CN118011358A - Rain drop spectrum inversion method and device for dual-band radar - Google Patents
Rain drop spectrum inversion method and device for dual-band radar Download PDFInfo
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Abstract
The invention provides a raindrop spectrum inversion method and device for a dual-band radar, belonging to the technical field of atmosphere detection, and comprising the following steps: according to the X/Ka dual-band radar observation data, determining an X/Ka dual-band radar dual-frequency ratio, so as to determine the liquid water content and the Ka/W dual-band radar dual-frequency ratio; according to whether the double-frequency ratio of the X/Ka wave band radar is zero, selecting the double-frequency ratio of the Ka/W wave band radar or determining the mass weighted average diameter of the raindrops according to the double-frequency ratio of the X/Ka wave band radar; and finally determining the distribution of the raindrop spectrum according to the weighted average diameter of the raindrop mass and the liquid water content. The invention solves the problem of double solutions between the double frequency ratio and the weighted average diameter of the raindrops when the raindrops spectrum is inverted by the double-band radar, does not need to classify the precipitation process and introduce adjustment factors, ensures that the inverted raindrops spectrum is more accurate in distribution, and can greatly improve the research level of aspects such as radar meteorology, cloud numerical mode parameterization, weather artificial influence and the like.
Description
Technical Field
The invention relates to the technical field of atmosphere detection, in particular to a method and a device for inverting a raindrop spectrum of a dual-band radar.
Background
In cloud precipitation microphysics research, almost all problems relate to particle size, so particle size is a very important, most fundamental parameter. And the raindrop spectrum (Drop Size Distribution, DSD) is a basic description of the raindrop scale distribution, and DSD reflects the change of the raindrop number concentration of a certain particle diameter range in unit volume along with the scale. The DSD is researched to be helpful for improving the accuracy of radar quantitative rainfall estimation, improving or optimizing the parameterization scheme of the atmospheric climate mode and improving the weather effect of artificial influence. Accurate acquisition of large-scale DSD has been one of the important research directions in radar meteorology.
DSD can be measured directly by a raindrop spectrometer, but ground or on-board raindrop spectrometers cannot obtain DSD information in large scale, high spatial-temporal resolution. Therefore, currently, DSD with large range and high space-time resolution is obtained through inversion in a radar remote sensing mode.
In the prior art, when DSD inversion analysis is carried out, a generalized DFR-D m inversion method of the relation between the radar double-frequency ratio DFR and the raindrop mass weighted average diameter D m is mainly adopted, or an R-D m inversion method of the relation between the rainfall ratio R and the rainfall ratio D m is adopted.
When the generalized DFR-D m inversion method is adopted, the double-solution problem of the DFR-D m is solved by setting the adjustment factor, the advantage that the DFR is only a D m function is sacrificed, and the inversion accuracy is reduced. When the R-D m inversion method is adopted, the precipitation type is required to be classified artificially, and a new adjustment factor is introduced at the same time, namely a new error is required to be introduced, and the inversion result is also inaccurate.
Disclosure of Invention
The invention provides a method and a device for inverting a raindrop spectrum of a dual-band radar, which are used for solving the defect that double solutions exist due to DFR-D m inversion in the prior art, can solve the double solution problem of DFR-D m inversion, and are more accurate in inverting the raindrop spectrum without classifying a precipitation process and introducing an adjustment factor.
In a first aspect, the present invention provides a method for inverting a raindrop spectrum of a dual-band radar, including:
acquiring X/Ka dual-band radar observation data in a detection range;
Determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data;
Determining a Ka band reflectivity factor true value according to the X/Ka band radar double-frequency ratio and the X band reflectivity factor true value; determining the liquid water content and the Ka/W band radar double-frequency ratio according to the Ka band reflectivity factor true value;
under the condition that the X/Ka band radar double-frequency ratio is less than or equal to zero, determining the raindrop mass weighted average diameter according to the Ka/W band radar double-frequency ratio;
Under the condition that the X/Ka band radar double-frequency ratio is larger than zero, determining the raindrop mass weighted average diameter according to the X/Ka band radar double-frequency ratio;
correcting the raindrop mass weighted average diameter by using a conversion function under the condition that the raindrop mass weighted average diameter is determined to be in a first preset range and the double-frequency ratio of the X/Ka band radar is smaller than a second preset range;
Determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content;
The first preset range, the second preset range and the transfer function are predetermined by inversion using historical observation data.
