Current Articles
2024, Volume 46, Issue 12
Display Method:
2024,
46(12):
1-12.
doi: 10.12284/hyxb2024107
Abstract:
Rapid changes in the Arctic environment significantly impact the characteristics of water masses in the Arctic Ocean, potentially affecting the ocean’s physical and biogeochemical processes. This study utilizes the latest MOSAiC observation data (from October 2019 to August 2020) and high-resolution reanalysis data (GLORYS12V1) to analyze the variations in temperature and salinity of water masses across the Eurasian Basin along the MOSAiC drift trajectory, and to explore the influence of the Atlantic inflow on these variations. The results show that: (1) Both temperature and salinity within the upper 100 m layer along the drift trajectory exhibit an overall pattern of initially increasing and then decreasing from the Amundsen Basin to the Nansen Basin. The spatial variation in salinity is greatest within the 0−20 m layer, with highly saline surface water (S >34) present in Nansen Basin. In contrast, the variation in temperature is greatest at the 100 m layer, with the depth of 0℃ isothermal less than 100 m in parts of the Nansen Basin. Although GLORYS12V1 simulates the higher temperature in the upper Nansen Basin, it reasonably captures the main features of horizontal and vertical variations in temperature and salinity along the drift trajectory. (2) The warm and saline Atlantic water generally flows anticlockwise in the Eurasian Basin, with its depth gradually deepening during transport, which predominantly determines the overall variations in temperature and salinity in intermedia and upper layers in the Eurasian Basin. The high salinity of surface water in the Nansen Basin is due to the drift trajectory involved into the regions influenced by deep winter convection in northern Svalbard. Strong wind events play a limited role in the distributional differences of temperature and salinity along the drift trajectory. (3) In the western Nansen Basin, the GLORYS12V1 reanalysis exhibits a northward deviation in the simulated horizontal extent of Atlantic Water, which results in an over estimation of temperature compared to in-situ observations. To improve the accuracy of the GLORYS12V1 simulated results, refining the setting of Atlantic inflow flux at the open boundary is suggested.
Rapid changes in the Arctic environment significantly impact the characteristics of water masses in the Arctic Ocean, potentially affecting the ocean’s physical and biogeochemical processes. This study utilizes the latest MOSAiC observation data (from October 2019 to August 2020) and high-resolution reanalysis data (GLORYS12V1) to analyze the variations in temperature and salinity of water masses across the Eurasian Basin along the MOSAiC drift trajectory, and to explore the influence of the Atlantic inflow on these variations. The results show that: (1) Both temperature and salinity within the upper 100 m layer along the drift trajectory exhibit an overall pattern of initially increasing and then decreasing from the Amundsen Basin to the Nansen Basin. The spatial variation in salinity is greatest within the 0−20 m layer, with highly saline surface water (S >34) present in Nansen Basin. In contrast, the variation in temperature is greatest at the 100 m layer, with the depth of 0℃ isothermal less than 100 m in parts of the Nansen Basin. Although GLORYS12V1 simulates the higher temperature in the upper Nansen Basin, it reasonably captures the main features of horizontal and vertical variations in temperature and salinity along the drift trajectory. (2) The warm and saline Atlantic water generally flows anticlockwise in the Eurasian Basin, with its depth gradually deepening during transport, which predominantly determines the overall variations in temperature and salinity in intermedia and upper layers in the Eurasian Basin. The high salinity of surface water in the Nansen Basin is due to the drift trajectory involved into the regions influenced by deep winter convection in northern Svalbard. Strong wind events play a limited role in the distributional differences of temperature and salinity along the drift trajectory. (3) In the western Nansen Basin, the GLORYS12V1 reanalysis exhibits a northward deviation in the simulated horizontal extent of Atlantic Water, which results in an over estimation of temperature compared to in-situ observations. To improve the accuracy of the GLORYS12V1 simulated results, refining the setting of Atlantic inflow flux at the open boundary is suggested.
