Method for automatically identifying black tide axis by using ocean surface velocity and ocean surface height

Abstract

The invention provides a method for automatically identifying a black tidal current axis by utilizing ocean surface flow velocity and ocean surface height, which comprises the following steps of: firstly, acquiring ocean surface warp-wise and weft-wise flow velocity to calculate a full flow field, and acquiring a maximum velocity reference line through forward, reverse and bidirectional velocity extremum methods; then, sea surface height measurement data are utilized, a mode value is calculated through data processing, and a sea surface reference isoline is generated; then calculating the minimum difference degree between the maximum speed reference line and each reference contour line to determine a target reference contour line; and finally, correcting the target reference contour line by using the speed extremum method to obtain the black and moist principal axis. The method effectively solves the problem that a classical speed extreme value method is influenced by vortex, can adapt to multi-source and multi-temporal data, realizes automatic extraction of a real-time dynamic black tide axis, improves the accuracy and integrity of black tide axis identification, and has important significance in research of black tide paths and flow change rules.

Description

Technical Field

[0001] The invention relates to the technical field of marine environment monitoring and data analysis, and in particular to a method for automatically identifying a black current axis by utilizing ocean surface velocity and sea surface height. Background Art

[0002] The Kuroshio is a strong warm current at the western border of the North Pacific Ocean. The Kuroshio has the characteristics of high water temperature, high salinity and fast flow, which has a profound impact on the surrounding marine environment, climate and biodiversity. The identification of the Kuroshio current axis is an important topic in marine research. Currently, three main methods are used: based on ocean currents or streamlines, based on isotherms and based on absolute dynamic height (ADT). Although these methods provide certain effectiveness in practical applications, their respective shortcomings are also obvious.

[0003] First, the identification method based on ocean currents or streamlines relies on the significant velocity characteristics of the Kuroshio as a strong western boundary current, which is intuitive and rapid. However, this method is easily disturbed by the surrounding vortices in complex flow fields, thus affecting the accurate identification of the flow axis. In addition, the instantaneous change of flow velocity may lead to the instability of the flow axis position, limiting its application in dynamic marine environments; secondly, the identification method based on isotherms is widely used due to the high temperature characteristics of the Kuroshio, but its selection criteria are somewhat subjective and usually need to be adjusted according to different sea areas and seasons. Especially when using daily data, the complexity of the marine environment affects the reliability of the flow axis, making the accuracy of automatic identification questionable; finally, the identification method based on absolute dynamic height combines sea level anomalies and average dynamic terrain data, which can provide more comprehensive flow field information. However, the sea surface height values ​​of data sets from different versions and sources are inconsistent, and they are all analyzed after averaging for many years, which is difficult to adapt to the dynamic and real-time changes in the flow of the Kuroshio, affecting the stability and accuracy of flow axis identification and increasing the complexity of application.

[0004] In summary, although the existing methods have certain advantages in identifying the axis of the Kuroshio Current, they generally face challenges such as subjectivity, complexity and lack of accuracy. Therefore, the present invention provides an innovative comprehensive identification method, which aims to overcome the limitations of the existing technology and improve the accuracy and completeness of the identification of the Kuroshio Current axis while realizing the automatic confirmation of the main axis of the Kuroshio Current. Summary of the invention

[0005] The present invention provides a method for automatically identifying the black current axis by using the ocean surface velocity and the sea surface height, so as to solve the problems of low accuracy, poor real-time performance and insufficient adaptability existing in the prior art, and realize automatic and high-precision identification of the black current axis.

[0006] The present invention provides a method for automatically identifying the black current axis by using the ocean surface velocity and the sea surface height, comprising the following steps: Step 1: Obtain data and calculate the full-field flow field; Step 2: Use the velocity extreme value method to obtain the maximum velocity reference line; Step 3: Calculate and identify the sea surface reference contour line; Step 4: Determine the target reference contour line; Step 5: Modify the target reference contour line to obtain the Kuroshio main axis.

