A radar three-dimensional cloud field profile generation method and system based on an earth spherical surface baseline

Abstract

This invention discloses a method and system for generating three-dimensional cloud field profiles based on the Earth's spherical baseline, belonging to the field of meteorological radar data processing technology. By establishing the coordinate transformation relationship between the planar radar polar coordinate system based on the Earth's spherical surface and the computer screen rectangular coordinate system, the minor arc baseline of the great circle of the Earth, determined by any two points on the Earth's spherical surface, is analyzed and calculated. Furthermore, by calculating the elevation angle, azimuth angle, and slant range of grid points in the vertical profile rectangular coordinate system of the radar reflectivity factor in the radar polar coordinate system, the radar reflectivity factor analysis value of these grid points is obtained using a vertical linear interpolation method. By replacing the traditional planar baseline with the minor arc of the great circle of the Earth's spherical surface, spatial position distortion under long-distance observation is effectively overcome, significantly improving the calculation accuracy and geometric realism of the three-dimensional cloud field profile. This method is suitable for refined meteorological monitoring and dynamic tracking and analysis of strong convective cloud systems.

Description

Technical Field

[0001] This application relates to the field of meteorological radar data processing technology, and more specifically, to a method and system for generating three-dimensional radar cloud field profiles based on the Earth's spherical baseline. Background Technology

[0002] In the field of meteorological observation and severe convective weather monitoring, radar three-dimensional cloud field profile generation technology is the core technical tool for analyzing the vertical structure of cloud systems, identifying precipitation types, and carrying out severe convective weather early warning. Its accurate generation highly depends on the fine processing of radar data and high-precision coordinate transformation technology. Currently, mainstream weather radars all adopt volume scan (VCP) observation mode, which obtains three-dimensional data of cloud systems through multi-elevation angle 360° all-round scanning. Based on this technology, two existing technical solutions have been formed, as follows: (1) Fixed azimuth radial vertical scanning technology (RHI mode): This technology uses a fixed radar azimuth angle to carry out vertical continuous scanning along the radial direction, collects reflectivity factor data at different elevation angles under a single azimuth angle, and finally generates a distance-height (RHI) two-dimensional profile. The "Meteorological Radar Observation Specification" clearly records the standard operating procedure and basic data processing method of this technology; Chen Daren et al. (2010, "Automatic Implementation Algorithm of Combined RHI Based on Volume Scan Mode", Meteorology) applied it to the command and control of artificial weather modification operations, but this technology can only obtain vertical profiles in a single direction, which is difficult to meet the needs of cloud field structure analysis in any direction. (2) Arbitrary baseline vertical profile algorithm: In order to overcome the limitation of the single direction of the RHI mode, relevant research has proposed an arbitrary baseline vertical profile algorithm. The core idea is to generate a vertical profile of the specified baseline by presetting a plane baseline in any direction, performing coordinate transformation and interpolation processing on the VCP observation data, which significantly improves the flexibility of the baseline direction. Early algorithms mostly built baseline models based on the ground plane, such as the scheme proposed by Guan Li, Wei Ming, et al. (2015, "Three-dimensional visualization of Doppler radar intensity data based on MATLAB platform", Journal of Henan Normal University: Natural Science Edition), which can obtain radar echo intensity of arbitrary profiles. However, its core is based on the assumption of planar geometry and does not consider the characteristics of the Earth's spherical surface, making it difficult to adapt to long-distance radar observation scenarios and prone to spatial distortion. To address this deficiency, Liu Yan et al. (2010, "Vertical profile algorithm of radar reflectivity factor for arbitrary baselines", Jilin Meteorological Bureau) proposed a coordinate transformation approach based on the Earth's spherical projection. The vertical profile is generated through spherical projection conversion and interpolation of polar coordinates to rectangular coordinates. This is a subdivision and optimization direction of the vertical profile algorithm for arbitrary baselines, but there is still room for further improvement in computational accuracy and engineering adaptability.

[0003] The existing radar three-dimensional cloud field vertical profile generation technology adopts the planar baseline assumption, which treats the radar's transmitting and receiving baselines as a plane to simplify the calculation. Although it can initially realize the generation of radar reflectivity factor vertical profiles, it still has the following key defects, which make it difficult to meet the actual needs of refined meteorological monitoring and operational applications: (1) Insufficient baseline flexibility and adaptability: The existing algorithm needs to preset baseline parameters or rely on fixed target areas. It cannot dynamically adjust according to the movement of cloud systems and the location of sudden strong convection, making it difficult to achieve continuous tracking and monitoring. The operation is cumbersome and has a lag. (2) Contradiction between vertical resolution and data continuity: The VCP mode is limited by the number of elevation angle layers. The data interval between adjacent elevation angles of distant targets is large, and the interpolation profile is prone to discontinuity and distortion. The RHI mode can only cover a single azimuth and cannot form a large-scale multi-dimensional continuous profile, making it difficult to reflect the overall vertical structure of the cloud system. (3) Lack of coordinate transformation accuracy and universality: Some technologies use a planar projection model, which does not fully consider the characteristics of the Earth's spherical surface, resulting in large transformation errors for distant targets.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for generating three-dimensional radar cloud field profiles based on the Earth's spherical baseline. This method can deeply integrate the Earth's spherical geometric model and coordinate transformation relationship to generate high-precision profiles. It aims to transform radar profile calculations based on planar assumptions and with geometric distortion errors into high-precision spherical baseline profile generation that conforms to the actual spatial geometry of the Earth. This will provide technical support for refined meteorological monitoring, dynamic tracking of strong convective cloud systems, and large-scale radar network observation.

