A high-precision calculation method for far-field calculation of lightning electromagnetic fields

Abstract

The present invention relates to the field of electromagnetic computing technology, specifically to a high-precision computing method that can realize far-field computing of lightning electromagnetic fields. In the present invention, by integrating remote sensing data and surface measurement data, the surface characteristics and atmospheric parameters on the electromagnetic field propagation path are accurately obtained, and a more refined set of environmental parameters is established, so that the dynamic characteristics of the lightning electromagnetic field propagation environment are fully considered. By analyzing the influence of surface roughness on the electromagnetic wave reflection power and correcting the propagation loss parameters, the accuracy of electromagnetic wave propagation is enhanced, so that the influence of the surface medium is more accurately quantified. Based on the area where the dielectric characteristics suddenly change on the propagation path, the equivalent reflectivity change and the refractive index adjustment amount are calculated, and the boundary conditions of the nonlinear partial differential equation are corrected, so that the propagation simulation of the lightning electromagnetic field in a complex medium environment is closer to the actual situation. In the process of dynamic boundary correction, the changes in the dielectric constant, magnetic permeability, and refractive index in the sudden change area are accurately adjusted.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic computing technology, and in particular to a high-precision computing method capable of realizing far-field computing of a lightning electromagnetic field. Background Art

[0002] The field of electromagnetic computing technology includes numerical simulation, analytical calculation of electromagnetic fields, magnetic fields, and electric fields, as well as measurement and simulation of related physical quantities. The core content of this technical field includes numerical calculation methods of electromagnetic fields, mathematical modeling, electromagnetic parameter measurement, and the interaction between electromagnetic fields and different media. Electromagnetic computing is widely used in lightning protection, electromagnetic compatibility, wireless communication, radar detection and other fields.

[0003] Among them, the high-precision calculation method that can realize the far-field calculation of lightning electromagnetic field refers to the use of mathematical modeling and numerical calculation methods to accurately simulate the far-field electromagnetic field based on the spatiotemporal distribution characteristics of lightning electromagnetic pulses in the far-field area. This method covers the current distribution modeling of the lightning return channel, the integral calculation of the electromagnetic field in the far-field area, and the evaluation of the impact of the earth's electrical parameters on the electromagnetic field propagation characteristics. By constructing a mathematical expression for the lightning return current and combining the integral transformation method to solve the spatial distribution of the far-field electromagnetic field, the influence of the electrical parameters of different ground media on the electromagnetic field propagation is considered.

[0004] In the prior art, the far-field calculation of lightning electromagnetic fields lacks accurate dynamic modeling of environmental factors, resulting in large calculation errors in the propagation path. Due to the failure to fully consider the changing characteristics of the surface medium such as roughness, wettability, and refractive index, the impact assessment on the reflection and refraction paths of electromagnetic waves is not accurate enough, which in turn affects the calculation accuracy of the far-field field intensity distribution. In the process of calculating electromagnetic field propagation, the prior art handles the dielectric constant mutation area roughly, and cannot accurately identify and adjust the reflectivity and refractive index changes at the mutation boundary, resulting in calculation deviations in the propagation path. There is a lack of dynamic boundary correction mechanism. In the process of electromagnetic field propagation, the setting of boundary conditions is too idealized, which is difficult to adapt to the actual complex environment and affects the stability of the calculation. The space-time discrete optimization is insufficient, and the fixed grid scale and time step are difficult to adapt to the propagation characteristics of different regions. The adaptability of the calculation results under different terrain and medium conditions is poor. The calculation of the far-field field intensity distribution relies on a simplified model, and fails to fully consider the non-uniform distribution of energy in the far-field area, which limits the accuracy of the calculation results in practical applications. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a high-precision calculation method for realizing far-field calculation of lightning electromagnetic fields.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: a high-precision calculation method for realizing far-field calculation of lightning electromagnetic field, comprising the following steps:

[0007] S1: Based on remote sensing data and surface measurement data, the surface characteristics and atmospheric parameters on the lightning electromagnetic field propagation path are obtained, the dielectric constant change rate is recorded, and the lightning electromagnetic field environment parameter set is obtained;

[0008] S2: Based on the lightning electromagnetic field environment parameter set, the influence of the surface roughness on the electromagnetic wave reflection power is analyzed and the propagation loss parameter is adjusted to obtain the lightning electromagnetic field medium influence correction result;

[0009] S3: Based on the lightning electromagnetic field medium influence correction result, extract the boundary area where the dielectric characteristics suddenly change on the propagation path, determine the change trend of the refraction path, calculate the equivalent reflectivity change value and refractive index adjustment amount of the sudden change boundary area, adjust the boundary conditions of the nonlinear partial differential equation, and obtain the lightning electromagnetic field dynamic boundary correction result;

[0010] S4: based on the dynamic boundary correction result of the lightning electromagnetic field, the refraction and attenuation changes after boundary adjustment are calculated, the spatiotemporal offset area on the propagation path is determined, the grid scale and time step are adjusted, and the spatiotemporal discrete optimization result of the lightning electromagnetic field is obtained;

[0011] S5: Based on the spatiotemporal discrete optimization result of the lightning electromagnetic field, analyzing the energy distribution of the optimized lightning electromagnetic field propagation path, and obtaining the far-field strength distribution data of the lightning electromagnetic field.

[0012] As a further solution of the present invention, the lightning electromagnetic field environmental parameter set includes surface roughness, wettability, particle size, terrain undulation, dielectric constant, atmospheric temperature, air density, humidity, refractive index, and time variation trend of surface dielectric constant; the lightning electromagnetic field medium influence correction result includes reflected power, scattering angle, reflection loss, attenuation parameter, refractive index change data, electromagnetic wave propagation loss, refractive index correction factor, reflectivity correction factor, and scattering correction factor; the lightning electromagnetic field dynamic boundary correction result includes dielectric constant spatial distribution, magnetic permeability spatial distribution, refractive index spatial distribution, mutation boundary area, refractive path variation trend, equivalent reflectivity variation value, refractive index adjustment amount, electromagnetic wave reflection coefficient, electromagnetic wave transmission coefficient, and nonlinear partial differential equation boundary condition; the lightning electromagnetic field spatiotemporal discrete optimization result includes refraction variation of electromagnetic wave propagation path, attenuation variation of electromagnetic wave propagation path, spatiotemporal offset area, grid scale, and time step; the lightning electromagnetic field far-field field strength distribution data includes lightning electromagnetic field propagation path, energy distribution, and far-field electromagnetic field value.

[0013] As a further solution of the present invention, the steps of acquiring the lightning electromagnetic field environment parameter set are specifically as follows:

[0014] S111: Acquire remote sensing data and surface measurement data, extract the surface roughness, wettability, particle size, terrain undulation and dielectric constant along the lightning electromagnetic field propagation path, record the initial state and spatial distribution of each parameter, and obtain the surface parameter data set;

[0015] S112: Obtain the atmospheric temperature, air density, humidity and refractive index of multiple altitude layers, analyze the vertical distribution trend of the atmospheric parameters of each altitude layer, and obtain the atmospheric parameter data set of the altitude layer;

[0016] S113: Based on the surface parameter data set and the altitude layer atmospheric parameter data set, the formula is used:

[0017] ;

[0018] Calculate the time rate of change of the dielectric constant of the surface , according to the rate of change Analyze the dynamic change characteristics of dielectric constant, record the time change trend of surface dielectric constant, and combine all environmental parameters to obtain the lightning electromagnetic field environmental parameter set;

[0019] in, Representative time The surface dielectric constant at time represents the surface dielectric constant at the previous time step, is the total number of time steps.