[0007] Preferably, in the above Step 1, obtain the meridional velocity u and zonal velocity v of the sea surface of the sea area to be detected from satellite observations or numerical model data, and calculate the full-field flow velocity data V through vector synthesis. The formula is to obtain the full-field flow velocity and flow direction.

[0008] Preferably, in the above Step 2, it includes the forward velocity extreme value method and the reverse velocity extreme value method. Among them, the forward velocity extreme value method is specifically as follows: Select a representative point as the first fixed point; construct an auxiliary line along the vertical direction of the fixed point's flow direction, and calculate the average flow direction for all grid points on the auxiliary line; the fixed point constructs a new auxiliary line along the vertical direction of the average flow direction, and find the grid point with the maximum velocity on the new auxiliary line, which is defined as the maximum velocity reference point; this reference point moves forward along the average flow direction, and the forward distance is set according to the data resolution, set as d , move to the next fixed point, and repeat the above steps until the fixed point reaches the longitude or latitude boundary line of the sea area to be detected, and connect all the maximum flow velocity points to form the forward maximum velocity reference line; The reverse velocity extreme value method is specifically as follows: Multiply the full-field flow velocity by -1 to obtain the reverse flow field; start from the given reverse starting point and perform the same operations as the forward velocity extreme value method to obtain the reverse maximum velocity reference line; if the reverse velocity extreme value method fails to successfully determine the maximum velocity reference line, then turn to the forward velocity extreme value method; after completing the analysis of the reverse and forward velocity extreme value methods, use the two-way method to reasonably splice the results of the two to finally determine the maximum velocity reference line segment of the sea area to be detected.

[0009] Preferably, the above Step 3 is specifically as follows: Obtain the sea surface altimetry data of the sea area to be detected from the used data, draw the sea surface altimetry contour lines of the entire sea area to be detected, and based on the obtained maximum velocity reference line, perform the calculation and identification of the sea surface reference contour line. The specific calculation method is as follows: Data preprocessing: Statistically classify the sea surface coronagraph height values of all points on the maximum velocity reference line; to improve the accuracy of statistics, multiply the sea surface height by ; ensuring that in the subsequent statistical process, all height values are on the same scale, reducing the error caused by numerical differences, and thus improving the data consistency;

[0010] Among them, is the original sea surface height value, is the required number of decimal places; Floor function: The magnified sea surface height value is floored to obtain an integer value;

[0011] Restore the original number of digits: The floored height value is divided by 10 to restore the original number of digits, ensuring the true expression of the data and avoiding information loss caused by numerical scaling;

[0012] Mode value calculation: Based on the obtained height value, the mode value on the maximum speed reference line is statistically calculated; this mode value is the sea surface altimetry reference isocontour value, and then this mode value is added to and subtracted from the interval value of the adjacent isocontours, thereby generating three sea surface altimetry reference isocontours.

[0013] Preferably, in step four, by calculating the distance between the sea surface altimetry isocontour and the straight line of the maximum speed reference line, the reference isocontour closest to it is found; the minimum difference degree calculation process is divided into the following steps: Data preparation: The longitude and latitude points of the maximum speed reference line and the corresponding path points on different reference isocontours; Define the longitude range: Set the optimal and required longitude range for filtering valid maximum speed reference line points and reference isocontour points; Calculate the minimum difference degree: For each valid isocontour point of each sea surface altimetry reference isocontour in turn, calculate its minimum distance to the maximum speed reference line, and the distance calculation formula is:

[0014] where, is the longitude and latitude of the current isocontour point, is the point on the maximum speed reference line; Calculate the average difference degree: For each isocontour in turn, accumulate the minimum distances of all its valid isocontour points to the maximum speed reference line to obtain the total difference degree, and calculate the average difference degree: Obtain the target reference isocontour: Compare the average difference degrees of each reference isocontour, and the reference isocontour with the smallest average difference degree is the target reference isocontour.

