2017 Vol. 39, No. 12
Display Method:
2017, 39(12): .
Abstract:
2017, 39(12): 1-11.
doi: 10.3969/j.issn.0253-4193.2017.12.001
Abstract:
There are significant physical and chemical differences between deep-sea hydrothermal fluids and ambient seawater. Detecting the temperature and turbidity anomaly is one of the main methods to explore the hydrothermal fields. Based on the towed CTD dataset of the project of Submarine Ring of Fire 2002, the hydrological characteristics and flux discharge of hydrothermal vents in Explorer Ridge were analyzed. The neutral buoyancy layer in Explorer Ridge hydrothermal filed is 1 600 to 1 900 m, about 200 m above the seafloor. The maximums of temperature, salinity and turbidity anomaly are 0.04℃, 0.004 and 0.18 NTU, respectively. The shape of the neutral buoyancy layer is approximately elliptical, the major axis overlaps with the ocean ridge, and the total area is about 27 km2. It is found that the neutral buoyancy layer is distinctly layered. It is estimated with empirical formulas that the total buoyancy flux, volume flux and heat flux of the measured hydrothermal vents are 6.19×10-2 m4/s3, 9.884×10-2 m3/s and 194.9 MW, respectively, and their average values are 2.063×10-2 m4/s3, 3.295×10-2 m3/s and 64.967 MW, respectively.
There are significant physical and chemical differences between deep-sea hydrothermal fluids and ambient seawater. Detecting the temperature and turbidity anomaly is one of the main methods to explore the hydrothermal fields. Based on the towed CTD dataset of the project of Submarine Ring of Fire 2002, the hydrological characteristics and flux discharge of hydrothermal vents in Explorer Ridge were analyzed. The neutral buoyancy layer in Explorer Ridge hydrothermal filed is 1 600 to 1 900 m, about 200 m above the seafloor. The maximums of temperature, salinity and turbidity anomaly are 0.04℃, 0.004 and 0.18 NTU, respectively. The shape of the neutral buoyancy layer is approximately elliptical, the major axis overlaps with the ocean ridge, and the total area is about 27 km2. It is found that the neutral buoyancy layer is distinctly layered. It is estimated with empirical formulas that the total buoyancy flux, volume flux and heat flux of the measured hydrothermal vents are 6.19×10-2 m4/s3, 9.884×10-2 m3/s and 194.9 MW, respectively, and their average values are 2.063×10-2 m4/s3, 3.295×10-2 m3/s and 64.967 MW, respectively.
An experimental study on characteristics of turbulence generated by oscillating grids in a wave tank
2017, 39(12): 12-19.
doi: 10.3969/j.issn.0253-4193.2017.12.002
Abstract:
In this paper, we study the characteristics of turbulence generated by oscillating grids in a wave tank. Four experiments are carried out. High-frequency velocity fluctuations with different depths of measurement points, vibration frequency, vibration stroke were recorded by an acoustic Doppler velocimeter (ADV). The experiments results show that, the turbulence strength becomes weak with increasing the distance from measurement points to grid position, becomes strong with increasing vibration frequency and vibration stoke respectively as power function. At the meantime, the turbulence strength of two different grids was compared. From the results we know that the length of grid has great influence on turbulence strength, this is different from the turbulence characteristic in a water box.
In this paper, we study the characteristics of turbulence generated by oscillating grids in a wave tank. Four experiments are carried out. High-frequency velocity fluctuations with different depths of measurement points, vibration frequency, vibration stroke were recorded by an acoustic Doppler velocimeter (ADV). The experiments results show that, the turbulence strength becomes weak with increasing the distance from measurement points to grid position, becomes strong with increasing vibration frequency and vibration stoke respectively as power function. At the meantime, the turbulence strength of two different grids was compared. From the results we know that the length of grid has great influence on turbulence strength, this is different from the turbulence characteristic in a water box.