2024,
46(12):
13-25.
doi: 10.12284/hyxb2024125
Abstract:
In recent decades, the beaches on both sides of the Jiehe River (hereinafter referred to as Jiehe Beach) in the northeastern part of Laizhou Bay have suffered severe erosion due to reduced riverine sediment input to the sea. Additionally, the construction of coastal engineering projects such as Yulong Island (a large artificial offshore island) has made the evolution of the Jiehe Beach shoreline exceptionally complex. This paper utilizes1186 satellite images from 1984 to 2024, employing a transect-focused method and sub-pixel shoreline recognition technology to study the evolution of the Jiehe Beach shoreline and assess the impacts of river sediment discharge and coastal engineering. The results show that the early evolution (1984−2004) of Jiehe Beach was primarily controlled by the closure and opening of the Jiehe River estuary, the alongshore movement of sand spits, and the onshore movement of sandbars, with overall erosion occurring. The later evolution (2004−2024) of Jiehe Beach was mainly influenced by the construction of coastal engineering projects such as Yulong Island, with overall accretion occurring. In today’s era of intensifying coastal development, the rational layout of coastal engineering is expected to mitigate beach erosion.
In recent decades, the beaches on both sides of the Jiehe River (hereinafter referred to as Jiehe Beach) in the northeastern part of Laizhou Bay have suffered severe erosion due to reduced riverine sediment input to the sea. Additionally, the construction of coastal engineering projects such as Yulong Island (a large artificial offshore island) has made the evolution of the Jiehe Beach shoreline exceptionally complex. This paper utilizes
2024,
46(12):
26-39.
doi: 10.12284/hyxb2024129
Abstract:
Sediment transport is a fundamental issue in the study of coastal and estuarine environments, holding significant scientific importance and practical value for the evolution of estuarine geomorphology, ecological environment, and engineering construction. This paper takes the estuary of the Moyang River as an example, based on the sea current, wave and suspended sediment concentration data measured by ship and bottom tripod, analyzes the alongshore and cross-shore transport trends of suspended sediment on the fixed cross-section of the Moyang River estuary, and calculates the sediment transport flux. It explores the sediment transport mechanisms and patterns in wave-tidal estuaries, with the main findings including: (1) During the flood season at the river mouth, the sediment transport is mainly controlled by the runoff, with the sediment transport flux increasing as the flow flux increases. The alongshore and cross-shore sediment transport reaches the maximum value during the neap tide with the largest flow, which are 111.9 g/(m²·s) and 269.5 g/(m²·s) respectively. At the mouth bar in the flood season, the sediment transport is jointly controlled by waves and tides. The alongshore sediment transport is consistently westward along the coast during both spring and neap tides, while the cross-shore sediment transport is dominated by the ebb tide during the spring tide with an offshore transport of 4.0 g/(m²·s), and by waves during the neap tide with an onshore transport of 19.0 g/(m²·s). (2) During the dry season, the mouth bar is primarily influenced by tidal currents and wave action. Sediment transport along the vertical shore predominantly occurs due to falling tidal currents moving seaward, while coastal transport is governed by wave energy, resulting in an eastward movement under the influence of wave-generated coastal currents. On the eastern side of the mouth bar during this season, tidal currents and waves also play a significant role; vertical shore transport is mainly driven by rising tides during spring tide periods before transitioning to offshore transport as tidal forces diminish. Coastal transport remains affected by wave-induced coastal currents and continues its eastward trajectory. (3) During the flood season observation period, the offshore transport at the river mouth is significant, and the flow direction of each water layer is consistent vertically. During the neap tide, there is a differentiation in the flow direction of the water layers, with the surface layer transporting offshore and the bottom layer onshore. At the mouth bar, the flow direction of each water layer is relatively consistent vertically during both spring and neap tides. Still, after tidal averaging, the spring tide shows offshore transport in all water layers, while the neap tide shows onshore transport in all water layers. During the neap tide, the influence of waves is evident, with the onshore transport ratio reaching 79%. (4) Under the influence of runoff and ebb current, the mouth of Moyang River estuary mainly carries sediment to the sea. The most significant factors affecting sediment transport at the mouth bar are the seaward tidal currents and the alongshore sediment movements driven by waves.