[0015] Preferably, in step five, the velocity extreme value method is used again to correct the target reference isocontour to obtain the Kuroshio main axis, and the specific correction process is as follows: Data preparation: Identify and obtain the longitude, latitude positions, combined flow velocity, flow direction information, and sea surface altimetry data information of all points on the target reference isoline. Interpolation calculation: For each point on the target isoline, construct an auxiliary line vertically along the flow direction at that point, and interpolate and calculate the flow velocity magnitude at that position at intervals. The distance range is defined according to the actual resolution of the data used. Finding the maximum flow velocity points: For each auxiliary line, find the point with the maximum flow velocity on that line, which is defined as the point on the main axis of the Kuroshio. Correcting the main axis: Gather all the maximum flow velocity points. These points represent the path of the Kuroshio axis under the maximum flow velocity condition. Connect them into a line and smooth it to complete the correction. Advantageous effects: The present invention calculates and generates the maximum velocity reference line through the velocity extreme value method in multiple directions, ensuring the maximum flow velocity characteristic of the Kuroshio axis. At the same time, by using sea surface altimetry data to screen the reference isoline and adopting geometric distance and interpolation calculation methods, it effectively overcomes the limitations of the traditional isoline method and greatly improves the accuracy and reliability of the identification of the Kuroshio flow path.

[0016] The present invention can adapt to different observation data and model data sets, directly obtain the real-time Kuroshio axis morphology based on the time resolution of the data used, realize the automatic extraction of the real-time dynamic Kuroshio main axis, no longer rely on long-term observation averages to obtain the reference isoline, reduce the need for a large amount of computational processing, and avoid the negative impact of multi-year averages on the real-time presentation of the flow axis.

[0017] The present invention is applicable to various multi-source and multi-temporal satellite observation data and numerical model data, effectively solves the deviation and interruption problems that may be caused by the classical velocity extreme value method under the influence of vortices, and ensures that the identified Kuroshio main axis points are all the maximum velocity points in the sea area to be measured.

[0018] The above description is only an overview of the technical solutions of the embodiments of the present invention. In order to be able to understand the technical means of the embodiments of the present invention more clearly, it can be implemented according to the content of the description. And in order to make the above and other purposes, features, and advantages of the embodiments of the present invention more obvious and understandable, the following specifically describes the embodiments of the present invention. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a flow chart of the velocity extreme value method applied in the present invention. Figure 2 This is the overall flowchart of the present invention. Detailed implementation manners

[0021] 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 belong to the scope of protection of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs; the terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" and any variations thereof in the specification and claims of this invention and the drawings are intended to cover non-exclusive inclusion.

[0023] 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.

[0024] To enable those skilled in the technical field 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.

[0025] As Figure 1 - Figure 2 shown, the present invention discloses a method for automatically identifying the Kuroshio axis using ocean surface velocity and sea surface height, including the following steps: Step 1: Obtain data and calculate the full-field flow field; Step 2: Use the velocity extreme value method to obtain the maximum velocity reference line; Step 3: Calculate and identify the sea surface reference contour line; Step 4: Determine the target reference contour line; Step 5: Correct the target reference contour line to obtain the Kuroshio main axis.

[0026] In step 1 of the present invention, the ocean surface meridional velocity u and zonal velocity v of the sea area to be detected are obtained from satellite observations or numerical model data, and the full-field flow velocity data V, the formula is , and then the flow velocity and direction of the whole field are obtained.

