A method and apparatus for locating the position of a tropical cyclone using a wind field

Abstract

The application relates to a method for positioning the position of a tropical cyclone by using a wind field, comprising the following steps: obtaining a given wind field, determining the basic attributes of the wind field; performing orthogonal decomposition on the wind field to obtain a zonal wind and a meridional wind; calculating the closed rotation center of the wind field based on the zonal wind and the meridional wind; performing pretreatment on the closed rotation center to obtain a processed closed rotation center; calculating the range of the tropical cyclone based on the processed closed rotation center to obtain a rectangular area corresponding to the east-west-south-north four-direction boundary of different tropical cyclones; performing unreasonable area elimination on the rectangular area according to the maximum wind speed and the range size to obtain a final tropical cyclone. The application can quickly and accurately identify the positions of multiple tropical cyclones in the wind field without relying on the pressure field, satellite inversion brightness temperature products and artificial pre-judgment positioning assistance, and can determine the position of the tropical cyclone while obtaining related tropical cyclone information including the range, intensity and wind circle radius of the tropical cyclone.

Description

Technical Field

[0001] This invention relates to the field of weather forecasting technology, and in particular to a method and apparatus for locating tropical cyclones using wind fields. Background Technology

[0002] Tropical cyclones are a general term for non-frontal synoptic-scale vortices that form over tropical or subtropical oceans, exhibiting organized convection and a defined cyclonic circulation. Tropical cyclones are conventionally called by different names in different regions, such as typhoons, hurricanes, and cyclonic storms. Based on intensity, they can be classified as tropical depressions, tropical storms, severe tropical storms, typhoons, severe typhoons, and super typhoons. The development of a tropical disturbance into a tropical cyclone is significantly marked by the establishment of a closed low-level circulation center.

[0003] Observing and locating tropical cyclones has always been a significant challenge. Because tropical cyclones primarily operate over the ocean, most land-based weather stations cannot provide real-time data. Currently, monitoring relies mainly on artificial Earth satellites, supplemented by products such as numerical weather prediction.

[0004] Currently, typhoon location solutions are mainly divided into three categories.

[0005] The first category of methods is typhoon center location methods based on satellite cloud image products, such as the Dvorak tropical cyclone location and intensity determination method and the "A Typhoon Center Location Method Based on Infrared Satellite Cloud Image" (CN112686254B). These methods mainly use various image recognition algorithms to locate the typhoon and identify the characteristics of the typhoon's eye. Location methods based on satellite cloud image products are mainly suitable for locating strong typhoons with a clear eye, whose eye characteristics are relatively obvious. However, for weak typhoons and asymmetrical typhoons, the location error is relatively large because it is difficult to identify the eye structure.

[0006] The second type of method is based on geopotential height and pressure fields for positioning, with wind field data used as an auxiliary discrimination algorithm. For example, the algorithm described in "A Typhoon Center Positioning Method, Device, and Typhoon Path Generation Method" (CN111427100B) uses the determination of the lowest pressure center location as a basis, supplemented by other discrimination conditions. However, in real-world observations, there are many scenarios where pressure field data cannot be directly obtained. For instance, satellite observations can only obtain temperature and wind field information, not direct pressure observation. In conventional weather forecasting, wind field is a fundamental forecasting element, but pressure is not. This limits the application scenarios of pressure-based positioning methods. Pressure-based methods are mainly suitable for scenarios such as atmospheric numerical models that contain a complete range of meteorological elements.

[0007] With the development of detection technology, several artificial Earth satellites now possess the capability to detect sea surface wind fields, such as the Fengyun-3E satellite, the Haiyang-2 series satellites, and the ASCAT series satellites. These satellites use microwave scatterometers, synthetic aperture radar, and other equipment to invert sea surface wind fields. Simultaneously, with the development of digital grid weather forecasting, the demand for wind field-based tropical cyclone (typhoon) location technologies is increasing. In recent years, various techniques based on wind field identification and location have gradually developed. For example, the method and system for accurately locating the center of a tropical cyclone using synthetic radar images (CN111862005A) uses the vertical wind direction method to obtain the center of the tropical cyclone. However, this method cannot determine whether the rotation center is closed, and it may identify an open rotation center as the center of the tropical cyclone. The methods for typhoon center location in "A Method for Typhoon Center Location Applicable to Multi-Spatial Resolution Sea Surface Wind Fields" (CN114019491A) and "An Automatic Typhoon Center Location Method and Device" (CN115390160A) use prior typhoon location or model wind fields as references and determine the center location by using the corresponding error between the prior location and the observed wind field location. This method is limited in application scenarios because it requires prior determination of the tropical cyclone location and other dependent data besides the observed wind field. In "Application Research of Vortex Tracking Technology in Typhoon Location and Intensity Determination in Zhejiang Regional Model" (Yu Zhenshou, Meteorology, 2020, 46(11):1461-1473.), a method based on vorticity center identification is used for center location. However, areas with high vorticity are not necessarily rotation centers. Weather systems with high vorticity, such as fronts and shear lines, are prone to misjudgment. Secondly, the point with the maximum vorticity is not necessarily a closed rotation center. For example, upper-level troughs and easterly fluctuations are closed centers without rotation, but their vorticity shows a high value. Summary of the Invention