[0020] As a further solution of the present invention, the step of obtaining the lightning electromagnetic field medium influence correction result is specifically:

[0021] S211: Based on the lightning electromagnetic field environment parameter set, analyzing the influence of the surface roughness in the lightning electromagnetic field propagation path on the electromagnetic wave reflection power and scattering angle, determining the reflection power and scattering angle under each roughness condition, and obtaining the influence data of the surface roughness on the reflection power and scattering angle;

[0022] S212: Based on the data of the influence of the surface roughness on the reflected power and the scattering angle, the formula is adopted:

[0023] ;

[0024] Calculate the correction factor for reflection loss caused by changes in humidity ;

[0025] in, Represents the reflection loss correction factor caused by the change in humidity, represents the dielectric constant of wet soil, represents the base dielectric constant of dry soil, represents the reflectivity of dry soil;

[0026] S213: Extract the refractive index change data of each altitude layer and analyze the electromagnetic wave propagation loss caused by the change of air density. The formula is:

[0027] ;

[0028] Correction factor for reflection loss Make adjustments and calculate the adjusted reflection loss correction factor , and obtain the correction result of medium influence on lightning electromagnetic field;

[0029] in, is the correction factor for reflection loss due to humidity changes, is the amplification factor of the refractive index change on the reflection loss, is the refractive index of the current air layer, is the refractive index of the reference air layer.

[0030] As a further solution of the present invention, the step of calculating the equivalent reflectivity change value and the refractive index adjustment amount of the sudden change boundary area is specifically:

[0031] S311: Based on the lightning electromagnetic field medium influence correction result, analyze the spatial distribution of the dielectric constant, magnetic permeability and refractive index in the lightning electromagnetic field propagation path, extract the dielectric constant change rate, magnetic permeability change rate and refractive index change rate of each spatial position point, screen the boundary area where the dielectric characteristics have mutations, and obtain the distribution data of the mutation boundary area;

[0032] S312: Based on the mutation boundary area distribution data, the formula is used:

[0033] ;

[0034] Calculate the change in equivalent reflectivity in the mutation boundary area , according to the change value of equivalent reflectivity Determine the change trend of the refraction path of electromagnetic waves in the sudden change boundary area and obtain the analysis results of the equivalent reflectivity change;

[0035] in, Represents the reflectivity of the reference medium in the abrupt boundary area, Represents the change in dielectric constant in the abrupt boundary area, Represents the dielectric constant of the reference medium in the abrupt boundary region, Represents the change in magnetic permeability in the sudden change boundary area, Represents the magnetic permeability of the reference medium in the abrupt boundary region;

[0036] S313: Based on the equivalent reflectivity change analysis result, the formula is used:

[0037] , ;

[0038] Calculate the correction amount of the refractive index due to the change of the dielectric constant and the correction of the refractive index due to the change in magnetic permeability ;

[0039] in, represents the dielectric constant of the abrupt boundary region, Represents the dielectric constant of the reference medium in the abrupt boundary region, Represents the refractive index of the reference medium in the abrupt boundary region, represents the magnetic permeability of the abrupt boundary region, Represents the magnetic permeability of the reference medium in the abrupt boundary area.

[0040] As a further solution of the present invention, the steps for obtaining the dynamic boundary correction result of the lightning electromagnetic field are specifically as follows:

[0041] S321: Correction of refractive index based on the dielectric constant change and the correction of the refractive index due to the change in magnetic permeability , using the formula:

[0042] ;

[0043] Calculate the corrected refractive index ;

[0044] in, represents the reference refractive index before correction, that is, the refractive index not affected by the changes in dielectric constant and magnetic permeability;

[0045] S322: Based on the corrected refractive index , using the formula:

[0046] ;

[0047] Calculate the corrected reflection coefficients and transmission coefficient ;

[0048] in, is the refractive index of the incident medium;

[0049] S323: Based on the corrected reflection coefficient and transmission coefficient , using the formula:

[0050] ;

[0051] Calculate boundary condition corrections , the corrected boundary conditions of the nonlinear partial differential equation are obtained, the corrected boundary conditions are applied in the process of solving the lightning electromagnetic field, the nonlinear partial differential equation is numerically calculated, the dynamic distribution of the lightning electromagnetic field is solved, and the dynamic boundary correction results of the lightning electromagnetic field are obtained.

[0052] As a further solution of the present invention, the step of obtaining the spatiotemporal discrete optimization result of the lightning electromagnetic field is specifically as follows:

[0053] S411: Based on the dynamic boundary correction result of the lightning electromagnetic field, the formula is used:

[0054] ;

[0055] Calculate the change in refraction angle of electromagnetic waves in the boundary area ;

[0056] in, represents the angle of incidence, represents the corrected refractive index, represents the refractive index of the incident medium;

[0057] Based on the change of the refraction angle of the electromagnetic wave in the boundary area , using the formula:

[0058] ;

[0059] Calculate the change in refraction of the electromagnetic wave propagation path after boundary adjustment ;

[0060] in, Represents the benchmark propagation distance;

[0061] S412: adjusting the refraction change of the electromagnetic wave propagation path based on the boundary , using the formula:

[0062] ;

[0063] Calculate the adjusted electromagnetic wave attenuation ;

[0064] in, Represents the reference attenuation, represents the attenuation factor;

[0065] S413: Setting a spatial step size on the propagation path to determine the initial spatial grid scale, and adjusting the refraction change of the electromagnetic wave propagation path according to the boundary. and the adjusted electromagnetic wave attenuation , determine the spatiotemporal offset area caused by boundary adjustment on the propagation path, adjust the grid scale and time step of the offset area, and obtain the spatiotemporal discrete optimization result of the lightning electromagnetic field.

[0066] As a further solution of the present invention, the step of acquiring the lightning electromagnetic field far-field intensity distribution data is specifically as follows:

[0067] S511: Based on the spatiotemporal discrete optimization result of the lightning electromagnetic field, according to the distribution of the electric field and the magnetic field, determine the change trend of the electromagnetic field energy, classify the energy intensity in each grid area, detect the energy concentration area and the diffusion area, and generate energy distribution data on the lightning electromagnetic field propagation path;

[0068] S512: Based on the energy distribution data on the lightning electromagnetic field propagation path, according to the change of electromagnetic field intensity in the far field area, the electric field and magnetic field data at various distance positions are screened to determine the field intensity distribution trend in the far field area, identify the influencing factors of the field intensity change, and obtain the far-field electric field intensity data of the lightning electromagnetic field;

[0069] S513: Based on the far-field electric field strength data of the lightning electromagnetic field, the field strength data of the azimuth angle in the grid space are sorted out to establish a field strength distribution structure in the far-field region, and obtain the far-field field strength distribution data of the lightning electromagnetic field.

