Dual-radar three-dimensional wind field inversion method considering the influence of standard atmosphere

Abstract

The present invention discloses a dual-radar three-dimensional wind field inversion method considering the influence of the standard atmosphere in the Earth coordinate system. The method is as follows: First, perform the conversion of the polar coordinates of the radar radial observation to the longitude-latitude grid coordinates. Then, convert the inversion grid target points from the longitude-latitude grid coordinates to the Earth coordinate system to obtain the position coordinates of the inversion grid target points and the two radars in the Earth coordinate system. Finally, perform the dual-radar wind field inversion considering the influence of the standard atmosphere in the Earth coordinate system. In the inversion wind field iteration equations, consider the influence of the standard atmosphere on the radial velocity projection of the three-dimensional wind field of the inversion grid target points. At the same time, consider the influence of the density change on the mass continuity equation under the condition of considering the standard atmosphere, so as to achieve the accurate calculation of the dual-radar three-dimensional wind field inversion and obtain accurate and reliable three-dimensional wind field inversion information. Based on the method of the present invention, the accurate calculation of the dual-radar three-dimensional wind field inversion can be realized, and relatively accurate and reliable wind field information values can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of atmospheric remote sensing monitoring and analysis, and relates to a three-dimensional wind field inversion method of a dual Doppler weather radar, and specifically to a dual radar three-dimensional wind field inversion method considering the influence of a standard atmosphere in an earth coordinate system. Background Art

[0002] Three-dimensional wind field data are very important for disastrous weather monitoring, numerical forecasting and model verification, as well as mesoscale weather dynamics analysis. Radar, as an effective means of observation for mesoscale and small-scale weather monitoring, can obtain radial velocity information along the direction of the radar antenna. However, this velocity information lacks intuitiveness, and a single radar cannot reflect the true vector velocity of precipitation particles.

[0003] With the development and maturity of radar wind field inversion technology, the application of dual-radar wind field inversion is becoming more and more extensive. The radial velocities observed by two Doppler weather radars are synthesized, and the real three-dimensional wind field information of precipitation echoes can be inverted with the help of relevant assumptions and equations.

[0004] However, most algorithms are calculated in the Cartesian coordinate system, ignoring the influence of the earth's surface as a spherical surface, and not considering the accuracy of the position calculation of the long-distance radar beam. This has a great impact on the wind field inversion analysis of distant weather systems, and it is also difficult to realize the networking application of wind field inversion. In order to ensure the accuracy and applicability of wind field inversion, the patent "A method for three-dimensional wind field inversion of dual Doppler radars" uses a dynamic earth coordinate system and equal longitude and latitude and equal altitude grids for dual radar wind field inversion. This method not only realizes the accurate calculation of the influence of the earth's curved surface, but also facilitates the networking analysis of wind field products and comprehensive analysis with other products. In addition, since the atmosphere is not a uniform fluid, the electromagnetic waves emitted by the radar do not propagate in a straight line under different atmospheric density distributions, but propagate in a curve formed by multiple refractions. Therefore, when calculating the precise position of the radar storage point, it is necessary to consider the influence of its curved propagation, and it is necessary to consider the influence of standard atmospheric refraction on the projection of the inverted wind field in the direction of electromagnetic wave propagation in the dual radar inversion formula. The patent "A method for inverting three-dimensional wind fields using dual Doppler radars" only considers the change in the projection coefficient of the vertical velocity of the target point, but does not calculate the change in the projection coefficient of the horizontal velocity of the target point. In addition, there are some problems in the derivation formula of the projection coefficient of the vertical velocity, and the final calculation formula is quite complicated.

[0005] In addition, if the background of standard atmospheric influence conditions is taken into account, it is also necessary to calculate the approximate change of density with height in the continuity equation, so as to finally achieve the accurate calculation of radar three-dimensional wind field inversion and obtain accurate and reliable inverted wind field information values. However, previous inversion algorithms and the patent "A Dual Doppler Radar Three-Dimensional Wind Field Inversion Method" directly ignore the spatial changes of density. Summary of the invention

[0006] A method for retrieving three-dimensional wind field from dual radars considering the influence of standard atmosphere in the earth coordinate system. This method takes into account the influence of the earth's curvature and standard atmosphere, strictly derives the conversion formula from the polar coordinates of radar radial observation to the longitude-latitude grid coordinates, and the conversion formula from the longitude-latitude grid coordinates to the earth coordinate system, and calculates the accurate positions of the retrieved grid target points of the two radars. In the calculation formula for retrieving the dual-radar wind field, the influence of atmospheric standard refraction on the radial velocity projection of the three-dimensional wind field of the retrieved grid target points is considered, and the projection coefficient of the three-dimensional wind field of the retrieved target points on the true radial velocity (tangential direction of the electromagnetic wave propagation curve) is derived. In addition, considering the influence of density change on the mass continuity equation under the condition of standard atmosphere influence, the density variation term with height is added, and finally, the accurate calculation of radar three-dimensional wind field retrieval can be realized, and accurate and reliable wind field information values can be obtained.

[0007] The technical solution adopted by the present invention is as follows:

[0008] First, perform the conversion from the polar coordinates of radar radial observation to the longitude-latitude grid coordinates, which specifically includes the following steps:

[0009] 1) Read the longitude, latitude, altitude of the radar location, and the radial velocity-related information from the radar base data. The radial velocity-related information specifically includes: the radial velocity value, the azimuth angle, elevation angle, range bin order, and range bin resolution of the radial velocity. Similarly, read the reflectivity-related information. The reflectivity-related information includes the reflectivity value, the azimuth angle, elevation angle, range bin order, and range bin resolution of the reflectivity.