[0006] In a first aspect, this application provides a method for generating a radar three-dimensional cloud field profile based on the Earth's spherical baseline, including: Establish a coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system, which is used to project radar data points onto the computer screen display interface; Select any two points A and B in the Cartesian coordinate system on the computer screen, and determine the minor arc of the great circle between the two points based on the geometric model of the Earth's sphere, which serves as the spherical baseline of the vertical profile of the radar reflectivity factor. Several sampling points are selected at preset intervals on the spherical baseline. Based on the coordinate mapping relationship and the spherical trigonometric relationship, the radar parameters corresponding to each sampling point are calculated. The radar parameters include elevation angle, azimuth angle, slant range, and altitude. A vertical profile rectangular coordinate system is constructed with the spherical baseline as the horizontal axis and the altitude as the vertical axis. The radar reflectivity factor of each sampling point is mapped to this vertical profile rectangular coordinate system to generate a three-dimensional cloud field vertical profile.

[0007] Furthermore, establishing the coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system includes: The radar polar coordinate system is established with the vertical projection of the radar antenna onto the Earth's sphere as the pole, due north as the polar axis, the arc length of the sphere as the polar radius, and the azimuth angle as the polar angle. Using the projection of the pole on the computer screen as the origin, a rectangular coordinate system for the computer screen is established, and the distance represented by a unit pixel is determined. A coordinate transformation relationship between the radar polar coordinate system and the computer screen rectangular coordinate system is then established.

[0008] Furthermore, establishing the coordinate transformation relationship between the radar polar coordinate system and the computer screen rectangular coordinate system includes:

[0009] Where (x,y) are the coordinates in the Cartesian coordinate system of the computer screen, and (s,θ) are the polar radius and azimuth angle in the radar polar coordinate system, where s is the polar radius and θ is the polar angle; (x o' y o' ) represents the coordinates of the pole in the screen coordinate system, and Δx and Δy represent the distance represented by a unit pixel.

[0010] Furthermore, the determination of the minor arc of the great circle between two points based on the Earth's spherical geometry model includes: Convert the screen coordinates of points A and B to polar coordinates in the radar polar coordinate system; Based on the polar radius and azimuth of points A and B, the central angles corresponding to the two points on the Earth's surface are calculated using spherical trigonometric relationships. The arc length of the minor arc of the great circle is determined by multiplying the central angle by the Earth's radius.

[0011] Furthermore, the spherical trigonometric relationship includes: Construct a spherical triangle consisting of the Earth's center, the poles, and the corresponding spherical projection points of points A and B; The spherical angles of the spherical triangle are calculated using the cosine theorem of the spherical triangle, and the azimuth relationship between the sampling point and point A is determined using the sine theorem of the spherical triangle. For each sampling point, based on the target arc length between the sampling point and point A, and combined with the relationship between the spherical angle and azimuth angle, the polar radius of the sampling point is calculated using the cosine theorem of the spherical triangle, and the azimuth angle of the sampling point is calculated using the sine theorem of the spherical triangle.

[0012] Furthermore, the calculation of the azimuth angle of the sampling point using the sine theorem for spherical triangles includes: When the polar radius of point A is zero, the target arc length is taken as the polar radius of the sampling point, and the azimuth of the sampling point is equal to the azimuth of point A; When the polar radius of point B is zero, the polar radius of the sampling point is determined to be equal to the difference between the polar radius of point A and the target arc length, and the azimuth of the sampling point is equal to the azimuth of point A. When the difference between the azimuth angles of points A and B is zero, the polar radius of the sampling point is determined to be equal to the sum of the polar radius of point A and the target arc length, and the azimuth angle of the sampling point is equal to the azimuth angle of point A. When the polar radii of points A and B are both non-zero and the difference in azimuth angles is π, the polar radii of the sampling point are determined according to the linear sum-difference relationship between the polar radii of point A and the target arc length, and the azimuth angle of the sampling point is equal to the azimuth angle of point A or the azimuth angle of point B.

[0013] Furthermore, the step of selecting a plurality of sampling points at preset intervals on the spherical baseline includes: Set the unit distance of the abscissa of the vertical profile rectangular coordinate system, and the unit distance is not greater than the unit pixel distance of the computer screen rectangular coordinate system; Calculate the total arc length of the spherical baseline and determine the number of sampling points to be the smallest integer not less than the ratio of the total arc length to the unit distance; The spherical baseline is discretized at equal intervals according to the unit distance to obtain the arc length of each sampling point along the spherical baseline from point A, which is taken as the target arc length.

[0014] Furthermore, the step of calculating the radar parameters corresponding to each sampling point based on the coordinate mapping relationship and the spherical trigonometric relationship includes: Convert the screen coordinates of points A and B into polar coordinates in the radar polar coordinate system, and construct a spherical triangle composed of the Earth's center, the pole, and the corresponding spherical projection points of points A and B. The spherical angle at the pole of the spherical triangle is calculated using the cosine theorem of the spherical triangle. Based on the target arc length between the sampling point and point A and the spherical angle, the polar radius and azimuth of the sampling point are calculated using the sine and cosine theorems of the spherical triangle. The elevation angle and slant distance are determined based on the polar radius, azimuth, and target altitude of the sampling point.