[0070] Compared with the prior art, the advantages and positive effects of the present invention are:

[0071] In the present invention, by integrating remote sensing data and surface measurement data, the surface characteristics and atmospheric parameters on the electromagnetic field propagation path are accurately obtained, and a more refined set of environmental parameters is established, so that the dynamic characteristics of the lightning electromagnetic field propagation environment are fully considered. By analyzing the influence of surface roughness on the electromagnetic wave reflection power and correcting the propagation loss parameters, the electromagnetic wave propagation accuracy is enhanced, so that the influence of the surface medium is more accurately quantified. Based on the area where the dielectric characteristics on the propagation path are suddenly changed, the equivalent reflectivity change and the refractive index adjustment amount are calculated, and the boundary conditions of the nonlinear partial differential equation are corrected, so that the propagation simulation of the lightning electromagnetic field in a complex medium environment is closer to the actual situation. In the dynamic boundary correction process, the changes in the dielectric constant, magnetic permeability, and refractive index of the sudden change area are accurately adjusted, which improves the stability and accuracy of the lightning electromagnetic field calculation. By optimizing the grid scale and time step, the calculation error is reduced, the time and space discrete accuracy is improved, and the calculation is more adaptable. Finally, in the far field area, a complete far field strength distribution is constructed according to the trend of electromagnetic field energy change to ensure that the far field electromagnetic field calculation results are more in line with reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a schematic diagram of the main steps of the present invention;

[0073] Figure 2 A flow chart of obtaining a lightning electromagnetic field environment parameter set for the present invention;

[0074] Figure 3 A flow chart of obtaining the correction result of the medium influence of the lightning electromagnetic field according to the present invention;

[0075] Figure 4 A flow chart of calculating the equivalent reflectivity change value and refractive index adjustment amount of the sudden change boundary area in the present invention;

[0076] Figure 5 A flow chart of obtaining the dynamic boundary correction result of the lightning electromagnetic field according to the present invention;

[0077] Figure 6 A flow chart of obtaining the spatiotemporal discrete optimization results of the lightning electromagnetic field according to the present invention;

[0078] Figure 7 The present invention is a flow chart for obtaining far-field intensity distribution data of a lightning electromagnetic field. DETAILED DESCRIPTION

[0079] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0080] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0081] See also Figure 1 The present invention provides a technical solution: a high-precision calculation method for realizing far-field calculation of lightning electromagnetic field, comprising the following steps:

[0082] S1: Based on remote sensing data and surface measurement data, the surface characteristics and atmospheric parameters on the lightning electromagnetic field propagation path are obtained, the dielectric constant change rate is recorded, and the lightning electromagnetic field environment parameter set is obtained;

[0083] S2: Based on the lightning electromagnetic field environment parameter set, the influence of surface roughness on the electromagnetic wave reflection power is analyzed and the propagation loss parameters are adjusted to obtain the correction result of the lightning electromagnetic field medium influence;

[0084] S3: Based on the correction results of the lightning electromagnetic field medium influence, the boundary area where the dielectric characteristics suddenly change on the propagation path is extracted, the change trend of the refraction path is determined, the equivalent reflectivity change value and the refractive index adjustment amount of the sudden change boundary area are calculated, and the boundary conditions of the nonlinear partial differential equation are adjusted to obtain the dynamic boundary correction results of the lightning electromagnetic field;

[0085] S4: Based on the dynamic boundary correction results of the lightning electromagnetic field, the refraction and attenuation changes after boundary adjustment are calculated, the spatiotemporal offset area on the propagation path is determined, the grid scale and time step are adjusted, and the spatiotemporal discrete optimization results of the lightning electromagnetic field are obtained;

[0086] S5: Based on the spatiotemporal discrete optimization results of the lightning electromagnetic field, analyze the energy distribution of the optimized lightning electromagnetic field propagation path and obtain the far-field strength distribution data of the lightning electromagnetic field;

[0087] The lightning electromagnetic field environmental parameter set includes surface roughness, wettability, particle size, terrain undulation, dielectric constant, atmospheric temperature, air density, humidity, refractive index, and time variation trend of surface dielectric constant. The lightning electromagnetic field medium influence correction results include reflected power, scattering angle, reflection loss, attenuation parameter, refractive index change data, electromagnetic wave propagation loss, refractive index correction factor, reflectivity correction factor, and scattering correction factor. The lightning electromagnetic field dynamic boundary correction results include the spatial distribution of dielectric constant, the spatial distribution of magnetic permeability, the spatial distribution of refractive index, the mutation boundary area, the refractive path variation trend, the equivalent reflectivity variation value, the refractive index adjustment amount, the electromagnetic wave reflection coefficient, the electromagnetic wave transmission coefficient, and the nonlinear partial differential equation boundary conditions. The lightning electromagnetic field spatiotemporal discrete optimization results include the refraction variation of the electromagnetic wave propagation path, the attenuation variation of the electromagnetic wave propagation path, the spatiotemporal offset area, the grid scale, and the time step. The lightning electromagnetic field far-field field strength distribution data include the lightning electromagnetic field propagation path, energy distribution, and far-field electromagnetic field value.

[0088] See also Figure 2 , the specific steps for obtaining the lightning electromagnetic field environment parameter set are:

[0089] S111: Acquire remote sensing data and surface measurement data, extract the surface roughness, wettability, particle size, terrain undulation and dielectric constant along the lightning electromagnetic field propagation path, record the initial state and spatial distribution of each parameter, and obtain the surface parameter data set;

[0090] First, use the remote sensing data acquisition system to obtain surface roughness data. Laser radar (LiDAR) or high-resolution optical images can be used to extract surface height information through three-dimensional reconstruction technology, and calculate the microscopic undulation of the surface. For example, in a typical measurement in a mountainous area, 10 representative points are selected for laser ranging measurement, and the average height variation range is calculated to obtain a surface roughness of 0.5 cm. Wetness measurement can use soil moisture sensors, insert capacitive or time domain reflectometry (TDR) humidity sensors at different depths to determine the relationship between dielectric constant and moisture content. For example, in an agricultural area, it was found that the humidity at 10 cm on the surface was 25%, and the humidity at 30 cm was 20%, indicating that the shallow layer was more wet. Particle size analysis uses screening method or laser particle size analyzer to dry the soil sample and sieve it to analyze the proportion of different particle size contents. For example, after 2 mm screening, the average particle diameter is calculated to be 0.3 mm. The terrain undulation data is based on the digital elevation model (DEM), which uses remote sensing images to extract terrain information and calculate the slope and surface elevation changes. For example, in the DEM data analysis of a mountainous area, the slope range is 10°-30°, and the maximum elevation change is 80m. The dielectric constant is measured using a vector network analyzer to measure the dielectric response of soil samples at different frequencies. For example, the dielectric constant of a soil sample measured at a frequency of 1GHz is 15. All measurement results are spatially interpolated to obtain the surface parameter distribution data of the entire measurement area, and then the surface parameter data set is established.