2017, 39(12): 20-31.
doi: 10.3969/j.issn.0253-4193.2017.12.003
Abstract:
With the survey and remote sensing data, we revealed the seasonal characteristics of the thermocline in the sea area around Nansha Islands sea area in 2013. Specifically, the mean value of the thermocline upper-bounds depth was almost the same in spring, summer and winter, which was around 45 to 47 m, and it was maximum in autumn which was as deep as 60 m. For the thermocline thickness, in the seasons of summer, autumn and winter it demonstrated almost the same mean value ranging from 85 to 87 m, while a slightly smaller value of 78 m was found in spring. The mean value of the thermocline intensity was almost the same throughout the year from spring to winter, which ranged from 0.13 to 0.15℃/m. The formation mechanism of such seasonal characteristics of thermocline upper-bounds depth was also revealed. In spring, it was deep in the west whereas shallow in the east. This is because that the western area was controlled by relatively low net heat fluxes, high wind speeds and the negative wind stress curl, and it is also influenced simultaneously by the mesoscale warm eddy and the anticyclonic circulation from the coastal area off the eastern Indo-China Peninsula; contrarily, the eastern area was controlled by relatively high net heat fluxes, low wind speed as well as the Ekman pumping effect induced by the wind stress curl. In summer, the depth was almost uniform from west to east. It was because that, in the north of 10°N, the wind-induced vortex mixing, though being strong, was undermined by the Ekman pumping, whereas in the south of 10°N the wind-induced vortex mixing, which although was weak, was affected by the negative wind stress curl. In autumn, the mean depth was 15 m deeper than those in the other three seasons. The reason was that the sea area of Nansha Islands was controlled by a warm eddy which induced the anticyclonic circulation that subsequently deepened the thermocline upper-bounds depth through the convergence of upper layer seawater. When it came to winter, the Ekman pumping induced by the positive wind stress curl and the cyclconic circulation caused by the cold eddy worked together, which lifted up the mean value of the thermocline upper-bounds depth by 15 m compared with that in autumn.
With the survey and remote sensing data, we revealed the seasonal characteristics of the thermocline in the sea area around Nansha Islands sea area in 2013. Specifically, the mean value of the thermocline upper-bounds depth was almost the same in spring, summer and winter, which was around 45 to 47 m, and it was maximum in autumn which was as deep as 60 m. For the thermocline thickness, in the seasons of summer, autumn and winter it demonstrated almost the same mean value ranging from 85 to 87 m, while a slightly smaller value of 78 m was found in spring. The mean value of the thermocline intensity was almost the same throughout the year from spring to winter, which ranged from 0.13 to 0.15℃/m. The formation mechanism of such seasonal characteristics of thermocline upper-bounds depth was also revealed. In spring, it was deep in the west whereas shallow in the east. This is because that the western area was controlled by relatively low net heat fluxes, high wind speeds and the negative wind stress curl, and it is also influenced simultaneously by the mesoscale warm eddy and the anticyclonic circulation from the coastal area off the eastern Indo-China Peninsula; contrarily, the eastern area was controlled by relatively high net heat fluxes, low wind speed as well as the Ekman pumping effect induced by the wind stress curl. In summer, the depth was almost uniform from west to east. It was because that, in the north of 10°N, the wind-induced vortex mixing, though being strong, was undermined by the Ekman pumping, whereas in the south of 10°N the wind-induced vortex mixing, which although was weak, was affected by the negative wind stress curl. In autumn, the mean depth was 15 m deeper than those in the other three seasons. The reason was that the sea area of Nansha Islands was controlled by a warm eddy which induced the anticyclonic circulation that subsequently deepened the thermocline upper-bounds depth through the convergence of upper layer seawater. When it came to winter, the Ekman pumping induced by the positive wind stress curl and the cyclconic circulation caused by the cold eddy worked together, which lifted up the mean value of the thermocline upper-bounds depth by 15 m compared with that in autumn.