Sediment transport is a fundamental issue in the study of coastal and estuarine environments, holding significant scientific importance and practical value for the evolution of estuarine geomorphology, ecological environment, and engineering construction. This paper takes the estuary of the Moyang River as an example, based on the sea current, wave and suspended sediment concentration data measured by ship and bottom tripod, analyzes the alongshore and cross-shore transport trends of suspended sediment on the fixed cross-section of the Moyang River estuary, and calculates the sediment transport flux. It explores the sediment transport mechanisms and patterns in wave-tidal estuaries, with the main findings including: (1) During the flood season at the river mouth, the sediment transport is mainly controlled by the runoff, with the sediment transport flux increasing as the flow flux increases. The alongshore and cross-shore sediment transport reaches the maximum value during the neap tide with the largest flow, which are 111.9 g/(m²·s) and 269.5 g/(m²·s) respectively. At the mouth bar in the flood season, the sediment transport is jointly controlled by waves and tides. The alongshore sediment transport is consistently westward along the coast during both spring and neap tides, while the cross-shore sediment transport is dominated by the ebb tide during the spring tide with an offshore transport of 4.0 g/(m²·s), and by waves during the neap tide with an onshore transport of 19.0 g/(m²·s). (2) During the dry season, the mouth bar is primarily influenced by tidal currents and wave action. Sediment transport along the vertical shore predominantly occurs due to falling tidal currents moving seaward, while coastal transport is governed by wave energy, resulting in an eastward movement under the influence of wave-generated coastal currents. On the eastern side of the mouth bar during this season, tidal currents and waves also play a significant role; vertical shore transport is mainly driven by rising tides during spring tide periods before transitioning to offshore transport as tidal forces diminish. Coastal transport remains affected by wave-induced coastal currents and continues its eastward trajectory. (3) During the flood season observation period, the offshore transport at the river mouth is significant, and the flow direction of each water layer is consistent vertically. During the neap tide, there is a differentiation in the flow direction of the water layers, with the surface layer transporting offshore and the bottom layer onshore. At the mouth bar, the flow direction of each water layer is relatively consistent vertically during both spring and neap tides. Still, after tidal averaging, the spring tide shows offshore transport in all water layers, while the neap tide shows onshore transport in all water layers. During the neap tide, the influence of waves is evident, with the onshore transport ratio reaching 79%. (4) Under the influence of runoff and ebb current, the mouth of Moyang River estuary mainly carries sediment to the sea. The most significant factors affecting sediment transport at the mouth bar are the seaward tidal currents and the alongshore sediment movements driven by waves.
2024,
46(12):
40-52.
doi: 10.12284/hyxb2024055
Abstract:
Sandy and mixed beach-bar, which has good exploration potential, are widely developed in the upper fourth member of Shahejie Formation(Es4U) to the lower third member of Shahejie Formation (Es3L) of the Laizhou Bay Sag in the Bohai Bay Basin. At present, the sedimentary characteristics, genesis mechanism and evolution model of the beach-bar are still poorly understood, which seriously restricts the exploration and prediction of this type of sedimentation. Therefore, this study makes comprehensive use of drilling, logging, and seismic data to finely recover the micro-paleogeomorphology of the study area, clarifies the controlling role of geomorphology of the multi-stage gentle slope on the development of the beach-bar in the study area, sums up the depositional characteristics and the main controlling factors of the sand bodies of the beach-bar at different locations, and constructs the depositional model. The results show that: (1) sandy beach-bar are mainly developed in the front flanks of the braided river delta of the Es4U, which are mainly controlled by the windward geomorphic features of the first-stage gentle slope, strong sediment supply and paleo-wind direction. (2) The thick-layered mixed beach-bar are mainly developed in the windward zone of the secondary gentle slope of the Es4U, which is jointly influenced by paleogeomorphology, medium sediment supply and strong coastal currents. (3) The thin-layered mixed beach-bar are developed in the windward zone of the first-stage gentle slope of the Es3L, which is influenced by the combination of paleogeomorphology, weak sediment supply, paleo-wind direction and littoral current. By dividing the multi-stage gentle slope geomorphology, the establishment of the depositional model can help to predict the distribution of the sand body of the beach-bar and provide a reference for the exploration of the sand body of the beach-bar in the Bohai Bay Basin.