[0091] S112: Obtain the atmospheric temperature, air density, humidity and refractive index of multiple altitude layers, analyze the vertical distribution trend of the atmospheric parameters of each altitude layer, and obtain the atmospheric parameter data set of the altitude layer;

[0092] Use sounding balloons or drones equipped with sensors to measure atmospheric parameters at different altitudes in layers. Sounding balloons carry thermometers, humidity sensors, and air pressure sensors, rise at intervals of 100 meters, and record measurement data. For example, in a certain observation, at an altitude of 0 meters, the temperature measurement value was 25°C, humidity was 60%, air density was 1.225kg / m³, and refractive index was 1.0003; at an altitude of 500 meters, the temperature was 22.5°C, humidity was 55%, air density was 1.165kg / m³, and refractive index was 1.00025; at an altitude of 1000 meters, the temperature was 20°C, humidity was 50%, air density was 1.112kg / m³, and refractive index was 1.0002. When analyzing these data, it was found that the temperature showed a downward trend with increasing altitude. For every 100 meters of ascent, the temperature dropped by about 0.5°C. The air density decreased with increasing altitude, and the humidity also showed a downward trend. The refractive index of the air changed relatively little, but the refractive index value was slightly higher in high humidity areas. For air density, a pressure sensor is used to measure atmospheric pressure, and the corresponding density value is found according to the standard atmospheric density table. For example, at an altitude of 0 meters, the measured pressure is 1013hPa, and the air density is 1.225kg / m³ from the table; at an altitude of 500 meters, the pressure is 954hPa, corresponding to an air density of 1.165kg / m³; at an altitude of 1000 meters, the pressure is 899hPa, corresponding to an air density of 1.112kg / m³. Humidity measurement uses an electronic humidity sensor on a sounding balloon, which measures relative humidity based on capacitance changes. For example, the humidity is 55% at an altitude of 500 meters and 50% at an altitude of 1000 meters. The refractive index calculation is based on the temperature, humidity, and air pressure data, and the standard atmospheric refractive index table is consulted to obtain the corresponding refractive index value. The measurement data of these different altitude layers are sorted out, and combined with the surface parameter data set, an atmospheric environment model of the lightning electromagnetic field propagation path is established to obtain the altitude layer atmospheric parameter data set.

[0093] S113: Based on the surface parameter data set and the altitude layer atmospheric parameter data set, the formula is used:

[0094] ;

[0095] Calculate the time rate of change of the dielectric constant of the surface , according to the rate of change Analyze the dynamic change characteristics of dielectric constant, record the time change trend of surface dielectric constant, and combine all environmental parameters to obtain the lightning electromagnetic field environmental parameter set;

[0096] in, Representative time The surface dielectric constant at time represents the surface dielectric constant at the previous time step, is the total number of time steps;

[0097] At a certain observation point, t=1 hour is measured , t = 2 hours ,but , indicating that the dielectric constant change rate is 0.5 units / hour during this time interval. The mean change rate of the measurement data of multiple time steps is calculated to determine the long-term change trend of the dielectric constant. Combined with the daily change pattern of the dielectric constant, the time series analysis method can be used to analyze whether its change trend is periodic. For example, by calculating the mean change within a 24-hour period, it is found that the dielectric constant fluctuates between 0.2-0.8 during the day under humid conditions, and between 0.1-0.4 under dry conditions. Through these calculations, the time change trend data of the surface dielectric constant are obtained, and finally the lightning electromagnetic field environment parameter set is obtained.

[0098] See also Figure 3 , the specific steps for obtaining the correction results of lightning electromagnetic field medium influence are:

[0099] S211: Based on the lightning electromagnetic field environmental parameter set, analyze the influence of the surface roughness on the reflected power and scattering angle of electromagnetic waves in the lightning electromagnetic field propagation path, determine the reflected power and scattering angle under each roughness condition, and obtain the influence data of the surface roughness on the reflected power and scattering angle;

[0100] Select multiple measurement points and measure the surface roughness of the ground. The measurement method can be a three-dimensional laser scanner or a high-precision contact roughness meter to obtain the surface microstructure data, calculate its root mean square height, and normalize it. The data is converted into parameters suitable for the electromagnetic wave propagation path, and the electromagnetic wave reflection power and scattering angle under different roughness conditions are calculated. The reflectivity of the surface under different roughness conditions is calculated using the Fresnel equation, and the reflection power of lightning electromagnetic waves is calculated in combination with the reflectivity. The influence of surface roughness on the scattering angle is calculated according to the scattering theory. The Rayleigh scattering theory is used to divide the roughness influence into the mirror reflection area and the diffuse reflection area, and the range of variation of the electromagnetic wave scattering angle in different areas is calculated. The calculation results of the smooth surface are compared to obtain the influence data of the surface roughness on the reflection power and scattering angle.

[0101] For the calculation of the root mean square height (RMSHeight): Assume the given height data: .average height: . Root mean square height calculation formula: , The result is 1.356cm, reflecting the average deviation of the surface. It is The height of each measuring point is obtained by a 3D laser scanner. is the average height of all measuring points. Sum the values ​​and divide by the number of points Calculated. is the total number of measurement points, which usually depends on the experimental design. The typical number of measurement points is between 10 and 50. Fresnel equation (calculation of reflectivity R): Refractive index of incident medium , refractive index of reflecting medium . Angle of incidence , converted to radians: . Transmission angle According to Snell's law: .in, are the refractive indices of the incident medium and the reflecting medium respectively. For the air-to-soil scenario, (air) and (soil). is the angle of incidence, assumed to be 30 degrees. is the transmission angle, calculated from Snell's law, . Reflectivity calculation: , The result is 0.0578, which represents the total reflectivity of the surface. is the dielectric constant of moist soil and can be determined from a table of soil moisture content and known soil types. It is the benchmark dielectric constant of dry soil, generally determined through literature or experiments. is the reflectivity of dry soil, which can be calculated using the Fresnel equation above.

[0102] S212: Based on the data on the effect of surface roughness on reflected power and scattering angle, the formula is used:

[0103] ;

[0104] Calculate the correction factor for reflection loss caused by changes in humidity ;

[0105] in, Represents the reflection loss correction factor caused by the change in humidity, represents the dielectric constant of wet soil, represents the base dielectric constant of dry soil, represents the reflectivity of dry soil;

[0106] Assume that the value is 15, which is obtained from the experimental data according to the soil type and moisture content table. Obtained through literature review, the value is 5, The result calculated from the Fresnel equation is 0.0578, , this step shows that the correction factor for reflection loss due to moisture change is 0.1156. Assuming the dielectric constant of dry soil ( ) is 5 (same as the baseline for wet conditions). Baseline reflectance ( ) is assumed to be 0.0578, obtained from the Fresnel equation calculated in the previous paragraph 1. Calculate the reflection loss correction factor for dry conditions ( ): , under dry conditions, since the dielectric constant does not change, the reflection loss correction factor is 0, which means that there is almost no additional reflection loss under dry conditions. Calculation under wet conditions: The reflection loss correction factor under wet conditions has been calculated . Correction factor for reflection loss under dry conditions: , reflection loss correction factor under wet conditions: By comparison, we can see that the correction factor under wet conditions increases from 0 to 0.1156. This shows that under wet conditions, due to the increase in the dielectric constant of the soil (from 5 to 15), the energy absorption and scattering properties of the soil change, resulting in more electromagnetic wave energy being absorbed or scattered by the soil, so the reflection loss increases significantly. This change has a significant impact on the propagation characteristics of electromagnetic waves, especially in radar and communication systems, where the increase in this loss may lead to a significant decrease in signal strength, which in turn affects the performance and reliability of the system.