[0027] In the second step of the present invention, it includes the forward velocity extreme value method and the reverse velocity extreme value method. Among them, the forward velocity extreme value method is specifically as follows: Select a representative point as the first fixed point; Construct an auxiliary line along the vertical direction of the fixed point's flow direction, and calculate the average flow direction for all grid points on the auxiliary line; The fixed point constructs a new auxiliary line along the vertical direction of the average flow direction, and finds the grid point with the maximum velocity on the new auxiliary line, which is defined as the maximum velocity reference point; The reference point advances along the average flow direction, and the advancing distance is set by itself according to the data resolution, and is set to d , move to the next fixed point, repeat the above steps until the fixed point reaches the longitude or latitude boundary line of the sea area to be measured, and connect all the maximum flow velocity points to form a forward maximum velocity reference line; The reverse velocity extreme value method is specifically as follows: Multiply the flow velocity of the whole field by -1 to obtain a reverse flow field; Starting from the given reverse starting point, perform the same operations as the forward velocity extreme value method to obtain a reverse maximum velocity reference line; If the reverse velocity extreme value method fails to successfully determine the maximum velocity reference line, then turn to the forward velocity extreme value method; After completing the analysis of the reverse and forward velocity extreme value methods, use the two-way method to reasonably splice the results of the two, and finally determine the maximum velocity reference line segment of the sea area to be measured.

[0028] Since the flow field may be disturbed by surrounding vortices, if the reverse velocity extreme value method fails to successfully determine the maximum velocity reference line, then it will turn to the forward velocity extreme value method. In this process, the same operations are performed using the given forward starting point to extract the forward maximum velocity reference line. Combining the forward and reverse velocity extreme value methods can significantly improve the success rate of extracting the maximum velocity reference line.

[0029] The third step of the present invention is specifically as follows: Obtain the sea surface altimetry data of the sea area to be measured from the data used, draw the sea surface altimetry contour lines of the whole sea area to be measured, and based on the obtained maximum velocity reference line, perform the calculation and identification of the sea surface reference contour lines. The specific calculation method is as follows: Data preprocessing: Statistically classify the sea surface coronation height values of all points on the maximum velocity reference line; To improve the accuracy of statistics, multiply the sea surface height uniformly by ; Ensure that in the subsequent statistical process, all height values are at the same scale, reduce the error caused by numerical differences, and thus improve the data consistency;

[0030] Among them, is the original sea surface height value, is the required number of decimal places; Floor function: Take the floor of the magnified sea surface height value to obtain an integer value; Restore the original number of digits: Divide the rounded height value by 10 to restore the original number of digits, ensuring the true expression of the data and avoiding information loss caused by numerical scaling;

[0031] Mode value calculation: Based on the obtained height values, count the mode values on the maximum speed reference line; this mode value is the sea surface altimetry reference contour value, and then add and subtract this mode value from the interval value of adjacent contours to generate three sea surface altimetry reference contour lines.

[0032] Specific steps are exemplified as follows: ① When the z values are 0.8934, 0.8734, 0.8265, 0.9875, etc., magnify the data by 10 times to get 8.934, 8.734, 8.265, 9.875; ② Then perform rounding to obtain the values of 9, 9, 8, 10; ③ Then'shrink' it by 10 times, that is, obtain the corresponding contour values with decimal places of 0.9m, 0.9m, 0.8m, 1.0m; ④ Then calculate the mode value based on the obtained values.

[0033] This mode value is the sea surface altimetry reference contour value, and then add and subtract this mode value from the interval value of adjacent contours to generate three sea surface altimetry reference contour lines. This method is of great significance, can dynamically adapt to the resolution and data accuracy of different data sources, and automatically extract the contour line group that can be used as a reference for any sea area to be measured. Counting the mode value on the maximum speed reference line provides a key reference point for subsequent analysis. As the value with the highest frequency of occurrence in the data set, the mode can effectively represent the typical sea surface height characteristics in this maximum speed area, laying a solid foundation for obtaining the continuous and maximum speed main flow axis.

