A digital holography-based hail momentum measurement method

Abstract

The present application relates to a kind of hail momentum measurement methods based on digital holography, including steps S01: by holographic hail spectrometer, the basic parameters of hail momentum measurement are collected;Step S03: the momentum of single hail particle is measured;Step S04: based on the measurement result of single hail particle momentum, the measurement of batch hail momentum is measured and the hail momentum spectrum reflecting the distribution characteristics of hail momentum is constructed, and the quantitative statistical measurement of hail momentum is completed.Accurate, differentiated calculation of the momentum of single hail particle is realized;A complete technical process of hail momentum measurement is established, integrated measurement from air hail particle parameter collection to momentum spectrum output is realized;Quantitative statistics and visual analysis of hail momentum are realized.

Description

Technical Field

[0001] This invention belongs to the fields of meteorology, weather modification, and disaster reduction and prevention, and specifically relates to a method for measuring hail momentum based on digital holography. Background Technology

[0002] Digital holography records holograms of objects using photoelectric imaging devices, and then reconstructs the object's three-dimensional shape and physical parameters using computer digital reconstruction. This enables non-contact, high-precision parameter detection of micro / macro particles. Hailstone momentum is the product of the hailstone particle's mass and its falling velocity. The mass of hailstones can be derived from their particle size, morphology, and density, which is a well-known and fundamental formula for calculating hailstone momentum in this field.

[0003] In the field of hail monitoring, traditional hail spectrometers can measure basic parameters such as hail particle size and quantity, providing basic data support for hail momentum estimation. This is the conventional technical understanding of those skilled in the art.

[0004] Existing technologies for measuring hail momentum all rely on indirect estimation methods, lacking a direct and precise measurement approach. The mainstream implementations fall into two categories, both revolving around obtaining the fundamental parameters for momentum calculation: 1. Ground-Sampling Hail Momentum Estimation Scheme: This scheme collects ground-falling hailstones using a mechanical sampling device (net method), measures parameters such as hailstone size and mass, estimates the average falling velocity of the hailstones using empirical meteorological formulas, and then substitutes these values ​​into the momentum formula to obtain the hailstone momentum value. This scheme uses ground-falling hailstones as the measurement object, obtains mass parameters manually / by instruments, and uses velocity as an empirical estimate without actual measurement data.

[0005] 2. Optical Imaging Hail Momentum Estimation Scheme: This scheme uses ordinary CCD imaging and laser scattering technology (such as laser precipitation particle spectrometer and two-dimensional raindrop meter) to photograph hailstones in the air, extracts the two-dimensional apparent particle size parameters of the hailstones, estimates the hailstone mass based on a spherical model, and simultaneously obtains an approximate hailstone velocity through multi-device velocities or statistical algorithms, thereby calculating momentum. This scheme can achieve aerial hailstone monitoring, but the particle size is a two-dimensional approximation and the velocity is a statistical estimate, neither of which is precise measurement data.

[0006] Neither of the above two schemes has a dedicated technical process for hail momentum measurement. They obtain momentum values ​​indirectly through "basic parameter estimation + formula substitution". Furthermore, there is no dedicated model or spectrum construction method for hail momentum measurement in the existing technology, which makes it impossible to achieve accurate and batch measurement of hail momentum.

[0007] The core shortcomings of existing technologies lie in the accuracy, directness, and systematic nature of hail momentum measurement, specifically: 1. Low accuracy in obtaining fundamental momentum parameters: In terms of mass, the mass may be distorted due to the breaking / melting of hailstones upon landing, or the volume estimation may be biased due to the use of a spherical model to fit non-spherical hailstones; in terms of velocity, all are estimated by empirical formulas / statistical algorithms, without actual precise measurement data. Errors in fundamental parameters directly lead to large deviations in momentum calculation results.

[0008] 2. There is no direct method for measuring hail momentum: Existing technologies are all indirect estimations that involve "measuring basic parameters first and then substituting them into the formula." There is no dedicated technical process for hail momentum measurement, from accurate parameter acquisition to momentum calculation. The measurement process lacks systematicity.