[0008] The purpose of this invention is to at least address one of the shortcomings of the prior art by providing a method and apparatus for locating tropical cyclones using wind fields.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: Specifically, a method for locating tropical cyclones using wind fields is proposed, including the following: Step 110: Obtain a given wind field and determine the basic attributes of the wind field, including the latitude and longitude range and resolution of the wind field; Step 120: Perform orthogonal decomposition on the wind field to obtain zonal wind and meridional wind. Zonal wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding latitude circle, and meridional wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding longitude circle. Step 130: Calculate the closed rotation center of the wind field based on the zonal wind and the meridional wind. The closed rotation center is composed of multiple potential rotation center points. Step 140: Preprocess the potential rotation center points of the closed rotation center, remove unreasonable potential rotation center points, and obtain the remaining rotation center points. The remaining rotation center points constitute the preprocessed closed rotation center. Step 150: Calculate the range of the tropical cyclone based on the preprocessed closed rotation center to obtain multiple rectangular regions with the boundaries of the four directions (east, west, south, and north) corresponding to different tropical cyclones. Step 160: Calculate the maximum wind speed within any of the rectangular areas, and filter the magnitude of the maximum wind speed to remove tropical cyclones with a maximum wind speed less than the wind speed threshold, thus obtaining the remaining tropical cyclones. Step 170: Calculate the size of the rectangular region of each of the remaining tropical cyclones, and remove tropical cyclones whose size is smaller than the range threshold to obtain the final tropical cyclones.

[0010] Furthermore, specifically, calculating the closed rotation center of the wind field based on the zonal and meridional winds includes, The latitude range of the wind field is denoted as [lat0, lat1], the longitude range as [lon0, lon1], and the resolution as gridUnit; By calculating the location where the wind speed changes from positive to negative from south to north using zonal wind, the set of location points where the zonal wind changes is obtained, denoted as set pos_u; By calculating the locations where the wind speed changes from negative to positive from west to east using meridional wind, we obtain the set of locations where the meridional wind changes, denoted as set pos_v; The intersection of zonal and meridional wind transitions is calculated based on the kd-tree algorithm. The minimum distance tolerance threshold is set to twice the gridUnit. All the intersections are used to form a set of location points, denoted as center_potential. This set of location points is defined as the potential wind field rotation center. Cluster analysis was performed on the distance matrix formed by potential wind field rotation centers based on the DBSCAN clustering method, with the tolerance distance set to 2 times the resolution (gridUnit×2), resulting in multiple cluster groups; For each cluster group, if any cluster group contains more than 2 location points, only the points with the closest distance to each other are retained to obtain the processed cluster group; For each processed cluster group, the position information of the points within the cluster group is arithmetically averaged to obtain a position information. The position information corresponding to each cluster group is the potential rotation center point, and all potential rotation centers are denoted as the set pos_center.

[0011] Furthermore, specifically, the preprocessing operation includes, Calculate the relative vorticity corresponding to each potential rotation center point, and remove potential rotation center points with vorticity less than the vorticity threshold to obtain the potential rotation center points after the first processing. Calculate the distance between potential rotation center points after the first processing. For potential rotation center points whose distance is less than the distance threshold, only the potential rotation center points with larger relative vorticity are retained to obtain the remaining rotation center points.

[0012] Furthermore, specifically, the vorticity threshold is set manually, specifically 20 × 10⁻⁶. -5 .

[0013] Furthermore, specifically, the distance threshold is set manually, specifically 200 kilometers.

[0014] Furthermore, specifically, the extent of a tropical cyclone is calculated based on the preprocessed closed rotation center, including: Step 151: Using the remaining rotation center points as the reference points for the tropical cyclone, draw a ray in each of the eight directions (north, northeast, east, southeast, south, southwest, west, and northwest) for each reference point to obtain eight rays. Interpolate the wind speed and vorticity of the wind field onto each ray to obtain a sequence of radial distances from the reference point and corresponding wind speeds and vorticities starting from the reference point. Step 152: On the sequence corresponding to each ray, starting from the reference point, calculate the radial distance when the vorticity changes from greater than 0 to less than 0 for the first time, and record this radial distance as R_vor0. If the radial distance cannot be calculated, set R_vor0 as the maximum radial distance that the wind field can reach within the region. Step 153: Calculate the maximum wind speed value within the distance interval from the reference point to R_vor0, denoted as Speed_max, and record the radial distance R_max corresponding to Speed_max; Step 154: Along the radial direction outward, starting from the radial distance R_max, calculate the radial distance R_min that first reaches a minimum value. That is, in the neighborhood of the radial distance R_min, the velocity values ​​on both sides before and after it are greater than the velocity values ​​at the distance of R_min. If R_min is not calculated, then R_min is equal to R_vor0. Step 155: Starting from the radial distance R_max to the distance R_min, calculate the radial distance at the position where the first wind speed changes from greater than 12 m / s to less than 12 m / s, and record this radial distance as R_12. If this distance cannot be found, record R_12 as missing measurement. Step 156: Calculate the radial range distance, denoted as R_bound. When R_12 is not missing, record the radial range distance R_bound in this direction as equal to R_12. When R_12 is missing, record the radial range distance R_bound in this direction as equal to the larger of R_min and R_vor0, thus obtaining the radial range distances in 8 directions. Step 157: Determine the northern boundary of the tropical cyclone by the location that reaches the maximum latitude in the northwest, due north, and northeast directions; determine the eastern boundary of the tropical cyclone by the location that reaches the maximum longitude in the northeast, due east, and southeast directions; determine the southern boundary of the tropical cyclone by the location that reaches the minimum latitude in the southeast, due south, and southwest directions; and determine the western boundary of the tropical cyclone by the location that reaches the minimum longitude in the southwest, due west, and northwest directions. This yields a rectangular area bounded by the four cardinal directions of the tropical cyclone.

