2023 Vol. 45, No. 10
Display Method:
2023, 45(10): 1-12.
doi: 10.12284/hyxb2023153
Abstract:
The observation and exploration of the seabed urgently requires the appearance of large-scale and long-term observation platforms. The subsea AUV has three main points: a structure that suitable for the mobility in the seabed, an intelligent motion performance that adapts to the complex environment of the seabed, and the underwater acoustic communication and positioning technology that adapts to the seabed. In this paper, the development and evolution of subsea AUV is analyzed, the key technical challenges of underwater AUVs are summarized, and corresponding solutions for underwater AUV hydrodynamic shape optimization technology, intelligent motion control technology, underwater acoustic communication and positioning navigation technology, and underwater connection and charging technology are provided. Finally, a study case of Autonomous Underwater Helicopter is given, to provide a solution for subsea AUV. This paper provides guidance for the development of subsea AUV, as well as ocean observation and exploration technology.
The observation and exploration of the seabed urgently requires the appearance of large-scale and long-term observation platforms. The subsea AUV has three main points: a structure that suitable for the mobility in the seabed, an intelligent motion performance that adapts to the complex environment of the seabed, and the underwater acoustic communication and positioning technology that adapts to the seabed. In this paper, the development and evolution of subsea AUV is analyzed, the key technical challenges of underwater AUVs are summarized, and corresponding solutions for underwater AUV hydrodynamic shape optimization technology, intelligent motion control technology, underwater acoustic communication and positioning navigation technology, and underwater connection and charging technology are provided. Finally, a study case of Autonomous Underwater Helicopter is given, to provide a solution for subsea AUV. This paper provides guidance for the development of subsea AUV, as well as ocean observation and exploration technology.
2023, 45(10): 13-30.
doi: 10.12284/hyxb2023125
Abstract:
Using Tropical Rainfall Measurement Mission 3B42 rainfall data, this study tracks pathways of Tropical Intraseasonal Oscillations (MJO) from a Lagrange perspective, analyses their distribution in the Maritime Continent (100°−120°E) and further discusses its mechanism. Identifying a raining area with above 12 mm in 24 hours precipitation as a MJO convective region and using its centroid as MJO convective center, pathways of MJO are tracked and a set of pathways is given. Because eastward propagating MJO events happen mostly in boreal winter, this study focuses on the distribution of pathways of MJO events in boreal winter. The results show that if measured by precipitation MJO moves through the Maritime Continent mostly near the equator (5°S−5°N), which is different from past research results that MJO detours to the south of the Maritime Continent measured by using outgoing long wave radiation (OLR) as a index. Besides, the conclusion that the precipitation associated with MJO moves through the Maritime Continent mostly near the equator is independent of background climate patterns like ENSO or IOD. The analysis of the mechanism shows that pathways of the precipitation associated with MJO through the Maritime Continent are mostly regulated by strong latent heat flux anomalies and are inconsistent with regions with warm sea surface temperature anomalies, which leads to different pathways of MJO moving through the Maritime Continent from different perspectives of precipitation and OLR.
Using Tropical Rainfall Measurement Mission 3B42 rainfall data, this study tracks pathways of Tropical Intraseasonal Oscillations (MJO) from a Lagrange perspective, analyses their distribution in the Maritime Continent (100°−120°E) and further discusses its mechanism. Identifying a raining area with above 12 mm in 24 hours precipitation as a MJO convective region and using its centroid as MJO convective center, pathways of MJO are tracked and a set of pathways is given. Because eastward propagating MJO events happen mostly in boreal winter, this study focuses on the distribution of pathways of MJO events in boreal winter. The results show that if measured by precipitation MJO moves through the Maritime Continent mostly near the equator (5°S−5°N), which is different from past research results that MJO detours to the south of the Maritime Continent measured by using outgoing long wave radiation (OLR) as a index. Besides, the conclusion that the precipitation associated with MJO moves through the Maritime Continent mostly near the equator is independent of background climate patterns like ENSO or IOD. The analysis of the mechanism shows that pathways of the precipitation associated with MJO through the Maritime Continent are mostly regulated by strong latent heat flux anomalies and are inconsistent with regions with warm sea surface temperature anomalies, which leads to different pathways of MJO moving through the Maritime Continent from different perspectives of precipitation and OLR.
2023, 45(10): 31-41.
doi: 10.12284/hyxb2023129
Abstract:
Rossby normal mode as a solution of the boundary problem is a key part of the dynamics in the South China Sea. With the usage of multiscale window transform, a recently developed decomposition tool for multiscale processes, mesoscale-eddy fields analogous to Rossby normal modes are separated from the satellite observation of the South China Sea. The eddies are dominated by a group with lifetime of 3 months, which belongs to an oscillating mode with period of 6 months and wavelength of 250 km. To explore the external influence on this mode, we apply an information flow-based causality analysis that has been rigorously established from first principles in physics. It is found that both the Kuroshio intrusion and monsoon, believed to be two primary forcings of the South China Sea circulations, are causal to the Rossby normal mode within one period. Specifically, the Kuroshio intrusion mainly affects the 1/2π and 3/2π phases, while the monsoon the 3/4π phase. Further analysis reveals that the transition between penetration and leaping of the Kuroshio at the Luzon Strait is key to the mode development. Under this circumstance, the leaking and looping branches are almost of equal intensity, facilitating the generation of cyclonic and anticyclonic eddies west of the Luzon Strait, and hence the Rossby normal mode. The monsoon over the South China Sea, on the other hand, shows the greatest influence at its mature phases. The Gulf of Thailand is a key region for the monsoon to affect the Rossby normal mode in the South China Sea, indicating that local forcing plays an important role in exciting a global mode.