[0009] 3. Inability to accurately calculate the momentum of a single hailstone: Because parameters such as particle size, velocity, and density are all overall / statistical estimates, it is impossible to accurately calculate the momentum of a single hailstone, nor is it possible to measure the momentum of different hailstones in a differentiated manner.

[0010] 4. Lack of batch measurement and spectrum construction capability for hail momentum: Existing technologies can only obtain average estimates of hail momentum, and cannot perform batch measurement of the momentum of multiple hail particles, nor can they construct momentum spectra that reflect the distribution characteristics of hail momentum, thus failing to achieve quantitative and visual analysis of hail momentum. Summary of the Invention

[0011] The purpose of this invention is to solve the problems of the inability to accurately and synchronously obtain the basic parameters (particle size, morphology, and falling velocity) for hail momentum measurement in existing technologies, which leads to the inability to provide data support for accurate calculation of hail momentum; the inability to perform batch measurement of hail momentum; the inability to construct hail momentum spectra; and the inability to achieve quantitative statistical and visual analysis of hail momentum.

[0012] To achieve the above objectives, the present invention provides a method for measuring hail momentum based on digital holography, comprising the following steps: Step S01: Collect basic parameters for hail momentum measurement using a holographic hail spectrometer; Step S03: Measure the momentum of a single hailstone particle; Step S04: Based on the momentum measurement results of a single hailstone, measure the momentum of a batch of hailstones and construct a hailstone momentum spectrum that reflects the momentum distribution characteristics of hailstones, thus completing the quantitative statistical measurement of hailstone momentum.

[0013] Specifically, step S01 includes: 1.1 Hailstone particle morphology parameter acquisition: Based on the holographic hailstone spectrometer, the holograms are processed by a digital holographic reconstruction algorithm to restore the three-dimensional morphology of the hailstone particles and extract the three-dimensional morphological parameters for momentum calculation, including the equivalent diameter, major axis, minor axis, perimeter, area, and roundness of the hailstone particles. 1.2. Acquisition of falling velocity parameters: Accurate measurement of the falling velocity of hail particles is achieved through multiple samplings in a single exposure. The specific process is as follows: ① Acquire a sequence of frames showing the motion trajectories of hail particles within the sampling area during a single exposure cycle of a CMOS camera; ②Based on the pulse interval of the pulsed laser and the displacement of hail particles in the image, combined with the imaging ratio of the CMOS camera lens, the displacement in the image is converted into the actual spatial displacement. Substituting this into the velocity formula: v=Δs / Δt, where Δs is the actual spatial displacement and Δt is the pulse interval, the falling velocity of a single hail particle is calculated.

[0014] The specific process of step S03 is as follows: 3.1 Substitute the equivalent diameter, major axis, and minor axis of the hail particles extracted in step S01 into the ellipsoid volume formula. Where a and b are the major and minor axes of the hail particle, respectively, the volume of a single hail particle is calculated. 3.2. Based on the equivalent diameter and falling velocity of a single hailstone, match the corresponding density value. The specific process is as follows: ① Based on the experimental data and industry standards of hail microphysical characteristics in the meteorological field, establish a hail density correlation table corresponding to different equivalent diameters and different falling velocities. The density value range in the table is 700~920kg / m³. ② Extract the equivalent diameter D and falling velocity v of a single hailstone from the effective parameter library, and perform precise matching in the hailstone density association table to obtain the exclusive density value ρ corresponding to the particle; ③ If the equivalent diameter or falling velocity of the particle falls within the range of the hail density correlation table, use linear interpolation to calculate its corresponding density value to ensure the continuity and accuracy of density assignment, and then substitute it into the mass formula. The mass of a single hailstone particle was calculated, providing core data for momentum calculation.

[0015] 2.3 Substitute the falling velocity v and mass m of a single hailstone particle directly into the hailstone momentum calculation formula: , combined The calculation formula is obtained as follows: The momentum value of a single hailstone particle is calculated, thus completing the momentum measurement of a single particle.