2017, 39(12): 32-41.
doi: 10.3969/j.issn.0253-4193.2017.12.004
Abstract:
Historical sea temperature and typhoon track datasets are used to study the SST variations of the Yellow Sea and East China Sea influenced by ENSO in the July. The results show that SST anomalies of the Yellow Sea and the East China Sea correlate well with the Niño3 index, the correlation coefficient between the OISST dataset and Niño3 index is -0.32 in July, while it's -0.45 when we use the GODAS dataset. There are more than 60% probability that SST anomalies would below -0.5℃ of the Yellow Sea and the East China Sea in July in the El Niño years. While in La Niña years, most part of the Yellow Sea has almost 60% probability the SST anomalies would surpass 0.5℃ in July. Spatial distributions of SST anomalies in normal years are opposite to that in El Niño years in July, but with low magnitudes. The atmospheric circulation anomalies on the China adjacent seas could bring more precipitation to local area in the July of El Niño years. Meanwhile, the typhoon intensities tend to be stronger, the duration time tends to be longer and the typhoon tracks tend to pass the Yellow Sea and East China Sea in July in the El Niño years. Large-scale precipitation and the typhoon activities are the reasons that result in the negative SSTA of the Yellow Sea and East China Sea. Therefore, based on the El Niño/La Niña background analysis, the effect of large-scale precipitation and typhoon activities should also be taken into consideration when we analyze and forecast the SST anomalies of China adjacent seas in July. This proves us a new mind to analyze the SST anomalies of China adjacent seas by considering different factors with different time-scales under certain background.
Historical sea temperature and typhoon track datasets are used to study the SST variations of the Yellow Sea and East China Sea influenced by ENSO in the July. The results show that SST anomalies of the Yellow Sea and the East China Sea correlate well with the Niño3 index, the correlation coefficient between the OISST dataset and Niño3 index is -0.32 in July, while it's -0.45 when we use the GODAS dataset. There are more than 60% probability that SST anomalies would below -0.5℃ of the Yellow Sea and the East China Sea in July in the El Niño years. While in La Niña years, most part of the Yellow Sea has almost 60% probability the SST anomalies would surpass 0.5℃ in July. Spatial distributions of SST anomalies in normal years are opposite to that in El Niño years in July, but with low magnitudes. The atmospheric circulation anomalies on the China adjacent seas could bring more precipitation to local area in the July of El Niño years. Meanwhile, the typhoon intensities tend to be stronger, the duration time tends to be longer and the typhoon tracks tend to pass the Yellow Sea and East China Sea in July in the El Niño years. Large-scale precipitation and the typhoon activities are the reasons that result in the negative SSTA of the Yellow Sea and East China Sea. Therefore, based on the El Niño/La Niña background analysis, the effect of large-scale precipitation and typhoon activities should also be taken into consideration when we analyze and forecast the SST anomalies of China adjacent seas in July. This proves us a new mind to analyze the SST anomalies of China adjacent seas by considering different factors with different time-scales under certain background.
2017, 39(12): 42-52.
doi: 10.3969/j.issn.0253-4193.2017.12.005
Abstract:
Bransfield Strait and its surrounding areas are the most active neotectonics region of volcanoes and earthquakes, which constitute the only existing "trench-arc-basin" system together with the South Shetland Trench and South Shetland Islands. Based on the observed data from the 28th, 30th Antarctic expeditions and the international public data, this study takes use of the isostatic correction method to invert the Moho depth and its distribution characteristics. The gravity field anormaly of the deep tectonic was analyzed. The free-air gravity anomaly shows a strip-like distribution, orienting closely to the terrain. The Bouguer gravity anomaly in the strait rises up from both of the two sides to the middle. Two high-value-anomaly traps appear in the central trough and the seamounts in the eastern trough respectively, with the highest value up to 150×10-5 m/s2. The minimum value of Moho depth (12 km) appears in the back-arc spreading area. The depth gradually increases from the back-arc spreading area to the both sides (e.g., Bransfield Strait and Antarctic Peninsula), and reaches 24 km at the slope area.