Sandy and mixed beach-bar, which has good exploration potential, are widely developed in the upper fourth member of Shahejie Formation(Es4U) to the lower third member of Shahejie Formation (Es3L) of the Laizhou Bay Sag in the Bohai Bay Basin. At present, the sedimentary characteristics, genesis mechanism and evolution model of the beach-bar are still poorly understood, which seriously restricts the exploration and prediction of this type of sedimentation. Therefore, this study makes comprehensive use of drilling, logging, and seismic data to finely recover the micro-paleogeomorphology of the study area, clarifies the controlling role of geomorphology of the multi-stage gentle slope on the development of the beach-bar in the study area, sums up the depositional characteristics and the main controlling factors of the sand bodies of the beach-bar at different locations, and constructs the depositional model. The results show that: (1) sandy beach-bar are mainly developed in the front flanks of the braided river delta of the Es4U, which are mainly controlled by the windward geomorphic features of the first-stage gentle slope, strong sediment supply and paleo-wind direction. (2) The thick-layered mixed beach-bar are mainly developed in the windward zone of the secondary gentle slope of the Es4U, which is jointly influenced by paleogeomorphology, medium sediment supply and strong coastal currents. (3) The thin-layered mixed beach-bar are developed in the windward zone of the first-stage gentle slope of the Es3L, which is influenced by the combination of paleogeomorphology, weak sediment supply, paleo-wind direction and littoral current. By dividing the multi-stage gentle slope geomorphology, the establishment of the depositional model can help to predict the distribution of the sand body of the beach-bar and provide a reference for the exploration of the sand body of the beach-bar in the Bohai Bay Basin.
2024,
46(12):
53-65.
doi: 10.12284/hyxb2024085
Abstract:
Submarine fans developed in the middle Miocene Meishan Formation possess significant potential for natural gas exploration. Most of scholars believed that these Miocene submarine fans were formed primarily by turbidity currents. However, drilling cores revealed the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibited good roundness and poor sorting, indicating that the traditional turbidity formation mechanism cannot fully explain the origin of this type of sandy conglomerates. Furthermore, the classic submarine fan model has limitations in predicting the distribution of sand bodies. Through a comprehensive study involving core, thin section observation, and grain size analysis, we have conducted a systematic investigation of the petrological characteristics and sedimentary structures of submarine fan in the study area. Our findings suggest that submarine fans in the study area resulted from the interaction of turbidity and hyperpycnal flow deposits. We have identified distinct sequences of turbidites and hyperpycnalites within the submarine fan. Based on the paleogeomorphlogy of the study area, we have established a genetic evolution model for the submarine fan in Meishan Formation. This model reveals that the hyperpycnites dominated by feldspathic litharenite, exhibit low compositional maturity. Poor sorting and subangular-circular of the rocks indicate middle-to-high structural maturity. Typical features of hyperpycnal flow include orientated gravel within block sandy conglomerates, reverse-to-normal grain order bedding, parallel bedding, carbonaceous debris, and biological fossil fragments. Multi stage superimposed turbidite sequence and hyperpycnites sequence developed in submarine fan in the study area. The early Meishan period is primarily composed of turbidite submarine fan lobes, while the middle Meishan period is dominated by hyperpycnites submarine fan channels. The late Meishan period, on the other hand, is mainly composed of turbidite submarine fan channels. We predict that more favorable submarine fan sand bodies could be found in the southern part of the study area. The results can serve as a basis for predicting the distribution of favorable submarine fan reservoirs of the Qiongdongnan Basin, and they hold significance for selecting exploration and development targets for hydrocarbon exploration.
Submarine fans developed in the middle Miocene Meishan Formation possess significant potential for natural gas exploration. Most of scholars believed that these Miocene submarine fans were formed primarily by turbidity currents. However, drilling cores revealed the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibited good roundness and poor sorting, indicating that the traditional turbidity formation mechanism cannot fully explain the origin of this type of sandy conglomerates. Furthermore, the classic submarine fan model has limitations in predicting the distribution of sand bodies. Through a comprehensive study involving core, thin section observation, and grain size analysis, we have conducted a systematic investigation of the petrological characteristics and sedimentary structures of submarine fan in the study area. Our findings suggest that submarine fans in the study area resulted from the interaction of turbidity and hyperpycnal flow deposits. We have identified distinct sequences of turbidites and hyperpycnalites within the submarine fan. Based on the paleogeomorphlogy of the study area, we have established a genetic evolution model for the submarine fan in Meishan Formation. This model reveals that the hyperpycnites dominated by feldspathic litharenite, exhibit low compositional maturity. Poor sorting and subangular-circular of the rocks indicate middle-to-high structural maturity. Typical features of hyperpycnal flow include orientated gravel within block sandy conglomerates, reverse-to-normal grain order bedding, parallel bedding, carbonaceous debris, and biological fossil fragments. Multi stage superimposed turbidite sequence and hyperpycnites sequence developed in submarine fan in the study area. The early Meishan period is primarily composed of turbidite submarine fan lobes, while the middle Meishan period is dominated by hyperpycnites submarine fan channels. The late Meishan period, on the other hand, is mainly composed of turbidite submarine fan channels. We predict that more favorable submarine fan sand bodies could be found in the southern part of the study area. The results can serve as a basis for predicting the distribution of favorable submarine fan reservoirs of the Qiongdongnan Basin, and they hold significance for selecting exploration and development targets for hydrocarbon exploration.
