An automatic identification method for the three-dimensional structure of the Kuroshio based on the velocity gradient

Abstract

The present invention provides a method for automatically identifying the three-dimensional structure of the Kuroshio based on the velocity gradient, including: calculating the velocity gradient row by row according to latitude and layer by layer according to depth, and precisely determining the boundary points of the three-dimensional structure of the Kuroshio in each layer and each row by combining the longitude difference constraint and the candidate point screening technique. To adapt to different ocean environments, this method supports the flexible selection of whether to incorporate the influence of topographic factors. By constructing a two-dimensional field of the combined velocity minus the average value and using the zero isocline to determine the bottom boundary depth, the distribution of the Kuroshio structure is finally visualized in the form of a three-dimensional scatter plot, comprehensively presenting its three-dimensional shape. The present invention breaks through the limitation of the traditional method which is limited to surface analysis and difficult to accurately extract the Kuroshio structure in real time, avoids the deficiencies of forced division of water area characteristics and fixed depth setting in the clustering method, realizes the acquisition of real-time structural morphology based on the time resolution of data, and significantly reduces the computational complexity.

Description

Technical Field

[0001] The present invention relates to the technical field of marine environment identification or phenomenon identification and extraction, and particularly to an automatic identification method for the three-dimensional structure of the Kuroshio based on velocity gradient. Background Art

[0002] The Kuroshio is a strong warm current on the western boundary of the North Pacific, characterized by high temperature, high salinity and high flow velocity, and has a profound impact on the marine environment, climate and ecological distribution. Accurately identifying its three-dimensional structure is crucial for studying the Kuroshio path, flow rate changes and environmental effects. Currently, there are mainly three methods: traditional oceanographic method analysis, calculation of the Kuroshio distribution based on satellite remote sensing technology and gradient algorithm, and clustering analysis of the Kuroshio based on sound velocity profile. Although these methods provide a certain degree of effectiveness in practical applications, there are still deficiencies in obtaining comprehensive, accurate and real-time three-dimensional structure information of the Kuroshio.

[0003] Firstly, the traditional oceanographic method detects the Kuroshio water body structure by analyzing the flow field, temperature gradient or salinity change, which is simple and intuitive, but it is difficult to capture the three-dimensional features in a complex flow field. Especially in the depth direction, it is limited by data and processing capabilities, with insufficient accuracy, low calculation efficiency and limited automation. Secondly, satellite remote sensing technology uses sea surface temperature and gradient algorithm to quickly obtain the Kuroshio distribution, but it is limited to the surface layer and difficult to provide depth information. Affected by resolution and environmental interference, the three-dimensional reconstruction accuracy and stability are poor. Finally, the clustering analysis method based on sound velocity profile is used for Kuroshio identification. This method uses the characteristics of sound velocity to reflect water temperature, salinity and pressure, and divides water masses through a clustering algorithm to identify the location of the Kuroshio. As a comprehensive physical quantity, sound velocity can effectively distinguish water area characteristics and has certain advantages. However, this method forcibly divides the water area into fixed categories, without considering the actual differences and dynamic changes of the water area, and requires stratified processing at specific depths, resulting in discontinuity between layers. Even areas without the Kuroshio are forcibly classified, and the actual depth position of the Kuroshio cannot be determined.

[0004] In summary, although the existing methods have their own advantages, they are difficult to meet the requirements of obtaining comprehensive, accurate and real-time three-dimensional structures. Therefore, the present invention proposes an automated technology based on velocity gradient, which can effectively solve the deficiencies of the existing technology in obtaining the three-dimensional structure of the Kuroshio and provide more reliable technical support for the research and application of the Kuroshio. Summary of the Invention

[0005] The present invention provides an automatic identification method for the three-dimensional structure of the Kuroshio based on velocity gradient, so as to solve the problem of the deficiencies of the existing technology in obtaining the three-dimensional structure of the Kuroshio, and realizes the automated, real-time and accurate identification of the three-dimensional structure of the Kuroshio, providing more reliable technical support for the research and application of the Kuroshio.