[0010] 2) Under the condition of considering the influence of standard atmosphere, according to the radial velocity-related information or the reflectivity-related information, using the altimetry formula (1), the height H of the observation bin point from the ground can be obtained:

[0011] (1)

[0012] Where h is the height of the radar antenna (i.e., the height of the radar location), δ is the elevation angle of the radial velocity or reflectivity, R is the slant range (obtained by multiplying the range bin order Num of the radial velocity or reflectivity by the range bin resolution dpl_reso), and H is the height of the center axis of the radar beam from the ground at the slant range R; R m is the equivalent radius of the earth, which is m times of the true earth radius R times, about 8500 km.

[0013] 3) Calculate the distance R CB between the observation bin point P1 and the radar A on the ground. C and B are respectively the projections of the observation bin point P1 and the radar A on the earth:

[0014] (2)

[0015] Among them, is , and it can be obtained by using the cosine theorem formula of triangle AO . O is the center of the earth.

[0016] 4) Now, the longitude rlon and latitude rlat of point B are known, the spherical distance from point C to point B, and the azimuth Azim (the azimuth corresponding to the radial velocity or reflectivity) between point C and point B. The spherical cosine theorem and sine theorem in the spherical triangle formed by the North Pole N and points C and B can be used to obtain the latitude and longitude of point C. This also obtains the longitude , latitude , and altitude value +H of the observed library point P1.

[0017] 5) Using the longitude, latitude, and altitude values of the observed library points, interpolate the volume scan data values (including reflectivity and radial velocity) of all observed library points to the equal longitude-latitude and equal altitude grid target points to be inverted. The cressman distance weight interpolation method is used in the horizontal direction, and linear interpolation is used in the vertical direction, so as to obtain the reflectivity and radial velocity values of the inverted grid target points.

[0018] Then, convert the inverted grid target points from the longitude-latitude grid coordinates to the earth coordinate system to obtain the position coordinates of the inverted grid target points and the two radars in the earth coordinate system. The specific method is as follows:

[0019] The origin of the earth coordinate system is set at the center of the earth. The z-axis passes through the inverted grid target point P and points to the zenith. The x-axis points to the due east direction of point P, and the y-axis points to the due north direction of point P. The coordinate system is not fixed and changes with the change of the inverted grid target point, so it is called the dynamic earth coordinate system.

[0020] In the longitude-latitude grid coordinates, the longitude lon, latitude lat, and altitude value H of the inverted grid target point P are known. The longitude rlon, latitude rlat, and altitude value h of radar A1 / A2.

[0021] Then, in the earth coordinate system, the coordinates of point P are P(0, 0, R m +H).

[0022] According to the longitudes, latitudes, and altitudes of two radars under the longitude-latitude grid coordinates and the position coordinates of the inversion grid target points in the Earth coordinate system, the position coordinates of the two radars in the Earth coordinate system are calculated respectively by the cosine theorem and sine theorem of spherical trigonometry. The specific method is as follows:

[0023] Set the coordinates of point P as P(0, 0, z), and the coordinates of point A1 of radar A( , , ) Then, the cosine theorem and sine theorem of spherical trigonometry of spherical triangle CNA1 can be used to obtain, where N is the North Pole. The coordinates of point A2 of radar A( , , ) Similarly, it can be obtained by the cosine theorem and sine theorem of spherical trigonometry of spherical triangle CNA2. Using A to replace A1 and A2, the cosine theorem and sine theorem of spherical trigonometry of spherical triangle CNA are shown in formulas (3)-(7).

[0024] + (3)

[0025] z1 = (4)

[0026] (5)

[0027] x1 = (6)

[0028] y1 = (7)

[0029] Among them, 、 、 are the radian corresponding to the arc length between points C and A on the sphere, the radian corresponding to the arc length between points N and A on the sphere, and the radian corresponding to the arc length between points N and C on the sphere, respectively.

[0030] Finally, consider the standard atmosphere influence in the Earth coordinate system for the dual-radar wind field inversion. Construct an iterative equation system for the inversion wind field according to the reflectivity and radial velocity of the inversion grid target points; consider the influence of the standard atmosphere on the projection of the three-dimensional wind field of the inversion grid target points on the radial velocity in the iterative equation system of the inversion wind field, and deduce the projection coefficients of the vertical and horizontal velocities of the inversion grid target points in the radial velocity direction; at the same time, consider the influence of density change on the mass continuity equation under the condition of standard atmosphere influence, so as to realize the accurate calculation of the radar three-dimensional wind field inversion and obtain accurate and reliable three-dimensional wind field inversion information.

[0031] A1 and A2 are the locations of two radars. From the above calculations, in the Earth coordinate system, their coordinates are respectively ( , , ), ( , , ), and the coordinates of point P are P(0, 0, z). V r1 and V r2 are the radial velocities of the two radars at point P respectively. Let the three-dimensional velocity components of point P be u, v, and w. Then the iterative equations for wind field inversion are:

[0032] (8)

[0033] (9)

[0034] (10)

[0035] (11)

[0036] where is the terminal velocity of the precipitation particles falling in the stationary atmosphere.