2024,
46(12):
66-78.
doi: 10.12284/hyxb2024031
Abstract:
The buried hill oil and gas reservoirs have become an important exploration field in China’s marine basins. The northwestern area of Shaleitian area of Bohai Bay Basin is a typical carbonate buried hill zone. Due to the lack of research on the reservoir control effect of multiple stage fractures and their related karstification, the oil and gas exploration of carbonate buried hills is restricted. This paper conducts a detailed analysis of the development characteristics of the fracture-cave system in carbonate buried hill reservoirs in the northwestern Shaleitian Uplift, and studies the reservoir control effects of fractures and karst. The results indicate that the lower Paleozoic carbonate buried hills in the northwestern area of Shaleitian Uplift belong to fracture related karst reservoirs. The reservoir space includes dissolution pores, structural fractures, and expansion pores along the structural fractures. High quality reservoirs have lithological selectivity, and fractures and dissolution pores developed in microlite crystalline dolomite and fine crystalline dolomite are better. The reservoir mainly develops three sets of fractures, with E−W and NE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian. The third set of NW oriented tensile fractures is related to the intracratonic movement during the Himalayan orogeny, and compression is the main mechanism for forming high-density fractures. The later stage of extension is a necessary condition for the relaxation of fractures to form reservoir spaces. The Lower Paleozoic carbonate buried hill reservoirs have undergone three stages of karstification, which are karstification in the steady Caledonian tectonic background, karstification in the Indosinian compressive background, and fault block-horst karstification in the Yanshanian-Himalayan extensional background. In summary, the carbonate buried hill reservoirs in the northwestern Shaleitian Uplift are formed by multiple stages and multiple types of tectonic-karst processes, and the analysis of the differences in the degree of recombination in different structural parts is an important factor in understanding the reservoir formation mechanism.
The buried hill oil and gas reservoirs have become an important exploration field in China’s marine basins. The northwestern area of Shaleitian area of Bohai Bay Basin is a typical carbonate buried hill zone. Due to the lack of research on the reservoir control effect of multiple stage fractures and their related karstification, the oil and gas exploration of carbonate buried hills is restricted. This paper conducts a detailed analysis of the development characteristics of the fracture-cave system in carbonate buried hill reservoirs in the northwestern Shaleitian Uplift, and studies the reservoir control effects of fractures and karst. The results indicate that the lower Paleozoic carbonate buried hills in the northwestern area of Shaleitian Uplift belong to fracture related karst reservoirs. The reservoir space includes dissolution pores, structural fractures, and expansion pores along the structural fractures. High quality reservoirs have lithological selectivity, and fractures and dissolution pores developed in microlite crystalline dolomite and fine crystalline dolomite are better. The reservoir mainly develops three sets of fractures, with E−W and NE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian. The third set of NW oriented tensile fractures is related to the intracratonic movement during the Himalayan orogeny, and compression is the main mechanism for forming high-density fractures. The later stage of extension is a necessary condition for the relaxation of fractures to form reservoir spaces. The Lower Paleozoic carbonate buried hill reservoirs have undergone three stages of karstification, which are karstification in the steady Caledonian tectonic background, karstification in the Indosinian compressive background, and fault block-horst karstification in the Yanshanian-Himalayan extensional background. In summary, the carbonate buried hill reservoirs in the northwestern Shaleitian Uplift are formed by multiple stages and multiple types of tectonic-karst processes, and the analysis of the differences in the degree of recombination in different structural parts is an important factor in understanding the reservoir formation mechanism.