In a second aspect, the invention further provides a dual-band radar raindrop spectrum inversion device, which comprises a data acquisition unit and a data inversion unit, wherein:
the data acquisition unit is used for acquiring X/Ka dual-band radar observation data in a detection range;
A data inversion unit for performing the following operations:
Determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data;
Determining a Ka band reflectivity factor true value according to the X/Ka band radar double-frequency ratio and the X band reflectivity factor true value;
Determining the liquid water content and the Ka/W band radar double-frequency ratio according to the Ka band reflectivity factor true value;
under the condition that the X/Ka band radar double-frequency ratio is less than or equal to zero, determining the raindrop mass weighted average diameter according to the Ka/W band radar double-frequency ratio;
Under the condition that the X/Ka band radar double-frequency ratio is larger than zero, determining the raindrop mass weighted average diameter according to the X/Ka band radar double-frequency ratio;
and determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content.
In a third aspect, the present invention provides an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of any one of the two-band radar raindrop spectrum inversion methods described above when the program is executed.
In a fourth aspect, the present invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of any of the two-band radar raindrop spectrum inversion methods described above.
In a fifth aspect, the present invention also provides a computer program product comprising a computer program which when executed by a processor implements the steps of a dual band radar raindrop spectrum inversion method as described in any one of the above.
The raindrop spectrum inversion method and the device for the dual-band radar, provided by the invention, solve the double-solution problem of DFR-D m when the raindrop spectrum is inverted by the X/Ka dual-band radar, and establish the raindrop spectrum inversion method based on the DFR, wherein the inversion method does not need to classify the precipitation process, does not need to introduce adjustment factors, and has the advantages compared with the R-D m raindrop spectrum inversion method adopted by the current GPM satellite, and the raindrop spectrum inversion method is more accurate.
Drawings
In order to more clearly illustrate the invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a scatter plot schematic of a prior art X/Ka dual band radar DFR-D m obtained when performing scatter simulation;
FIG. 2 is a scatter plot of an X/Ka dual-band radar DFR-D m obtained using prior art generalized DFR-D m inversion;
FIG. 3 is a schematic flow chart of the raindrop spectrum inversion method of the dual-band radar provided by the invention;
FIG. 4 is a schematic flow chart of simulating the relation between radar parameters and fitting by using T matrix scattering;
FIG. 5 is a second flow chart of the method for inverting raindrop spectrum of the dual-band radar provided by the invention;
FIG. 6 is a schematic diagram of the scatter points of the DFR-D m without TF conversion provided by the present invention;
FIG. 7 is a scatter plot of the TF-converted DFR-D m;
FIG. 8 is a schematic structural diagram of a dual-band radar raindrop spectrum inversion device provided by the invention;
FIG. 9 is a schematic representation of an X/Ka dual band reflectance factor observation taken at the proximal end provided by the present invention;
FIG. 10 is a schematic representation of an X/Ka dual band reflectance factor observation taken at a remote end provided by the present invention;
FIG. 11 is a schematic diagram of the differential attenuation rate of the X/Ka dual band provided by the present invention;
FIG. 12 is a schematic illustration of the X-band attenuation ratio provided by the present invention;
FIG. 13 is a schematic diagram of the true value of the X-band reflectance factor provided by the present invention;
FIG. 14 is a schematic diagram of the dual frequency ratio of an X/Ka band radar provided by the present invention;
FIG. 15 is a schematic diagram of a true value of the Ka-band reflectance factor provided by the present invention;
FIG. 16 is a schematic diagram of a Ka/W band radar dual-band ratio provided by the present invention;
FIG. 17 is a graph comparing inversion and true values of mass-weighted average diameters provided by the present invention;
FIG. 18 is a graph comparing inversion and true values of liquid water content provided by the present invention;
FIG. 19 is a graph comparing normalized number concentration inversion values with true values provided by the present invention;