[0107] S213: Extract the refractive index change data of each altitude layer and analyze the electromagnetic wave propagation loss caused by the change of air density. The formula is:

[0108] ;

[0109] Correction factor for reflection loss Make adjustments and calculate the adjusted reflection loss correction factor , and obtain the correction result of medium influence on lightning electromagnetic field;

[0110] in, is the correction factor for reflection loss due to wetness change (dimensionless), It is the amplification factor (dimensionless) of the refractive index change on the reflection loss. Its value depends on the frequency of the electromagnetic wave and the characteristics of the propagation medium. It can be set through experiments or experience. It is usually taken as magnitude to ensure that the change in reflection loss is within a reasonable range. is the refractive index of the current air layer, dimensionless. is the refractive index of the reference air layer, dimensionless. It is the relative change in refractive index (dimensionless), which represents the effect of changes in air density on the refractive index.

[0111] Known parameters, , (the current refractive index of the air layer), (reference air layer refractive index), (Empirical value setting, based on the influence of changes in electromagnetic wave frequency and air density).

[0112] Calculate the refractive index change ;

[0113] Calculate the adjusted reflection loss correction factor ;

[0114] Compared to the basic reflection loss correction factor caused by humidity change , the reflection loss factor increases , which increases by about This adjustment range more reasonably reflects the combined effect of wettability change and refractive index change on electromagnetic wave propagation loss.

[0115] See also Figure 4 , the steps for calculating the equivalent reflectivity change value and refractive index adjustment amount of the mutation boundary area are as follows:

[0116] S311: Based on the correction results of the lightning electromagnetic field medium effect, analyze the spatial distribution of the dielectric constant, magnetic permeability and refractive index in the lightning electromagnetic field propagation path, extract the dielectric constant change rate, magnetic permeability change rate and refractive index change rate of each spatial position point, screen the boundary areas where the dielectric characteristics have mutations, and obtain the distribution data of the mutation boundary areas;

[0117] For the calculation of the change in dielectric constant, magnetic permeability and refractive index between adjacent measuring points, these changes are divided by the interval distance between the measuring points to calculate the change rate, the coordinate data between adjacent measuring points are obtained, the Euclidean distance between adjacent measuring points is calculated and used as the measuring point spacing, the dielectric constant change rate is calculated by dividing the measured dielectric constant change by the measuring point spacing, the magnetic permeability change rate is calculated by dividing the measured magnetic permeability change by the measuring point spacing, and the refractive index change rate is calculated by dividing the measured refractive index change by the measuring point spacing. It is determined whether the change rate exceeds the set threshold, and the position exceeding the threshold is screened out as the mutation boundary area. The setting of the threshold refers to the change range of the surface medium under the natural state. Specifically, a statistical method is used to analyze the measurement data of the dielectric constant, magnetic permeability and refractive index under different geological conditions, the mean and standard deviation of the change rate of each medium are calculated, and the threshold is set to the mean plus three times the standard deviation as the boundary standard for determining the mutation area.

[0118] S312: Based on the distribution data of the mutation boundary area, the formula is used:

[0119] ;

[0120] Calculate the change in equivalent reflectivity in the mutation boundary area , according to the change value of equivalent reflectivity Determine the change trend of the refraction path of electromagnetic waves in the sudden change boundary area and obtain the analysis results of the equivalent reflectivity change;

[0121] in, Represents the reflectivity of the reference medium in the abrupt boundary area, Represents the change in dielectric constant in the abrupt boundary area, Represents the dielectric constant of the reference medium in the abrupt boundary region, Represents the change in magnetic permeability in the sudden change boundary area, Represents the magnetic permeability of the reference medium in the abrupt boundary region;

[0122] Call the distribution data of the mutation boundary area, analyze the change trend of the refraction path of the electromagnetic wave in the mutation boundary area, obtain the incident angle data of the mutation boundary area and the dielectric constant and permeability on both sides of the area, calculate the refraction angle of the electromagnetic wave in the mutation boundary area, and call Snell's law: ,in, represents the refractive index of the incident medium, represents the refractive index of the transmission medium, represents the angle of incidence, represents the refraction angle. , , , , ,but:

[0123] ;

[0124] The final calculated equivalent reflectivity change value of the mutation boundary area is 0.18. The change trend can be compared based on the change values ​​at different times.

[0125] S313: Based on the analysis results of equivalent reflectivity change, the formula is used:

[0126] , ;

[0127] Calculate the correction amount of the refractive index due to the change of the dielectric constant and the correction of the refractive index due to the change in magnetic permeability ;

[0128] in, represents the dielectric constant of the abrupt boundary region, Represents the dielectric constant of the reference medium in the abrupt boundary region, Represents the refractive index of the reference medium in the abrupt boundary region, represents the magnetic permeability of the abrupt boundary region, Represents the magnetic permeability of the reference medium in the abrupt boundary region;

[0129] set up , , , , ,but:

[0130] ;

[0131] ;

[0132] The results show that the correction amount of the dielectric constant change to the refractive index is , the correction amount of the refractive index due to the change of magnetic permeability .

[0133] See also Figure 5 , the specific steps for obtaining the dynamic boundary correction results of the lightning electromagnetic field are:

[0134] S321: Correction of refractive index based on dielectric constant change and the correction of the refractive index due to the change in magnetic permeability , using the formula:

[0135] ;

[0136] Calculate the corrected refractive index ;

[0137] in, represents the reference refractive index before correction, that is, the refractive index not affected by the changes in dielectric constant and magnetic permeability;

[0138] First, the changes in dielectric constant and permeability are measured, assuming that the initial dielectric constant of a certain medium is is 2.5, the initial magnetic permeability is 1.0, under the test conditions, the change in dielectric constant is measured , the magnetic permeability changes , when calculating the correction amount of the refractive index, use the correction formula: , substitute the data into the calculation: , , calculate the corrected refractive index: , assuming the base refractive index , substitute into the calculation: .

[0139] S322: Based on the corrected refractive index , using the formula:

[0140] ;

[0141] Calculate the corrected reflection coefficients and transmission coefficient ;

[0142] in, is the refractive index of the incident medium;

[0143] Calculate the corrected reflection coefficient and transmission coefficient, and the refractive index of the incident medium is set to ,calculate: , , substitute the data: , ,Finally, the corrected reflection and transmission coefficient of the boundary area is obtained.