[0006] The present invention provides a method for automatically identifying the three-dimensional structure of the Kuroshio based on the velocity gradient, comprising the following steps:

[0007] A. Calculating the horizontal width of the Kuroshio based on the velocity gradient: First, extract the meridional velocity and zonal velocity of the sea area to be measured from the ocean current field data, and then calculate the full-field velocity data of the current field to obtain the full-field velocity distribution of the current field; thereafter, calculate the velocity partial derivative of each latitude row along the longitude direction, and identify the horizontal width of the Kuroshio by using the inflection point characteristics of the partial derivative;

[0008] B. Determining the bottom boundary of the Kuroshio water body based on depth screening: Determine the bottom boundary depth of the Kuroshio water body by screening the velocity partial derivative results of each depth layer;

[0009] C. Identifying the three-dimensional structure of the Kuroshio in the ocean area without considering the terrain;

[0010] D. Identifying the three-dimensional structure of the Kuroshio considering the influence of the terrain;

[0011] The specific process of step A is as follows:

[0012] Velocity data extraction and calculation: Obtain the meridional velocity of the sea area to be measured from the input data and the zonal velocity , calculate the combined velocity , providing basic data for subsequent gradient analysis;

[0013] Row-by-row partial derivative calculation and analysis principle: For each latitude row, perform partial derivative calculation on the combined velocity along the longitude direction to obtain the horizontal gradient , and identify by analyzing the change trend of ;

[0014] Inflection point identification: By analyzing the inflection points, maximum gradient, and minimum gradient of the gradient , as candidate points for the left and right boundaries of the Kuroshio, and then determine the positions of the left and right boundaries of the Kuroshio, that is, the horizontal width;

[0015] The identification of the horizontal width of the Kuroshio in step A is divided into the following three stages:

[0016] ① Entering the Kuroshio boundary stage, not yet in the Kuroshio area: When gradually increases and reaches the maximum value, it indicates that the rate of increase in the velocity along the longitude direction is getting faster and faster;

[0017] ② Internal process of the Kuroshio: When is still greater than 0 but starts to decrease, the velocity is still increasing, but the rate of increase gradually slows down. Subsequently, decreases to 0 or even becomes negative, indicating that the trend of velocity increase disappears and even starts to reverse;

[0018] ③Stage of leaving the Kuroshio region: When reaches the minimum value and then starts to rise but remains negative, it indicates that the flow velocity is still decreasing, but the rate of decrease is gradually slowing down;

[0019] Step B includes the following processes:

[0020] Analysis of flow velocity in depth layers: Extract flow velocity data layer by layer along the depth direction, and calculate the horizontal gradient within the specified latitude row for each depth layer ;

[0021] Boundary determination conditions: Apply screening conditions to the gradient results of each depth layer, including the range of gradient values, the gradient difference greater than 2°, and the longitude continuity constraint of boundary points. When a certain depth layer no longer meets the conditions, it is determined as the bottom boundary of the Kuroshio;

[0022] Result integration: Summarize the bottom boundary depths of each latitude row to form the three-dimensional structure contour of the Kuroshio;

[0023] The specific process of Step C is as follows:

[0024] Integration of terrain data: Combine external terrain data. Since the Kuroshio phenomenon is located in the upper ocean, the analysis depth range can be limited to avoid the interference of terrain occlusion on the calculation of flow velocity;

[0025] Gradient calculation and boundary extraction: Calculate the flow velocity gradient along each latitude row within the specified depth range, and determine the horizontal width and bottom boundary of the Kuroshio through the inflection point identification and depth screening methods;

[0026] Three-dimensional structure generation: Integrate the horizontal width and bottom boundary to form the three-dimensional structure of the Kuroshio in the ocean area;

[0027] In Step D, an auxiliary determination mechanism of removing the average value by introducing the combined flow velocity is adopted, and the specific steps are as follows:

[0028] Calculation of the average flow velocity: For each latitude row, calculate the average value of the combined flow velocity along the depth direction , only considering the valid flow velocity data;

[0029] Construction of the flow velocity difference field: Calculate the flow velocity difference field after removing the average value, that is , generate a two-dimensional flow velocity difference distribution field of depth-longitude, and the average depth of the flow velocity can be defined according to the actual terrain of the research sea area;

[0030] Bottom boundary determination: Determine the lowest depth as the bottom boundary of the Kuroshio water body by extracting the zero isocline in the flow velocity difference field;

[0031] Three-dimensional structure generation: Integrate the horizontal width and bottom boundary to form the three-dimensional structure of the Kuroshio in the ocean area.