FIG. 20 is a graph of the comparison of inverted and measured raindrop spectra for an X-band reflectance factor of 23.4dBZ provided by the present invention;
FIG. 21 is a graph of an inverted raindrop spectrum versus an actual measured raindrop spectrum for an X-band reflectance factor of 36.7dBZ provided by the present invention;
FIG. 22 is a graph of the comparison of inverted and measured raindrop spectra for an X-band reflectance factor of 46.9dBZ provided by the present invention;
FIG. 23 is a graph of an inverted raindrop spectrum versus an actual measured raindrop spectrum for an X-band reflectance factor of 53.4dBZ provided by the present invention;
fig. 24 is a schematic structural diagram of an electronic device provided by the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that in the description of the present invention, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. The orientation or positional relationship indicated by the terms "upper", "lower", etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description and to simplify the description, and are not indicative or implying that the apparatus or elements in question must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and "coupled" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
The terms "first," "second," and the like in this specification are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged, as appropriate, such that embodiments of the present invention may be implemented in sequences other than those illustrated or described herein, and that the objects identified by "first," "second," etc. are generally of a type, and are not limited to the number of objects, such as the first object may be one or more. In addition, "and/or" indicates at least one of the connected objects, and the character "/", generally indicates that the associated object is an "or" relationship.
Dual wave radars are widely used for raindrop spectrum inversion because they can provide radar dual frequency ratios (Dual Frequency Ratio, DFR) that are related only to the distribution characteristics of the raindrop spectrum, but not to the concentration of precipitation particles.
Wherein the definition of the radar double frequency ratio DFR is shown in the formula (1):
（1）
Wherein, Is of low frequency band,/>Is of high frequency band,/>Is the reflectivity of the low-frequency band,/>The reflectivity of the high-frequency wave band; dB is a pure count unit representing the logarithm between the reflectivity of the low frequency band and the reflectivity of the high frequency band.
The currently adopted raindrop spectrum model is generally expressed by using standard Gamma particle spectrum distribution, and the expression is shown in a formula (2):
（2）
（3）
Is rain drop spectrum distribution,/> Is the shape factor of the raindrops, Γ is the gamma function, D is the particle diameter of the raindrops,As an intermediate variable function.
The average diameter is weighted for the mass of the raindrops, which refers to the ratio of the mass accumulated value of all raindrops to the diameter accumulated value of all raindrops.
The normalized number concentration is the number distribution of raindrops with different diameters in a unit volume, and the normalized number concentration can eliminate scale effects of the raindrop spectrum under different rainfall events or different environments, so that the raindrop spectrum under different conditions can be compared and analyzed.
Under the Gamma particle spectrum distribution condition, the DFR is only a function of the raindrop mass weighted average diameter D m and the shape factor [ mu ] of the raindrops, and when the raindrops are in a liquid state, the [ mu ] is 3, and then the DFR is only a function of D m.
Fig. 1 is a schematic diagram of scattering points of an X/Ka dual-band radar DFR-D m obtained during scattering simulation in the prior art, and as shown in fig. 1, when a raindrop is in a liquid state, and the mu is 3, and when DFR >0, a unique solution exists in the DFR-D m, and D m can be obtained through DFR inversion. However, when the DFR is equal to or less than 0, the DFR corresponds to two D m (as shown by the dashed box area in FIG. 1), then a unique D m cannot be obtained by the DFR inversion.
To solve the double-solution problem of DFR-D m, the prior art provides a generalized DFR-D m inversion method, whose defined expression is shown in formula (4):
（4）
wherein, gamma is an adjustment factor, and gamma is [0,0.8].
FIG. 2 is a schematic view of the scatter points of the X/Ka dual-band radar DFR-D m obtained by inversion with the prior art generalized DFR-D m, where γ=0.8 is set, as can be seen in FIG. 2The corresponding D m also has a unique solution.