[0144] S323: Based on the corrected reflection coefficient and transmission coefficient , using the formula:

[0145] ;

[0146] Calculate boundary condition corrections , obtain the corrected boundary conditions of the nonlinear partial differential equation, apply the corrected boundary conditions in the process of solving the lightning electromagnetic field, perform numerical calculations on the nonlinear partial differential equation, solve the dynamic distribution of the lightning electromagnetic field, and obtain the dynamic boundary correction results of the lightning electromagnetic field;

[0147] Substituting the calculated values: ; Calculate the corrected electric field strength, assuming the incident electric field strength , calculate the reflected electric field strength: ; . Transmitted electric field strength: , Finally, the corrected boundary conditions of the nonlinear partial differential equation are obtained, the corrected boundary conditions of the nonlinear partial differential equation are called, the corrected boundary conditions are applied in the lightning electromagnetic field solution process, and the corrected current density is calculated. , the relationship between current density and electric field strength is as follows: , assuming that the conductivity of the medium ,calculate: , , then calculate the magnetic induction intensity Change, assuming that the initial magnetic induction intensity , use the difference method to calculate the magnetic induction intensity at the next moment: , let the time step , spatial step length , substitute into the calculation: ,Finally, the dynamic boundary correction result of the lightning electromagnetic field is obtained.

[0148] in, is the current density, which indicates the current flow per unit area, and its unit is: (amperes per square meter), is the conductivity of the medium, in units of (Siemens per meter), which indicates the conductivity of a medium to electric current. is the electric field strength in (volts per meter), which represents the potential difference per unit length, is the magnetic induction intensity, unit: (Tesla), is the magnetic induction intensity at the next moment, is the magnetic induction intensity at the current moment (the initial value is set to ), is the time step in units of (seconds), representing discrete changes in time, is the transmitted electric field strength, in units of , represents the remaining electric field strength after passing through the medium, is the spatial step length in units of (meters), indicating the spatial interval for calculating discretization.

[0149] result Represents the corrected magnetic induction intensity The change at the next moment, if the value is negative, it means that the direction of the magnetic induction intensity changes in the opposite direction relative to the initial direction. Due to the electric field strength Acting on the space step The amount of magnetic field change generated within the range. This means that at this moment, the magnetic induction intensity has decreased compared to the previous moment. , if the initial magnetic induction intensity is zero, then the magnetic induction intensity at the next moment is , indicating that the direction of the magnetic field is opposite to the positive direction initially assumed.

[0150] Assume that in another case, the calculated change in magnetic induction intensity is , then the positive and negative signs of the value indicate that the direction of the magnetic induction intensity is consistent with the positive direction of the initial assumption, that is, the magnetic field is in the time step The inside has increased , and its direction is the same as the initial setting direction. This situation usually occurs when the electric field direction or boundary conditions are different. For example, if the polarization direction of the incident electromagnetic wave changes, or the dielectric constant and magnetic permeability distribution of the boundary area are different, the magnetic induction intensity may increase over time and the direction remains unchanged. In this case, if the initial magnetic induction intensity is not zero, but some positive number, such as , then the magnetic induction intensity at the next moment is: , which indicates that the magnetic induction intensity increases and the direction remains consistent with the original direction without any reverse change.

[0151] See also Figure 6 , the specific steps for obtaining the spatiotemporal discrete optimization results of lightning electromagnetic fields are as follows:

[0152] S411: Based on the dynamic boundary correction results of the lightning electromagnetic field, the formula is used:

[0153] ;

[0154] Calculate the change in refraction angle of electromagnetic waves in the boundary area ;

[0155] in, represents the angle of incidence, represents the corrected refractive index, represents the refractive index of the incident medium;

[0156] Based on the change of refraction angle of electromagnetic wave in the boundary area , using the formula:

[0157] ;

[0158] Calculate the change in refraction of the electromagnetic wave propagation path after boundary adjustment ;

[0159] in, Represents the benchmark propagation distance;

[0160] The incident angle Set to 30°, the refractive index of the incident medium is 1.0, substitute the data and calculate: ; Calculate the change in the refraction path , using the formula: ; Among them, the propagation path reference distance is , substitute into the calculation: ; Obtain the refraction change of the electromagnetic wave propagation path after boundary adjustment.

[0161] S412: Change in refraction of the electromagnetic wave propagation path after boundary adjustment , using the formula:

[0162] ;

[0163] Calculate the adjusted electromagnetic wave attenuation ;

[0164] in, Represents the reference attenuation, represents the attenuation factor;

[0165] Set the reference attenuation , attenuation factor The attenuation factor is set based on the energy loss characteristics of electromagnetic waves in different media. First, the conductivity of the medium is obtained. and dielectric constant , the complex dielectric constant of the medium at a specific frequency is measured experimentally, and the attenuation characteristics of the medium are calculated. The attenuation of electromagnetic waves in the medium is usually determined by its propagation loss factor, which is affected by conductivity and frequency. In order to determine a reasonable attenuation factor, a typical electromagnetic wave propagation medium is selected for measurement, for example, at a frequency Under normal conditions, the conductivity of common media such as moist soil is about , the corresponding loss factor is generally Therefore, the attenuation factor is set As a reasonable value, this value can characterize the attenuation degree of the medium to electromagnetic waves in a typical electromagnetic environment.

[0166] Substitute the data: ; The attenuation change of the electromagnetic wave propagation path after boundary adjustment is .

[0167] S413: Set the spatial step size on the propagation path to determine the initial spatial grid scale, and adjust the refraction change of the electromagnetic wave propagation path according to the boundary and the adjusted electromagnetic wave attenuation , determine the spatiotemporal offset area caused by boundary adjustment on the propagation path, adjust the grid scale and time step of the offset area, and obtain the spatiotemporal discrete optimization result of the lightning electromagnetic field;

[0168] First, according to the change in the refraction path Determine the spatial grid scale and set the grid scale judgment criteria based on the wavelength of electromagnetic waves. The scale of the grid should be based on the ratio of to To ensure the stability of numerical calculations, for the common electromagnetic wave frequency range in this scenario (such as 100MHz to 10GHz), calculate its wavelength range in the air (in =The wavelength range can be calculated as 3m to 0.03m, which determines the grid scale range as 0.3m to 0.0015m. Then, according to the change in the refraction path, Determine the adjustment of the spatial grid scale if the refraction path changes If the wavelength is greater than 3m, the refraction changes in this area are more drastic, and the grid scale should be To ensure the calculation accuracy, the grid size is set to , if the refraction path change is less than the lower limit of the wavelength range , then the refraction change in this area is small, and the grid scale can be To reduce the computational burden, the grid size is set to , in this scene Much greater than , so the grid scale is selected Then, the time step is adjusted according to the propagation characteristics of electromagnetic waves and the refractive index of the medium. The propagation speed of electromagnetic waves in the medium is ,in , calculate the propagation speed m / s, and then determine the time step according to the CFL (Courant-Friedrichs-Lewy) condition , the time step satisfies , to calculate the grid size Substitute into the calculation: , so the time step is finally determined , call the refraction change of the electromagnetic wave propagation path after boundary adjustment and the attenuation change of the electromagnetic wave propagation path after boundary adjustment, judge the spatiotemporal offset area caused by boundary adjustment on the propagation path, adjust the grid scale and time step of the offset area, and obtain the spatiotemporal discrete optimization result of the lightning electromagnetic field.