[0032] Beneficial effects: The present invention realizes the automatic identification of the horizontal width and bottom boundary of the Kuroshio Current through velocity gradient analysis, and combines two schemes of considering the terrain and not considering the terrain, which can flexibly adapt to the needs of different marine environments. Its main advantages include: strong real-time performance, which can quickly generate results based on multi-phase data, reducing the need for a large amount of computing and processing, and avoiding the negative impact of traditional methods relying on multi-year averages on real-time presentation; objectivity and high flexibility, which can define execution conditions according to the characteristics of the Kuroshio Current in different sea areas, avoiding the problem of being limited to the surface or fixed identification depth; both accuracy and completeness, suitable for multi-source data processing; strong adaptability, and can dynamically adjust to data sets of different resolutions. Finally, the present invention intuitively presents the Kuroshio Current structure through three-dimensional visualization, realizes the automatic extraction of the real-time dynamic three-dimensional structure of the Kuroshio Current, and provides an effective technical means for further ocean dynamics research and Kuroshio Current monitoring.

[0033] The above description is only an overview of the technical solutions of the embodiments of the present invention. In order to more clearly understand the technical means of the embodiments of the present invention, they can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiments of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] Figure 1 It is the overall flow chart of the present invention;

[0036] Figure 2 is a flow velocity profile diagram in an example of the present invention;

[0037] Figure 3 is a flow velocity gradient curve diagram in an example of the present invention;

[0038] Figure 4 is a curve diagram of the absolute value of the flow velocity gradient in an example of the present invention;

[0039] Figure 5 is the two-dimensional velocity difference distribution field of depth-longitude after removing the average value of the velocity in the example of the present invention;

[0040] Figure 6 The three-dimensional Kuroshio boundary structure point map is finally extracted without considering the terrain in the example of the present invention;

[0041] Figure 7This is the final three-dimensional Kuroshio boundary structure point map extracted after considering the terrain in the embodiments of the present invention. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0043] Reference to "embodiment" herein means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present invention. The phrase "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0044] To enable those skilled in the art of this technology to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0045] Please refer to Figures 1-7 , the present invention provides a method for automatically identifying the three-dimensional structure of the Kuroshio based on the velocity gradient, including the following steps:

[0046] A. Calculating the horizontal width of the Kuroshio based on the velocity gradient: First, extract the meridional velocity and zonal velocity of the sea area to be measured from the ocean current field data, and then calculate the total field velocity data to obtain the full-field velocity distribution of the current field; then calculate the velocity partial derivative of each latitude row along the longitude direction, and use the inflection point feature of the partial derivative to identify the horizontal width of the Kuroshio;

[0047] B. Determining the bottom boundary of the Kuroshio water body based on depth screening: Screen the velocity partial derivative results of each depth layer to determine the bottom boundary depth of the Kuroshio water body;

[0048] C. Identifying the three-dimensional structure of the Kuroshio in the ocean area without considering the terrain;

[0049] D. Identifying the three-dimensional structure of the Kuroshio considering the influence of the terrain.

[0050] In the present invention, the specific process of step A is as follows:

[0051] Velocity data extraction and calculation: Obtain the meridional velocity and zonal velocity of the sea area to be measured from the input data, and calculate the combined velocity , providing basic data for subsequent gradient analysis;

[0052] Principle of row-by-row partial derivative calculation and analysis: For each latitude row, the partial derivative of the combined flow velocity is calculated along the longitude direction to obtain the horizontal gradient , and identification is carried out by analyzing the changing trend;

[0053] Inflection point identification: By analyzing the inflection points of the gradient , the maximum gradient and the minimum gradient, they are used as candidate points for the left and right boundaries of the Kuroshio, and then the positions of the left and right boundaries of the Kuroshio, that is, the horizontal width, are determined. To ensure the accuracy of the boundary, specific constraint conditions are imposed:

[0054] ① Select the first gradient maximum point in the gradient gentle interval-transition gradient acceleration interval and the first gradient minimum point in the gradient deceleration interval as candidate boundaries, and apply a longitude difference constraint (set a constraint difference according to the width of the Kuroshio current amplitude in different sea areas, such as not exceeding 2°).