Although the generalized DFR-D m inversion method described above solves the double solution problem of D m, due to the DFRThe method is not the only function of D m and is also the function of the normalized number concentration N W, so that the advantage that the DFR is only the function of D m is sacrificed, and the accuracy of the generalized DFR-D m inversion method is lower than that of the conventional DFR-D m inversion method.
The prior art provides another dual-band raindrop spectrum inversion algorithm, and a global precipitation observation GPM satellite is used for carrying a Ku/Ka dual-band radar so as to implement an R-D m inversion method based on the relation between the rainfall rate R and the D m. However, because the association between the rainfall rates R and D m shows a great difference with different precipitation types, the inversion method needs to manually classify the precipitation types in advance, mainly divide the precipitation types into lamellar cloud precipitation and convective cloud precipitation, and then invert the precipitation types to obtain D m respectively, wherein the corresponding inversion expression is shown in formula (5) and formula (6):
（5）
（6）
Wherein, formula (5) is for R-D m inversion when the type of precipitation is laminar cloud rainfall, formula (6) is for R-D m inversion when the type of precipitation is convective cloud rainfall, epsilon is an adjustment factor, and R is rainfall rate.
According to the formula (5) and the formula (6), the R-D m inversion method avoids the problem of double solutions of the DFR-D m, but introduces an adjustment factor epsilon and needs to classify the precipitation process, which tends to introduce new errors, and the inversion result is inaccurate.
In view of the above, the invention provides an X/Ka dual-band radar raindrop spectrum inversion method based on DFR-D m, which can solve the problem of double solutions of DFR-D m, does not need to classify precipitation processes and introduce adjustment factors, and has the advantages of being more accurate than the R-D m raindrop spectrum inversion method adopted by the conventional GPM satellite. The invention has great application value and popularization prospect, and can be popularized and applied to inversion of rain drop spectrums of various spaceborne and foundation dual-band radars.
The method and the device for inverting the raindrop spectrum of the dual-band radar provided by the invention are described below with reference to fig. 3 to 9.
FIG. 3 is a schematic flow chart of the method for inverting raindrop spectrum of the dual-band radar provided by the invention, as shown in FIG. 3, including but not limited to the following steps:
and step 1, acquiring X/Ka dual-band radar observation data in a detection range.
The invention performs raindrop spectrum inversion by collecting X/Ka dual-band radar observation data, and the following provides an implementation mode for obtaining X/Ka dual-band radar observation data in a detection range:
(1) And (3) radar equipment setting and calibration: ensuring that the radar apparatus in the X-band and Ka-band are properly installed, calibrated and in operation. This includes examining the antenna, receiver, transmitter, and associated signal processing system of the radar.
(2) Setting a data acquisition mode: and setting a proper radar data acquisition mode according to the research requirements and the detection range. This may include setting parameters such as scan speed, scan range, resolution, etc.
(3) Data receiving and storing: after data acquisition is started, the radar starts to receive precipitation echo signals from different directions and different heights. These signals, after processing, will be converted to digital data and stored in a computer or dedicated data storage device as X/Ka dual band radar observations.
Specifically, the acquired X/Ka dual-band radar observation data mainly includes original echo data, X/Ka dual-band reflectivity factor observation values, and the like, and may also include spectral width and speed data, dual-polarization data, and the like, which is not particularly limited in this invention.
The original echo data are unprocessed precipitation echo signals directly received by the X/Ka dual-band radar, and the signals contain scattering information of precipitation particles and are the basis of subsequent inversion of a raindrop spectrum.
The X/Ka dual band reflectivity factor observations are reflectivity factor data obtained by processing the raw echo data. The reflectivity factor is an important parameter for describing the rainfall intensity, and has important significance for raindrop spectrum inversion.
The spectral width and the speed data are information reflecting the speed distribution and the spectral width of precipitation particles in the radar beam direction, and a certain basis can be provided for analyzing the dynamic characteristics of a precipitation system and raindrop spectrum inversion. Of course, if the radar supports dual polarized observation, echo data in both the horizontal and vertical polarization directions may also be acquired. These data may provide more information about precipitation particle shape, size, and phase, helping to improve the accuracy of the raindrop spectrum inversion.