[0037] However, the above wind field iterative equation does not consider the influence of the standard atmosphere, that is, it is assumed that the electromagnetic wave propagates in a straight line, and the direction of the radial velocity is from the inversion grid target point to the radar.

[0038] However, under the influence of atmospheric refraction, the electromagnetic wave propagates in a curved path rather than a straight line. The direction of the radial velocity of the inversion grid target point P is actually the tangential direction of the curved curve. Therefore, the projection of (u, v, w) in the direction of the radial velocity changes. Previously, it was projected in the direction of the straight line AP, but actually it should be projected in the tangential direction of the curved curve.

[0039] The calculation method of the projection coefficient of the vertical velocity w in the direction of the radial velocity is to use ( ) to replace the represented by the original That's it. , and now it is necessary to obtain the magnitude of . Since the arc of AP is the propagation path under the influence of the standard atmosphere, according to the standard atmospheric refraction parameter table of Zhang Peichang et al. (2012), it can be known that the curvature of the propagation path is -4×10 -5 km -1, where \(n\) represents the refractive index of the standard atmospheric medium, \(h\) represents the height, and the entire term \(dn / dh\) represents the variation of the refractive index with height. From this, the corresponding radius \(R\) of the propagation curve can be known. n is 25000 km, and in the isosceles triangle A P, it can be obtained. ( ), and the magnitude of can be obtained. Thus, the value can be obtained. Specifically, for the radar at point A1, the point is the center of the circle of the propagation curve path A1P; in the isosceles triangle A1 P, A1P is obtained; the straight line L1L2 is the tangent of the propagation curve path A1P, so A1PL1 can be obtained; in the triangle A1OP, according to the cosine theorem of triangles, A1PO can be obtained; according to A1PL1 and A1PO, L1PO can be obtained. Abbreviate L1PO as θ1, so as to obtain the projection coefficient cosθ1 of the vertical velocity w of the inversion grid target point on the radial velocity; similarly, for the radar at point A2, the projection coefficient cosθ2 of the vertical velocity w of the inversion grid target point P on the radial velocity direction can be calculated;

[0040] The calculation of the projection coefficients of the horizontal velocities u and v in the radial velocity direction is relatively complicated. Taking the v component as an example, the calculation process will be described in detail.

[0041] For the radar at point A1, if the influence of atmospheric refraction is not considered, it is projected on the blue straight line, which is the projection coefficient of this component. Now it needs to be projected on the tangent of the curved curve. A plane perpendicular to PO is made through point A1, and point D is the intersection of the plane and PO. There is a point E in the due north direction of A1 and the length of A1E is y1. The intersection of the straight line L1L2 and the plane is point G, is equal to L1PO. The straight line in the due north direction passing through point G intersects the straight line ED at point F. Let the coordinates of point G be ( , , ), then the current projection coefficient is . From the similar triangles A1ED and triangle GFD, it can be obtained that:

[0042] (12)

[0043] Similarly for the u component, the projection coefficient is: (13)

[0044] Similarly, for the radar at point A2, we can obtain:

[0045] The projection coefficients of the horizontal velocity v and u of the inversion grid target point P on the radial velocity can be obtained as: and .

[0046] Therefore, after considering the influence of the standard atmosphere, equations (8) - (11) (i.e., the inversion wind field iterative equations) should be changed to:

[0047] (14)

[0048] (15)

[0049] where, and are the radial velocities of the two radars at the inversion grid target point after considering the influence of the standard atmosphere, respectively; is the terminal velocity of the precipitation particles falling in the static atmosphere, which is estimated using the reflectivity I of the inversion grid target point:

[0050] (16)

[0051] To solve the inversion wind field iterative equations, the vertical velocity w needs to be calculated through the mass continuity equation:

[0052] (17)

[0053] and w satisfies:

[0054] (18)

[0055] where z0 represents the height of the grid point one layer below the lowest effective interpolation point of the inversion grid target point.

[0056] Furthermore, considering the influence of density changes on the mass continuity equation under the condition of the standard atmosphere influence, specifically:

[0057] In the case of deep convection, the mass continuity equation can use the anelastic approximation (Ogura and Phyllips, 1962), ignoring the influence of density perturbations , and based on scale analysis, omitting the density changes in the horizontal direction, then the mass continuity equation (17) is changed to:

[0058] (19)

[0059] Under standard atmospheric influence conditions, the density varies with height, as shown in Equation (20), which can be substituted into Equation (19). That is, the standard atmospheric influence is also considered in the mass continuity equation.

[0060] (20)

[0061] where Z is the height in meters; is the atmospheric density at mean sea level, approximately 1.2 kg / m 3 .

[0062] Thus, the accurate calculation of radar three-dimensional wind field inversion can be achieved as follows: After giving the initial values of u and v, the first estimated value of w can be obtained using the mass continuity equation (19). Then, substitute w into the inversion wind field iteration equations (14) and (15) to recalculate u, v, and w. Through several iterations, when the difference between the data of the two inversion calculations before and after is less than a given minimum value (such as 0.0001 m / s), the three-dimensional wind field inversion result (u, v, w) that meets the accuracy can be obtained.