[0015] Furthermore, specifically, the wind speed threshold is set manually, specifically 10 m / s.

[0016] Furthermore, specifically, the range threshold is set manually, specifically 50 kilometers.

[0017] The present invention also proposes a device for locating tropical cyclones using wind fields, comprising: The data acquisition module is used to acquire a given wind field and determine the basic attributes of the wind field, including the latitude and longitude range and resolution of the wind field. The orthogonal decomposition module is used to orthogonally decompose the wind field to obtain zonal wind and meridional wind. Zonal wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding latitude circle, and meridional wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding longitude circle. A closed rotation center calculation module is used to calculate the closed rotation center of the wind field based on the zonal wind and the meridional wind. The closed rotation center is composed of multiple potential rotation center points. The preprocessing module is used to preprocess the potential rotation center points of the closed rotation center, remove unreasonable potential rotation center points, and obtain the remaining rotation center points, which constitute the preprocessed closed rotation center. The range calculation module is used to calculate the range of a tropical cyclone based on the preprocessed closed rotation center, and obtain multiple rectangular regions corresponding to the four cardinal directions of different tropical cyclones. The first filtering module is used to calculate the maximum wind speed within any rectangular area, and filter the magnitude of the maximum wind speed to remove tropical cyclones with a maximum wind speed less than the wind speed threshold, thereby obtaining the remaining tropical cyclones. The second filtering module is used to calculate the size of the rectangular region of each remaining tropical cyclone, and remove tropical cyclones whose size is smaller than the range threshold to obtain the final tropical cyclones.

[0018] This invention proposes a method for locating tropical cyclones using wind fields, which offers the following advantages compared to existing technologies: 1. It does not rely on additional external inputs; it only requires wind field data to complete tropical cyclone identification. No additional data such as typhoon reports, predefined typhoon locations, or model wind fields are needed.

[0019] 2. This method can ensure that the identified center of a closed vortex is identified by using the center of rotation and the vorticity threshold to ensure that it is the closed center position of a cyclonic rotation.

[0020] 3. This method can simultaneously obtain multiple tropical cyclones from wind field data. Compared to conventional methods, it can directly obtain the locations of multiple tropical cyclones without additional assistance, and eliminates false or unsuitable weak vortices through various threshold filtering methods, thus conveniently obtaining multiple tropical cyclones.

[0021] 4. This invention, through a refined typhoon range control scheme, can more accurately identify the range of a typhoon and its extension distance in all directions. By judging multiple threshold distances, it can effectively avoid misidentifying typhoon attributes such as maximum wind speed and wind speed radius, especially when the background wind field has a high wind speed, reducing the occurrence of misidentifying the environmental wind field as the circulation of the tropical cyclone itself.

[0022] 5. Compared with other technical solutions, it can obtain more attribute information about tropical cyclones, including typhoon location, range, maximum wind speed (intensity), radial radius of each phase, etc., providing more reference tools for subsequent tropical cyclone diagnosis and disaster analysis, and providing decision support for disaster prevention and mitigation. Attached Figure Description

[0023] The above and other features of this disclosure will become more apparent from the detailed description of the embodiments illustrated in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals denote the same or similar elements. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort. In the drawings: Figure 1The diagram shows a flowchart of a method for locating tropical cyclones using wind fields according to the present invention. Figure 2 The diagram shown is a logical principle diagram of a method for locating tropical cyclones using wind fields according to the present invention. Figure 3 The diagram shown illustrates the zonal wind change position (represented by dots) and meridional wind change position (represented by x) in one embodiment of the present invention. Figure 4 The diagram shown is a schematic of the zonal wind change position (represented by dots) and the meridional wind change position (represented by x) obtained after calculating the intersection of zonal wind change and meridional wind change using the kd-tree algorithm in one embodiment of the present invention. Figure 5 The diagram shown is a schematic representation of the potential rotation center points obtained after cluster averaging in one embodiment of the present invention, indicated by solid black dots. Figure 6 The diagram shown is a schematic of the rotation center point obtained after vortex threshold screening in one embodiment of the present invention, represented by solid black dots. Figure 7 The diagram shows the radial velocity (solid line) and vorticity (dashed line) distribution of a tropical cyclone with its rotation center located at [20.812°N, 115.125°E] in the due east direction in one embodiment of the present invention. Figure 8 The figure shows the radial distances (the eight line segments centered on the black dots) of a tropical cyclone centered at [20.812°N, 115.125°E] and [25.021°N, 119.729°E] in one embodiment of the present invention, and the rectangular range formed by the four cardinal directions of the tropical cyclone determined by these eight radial directions. Figure 9 The figure shows the radial velocity (solid line) and vorticity (dashed line) distribution of a tropical cyclone with its rotation center located in the southeast direction of [25.021°N, 119.729°E] in one embodiment of the present invention. Detailed Implementation

[0024] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The same reference numerals used throughout the accompanying drawings indicate the same or similar parts.