Rossby normal mode as a solution of the boundary problem is a key part of the dynamics in the South China Sea. With the usage of multiscale window transform, a recently developed decomposition tool for multiscale processes, mesoscale-eddy fields analogous to Rossby normal modes are separated from the satellite observation of the South China Sea. The eddies are dominated by a group with lifetime of 3 months, which belongs to an oscillating mode with period of 6 months and wavelength of 250 km. To explore the external influence on this mode, we apply an information flow-based causality analysis that has been rigorously established from first principles in physics. It is found that both the Kuroshio intrusion and monsoon, believed to be two primary forcings of the South China Sea circulations, are causal to the Rossby normal mode within one period. Specifically, the Kuroshio intrusion mainly affects the 1/2π and 3/2π phases, while the monsoon the 3/4π phase. Further analysis reveals that the transition between penetration and leaping of the Kuroshio at the Luzon Strait is key to the mode development. Under this circumstance, the leaking and looping branches are almost of equal intensity, facilitating the generation of cyclonic and anticyclonic eddies west of the Luzon Strait, and hence the Rossby normal mode. The monsoon over the South China Sea, on the other hand, shows the greatest influence at its mature phases. The Gulf of Thailand is a key region for the monsoon to affect the Rossby normal mode in the South China Sea, indicating that local forcing plays an important role in exciting a global mode.
2023, 45(10): 42-55.
doi: 10.12284/hyxb2023053
Abstract:
Using reanalysis sea surface data and in-situ high-resolution observations in spring, summer 2018, and summer 2019, this study analyzes the 3D structure and seasonal variation of temperature fronts in the shelf sea west of Guangdong. The results show that the sea surface temperature (SST) fronts reach the strongest intensity up to 0.049°C/km in winter, with the largest occurrence probability of 75% and coverage of 66 km. The SST fronts weaken in spring and summer, and almost disappear in autumn. The average offshore distance of the front is 50 km in winter and 23.1 km in summer. The in-situ observations show a strong thermal front in coastal areas shallower than 20 m in both spring and summer. The front gets weaker and closer to the coast in deeper layers and is associated with warm coastal water and cold shelf water. In shelf areas deeper than 20 m, the fronts in the subsurface layer are stronger than in the surface layer and shift shoreward in deeper layers. The correlation coefficient and information flow between the surface wind and frontal parameters reveal that the surface wind stress curl and along-coast wind are the most important factors affecting the surface thermal front. These thermal fronts also have interannual variations, with maximum intensity in La Niña years with negative PDO and minimum intensity in El Niño years with positive PDO.
Using reanalysis sea surface data and in-situ high-resolution observations in spring, summer 2018, and summer 2019, this study analyzes the 3D structure and seasonal variation of temperature fronts in the shelf sea west of Guangdong. The results show that the sea surface temperature (SST) fronts reach the strongest intensity up to 0.049°C/km in winter, with the largest occurrence probability of 75% and coverage of 66 km. The SST fronts weaken in spring and summer, and almost disappear in autumn. The average offshore distance of the front is 50 km in winter and 23.1 km in summer. The in-situ observations show a strong thermal front in coastal areas shallower than 20 m in both spring and summer. The front gets weaker and closer to the coast in deeper layers and is associated with warm coastal water and cold shelf water. In shelf areas deeper than 20 m, the fronts in the subsurface layer are stronger than in the surface layer and shift shoreward in deeper layers. The correlation coefficient and information flow between the surface wind and frontal parameters reveal that the surface wind stress curl and along-coast wind are the most important factors affecting the surface thermal front. These thermal fronts also have interannual variations, with maximum intensity in La Niña years with negative PDO and minimum intensity in El Niño years with positive PDO.
2023, 45(10): 56-69.
doi: 10.12284/hyxb2023123
Abstract:
Grain size, composition of elements and clay minerals, and AMS14C dating of samples of upmost 100 cm in Core CJ09-03 in the Southwest Arabian Sea were analysied, and provenance, the sedimentary evolution and the restricting factors in the study area since 45 ka BP were discussed. The composition of major elements and rare earth elements show that, the sediment in the study area has obvious terrigenous properties Graph of (La/Sm)UCC-(Gd/Yb)UCC and the composition of clay minerals show that the sources of the sediments in the study area are relatively complex, which include the Thar Desert, the Northeast Africa, the Southwest Asia and the Arabian Peninsula. Based on the index of δ15N from literatures, and indexs of chemical weathering index of illite, K/Al, 1−CaCO3(%), the sedimentary evolution of the Southwest Arabian Sea since 45 ka BP can be divided into four stages: the Last Glacial period, the Last Glacial Maximum periond, the Deglaciation period and the Holocene period. The provenance in different stages are different, which is mainly influenced by the sea level changes and the strength of the Indian monsoon.