2024,
46(12):
79-86.
doi: 10.12284/hyxb2024111
Abstract:
In engineering practice, the Morison equation is commonly used to calculate wave loads on slender structures. Traditionally, the Morison equation for wave force calculation is often simplified, assuming the pile as a rigid body and neglecting the elastic deformation of the pile. By employing the Radial Basis Function (RBF), a mesh-free method, this study simultaneously solves the Morison equation, which considers pile elastic deformation, and the dynamic balance equation. This approach obtains the wave force and dynamic response of a single pile under wave load, and compares the results with those from standard methods and previous literature to validate its accuracy. Applying this method to actual engineering cases reveals the dynamic response of the working platform under the most unfavorable conditions. The RBF method is computationally straightforward and easy to master, making it suitable for practical engineering applications and providing a new direction for the calculation of offshore structures in the future.
In engineering practice, the Morison equation is commonly used to calculate wave loads on slender structures. Traditionally, the Morison equation for wave force calculation is often simplified, assuming the pile as a rigid body and neglecting the elastic deformation of the pile. By employing the Radial Basis Function (RBF), a mesh-free method, this study simultaneously solves the Morison equation, which considers pile elastic deformation, and the dynamic balance equation. This approach obtains the wave force and dynamic response of a single pile under wave load, and compares the results with those from standard methods and previous literature to validate its accuracy. Applying this method to actual engineering cases reveals the dynamic response of the working platform under the most unfavorable conditions. The RBF method is computationally straightforward and easy to master, making it suitable for practical engineering applications and providing a new direction for the calculation of offshore structures in the future.
2024,
46(12):
87-99.
doi: 10.12284/hyxb2024117
Abstract:
In real ocean environments, natural reefs typically exhibit complex topography, with reef platforms presenting non-uniform characteristics. Previous extensive research has mainly focused on simplified stepped reef models and has not conducted in-depth studies on the impact of non-uniform reef platforms on the propagation and evolution characteristics of waves. To address the shortcomings of previous research, this paper conducted physical model experiments to systematically study the propagation and evolution characteristics of tsunami-like waves over complex reef platforms. Previous studies did not consider the impact of the non-uniformity of reef platform topography on solitary waves, therefore, this paper also analyzed the effects of incident wave height and reef platform water depth. To investigate the impact of non-uniform reef platform geometric characteristics on the propagation and evolution of tsunami-like waves and the load characteristics of sea walls under different incident wave conditions, this paper further carried out a series of high-resolution numerical calculations. First, physical experiments were used to verify the accuracy of the numerical simulation method, and then numerical calculations were used to study the effects of two wave parameters, incident wave height and reef platform submergence depth, and three complex reef topography factors—the height of the second reef platform, the position of the reef platform steps, and the slope of the reef front slope—on the maximum wave height along the path, reflection coefficient, maximum run-up height, distribution of the maximum impact pressure on the sea wall, and the variation of the maximum total force and total moment on the sea wall. The research results indicate that the reflection coefficient of solitary waves decreases with increasing incident wave height and increases with increasing reef platform water depth. The maximum run-up height increases with increasing incident wave height and decreases with increasing cot α of the reef front slope. The maximum total force and maximum total moment on the sea wall increase with increasing incident wave height and reef platform water depth, and decrease with increasing height of the second reef platform. The position of the maximum impact pressure on the sea wall rises with increasing incident wave height, increasing reef platform water depth, and decreasing distance between the reef platform steps and the sea wall. The research results can provide a reference for further protecting coastal facilities from the impact of extreme marine environments.
In real ocean environments, natural reefs typically exhibit complex topography, with reef platforms presenting non-uniform characteristics. Previous extensive research has mainly focused on simplified stepped reef models and has not conducted in-depth studies on the impact of non-uniform reef platforms on the propagation and evolution characteristics of waves. To address the shortcomings of previous research, this paper conducted physical model experiments to systematically study the propagation and evolution characteristics of tsunami-like waves over complex reef platforms. Previous studies did not consider the impact of the non-uniformity of reef platform topography on solitary waves, therefore, this paper also analyzed the effects of incident wave height and reef platform water depth. To investigate the impact of non-uniform reef platform geometric characteristics on the propagation and evolution of tsunami-like waves and the load characteristics of sea walls under different incident wave conditions, this paper further carried out a series of high-resolution numerical calculations. First, physical experiments were used to verify the accuracy of the numerical simulation method, and then numerical calculations were used to study the effects of two wave parameters, incident wave height and reef platform submergence depth, and three complex reef topography factors—the height of the second reef platform, the position of the reef platform steps, and the slope of the reef front slope—on the maximum wave height along the path, reflection coefficient, maximum run-up height, distribution of the maximum impact pressure on the sea wall, and the variation of the maximum total force and total moment on the sea wall. The research results indicate that the reflection coefficient of solitary waves decreases with increasing incident wave height and increases with increasing reef platform water depth. The maximum run-up height increases with increasing incident wave height and decreases with increasing cot α of the reef front slope. The maximum total force and maximum total moment on the sea wall increase with increasing incident wave height and reef platform water depth, and decrease with increasing height of the second reef platform. The position of the maximum impact pressure on the sea wall rises with increasing incident wave height, increasing reef platform water depth, and decreasing distance between the reef platform steps and the sea wall. The research results can provide a reference for further protecting coastal facilities from the impact of extreme marine environments.