[0016] The specific process of step S04 is as follows: 4.1 Batch Momentum Calculation: For each valid hail particle, step S03 is executed to measure the momentum of different hail particles, complete the momentum calculation of each hail particle, and obtain the batch measurement results of the momentum of all hail particles in the sampling area. 4.2. Size Division: Based on the measured equivalent diameter of hail particles, hail particles are divided into bins, and multiple size intervals are divided according to preset intervals to obtain the momentum distribution of hail particles in each interval. 4.3 Momentum Distribution Statistics: Based on the spatial density data of hail particles in the sampling area, the number of hail particles, number concentration, and momentum ratio in each interval are statistically analyzed. 4.4 Momentum Spectrum Construction: The total momentum of all effective hail particles within a unit time and a unit sampling volume is statistically analyzed to obtain the total momentum within a unit time and volume. The momentum distribution is then statistically analyzed according to the equivalent diameter of the hail particles to achieve quantitative acquisition of the hail momentum spectrum.

[0017] After step S01 and before step S03, there is also step S02, which involves eliminating invalid particles and screening valid targets for momentum measurement. The specific process is as follows: 2.1 Establishing a screening feature library: Based on the microphysical characteristics of hail particles, roundness, equivalent diameter range, and falling speed range are selected as screening indicators to establish a screening feature library. The roundness screening threshold is set to 0.5 to 1.0, the equivalent diameter screening threshold is set to 5 mm to 40 mm, and the falling speed screening threshold is set to 5 to 30 m / s. 2.2 Multi-feature fusion screening: The roundness, equivalent diameter, and falling speed of each particle are quantitatively calculated, and the calculation results are compared with the corresponding screening thresholds. Particles whose roundness, equivalent diameter, and falling speed all meet the threshold requirements are judged as valid hail particles; otherwise, they are judged as invalid particles that do not meet the threshold requirements. 2.3 Invalid particle removal and valid particle storage: Invalid particles are directly deleted from the parameter library; the three-dimensional morphological parameters, falling velocity parameters, and spatial position information of valid hail particles are uniformly stored in the valid parameter library for hail momentum measurement, and numbered according to the spatial position of the valid hail particles.

[0018] The beneficial effects of this invention are: it enables accurate and differentiated calculation of the momentum of individual hail particles; it establishes a complete technical process for hail momentum measurement, realizing integrated measurement from aerial hail particle parameter acquisition to momentum spectrum output; and it achieves quantitative statistical and visual analysis of hail momentum.

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the optical path for digital holographic observation of a holographic hail spectrometer.

[0021] Figure 2 This is a schematic diagram of a method for measuring the momentum of hail based on digital holography.

[0022] Figure 3 This is a diagram illustrating the momentum model of hail.

[0023] Figure 4 It is a momentum spectrum diagram of hail.

[0024] Figure 5 It is the overall software design of the holographic hail spectrometer.

[0025] Explanation of reference numerals in the attached diagram: 1. Laser; 2. Polarizer; 3. Beam expander; 4. Plano-convex lens group; 5. First mirror; 6. Second mirror; 7. CMOS camera; 8. Miniature lens. Detailed Implementation

[0026] The present invention will be further described below with reference to the embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0027] To address the numerous shortcomings of existing technologies, this embodiment employs the following technical concept: Centered on precise hail momentum measurement, it leverages digital holography and single-exposure multiple-sampling techniques to achieve precise and synchronous acquisition of three-dimensional morphological parameters (equivalent diameter, major and minor axes, etc.) and falling velocity parameters of aerial hail particles. An ellipsoidal model is used to fit the hail particle morphology, and the hail density is dynamically assigned based on the relationship between hail diameter and falling velocity, accurately deriving the mass of a single hail particle. The precisely measured mass and velocity are then substituted into the momentum formula to directly calculate the momentum of a single hail particle. Through batch calculation of the momentum of multiple hail particles, combined with spatial density data, the particle distribution characteristics of different momentum intervals are statistically analyzed to construct a hail momentum spectrum, ultimately forming a complete hail momentum measurement method from parameter acquisition to momentum spectrum output. This achieves quantitative statistical and visual analysis of hail momentum, realizing integrated measurement from aerial hail particle parameter acquisition to momentum spectrum output.