Grain size, composition of elements and clay minerals, and AMS14C dating of samples of upmost 100 cm in Core CJ09-03 in the Southwest Arabian Sea were analysied, and provenance, the sedimentary evolution and the restricting factors in the study area since 45 ka BP were discussed. The composition of major elements and rare earth elements show that, the sediment in the study area has obvious terrigenous properties Graph of (La/Sm)UCC-(Gd/Yb)UCC and the composition of clay minerals show that the sources of the sediments in the study area are relatively complex, which include the Thar Desert, the Northeast Africa, the Southwest Asia and the Arabian Peninsula. Based on the index of δ15N from literatures, and indexs of chemical weathering index of illite, K/Al, 1−CaCO3(%), the sedimentary evolution of the Southwest Arabian Sea since 45 ka BP can be divided into four stages: the Last Glacial period, the Last Glacial Maximum periond, the Deglaciation period and the Holocene period. The provenance in different stages are different, which is mainly influenced by the sea level changes and the strength of the Indian monsoon.
2023, 45(10): 70-86.
doi: 10.12284/hyxb2023141
Abstract:
The bioturbation structure is an important indicator of the state of the seabed environment and the main basis for the reconstruction of the paleosedimentary environment; moreover, it affects the early diagenesis of sediments and the redistribution of materials, and becomes the interference factor for the interpretation of the 100-year scale sedimentary records. In this article, sediment cores from 21 stations in the Changjiang River Estuary and its adjacent areas were characterized qualitatively and quantitatively by using high-resolution X-ray computed tomography technology, and the main factors affecting the bioturbation structures were analyzed. The result shows that the bioturbation structures in the Changjiang River Estuary and its adjacent areas are relatively developed, which can be divided into four types: biodiffusor structures, conveyor structures, regenerator structures and gallery-diffusor structures. Conveyor structures and gallery-diffusor structures are common. The bioturbation structure is distributed in various forms in the core, including exponential attenuation type, wave attenuation type, uniform distribution type, pulse distribution type and other vertical distribution forms. The depth of disturbance varies, most of which are within 20 cm, but some are more than 40 cm. The bioturbation structures are spatially uneven. The Changjiang River Estuary and the inner shelf are relatively developed, with a disturbance inventory of 0–13 972 mm3, while the northern Jiangsu coast and the middle continental shelf are less, with a disturbance inventory of 351–3 212 mm3. The bioturbation structures from the coast to the outside have a decreasing trend. The development degree of bioturbation structure is mainly restricted by the type of bottom material and sedimentation rate. Clay silt and suitable sedimentation rate (0.52–1.34 cm/a) are conducive to the development and preservation of bioturbation structures.
The bioturbation structure is an important indicator of the state of the seabed environment and the main basis for the reconstruction of the paleosedimentary environment; moreover, it affects the early diagenesis of sediments and the redistribution of materials, and becomes the interference factor for the interpretation of the 100-year scale sedimentary records. In this article, sediment cores from 21 stations in the Changjiang River Estuary and its adjacent areas were characterized qualitatively and quantitatively by using high-resolution X-ray computed tomography technology, and the main factors affecting the bioturbation structures were analyzed. The result shows that the bioturbation structures in the Changjiang River Estuary and its adjacent areas are relatively developed, which can be divided into four types: biodiffusor structures, conveyor structures, regenerator structures and gallery-diffusor structures. Conveyor structures and gallery-diffusor structures are common. The bioturbation structure is distributed in various forms in the core, including exponential attenuation type, wave attenuation type, uniform distribution type, pulse distribution type and other vertical distribution forms. The depth of disturbance varies, most of which are within 20 cm, but some are more than 40 cm. The bioturbation structures are spatially uneven. The Changjiang River Estuary and the inner shelf are relatively developed, with a disturbance inventory of 0–13 972 mm3, while the northern Jiangsu coast and the middle continental shelf are less, with a disturbance inventory of 351–3 212 mm3. The bioturbation structures from the coast to the outside have a decreasing trend. The development degree of bioturbation structure is mainly restricted by the type of bottom material and sedimentation rate. Clay silt and suitable sedimentation rate (0.52–1.34 cm/a) are conducive to the development and preservation of bioturbation structures.