[0055] ② Screening is carried out according to the gradient difference condition (set the maximum gradient and minimum gradient thresholds to exclude abnormal gradient values caused by the data itself), to highlight the significant features of the Kuroshio region and ensure the accuracy of the boundary points, and finally determine the horizontal width of the Kuroshio.

[0056] The logic of this method lies in using the spatial change trend of the flow velocity gradient , combined with the dynamic processes of entering the Kuroshio boundary, inside the Kuroshio, and the Kuroshio region, to objectively depict the horizontal range of the Kuroshio, avoiding the deficiencies of traditional methods that rely on empirical thresholds or forced classification by clustering analysis, and providing a reliable basis for the determination of the subsequent three-dimensional structure.

[0057] In the present invention, the identification of the horizontal width of the Kuroshio in step A is divided into the following three stages:

[0058] ① Kuroshio boundary stage, not reaching the Kuroshio region: When gradually increases and reaches the maximum value, it indicates that the rising rate of the flow velocity along the longitude direction is getting faster and faster. This stage can be understood as the sea current being in the "acceleration" stage and advancing towards the inside of the frontal zone, marking the gradual appearance of the left boundary of the Kuroshio region;

[0059] ② Kuroshio internal process: When is still greater than 0 but starts to decrease, the flow velocity is still increasing, but the increasing rate gradually slows down. Subsequently, decreases to 0 or even becomes negative, indicating that the trend of increasing flow velocity disappears and even starts to reverse. This range reflects the process of the sea current passing through the inside of the Kuroshio. The flow velocity has experienced stages from rapid acceleration to reaching the inflection point (maximum flow velocity point) and then gradually entering the deceleration stage, defining the core region of the Kuroshio;

[0060] ③ Stage of leaving the Kuroshio area: When reaches the minimum value and then starts to rise but is still negative, it indicates that the flow velocity is still decreasing, but the rate of decrease is gradually slowing down. This stage means that the ocean current has exited the Kuroshio area and entered a relatively gentle area, marking the right boundary of the Kuroshio area.

[0061] In the present invention, step B includes the following processes:

[0062] Analysis of flow velocity in depth layers: Extract flow velocity data layer by layer along the depth direction, and calculate the horizontal gradient within the specified latitude row for each depth layer ;

[0063] Boundary determination conditions: Apply screening conditions to the gradient results of each depth layer, including the range of gradient values, the gradient difference being greater than 2°, and the longitude continuity constraint of boundary points. When a certain depth layer no longer meets the conditions, it is determined as the bottom boundary of the Kuroshio;

[0064] Result integration: Summarize the bottom boundary depths of each latitude row to form the three-dimensional structure contour of the Kuroshio.

[0065] This method ensures that the identified bottom boundary of the Kuroshio is both accurate and complete through layer-by-layer screening, and can dynamically adapt to the flow field variation characteristics at different depths.

[0066] In the present invention, the specific process of step C is as follows:

[0067] Integration of terrain data: Combine external terrain data. Since the Kuroshio phenomenon is located in the upper ocean, the analysis depth range can be limited to avoid the interference of terrain occlusion on the calculation of flow velocity;

[0068] Gradient calculation and boundary extraction: Calculate the flow velocity gradient along each latitude row within the specified depth range, and determine the horizontal width and bottom boundary of the Kuroshio through inflection point identification and depth screening methods;

[0069] Three-dimensional structure generation: Integrate the horizontal width and the bottom boundary to form the three-dimensional structure of the Kuroshio in the ocean area.

[0070] This method is applicable to sea areas where the influence of seabed terrain is not considered, can effectively improve the accuracy of Kuroshio structure identification, and has significant application value especially in the ocean area.

[0071] In the present invention, in step D, an auxiliary determination mechanism of removing the average value by introducing the combined flow velocity is adopted, and the specific steps are as follows:

[0072] Calculation of average flow velocity: For each latitude row, calculate the average value of the combined flow velocity along the depth direction , only considering valid flow velocity data (for example, excluding abnormal flow velocity values with an absolute value greater than 2 m / s);

[0073] Construction of velocity difference field: Calculate the velocity difference field after removing the average value, that is , generate a two-dimensional velocity difference distribution field of depth-longitude, and calculate the average depth of the velocity. The range can be defined according to the actual terrain of the study area;

[0074] Bottom boundary determination: By extracting the zero contour line in the velocity difference field, determine the lowest depth as the bottom boundary of the Kuroshio water body, and combined with gradient analysis, further verify the effectiveness of the boundary points;

[0075] Three-dimensional structure generation: Integrate the horizontal width and the bottom boundary to form the three-dimensional structure of the Kuroshio in the ocean area.