[0028] In specific implementation, the hail momentum measurement method based on digital holography provided in this embodiment is completed using a holographic hail spectrometer (HHM), the hardware of which includes... Figure 1The device shown includes a pulsed laser 1, a polarizer 2 (which converts the beam into linearly polarized light), a beam expander 3, a plano-convex lens group 4, a first reflector 5, a second reflector 6, a CMOS camera 7, and a miniature lens 8. Its built-in hardware modules comprise four core modules: hologram processing, particle parameter extraction, momentum calculation, and momentum spectrum construction. The built-in software utilizes mature, existing technologies. Hologram processing is performed by a hologram processing module, which denoises, reconstructs, and segments the raw holograms acquired by the CMOS camera, outputting clear two-dimensional / three-dimensional particle contour images to provide basic data for subsequent parameter extraction. This mainly includes: Background subtraction: Subtracting two holograms every other frame to remove fixed background noise, stray light, and optical inhomogeneities from the particle-containing hologram, eliminating fixed pattern noise. Numerical reconstruction: Using a Fresnel diffraction algorithm, the hologram after background subtraction is digitally focused to reconstruct the three-dimensional light field distribution of the particles within the detection volume, obtaining a clear focused image of the particles. Binarization: Adaptive thresholding is applied to the reconstructed image to separate the particle region from the background, facilitating subsequent contour extraction and pixel statistics. Denoising and morphological optimization: Opening / closing operations are performed on the binary image to remove isolated noise points and fill in voids within particles, ensuring complete particle contours and continuous edges.

[0029] The particle parameter extraction module automatically identifies individual hailstones and accurately extracts their microphysical parameters based on the processed binary holographic image. The core of this process is converting pixel information into actual physical dimensions. This mainly involves pixel-to-physical-size conversion: after identifying a single hailstone from the binary image, the system calculates the total number of pixels occupied by a single particle based on a fixed pixel physical size and the lens magnification (e.g., 1 pixel = 3.45 μm, magnification 0.168). Combining the pixel size and magnification, the system can calculate parameters such as the particle's equivalent diameter, major and minor axes, circumference, area, and roundness.

[0030] Momentum calculation, based on a single-exposure, multiple-sampling technique, accurately measures the falling velocity of hail particles. This mainly includes: Velocity inversion: By acquiring the particle's trajectory within a single exposure time using a CMOS camera, matching the position of the same particle at different moments, and combining this with the pulse interval Δt, the falling velocity is calculated. Invalid particle removal: Hail particles are often accompanied by interference from raindrops and broken particles during their fall; therefore, valid hail particle targets are selected based on three conditions: equivalent diameter, roundness, and falling velocity. Mass estimation: After selecting valid hail particles, the particle mass m is calculated using the equivalent diameter D of the hailstone, a hail density model (e.g., ρ = 0.9 g / cm³), and the ellipsoidal volume formula. Momentum calculation: The momentum of a single hailstone is calculated according to the definition of momentum p = m・v.

[0031] The momentum spectrum construction module statistically analyzes a large amount of hail particle momentum data to generate a hail momentum spectrum distribution for hail dynamic characteristic analysis and disaster assessment. This mainly includes: Interval division: Based on measured momentum data, bins are divided according to logarithmic or linear intervals of particle diameter. Particle counting: The momentum of all valid hail particles is assigned to corresponding intervals based on diameter, and the number of particles and their momentum sum within each interval are counted. Spectrum distribution fitting: The measured momentum spectrum is fitted using a power-law function model, and the resulting momentum spectrum is output for easy comparison with other observations and model applications.

[0032] This method revolves entirely around hail momentum measurement, from the precise acquisition of basic parameters for momentum calculation, to the calculation of momentum of a single particle, and then to batch measurement and momentum spectrum construction, forming an integrated technical process. The specific implementation steps are as follows: Step S1: Place the holographic hail spectrometer at the designated hail observation location, ensuring the instrument is securely installed, the lens is unobstructed, and it is aimed at the core area of ​​the falling hail. Then, connect the power to the holographic hail spectrometer and start the instrument control system. Configure the instrument parameters according to the preset observation requirements. After the parameters are configured and confirmed to be correct, for example, set the camera gain to between 5 and 10, the exposure time to 3100 microseconds, and the pulse interval to 1 millisecond. Start the camera acquisition function. The camera will continuously capture holograms of the falling hail according to the set parameters. Simultaneously, the acquired hologram data will be stored in real time to the instrument's built-in storage module. During the acquisition process, monitor the instrument's operating status in real time to avoid external factors such as stray light and vibration affecting the data acquisition quality.