[0015] Furthermore, the step of mapping the radar reflectivity factor of each sampling point to the Cartesian coordinate system of the vertical profile to generate a three-dimensional cloud field vertical profile includes: In the vertical profile rectangular coordinate system, for a grid point with the horizontal position of each sampling point as a reference, the target altitude is determined according to the ordinate of the grid point, and the two adjacent elevation layers where the target altitude is located are determined. Based on the elevation angle and slant range corresponding to the sampling point, the radar reflectivity factor observation values ​​at corresponding positions on the two adjacent elevation angle layers are obtained from the radar volume scan data. Based on the target altitude and the height difference between the two adjacent elevation layers, a vertical linear interpolation is performed to obtain the radar reflectivity factor analysis value of the grid points; the radar reflectivity factor analysis value of each grid point constitutes the three-dimensional cloud field vertical profile.

[0016] Secondly, this application also proposes a radar three-dimensional cloud field profile generation system based on the Earth's spherical baseline, comprising: The module is used to establish the coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system, which is used to project radar data points onto the computer screen display interface. The determination module is used to select any two points A and B in the Cartesian coordinate system on the computer screen, and determine the minor arc of the great circle between the two points based on the geometric model of the Earth's sphere, which serves as the spherical baseline of the vertical profile of the radar reflectivity factor. The calculation module is used to select a number of sampling points at preset intervals on the spherical baseline, and calculate the radar parameters corresponding to each sampling point according to the coordinate mapping relationship and the spherical trigonometric relationship; the radar parameters include elevation angle, azimuth angle, slant range and altitude. The generation module is used to construct a vertical profile rectangular coordinate system with the spherical baseline as the horizontal axis and the altitude as the vertical axis, and to map the radar reflectivity factor of each sampling point to the vertical profile rectangular coordinate system to generate a three-dimensional cloud field vertical profile.

[0017] As can be seen from the above, the radar 3D cloud field profile generation method and system based on the Earth's spherical baseline provided in this application establishes a precise mapping relationship between the radar polar coordinate system based on the Earth's spherical projection and the computer screen rectangular coordinate system by introducing the minor arc of the great circle of the Earth as the geometric baseline of the radar reflectivity factor vertical profile. This solves the key technical defects of the prior art, such as spatial position distortion at long distances, insufficient baseline flexibility, and lack of coordinate transformation accuracy caused by the assumption of a planar baseline. Compared with the traditional fixed azimuth RHI mode and planar arbitrary baseline algorithm, this scheme can dynamically adjust the A and B endpoints according to the movement of the cloud system or the position of strong convection to continuously track the target, significantly improving the baseline adaptability. By using the cosine theorem and sine theorem of spherical triangles to calculate the spatial coordinates of the sampling points, the geometric cumulative error under long-distance observation is effectively eliminated, ensuring the accurate restoration of the 3D cloud field structure. At the same time, the high-resolution profile generation is achieved by using the vertical linear interpolation method while ensuring data continuity. The overall technical solution combines geometric rigor with engineering feasibility, providing high-precision and highly flexible data support for refined meteorological monitoring, severe convective weather early warning, and large-scale radar network observation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating the steps of the radar three-dimensional cloud field profile generation method based on the Earth's spherical baseline disclosed in an embodiment of the present invention. Figure 2 This is a schematic diagram of radar data projected onto the Earth's sphere according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the radar polar coordinate system and the computer screen rectangular coordinate system disclosed in the embodiments of the present invention; Figure 4 This is a schematic diagram of the radar altimeter formula disclosed in an embodiment of the present invention; Figure 5 This is a schematic diagram of the vertical profile baseline of the radar reflectivity factor in the Cartesian coordinate system of the computer screen disclosed in the embodiments of the present invention; Figure 6 This is a schematic diagram of the Earth's spherical triangle determined by the vertical profile baseline of the radar reflectivity factor disclosed in the embodiments of the present invention; Figure 7 This is a schematic diagram of the radar reflectivity factor vertical profile rectangular coordinate system disclosed in the embodiments of the present invention; Figure 8 This is a schematic diagram of the reflectivity factor (PPI) at an elevation angle of 1.5° based on volume scan data from the Changchun radar, as disclosed in this embodiment of the invention. Figure 9 It is the vertical profile of radar reflectivity factor determined by baseline AB as disclosed in the embodiments of the present invention; Figure 10 This is a schematic diagram of the radar three-dimensional cloud field profile generation system based on the Earth's spherical baseline disclosed in an embodiment of the present invention. Detailed Implementation

[0020] Unless otherwise defined, all technical and scientific terms used in this embodiment have the same meaning as commonly understood by one of ordinary skill in the art to which this embodiment belongs; the terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this embodiment; the terms "comprising" and "having," and any variations thereof, in the specification and the foregoing drawings of this embodiment are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification and the foregoing drawings of this embodiment are used to distinguish different objects, not to describe a specific order.

[0021] The implementation details of the technical solution in this embodiment are described in detail below: This embodiment proposes a method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline, such as... Figure 1 As shown, the method includes: S101 establishes the coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system, which is used to project radar data points onto the computer screen display interface.