And 2, determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data.
According to the method, the radar double-frequency ratio of the X/Ka wave band is calculated by analyzing the radar reflectivities of two different frequencies (the X wave band and the Ka wave band), and the obtained radar double-frequency ratio can provide information about the size and the distribution of precipitation particles so as to be used as a basis for accurately deducing a raindrop spectrum subsequently.
Radar reflectivity factor Z is a parameter describing the echo intensity of precipitation and is related to the size, density and phase (typically expressed by a form factor) of the precipitation particles. Of course, for different radar frequencies, the same precipitation system may generate different reflectivity factor values, the invention selects the radar adopting the X wave band and the Ka wave band through repeated experiments, and the size distribution information of precipitation particles is represented by calculating the ratio of the reflectivity factor observations of the X wave band and the Ka wave band.
The method for determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data mainly comprises the following steps:
Firstly, preprocessing the obtained X/Ka dual-band radar observation data, including removing noise, calibrating, controlling quality and the like, so as to ensure the accuracy and reliability of the radar observation data.
And calculating the differential attenuation rate of the X/Ka dual-band radar according to the reflectivity factor observed values of the X/Ka dual-band radar at the near end and the far end.
Further, the X/Ka dual-band differential attenuation rate and the X-band attenuation rate can be utilized according to the X/Ka dual-band differential attenuation rateThe first functional relation between the two is inverted to deduce the attenuation rate/>, within the detection range, of the X-band。
Using attenuation ratio in the X-bandAfter correcting the observed value of the X-band reflectivity factor, the method can be used for correcting the true value/>, according to the corrected X-band reflectivity factorTrue value/>, using pre-constructed X-band reflectivity factorsDouble-frequency ratio/>, with X/Ka wave band radarThe second functional relation between the two is inverted to obtain the double-frequency ratio of the X/Ka wave band radar in the detection range。
The first functional relation and the second functional relation are constructed in advance by carrying out scattering calculation on collected actually measured raindrop spectrum data and fitting.
True value is generated according to the double-frequency ratio of the X/Ka band radar and the X band reflectivity factorDetermining the true value/>, of the Ka band reflectivity factor。
Step 3, because the prior art utilizes the X/Ka band radar dual-frequency ratioWhen inversion of the rain drop spectrum is performed, the inversion occurs in the following wayWhen less than or equal to 0,/>The case of the weighted average diameter D m for two raindrops mass results in a failure of inversion.
The invention is realized by the following steps ofLess than or equal to 0 and/>Two cases >0 employ different inversion methods.
In particular, inUnder the condition of less than or equal to 0, firstly, according to the double-frequency ratio/>, of the X/Ka band radarTrue value/>, obtained by inversion, of X-band reflectivity factorObtaining the true value/>, of the Ka band reflectivity factor。
Based on the foregoing embodiment, as an alternative embodiment, in determining the X/Ka band radar dual-band ratioGreater than zero, further comprising:
according to the X/Ka band radar double-frequency ratio Determining the raindrop mass weighted average diameter D m;
And determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter D m and the liquid water content LWC.
In particular, the invention is inIn the case of < 0, according to/>Inversion is carried out first to obtain the true value/>, of the Ka band reflectivity factorThen utilize Ka wave band reflectance factor true value/>Inversion is carried out to obtain a Ka/W wave band radar dual-frequency ratio/>To according to/>Inversion of the raindrop mass weighted average diameter D m was performed.
At the position ofWhen 0, the method can be based on the double frequency ratio/>, of the X/Ka band radarAnd a sixth functional relation between the raindrop mass weighted average diameter D m and the raindrop mass weighted average diameter D m is obtained through direct inversion.
In the above way, byThe two sections are separated for inversion, and the comprehensive utilization ofAnd/>The correlation characteristic with the raindrop mass weighted average diameter D m solves the problem of double solutions of the DFR-D m in the inversion of the raindrop spectrum of the dual-band radar, and a new adjustment factor is not required to be introduced in the whole process, so that more accurate raindrop spectrum distribution can be inverted.