[0025] Reference Figure 1 as well as Figure 2Example 1: This invention proposes a method for locating tropical cyclones using wind fields, comprising the following: Step 110: Obtain a given wind field and determine the basic attributes of the wind field, including the latitude and longitude range and resolution of the wind field; Step 120: Perform orthogonal decomposition on the wind field to obtain zonal wind and meridional wind. Zonal wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding latitude circle, and meridional wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding longitude circle. Step 130: Calculate the closed rotation center of the wind field based on the zonal wind and the meridional wind. The closed rotation center is composed of multiple potential rotation center points. Step 140: Preprocess the potential rotation center points of the closed rotation center, remove unreasonable potential rotation center points, and obtain the remaining rotation center points. The remaining rotation center points constitute the preprocessed closed rotation center. Step 150: Calculate the range of the tropical cyclone based on the preprocessed closed rotation center to obtain multiple rectangular regions with the boundaries of the four directions (east, west, south, and north) corresponding to different tropical cyclones. Step 160: Calculate the maximum wind speed within any of the rectangular areas, and filter the magnitude of the maximum wind speed to remove tropical cyclones with a maximum wind speed less than the wind speed threshold, thus obtaining the remaining tropical cyclones. Step 170: Calculate the size of the rectangular region of each of the remaining tropical cyclones, and remove tropical cyclones whose size is smaller than the range threshold to obtain the final tropical cyclones.

[0026] In this embodiment 1, the proposed method for locating tropical cyclones using wind fields solves the problem of determining the center location of tropical cyclones when only wind field data is available. This method quickly and accurately identifies the locations of multiple tropical cyclones in the wind field without relying on pressure fields, satellite-derived brightness temperature products, or manual pre-determined location assistance. Furthermore, it obtains relevant tropical cyclone information, including range, intensity, and wind circle radius, while simultaneously determining the location of the tropical cyclone. Specifically, in this preferred embodiment 1, the wind speed threshold is manually set to 10 m / s, and the range threshold is manually set to 50 km. Both the wind speed and range thresholds were determined through extensive experiments. The above is a preferred embodiment; however, other methods can be selected according to actual needs.

[0027] Furthermore, considering that the method proposed in this invention uses criteria such as wind speed gradient, excessive noise signals will affect the accuracy of the results. If the given wind field contains a large amount of noise, a low-pass filtering algorithm should be performed to reduce noise before the wind field input signal.

[0028] In a preferred embodiment of the present invention, specifically, calculating the closed rotation center of the wind field based on the zonal wind and the meridional wind includes, The latitude range of the wind field is denoted as [lat0, lat1], the longitude range as [lon0, lon1], and the resolution as gridUnit; By calculating the location where the wind speed changes from positive to negative from south to north using zonal wind, the set of location points where the zonal wind changes is obtained, denoted as set pos_u; By calculating the locations where the wind speed changes from negative to positive from west to east using meridional wind, we obtain the set of locations where the meridional wind changes, denoted as set pos_v; The intersection of zonal and meridional wind transitions is calculated based on the kd-tree algorithm. The minimum distance tolerance threshold is set to twice the gridUnit. All the intersections are used to form a set of location points, denoted as center_potential. This set of location points is defined as the potential wind field rotation center. Cluster analysis was performed on the distance matrix formed by potential wind field rotation centers based on the DBSCAN clustering method, with the tolerance distance set to 2 times the resolution (gridUnit×2), resulting in multiple cluster groups; For each cluster group, if any cluster group contains more than 2 location points, only the points with the closest distance to each other are retained to obtain the processed cluster group; For each processed cluster group, the position information of the points within the cluster group is arithmetically averaged to obtain a position information. The position information corresponding to each cluster group is the potential rotation center point, and all potential rotation centers are denoted as the set pos_center.

[0029] In this preferred embodiment, calculating the closed rotation center of the wind field in the above manner can ensure the identification of the closed rotation center, thus solving the problem that other methods cannot guarantee the rotational closure or the location is not at the rotation center.

[0030] Furthermore, considering that the target of this analysis is a tropical cyclone in the Northern Hemisphere, the identification steps for tropical cyclones in the Southern Hemisphere are similar; simply mirror the corresponding steps symmetrically around the equator. For example, "calculating the location where wind speed changes from positive to negative from south to north using zonal winds" in the Southern Hemisphere would be "calculating the location where wind speed changes from positive to negative from north to south using zonal winds." Other steps can be deduced similarly.

[0031] In a preferred embodiment of the present invention, the preprocessing operation specifically includes: Calculate the relative vorticity corresponding to each potential rotation center point, and remove potential rotation center points with vorticity less than the vorticity threshold to obtain the potential rotation center points after the first processing. Calculate the distance between potential rotation center points after the first processing. For potential rotation center points whose distance is less than the distance threshold, only the potential rotation center points with larger relative vorticity are retained to obtain the remaining rotation center points.

[0032] In this preferred embodiment, by eliminating unreasonable potential rotation center points using the above method, the problem of saddle-shaped fields in falsely identified wind fields can be solved.