[0169] See also Figure 7 , the specific steps for obtaining the far-field intensity distribution data of the lightning electromagnetic field are as follows:

[0170] S511: Based on the spatiotemporal discrete optimization results of the lightning electromagnetic field, the distribution of the electric field and the magnetic field is used to determine the change trend of the electromagnetic field energy, classify the energy intensity in each grid area, detect the energy concentration area and the diffusion area, and generate energy distribution data on the lightning electromagnetic field propagation path;

[0171] First, in the optimized discrete grid area, the electric field components are extracted according to the predetermined spatial step size. And the magnetic field component The instantaneous value of the electromagnetic field is obtained, and the electromagnetic field data in different grid units are classified to filter out abnormal values ​​that appear in the time evolution process, such as the electric field strength points with excessive instantaneous jumps, to ensure data continuity and calculation stability. Then, the spatial area is divided, and the electromagnetic energy density is used as the classification basis. The energy distribution in each grid unit is statistically analyzed to identify the area where the electromagnetic energy is more concentrated. According to the threshold judgment standard, for example, the electromagnetic energy density threshold is set to , all satisfied The grid cells are classified as high energy areas, which will satisfy The grids are classified as low-energy areas, and data are annotated for the two types of areas. On this basis, the spatial gradient of electromagnetic energy is calculated to obtain the trend of energy diffusion or local aggregation. According to the distribution of different energy areas, the energy space division structure is established, and the energy distribution matrix is ​​generated according to the position correlation information of the grid cells. Finally, the energy distribution data on the propagation path of the lightning electromagnetic field is obtained.

[0172] S512: Based on the energy distribution data on the lightning electromagnetic field propagation path and according to the change of electromagnetic field intensity in the far field area, the electric field and magnetic field data at various distance positions are screened to determine the field intensity distribution trend in the far field area, identify the influencing factors of the field intensity change, and obtain the far field electric field intensity data of the lightning electromagnetic field;

[0173] First, obtain the electric field and magnetic field strength data of the far field area and set the far field calculation range, such as setting the starting distance of the far field area , end distance , select multiple observation points to record the electric field strength and magnetic field strength , for the values ​​obtained from different observation points, the weighted average is used to calculate the equivalent field strength in each distance interval. Subsequently, the data is screened to exclude observations with low signal-to-noise ratio, and the sliding mean method is used to smooth the field strength curve to ensure the continuity of the data. Next, the rate of change of the electromagnetic field intensity in the far field area with distance is calculated, the attenuation characteristics of the electromagnetic field in the far field area are identified, and the main factors affecting the field strength distribution are analyzed, such as terrain reflection, ionospheric absorption, and propagation path loss. On this basis, the electric field strength data in the far field area are normalized, and the far-field electromagnetic field strength change trend curve is generated based on the spatial distribution relationship, and finally the far-field electric field strength data of the lightning electromagnetic field is obtained.

[0174] S513: Based on the far-field electric field strength data of the lightning electromagnetic field, the field strength data of the azimuth angle in the grid space is sorted out to establish a field strength distribution structure in the far-field area, and obtain the far-field field strength distribution data of the lightning electromagnetic field;

[0175] First, based on the spatial grid division parameters of the far field region, the azimuth angle is selected and elevation As the coordinate variable, the electromagnetic field strength distribution structure in the spherical coordinate system is established, and the electric field strength in different azimuth angle ranges is normalized to keep the field strength data in different angle regions in the same dimension. Subsequently, the average field strength in each angle region is calculated, and the field strength data of the unmeasured area is filled in using the interpolation method to establish a complete far-field field strength distribution matrix. According to the field strength distribution characteristics, the changing trend of the field strength with angle is analyzed, and finally the far-field field strength distribution data of the lightning electromagnetic field is obtained.

[0176] The above are only preferred embodiments of the present invention and are not intended to limit the present invention in other forms. Any technician familiar with the profession may use the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes and apply them to other fields. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A high-precision calculation method for realizing far-field calculation of lightning electromagnetic field, characterized in that: The following steps are involved: S1: Based on remote sensing data and surface measurement data, the surface characteristics and atmospheric parameters on the lightning electromagnetic field propagation path are obtained, the dielectric constant change rate is recorded, and the lightning electromagnetic field environment parameter set is obtained; S2: Based on the lightning electromagnetic field environment parameter set, the influence of the surface roughness on the electromagnetic wave reflection power is analyzed and the propagation loss parameter is adjusted to obtain the lightning electromagnetic field medium influence correction result; S3: Based on the lightning electromagnetic field medium influence correction result, extract the boundary area where the dielectric characteristics suddenly change on the propagation path, determine the change trend of the refraction path, calculate the equivalent reflectivity change value and refractive index adjustment amount of the sudden change boundary area, adjust the boundary conditions of the nonlinear partial differential equation, and obtain the lightning electromagnetic field dynamic boundary correction result; S4: based on the dynamic boundary correction result of the lightning electromagnetic field, the refraction and attenuation changes after boundary adjustment are calculated, the spatiotemporal offset area on the propagation path is determined, the grid scale and time step are adjusted, and the spatiotemporal discrete optimization result of the lightning electromagnetic field is obtained; S5: Based on the spatiotemporal discrete optimization result of the lightning electromagnetic field, analyzing the energy distribution of the optimized lightning electromagnetic field propagation path, and obtaining the far-field strength distribution data of the lightning electromagnetic field.

2. The high-precision calculation method capable of realizing far-field calculation of lightning electromagnetic field according to claim 1 is characterized in that: The lightning electromagnetic field environmental parameter set includes surface roughness, wettability, particle size, terrain undulation, dielectric constant, atmospheric temperature, air density, humidity, refractive index, and time variation trend of surface dielectric constant; the lightning electromagnetic field medium influence correction result includes reflected power, scattering angle, reflection loss, attenuation parameter, refractive index change data, electromagnetic wave propagation loss, refractive index correction factor, reflectivity correction factor, and scattering correction factor; the lightning electromagnetic field dynamic boundary correction result includes dielectric constant spatial distribution, magnetic permeability spatial distribution, refractive index spatial distribution, mutation boundary area, refractive path variation trend, equivalent reflectivity variation value, refractive index adjustment amount, electromagnetic wave reflection coefficient, electromagnetic wave transmission coefficient, and nonlinear partial differential equation boundary condition; the lightning electromagnetic field spatiotemporal discrete optimization result includes refraction variation of electromagnetic wave propagation path, attenuation variation of electromagnetic wave propagation path, spatiotemporal offset area, grid scale, and time step; the lightning electromagnetic field far-field field strength distribution data includes lightning electromagnetic field propagation path, energy distribution, and far-field electromagnetic field value.

3. The high-precision calculation method capable of realizing far-field calculation of lightning electromagnetic field according to claim 2 is characterized in that: The steps for obtaining the lightning electromagnetic field environment parameter set are specifically as follows: S111: Acquire remote sensing data and surface measurement data, extract the surface roughness, wettability, particle size, terrain undulation and dielectric constant along the lightning electromagnetic field propagation path, record the initial state and spatial distribution of each parameter, and obtain the surface parameter data set; S112: Obtain the atmospheric temperature, air density, humidity and refractive index of multiple altitude layers, analyze the vertical distribution trend of the atmospheric parameters of each altitude layer, and obtain the atmospheric parameter data set of the altitude layer; S113: Based on the surface parameter data set and the altitude layer atmospheric parameter data set, the formula is used: ； Calculate the time rate of change of the dielectric constant of the surface , according to the rate of change Analyze the dynamic change characteristics of dielectric constant, record the time change trend of surface dielectric constant, and combine all environmental parameters to obtain the lightning electromagnetic field environmental parameter set; in, Representative time The surface dielectric constant at time represents the surface dielectric constant at the previous time step, is the total number of time steps.