2023, 45(10): 87-104.
doi: 10.12284/hyxb2023135
Abstract:
The shoreline change is the most direct factor in studying landform erosion and deposition. The Huanghe River Delta is the world’s fastest-growing delta, and understanding its coastline changes and evolution trends is crucial to regional ecological environment protection, marine resource development, and infrastructure construction. In this study, we combined modified normalized difference water index (MNDWI) and multi-year water frequency index (MWFI) to analyze water quality in typical years from 1976 to 2021, based on previous research. We visually interpreted 207 remote sensing images to obtain an annual coastline that makes the obtained coastline more scientific and representative. We then analyzed the temporal and spatial evolution and stability characteristics of the coastline through quantitative calculations to explore the Qingshuigou sub-delta coastline of the Yellow River’s evolution mechanism since 1976. Our main findings are as follows: (1) In general, the evolution of Qingshuigou sub-delta coastline shows a trend of rapid sedimentation towards the sea, followed by fluctuations and stability. We can divide it into “rapid development” and “slow development,” with the “dynamic equilibrium” in between, taking 1996 and 2002 as nodes. (2) Over the past 45 years, the stability of the coastline in the study area has continued to increase. The coastline of the section of the coastline and the abandoned estuary section of Qingshuigou is relatively active, and its coastline stability index is generally lower than 0.5. (3) The migration of the sedimentation and erosion center of the land delta corresponds to the estuary location’s change, especially the migration of the sedimentation center, which has a positive relationship in the longitude direction between the change of the estuary position and the position of the estuary, R2 = 0.690 4. (4) The Huanghe River’s sediment reduction into the sea, the relocation of the estuary position, and human activities have a significant impact on the delta coastline’s development and evolution. In the long run, the Huanghe River’s silt into the sea is still continuously reducing, and the future of the delta is still facing the threat of erosion.
The shoreline change is the most direct factor in studying landform erosion and deposition. The Huanghe River Delta is the world’s fastest-growing delta, and understanding its coastline changes and evolution trends is crucial to regional ecological environment protection, marine resource development, and infrastructure construction. In this study, we combined modified normalized difference water index (MNDWI) and multi-year water frequency index (MWFI) to analyze water quality in typical years from 1976 to 2021, based on previous research. We visually interpreted 207 remote sensing images to obtain an annual coastline that makes the obtained coastline more scientific and representative. We then analyzed the temporal and spatial evolution and stability characteristics of the coastline through quantitative calculations to explore the Qingshuigou sub-delta coastline of the Yellow River’s evolution mechanism since 1976. Our main findings are as follows: (1) In general, the evolution of Qingshuigou sub-delta coastline shows a trend of rapid sedimentation towards the sea, followed by fluctuations and stability. We can divide it into “rapid development” and “slow development,” with the “dynamic equilibrium” in between, taking 1996 and 2002 as nodes. (2) Over the past 45 years, the stability of the coastline in the study area has continued to increase. The coastline of the section of the coastline and the abandoned estuary section of Qingshuigou is relatively active, and its coastline stability index is generally lower than 0.5. (3) The migration of the sedimentation and erosion center of the land delta corresponds to the estuary location’s change, especially the migration of the sedimentation center, which has a positive relationship in the longitude direction between the change of the estuary position and the position of the estuary, R2 = 0.690 4. (4) The Huanghe River’s sediment reduction into the sea, the relocation of the estuary position, and human activities have a significant impact on the delta coastline’s development and evolution. In the long run, the Huanghe River’s silt into the sea is still continuously reducing, and the future of the delta is still facing the threat of erosion.
2023, 45(10): 105-113.
doi: 10.12284/hyxb2023091
Abstract:
The phenomenon of seabed liquefaction is widely distributed in the underwater delta of the Huanghe River, which poses a great threat to submarine engineering facilities. The determination of liquefaction depth can provide a reference for offshore engineering construction, which has great theoretical significance and application value. The columnar sediments were obtained by drilling in the liquefaction disturbance area of Chengdao sea area in the north of the Huanghe River Delta, and the profile image scanning, radionuclide and particle size composition testing were carried out to obtain the image stratification characteristics, 210Pb, 137Cs activity and particle size profile, and the deposition rate was calculated on this basis. The results show that the Chengdao sea area was significantly affected by the change of the Huanghe River from the Diaokou channel in 1976, and the sedimentation rate decreased significantly during this period and showed a phased character. During the rapid deposition period, the sand layer produced by frequent liquefaction of surface sediments accumulated continuously, thus forming the dense sand layer. By analyzing 210Pbex and 137Cs activity profiles, the sedimentary records of liquefaction history in the study area were obtained, and the historical liquefaction depth was determined to be at least 5 m, which is similar to previous studies. It is feasible to use the activity of 210Pb and 137Cs as tools to judge the history and depth of sediment liquefaction, which has great development potential.
The phenomenon of seabed liquefaction is widely distributed in the underwater delta of the Huanghe River, which poses a great threat to submarine engineering facilities. The determination of liquefaction depth can provide a reference for offshore engineering construction, which has great theoretical significance and application value. The columnar sediments were obtained by drilling in the liquefaction disturbance area of Chengdao sea area in the north of the Huanghe River Delta, and the profile image scanning, radionuclide and particle size composition testing were carried out to obtain the image stratification characteristics, 210Pb, 137Cs activity and particle size profile, and the deposition rate was calculated on this basis. The results show that the Chengdao sea area was significantly affected by the change of the Huanghe River from the Diaokou channel in 1976, and the sedimentation rate decreased significantly during this period and showed a phased character. During the rapid deposition period, the sand layer produced by frequent liquefaction of surface sediments accumulated continuously, thus forming the dense sand layer. By analyzing 210Pbex and 137Cs activity profiles, the sedimentary records of liquefaction history in the study area were obtained, and the historical liquefaction depth was determined to be at least 5 m, which is similar to previous studies. It is feasible to use the activity of 210Pb and 137Cs as tools to judge the history and depth of sediment liquefaction, which has great development potential.