[0076] The innovation of this method lies in using the velocity difference field to enhance the significance of the Kuroshio bottom boundary, adapting to data resolution and flow field characteristics, avoiding the limitations of traditional methods affected by the environment, and lacking adaptability and flexibility. Embodiment

[0077] In this embodiment, the HYCOM (Hybrid Coordinate Ocean Model) reanalysis dataset is used to extract the three-dimensional structure of the Kuroshio. This dataset is provided by the US Naval Research Laboratory, with a spatial resolution of 1 / 12°×1 / 12° and a time resolution of 3 hours, covering the time range from 1993 to 2023. The data time selected in this embodiment is 2013, and the specific elements used include the meridional velocity , zonal velocity and depth data depth. The sea area range of the embodiment is the East China Sea area, with a longitude range from 124°E to 128°E and a latitude range from 26°N to 30°N. In addition, the ETOPO2022 seabed terrain data (resolution 15 arc seconds) is combined to assist in analyzing the terrain impact. The implementation process is described in detail in the following steps.

[0078] S10. Data preparation and velocity calculation.

[0079] S101. Load the ocean current field data, process the outliers in the velocity data, and regard the data with an absolute value greater than 2 m / s as outliers and set them to invalid values. Select a depth range of 0 to 1000 m (which can be set according to the actual sea area) to adapt to the typical water depth characteristics.

[0080] S102. Load the terrain data and generate the seabed depth distribution for subsequent terrain impact analysis.

[0081] S103. Calculate the resultant velocity of each depth layer , draw a two-dimensional velocity profile of depth-longitude, and the result is as Figure 2 shown: to verify the velocity characteristics of the Kuroshio.

[0082] S20. Flow velocity gradient calculation and horizontal gradient analysis.

[0083] S201. Calculate the horizontal gradient of the combined flow velocity along the longitude direction row by row (latitude) and layer by layer (depth), the zonal flow velocity gradient, and the meridional flow velocity gradient. Select typical depth layers (0, 100, 300, 400, 600, 800 m), and obtain the variation of the gradients of each layer in each row with longitude respectively. The results are as Figure 3 shown.

[0084] S202. Screen the effective gradient values, set the maximum and minimum gradient thresholds (which can be set according to the actual sea area. In the example, the maximum and minimum gradient thresholds are 3 and -2 respectively), and exclude the abnormal gradient values caused by the data itself.

[0085] S203. To highlight the inflection point characteristics, calculate the variation of the absolute value of the gradient of each layer in each row with the longitude value, as Figure 4 shown, indicating that the Kuroshio region should be between the two sides of the significantly high value points of the absolute value of the gradient.

[0086] S204. Select the first gradient maximum point in the gradient gentle interval - transition gradient acceleration interval and the first gradient minimum point in the gradient slowdown interval as candidate boundary points.

[0087] S205. Constrain the left - right (maximum gradient value point and minimum gradient value point) candidate boundary points through the longitude difference (set the constraint difference according to the Kuroshio width in different sea areas. In the example, it is set not to exceed 2°).

[0088] S206. Constrain the longitude continuity of the boundary points, and set the longitude difference between the candidate boundary points of the current depth layer and the previous depth layer to be less than 0.5° (which can be adjusted by the user according to the actual sea area).

[0089] S207. Screen the left - right boundary points (maximum gradient value point and minimum gradient value point) that satisfy the gradient difference greater than 2° as candidate boundary points.

[0090] S30. Based on the screening of constraint conditions, determine the three - dimensional structure of the Kuroshio without considering the influence of topography.

[0091] S301. Repeat the steps of S201 - S207 for each row until the final left - right horizontal boundary points of each layer in each row are determined.

[0092] S302. Determine whether the condition of S207 is satisfied. When a certain depth layer no longer meets the condition, it is determined as the bottom boundary depth of the Kuroshio in this latitude row.