[0063] The present invention also provides a dual-radar three-dimensional wind field inversion device considering standard atmospheric influence, which includes:

[0064] A coordinate transformation module 1, which is used to interpolate the reflectivity and radial velocity of all observed grid points in polar coordinates observed by the radar to the target points of the equal longitude and latitude, equal height grid to be inverted, and obtain the reflectivity and radial velocity values of the inversion grid target points in the longitude and latitude grid coordinates;

[0065] A coordinate transformation module 2, which is used to transform the inversion grid target points from the longitude and latitude grid coordinates to the Earth coordinate system, and obtain the position coordinates of the inversion grid target points and the two radars in the Earth coordinate system;

[0066] A dual-radar wind field inversion module considering standard atmospheric influence in the Earth coordinate system, which is used to construct an inversion wind field iteration equation set according to the reflectivity and radial velocity of the inversion grid target points; consider the influence of standard atmospheric influence on the projection of the three-dimensional wind field of the inversion grid target points on the radial velocity, and deduce the projection coefficients of the vertical and horizontal velocities of the inversion grid target points in the radial velocity direction; at the same time, consider the influence of density change under standard atmospheric influence conditions on the mass continuity equation, so as to achieve the accurate calculation of radar three-dimensional wind field inversion and obtain accurate and reliable three-dimensional wind field inversion information.

[0067] The present invention also provides an electronic device, including: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the dual-radar three-dimensional wind field inversion method considering the influence of the standard atmosphere.

[0068] The present invention also provides a computer-readable storage medium, on which computer instructions are stored, and the computer instructions are used to cause a computer to execute the dual-radar three-dimensional wind field inversion method considering the influence of the standard atmosphere.

[0069] The beneficial effects of the present invention are as follows:

[0070] (1) The present invention considers the influence of the earth's curved surface and the standard atmosphere, strictly derives the conversion formula from the polar coordinates of radar radial observations to the longitude-latitude grid coordinates, and the conversion formula from the longitude-latitude grid coordinates to the earth coordinate system, and can accurately calculate the positions of the two radars and the inversion grid target points.

[0071] (2) The influence of atmospheric refraction is considered in the dual-radar wind field inversion equation set, and the projection coefficient of the three-dimensional wind field of the inversion grid target point on the true radial velocity (tangential direction of the electromagnetic wave propagation curve) is derived, and the three-dimensional wind field can be inverted more accurately.

[0072] (3) In addition, the influence of the standard atmosphere is considered in the mass continuity equation, and the density variation term with height is added, and finally the accurate calculation of the radar three-dimensional wind field inversion can be realized, and more accurate and reliable wind field information values can be obtained.

[0073] (4) The inversion results of the method of the present invention are evaluated and tested using the second-level sounding data for a long time series, and it is found that the root mean square error is about 3.5 m / s. Description of the Drawings

[0074] Figure 1 is a schematic diagram for solving the height of the radar observation point under the equivalent earth radius;

[0075] Figure 2 is a schematic diagram for converting the longitude-latitude grid coordinates to the earth coordinate system;

[0076] Figure 3 is a schematic diagram for the dual-radar wind field inversion without considering atmospheric refraction;

[0077] Figure 4 is a schematic diagram for the radar electromagnetic wave propagation considering the influence of the standard atmosphere;

[0078] Figure 5 is a schematic diagram for the radar radial velocity direction considering the influence of the standard atmosphere in the earth coordinate system. Detailed Embodiments

[0079] The solution of the present invention will be further described and explained below with reference to the accompanying drawings.

[0080] An embodiment of the present invention provides a dual-radar three-dimensional wind field inversion method considering the influence of the standard atmosphere, which specifically includes the following steps:

[0081] First, perform the conversion from the polar coordinates of the radar radial observation to the longitude and latitude grid coordinates.

[0082] Read the longitude, latitude, altitude of the radar location, and the radial velocity-related information from the radar base data. The radial velocity-related information specifically includes: the radial velocity value, the azimuth angle, elevation angle, range bin order, and range bin resolution of the radial velocity. Similarly, read the reflectivity-related information. The reflectivity-related information includes the reflectivity value, the azimuth angle, elevation angle, range bin order, and range bin resolution of the reflectivity.

[0083] As Figure 1 shown, O is the center of the earth, R m is the true radius of the earth, A and P1 are the radar and the observation bin point respectively, B and C are the projections of the radar A and the observation bin point P1 on the earth respectively, O1 is the center of the equivalent earth, and C P1 is the schematic of the equivalent length of CP1 under the equivalent radius of the earth; is the equivalent radius of the earth.

[0084] Under the condition of considering the influence of the standard atmosphere, according to the radial velocity-related information or the reflectivity-related information, using the altimetry formula (1), the height H of the observation bin point from the ground can be obtained, that is, Figure 1 the C P1 length in.

[0085] (1)

[0086] where h is the height of the radar antenna (i.e., the height of the radar location), δ is the elevation angle of the radial velocity or reflectivity, R is the slant range (i.e., the straight-line distance between points AP1 and also the straight-line distance between points AP1, that is, the range bin order Num of the radial velocity or reflectivity multiplied by the range bin resolution dpl_reso), H is the height of the center axis of the radar beam from the ground at the slant range R, and R m is, the true radius of the earth R m times of, about 8500 km. times, about 8500 km.

[0087] Then, the distance R CB between the observation bin point P1 and the radar A on the ground can be calculated as:

[0088] (2)

[0089] Among them, is , using the cosine theorem formula of triangle AOP1, we can get (where = + h; = + H).

[0090] (3)

[0091] Now, the longitude rlon and latitude rlat of point B are known, the spherical distance from point C to point B, and the azimuth Azim (the azimuth corresponding to the radial velocity or reflectivity) between point C and point B. Using the spherical cosine theorem and sine theorem in the spherical triangle formed by the North Pole N and points C and B, we can obtain the latitude of point C and the longitude .