Step 4, according to the Ka band reflectivity factor true valueDetermining the liquid water content and the Ka/W band radar dual-frequency ratio/>；
Can be true according to the Ka band reflectivity factorInversion is carried out by utilizing a pre-constructed third function to obtain a Ka/W wave band radar dual-frequency ratio/>。
Can also be true according to the Ka band reflectivity factorAnd inverting to obtain the liquid water content LWC by utilizing a fourth function relation constructed in advance.
Step 5, according to the Ka/W wave band radar double-frequency ratioDetermine/>And the weight average diameter D m of the corresponding raindrops is less than or equal to 0.
The obtained Ka/W wave band radar double-frequency ratioThe raindrop mass weighted average diameter D m can be obtained by inversion through inputting a fifth function which is constructed in advance.
Step 6, according to the X/Ka band radar double-frequency ratioDetermine/>And >0, the corresponding raindrop mass weighted average diameter D m.
The obtained X/Ka band radar double-frequency ratioThe raindrop mass weighted average diameter D m can be obtained by inversion through inputting a sixth function which is constructed in advance.
And 7, determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content.
The inversion of the raindrop spectrum can be performed by utilizing Gamma spectrum distribution according to the raindrop mass weighted average diameter D m and the liquid water content LWC.
The raindrop spectrum inversion method and the device for the dual-band radar provided by the invention solve the double-solution problem of DFR-D m when the raindrop spectrum is inverted by the X/Ka dual-band radar, and establish the raindrop spectrum inversion method based on the DFR, wherein the inversion method does not need to classify the precipitation process and introduce adjustment factors, and has the advantages compared with the R-D m raindrop spectrum inversion method adopted by the conventional GPM satellite, the inversion raindrop spectrum is more accurate, and the research level of radar meteorology, numerical mode parameterization, weather artificial influence and the like can be improved.
Fig. 4 is a schematic flow chart of simulating the relation between radar parameters and fitting by using T matrix scattering, as shown in fig. 4, before inversion of a raindrop spectrum, the invention can acquire and measure measured raindrop spectrum data in advance in a test mode, calculate and calculate parameters such as a weighted average diameter D m of raindrop mass and a liquid water content LWC by combining the measured raindrop spectrum data, and obtain the following parameters by using T matrix scattering simulation:
X-band attenuation rate A x and X/Ka dual-band differential attenuation rate True value/>, X-band reflectivity factorTrue value/>, ka band reflectivity factorTrue value/>, of W-band reflectivity factorX/Ka band radar dual-frequency ratio/>And Ka/W band radar dual-band/>Etc.
Then, by fitting the above parameters, the expression of the raindrop mass weighted average diameter D m and the liquid water content LWC is shown as formula (7) -formula (9):
（7）
（8）
（9）
wherein D is the diameter of raindrops, Maximum diameter of raindrops,/>Is the minimum diameter of raindrops,/>N (D) is the distribution of rain drops spectrum, which is the definition formula of the N-step distance.
T matrix scattering simulation is to solve the scattering problem of non-spherical particles by directly solving the Maxwell equation set, and link far-field scattered electromagnetic waves with incident electromagnetic waves to obtain a 4×4 backscattering phase matrix (also called Mueller matrix) and a2×2 forward scattering amplitude matrix.
Radar reflectivity (mm 6m-3) is defined as shown in equation (10):
(10)
Wherein lambda is wavelength, X-band wavelength is 32mm, ka-band wavelength is 9mm, W-band wavelength is 3mm, m is rain drop complex refractive index, and sigma H is horizontal back scattering section.
The radar reflectivity is represented by the T matrix element and becomes as shown in formula (11):
(11)
Wherein < is > represents the volume ensemble average of the raindrop phase matrix elements, Representing the total number of raindrops per cubic meter.K= (m 2-1)/(m2 +2), m is the rain drop complex refractive index,/>For the backscatter phase matrix, the radar reflectivity factor is typically expressed in 10lg (Z) in dBZ.