Bransfield Strait and its surrounding areas are the most active neotectonics region of volcanoes and earthquakes, which constitute the only existing "trench-arc-basin" system together with the South Shetland Trench and South Shetland Islands. Based on the observed data from the 28th, 30th Antarctic expeditions and the international public data, this study takes use of the isostatic correction method to invert the Moho depth and its distribution characteristics. The gravity field anormaly of the deep tectonic was analyzed. The free-air gravity anomaly shows a strip-like distribution, orienting closely to the terrain. The Bouguer gravity anomaly in the strait rises up from both of the two sides to the middle. Two high-value-anomaly traps appear in the central trough and the seamounts in the eastern trough respectively, with the highest value up to 150×10-5 m/s2. The minimum value of Moho depth (12 km) appears in the back-arc spreading area. The depth gradually increases from the back-arc spreading area to the both sides (e.g., Bransfield Strait and Antarctic Peninsula), and reaches 24 km at the slope area.
2017, 39(12): 53-62.
doi: 10.3969/j.issn.0253-4193.2017.12.006
Abstract:
Nowadays, a lot of mounded seismic reflections in the Mid-Miocene Meishan Formation were found and attracted the attention of geologists, while the genesises of the mound were various. Combined with the 3D high resolution seismic data and the 2D seismic datum and drilling, this paper aimed at analyzing the characteristics of the mounds. The results show that compared with the weak amplitude channel filled with mudstone in northeast 3D area and the high amplitude channel filled with sandstone in southwest 3D area, the elongated mounds with nearly EW orientaion had mediate amplitude. The channel located between mounds. Wave impedance inversion unravelled that the mounds with inner lower impedance should belong to the scope of mudstone. The inner mound bed with ductile within Meishan Formation were subjected to gravitational spreading, which contributed to developed polygonal faults on the overlying strata with brittle property. Under this circumstance, Meishan Formation was concluded to form in deepwater depositional environment in Mid-Miocene and mounds on the top of Meishan Formation consisted of mudstone. Mounds and channels formed the sag-crest bedform corresponded with channels and mounds above the overlying strata, respectively, which was regarded as the result of bottom current of incision and deposition. This study about the Mid-Miocene mound reflections has guiding significance and can improve the success rate of oil and gas exploration drilling and can reduce oil and gas exploration risk.
Nowadays, a lot of mounded seismic reflections in the Mid-Miocene Meishan Formation were found and attracted the attention of geologists, while the genesises of the mound were various. Combined with the 3D high resolution seismic data and the 2D seismic datum and drilling, this paper aimed at analyzing the characteristics of the mounds. The results show that compared with the weak amplitude channel filled with mudstone in northeast 3D area and the high amplitude channel filled with sandstone in southwest 3D area, the elongated mounds with nearly EW orientaion had mediate amplitude. The channel located between mounds. Wave impedance inversion unravelled that the mounds with inner lower impedance should belong to the scope of mudstone. The inner mound bed with ductile within Meishan Formation were subjected to gravitational spreading, which contributed to developed polygonal faults on the overlying strata with brittle property. Under this circumstance, Meishan Formation was concluded to form in deepwater depositional environment in Mid-Miocene and mounds on the top of Meishan Formation consisted of mudstone. Mounds and channels formed the sag-crest bedform corresponded with channels and mounds above the overlying strata, respectively, which was regarded as the result of bottom current of incision and deposition. This study about the Mid-Miocene mound reflections has guiding significance and can improve the success rate of oil and gas exploration drilling and can reduce oil and gas exploration risk.
2017, 39(12): 63-73.
doi: 10.3969/j.issn.0253-4193.2017.12.007
Abstract:
Research on reservoir flow units in complex faulted block in offshore oilfield has very important practical significance for the studies of reservoir connectivity degree and remaining oil distribution. Taking A1/A5 faulted block of A oilfield in Beibu Gulf as an example, firstly the fine geological framework of flow unit was established through identification of the single sand body in the compound sand bodies. Then the flow unit was divided through impermeable shields formed by fault sealing, interlayers/interlining distribution and the contact relationship of sand body. We conducted parameter optimization through component analysis and correlation analysis and determined porosity, shale content and seepage coefficient as the main parameters for flow unit classification in the study area. Through neural network clustering analysis the flow unit was divided into three types. Based on the study of flow unit in single well, profile, and plane distribution, three-dimensional geological model of flow unit was established by making use of Truncated Gaussian Simulation method. The results show that type Ⅰ has the best reservoir seepage ability and provides a high cumulative production, however its distribution is limited to a potato shape in the central part of underwater distributary channels. Type Ⅱ distribution is most widely distributed in the underwater distributary channels microfacies with preferably reservoir seepage ability and much remaining oil distribution and its productive potential can be improved through adjustment and exploitation. Type Ⅲ has a banded distribution mainly in the underwater bank sand deposition area with wrost reservoir seepage capacity, low production and poor development potential.
