The pockmark chains are closely related to the formation of the gully, and the pockmark chains spreading in the direction perpendicular to the contour line, can evolve into pockmark gullies with smooth bottom under the scour of the gravity flows. Comparing with the parameters of pockmarks in other areas of the world, it is found that the size of the pockmarks has a close link to the water depth, and it is easier to develop mega-pockmarks in deep water areas.
2019, 41(3): 121-133.
doi: 10.3969/j.issn.0253-4193.2019.03.012
Abstract:
The Pliocene strata-trapped gas field L18 has been discovered recently in the ultra-deepwater area of the Qiongdongnan Basin.There are considerable debates regarding what the accumulation background is and how the source rock developed and the reservoir deposited and what the gas migration pathway and the gas accumulation model are in the gas field L18. Our integrate study reveals that besides developing strata-trap within axial paleo-groove where the natural gas accumulated Pliocene, the formation conditions of the gas field L18 are required to develop the mature marine source rock in the Oligocene Yacheng Formation and the axial confined gravity flow sandstone reservoirs Pliocene, as well as the fault migration pathway in the Oligocene and Miocene in the eastern Lingshui Sag. Our comprehensive research on accumulation model show that the sandstone reservoirs that deposited in the axial confined paleo-groove, and their tops fluctuated due to the later depositional migration and the differential compaction, and are sealed by the adjacent abyssal mudstone deposits, formed the stratigraphic traps of the Pliocene Yinggehai Formation.The mature natural gas has been generated from the marine source rock in the Oligocene Yacheng Formation in the eastern Linshui Sag since 3.4 Ma BP, migrated upward to the sandstone reservoirs in the Yinggehai Formation, then moved laterally into the strata-trapped area and accumulated. The source rock, the valid trap and the migration pathway composing of faults and sandstones together contributed to the natural gas accumulation in the gas field L18.
The Pliocene strata-trapped gas field L18 has been discovered recently in the ultra-deepwater area of the Qiongdongnan Basin.There are considerable debates regarding what the accumulation background is and how the source rock developed and the reservoir deposited and what the gas migration pathway and the gas accumulation model are in the gas field L18. Our integrate study reveals that besides developing strata-trap within axial paleo-groove where the natural gas accumulated Pliocene, the formation conditions of the gas field L18 are required to develop the mature marine source rock in the Oligocene Yacheng Formation and the axial confined gravity flow sandstone reservoirs Pliocene, as well as the fault migration pathway in the Oligocene and Miocene in the eastern Lingshui Sag. Our comprehensive research on accumulation model show that the sandstone reservoirs that deposited in the axial confined paleo-groove, and their tops fluctuated due to the later depositional migration and the differential compaction, and are sealed by the adjacent abyssal mudstone deposits, formed the stratigraphic traps of the Pliocene Yinggehai Formation.The mature natural gas has been generated from the marine source rock in the Oligocene Yacheng Formation in the eastern Linshui Sag since 3.4 Ma BP, migrated upward to the sandstone reservoirs in the Yinggehai Formation, then moved laterally into the strata-trapped area and accumulated. The source rock, the valid trap and the migration pathway composing of faults and sandstones together contributed to the natural gas accumulation in the gas field L18.
2019, 41(3): 134-142.
doi: 10.3969/j.issn.0253-4193.2019.03.013
Abstract:
The South Yellow Sea has been one of the important sinks for the terrigenous sediments transported by the Changjiang and Yellow rivers. It contains abundant information for the river migration and evolution in the sedimentary records. The Xiyang tidal channel, as one of the important tidal channels in the northwestern radial sand ridge field, is located on the central Jiangsu coast of the South Yellow Sea. It has the strong impacts from both the ancient Yellow River and Changjiang River in this area. So far, the studies on the paleo-geomorphology and sedimentary strata are still not sufficient. Based on the about 380 km long shallow seismic profiles obtained in the study area, combined with the published data of sedimentary core, the shallow seismic sequence has been studied, and concerned characteristics of the sedimentary environments have been discussed. The results indicate that there is a regional unconformable seismic reflection interface underneath the seafloor, 33-49 m below the mean sea-level, characterized by strong amplitude, medium frequency and good continuity. This strong reflection interface could correspond to the top surface of coastal lacustrine deposits in the core. It is the representative for a paleo-geomorphological surface. The spatial distribution of this strong reflection interface, joint with the groove seismic structures underneath it, figure out that several ancient channels extending to the sea northeastwards and converging in the lower-lying area located in the north of the study area. The strong reflection interface is an eroded surface formed during the last deglaciation transgression. Its overlying is the shallow water deposits formed during the Holocene, on the other hand, its underlying is the deposits in flood plain or coastal marsh or ancient river or tidal channels formed during the last stage of the late Pleistocene. The further study of this regional interface is helpful to understand the evolution of the sedimentary systems in the western South Yellow Sea since the late Pleistocene, and to improve the understanding of the development of the radial sand ridge field.