2023, 45(10): 114-122.
doi: 10.12284/hyxb2023139
Abstract:
fruitless (fru) gene plays an important role in courtship, mating behavior and reproductive development of insectsand crustaceans. Artemia is not only the crucial live food in fish and crustacean larviculture, but also an ideal experimental organism for biological study. In this experiment, the open reading frame (ORF) of fru gene was obtained from the transcriptome of Artemia franciscana and analyzed bioinformatically. qPCR was used to study the expression characteristics of this gene at different stages of gonad development in the Artemia, and its function was explored by RNAi microinjection. Bioinformatics analysis showed that the ORF length of fru gene was 1 215 bp, which contains 404 amino acids, while its molecular weight and isoelectric point were 45.19 kDa and 5.28, and it was an acidic hydrophilic protein with no signal peptide or transmembrane structure; structural domain prediction showed that there are two structural domains of fru, BTB_POZ and HTH. The secondary structure is dominated by α-helix and irregular coil, and the tertiary structure corresponds to it. The qPCR results showed that the expression of fru gene showed a significant increase in late embryos stage, and its expression was significantly higher than that of early oocyte, later oocyte and early embryo stages in the ovary (P < 0.01); while the expression of fru gene also increased in immature stage of the testis, and its expression was significantly higher than that of early, middle and late maturation stages (P < 0.01). After RNA interference, we found that there was a significant decrease in the expression of the fru gene (P < 0.01), and all the offspring produced were cysts. This suggests that the fru gene has an important effect on reproduction and development of A. franciscana, and may be a key factor influencing the reproductive mode of Artemia. Through this study, we obtained important information about the role of fru gene in the reproductive development of Artemia and their related molecular mechanisms, which can help us better understand this important biological process.
fruitless (fru) gene plays an important role in courtship, mating behavior and reproductive development of insectsand crustaceans. Artemia is not only the crucial live food in fish and crustacean larviculture, but also an ideal experimental organism for biological study. In this experiment, the open reading frame (ORF) of fru gene was obtained from the transcriptome of Artemia franciscana and analyzed bioinformatically. qPCR was used to study the expression characteristics of this gene at different stages of gonad development in the Artemia, and its function was explored by RNAi microinjection. Bioinformatics analysis showed that the ORF length of fru gene was 1 215 bp, which contains 404 amino acids, while its molecular weight and isoelectric point were 45.19 kDa and 5.28, and it was an acidic hydrophilic protein with no signal peptide or transmembrane structure; structural domain prediction showed that there are two structural domains of fru, BTB_POZ and HTH. The secondary structure is dominated by α-helix and irregular coil, and the tertiary structure corresponds to it. The qPCR results showed that the expression of fru gene showed a significant increase in late embryos stage, and its expression was significantly higher than that of early oocyte, later oocyte and early embryo stages in the ovary (P < 0.01); while the expression of fru gene also increased in immature stage of the testis, and its expression was significantly higher than that of early, middle and late maturation stages (P < 0.01). After RNA interference, we found that there was a significant decrease in the expression of the fru gene (P < 0.01), and all the offspring produced were cysts. This suggests that the fru gene has an important effect on reproduction and development of A. franciscana, and may be a key factor influencing the reproductive mode of Artemia. Through this study, we obtained important information about the role of fru gene in the reproductive development of Artemia and their related molecular mechanisms, which can help us better understand this important biological process.
2023, 45(10): 123-134.
doi: 10.12284/hyxb2023137
Abstract:
17β-hydroxysteroid dehydrogenases (17β-HSDs) are the oxidoreductases in the last step of sex steroid hormone synthesis process, and play important roles in animal gonadal development and reproductive regulation. In this study, on the basis of the genome data of the razor clam Sinonovacula constricta, 17β-HSD genes were cloned and identified, and their chromosome distributions, phylogenetic relationships and gene expression patterns in different tissues and under different gonadal developmental stages were analyzed. The results showed that 17β-HSD6, 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes of S. constricta were located on four different chromosomes, and the encoded proteins all contained the conserved SDR superfamily domains. The four 17β-HSD proteins were clearly differentiated and clustered into four independent branches in the phylogenetic trees. The results of qRT-PCR showed that 17β-HSD genes were all expressed in testes tissues, and possessed higher expression levels in gonads and hepatopancreas. During the gonadal development of S. constricta, 17β-HSD6 gene was expressed higher in testis and ovary at the spawning stage. The expression levels of 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes showed a trend of increasing first and then decreasing during the development cycle of testis and ovary, which were all expressed higher at the mature stage. At the mature stage, 17β-HSD10 gene was expressed significantly higher in testis than in ovary (p < 0.05) , while the expression levels of 17β-HSD12 and 17β-HSD14 genes were all significantly higher in ovary than in testis (p < 0.05). Therefore, 17β-HSD6 gene might not be involved in regulating gonadal development process, while the expressions of 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes were closely related to the gonadal development, suggesting that they might affect the gonadal development by regulating the synthesis and metabolism of sex steroid hormones in S. constricta. These findings laid theoretical foundations for further study on mechanism of 17β-HSD genes in regulating gonadal development and reproductive endocrine of mollusks.