[0092] Spherical cosine theorem:

[0093] + (4)

[0094] (5)

[0095] (6)

[0096] Among them, , , are the radian corresponding to the arc length between points N and C on the sphere, the radian corresponding to the arc length between points N and B on the sphere, and the radian corresponding to the arc length between points B and C on the sphere, respectively.

[0097] Spherical sine theorem:

[0098] (7)

[0099] (8)

[0100] This also obtains the longitude , latitude , and altitude value + H of the observation library point .

[0101] Then, using the longitude, latitude, and altitude values of the observation library points, the volume scan data values (reflectivity, radial velocity) of all observation library points can be interpolated to the equal longitude - latitude and equal - altitude grid target points to be inverted. The cressman distance - weighted interpolation method is used in the horizontal direction, and linear interpolation is used in the vertical direction, so as to obtain the reflectivity and radial velocity values at the inversion target grid points under the longitude - latitude grid coordinates.

[0102] Then, it is necessary to convert the inversion grid target points from the longitude - latitude grid coordinates to the Earth coordinate system to obtain the coordinates of the inversion grid target points and the two radars in the Earth coordinate system.

[0103] As Figure 2 shown, the origin O of the Earth coordinate system is set at the center of the Earth. The z - axis points to the zenith through the inversion grid target point P, the x - axis points to the due east direction of point P, and the y - axis points to the due north direction of point P. The coordinate system is not fixed and it changes with the inversion target point, so it is called a dynamic Earth coordinate system.

[0104] Under the longitude - latitude grid coordinates, the longitude lon, latitude lat, and altitude value H of the grid target point P to be inverted are known. The longitude rlon, latitude rlat, and altitude value h of the radars A1 / A2 are also known.

[0105] Then, under the Earth coordinate system, the coordinates of point P are P(0, 0, R m +H), denoted as P(0, 0, z), and the coordinates of point A1( , , ) can be obtained by the spherical - triangle cosine theorem and sine theorem of spherical triangle CNA1, where N is the North Pole. The coordinates of point A2( , , ) can be obtained in the same way by the spherical - triangle cosine theorem and sine theorem of spherical triangle CNA2. Using A to replace A1 and A2, the spherical - triangle cosine theorem and spherical - triangle sine theorem of spherical triangle CNA are specifically shown in formulas (9) - (15).

[0106] Spherical - triangle cosine theorem:

[0107] NA (9)

[0108] That is: (10)

[0109] (11)

[0110] Among them, 、 , They are respectively the arc length between two points C and A on the spherical surface, the arc length between two points N and A on the spherical surface, and the arc length between two points N and C on the spherical surface.

[0111] The sine theorem of spherical trigonometry:

[0112] (12)

[0113] That is: (13)

[0114] x1 = (14)

[0115] y1 = (15)

[0116] Finally, consider the dual-radar wind field inversion considering the influence of the standard atmosphere in the Earth coordinate system.

[0117] As Figure 3 shown, A1 and A2 are the positions of the two radars. From the above calculations, in the Earth coordinate system, their coordinates are respectively ([[]] , , ), ([[]] , , ), and the coordinates of point P are P(0, 0, z), V r1 , V r2 are respectively the radial velocities of the two radars at point P. Let the three-dimensional velocity components of point P be u, v, and w, then the wind field iteration equation set is:

[0118] (16)

[0119] (17)

[0120] (18)

[0121] (19)

[0122] Among them, is the terminal velocity of the precipitation particles falling in the stationary atmosphere.

[0123] The above wind field iteration equation does not consider the influence of the standard atmosphere. As Figure 3 shown by the two blue lines, that is, assuming that the electromagnetic wave propagates in a straight line, the direction of the radial velocity is from the inversion grid target point to the radar.

[0124] However, under the influence of the standard atmosphere, the electromagnetic wave propagates in a curved path rather than a straight line. The radial velocity direction of the inversion grid target point P is actually the tangential direction of the curved line, that is, Figure 4 the tangential direction shown by the gray straight line L1L2 in Figure 4 . Replace A1 and A2 with A in Figure 4 , and the calculation method of the projection coefficient of the vertical velocity of the inversion grid target point on the radial velocity is described in detail. Therefore, the projection of (u, v, w) in the radial velocity direction changes. Previously, it was projected in the direction of the straight line AP, but in fact, it should be projected in the tangential direction of the gray line L1L2.

[0125] The calculation method of the projection coefficient of the vertical velocity w in the radial velocity direction is as follows:

[0126] Use ( ) to replace what the original this term represents and that's it. , and now we need to obtain the magnitude of . Since the AP arc is the propagation path under the influence of the standard atmosphere, according to the standard atmospheric refraction parameter table of Zhang Peichang et al. (2012), the curvature of the propagation path is -4×10 -5 km -1 . Here, n represents the refraction index of the standard atmospheric medium, h represents the height, and the whole term dn / dh represents the change of the refraction index with height. From this, the corresponding radius R n of this propagation curve is 25000 km. In the isosceles triangle A P, the magnitude of ( ) can be obtained, and thus the magnitude of is obtained. From this, the value can be obtained.