The South Yellow Sea has been one of the important sinks for the terrigenous sediments transported by the Changjiang and Yellow rivers. It contains abundant information for the river migration and evolution in the sedimentary records. The Xiyang tidal channel, as one of the important tidal channels in the northwestern radial sand ridge field, is located on the central Jiangsu coast of the South Yellow Sea. It has the strong impacts from both the ancient Yellow River and Changjiang River in this area. So far, the studies on the paleo-geomorphology and sedimentary strata are still not sufficient. Based on the about 380 km long shallow seismic profiles obtained in the study area, combined with the published data of sedimentary core, the shallow seismic sequence has been studied, and concerned characteristics of the sedimentary environments have been discussed. The results indicate that there is a regional unconformable seismic reflection interface underneath the seafloor, 33-49 m below the mean sea-level, characterized by strong amplitude, medium frequency and good continuity. This strong reflection interface could correspond to the top surface of coastal lacustrine deposits in the core. It is the representative for a paleo-geomorphological surface. The spatial distribution of this strong reflection interface, joint with the groove seismic structures underneath it, figure out that several ancient channels extending to the sea northeastwards and converging in the lower-lying area located in the north of the study area. The strong reflection interface is an eroded surface formed during the last deglaciation transgression. Its overlying is the shallow water deposits formed during the Holocene, on the other hand, its underlying is the deposits in flood plain or coastal marsh or ancient river or tidal channels formed during the last stage of the late Pleistocene. The further study of this regional interface is helpful to understand the evolution of the sedimentary systems in the western South Yellow Sea since the late Pleistocene, and to improve the understanding of the development of the radial sand ridge field.
2019, 41(3): 143-154.
doi: 10.3969/j.issn.0253-4193.2019.03.014
Abstract:
Compared with the traditional microwave radiometer, one dimensional synthetic aperture microwave radiometer can effectively improve the spatial resolution of sea surface temperature retrieval. However, the spaceborne one dimensional synthetic aperture microwave radiometer is multiple incidence angle observation for the sea target and the incidence angle changes from 0° to 55°. In order to develop sea surface temperature inversion algorithms suited to one dimensional synthetic aperture microwave radiometer, it is necessary to evaluate the sensitivities of brightness temperature to oceanic and atmospheric environmental elements. Using the sea surface emissivity model and the atmospheric radiative transfer model, we construct a oceanic and atmospheric radiative transfer mode suited to the one dimensional synthetic aperture microwave radiometer. In this paper, the sensitivity changes of C-band vertical and horizontal polarization brightness temperature to oceanic and atmospheric environmental elements at different incidence angles are studied, and the corresponding sensitivity coefficients are calculated. The results indicate that the sensitivities of vertical and horizontal polarization brightness temperature to oceanic and atmospheric environmental elements show different characteristics. With the increase of the incidence angle, the sensitivity of the vertical polarization brightness temperature to the sea surface temperature is enhanced, and the sensitivity to the sea surface wind field is relatively weakened; but the horizontal polarization brightness temperature is opposite. The vertical and horizontal polarization brightness temperature errors caused by the errors of atmospheric water vapor content and cloud liquid water content increase with the increasing of the incidence angle, however, even at a large incidence angle of 55°, the errors of vertical and horizontal polarization brightness temperature are still less than 0.12 K. If the accuracy of sea surface temperature inversion is higher than 1 K, the calibration precision of one dimensional synthetic aperture microwave radiometer should be better than 0.6 K. Overall, the results of this paper are of great significance to the research of sea surface temperature retrieval with multiple incidence angle for one dimensional synthetic aperture microwave radiometer.