[0093] S303. Integrate all the horizontal boundary points and bottom boundary points to complete the three-dimensional Kuroshio structure model in the ocean area without considering the influence of terrain. The result is presented as a three-dimensional scatter plot, as shown in Figure 6 as follows.

[0094] S40. Calculate and extract the velocity difference field.

[0095] S401. Assist in determining the bottom boundary, and calculate the average velocity of each cross-section point along the depth direction row by row (abnormal values with absolute value > 2 m / s are excluded). When in use, the average velocity calculation depth can be set according to the actual sea area terrain depth. In the example, a depth of 800 meters is adopted to generate the velocity difference field.

[0096] S402. Calculate the two-dimensional distribution of depth-longitude, and extract the 0 m / s contour line of the velocity difference field as the reference bottom boundary depth line. The result is shown in Figure 5 as follows. This result is only for display effect and is not the actual step of this embodiment.

[0097] S50. Based on the constraint conditions screening, realize the determination of the three-dimensional Kuroshio structure considering the influence of terrain.

[0098] S501. By extracting the zero contour line with a longitude span greater than 1° in the velocity difference field, determine the lowest depth it passes through as the candidate depth of the Kuroshio bottom boundary.

[0099] S502. For the complex seabed area, based on the velocity difference field, repeat the steps of S201 - S207 for each layer of each row to screen the boundary points and determine the horizontal width of the Kuroshio.

[0100] S503. If a certain depth layer does not meet the condition of S207 first (before reaching the candidate depth of the velocity difference field), then this depth layer is determined as the final depth of the Kuroshio bottom boundary for this latitude row.

[0101] S504. If the screening result of repeating the steps of S201 - S207 for a certain row reaches the candidate depth of the velocity difference field first, then it is determined as the final depth of the Kuroshio bottom boundary.

[0102] S505. Integrate all the horizontal boundary points and bottom boundary points to complete the three-dimensional Kuroshio structure model considering the influence of the nearshore or complex terrain. The result is presented as a three-dimensional scatter plot, as shown in Figure 7 as follows.

[0103] As described above, the present invention realizes the automatic identification of the horizontal width and bottom boundary of the Kuroshio through velocity gradient analysis, provides an intuitive basis for the extraction of the three-dimensional boundary structure of the Kuroshio, fully considers the boundary structures affected by terrain and without considering terrain, overcomes the limitations of the prior art, and realizes the automatic and real-time acquisition of the three-dimensional structure of the Kuroshio.

[0104] Those skilled in the art should be clear that the embodiments of the present invention can be embodied as methods, systems, or computer program products. Therefore, the present invention can be presented in the form of complete hardware implementation, complete software implementation, or a combination of hardware and software. At the same time, the present invention can also be implemented as a computer program product relying on a computer-readable storage medium (such as a hard disk, flash memory, optical disc, etc.).

[0105] The present invention is described through flowcharts and / or schematic diagrams of methods, devices (systems), and computer program products. Obviously, each step or module in the flowchart and schematic diagram can be implemented by computer program instructions. These instructions can be loaded onto the processor of a general-purpose computer, a special-purpose computer, an embedded processing device, or other programmable processing devices. By executing the instructions, the relevant devices can complete the functions defined in the flowchart or schematic diagram.

[0106] In summary, the present invention realizes the automatic identification of the horizontal width and bottom boundary of the Kuroshio through flow velocity gradient analysis. Combining two schemes with and without considering topography, it can flexibly meet the requirements of different ocean environments. Its main advantages include: strong real-time performance, capable of quickly generating results based on multi-temporal data, reducing the need for a large amount of computational processing, and avoiding the negative impact of traditional methods relying on multi-year averages on real-time performance; objective and highly flexible, able to define execution conditions according to the characteristics of the Kuroshio in different sea areas, avoiding problems limited to the surface layer or fixed identification depths; both accurate and complete, suitable for multi-source data processing; highly adaptable, capable of dynamically adjusting to datasets of different resolutions. Finally, the present invention intuitively presents the Kuroshio structure through three-dimensional visualization means, realizes the automatic extraction of the real-time dynamic three-dimensional structure of the Kuroshio, and provides an effective technical means for further ocean dynamics research and Kuroshio monitoring.