17β-hydroxysteroid dehydrogenases (17β-HSDs) are the oxidoreductases in the last step of sex steroid hormone synthesis process, and play important roles in animal gonadal development and reproductive regulation. In this study, on the basis of the genome data of the razor clam Sinonovacula constricta, 17β-HSD genes were cloned and identified, and their chromosome distributions, phylogenetic relationships and gene expression patterns in different tissues and under different gonadal developmental stages were analyzed. The results showed that 17β-HSD6, 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes of S. constricta were located on four different chromosomes, and the encoded proteins all contained the conserved SDR superfamily domains. The four 17β-HSD proteins were clearly differentiated and clustered into four independent branches in the phylogenetic trees. The results of qRT-PCR showed that 17β-HSD genes were all expressed in testes tissues, and possessed higher expression levels in gonads and hepatopancreas. During the gonadal development of S. constricta, 17β-HSD6 gene was expressed higher in testis and ovary at the spawning stage. The expression levels of 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes showed a trend of increasing first and then decreasing during the development cycle of testis and ovary, which were all expressed higher at the mature stage. At the mature stage, 17β-HSD10 gene was expressed significantly higher in testis than in ovary (p < 0.05) , while the expression levels of 17β-HSD12 and 17β-HSD14 genes were all significantly higher in ovary than in testis (p < 0.05). Therefore, 17β-HSD6 gene might not be involved in regulating gonadal development process, while the expressions of 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes were closely related to the gonadal development, suggesting that they might affect the gonadal development by regulating the synthesis and metabolism of sex steroid hormones in S. constricta. These findings laid theoretical foundations for further study on mechanism of 17β-HSD genes in regulating gonadal development and reproductive endocrine of mollusks.
2023, 45(10): 135-146.
doi: 10.12284/hyxb2023149
Abstract:
Rip currents are narrow and concentrated seaward-directed flows and play an important role on coastal morphodynamics, mass transport and swimmer safety. As the intersecting wave field caused by wave reflection of coastal structures is not uniform alongshore, the flow characteristics and spatial distribution of rip currents are different from those of uniform intersecting waves on an open coast. The reflection of waves on cross-shore coastal structures will lead to longshore standing waves, and rip currents will occur in the area of standing wave nodes because of the small wave height, which is one of the generation mechanisms for rip currents. In this study, the characteristics of rip current systems near a coastal structure on a barred beach are given by a laboratory experiment. The influence of the longshore variation of wave height on the flow balance of each rip current unit is discussed. The results showed that the existence of structure drives a longshore current away from the structure and causes the water exchange between each rip current unit. The lateral currents between rip current units are found to make contributions to the rip current transport of each rip current unit and the contributions mainly depend on the relative position of the unit to the structure.
Rip currents are narrow and concentrated seaward-directed flows and play an important role on coastal morphodynamics, mass transport and swimmer safety. As the intersecting wave field caused by wave reflection of coastal structures is not uniform alongshore, the flow characteristics and spatial distribution of rip currents are different from those of uniform intersecting waves on an open coast. The reflection of waves on cross-shore coastal structures will lead to longshore standing waves, and rip currents will occur in the area of standing wave nodes because of the small wave height, which is one of the generation mechanisms for rip currents. In this study, the characteristics of rip current systems near a coastal structure on a barred beach are given by a laboratory experiment. The influence of the longshore variation of wave height on the flow balance of each rip current unit is discussed. The results showed that the existence of structure drives a longshore current away from the structure and causes the water exchange between each rip current unit. The lateral currents between rip current units are found to make contributions to the rip current transport of each rip current unit and the contributions mainly depend on the relative position of the unit to the structure.
2023, 45(10): 147-158.
doi: 10.12284/hyxb2023143
Abstract:
Jiaomen outlet is a typical river network bifurcated estuary and an important channel for flood discharge and sediment discharge of the Zhujiang River. The change of diversion ratio in bifurcated Jiaomen outlet is crucial to the geomorphological evolution, flood control and navigation safety of the Zhujiang River Delta. This study designed a series of flume experiments, and selected sensitivity analysis parameter which includes the water depth of bifurcated channel and bifurcated angle to explores the evolution of the flow division ratio of the river network type bifurcated estuary with the above factors. The dimension of the physical model is based on the recent geomorphic morphology of Jiaomen outlet. The result show that, on the basis of the stability of the section feature of the bifurcated channel, the flow division ratio of Fuzhou Channel depicts a good correlation with the flow velocity ratio between Humen and Jiaomen, and is less affected by the absolute flow velocity of the two outlets. Subsequently, the sensitivity experiment result indicate that the flow division ratio is negatively correlated with the water depth of Jiaomen South Channel and positively correlated with the water depth of Fuzhou Channel, and when the bifurcation angle is between 30° and 65°, the flow division ratio is negatively correlated with the bifurcation angle, but when the bifurcation angle is between 65° and 75°, the positive and negative correlation between the flow division ratio and the bifurcation angle changes around the velocity ratio V = 0.7. Then, the sensitivity of the increase or decrease of the flow division ratio to the above each variable can be obtained by quantifying the sensitivity experiment result. The research results can provide reference for artificial regulation project of Jiaomen outlet.