[0033] Specifically, the vorticity threshold is set manually, specifically 20 × 10. -5 Specifically, the distance threshold is set manually to 200 kilometers. The vorticity threshold is derived from the Rankine vortex conceptual model. In the Rankine vortex model, a wind speed threshold of 10 m / s is taken, corresponding to a wind speed radius of 100 km, to obtain the corresponding vorticity value. = 20×10 -5 s -1 The specific vorticity threshold can be adjusted according to the application scenario and the Rankine vortex model. The distance threshold is based on the World Meteorological Organization's description of tropical cyclone characteristics. The typical size of a tropical cyclone is 200 to 500 km, so the distance threshold is set as the lower limit of the typical size—200 km. The actual scale of tropical cyclones varies greatly, from tens of kilometers to thousands of kilometers. It can be adjusted as needed in practical applications.

[0034] In a preferred embodiment of the present invention, specifically, the range of a tropical cyclone is calculated based on the preprocessed closed rotation center, including... Step 151: Using the remaining rotation center points as the reference points for the tropical cyclone, draw a ray in each of the eight directions (north, northeast, east, southeast, south, southwest, west, and northwest) for each reference point to obtain eight rays. Interpolate the wind speed and vorticity of the wind field onto each ray to obtain a sequence of radial distances from the reference point and corresponding wind speeds and vorticities starting from the reference point. Step 152: On the sequence corresponding to each ray, starting from the reference point, calculate the radial distance when the vorticity changes from greater than 0 to less than 0 for the first time, and record this radial distance as R_vor0. If the radial distance cannot be calculated, set R_vor0 as the maximum radial distance that the wind field can reach within the region. Step 153: Calculate the maximum wind speed value within the distance interval from the reference point to R_vor0, denoted as Speed_max, and record the radial distance R_max corresponding to Speed_max; Step 154: Starting from the radial distance R_max, calculate the radial distance at which the first minimum value is obtained along the radial direction outward, and record this radial distance as R_min. That is, within the neighborhood of the radial distance R_min, the velocity values ​​on both sides before and after it are greater than the velocity values ​​at the distance of R_min. If R_min is not calculated, then R_min is equal to R_vor0. Step 155: Starting from the radial distance R_max to the distance R_min, calculate the radial distance at the position where the first wind speed changes from greater than 12 m / s to less than 12 m / s, and record this radial distance as R_12. If this distance cannot be found, record R_12 as missing measurement. Step 156: When R_12 is not missing, record the radial range distance R_bound in this direction as equal to R_12. When R_12 is missing, record the radial range distance R_bound in this direction as equal to the larger of R_min and R_vor0, thus obtaining the radial range distances in 8 directions. Step 157: Determine the northern boundary of the tropical cyclone by the location that reaches the maximum latitude in the northwest, due north, and northeast directions; determine the eastern boundary of the tropical cyclone by the location that reaches the maximum longitude in the northeast, due east, and southeast directions; determine the southern boundary of the tropical cyclone by the location that reaches the minimum latitude in the southeast, due south, and southwest directions; and determine the western boundary of the tropical cyclone by the location that reaches the minimum longitude in the southwest, due west, and northwest directions. This yields a rectangular area bounded by the four cardinal directions of the tropical cyclone.

[0035] In this preferred embodiment, to ensure accurate identification of the tropical cyclone's range, intensity, and other related attributes, the above-described method for calculating the tropical cyclone's range is proposed. Steps 152 and 153 are used to ensure that the identified maximum wind speed is within the tropical cyclone vortex, preventing the identification of speeds in the external environmental wind field. The purpose of identifying the R_min distance in steps 154 to 156 is also to avoid interference from the external environment. When the environmental wind speed is greater than the vortex's own speed, the above method can effectively avoid mistaking the environmental wind field for the vortex's own circulation.

[0036] The following is an example of tropical cyclone identification based on wind field, using the wind field location method proposed in this invention to locate tropical cyclones in the northern South China Sea on September 16, 2018. Step A: Confirm the basic information of the given wind field data. The longitude range is 105°E to 125°E, and the latitude range is 10°N to 125°N. The resolution is 0.25°.

[0037] Step B involves orthogonally decomposing the wind field to obtain zonal and meridional winds.

[0038] Step C1: Calculate the closed rotation center of the wind field. Use zonal winds to calculate the positions where the values ​​change from positive to negative from south to north, obtaining the set of zonal wind transition points, such as... Figure 3 The solid black dots are shown.

[0039] Step C2: Use meridional wind to calculate the positions where the meridional wind changes from negative to positive from west to east, obtaining the set of meridional wind transition points, such as... Figure 3 The point shown has a shape of x.

[0040] Step C3: Calculate the intersection of the zonal wind transition point and the meridional wind transition point. The distance tolerance threshold for the intersection point is twice the resolution, i.e., 0.5°. The set of all obtained intersection points is denoted as the potential rotation center, such as... Figure 4 As shown.

[0041] Step C4 involves performing cluster analysis on the potential rotation centers obtained in C3, with a cluster tolerance distance that is twice the resolution, i.e., 0.5°, resulting in four cluster groups.

[0042] Step C5: For each cluster group, if the number of location points exceeds 2, only the points in that group that are closest to each other are retained.

[0043] Step C6: For each cluster group, perform an arithmetic mean on the location points within the group. This yields one location information for each group, resulting in a total of four rotation centers. Figure 5 The four solid black dots shown are located at [16.5625°N, 105.6875°E], [20.812°N, 115.125°E], [24.563°N, 121.063°E], and [25.021°N, 119.729°E].