Research on reservoir flow units in complex faulted block in offshore oilfield has very important practical significance for the studies of reservoir connectivity degree and remaining oil distribution. Taking A1/A5 faulted block of A oilfield in Beibu Gulf as an example, firstly the fine geological framework of flow unit was established through identification of the single sand body in the compound sand bodies. Then the flow unit was divided through impermeable shields formed by fault sealing, interlayers/interlining distribution and the contact relationship of sand body. We conducted parameter optimization through component analysis and correlation analysis and determined porosity, shale content and seepage coefficient as the main parameters for flow unit classification in the study area. Through neural network clustering analysis the flow unit was divided into three types. Based on the study of flow unit in single well, profile, and plane distribution, three-dimensional geological model of flow unit was established by making use of Truncated Gaussian Simulation method. The results show that type Ⅰ has the best reservoir seepage ability and provides a high cumulative production, however its distribution is limited to a potato shape in the central part of underwater distributary channels. Type Ⅱ distribution is most widely distributed in the underwater distributary channels microfacies with preferably reservoir seepage ability and much remaining oil distribution and its productive potential can be improved through adjustment and exploitation. Type Ⅲ has a banded distribution mainly in the underwater bank sand deposition area with wrost reservoir seepage capacity, low production and poor development potential.
2017, 39(12): 74-89.
doi: 10.3969/j.issn.0253-4193.2017.12.008
Abstract:
In order to reveal the petrogenesis of the rhyolite from the southwestern Okinawa Trough, the major and trace elements of the amphibole phenocrysts in the rhyolite were measured by electron probe and LA-ICP-MS. The composition variation range of major elements of all the amphiboles is small, the crystal chemistry show CaB>1.60, CaA=0, (Na+K)A<0.33, NaB is between 0.23 and 0.39, that belong to calcic series and classify as magnesiohornblendes. Trace elements are characterized by enrichment of Sc, V, Cr, Co, Ni and REE, loss Rb, Sr, Ba, Zr, Th, U and Pb. The enrichment and loss of these elements are related to complex role of isomorphic replacement. Based on the amphibole geothermobarometer, the temperatures and pressures are 775 to 839℃ and 0.12 GPa, roughly equivalent to the depth of 4 km. Genetic mineralogy studies have shown that amphibolite in the rhyolite is a crust-mantle mixing origin, further indicating that the rhyolite was most likely formed by mixing a mantle-derived basaltic magma with a crustal felsic magma, followed by extensive fractional crystallization in the shallow chamber, and crust-mantle mixed source is likely to be the main source of the volcanic rocks from southwest Okinawa Trough.
In order to reveal the petrogenesis of the rhyolite from the southwestern Okinawa Trough, the major and trace elements of the amphibole phenocrysts in the rhyolite were measured by electron probe and LA-ICP-MS. The composition variation range of major elements of all the amphiboles is small, the crystal chemistry show CaB>1.60, CaA=0, (Na+K)A<0.33, NaB is between 0.23 and 0.39, that belong to calcic series and classify as magnesiohornblendes. Trace elements are characterized by enrichment of Sc, V, Cr, Co, Ni and REE, loss Rb, Sr, Ba, Zr, Th, U and Pb. The enrichment and loss of these elements are related to complex role of isomorphic replacement. Based on the amphibole geothermobarometer, the temperatures and pressures are 775 to 839℃ and 0.12 GPa, roughly equivalent to the depth of 4 km. Genetic mineralogy studies have shown that amphibolite in the rhyolite is a crust-mantle mixing origin, further indicating that the rhyolite was most likely formed by mixing a mantle-derived basaltic magma with a crustal felsic magma, followed by extensive fractional crystallization in the shallow chamber, and crust-mantle mixed source is likely to be the main source of the volcanic rocks from southwest Okinawa Trough.