Jiaomen outlet is a typical river network bifurcated estuary and an important channel for flood discharge and sediment discharge of the Zhujiang River. The change of diversion ratio in bifurcated Jiaomen outlet is crucial to the geomorphological evolution, flood control and navigation safety of the Zhujiang River Delta. This study designed a series of flume experiments, and selected sensitivity analysis parameter which includes the water depth of bifurcated channel and bifurcated angle to explores the evolution of the flow division ratio of the river network type bifurcated estuary with the above factors. The dimension of the physical model is based on the recent geomorphic morphology of Jiaomen outlet. The result show that, on the basis of the stability of the section feature of the bifurcated channel, the flow division ratio of Fuzhou Channel depicts a good correlation with the flow velocity ratio between Humen and Jiaomen, and is less affected by the absolute flow velocity of the two outlets. Subsequently, the sensitivity experiment result indicate that the flow division ratio is negatively correlated with the water depth of Jiaomen South Channel and positively correlated with the water depth of Fuzhou Channel, and when the bifurcation angle is between 30° and 65°, the flow division ratio is negatively correlated with the bifurcation angle, but when the bifurcation angle is between 65° and 75°, the positive and negative correlation between the flow division ratio and the bifurcation angle changes around the velocity ratio V = 0.7. Then, the sensitivity of the increase or decrease of the flow division ratio to the above each variable can be obtained by quantifying the sensitivity experiment result. The research results can provide reference for artificial regulation project of Jiaomen outlet.
2023, 45(10): 159-167.
doi: 10.12284/hyxb2023133
Abstract:
Airborne Laser Bathymetry (ALB) as an established surveying procedure is certainly operated in blue-green region (532 nm) for penetrating the water column to collect depth. Alongside geometric information accepted widely, ALB typically record the radiometric properties (backscattering intensity) about sensed targets and assist with accurate strips registration, fine ground (sediment) cover classification, and advanced geometric modelling. However, due to the design limitations of Automatic Gain Control (AGC), there is a delay in gain value adjustment, particularly prominent in island and coastal areas with more high-return and low-return targets such as exposed rocks and water, which throws the issue of intensity compensation abnormality into stark relief. In response to this issue, a local weighted intensity correction method based on bidirectional movement is designed. Firstly, effective intensity is extracted by index sharing and elevation information. Then, the emission angles are used to divide the scan line and serve as the judgment unit, and the Kolmogorov-Smirnov test is used to identify the abnormal area. Finally, intensity correction is performed by joint weighting of adjacent scan lines and neighborhood intensity, where the joint weighting can ensure the intensity details while eliminating the deviation from the neighborhood intensity. In addition, a unique bidirectional moving strategy is introduced to weaken the decline of strength correction accuracy caused by insufficient correction accumulation. Experiments have illustrated that this approach can effectively solve the AGC compensation anomaly problem, and compared to the pre-correction, the average absolute percentage error of the corrected intensity data decreased by about 0.27, the root mean square error decreased by about 693, and the intensity deviation of the abnormal area was controlled within 26 DN (Digital Number), thus obtaining a high-quality intensity image.
Airborne Laser Bathymetry (ALB) as an established surveying procedure is certainly operated in blue-green region (532 nm) for penetrating the water column to collect depth. Alongside geometric information accepted widely, ALB typically record the radiometric properties (backscattering intensity) about sensed targets and assist with accurate strips registration, fine ground (sediment) cover classification, and advanced geometric modelling. However, due to the design limitations of Automatic Gain Control (AGC), there is a delay in gain value adjustment, particularly prominent in island and coastal areas with more high-return and low-return targets such as exposed rocks and water, which throws the issue of intensity compensation abnormality into stark relief. In response to this issue, a local weighted intensity correction method based on bidirectional movement is designed. Firstly, effective intensity is extracted by index sharing and elevation information. Then, the emission angles are used to divide the scan line and serve as the judgment unit, and the Kolmogorov-Smirnov test is used to identify the abnormal area. Finally, intensity correction is performed by joint weighting of adjacent scan lines and neighborhood intensity, where the joint weighting can ensure the intensity details while eliminating the deviation from the neighborhood intensity. In addition, a unique bidirectional moving strategy is introduced to weaken the decline of strength correction accuracy caused by insufficient correction accumulation. Experiments have illustrated that this approach can effectively solve the AGC compensation anomaly problem, and compared to the pre-correction, the average absolute percentage error of the corrected intensity data decreased by about 0.27, the root mean square error decreased by about 693, and the intensity deviation of the abnormal area was controlled within 26 DN (Digital Number), thus obtaining a high-quality intensity image.