[0044] Combination Figure 6 Step D: Calculate the vorticity corresponding to the center of rotation, which is 1.9 × 10⁻⁶. -5 s -1 69.3×10 -5 s -1 -1.0×10 -5 s -1 28.5×10 -5 s -1 Remove those with vorticity less than the threshold (20×10). -5 s -1 The center point of ) has two center points, which are [20.812°N, 115.125°E] and [25.021°N, 119.729°E].

[0045] Step E: Calculate the distance between the two center points. This distance is greater than the threshold distance (200 kilometers). Retain these two center points.

[0046] Step F1: Taking the center [20.812°N, 115.125°E] as an example, calculate the range of the tropical cyclone. Using the center point [20.812°N, 115.125°E] as the base point, draw rays in eight directions: due north, northeast, due east, southeast, due south, southwest, due west, and northwest. The wind speed and vorticity sequences in the due east direction are as follows: Figure 7 As shown in the diagram. The horizontal axis represents the distance from the center point, and the vertical axis represents the wind speed and vorticity magnitude at the corresponding radial distance. R_vor0 is the distance at which the vorticity first becomes less than 0, R_Vmax is the radial distance corresponding to the maximum wind speed, and R_12 is the radius distance of a wind speed of 12 m / s. R_min is the location of the minimum value outside the radius of the maximum wind speed.

[0047] Step F2, taking the sequence in the due east direction as an example, calculate the radial distance when the vorticity changes from greater than 0 to less than 0 for the first time. This distance is R_vor0 = 176 km.

[0048] Step F3: Calculate the maximum wind speed within the distance range from the center point to 176km in the due east direction. Speed_max = 28.6m / s, and record the radial distance R_max = 141km corresponding to the maximum wind speed.

[0049] Step F4: Starting from the radial distance R_max, calculate the radial distance R_min that first reaches a minimum value. That is, within the neighborhood of distance R_min, the velocity values ​​on both sides before and after it are greater than the velocity values ​​at the distance of R_min. We obtain R_min = 268 km.

[0050] Step F5: Starting from the radial distance R_max to the distance R_min, calculate the position where the wind speed first changes from greater than 12 m / s to less than 12 m / s, and record this radial distance as R_12. Record this radial distance as R_12 = 233 km.

[0051] Step F6: Since the radial distance R_12 is not missing, record the radial range distance R_bound = R_12 = 233km in this direction.

[0052] Step F7, from steps F1 to F6, yields the radial range distances in eight directions. The northern boundary of the tropical cyclone is determined by the maximum latitude reached in the northwest, north, and northeast directions; the eastern boundary by the maximum longitude reached in the northeast, east, and southeast directions; the southern boundary by the minimum latitude reached in the southeast, south, and southwest directions; and the western boundary by the minimum longitude reached in the southwest, west, and northwest directions. This results in a rectangular area defining the boundaries of the tropical cyclone in all four directions. The extent of this tropical cyclone is: northern boundary 23.821°N, southern boundary 15.797°N, eastern boundary 119.887°E, and western boundary 112.207°E. Figure 8 The rectangular frame surrounding the tropical cyclone shown.

[0053] Step G: Within the range of the tropical cyclone obtained in step F, calculate the maximum wind speed of this rectangular area, which is 29.1 m / s. This exceeds the default threshold of 10 m / s, so retain the center of this tropical cyclone.

[0054] Step H involves filtering the tropical cyclone range sizes obtained in Step F, removing those smaller than a threshold (default threshold is 50 km). If the range of a tropical cyclone exceeds the threshold, its center is retained.

[0055] The identification process for the other center point [25.021°N, 119.729°E] is similar, but due to the weaker vortex intensity at this center, its range calculation differs from that at [20.812°N, 115.125°E]. The detailed steps for determining its southeast radial range are demonstrated here for reference.

[0056] Step f1: Taking the center [25.021°N, 119.729°E] as an example, calculate the range of the tropical cyclone. Using the center point [25.021°N, 119.729°E] as the base point, draw a ray in each of the eight directions: due north, northeast, due east, southeast, due south, southwest, west, and northwest. The wind speed and vorticity sequences in the southeast direction are as follows: Figure 9 As shown in the figure. The horizontal axis represents the distance from the center point, the vertical axis represents the wind speed and vorticity at the corresponding radial distance, R_vor0 is the distance at which the vorticity first becomes less than 0, R_Vmax is the radial distance corresponding to the maximum wind speed, and R_min is the minimum value position outside the radius of the maximum wind speed.

[0057] Step f2, taking the sequence in the southeast direction as an example, calculate the radial distance when the vorticity changes from greater than 0 to less than 0 for the first time. This distance is R_vor0 = 72km.

[0058] Step f3: In the southeast direction, starting from the center point to 72km, calculate the maximum wind speed value within this distance range, Speed_max=7.2m / s, and record the radial distance R_max=42km corresponding to the maximum wind speed.

[0059] Step f4: Starting from the radial distance R_max, calculate the radial distance R_min that first reaches a minimum value. That is, within the neighborhood of distance R_min, the velocity values ​​on both sides before and after it are greater than the velocity values ​​at the distance of R_min. We obtain R_min = 147 km.