[0033] Step S2: Accurate and synchronous acquisition of basic parameters for hail momentum measurement S2.1 Hailstone Particle Morphology Parameter Acquisition In a holographic hail spectrometer, a portion of the coherent light emitted by the pulsed laser 1 illuminates hail particles within the sampling area and is scattered to become object light. The other portion of the coherent light serves as reference light, illuminating a CMOS camera. When the object light illuminates the CMOS camera, it interferes with the reference light at the photosensitive surface of the CMOS camera (or CCD camera) to form a hologram. This hologram contains the three-dimensional morphological information of the hail particles. The holographic hail spectrometer's built-in hologram processing module processes the hologram using a digital holographic reconstruction algorithm to reconstruct the three-dimensional morphology of the hail particles. The particle parameter extraction module extracts core morphological parameters used for momentum calculation, such as the equivalent diameter, major and minor axes, circumference, area, and roundness of the hail particles, providing accurate data for subsequent mass derivation.

[0034] S2.2 Falling speed parameter acquisition Based on a single-exposure, multiple-sampling technique, the precise measurement of hail particle falling velocity is achieved. The specific process is as follows: ① Within a single exposure cycle of the CMOS camera, a sequence of frame sequences of hail particle motion trajectories within the sampling area is acquired. ② Based on the pulse interval of the pulsed laser and the calculated displacement, combined with the lens's imaging ratio, the displacement in the image is converted into the actual spatial displacement. Substituting this into the velocity formula v=Δs / Δt (Δs is the actual spatial displacement, Δt is the pulse interval), the momentum calculation module calculates the precise falling velocity of a single hail particle.

[0035] Step S3: Eliminate invalid particles and screen for valid targets for momentum measurement. In addition to valid hail particles, the sampling area also contains invalid particles such as raindrops, broken hail particles, and air impurities. These particles differ significantly from hail particles in morphology and velocity characteristics, and including them in momentum measurements would distort the results. This step establishes a multi-feature fusion particle selection model to intelligently eliminate particles from the parameter extraction process, retaining only valid targets that match the characteristics of hail particles. This ensures the accuracy of the data source for subsequent momentum measurements. The specific process is as follows: 1. Establish a screening feature library: Combining the microphysical characteristics of hail particles, three core features are selected as screening indicators: roundness, equivalent diameter range, and falling velocity range of hail particles. The roundness screening threshold is set to 0.5-1.0 (the roundness of hail particles is mostly above 0.5, the roundness of raindrops is close to 1.0, and the roundness of impurities is mostly below 0.4). The equivalent particle size screening threshold is set to 5mm-40mm (the equivalent particle size of hail particles is mostly greater than 5mm). The falling velocity screening threshold is set to 5-30m / s (the falling velocity of hail particles is mostly between 5 and 30m / s, and the falling velocity of raindrops is mostly between 1 and 10m / s).

[0036] 2. Multi-feature fusion screening: For each particle with extracted parameters, the three core features are quantified and calculated. The calculation results are compared with the screening threshold. Particles that meet the threshold requirements for all three features are determined to be valid hail particles, and particles that do not meet the threshold requirements for any one feature are determined to be invalid particles.

[0037] 3. Invalid particle removal and valid particle storage: For particles determined to be invalid, all their data are directly deleted from the parameter library; for particles determined to be valid hailstones, their associated three-dimensional morphological parameters, falling velocity parameters, and spatial position information are uniformly stored in the valid parameter library for hailstone momentum measurement, and numbered according to the spatial position of the particles, providing an accurate and clean data source for subsequent momentum calculation of individual particles.