[0022] Furthermore, in step S101, establishing the coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system includes: The radar polar coordinate system is established with the vertical projection of the radar antenna onto the Earth's sphere as the pole, due north as the polar axis, the arc length of the sphere as the polar radius, and the azimuth angle as the polar angle. Using the projection of the pole on the computer screen as the origin, a rectangular coordinate system for the computer screen is established, and the distance represented by a unit pixel is determined. A coordinate transformation relationship between the radar polar coordinate system and the computer screen rectangular coordinate system is then established.

[0023] Specifically, in this embodiment, it is assumed that the Earth is a perfect sphere, O e At the center of the Earth, r e For the Earth's radius, such as Figure 2 The image shown is a schematic diagram of the radar data projected onto the Earth's surface in this embodiment. The altitude is h. r radar antenna O r The vertical projection of radar data point P on the Earth's surface is O'. The vertical projection of P on the Earth's surface with an elevation angle of δ and a slant range of r is P', and the altitude is h. For O r The projection of P onto the Earth's surface has an arc length of s. δ=0 The point where the radar beam axis with an elevation angle of 0 intersects with PP' is the intersection point.

[0024] by Figure 2 A planar radar polar coordinate system is established with O' as the pole, the ray extending northward from O' as the polar axis, s as the polar radius, θ as the polar angle, and clockwise direction as the positive direction. This system is then mapped onto a Cartesian coordinate system xO on the computer screen. s In y, among which, such as Figure 3 The diagram shows the radar polar coordinate system and the computer screen rectangular coordinate system of this embodiment. s (0, 0) is the origin of the Cartesian coordinate system on the computer screen. The positive x-axis points to the right, and the positive y-axis points downwards. Δx represents the distance per pixel along the x-axis, and Δy represents the distance per pixel along the y-axis, with Δx = Δy. Let x... o' = yo' And with O'(x o' y o' (x) is the center of the circle. o' A circle with radius is tangent to both the x-axis and the y-axis. Figure 1 P'(s, θ) in coordinate system xO s The coordinates in y are P'(x, y).

[0025] Regarding Δx, Δy, and x o' y o' The selection of [value]. In computer programming, radar images are stored using in-memory images. Δx and Δy represent the distance per pixel in the in-memory image, in km / pixel, and Δx = Δy. o' y o' The center of the image in memory is given in pixels, and x... o' =y o' Then the maximum radial detection range r of the radar. max The maximum distance s projected onto the Earth's spherical surface max ≤Δx·x o' The projection of the radar slant range onto the Earth's spherical surface decreases with increasing elevation angle. Let Δr be the radar length, N be the number of radar units per radial direction, and δ... min δ max For the lowest and highest elevation angles of the radar volume scan data, Δs min Let this be the minimum distance projected onto the Earth's surface by the radar's length.

[0026]

[0027] To use all polar coordinate data when calculating rectangular coordinates, Δx = Δy ≤ Δs should be ensured. min x o' = y o' ≥s max / Δx≥s max / Δs min For example, the volume scan database of the Changchun CINRAD / CC radar is 0.3 km long, with 500 entries per radial direction, a minimum elevation angle of 0.5°, a maximum elevation angle of 19.5°, a radar antenna altitude of 0.2946 km, and an average Earth radius of 6371.004 km. The calculated Δs... min =0.283km, s max =149.95km, s max / Δs min =530.27. For ease of calculation during programming, Δx = Δy = 0.25km can be chosen, where x... o' = y o' =600.

[0028] Furthermore, the coordinate transformation relationship between the radar polar coordinate system and the computer screen rectangular coordinate system is established.

[0029] Specifically, in this embodiment, equations (1) and (2) give the transformation relationship between P'(s, θ) and P'(x, y).

[0030] (1) (2) Where (x,y) are the coordinates in the Cartesian coordinate system of the computer screen, and (s,θ) are the polar radius and azimuth angle in the radar polar coordinate system, where s is the polar radius and θ is the polar angle; (x o' y o' ) represents the coordinates of the pole in the screen coordinate system, and Δx and Δy represent the distance represented by a unit pixel.

[0031] In equation (2), when x = xo' and y = yo', θ can be defined as any value, such as 0 or no value, according to programming needs. In this embodiment, custom cases can be handled in this way.

[0032] In some embodiments, the conversion of other parameters is also included. For example... Figure 4 The diagram shown is a schematic of the radar height measurement formula in this embodiment, where ∠O e QP=∠O e O r P δ=0 =π / 2, ∠O'O e P'=s / r e QP = r·cosδ, QO r =r·sinδ.

[0033] In triangle QOeP,

[0034] (3) When s≠0, in triangle QOeP, 4 In triangle QOeP, (5) When s≠0, in triangle QOrP, 6 When s≠0, in triangle OrOeP, 7 Equations (1) to (7) give the conversion relationship between radar parameters and computer screen coordinates. For example, equations (1), (3), and (5) can be used to calculate the coordinates (x, y) and altitude h of any radar data point (δ, θ, r) on the computer screen; equations (2), (4), and (5) can be used to calculate the azimuth θ, slant range r, and altitude h of any point (x, y) on the computer screen at an elevation angle of δ; when calculating CAPPI, equations (2), (6), and (7) can be used to calculate the coordinates (δ, θ, r) of any point (x, y) on the computer screen at an altitude of h.

[0035] S102. Select any two points A and B in the Cartesian coordinate system on the computer screen, and determine the minor arc of the great circle between the two points based on the Earth's spherical geometric model, which serves as the spherical baseline of the vertical profile of the radar reflectivity factor.