[0107] As mentioned above, the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for automatically identifying the three-dimensional structure of the Kuroshio based on the velocity gradient, characterized in that, It includes the following steps: A. Calculate the horizontal width of the Kuroshio based on the velocity gradient: First, extract the meridional velocity and zonal velocity of the sea area to be measured from the ocean current field data, and then calculate the full-field velocity data of the flow field to obtain the full-field velocity distribution of the flow field; After that, calculate the velocity partial derivative of each latitude row along the longitude direction, and use the inflection point characteristics of the partial derivative to identify the horizontal width of the Kuroshio; B. Determine the bottom boundary of the Kuroshio water body based on depth screening: Screen the velocity partial derivative results of each depth layer to determine the bottom boundary depth of the Kuroshio water body; C. Identify the three-dimensional structure of the Kuroshio in the ocean area without considering the terrain; D. Identify the three-dimensional structure of the Kuroshio considering the terrain influence; The specific process of step A is as follows: Flow velocity data extraction and calculation: Obtain the meridional flow velocity of the sea area to be measured from the input data and the zonal flow velocity , calculate the resultant flow velocity , providing basic data for subsequent gradient analysis; Principle of row-by-row partial derivative calculation and analysis: For each latitude row, the partial derivative of the combined flow velocity is calculated along the longitude direction to obtain the horizontal gradient and is identified by analyzing the changing trend of ; Inflection point recognition: By analyzing the inflection points, maximum gradient value, and minimum gradient value of the gradient as candidate points for the left and right boundaries of the Kuroshio, and then determining the positions of the left and right boundaries of the Kuroshio, that is, the horizontal width. ​ The identification of the horizontal width of the Kuroshio is divided into the following three stages: ① Entering the Kuroshio boundary stage, not yet in the Kuroshio region: When gradually increases and reaches the maximum value, it indicates that the rate of increase in the flow velocity along the longitude direction is getting faster and faster; ②Internal processes of the Kuroshio: When Although it is still greater than 0 but starts to decrease, the flow velocity is still increasing, but the rate of increase gradually slows down. Subsequently, it decreases to 0 or even becomes negative, indicating that the trend of increasing flow velocity disappears and even starts to reverse; ③Stage of leaving the Kuroshio region: When reaches the minimum value and then starts to rise but is still negative, it indicates that the flow velocity is still decreasing, but the rate of decrease is gradually slowing down; The said step B includes the following process: Deep layer velocity analysis: Extract velocity data layer by layer along the depth direction, and calculate the horizontal gradient within the specified latitude row for each depth layer ; Boundary determination conditions: Apply screening conditions to the gradient results of each depth layer, including the gradient value range, the gradient difference greater than 2°, and the longitude continuity constraint of the boundary points. When a certain depth layer no longer meets the conditions, it is determined as the bottom boundary of the Kuroshio; Result integration: Summarize the bottom boundary depths of each latitude row to form the three-dimensional structure contour of the Kuroshio; The specific process of the said step C is as follows: Terrain data integration: Combine external terrain data. Since the Kuroshio phenomenon is located in the upper ocean, the analysis depth range can be limited to avoid the interference of terrain occlusion on the velocity calculation; Gradient calculation and boundary extraction: Calculate the velocity gradient along each latitude row within the specified depth range, and determine the horizontal width and bottom boundary of the Kuroshio through the inflection point identification and depth screening methods; Three-dimensional structure generation: Integrate the horizontal width and the bottom boundary to form the three-dimensional structure of the Kuroshio in the ocean area; In the said step D, an auxiliary determination mechanism of removing the average value by introducing the combined velocity is adopted, and the specific steps are as follows: Calculation of average flow velocity: For each latitude row, calculate the average of the resultant flow velocities in the depth direction, considering only the valid flow velocity data. , considering only the valid flow velocity data. Construction of velocity difference field: Calculate the velocity difference field after removing the average value, that is , generate a two-dimensional velocity difference distribution field of depth-longitude, and the average depth of the velocity can be defined according to the actual terrain of the study area; Bottom boundary determination: Determine the lowest depth as the bottom boundary of the Kuroshio water body by extracting the zero isocline in the velocity difference field; Three-dimensional structure generation: Integrate the horizontal width and the bottom boundary to form the three-dimensional structure of the Kuroshio in the ocean area.

Images