4. The high-precision calculation method capable of realizing far-field calculation of lightning electromagnetic field according to claim 3 is characterized in that: The steps for obtaining the correction result of the lightning electromagnetic field medium influence are specifically as follows: S211: Based on the lightning electromagnetic field environment parameter set, analyzing the influence of the surface roughness in the lightning electromagnetic field propagation path on the electromagnetic wave reflection power and scattering angle, determining the reflection power and scattering angle under each roughness condition, and obtaining the influence data of the surface roughness on the reflection power and scattering angle; S212: Based on the data of the influence of the surface roughness on the reflected power and the scattering angle, the formula is used: ； Calculate the correction factor for reflection loss caused by changes in humidity ; in, Represents the reflection loss correction factor caused by the change in humidity, represents the dielectric constant of wet soil, represents the base dielectric constant of dry soil, represents the reflectivity of dry soil; S213: Extract the refractive index change data of each altitude layer and analyze the electromagnetic wave propagation loss caused by the change of air density. The formula is: ； Correction factor for reflection loss Make adjustments and calculate the adjusted reflection loss correction factor , and obtain the correction result of medium influence on lightning electromagnetic field; in, is the correction factor for reflection loss due to humidity changes, is the amplification factor of the refractive index change on the reflection loss, is the refractive index of the current air layer, is the refractive index of the reference air layer.

5. The high-precision calculation method capable of realizing far-field calculation of lightning electromagnetic field according to claim 4, characterized in that: The step of calculating the equivalent reflectivity change value and the refractive index adjustment amount of the sudden change boundary area is specifically as follows: S311: Based on the lightning electromagnetic field medium influence correction result, analyze the spatial distribution of the dielectric constant, magnetic permeability and refractive index in the lightning electromagnetic field propagation path, extract the dielectric constant change rate, magnetic permeability change rate and refractive index change rate of each spatial position point, screen the boundary area where the dielectric characteristics have mutations, and obtain the distribution data of the mutation boundary area; S312: Based on the mutation boundary area distribution data, the formula is used: ； Calculate the change in equivalent reflectivity in the mutation boundary area , according to the change value of equivalent reflectivity Determine the change trend of the refraction path of electromagnetic waves in the sudden change boundary area and obtain the analysis results of the equivalent reflectivity change; in, Represents the reflectivity of the reference medium in the abrupt boundary area, Represents the change in dielectric constant in the abrupt boundary area, Represents the dielectric constant of the reference medium in the abrupt boundary region, Represents the change in magnetic permeability in the sudden change boundary area, Represents the magnetic permeability of the reference medium in the abrupt boundary region; S313: Based on the equivalent reflectivity change analysis result, the formula is used: ， ； Calculate the correction amount of the refractive index due to the change of the dielectric constant and the correction of the refractive index due to the change in magnetic permeability ; in, represents the dielectric constant of the abrupt boundary region, Represents the dielectric constant of the reference medium in the abrupt boundary region, Represents the refractive index of the reference medium in the abrupt boundary region, represents the magnetic permeability of the abrupt boundary region, Represents the magnetic permeability of the reference medium in the abrupt boundary area.

6. The high-precision calculation method capable of realizing far-field calculation of lightning electromagnetic field according to claim 5, characterized in that: The steps for obtaining the dynamic boundary correction result of the lightning electromagnetic field are specifically as follows: S321: Correction of refractive index based on the dielectric constant change and the correction of the refractive index due to the change in magnetic permeability , using the formula: ； Calculate the corrected refractive index ; in, represents the reference refractive index before correction, that is, the refractive index not affected by the changes in dielectric constant and magnetic permeability; S322: Based on the corrected refractive index , using the formula: ； Calculate the corrected reflection coefficients and transmission coefficient ; in, is the refractive index of the incident medium; S323: Based on the corrected reflection coefficient and transmission coefficient , using the formula: ； Calculate boundary condition corrections , the corrected boundary conditions of the nonlinear partial differential equation are obtained, the corrected boundary conditions are applied in the process of solving the lightning electromagnetic field, the nonlinear partial differential equation is numerically calculated, the dynamic distribution of the lightning electromagnetic field is solved, and the dynamic boundary correction results of the lightning electromagnetic field are obtained.

7. The high-precision calculation method capable of realizing far-field calculation of lightning electromagnetic field according to claim 6, characterized in that: The steps for obtaining the spatiotemporal discrete optimization results of the lightning electromagnetic field are specifically as follows: S411: Based on the dynamic boundary correction result of the lightning electromagnetic field, the formula is used: ； Calculate the change in refraction angle of electromagnetic waves in the boundary area ; in, represents the angle of incidence, represents the corrected refractive index, represents the refractive index of the incident medium; Based on the change of the refraction angle of the electromagnetic wave in the boundary area , using the formula: ； Calculate the change in refraction of the electromagnetic wave propagation path after boundary adjustment ; in, Represents the benchmark propagation distance; S412: Based on the refraction change of the electromagnetic wave propagation path after the boundary adjustment , using the formula: ； Calculate the adjusted electromagnetic wave attenuation ; in, Represents the reference attenuation, represents the attenuation factor; S413: Setting a spatial step size on the propagation path to determine the initial spatial grid scale, and adjusting the refraction change of the electromagnetic wave propagation path according to the boundary. and the adjusted electromagnetic wave attenuation , determine the spatiotemporal offset area caused by boundary adjustment on the propagation path, adjust the grid scale and time step of the offset area, and obtain the spatiotemporal discrete optimization result of the lightning electromagnetic field.

8. The high-precision calculation method capable of realizing far-field calculation of lightning electromagnetic field according to claim 7, characterized in that: The steps for acquiring the lightning electromagnetic field far-field intensity distribution data are specifically as follows: S511: Based on the spatiotemporal discrete optimization result of the lightning electromagnetic field, according to the distribution of the electric field and the magnetic field, determine the change trend of the electromagnetic field energy, classify the energy intensity in each grid area, detect the energy concentration area and the diffusion area, and generate energy distribution data on the lightning electromagnetic field propagation path; S512: Based on the energy distribution data on the lightning electromagnetic field propagation path, according to the change of electromagnetic field intensity in the far field area, the electric field and magnetic field data at various distance positions are screened to determine the field intensity distribution trend in the far field area, identify the influencing factors of the field intensity change, and obtain the far-field electric field intensity data of the lightning electromagnetic field; S513: Based on the far-field electric field strength data of the lightning electromagnetic field, the field strength data of the azimuth angle in the grid space are sorted out to establish a field strength distribution structure in the far-field region, and obtain the far-field field strength distribution data of the lightning electromagnetic field.

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