[0036] Further, in step S102, determining the minor arc of the great circle between two points based on the Earth's spherical geometric model includes: converting the screen coordinates of points A and B into polar coordinates in the radar polar coordinate system; calculating the central angles of the two points on the Earth's sphere using spherical trigonometric relationships based on the polar radius and azimuth of points A and B; and determining the arc length of the minor arc of the great circle based on the product of the central angle and the Earth's radius.

[0037] Furthermore, the spherical trigonometric relationship includes: Construct a spherical triangle consisting of the Earth's center, the poles, and the corresponding spherical projection points of points A and B; The spherical angles of the spherical triangle are calculated using the cosine theorem of the spherical triangle, and the azimuth relationship between the sampling point and point A is determined using the sine theorem of the spherical triangle. For each sampling point, based on the target arc length between the sampling point and point A, and combined with the relationship between the spherical angle and azimuth angle, the polar radius of the sampling point is calculated using the cosine theorem of the spherical triangle, and the azimuth angle of the sampling point is calculated using the sine theorem of the spherical triangle.

[0038] Specifically, in this embodiment, such as Figure 5 The diagram shown is a schematic representation of the vertical profile baseline of the radar reflectivity factor in the Cartesian coordinate system of the computer screen in this embodiment. Two points A(x,y) are arbitrarily determined on the computer screen. a y a B(x) b y b Then, it can be converted into polar coordinates A(s) by equation (2). a θ a ), B(s) b θ b (The minor arc of the great circle of the Earth passing through points A and B) In coordinate system xOs Projection in y This is the baseline we are looking for. Among them, the minor arc of the great circle... The arc length is determined by spherical geometry (based on s) a θ a s b θ b )Sure.

[0039] Let d AB for Arc length, Δd is the distance represented by a unit pixel on the vertical cross-section of the radar reflectivity factor, i.e. Point P' on i (s) i θ i The unit distance between point A and point B, and Δd≤Δx, n=ceil(d AB / Δd) is not less than d AB The smallest integer of / Δd, then passing through A and P' i The arc length d of the minor arc of the great circle on the Earth's surface i =Δd×i, where i∈[0,n]. In coordinate system xO s In y, when line AB does not pass through O', let P'' i For O'P' i The intersection point with line AB is O'P'. i ≥O'P'' i The baseline It convexes outward relative to line AB.

[0040] Furthermore, the calculation of the azimuth angle of the sampling point using the sine theorem for spherical triangles includes: When the polar radius of point A is zero, the target arc length is taken as the polar radius of the sampling point, and the azimuth of the sampling point is equal to the azimuth of point A; When the polar radius of point B is zero, the polar radius of the sampling point is determined to be equal to the difference between the polar radius of point A and the target arc length, and the azimuth of the sampling point is equal to the azimuth of point A. When the difference between the azimuth angles of points A and B is zero, the polar radius of the sampling point is determined to be equal to the sum of the polar radius of point A and the target arc length, and the azimuth angle of the sampling point is equal to the azimuth angle of point A. When the polar radii of points A and B are both non-zero and the difference in azimuth angles is π, the polar radii of the sampling point are determined according to the linear sum-difference relationship between the polar radii of point A and the target arc length, and the azimuth angle of the sampling point is equal to the azimuth angle of point A or the azimuth angle of point B.

[0041] S103, select a number of sampling points at a preset interval on the spherical baseline, and calculate the radar parameters corresponding to each sampling point according to the coordinate mapping relationship and the spherical trigonometric relationship; the radar parameters include elevation angle, azimuth angle, slant range and altitude.

[0042] Further, in step S103, selecting a number of sampling points at preset intervals on the spherical baseline includes: Set the unit distance of the abscissa of the vertical profile rectangular coordinate system, and the unit distance is not greater than the unit pixel distance of the computer screen rectangular coordinate system; Calculate the total arc length of the spherical baseline and determine the number of sampling points to be the smallest integer not less than the ratio of the total arc length to the unit distance; The spherical baseline is discretized at equal intervals according to the unit distance to obtain the arc length of each sampling point along the spherical baseline from point A, which is taken as the target arc length.

[0043] Further, in step S103, calculating the radar parameters corresponding to each sampling point based on the coordinate mapping relationship and the spherical trigonometric geometric relationship includes: Convert the screen coordinates of points A and B into polar coordinates in the radar polar coordinate system, and construct a spherical triangle composed of the Earth's center, the pole, and the corresponding spherical projection points of points A and B. The spherical angle at the pole of the spherical triangle is calculated using the cosine theorem of the spherical triangle. Based on the target arc length between the sampling point and point A and the spherical angle, the polar radius and azimuth of the sampling point are calculated using the sine and cosine theorems of the spherical triangle. The elevation angle and slant distance are determined based on the polar radius, azimuth, and target altitude of the sampling point.

[0044] Specifically, in this embodiment, regarding the baseline... The relationship with line AB. Figure 5 In the equation, ∠AO'B equals the dihedral angle calculated by equation (10), ∠AO'P' i The dihedral angle calculated by equation (14) is equal to Δs. i -O'P'' i When P' i When P' coincides with A and B, Δs = 0. i When it does not coincide with A and B, in triangle AO'B,

[0045]

[0046] In triangle AO'P''i

[0047]

[0048] The calculation shows that Δs > 0, meaning the baseline is... It convexes outward relative to line AB.