[0034] In step four of the present invention, by calculating the distance between the sea surface altimetry contour line and the straight line of the maximum speed reference line, the reference contour line closest to it is found; the minimum difference calculation process is divided into the following steps: Data preparation: The longitude and latitude points of the maximum speed reference line and the corresponding path points on different reference contour lines; Define the longitude range: Set the optimal longitude range to be calculated, which is used to filter the valid maximum speed reference line points and reference contour line points; Calculate the minimum difference: For each valid contour line point of each sea surface altimetry reference contour line in turn, calculate its minimum distance to the maximum speed reference line, and the distance calculation formula is: Among them, is the longitude and latitude of the current contour point, is a point on the maximum speed reference line; Calculate the average difference degree: For each contour line in turn, accumulate the minimum distances from all its valid contour points to the maximum speed reference line to obtain the total difference degree, and calculate the average difference degree: Obtain the target reference contour line: Compare the average difference degrees of each reference contour line. The reference contour line with the smallest average difference degree is the target reference contour line.

[0035] It not only improves the utilization efficiency of sea surface altimetry data, but also further enhances the accuracy of selecting reference contour lines, and improves the recognition accuracy of the Kuroshio main axis. By calculating the difference degree from the target reference contour line, this method can adaptively adjust the position of the flow axis, provide a more accurate Kuroshio flow path, and provide an important basis for the subsequent determination of the Kuroshio main axis.

[0036] In the fifth step of the present invention, the speed extreme value method is used again to correct the target reference contour line to obtain the Kuroshio main axis. The specific correction process is as follows: Data preparation: Identify and obtain the longitude and latitude positions, combined flow velocity, flow direction information, and sea surface altimetry data information of all points on the target reference contour line; Interpolation calculation: For each point on the target contour line, construct an auxiliary line vertically along the flow direction at this point, and interpolate and calculate the flow velocity magnitude at this position at intervals. The distance range is defined according to the actual resolution of the data used; Find the maximum flow velocity point: For each auxiliary line, find the point with the maximum flow velocity on this line, which is defined as the point on the Kuroshio main axis; Correct the main axis: Gather all the maximum flow velocity points. These points represent the Kuroshio flow axis path under the maximum flow velocity condition. Connect them into a line and smooth it to complete the correction.

[0037] By using the speed extreme value method to find the highest flow velocity point near specific contour points, the main axis of the Kuroshio can be depicted more accurately, ensuring that the flow field characteristics are accurately reflected in a complex flow field environment. Embodiment

[0038] In this embodiment, satellite altimeter sea surface current field data and satellite remote sensing AVSIO absolute dynamic topography (ADT) are used to extract the axis of the Kuroshio surface current. This data is provided by the French Satellite Ocean Archive Data Center and is a delayed daily sea surface product released by the Copernicus Marine Environment Monitoring Center. The data integrates the observation data of ERS-1 / 2, Envisat, Topex / Poseidon and its subsequent satellites Jason-1 / 2. Its spatial resolution is 1 / 4°×1 / 4°, the time resolution is daily, and the time range is from 1993 to November 2023. The specific elements used include ADT data and geostrophic velocity data (meridional velocity , zonal velocity ) derived from ADT through geostrophic balance. The sea area range of the embodiment is 24.375°-30.875°N, 121.625°-130.625°E.

[0039] S101. Calculate the sea surface height contour lines of the entire implementation sea area using ADT data, with a contour interval of 0.1 meters, to form an ADT sea surface height contour map.

[0040] S102. Calculate the flow velocity and flow direction results of the entire implementation sea area using geostrophic velocity data, , , to form a full-field flow field map.

[0041] S20. Based on the flow velocity and flow direction results of the entire implementation sea area, use the velocity extreme value method in multiple directions to calculate the maximum velocity reference line.

[0042] S201. Flow velocity reverse processing: First, multiply the full-field flow velocity by -1. The magnitude of the flow velocity in the reverse flow field is not affected, and the path recognition from north to south can effectively reduce the problem of flow field bifurcation caused by vortices. Using the reverse velocity extreme value method, starting from the given reverse starting point, construct a 200 km auxiliary line (100 km on each side of the fixed point) along the vertical direction of the fixed-point flow direction, and calculate the average flow direction for all grid points on this auxiliary line. The length of the auxiliary line can be defined according to the specific situation of the research area and the data used.