2024,
46(12):
100-110.
doi: 10.12284/hyxb2024115
Abstract:
The streamline construction and placement of the marine flow field is of great significance for recognizing and understanding the marine flow field. In the process of streamline drawing, the selection of integration step is very important, which can directly affect the effect of streamline placement. The fixed step size algorithm is often not used because it cannot adapt to the changing curvature. The previous adaptive step size streamline algorithm has the problems of low degree of freedom and poor multi-scale applicability. In view of the above problems, this paper introduces information entropy into the step size calculation for the first time, and proposes an adaptive step size algorithm of marine streamline controlled by information entropy. Firstly, the entropy field is obtained by calculating the information entropy of the flow field, and then the flow field is divided into high entropy region and low entropy region according to the entropy value, and each integration point is given a new step size, so that the flow field can adaptively adjust the step size according to the intensity of change, that is, the step size of the high entropy region (the region with sharp change) is smaller, and the step size of the low entropy region (the region with gentle change) is larger. The experimental results show that the proposed algorithm can significantly increase the number of integration points and streamlines in the rapidly changing region, better draw the details of the streamline at the feature, and reduce the number of integration points and streamlines in the unimportant region without affecting the placement effect to improve the computational efficiency. Compared with the previous adaptive step size algorithm, the proposed algorithm significantly improves the degree of freedom of step size adjustment and the scale applicability, and can be applied to different scales of marine flow field.
The streamline construction and placement of the marine flow field is of great significance for recognizing and understanding the marine flow field. In the process of streamline drawing, the selection of integration step is very important, which can directly affect the effect of streamline placement. The fixed step size algorithm is often not used because it cannot adapt to the changing curvature. The previous adaptive step size streamline algorithm has the problems of low degree of freedom and poor multi-scale applicability. In view of the above problems, this paper introduces information entropy into the step size calculation for the first time, and proposes an adaptive step size algorithm of marine streamline controlled by information entropy. Firstly, the entropy field is obtained by calculating the information entropy of the flow field, and then the flow field is divided into high entropy region and low entropy region according to the entropy value, and each integration point is given a new step size, so that the flow field can adaptively adjust the step size according to the intensity of change, that is, the step size of the high entropy region (the region with sharp change) is smaller, and the step size of the low entropy region (the region with gentle change) is larger. The experimental results show that the proposed algorithm can significantly increase the number of integration points and streamlines in the rapidly changing region, better draw the details of the streamline at the feature, and reduce the number of integration points and streamlines in the unimportant region without affecting the placement effect to improve the computational efficiency. Compared with the previous adaptive step size algorithm, the proposed algorithm significantly improves the degree of freedom of step size adjustment and the scale applicability, and can be applied to different scales of marine flow field.
2024,
46(12):
111-121.
doi: 10.12284/hyxb2024127
Abstract:
The prediction of El Niño-Southern Oscillation is one of the hot issues in climate change research. This paper combines swin-transformer model with spatio-temporal fusion attention mechanism, and uses CMIP6 multi-model simulation historical data from 1850 to 2014, SODA assimilated data from 1871 to 1979 and GODAS assimilated data from 1980 to 2023 to construct El Niño-Southern Oscillation prediction model—ENSO-STformer. The model was fully trained on CMIP6 and SODA datasets and evaluated on GODAS data. The results show that the average skill of this model in predicting the Niño3.4 index at 11-month lead times exceeds those of CanCM4, CCSM3, and GFDLaer04 by 5.1%, 21.6%, and 12.4% respectively. Meanwhile, the Niño3.4 index related skills of the proposed model are significantly better than other deep learning models in the medium and long term. Effective ENSO forecasts can be made for up to 24 months, and the 2015−2016 El Niño event simulation shows strong ability to cope with spring forecast obstacles.