[0049] Furthermore, in this embodiment, the radar reflectivity factor is calculated at point P' on the vertical profile baseline. i The calculation is divided into three cases: Case 1 and Case 2 are special cases where line AB passes through O', and Case 3 is the general case.

[0050] Case 1: s a =0 or s b =0 or |θ a -θ b |=0 (8) The azimuth angle of the sampling point is θ. i .

[0051] Case 2: s a ≠0, s b ≠0, |θ a -θ b |=π (9) Case 3: s a ≠0, s b ≠0, |θ a -θ b |≠0,|θ a -θ b |≠π like Figure 6 The diagram shown is a schematic representation of the Earth's spherical triangle determined by the vertical profile baseline of the radar reflectivity factor in this embodiment, with O', A, B, and P' as the reference points. i For points O' and A(s) on the computer screen a θ a ), B(s) b θ b ), P' i (s) i θ i The projection of ) onto the Earth's surface.

[0052] Let ∠AO'B, ∠O'AB, and ∠AO'P'i represent the spherical angles in spherical triangles AO'B and AO'P'i. In spherical triangle AO'B, 10 According to the cosine formula for a spherical triangle, we have... 11 According to the sine formula for a spherical triangle, we have... 12 In spherical triangle A O'P'i, according to the cosine formula for spherical triangles, we have... 13 According to the sine formula for a spherical triangle, we have...

[0053] 14 make 12 ⒃ In equation ⒃, % represents modulo. Equations ⑻ to ⒃ give the result of A(s) a θ a ), B(s) b θ b ) and d i Calculate P' i (s) i θ i The method involves considering atmospheric refraction, and then using the Earth's equivalent radius r in the calculation. m Instead of the Earth's true radius r e Under standard atmospheric conditions, r m =4 / 3·r e .

[0054] S104. Construct a vertical profile rectangular coordinate system with the spherical baseline as the horizontal axis and the altitude as the vertical axis. Map the radar reflectivity factor of each sampling point to the vertical profile rectangular coordinate system to generate a three-dimensional cloud field vertical profile.

[0055] Further, in step S104, mapping the radar reflectivity factor of each sampling point to the vertical profile Cartesian coordinate system to generate a three-dimensional cloud field vertical profile includes: In the vertical profile rectangular coordinate system, for a grid point with the horizontal position of each sampling point as a reference, the target altitude is determined according to the ordinate of the grid point, and the two adjacent elevation layers where the target altitude is located are determined. Based on the elevation angle and slant range corresponding to the sampling point, the radar reflectivity factor observation values ​​at corresponding positions on the two adjacent elevation angle layers are obtained from the radar volume scan data. Based on the target altitude and the height difference between the two adjacent elevation layers, a vertical linear interpolation is performed to obtain the radar reflectivity factor analysis value of the grid points; the radar reflectivity factor analysis value of each grid point constitutes the three-dimensional cloud field vertical profile.

[0056] like Figure 7 The diagram shows a schematic of the Cartesian coordinate system for the vertical profile of the radar reflectivity factor in this embodiment. The Cartesian coordinate system is established with A(0,0) as the origin, the baseline determined by A and B as the horizontal axis, and the altitude h as the vertical axis. Δd represents the distance per pixel on the horizontal axis and Δd≤Δx, while Δh represents the altitude per pixel on the vertical axis. Δh is customized according to the required calculation accuracy. Since d AB / Δd is not necessarily an integer, therefore the x-coordinate is calculated up to B'(d) n ,0), where n=ceil(d AB / Δd). P' i (d) i ,0) is P' i (s) i θ i ) A point d in the Cartesian coordinate system of the vertical profile of radar reflectivity factor i =Δd×i is the value after passing through A and P' i Let P' be the arc length of the minor arc of the great circle of the Earth's surface, where i∈[0,n]. Calculate P' using equations (4) and (5). i At an elevation angle of δ j δ j+1 The coordinate P of the radar reflectivity factor vertical profile rectangular coordinate system j (d) i h j ), P j+1 (d) i h j+1 The height h j h j+1 , P(d i (h) is P j With P j+1 Any point between them.

[0057] Let Z j Z j+1 For P j P j+1 Z is the radar reflectivity factor value at point P, and Z is the radar reflectivity factor analysis value at point P.

[0058] make 14 but 18 Calculate the radar reflectivity factor at any point P(d) in the Cartesian coordinate system of the vertical profile. iThe position of A(s) in the radar polar coordinate system can be determined first by A(s). a θ a ), B(s) b θ b ) and d i Calculate P' using equations (8) to (19). i (s) i θ i Then, the elevation angle δ and slant distance r are calculated using equations (6) and (7) from h.

[0059] Figure 8 This is a schematic diagram of the reflectivity factor (PPI) at a 1.5° elevation angle for volume scan data from the Changchun radar in this embodiment. The PPI at a 1.5° elevation angle for volume scan data from the Changchun radar at 07:18 on July 4, 2010 is shown. The calculation results of the radar reflectivity factor vertical profile determined by the baseline defined by any two points A and B are as follows. Figure 9 .from Figure 9 As can be seen, the calculated radar reflectivity factor vertical profile echo intensity and spatial location are reasonable, and have good spatial continuity in both the horizontal and vertical directions.