2023, 45(10): 168-182.
doi: 10.12284/hyxb2023151
Abstract:
Multispectral images are greatly affected by factors such as clouds, fog, and solar flares, which makes it difficult to automatically extract high-precision green tides under complex weather conditions. Based on the multi-spectral images of my country’s HY-1C/D satellite CZI payload, using data mining technology to explore the difference in data distribution between green tide areas and non-green tide areas, we propose a high-precision and fully automatic green tide extraction method , which can be applied to HY-1C/D CZI sensor data. First of all, the thick cloud area is removed by preliminary extraction rules to achieve preliminary classification. Then, the correctly classified green tide samples and non-green tide samples were used as positive and negative samples respectively, and these samples were used as experimental data to train the decision tree model, and the automatic extraction rules of green tide were obtained according to the model. Finally, 5 strategies for correcting misclassifications were designed to achieve fully automatic extraction of green tides. In order to verify the effectiveness of the method, we collected 25 images of the green tide outbreak period in the Yellow Sea in 2021 for automatic detection experiments, and compared the experimental results with traditional index methods (NDVI, VB-FAH) and deep learning methods (ResNet50, U-Net). The results showed that the method outperformed other methods in terms of accuracy, Kappa coefficient, F1-Score, and MIoU. The accuracy of green tide extraction was higher in areas with thick clouds, thin clouds, cloudless clouds, cloud spots, and flares.
Multispectral images are greatly affected by factors such as clouds, fog, and solar flares, which makes it difficult to automatically extract high-precision green tides under complex weather conditions. Based on the multi-spectral images of my country’s HY-1C/D satellite CZI payload, using data mining technology to explore the difference in data distribution between green tide areas and non-green tide areas, we propose a high-precision and fully automatic green tide extraction method , which can be applied to HY-1C/D CZI sensor data. First of all, the thick cloud area is removed by preliminary extraction rules to achieve preliminary classification. Then, the correctly classified green tide samples and non-green tide samples were used as positive and negative samples respectively, and these samples were used as experimental data to train the decision tree model, and the automatic extraction rules of green tide were obtained according to the model. Finally, 5 strategies for correcting misclassifications were designed to achieve fully automatic extraction of green tides. In order to verify the effectiveness of the method, we collected 25 images of the green tide outbreak period in the Yellow Sea in 2021 for automatic detection experiments, and compared the experimental results with traditional index methods (NDVI, VB-FAH) and deep learning methods (ResNet50, U-Net). The results showed that the method outperformed other methods in terms of accuracy, Kappa coefficient, F1-Score, and MIoU. The accuracy of green tide extraction was higher in areas with thick clouds, thin clouds, cloudless clouds, cloud spots, and flares.
2023, 45(10): 183-194.
doi: 10.12284/hyxb2023131
Abstract:
Random errors between systems are not correlated is a necessary assumption for Triple Collocation (TC) analysis, but this assumption does not always hold in practice. The least squares-based Extended Collocation (EC) method can estimate random error in the presence of error correlation, but it cannot accurately estimate standard deviation (SD) of the random error as error correlation is weak. This paper proposes an error estimation method for the fourth system using three error-independent systems, which can estimate the SD of the system error more accurately in case of weak correlation by considering both error correlation and representative error. The SD of the errors of the scatterometer, radiometer and altimeter are 0.600 m/s, 0.742 m/s and 0.533 m/s respectively, as assumed that random errors of three HY-2B wind speed products are independent. The SD of error of ERA5 reanalysis wind speed is also estimated to be 0.810 m/s, the correlation coefficient of the errors of wind speed between HY-2B scatterometer and the ERA5 is 0.231, the correlation coefficient of the errors of wind speed between HY-2B radiometer and the ERA5 is 0.105. This paper proposes a method to estimate random errors and their correlation with the fourth dataset using three known error independent datasets, which achieves a more precise estimation for the SD of the random error in the case of weak correlation, and it helps to use these data better in assimilation and fusion.
Random errors between systems are not correlated is a necessary assumption for Triple Collocation (TC) analysis, but this assumption does not always hold in practice. The least squares-based Extended Collocation (EC) method can estimate random error in the presence of error correlation, but it cannot accurately estimate standard deviation (SD) of the random error as error correlation is weak. This paper proposes an error estimation method for the fourth system using three error-independent systems, which can estimate the SD of the system error more accurately in case of weak correlation by considering both error correlation and representative error. The SD of the errors of the scatterometer, radiometer and altimeter are 0.600 m/s, 0.742 m/s and 0.533 m/s respectively, as assumed that random errors of three HY-2B wind speed products are independent. The SD of error of ERA5 reanalysis wind speed is also estimated to be 0.810 m/s, the correlation coefficient of the errors of wind speed between HY-2B scatterometer and the ERA5 is 0.231, the correlation coefficient of the errors of wind speed between HY-2B radiometer and the ERA5 is 0.105. This paper proposes a method to estimate random errors and their correlation with the fourth dataset using three known error independent datasets, which achieves a more precise estimation for the SD of the random error in the case of weak correlation, and it helps to use these data better in assimilation and fusion.
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