2017, 39(12): 90-97.
doi: 10.3969/j.issn.0253-4193.2017.12.009
Abstract:
Scomber japonicus is a pelagic fish that inhabits the western Pacific Ocean. Understanding the distribution of its fishery and the relationship with marine environmental factors could help us to make reasonable use of the fishery stock. In this study, based on the production data of S.japonicus from July to September, 2003-2011, as well as sea surface temperature (SST), gradient of sea surface temperature (GSST),sea surface height (SSH) and fishing effort to establish the suitability index (SI) through using normal distribution function. This study used different weights to establish habitat suitability index (HSI) through using arithmetic weighted model (AWM), and using production data of July to September in 2012 to verify. The results show that the monthly suitable weights of SST, STG and SSH from July to September is 0.5, 0.25, 0.25; 0.8, 0.1, 0.1, and 0, 1.0, 0. According to the data during July to September in 2012, we found that the main fishing ground is distributed in the waters with HSI greater than 0.6, and the monthly proportion of fishing effort and catch from July to September was 85.87% and 92.55%, 76.74% and 86.69%, 51.83% and 56.11%. It is concluded that in different months different environmental factors have different effects on the distribution of S.japonicus fishery. This study laid the foundation for better predicting the fishing grounds of S.japonicus.
Scomber japonicus is a pelagic fish that inhabits the western Pacific Ocean. Understanding the distribution of its fishery and the relationship with marine environmental factors could help us to make reasonable use of the fishery stock. In this study, based on the production data of S.japonicus from July to September, 2003-2011, as well as sea surface temperature (SST), gradient of sea surface temperature (GSST),sea surface height (SSH) and fishing effort to establish the suitability index (SI) through using normal distribution function. This study used different weights to establish habitat suitability index (HSI) through using arithmetic weighted model (AWM), and using production data of July to September in 2012 to verify. The results show that the monthly suitable weights of SST, STG and SSH from July to September is 0.5, 0.25, 0.25; 0.8, 0.1, 0.1, and 0, 1.0, 0. According to the data during July to September in 2012, we found that the main fishing ground is distributed in the waters with HSI greater than 0.6, and the monthly proportion of fishing effort and catch from July to September was 85.87% and 92.55%, 76.74% and 86.69%, 51.83% and 56.11%. It is concluded that in different months different environmental factors have different effects on the distribution of S.japonicus fishery. This study laid the foundation for better predicting the fishing grounds of S.japonicus.
2017, 39(12): 98-108.
doi: 10.3969/j.issn.0253-4193.2017.12.010
Abstract:
In cold regions, the vibrations of offshore platforms induced by sea ice can be harmful for not only the routine production but also the serviceability and safety of platforms. In this study, a coupled discrete element method (DEM) and finite element method (FEM) is developed to analyze the sea ice-conical jacket platform interaction and ice induced vibrations of the platform. The DEM with bonding-breaking effect between bonded spherical elements is adopted to simulate the breakage of ice cover and the FEM is applied to model the ice-induced vibrations of jacket platform with the beam element. The transmissions of the mechanical variables at the interface between DEM and FEM are achieved in this paper. In additionally, to improve the computational efficiency and scale of the coupled model, the coupled model based on the dynamic sub-structure method is adopted here. In order to verify the effectiveness of the proposed method, ISO19906 and JTS 144-1-2010 standards under various ice velocities and thicknesses are compared with the simulated ice load. The simulated ice load is in good conformance with the standard. Meanwhile, the simulation accelerations obtained by the proposed method are compared with observation data of the four-pile conical platform (JZ20-2 MUQ), which show the high consistency. In addition, the results also indicate that the vibration acceleration of the platform is linearly related to ice velocity, quadratic nonlinearity to ice thickness, and linearly related to the product of the ice velocity and ice thickness squared.