[0127] The calculation method of the projection coefficients of the horizontal velocities u and v in the radial velocity is as follows:

[0128] Taking the v component as an example, as Figure 5 shows, if the influence of atmospheric refraction is not considered, it is projected on the blue straight line, which is the projection coefficient of this component. Now it needs to be projected on the gray tangent line (i.e., the tangent of the curved line). Let the coordinates of point G be ( , , ), then the current projection coefficient is Point E is due north of A1, and the length of A1E is y1. The plane A1ED is perpendicular to the Z-axis. Point D is the intersection of the plane A1ED and PO, and point G is the intersection of the gray tangent line and the plane A1ED. That is, θ1. From the similar triangles A1ED and GFD, we can obtain:

[0129] (20)

[0130] Therefore: (21)

[0131] (22)

[0132] Then: (23)

[0133] That is: (24)

[0134] Among them, 、 、 、 、 、 are the distance between point G and point F, the distance between point A1 and point E, the distance between point G and point D, the distance between point A1 and point D, the distance between point D and point P, and the distance between point G and point P respectively;

[0135] Similarly for the u component, the projection coefficient is: (25)

[0136] Similarly, for the radar at point A2, we can obtain:

[0137] The projection coefficients of the horizontal velocity v and u of the inversion grid target point P on the radial velocity are respectively: and .

[0138] Therefore, considering the influence of the standard atmosphere, equations (16)-(19) can be changed to (26) and (27). Equations (26) and (27) are the iterative equations of the inversion wind field considering the influence of the standard atmosphere:

[0139] (26)

[0140] (27)

[0141] Among them, and are the radial velocities of the two radars at the inversion grid target point considering the influence of the standard atmosphere respectively; The terminal velocity of precipitation particles falling in a stationary atmosphere is estimated by using the reflectivity I of the inversion grid target points:

[0142] (28)

[0143] To solve the iterative equations (26) and (27) of the inversion wind field, the vertical velocity w is calculated using the mass continuity equation:

[0144] (29)

[0145] And w needs to satisfy:

[0146] (30)

[0147] Among them, z0 represents the height of the grid point in the layer below the lowest effective interpolation point of the inversion grid target point.

[0148] Considering the influence of density change on the mass continuity equation under the standard atmospheric influence conditions, specifically:

[0149] In the case of deep convection, the mass continuity equation uses the anelastic approximation (Ogura and Phyllips, 1962), ignoring the influence of density perturbation , and based on scale analysis, the density change in the horizontal direction is omitted, then the mass continuity equation (29) is changed to:

[0150] (31)

[0151] Under the standard atmosphere, the density varies with height. The specific calculation method is shown in formula (32), and it can be substituted into formula (31) for calculation, that is, the standard atmospheric influence is also considered in the mass continuity equation.

[0152] (32)

[0153] Among them, Z is the height, with the unit of m, is the atmospheric density at the mean sea level, about 1.2 kg / m 3 .

[0154] For the accurate calculation of radar three-dimensional wind field inversion, the specific method is as follows: First, given the initial values of u and v, the first estimated value of w can be obtained by using the mass continuity equation (31). Then, substitute w into the equations (26) and (27) to recalculate u, v, and w. Through several iterations, when the difference between the data of the two inversion calculations before and after is less than the given minimum value of 0.0001 m / s, the three-dimensional wind field inversion result (u, v, w) that meets the accuracy can be obtained.

[0155] In the dual-radar wind field inversion experiment, based on the above method, long-term sequence evaluation and verification were carried out using second-level sounding data, and it was found that the root mean square error was about 3.5 m / s, and the inversion results were relatively reliable.

[0156] Another embodiment of the present invention provides a dual-radar three-dimensional wind field inversion device considering the influence of the standard atmosphere. The device includes:

[0157] A coordinate transformation module one, configured to interpolate the reflectivity and radial velocity of all observed library points in polar coordinates observed by the radar to the target points of the equi-longitude, equi-height grid to be inverted, and obtain the reflectivity and radial velocity values of the inversion grid target points in the longitude-latitude grid coordinates;

[0158] A coordinate transformation module two, configured to transform the inversion grid target points from the longitude-latitude grid coordinates to the Earth coordinate system, and obtain the position coordinates of the inversion grid target points and the two radars in the Earth coordinate system;

[0159] A dual-radar wind field inversion module considering the influence of the standard atmosphere in the Earth coordinate system, configured to construct an iterative equation system for the inversion wind field according to the reflectivity and radial velocity of the inversion grid target points; consider the influence of the standard atmosphere on the projection of the three-dimensional wind field of the inversion grid target points on the radial velocity, and deduce the projection coefficients of the vertical and horizontal velocities of the inversion grid target points in the radial velocity direction; at the same time, consider the influence of density change on the mass continuity equation under the condition of considering the standard atmosphere, so as to realize the accurate calculation of the radar three-dimensional wind field inversion and obtain accurate and reliable three-dimensional wind field inversion information.

[0160] Another embodiment of the present invention also provides an electronic device, including: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the dual-radar three-dimensional wind field inversion method considering the influence of the standard atmosphere.

[0161] Another embodiment of the present invention also provides a computer-readable storage medium, on which computer instructions are stored, and the computer instructions are used to cause a computer to execute the dual-radar three-dimensional wind field inversion method considering the influence of the standard atmosphere.