[0043] S202. Construct a new 100 km auxiliary line (50 km on each side of the fixed point) along the vertical direction of the average flow direction at the fixed point.

[0044] S203. Identify all grid points passed on the new auxiliary line, read out the data information at the grid points, and judge to find the grid point with the maximum flow velocity on the new auxiliary line, which is recorded as the maximum velocity reference point.

[0045] S204. Move forward 30 km (which can be set according to the data resolution) along the average flow direction from the obtained maximum velocity reference point to the next fixed point.

[0046] S205. Repeat steps S202 - S205 until the fixed point reaches the longitude or latitude boundary line of the implementation sea area, and finally identify all the maximum velocity points, and connect these points to form a reverse maximum velocity reference line.

[0047] If the reverse velocity extreme value method fails due to the influence of vortices.

[0048] S206. Forward processing of the steering velocity: In this process, the same operation is performed using the given forward starting point to extract the forward maximum velocity reference line. Combining the forward and reverse velocity extreme value methods can significantly improve the success rate of extracting the maximum velocity reference line.

[0049] In the sea area of this embodiment and the data results used, only by combining the reverse and forward velocity extreme value methods can the maximum velocity reference line of each day be successfully confirmed. Therefore, to show the form of the bidirectional velocity extreme value method, the data used is specifically replaced with the numerical mode data HYCOM (Hybrid Coordinate Ocean Model) reanalysis dataset, which has a spatial resolution of 1 / 12°×1 / 12° and a time resolution of 3 hours.

[0050] S30. Based on the obtained maximum velocity reference line, calculate and identify the sea surface reference contour line.

[0051] S301. Identify the ADT values of all grid points on the maximum velocity reference line and perform statistical classification. To improve the accuracy of classification, multiply all ADT values by 10 (if the contour interval needs to be accurate to two decimal places, multiply by 100, and multiply by the corresponding multiple accordingly).

[0052] S302. Round down the amplified ADT values to obtain their integer values.

[0053] S303. Divide the rounded height values by 10 to restore the original number of digits.

[0054] S304. Based on the obtained height values, statistically calculate the mode value on the maximum velocity reference line.

[0055] Through the classification and statistics of this series of steps, in the process of calculating and identifying the ADT reference contour line around the maximum velocity line, the accuracy of classification can be effectively improved and the data processing can be simplified.

[0056] S305. If the mode value is 1.0, then add and subtract the contour interval value of 0.1 from the value 1.0 to generate three sea surface altimetry reference contour lines, which are generated as 0.9 m, 1.0 m, and 1.1 m reference contour lines.

[0057] S40. Calculate the minimum difference degree between the maximum velocity reference line and each ADT reference contour line to obtain the target reference contour line.

[0058] S401. Read out the position information of each point on the maximum speed reference line and the ADT reference isoline.

[0059] S402. Set the calculated longitude range, and filter out the position information of each point on each line within the corresponding longitude range to maximize the matching degree between the accurate maximum speed and the ADT isoline. If it is a reverse maximum speed reference line, the longitude range is 127.875°E - 130.125°E; if it is a forward maximum speed reference line, the longitude range is 121.875°E - 124.125°E; if it is a two-way maximum speed reference line, the accuracy ranges are 127.875°E - 130.125°E and 121.875°E - 124.125°E.

[0060] S403. Within the corresponding longitude range, each point on the maximum speed reference line is successively compared with each valid isoline point on each ADT reference isoline to calculate the minimum distance from the maximum speed point to the isoline. The distance calculation formula is: S404. Accumulate the minimum distances from the valid points on each isoline to the maximum speed reference line to obtain the total difference degree, and then calculate the average difference degree of each isoline. The calculation formula is: .

[0061] S405. Compare the average difference degrees of each isoline. The ADT isoline with the minimum average difference degree is regarded as the target ADT reference isoline.