In cold regions, the vibrations of offshore platforms induced by sea ice can be harmful for not only the routine production but also the serviceability and safety of platforms. In this study, a coupled discrete element method (DEM) and finite element method (FEM) is developed to analyze the sea ice-conical jacket platform interaction and ice induced vibrations of the platform. The DEM with bonding-breaking effect between bonded spherical elements is adopted to simulate the breakage of ice cover and the FEM is applied to model the ice-induced vibrations of jacket platform with the beam element. The transmissions of the mechanical variables at the interface between DEM and FEM are achieved in this paper. In additionally, to improve the computational efficiency and scale of the coupled model, the coupled model based on the dynamic sub-structure method is adopted here. In order to verify the effectiveness of the proposed method, ISO19906 and JTS 144-1-2010 standards under various ice velocities and thicknesses are compared with the simulated ice load. The simulated ice load is in good conformance with the standard. Meanwhile, the simulation accelerations obtained by the proposed method are compared with observation data of the four-pile conical platform (JZ20-2 MUQ), which show the high consistency. In addition, the results also indicate that the vibration acceleration of the platform is linearly related to ice velocity, quadratic nonlinearity to ice thickness, and linearly related to the product of the ice velocity and ice thickness squared.
2017, 39(12): 109-121.
doi: 10.3969/j.issn.0253-4193.2017.12.011
Abstract:
For nearly thirty years, the Arctic sea ice coverage shrink sharply, with significant changes in open water too. In this thesis, we used the sea ice concentration products from the National Snow and Ice Center and sea surface temperature data from National Oceanic and Atmospheric Administration to analyze the variability of open water area and the length of the open water season from 1982 to 2016. We further analyzed the sea surface temperature's influence on the spatio-temporal variability of open water. The results indicated that the open water area of the North Pole increased at a rate of 55.89×103 km2/a, sea ice retreat time in advance at a rate of 0.77 days per year on average, sea ice advance time delayed at a rate of 0.82 days per year on average, causing the length of the open water season increased at a rate of 1.59 days per year. In 2016, open water and the length of open water season reached maximum since there were remote sensing observation data, the value were 13.52×106 km2 and 182 days respectively. Nine partitions have different change about the variability of open water, it was found that the seas which affected the open water most were Arctic Ocean core region, Kara and Barents seas. Sea surface temperature has an important influence on the change of open water, its influence extent has a close relationship with the degree of latitude. For high latitude, sea surface temperature's influence for open water was larger than low latitude.
For nearly thirty years, the Arctic sea ice coverage shrink sharply, with significant changes in open water too. In this thesis, we used the sea ice concentration products from the National Snow and Ice Center and sea surface temperature data from National Oceanic and Atmospheric Administration to analyze the variability of open water area and the length of the open water season from 1982 to 2016. We further analyzed the sea surface temperature's influence on the spatio-temporal variability of open water. The results indicated that the open water area of the North Pole increased at a rate of 55.89×103 km2/a, sea ice retreat time in advance at a rate of 0.77 days per year on average, sea ice advance time delayed at a rate of 0.82 days per year on average, causing the length of the open water season increased at a rate of 1.59 days per year. In 2016, open water and the length of open water season reached maximum since there were remote sensing observation data, the value were 13.52×106 km2 and 182 days respectively. Nine partitions have different change about the variability of open water, it was found that the seas which affected the open water most were Arctic Ocean core region, Kara and Barents seas. Sea surface temperature has an important influence on the change of open water, its influence extent has a close relationship with the degree of latitude. For high latitude, sea surface temperature's influence for open water was larger than low latitude.
2017, 39(12): 122-135.
doi: 10.3969/j.issn.0253-4193.2017.12.012
Abstract:
A 3DVAR method with regularization constraints is proposed to blend sea surface wind data in the South China Sea based on the traditional 3DVAR and regularization technology of the inverse problem, and the model function method which is used to determine the reasonable regularization parameters and then the blended experiments of the satellite scatterometer (QuikSCAT) and Guang Zhou Mesoscale Model (GZMM) sea surface wind field data are carried out for a typhoon case. Results show that when we use the regularization method for experiments, the false information caused by the traditional 3DVAR is eliminated obviously and the noise is almost disappeared, at the same time, the wind field and vorticity field as well as divergence field are distributed evenly, and the structure is clear, more importantly, it is clear that the cyclone center is remarkable, and observation is dramatic in the analysis field. Besides, the degrees of freedom for signal (DFS) method is used to evaluate blended systems quantitatively, it is found that the regularized constraint 3DVAR system has a higher DFS and observation influence related to traditional 3DVAR. The blended results are tested based on the independent observation data, it indicates that the result of regularized constraint 3DVAR method has the smallest root mean square error and maximum correlation coefficient, which is better than the statistical result of GZMM and the conventional 3DVAR method.