Claims

1. A dual-radar three-dimensional wind field inversion method considering the influence of standard atmosphere, characterized in that It includes the following steps: First, perform the conversion of polar coordinates of radar radial observations to longitude-latitude grid coordinates: Interpolate the reflectivity and radial velocity of all observation bin points in polar coordinates of radar radial observations to the longitude-latitude and height grid target points to be inverted, and obtain the reflectivity and radial velocity values of the inverted grid target points in longitude-latitude grid coordinates; Next, convert the inverted grid target points from longitude-latitude grid coordinates to the Earth coordinate system to obtain the position coordinates of the inverted grid target points and the two radars in the Earth coordinate system; Finally, perform dual-radar wind field inversion considering the influence of the standard atmosphere in the Earth coordinate system: Construct an iterative equation system for the inverted wind field based on the reflectivity and radial velocity of the inverted grid target points; Consider the influence of the standard atmosphere on the projection of the three-dimensional wind field of the inverted grid target points on the radial velocity, and deduce the projection coefficients of the vertical and horizontal velocities of the inverted grid target points in the radial velocity direction, so as to determine the iterative equation system of the inverted wind field considering the influence of the standard atmosphere; At the same time, consider the influence of density change on the mass continuity equation under the condition of considering the standard atmosphere, so as to realize the accurate calculation of radar three-dimensional wind field inversion and obtain accurate and reliable three-dimensional wind field inversion information; The iterative equation system of the inverted wind field considering the influence of the standard atmosphere is specifically expressed as: where, v r1 and v r2 are the radial velocities of the two radars at the inversion grid target points after considering the influence of the standard atmosphere, respectively; u, v, and w are the three-dimensional velocity components of the position coordinate P of the inversion grid target point in the Earth coordinate system; x1, y1 and x2, y2 are the x and y axis values of the position coordinates of radars A1 and A2 in the Earth coordinate system, respectively; θ1 is ∠L1PO corresponding to the radar propagation curve path at point A1, the straight line L1L2 is the tangent of the propagation curve path A1P, and O is the center of the Earth; similarly, θ2 is ∠L1PO corresponding to the radar propagation curve path at point A2; w t is the terminal velocity of the precipitation particles falling in the stationary atmosphere, which is estimated using the reflectivity I of the inversion grid target point: w t = 3.8I 0.072 .

2. The dual-radar three-dimensional wind field inversion method considering the influence of standard atmosphere according to claim 1, wherein, The conversion of polar coordinates of radar radial observations to longitude-latitude grid coordinates specifically includes the following steps: 1) Read the longitude, latitude, height of the radar location, as well as the information related to radial velocity and reflectivity from the radar base data; 2) Under the condition of considering the influence of the standard atmosphere, calculate the height of the observation bin point from the ground using the altimetry formula according to the information related to radial velocity or reflectivity and the height of the radar location; 3) Calculate the distance between the observation bin point and the radar station on the ground using the cosine theorem formula of a triangle and the Earth radius based on the height of the observation bin point from the ground; 4) Calculate the longitude, latitude, and height values of the observation bin point using the cosine theorem and sine theorem of spherical triangles based on the distance between the observation bin point and the radar station on the ground, the information related to radial velocity or reflectivity, and the longitude and latitude of the radar location; 5) Use the longitude, latitude, and height values of the observation bin point to interpolate the radial velocity and reflectivity of all observation bin points to the longitude-latitude and height grid target points to be inverted. The cressman distance weight interpolation method is used in the horizontal direction, and linear interpolation is used in the vertical direction to obtain the reflectivity and radial velocity values of the inverted grid target points.

3. The dual-radar three-dimensional wind field inversion method considering the influence of standard atmosphere according to claim 1, characterized in that, Convert the inversion grid target points from the longitude-latitude grid coordinates to the Earth coordinate system to obtain the position coordinates of the inversion grid target points and the two radars in the Earth coordinate system. The specific method is as follows: According to the longitude, latitude, and altitude of the inversion grid target points in the longitude-latitude grid coordinates, obtain the position coordinates of the inversion grid target points in the Earth coordinate system; According to the longitudes, latitudes, altitudes of the two radars in the longitude-latitude grid coordinates and the position coordinates of the inversion grid target points in the Earth coordinate system, calculate the position coordinates of the two radars in the Earth coordinate system respectively by the cosine theorem and sine theorem of spherical trigonometry.