[0062] Through the calculation of the minimum difference degree, the accuracy of the selection of the reference isoline is further enhanced, and the recognition accuracy of the Kuroshio main axis is improved.

[0063] S50. Use the velocity extreme value method again to correct the target ADT reference isoline to obtain the Kuroshio main axis.

[0064] S501. Identify the longitude and latitude positions, combined flow velocity, flow direction information, and sea surface altimetry data information of all points on the target ADT reference isoline.

[0065] S502. For each point on the target isoline, construct a 60 km auxiliary line (30 km on each side) vertically along its flow direction, and interpolate and calculate the flow velocity magnitude every 3 km.

[0066] S503. For each auxiliary line in turn, find the point with the maximum flow velocity on the current auxiliary line, and replace each point on the original target ADT reference isoline with the point with the maximum flow velocity on its corresponding auxiliary line to obtain the points on the Kuroshio main axis.

[0067] S504. Gather all the maximum flow velocity points and connect them into a line to complete the correction.

[0068] S505. After smoothing by a moving average with a window size of 3, the final main axis of the Kuroshio is obtained.

[0069] As described above, the method for automatically comprehensively identifying and determining the main axis of the Kuroshio surface layer assisted by sea surface altimetry data proposed by the present invention can ensure the maximum flow velocity characteristic of the Kuroshio axis to the greatest extent, thus overcoming the limitations of the traditional contour method.

[0070] In summary, the present invention calculates and generates a maximum velocity reference line through the velocity extreme value method in multiple directions, ensuring the maximum flow velocity characteristic of the Kuroshio axis. At the same time, by using sea surface altimetry data to screen the reference contour lines and adopting geometric distance and interpolation calculation methods, the limitations of the traditional contour method are effectively overcome, and the accuracy and reliability of the Kuroshio flow path identification are greatly improved.

[0071] The present invention can adapt to different observation data and model data sets, directly obtain the real-time morphology of the Kuroshio axis based on the time resolution of the used data, realize the automatic extraction of the real-time dynamic main axis of the Kuroshio, no longer rely on long-term observation averages to obtain reference contour lines, reduce the need for a large amount of computational processing, and avoid the negative impact of multi-year averages on the real-time presentation of the convection axis.

[0072] The present invention can be applied to various multi-source and multi-temporal satellite observation data and numerical model data, effectively solving the problems of deviation and interruption that may be caused by the classical velocity extreme value method under the influence of vortices, and ensuring that the identified Kuroshio main axis points are all the maximum velocity points in the sea area to be measured.

[0073] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than 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 on 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 Kuroshio current axis using ocean surface velocity and sea surface height, characterized in that: The steps include: Step 1: Obtain data and calculate the full-field flow field; Step 2: Use the speed extreme value method to obtain the maximum speed reference line; Step 3: Calculate and identify sea surface reference contours; Step 4: Determine the target reference contour; Step 5: Correct the target reference contour to obtain the main axis of the Kuroshio.

2. The method for automatically identifying the Kuroshio Current axis using ocean surface velocity and sea surface height according to claim 1, characterized in that: In the step 1, the sea surface meridional current velocity of the sea area to be detected is obtained from satellite observations or numerical model data. u , latitudinal velocity v , calculate the flow velocity data of the whole occasion through vector synthesis V , the formula is , and then obtain the flow velocity and direction of the whole field.