A 3DVAR method with regularization constraints is proposed to blend sea surface wind data in the South China Sea based on the traditional 3DVAR and regularization technology of the inverse problem, and the model function method which is used to determine the reasonable regularization parameters and then the blended experiments of the satellite scatterometer (QuikSCAT) and Guang Zhou Mesoscale Model (GZMM) sea surface wind field data are carried out for a typhoon case. Results show that when we use the regularization method for experiments, the false information caused by the traditional 3DVAR is eliminated obviously and the noise is almost disappeared, at the same time, the wind field and vorticity field as well as divergence field are distributed evenly, and the structure is clear, more importantly, it is clear that the cyclone center is remarkable, and observation is dramatic in the analysis field. Besides, the degrees of freedom for signal (DFS) method is used to evaluate blended systems quantitatively, it is found that the regularized constraint 3DVAR system has a higher DFS and observation influence related to traditional 3DVAR. The blended results are tested based on the independent observation data, it indicates that the result of regularized constraint 3DVAR method has the smallest root mean square error and maximum correlation coefficient, which is better than the statistical result of GZMM and the conventional 3DVAR method.
Intercomparison analysis of merging sea surface temperature products for the Northwest Pacific Ocean
2017, 39(12): 136-152.
doi: 10.3969/j.issn.0253-4193.2017.12.013
Abstract:
Sea surface temperature products are significant data sources for global ocean atmosphere system studies, and play an important role for research and applications in marine related fields. Focusing on the Northwest Pacific Ocean, three merging SST products (AVHRR OISST, MISST and OSTIA) have been validated and compared with Argo, and intercomparison analysis among merging products during 2007 to 2014 in this paper. The results suggest that the overall trend of the variability changes of the three merging products is consistent in the study area. Bias is ±0.1℃ and root mean square error is less than 0.9℃ between merging products and Argo. Comparisons of merging data and buoy data have obvious seasonal cycles especially, bias and root mean square error are smaller in winter. There are positive deviation in the high latitude area. The data quality of OSTIA is more ideal than other merging products. The differences of data among merging products are relatively large in coastal and high latitude sea area. When sea ice is processed in different ways, merging products will be affected strongly. Before June 2012, the data qualities of SST are much closer between MISST and OSTIA, but henceforth MISST exists system deviation. Infrared data, microwave data and situ data as input data are essential elements in order to produce high temporal-spatial resolution and high precision of merging SST products.
Sea surface temperature products are significant data sources for global ocean atmosphere system studies, and play an important role for research and applications in marine related fields. Focusing on the Northwest Pacific Ocean, three merging SST products (AVHRR OISST, MISST and OSTIA) have been validated and compared with Argo, and intercomparison analysis among merging products during 2007 to 2014 in this paper. The results suggest that the overall trend of the variability changes of the three merging products is consistent in the study area. Bias is ±0.1℃ and root mean square error is less than 0.9℃ between merging products and Argo. Comparisons of merging data and buoy data have obvious seasonal cycles especially, bias and root mean square error are smaller in winter. There are positive deviation in the high latitude area. The data quality of OSTIA is more ideal than other merging products. The differences of data among merging products are relatively large in coastal and high latitude sea area. When sea ice is processed in different ways, merging products will be affected strongly. Before June 2012, the data qualities of SST are much closer between MISST and OSTIA, but henceforth MISST exists system deviation. Infrared data, microwave data and situ data as input data are essential elements in order to produce high temporal-spatial resolution and high precision of merging SST products.
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