4. The dual-radar three-dimensional wind field inversion method considering the influence of standard atmosphere according to claim 1, characterized in that, The derivation method of the projection coefficients of the vertical and horizontal velocities of the inversion grid target points in the radial velocity direction is specifically as follows: Known points A1(x 1, y 1, z1), A2(x 2, y 2, z2) are the position coordinates of two radars in the earth coordinate system, and the point P(0, 0, z) is the position coordinate of the inversion grid target point in the earth coordinate system; The calculation method of the projection coefficient of the vertical velocity w in the radial velocity direction is: For the radar at point A1, the calculation of the projection coefficient of the vertical velocity w of the inversion grid target point P in the radial velocity direction is: Obtain the curvature of the electromagnetic wave propagation path according to the standard atmospheric refraction parameter table, and obtain the corresponding radius of the electromagnetic wave propagation path according to the curvature of the electromagnetic wave propagation path; Point O′ is the center of the propagation curve path A1P; In the isosceles triangle A1O′P, obtain ∠A1PO′; The straight line L1L2 is the tangent of the propagation curve path A1P, so ∠A1PL1 can be obtained; In the triangle A1OP, ∠A1PO can be obtained according to the cosine theorem of trigonometry; According to ∠A1PL1 and ∠A1PO, ∠L1PO can be obtained, and ∠L1PO is abbreviated as θ1, so as to obtain the projection coefficient cosθ1 of the vertical velocity w of the inversion grid target point in the radial velocity. Similarly, for the radar at point A2, the projection coefficient cosθ2 of the vertical velocity w of the inversion grid target point P in the radial velocity direction can be calculated. The calculation method of the projection coefficients of the horizontal velocities u and v in the radial velocity direction is: For the radar at point A1, the calculation of the projection coefficient of the horizontal velocity v of the inversion grid target point P in the radial velocity is: Make a plane perpendicular to PO through point A1, point D is the intersection of the plane and PO, there is a point E in the due north direction of A1 and the length of A1E is y1, the intersection of the straight line L1L2 and the plane is point G, let the coordinates of point G be (x1′, y1′, z1′), ∠GPD is equal to ∠L1PO, and the straight line in the due north direction through point G intersects the straight line ED at point F. From the similar triangles A1ED and triangle GFD, we can get: Therefore: Then: Therefore, the projection coefficient of the horizontal velocity v of the inversion grid target point P in the radial velocity is: Among them, R GF , T GD , R DP , R GP are respectively the distance between point G and point F, the distance between point A1 and point E, the distance between point G and point D, the distance between point A1 and point D, the distance between point D and point P, and the distance between point G and point P; Similarly for the horizontal velocity u, its projection coefficient in the radial velocity is: Similarly, for the radar at point A2, the projection coefficients of the horizontal velocities v and u of the inversion grid target point P on the radial velocity can be obtained. and .

5. The method for retrieving three-dimensional wind field by dual radar considering the influence of standard atmosphere according to claim 4, characterized in that, The influence of the density change on the mass continuity equation under the condition of considering the standard atmosphere influence is specifically as follows: In the case of deep convection, the mass continuity equation uses the anelastic approximation and ignores the influence of density perturbations. Based on scale analysis and neglecting the density change in the horizontal direction, the mass continuity equation is as follows: Under the condition of standard atmosphere influence, the density ρ changes with height, and the specific calculation formula is: ρ = ρ0(1 - 2.25577×10 -5 Z) 4.25588 Where, Z is the height, the unit is m; ρ0 is the atmospheric density at the mean sea level.

6. The method for retrieving three-dimensional wind field by dual radar considering the influence of standard atmosphere according to claim 5, characterized in that, The specific method to achieve the accurate calculation of radar three-dimensional wind field inversion is as follows: First, given the initial values of u and v, use the mass continuity equation to obtain the first estimated value of w, and w satisfies: w(z = z0) = 0 Among them, z0 represents the height of the grid point in the next layer of the least significant interpolation point of the inversion grid target point; Then, substitute w into the inversion wind field iterative equations to recalculate u, v, and w; Through several iterations, when the difference between the data of the current and previous inversion calculations is less than a given value, the three-dimensional wind field inversion result (u, v, w) that meets the accuracy can be obtained.

7. A dual-radar three-dimensional wind field inversion device considering the influence of the standard atmosphere, characterized in that, It includes: Coordinate transformation module one, which is used to interpolate the reflectivity and radial velocity of all observation library points in polar coordinates observed by the radar to the equal longitude and latitude, equal height grid target points to be inverted, and obtain the reflectivity and radial velocity values of the inversion grid target points in the longitude and latitude grid coordinates; Coordinate transformation module two, which is used to transform the inversion grid target points from the longitude and latitude grid coordinates to the earth coordinate system, and obtain the position coordinates of the inversion grid target points and the two radars in the earth coordinate system; Dual-radar wind field inversion module considering the influence of the standard atmosphere in the earth coordinate system, which is used to construct an inversion wind field iterative equation set based on the reflectivity and radial velocity of the inversion grid target points; consider the influence of the standard atmosphere on the projection of the three-dimensional wind field of the inversion grid target points on the radial velocity in the inversion wind field iterative equation set, deduce the projection coefficients of the vertical and horizontal velocities of the inversion grid target points in the radial velocity direction, so as to determine the inversion wind field iterative equation set considering the influence of the standard atmosphere; at the same time, consider the influence of density change on the mass continuity equation under the condition of considering the standard atmosphere, so as to realize the accurate calculation of the radar three-dimensional wind field inversion and obtain accurate and reliable three-dimensional wind field inversion information; The inversion wind field iterative equation set considering the influence of the standard atmosphere is specifically expressed as: where, v r1 and v r2 are the radial velocities of the two radars at the retrieved grid target points considering the influence of the standard atmosphere; u, v, and w are the three-dimensional velocity components of the retrieved grid target point at the position coordinate P in the earth coordinate system; x1, y1 and x2, y2 are the x and y axis values of the position coordinates of radars A1 and A2 in the earth coordinate system respectively; θ1 is ∠L1PO corresponding to the radar propagation curve path at point A1, the straight line L1L2 is the tangent of the propagation curve path A1P, and O is the center of the earth; similarly, θ2 is ∠L1PO corresponding to the radar propagation curve path at point A2; w t is the terminal velocity of the precipitation particles falling in the stationary atmosphere, which is estimated using the reflectivity I of the retrieved grid target point: w t = 3.8I 0.072 .

8. An electronic device, characterized in that, It includes: One or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1-6.

9. A computer-readable storage medium having computer instructions stored thereon, characterized in that, The computer instructions are used to cause the computer to execute the steps of the method according to any one of claims 1-6.

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