[0060] Based on this, this embodiment proposes a computer-programmable algorithm for 3D cloud field vertical profiling of arbitrary baseline radar on the Earth's sphere. The core value of the Earth's spherical baseline lies in abandoning the simplistic assumptions of traditional planar baselines, fully considering the Earth's spherical curvature, and embedding the radar baseline into the Earth's spherical geometric model for calculation. This effectively avoids spatial distortion caused by neglecting curvature during long-range detection, significantly improving the spatial positioning accuracy and long-range detection applicability of the vertical profile. Simultaneously, the computer-programmable algorithm design has significant advantages: its streamlined and modular architecture facilitates program implementation and debugging; the mathematical models of core steps such as coordinate transformation and grid interpolation can be directly mapped to efficient code logic; and the algorithm's calculation process exhibits good repeatability and scalability, flexibly adapting to different radar parameter settings and detection scenario requirements, laying a solid foundation for subsequent engineering applications and multi-radar network collaborative processing.

[0061] To achieve accurate profile generation, this embodiment establishes a coordinate transformation relationship between the planar radar polar coordinate system unfolded from the Earth's sphere and the computer screen's rectangular coordinate system. By calculating the elevation angle, azimuth angle, and slant range of grid points in the vertical profile rectangular coordinate system of the radar reflectivity factor in the radar polar coordinate system, the radar reflectivity factor analysis value of that grid point is obtained using a vertical linear interpolation method. This algorithm demonstrates powerful performance in cloud field analysis. Addressing the key issues of complex cloud field structures and unclear precipitation mechanisms in various weather systems, it can clearly reconstruct the vertical stratification characteristics, particle concentration distribution, and dynamic evolution process of clouds, providing intuitive and accurate data support for in-depth analysis of core mechanisms such as cumulus convection development and stratigraphic cloud microphysical transformation. The high-quality vertical profile data it generates not only provides crucial three-dimensional cloud field structure information for short-term nowcasting of precipitation, improving forecast accuracy and timeliness, but also provides scientific reference for cloud water resource assessment and analysis of artificial weather modification operation conditions, contributing to the rational development and efficient utilization of cloud water resources. The accuracy of echo intensity, spatial location precision, and spatial continuity of the calculation results demonstrate that the proposed vertical profile algorithm for arbitrary baseline radar reflectivity factor on the Earth's sphere has good rationality, practicality, and engineering application value.

[0062] Secondly, this application also proposes a radar three-dimensional cloud field profile generation system based on the Earth's spherical baseline, such as... Figure 10 The system includes: Module 1001 is established to create a coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system, which is used to project radar data points onto the computer screen display interface. The determination module 1002 is used to select any two points A and B in the Cartesian coordinate system on the computer screen, and determine the minor arc of the great circle between the two points based on the geometric model of the Earth's sphere, which serves as the spherical baseline of the vertical profile of the radar reflectivity factor. The calculation module 1003 is used to select a number of sampling points at a preset interval on the spherical baseline, and calculate the radar parameters corresponding to each sampling point according to the coordinate mapping relationship and the spherical trigonometric relationship; the radar parameters include elevation angle, azimuth angle, slant range and altitude. The generation module 1004 is used to construct a vertical profile rectangular coordinate system with the spherical baseline as the horizontal axis and the altitude as the vertical axis, and to map the radar reflectivity factor of each sampling point to the vertical profile rectangular coordinate system to generate a three-dimensional cloud field vertical profile.

[0063] This system can be used to execute the radar three-dimensional cloud field profile generation method based on the Earth's spherical baseline described in the first aspect, which will not be elaborated here.

[0064] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline, characterized in that, include: Establish a coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system, which is used to project radar data points onto the computer screen display interface; Select any two points A and B in the Cartesian coordinate system on the computer screen, and determine the minor arc of the great circle between the two points based on the geometric model of the Earth's sphere, which serves as the spherical baseline of the vertical profile of the radar reflectivity factor. Several sampling points are selected at preset intervals on the spherical baseline. Based on the coordinate mapping relationship and the spherical trigonometric relationship, the radar parameters corresponding to each sampling point are calculated. The radar parameters include elevation angle, azimuth angle, slant range, and altitude. A vertical profile rectangular coordinate system is constructed with the spherical baseline as the horizontal axis and the altitude as the vertical axis. The radar reflectivity factor of each sampling point is mapped to this vertical profile rectangular coordinate system to generate a three-dimensional cloud field vertical profile.

2. The method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline according to claim 1, characterized in that, The establishment of the coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system includes: The radar polar coordinate system is established with the vertical projection of the radar antenna onto the Earth's sphere as the pole, due north as the polar axis, the arc length of the sphere as the polar radius, and the azimuth angle as the polar angle. Using the projection of the pole on the computer screen as the origin, a rectangular coordinate system for the computer screen is established, and the distance represented by a unit pixel is determined. A coordinate transformation relationship between the radar polar coordinate system and the computer screen rectangular coordinate system is then established.

3. The method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline according to claim 2, characterized in that, Establishing the coordinate transformation relationship between the radar polar coordinate system and the computer screen rectangular coordinate system includes: ； Where (x,y) are the coordinates in the Cartesian coordinate system of the computer screen, and (s,θ) are the polar radius and azimuth angle in the radar polar coordinate system, where s is the polar radius and θ is the polar angle; (x o' y o' ) represents the coordinates of the pole in the screen coordinate system, and Δx and Δy represent the distance represented by a unit pixel.