3. The method for automatically identifying the Kuroshio Current axis using ocean surface velocity and sea surface height according to claim 1, characterized in that: The step 2 includes the forward velocity extreme value method and the reverse velocity extreme value method, wherein the forward velocity extreme value method is specifically as follows: select a representative point as the first fixed point; construct an auxiliary line vertically along the fixed point flow direction, and calculate the average flow direction for all grid points on the auxiliary line; construct a new auxiliary line vertically based on the average flow direction, find the maximum velocity grid point on the new auxiliary line, and define it as the maximum velocity reference point; the reference point moves forward along the average flow direction, and the forward distance is set according to the data resolution, which is set as d , move to the next fixed point, repeat the above steps until the fixed point reaches the longitude or latitude boundary line of the sea area to be measured, and connect all the maximum flow velocity points to form a positive maximum velocity reference line; The reverse velocity extreme value method is as follows: multiply the full-field velocity by -1 to obtain the reverse flow field; starting from a given reverse starting point, perform the same operation as the forward velocity extreme value method to obtain the reverse maximum velocity reference line; if the reverse velocity extreme value method fails to successfully determine the maximum velocity reference line, turn to the forward velocity extreme value method; after completing the analysis of the reverse and forward velocity extreme value methods, use the bidirectional method to reasonably "splice" the results of the two, and finally determine the maximum velocity reference line segment of the sea area to be tested.

4. The method for automatically identifying the Kuroshio Current axis using ocean surface velocity and sea surface height according to claim 1, characterized in that: The step three is specifically as follows: obtaining the sea surface height measurement data of the sea area to be measured from the used data, drawing the sea surface height measurement contour lines of the entire sea area to be measured, and calculating and identifying the sea surface reference contour lines based on the obtained maximum speed reference lines. The calculation method is as follows: Data preprocessing: Statistical classification of the sea surface height values ​​at all points on the maximum speed reference line; to improve the accuracy of statistics, the sea surface height is uniformly multiplied by ; This ensures that all height values ​​are on the same scale in the subsequent statistical process, reducing the error caused by numerical differences and thus improving the consistency of the data; in, is the original sea surface height, is the required number of decimal places; Round down: round down the amplified sea surface height value to get an integer value; Restore the original number of digits: Divide the rounded height value by 10 to restore the original number of digits, ensuring the true expression of the data and avoiding information loss caused by numerical scaling; Mode value calculation: Based on the obtained height value, the mode value on the maximum speed reference line is counted; the mode value is the sea surface height reference contour value, and then the mode value is added and subtracted from the interval value of the adjacent contour line to generate three sea surface height reference contour lines.

5. The method for automatically identifying the Kuroshio Current axis using ocean surface velocity and sea surface height according to claim 1, characterized in that: In the step 4, the distance between the sea surface height contour line and the maximum speed reference line is calculated to find the closest reference contour line; the minimum difference calculation process is divided into the following steps: Data preparation: longitude and latitude points of the maximum speed reference line and corresponding path points on different reference contour lines; Define longitude range: Set the optimal longitude range that needs to be calculated to filter the valid maximum speed reference line points and reference contour points; Calculate the minimum difference: For each valid contour point of each sea surface height reference contour line, calculate the minimum distance to the maximum speed reference line. The distance calculation formula is: in, is the latitude and longitude of the current contour point, is the point on the maximum speed reference line; Calculate the average difference: For each contour line, add up the minimum distances from all valid contour line points to the maximum speed reference line to obtain the total difference, and calculate the average difference: Obtain the target reference contour line: compare the average difference of each reference contour line, and the reference contour line with the smallest average difference is the target reference contour line.

6. The method for automatically identifying the Kuroshio Current axis using ocean surface velocity and sea surface height according to claim 1, characterized in that: In step 5, the velocity extreme value method is used again to correct the target reference contour to obtain the main axis of the Kuroshio. The specific correction process is as follows: Data preparation: Identify and obtain the latitude and longitude positions, combined flow velocity, flow direction information and sea surface height measurement data of all points on the target reference contour line; Interpolation calculation: For each point on the target contour line, construct auxiliary lines vertically along the flow direction at that point, and calculate the flow velocity at that location by interpolation at intervals. The distance range is defined by the actual resolution of the data used. Find the point with the maximum velocity: For each auxiliary line, find the point with the maximum velocity on the line, which is defined as the point on the main axis of the Kuroshio Current; Correction of the main axis: Gather all the maximum flow rate points, which represent the black current axis path under the maximum flow rate conditions, and connect them into a smooth line to complete the correction.

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