[0060] Step f5: Starting from the radial distance R_max to the distance R_min, calculate the position where the first wind speed changes from greater than 12 m / s to less than 12 m / s, and record this radial distance as R_12. For example... Figure 9 The distance shown cannot be found, so R_12 is marked as missing.

[0061] Step f6: Since R_12 is missing, record the radial range distance R_bound in this direction as the larger of R_min and R_vor0. Since R_min > R_vor0, set R_bound = R_min = 147km.

[0062] By repeating the above steps, information such as radial distances and extent in eight directions is obtained. The method and steps are the same as described above and will not be repeated here. Finally, the extent of the tropical cyclone centered at [25.021°N, 119.729°E] is obtained as follows: Figure 7 The rectangle in the northeast direction is shown.

[0063] The present invention also proposes a device for locating tropical cyclones using wind fields, comprising: The data acquisition module is used to acquire a given wind field and determine the basic attributes of the wind field, including the latitude and longitude range and resolution of the wind field. The orthogonal decomposition module is used to orthogonally decompose the wind field to obtain zonal wind and meridional wind. Zonal wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding latitude circle, and meridional wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding longitude circle. A closed rotation center calculation module is used to calculate the closed rotation center of the wind field based on the zonal wind and the meridional wind. The closed rotation center is composed of multiple potential rotation center points. The preprocessing module is used to preprocess the potential rotation center points of the closed rotation center, remove unreasonable potential rotation center points, and obtain the remaining rotation center points, which constitute the preprocessed closed rotation center. The range calculation module is used to calculate the range of a tropical cyclone based on the preprocessed closed rotation center, and obtain multiple rectangular regions corresponding to the four cardinal directions of different tropical cyclones. The first filtering module is used to calculate the maximum wind speed within any rectangular area, and filter the magnitude of the maximum wind speed to remove tropical cyclones with a maximum wind speed less than the wind speed threshold, thereby obtaining the remaining tropical cyclones. The second filtering module is used to calculate the size of the rectangular region of each remaining tropical cyclone, and remove tropical cyclones whose size is smaller than the range threshold to obtain the final tropical cyclones.

[0064] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment, depending on actual needs.

[0065] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0066] If the integrated module is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or system capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0067] Although the description of the invention has been quite detailed and particularly of several described embodiments, it is not intended to limit it to any of these details or embodiments or any particular embodiment, but should be considered as providing a broad possible interpretation of the claims by referring to the appended claims and taking into account the prior art, thereby effectively covering the intended scope of the invention. Furthermore, the invention has been described above with respect to embodiments foreseeable by the inventors in order to provide a useful description, and non-substantial modifications to the invention that have not yet been foreseen may still represent equivalent modifications.

[0068] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any embodiment that achieves the technical effects of the present invention using the same means should fall within the protection scope of the present invention. Within the protection scope of the present invention, various modifications and variations can be made to the technical solutions and / or implementation methods.

Claims

1. A method for locating tropical cyclones using wind fields, characterized in that, Including the following: Step 110: Obtain a given wind field and determine the basic attributes of the wind field, including the latitude and longitude range and resolution of the wind field; Step 120: Perform orthogonal decomposition on the wind field to obtain zonal wind and meridional wind. Zonal wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding latitude circle, and meridional wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding longitude circle. Step 130: Calculate the closed rotation center of the wind field based on the zonal wind and the meridional wind. The closed rotation center is composed of multiple potential rotation center points. Step 140: Preprocess the potential rotation center points of the closed rotation center, remove unreasonable potential rotation center points, and obtain the remaining rotation center points. The remaining rotation center points constitute the preprocessed closed rotation center. Step 150: Calculate the range of the tropical cyclone based on the preprocessed closed rotation center to obtain multiple rectangular regions with the boundaries of the four directions of east, west, south and north corresponding to different tropical cyclones. Step 160: Calculate the maximum wind speed within any of the rectangular areas, and filter the magnitude of the maximum wind speed to remove tropical cyclones with a maximum wind speed less than the wind speed threshold, thus obtaining the remaining tropical cyclones. Step 170: Calculate the size of the rectangular region of each of the remaining tropical cyclones, and remove tropical cyclones whose size is smaller than the range threshold to obtain the final tropical cyclones; Specifically, the closed rotation center of the wind field is calculated based on the zonal and meridional winds. include, The latitude range of the wind field is denoted as [lat0, lat1], the longitude range as [lon0, lon1], and the resolution as gridUnit; By calculating the location where the wind speed changes from positive to negative from south to north using zonal wind, the set of location points where the zonal wind changes is obtained, denoted as set pos_u; By calculating the locations where the wind speed changes from negative to positive from west to east using meridional wind, we obtain the set of locations where the meridional wind changes, denoted as set pos_v; The intersection of zonal and meridional wind transitions is calculated based on the kd-tree algorithm. The minimum distance tolerance threshold is set to twice the gridUnit. All the intersections are used to form a set of location points, denoted as center_potential. This set of location points is defined as the potential wind field rotation center. Cluster analysis was performed on the distance matrix formed by potential wind field rotation centers based on the DBSCAN clustering method, with the tolerance distance set to twice the resolution, i.e., gridUnit×2, to obtain multiple cluster groups; For each cluster group, if any cluster group contains more than 2 location points, only the points with the closest distance to each other are retained to obtain the processed cluster group; For each processed cluster group, the position information of the points within the cluster group is arithmetically averaged to obtain a position information. The position information corresponding to each cluster group is the potential rotation center point, and all potential rotation centers are denoted as the set pos_center.