[0038] Step S4: Precise derivation of the mass of a single hailstone particle Mass is a core fundamental parameter for hail momentum measurement. This application, considering the non-spherical nature of hail, employs an ellipsoidal model for volume fitting and combines this with a dynamic density assignment strategy to derive the precise mass of a single hail particle. Specifically: Based on the major and minor axes and equivalent diameter parameters of the hail particles extracted in step 2, substitute them into the ellipsoid volume formula. ,in The precise volume of a single hailstone is calculated by taking the major and minor axes of the hailstone particles, respectively. Abandoning the existing method of uniformly assigning density values, a correlation model of hail equivalent diameter, falling velocity, and density is established. Based on the equivalent diameter and falling velocity of a single hailstone particle, a precise density value is matched. The specific process is as follows: ① Based on experimental data and industry standards of hail microphysical characteristics in the meteorological field, a hail density correlation table is established corresponding to different equivalent diameters and falling velocities. The density values ​​in the table range from 700 to 920 kg / m³ (small-diameter hailstones have a density close to 920 kg / m³, while large-diameter, high-velocity hailstones have lower densities due to the presence of internal air bubbles); ② The equivalent diameter D and falling velocity v of a single hailstone particle are extracted from an effective parameter library and precisely matched in the density correlation table to obtain the specific density value ρ corresponding to that particle; ③ If the equivalent diameter or falling velocity of the particle falls within the range of the correlation table, linear interpolation is used to calculate its corresponding density value to ensure the continuity and accuracy of density assignment, which is then substituted into the mass formula. The precise mass of a single hailstone particle was calculated, providing core data for accurate momentum calculation.

[0039] Step S5: Precise calculation of the momentum of a single hailstone particle To achieve direct hail momentum measurement, the falling velocity v of a single hail particle, accurately measured in step S2, and the mass m of a single hail particle, accurately derived in step S4, are directly substituted into the core formula for calculating hail momentum: , combined The calculation formula is obtained as follows: The precise momentum value of a single hailstone is calculated, completing the momentum measurement of a single particle. This step is performed for each valid hailstone to achieve differentiated and precise measurement of the momentum of different hailstones.

[0040] Step S6: Batch measurement of hail momentum and construction of momentum spectrum Based on the momentum measurement results of individual hail particles, batch measurements of hail momentum are achieved, and a hail momentum spectrum reflecting the distribution characteristics of hail momentum is constructed to complete the quantitative statistical measurement of hail momentum. Specifically: Batch momentum calculation: For all valid hail particles after screening in step S3, execute steps S4 and S5 in sequence to complete the momentum calculation of each particle and obtain the batch momentum measurement results of hail particles in the sampling area. Hailstone size range division: Hailstones are divided into bins based on the measured equivalent diameter of the hailstones, and multiple size ranges are divided at preset intervals to obtain the momentum distribution of hailstones in each range. Momentum distribution statistics: Based on the spatial density data of hail particles in the sampling area, the number of hail particles, number concentration, momentum ratio and other parameters in each interval are statistically analyzed; Momentum spectrum construction: The total momentum of all effective hail particles within a unit time and a unit sampling volume is statistically analyzed to obtain the total momentum within a unit time and volume. The momentum distribution is then statistically analyzed according to the equivalent diameter of the hail particles to achieve quantitative acquisition of the hail momentum spectrum.

[0041] Step S7: Output and Application of Hail Momentum Measurement Results The momentum measurements of individual hail particles, statistical data from batch measurements, and hail momentum spectra are output in standardized formats (numerical tables, graphs, and distribution maps). The measurement results can be directly applied to scenarios such as assessing the destructive capacity of hail disasters (momentum values ​​are positively correlated with hail destructive power) and judging the effectiveness of hail suppression operations (comparing changes in momentum spectra before and after operations), providing accurate momentum data support for relevant decision-making.