The prediction of El Niño-Southern Oscillation is one of the hot issues in climate change research. This paper combines swin-transformer model with spatio-temporal fusion attention mechanism, and uses CMIP6 multi-model simulation historical data from 1850 to 2014, SODA assimilated data from 1871 to 1979 and GODAS assimilated data from 1980 to 2023 to construct El Niño-Southern Oscillation prediction model—ENSO-STformer. The model was fully trained on CMIP6 and SODA datasets and evaluated on GODAS data. The results show that the average skill of this model in predicting the Niño3.4 index at 11-month lead times exceeds those of CanCM4, CCSM3, and GFDLaer04 by 5.1%, 21.6%, and 12.4% respectively. Meanwhile, the Niño3.4 index related skills of the proposed model are significantly better than other deep learning models in the medium and long term. Effective ENSO forecasts can be made for up to 24 months, and the 2015−2016 El Niño event simulation shows strong ability to cope with spring forecast obstacles.
2024,
46(12):
122-134.
doi: 10.12284/hyxb2024119
Abstract:
Short-term precipitation nowcasting is a critical task in both meteorology and hydrology. However, current deep learning methods often yield ambiguous prediction results and exhibit significant cumulative errors. To address the limitations associated with these predictive methods, particularly the challenges of cumulative error and lack of clarity in prediction sequences, we propose a novel approach based on a Multi-scale Attention Encoding-Dynamic Decoding Network (MAEDDN) for short-term precipitation nowcasting. This method leverages the learning of spatiotemporal features from input data to accurately predict future precipitation scenarios. To obtain richer feature information from the input sequences, the encoding process employs convolutional blocks with spatial and channel attention for encoding. And a multi-scale fusion module is introduced to address the challenge of capturing both small-scale and large-scale information in precipitation distribution simultaneously. To enhance the clarity of the predicted sequences, the model needs to better understand the precipitation process. Therefore, in the decoding process, a dynamic decoding network is proposed in response to the generation and dissipation processes accompanying short-term precipitation. This network flexibly filters the decoding process by learning the intensity distribution and change trends of past input data. Experiments are conducted by using the precipitation data from the open-source SEVIR dataset, and comparisons are made with the best methods reported so far. The experimental results reveal that: (1) MAEDDN enhances the forecasting capability in areas with high-intensity precipitation, and (2) The clarity of the predicted image sequences by MAEDDN is significantly better than that of other models. The constructed multi-scale attention encoding captures the complex relationships in meteorological data more effectively, while the dynamic decoding adapts the decoding process based on different scenarios, resulting in more accurate prediction outcomes.
Short-term precipitation nowcasting is a critical task in both meteorology and hydrology. However, current deep learning methods often yield ambiguous prediction results and exhibit significant cumulative errors. To address the limitations associated with these predictive methods, particularly the challenges of cumulative error and lack of clarity in prediction sequences, we propose a novel approach based on a Multi-scale Attention Encoding-Dynamic Decoding Network (MAEDDN) for short-term precipitation nowcasting. This method leverages the learning of spatiotemporal features from input data to accurately predict future precipitation scenarios. To obtain richer feature information from the input sequences, the encoding process employs convolutional blocks with spatial and channel attention for encoding. And a multi-scale fusion module is introduced to address the challenge of capturing both small-scale and large-scale information in precipitation distribution simultaneously. To enhance the clarity of the predicted sequences, the model needs to better understand the precipitation process. Therefore, in the decoding process, a dynamic decoding network is proposed in response to the generation and dissipation processes accompanying short-term precipitation. This network flexibly filters the decoding process by learning the intensity distribution and change trends of past input data. Experiments are conducted by using the precipitation data from the open-source SEVIR dataset, and comparisons are made with the best methods reported so far. The experimental results reveal that: (1) MAEDDN enhances the forecasting capability in areas with high-intensity precipitation, and (2) The clarity of the predicted image sequences by MAEDDN is significantly better than that of other models. The constructed multi-scale attention encoding captures the complex relationships in meteorological data more effectively, while the dynamic decoding adapts the decoding process based on different scenarios, resulting in more accurate prediction outcomes.
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