2. The method for locating tropical cyclones using wind fields according to claim 1, characterized in that, Specifically, the preprocessing includes, Calculate the relative vorticity corresponding to each potential rotation center point, and remove potential rotation center points with vorticity less than the vorticity threshold to obtain the potential rotation center points after the first processing. Calculate the distance between potential rotation center points after the first processing. For potential rotation center points whose distance is less than the distance threshold, only the potential rotation center points with larger relative vorticity are retained to obtain the remaining rotation center points.

3. The method for locating a tropical cyclone using wind field according to claim 2, characterized in that, Specifically, the vorticity threshold is set manually, specifically 20 × 10. -5 .

4. The method for locating a tropical cyclone using a wind field according to claim 2, characterized in that, Specifically, the distance threshold is set manually, specifically 200 kilometers.

5. The method for locating a tropical cyclone using a wind field according to claim 1, characterized in that, Specifically, the extent of a tropical cyclone is calculated based on the preprocessed closed rotation center, including: Step 151: Using the remaining rotation center points as the reference points for the tropical cyclone, draw a ray in each of the eight directions (north, northeast, east, southeast, south, southwest, west, and northwest) for each reference point to obtain eight rays. Interpolate the wind speed and vorticity of the wind field onto each ray to obtain a sequence of radial distances from the reference point and corresponding wind speeds and vorticities starting from the reference point. Step 152: On the sequence corresponding to each ray, starting from the reference point, calculate the radial distance when the vorticity changes from greater than 0 to less than 0 for the first time, and record this radial distance as R_vor0. If this radial distance cannot be calculated, set R_vor0 as the maximum radial distance that can be reached within the wind field area. Step 153: Calculate the maximum wind speed value within the distance interval from the reference point to R_vor0, denoted as Speed_max, and record the radial distance R_max corresponding to Speed_max; Step 154: Along the radial direction outward, starting from the radial distance R_max, calculate the radial distance at which the first minimum value is obtained, and denot it as R_min. That is, in the neighborhood of the radial distance R_min, the velocity values ​​on both sides before and after it are greater than the velocity values ​​at the distance of R_min. If R_min is not calculated, then R_min is equal to R_vor0. Step 155: Starting from the radial distance R_max to the distance R_min, calculate the radial distance at the position where the first wind speed changes from greater than 12 m / s to less than 12 m / s, and record this radial distance as R_12. If this distance cannot be found, record R_12 as missing measurement. Step 156: Calculate the radial range distance, denoted as R_bound. When R_12 is not missing, record the radial range distance R_bound in this direction as equal to R_12. When R_12 is missing, record the radial range distance R_bound in this direction as equal to the larger of R_min and R_vor0. This yields the radial range distances in 8 directions. Step 157: Determine the northern boundary of the tropical cyclone by the location that reaches the maximum latitude in the northwest, due north, and northeast directions; determine the eastern boundary of the tropical cyclone by the location that reaches the maximum longitude in the northeast, due east, and southeast directions; determine the southern boundary of the tropical cyclone by the location that reaches the minimum latitude in the southeast, due south, and southwest directions; and determine the western boundary of the tropical cyclone by the location that reaches the minimum longitude in the southwest, due west, and northwest directions. This yields a rectangular area bounded by the four cardinal directions of the tropical cyclone.

6. The method for locating a tropical cyclone using wind field according to claim 1, characterized in that, Specifically, the wind speed threshold is set manually, specifically 10 m / s.

7. The method for locating a tropical cyclone using a wind field according to claim 1, characterized in that, Specifically, the range threshold is set manually, specifically 50 kilometers.

8. A device for locating tropical cyclones using wind fields, characterized in that, The apparatus comprising the steps of the method according to any one of claims 1-7, wherein the method is applied, the apparatus includes: The data acquisition module is used to acquire a given wind field and determine the basic attributes of the wind field, including the latitude and longitude range and resolution of the wind field. The orthogonal decomposition module is used to orthogonally decompose the wind field to obtain zonal wind and meridional wind. Zonal wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding latitude circle, and meridional wind is defined as the projection distance obtained by projecting the wind vector of the wind field onto the corresponding longitude circle. The closed rotation center calculation module is used to calculate the closed rotation center of the wind field based on the zonal wind and the meridional wind. The closed rotation center is composed of multiple potential rotation center points. The preprocessing module is used to preprocess the potential rotation center points of the closed rotation center, remove unreasonable potential rotation center points, and obtain the remaining rotation center points, which constitute the preprocessed closed rotation center. The range calculation module is used to calculate the range of a tropical cyclone based on the preprocessed closed rotation center, and obtain multiple rectangular regions corresponding to the four cardinal directions of different tropical cyclones. The first filtering module is used to calculate the maximum wind speed within any rectangular area, and filter the magnitude of the maximum wind speed to remove tropical cyclones with a maximum wind speed less than the wind speed threshold, thereby obtaining the remaining tropical cyclones. The second filtering module is used to calculate the size of the rectangular region of each remaining tropical cyclone, and remove tropical cyclones whose size is smaller than the range threshold to obtain the final tropical cyclones.

Images