[0042] In summary, it is clear that this embodiment features a dedicated process for momentum measurement. It utilizes digital holographic technology to accurately acquire the three-dimensional morphological parameters of hailstones, employs a single-exposure, multiple-sampling technique to precisely measure the falling velocity, and derives accurate mass using an ellipsoidal model and dynamic density assignment. All fundamental parameters are actual measurements / precisely derived values, not empirical estimates. This overcomes the limitations of indirect estimation in existing technologies, enabling direct calculation of the momentum of a single hailstone particle. It solves the problem of momentum calculation deviations caused by errors in fundamental parameters, significantly improving the accuracy of hailstone momentum measurement.

[0043] Instead of using overall statistical parameters, this method collects morphological and velocity parameters, derives mass, and calculates momentum for each effective hailstone individually. This overcomes the limitation of existing technologies that can only obtain average momentum values, and can accurately obtain the momentum value of each hailstone, reflecting the momentum differences of hailstones of different sizes and shapes. This provides data support for analyzing the individual characteristics of hailstones' destructive potential.

[0044] By measuring the momentum of individual particles, the momentum of a batch of hailstones is calculated, and a hailstone momentum spectrum is constructed by statistically analyzing the particle distribution characteristics across different momentum ranges. This fills the gap in existing technologies that lack the capability for batch measurement and spectrum construction of hailstone momentum. It can intuitively reflect the distribution characteristics of hailstone momentum within the sampling area, enabling quantitative statistical analysis and visualization of hailstone momentum, thus making the hailstone momentum measurement results more valuable for practical applications.

[0045] This technology utilizes digital holography to collect parameters of hail particles in the air without contact. All measurement steps are completed automatically by software, requiring no manual intervention or hail sampling upon landing. It solves the problems of poor real-time performance of existing technologies and the limitation of optical imaging to only measuring two-dimensional parameters. It can capture the momentum changes of hail particles in real time, enabling dynamic momentum monitoring throughout the entire hail disaster process and providing accurate real-time data for hail disaster early warning.

[0046] The design encompasses a complete technical process, from momentum measurement system setup, basic parameter acquisition, invalid particle removal, and individual particle momentum calculation to batch measurement, momentum spectrum construction, and result output. All steps revolve around hail momentum measurement. It overcomes the shortcomings of existing technologies that lack a dedicated hail momentum measurement process, forming a systematic and integrated hail momentum measurement method that can be directly applied to various hail monitoring scenarios, offering convenient operation and strong versatility.

[0047] The output of individual momentum values, batch statistical data, and momentum spectra can directly reflect the destructive power of hail (the greater the momentum, the stronger the destructive force). The effectiveness of hail suppression operations can be quantified by comparing changes in momentum spectra before and after the operation. This solves the problem of low application value of existing momentum estimation values. The measurement results can directly provide accurate data support for the quantitative assessment of hail disasters and the optimization of hail suppression operation plans, greatly improving the practical application value of hail momentum measurement.

[0048] The preferred embodiments of the present invention disclosed above are only for illustrating the present invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to specific implementations. Obviously, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.

Claims

1. A method for measuring the momentum of hail based on digital holography, characterized in that, Includes the following steps: Step S01: Collect basic parameters for hail momentum measurement using a holographic hail spectrometer; Step S03: Measure the momentum of a single hailstone particle; Step S04: Based on the momentum measurement results of a single hailstone, measure the momentum of a batch of hailstones and construct a hailstone momentum spectrum that reflects the momentum distribution characteristics of hailstones, thus completing the quantitative statistical measurement of hailstone momentum.

2. The hail momentum measurement method based on digital holography according to claim 1, characterized in that, Step S01 includes, 1.1 Hailstone particle morphology parameter acquisition: Based on the holographic hailstone spectrometer, the holograms are processed by a digital holographic reconstruction algorithm to restore the three-dimensional morphology of the hailstone particles and extract the three-dimensional morphological parameters for momentum calculation, including the equivalent diameter, major axis, minor axis, perimeter, area, and roundness of the hailstone particles. 1.