4. The method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline according to claim 1, characterized in that, The determination of the minor arc of the great circle between two points based on the Earth's spherical geometry model includes: Convert the screen coordinates of points A and B to polar coordinates in the radar polar coordinate system; Based on the polar radius and azimuth of points A and B, the central angles corresponding to the two points on the Earth's surface are calculated using spherical trigonometric relationships. The arc length of the minor arc of the great circle is determined by multiplying the central angle by the Earth's radius.

5. The method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline according to claim 1, characterized in that, The spherical trigonometric relationships include: Construct a spherical triangle consisting of the Earth's center, the poles, and the corresponding spherical projection points of points A and B; The spherical angles of the spherical triangle are calculated using the cosine theorem of the spherical triangle, and the azimuth relationship between the sampling point and point A is determined using the sine theorem of the spherical triangle. For each sampling point, based on the target arc length between the sampling point and point A, and combined with the relationship between the spherical angle and azimuth angle, the polar radius of the sampling point is calculated using the cosine theorem of the spherical triangle, and the azimuth angle of the sampling point is calculated using the sine theorem of the spherical triangle.

6. The method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline according to claim 5, characterized in that, The calculation of the azimuth angle of the sampling point using the sine theorem for spherical triangles includes: When the polar radius of point A is zero, the target arc length is taken as the polar radius of the sampling point, and the azimuth of the sampling point is equal to the azimuth of point A; When the polar radius of point B is zero, the polar radius of the sampling point is determined to be equal to the difference between the polar radius of point A and the target arc length, and the azimuth of the sampling point is equal to the azimuth of point A. When the difference between the azimuth angles of points A and B is zero, the polar radius of the sampling point is determined to be equal to the sum of the polar radius of point A and the target arc length, and the azimuth angle of the sampling point is equal to the azimuth angle of point A. When the polar radii of points A and B are both non-zero and the difference in azimuth angles is π, the polar radii of the sampling point are determined according to the linear sum-difference relationship between the polar radii of point A and the target arc length, and the azimuth angle of the sampling point is equal to the azimuth angle of point A or the azimuth angle of point B.

7. The method according to claim 1, characterized in that, The step of selecting a number of sampling points at preset intervals on the spherical baseline includes: Set the unit distance of the abscissa of the vertical profile rectangular coordinate system, and the unit distance is not greater than the unit pixel distance of the computer screen rectangular coordinate system; Calculate the total arc length of the spherical baseline and determine the number of sampling points to be the smallest integer not less than the ratio of the total arc length to the unit distance; The spherical baseline is discretized at equal intervals according to the unit distance to obtain the arc length of each sampling point along the spherical baseline from point A, which is taken as the target arc length.

8. The method according to claim 7, characterized in that, The step of calculating the radar parameters corresponding to each sampling point based on the coordinate mapping relationship and the spherical trigonometric relationship includes: Convert the screen coordinates of points A and B into polar coordinates in the radar polar coordinate system, and construct a spherical triangle composed of the Earth's center, the pole, and the corresponding spherical projection points of points A and B. The spherical angle at the pole of the spherical triangle is calculated using the cosine theorem of the spherical triangle. Based on the target arc length between the sampling point and point A and the spherical angle, the polar radius and azimuth of the sampling point are calculated using the sine and cosine theorems of the spherical triangle. The elevation angle and slant distance are determined based on the polar radius, azimuth, and target altitude of the sampling point.

9. The method for generating a three-dimensional radar cloud field profile based on the Earth's spherical baseline according to claim 1, characterized in that, The step of mapping the radar reflectivity factor of each sampling point to the Cartesian coordinate system of the vertical profile to generate a three-dimensional cloud field vertical profile includes: In the vertical profile rectangular coordinate system, for a grid point with the horizontal position of each sampling point as a reference, the target altitude is determined according to the ordinate of the grid point, and the two adjacent elevation layers where the target altitude is located are determined. Based on the elevation angle and slant range corresponding to the sampling point, the radar reflectivity factor observation values ​​at corresponding positions on the two adjacent elevation angle layers are obtained from the radar volume scan data. Based on the target altitude and the height difference between the two adjacent elevation layers, a vertical linear interpolation is performed to obtain the radar reflectivity factor analysis value of the grid points; the radar reflectivity factor analysis value of each grid point constitutes the three-dimensional cloud field vertical profile.

10. A radar three-dimensional cloud field profile generation system based on the Earth's spherical baseline, characterized in that, include: The module is used to establish the coordinate mapping relationship between the radar polar coordinate system under the Earth's spherical projection and the computer screen rectangular coordinate system, which is used to project radar data points onto the computer screen display interface. The determination module is used to select any two points A and B in the Cartesian coordinate system on the computer screen, and determine the minor arc of the great circle between the two points based on the geometric model of the Earth's sphere, which serves as the spherical baseline of the vertical profile of the radar reflectivity factor. The calculation module is used to select a number of sampling points at preset intervals on the spherical baseline, and calculate the radar parameters corresponding to each sampling point according to the coordinate mapping relationship and the spherical trigonometric relationship; the radar parameters include elevation angle, azimuth angle, slant range and altitude. The generation module is used to construct a vertical profile rectangular coordinate system with the spherical baseline as the horizontal axis and the altitude as the vertical axis, and to map the radar reflectivity factor of each sampling point to the vertical profile rectangular coordinate system to generate a three-dimensional cloud field vertical profile.

Images