Compared with the traditional microwave radiometer, one dimensional synthetic aperture microwave radiometer can effectively improve the spatial resolution of sea surface temperature retrieval. However, the spaceborne one dimensional synthetic aperture microwave radiometer is multiple incidence angle observation for the sea target and the incidence angle changes from 0° to 55°. In order to develop sea surface temperature inversion algorithms suited to one dimensional synthetic aperture microwave radiometer, it is necessary to evaluate the sensitivities of brightness temperature to oceanic and atmospheric environmental elements. Using the sea surface emissivity model and the atmospheric radiative transfer model, we construct a oceanic and atmospheric radiative transfer mode suited to the one dimensional synthetic aperture microwave radiometer. In this paper, the sensitivity changes of C-band vertical and horizontal polarization brightness temperature to oceanic and atmospheric environmental elements at different incidence angles are studied, and the corresponding sensitivity coefficients are calculated. The results indicate that the sensitivities of vertical and horizontal polarization brightness temperature to oceanic and atmospheric environmental elements show different characteristics. With the increase of the incidence angle, the sensitivity of the vertical polarization brightness temperature to the sea surface temperature is enhanced, and the sensitivity to the sea surface wind field is relatively weakened; but the horizontal polarization brightness temperature is opposite. The vertical and horizontal polarization brightness temperature errors caused by the errors of atmospheric water vapor content and cloud liquid water content increase with the increasing of the incidence angle, however, even at a large incidence angle of 55°, the errors of vertical and horizontal polarization brightness temperature are still less than 0.12 K. If the accuracy of sea surface temperature inversion is higher than 1 K, the calibration precision of one dimensional synthetic aperture microwave radiometer should be better than 0.6 K. Overall, the results of this paper are of great significance to the research of sea surface temperature retrieval with multiple incidence angle for one dimensional synthetic aperture microwave radiometer.
2019, 41(3): 155-168.
doi: 10.3969/j.issn.0253-4193.2019.03.015
Abstract:
In order to explore the possibilities of ocean geophysical parameter retrievals with bistatic scattering signals, thorough understanding of ocean bistatic scattering, both its spatial feature and sensitivity to geophysical parameters, will be crucial and meaningful. In this study, the integral equation model (IEM) combined with an improved directional sea spectrum are adopted to simulate the fully polarimetric microwave bistatic scattering from an anisotropic ocean surface. By comparing the simulation results with satellite observations, the geophysical model function CMOD5 and the simulations of Small Slope Approximation (SSA), the practicability of proposed method in simulating ocean surface microwave scattering is validated. Furthermore, the sensitivities of sea surface bistatic scattering to several geometric and physical parameters, i.e., microwave frequency, incidence, polarization, wind speed and direction, are investigated with this method. The simulation results indicate that ocean surface bistatic scatterings show different spatial scattering characteristics under different observation geometry, and have various sensitivities to ocean dynamic parameters, namely, wind speed and wind direction. Specifically, L-band bistatic scatterings in the backward directions are more sensitive to sea surface wind speed, and the co-polarized ones have opposite responses to wind direction changes for low and high wind speed. At low wind speeds, L-band ocean surface bistatic scatterings have higher sensitivities to wind direction. It is also found that the bistatic scattering contains more spatial information than the conventional monostatic scattering. This work expands the understanding of ocean surface scattering in fully bistatic configuration and explore the potential of parameter retrieval with bistatic radar observations.
In order to explore the possibilities of ocean geophysical parameter retrievals with bistatic scattering signals, thorough understanding of ocean bistatic scattering, both its spatial feature and sensitivity to geophysical parameters, will be crucial and meaningful. In this study, the integral equation model (IEM) combined with an improved directional sea spectrum are adopted to simulate the fully polarimetric microwave bistatic scattering from an anisotropic ocean surface. By comparing the simulation results with satellite observations, the geophysical model function CMOD5 and the simulations of Small Slope Approximation (SSA), the practicability of proposed method in simulating ocean surface microwave scattering is validated. Furthermore, the sensitivities of sea surface bistatic scattering to several geometric and physical parameters, i.e., microwave frequency, incidence, polarization, wind speed and direction, are investigated with this method. The simulation results indicate that ocean surface bistatic scatterings show different spatial scattering characteristics under different observation geometry, and have various sensitivities to ocean dynamic parameters, namely, wind speed and wind direction. Specifically, L-band bistatic scatterings in the backward directions are more sensitive to sea surface wind speed, and the co-polarized ones have opposite responses to wind direction changes for low and high wind speed. At low wind speeds, L-band ocean surface bistatic scatterings have higher sensitivities to wind direction. It is also found that the bistatic scattering contains more spatial information than the conventional monostatic scattering. This work expands the understanding of ocean surface scattering in fully bistatic configuration and explore the potential of parameter retrieval with bistatic radar observations.
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