2. Acquisition of falling velocity parameters: Accurate measurement of the falling velocity of hail particles is achieved through multiple samplings in a single exposure. The specific process is as follows: ① Acquire a sequence of frames showing the motion trajectories of hail particles within the sampling area during a single exposure cycle of a CMOS camera; ②Based on the pulse interval of the pulsed laser and the displacement of hail particles in the image, combined with the imaging ratio of the CMOS camera lens, the displacement in the image is converted into the actual spatial displacement, and then substituted into the velocity formula: v = Δs / Δt, where Δs is the actual spatial displacement and Δt is the pulse interval, thus calculating the falling velocity of a single hailstone particle.

3. The hail momentum measurement method based on digital holography according to claim 2, characterized in that, The specific process of step S03 is as follows: 3.1 Substitute the equivalent diameter, major axis, and minor axis of the hail particles extracted in step S01 into the ellipsoid volume formula. Where a and b are the major and minor axes of the hail particle, respectively, the volume of a single hail particle is calculated. 3.

2. Based on the equivalent diameter and falling velocity of a single hailstone particle, a corresponding density value is matched. The specific process is as follows: ①Based on experimental data and industry standards on the microphysical characteristics of hail in the meteorological field, a hail density correlation table is established for different equivalent diameters and different falling speeds. The density values ​​in the table range from 700 to 920 kg / m³. ② Extract the equivalent diameter D and falling velocity v of a single hailstone from the effective parameter library, and perform precise matching in the hailstone density association table to obtain the exclusive density value ρ corresponding to the particle; ③ If the equivalent diameter or falling velocity of the particle falls within the range of the hail density correlation table, use linear interpolation to calculate its corresponding density value to ensure the continuity and accuracy of density assignment, and then substitute it into the mass formula. The mass of a single hailstone particle was calculated, providing core data for momentum calculation; 2.3 Substitute the falling velocity v and mass m of a single hailstone particle directly into the hailstone momentum calculation formula: , combined The calculation formula is obtained as follows: The momentum value of a single hailstone particle is calculated, thus completing the momentum measurement of a single particle.

4. The hail momentum measurement method based on digital holography according to claim 3, characterized in that, The specific process of step S04 is as follows: 4.1 Batch Momentum Calculation: For each valid hail particle, step S03 is executed to measure the momentum of different hail particles, complete the momentum calculation of each hail particle, and obtain the batch measurement results of the momentum of all hail particles in the sampling area. 4.

2. Size Division: Based on the measured equivalent diameter of hail particles, hail particles are divided into bins, and multiple size intervals are divided according to preset intervals to obtain the momentum distribution of hail particles in each interval. 4.3 Momentum Distribution Statistics: Based on the spatial density data of hail particles in the sampling area, the number of hail particles, number concentration, and momentum ratio in each interval are statistically analyzed. 4.4 Momentum Spectrum Construction: The total momentum of all effective hail particles within a unit time and a unit sampling volume is statistically analyzed to obtain the total momentum within a unit time and volume. The momentum distribution is then statistically analyzed according to the equivalent diameter of the hail particles to achieve quantitative acquisition of the hail momentum spectrum.

5. The hail momentum measurement method based on digital holography according to claim 1, 2, or 3, characterized in that, After step S01 and before step S03, there is also step S02, which involves eliminating invalid particles and screening valid targets for momentum measurement. The specific process is as follows: 2.1 Establishing a screening feature library: Based on the microphysical characteristics of hail particles, roundness, equivalent diameter range, and falling speed range are selected as screening indicators to establish a screening feature library. The roundness screening threshold is set to 0.5 to 1.0, the equivalent diameter screening threshold is set to 5 mm to 40 mm, and the falling speed screening threshold is set to 5 to 30 m / s. 2.2 Multi-feature fusion screening: The roundness, equivalent diameter, and falling speed of each particle are quantitatively calculated, and the calculation results are compared with the corresponding screening thresholds. Particles whose roundness, equivalent diameter, and falling speed all meet the threshold requirements are judged as valid hail particles; otherwise, they are judged as invalid particles that do not meet the threshold requirements. 2.3 Invalid particle removal and valid particle storage: Invalid particles are directly deleted from the parameter library; the three-dimensional morphological parameters, falling velocity parameters, and spatial position information of valid hail particles are uniformly stored in the valid parameter library for hail momentum measurement, and numbered according to the spatial position of the valid hail particles.

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