The decay rate expression is shown in formula (12):
(12)
wherein λ is the wavelength; im represents the imaginary part after integration; Is a forward scattering amplitude matrix.
Of the above parameters、/>And/>The expression of (a) is shown as formula (13) -formula (15):
（13）
（14）
（15）
Finally, the acquired measured raindrop spectrum data can be fitted to the following functional relationship, specifically as shown in the formula (16) -formula (21):
（16）
（17）
（18）
（19）
（20）
（21）
Wherein equation (16) is the first function mentioned above, equation (18) is the second function mentioned above, equation (19) is the third function, equation (17) is the fourth function mentioned above, equation (20) is the fifth function, and equation (21) is the sixth function mentioned above.
Fig. 5 is a second schematic flow chart of the dual-band radar raindrop spectrum inversion method provided by the present invention, and the following details of the specific embodiment of the present invention are described with reference to fig. 5:
As an alternative embodiment, the determining the dual-frequency ratio of the X/Ka-band radar according to the X/Ka dual-band radar observation data may include:
According to the X/Ka dual-band radar observation data, determining the X/Ka dual-band differential attenuation rate Inversion can be performed specifically using the following formula:
Wherein, For the X/Ka dual-band differential attenuation rate,/>Is near-end of radar,/>For the far-end of the radar,Representing the proximal/>Band reflectivity factor observations,/>Representing the far end/>Band reflectivity factor observations,/>Representing near-end X-band reflectivity factor observations,/>Representing the far-end X-band reflectance factor observations.
According to the X/Ka dual-band differential attenuation rateDetermining the attenuation rate of the X-band/>The inversion may be specifically performed by using the first functional relationship expressed by the formula (16), which is not described herein.
By using the X-band attenuation rateCorrecting the observed value of the X-band reflectivity factor to obtain the true value/>, of the X-band reflectivity factor。
Wherein the X-band reflectivity factor observation is one of the X/Ka dual-band radar observations.
Finally, the true value of the X-band reflectivity factor can be obtainedDetermining the double-frequency ratio of the X/Ka band radarThe inversion may be specifically performed by using the second functional relationship expressed by the formula (18), which is not described herein.
As another alternative embodiment, the functional expression for determining the true value of the Ka-band reflectivity factor according to the dual-band ratio of the X/Ka-band radar and the true value of the X-band reflectivity factor is shown in the formula (14), which is not described herein.
As another alternative embodiment, the functional expression for determining the dual-frequency ratio of the Ka/W band radar according to the true value of the Ka band reflectivity factor is shown in the formula (19), and will not be described herein.
As another alternative embodiment, the functional expression for determining the liquid water content according to the true value of the Ka-band reflectivity factor is shown in the formula (17), which is not described herein.
As another alternative embodiment, the function expression for determining the weighted average diameter of the raindrops by the Ka/W band radar double-frequency ratio is shown in the formula (20), and will not be described herein.
As another alternative embodiment, the functional expression for determining the weighted average diameter of the raindrops according to the X/Ka band radar dual-frequency ratio is shown in the formula (21), which is not described herein.
As another optional embodiment, substituting the weighted average diameter of the raindrop mass and the normalized number concentration into a Gamma spectrum distribution, the specific manner of obtaining the raindrop spectrum distribution of the detection range is:
Determining a normalized number concentration according to the liquid water content and the raindrop mass weighted average diameter;
Substituting the weighted average diameter of the raindrop mass and the normalized number concentration into Gamma spectrum distribution to obtain the raindrop spectrum distribution of the detection range, wherein the raindrop spectrum distribution can be shown by referring to the formulas (2) and (3), and the description is omitted here.
Wherein a normalized number concentration is determined based on the liquid water content and the raindrop mass weighted average diameterThe expression of (2) is shown in formula (22):
（22）
Wherein, For the normalized number concentration,/>For the liquid water content,/>Is the water density of raindrops,/>The average diameter is weighted for the raindrop mass.
The invention provides a raindrop spectrum inversion method for a dual-band radar, which is implemented by determiningWhen usingAnd carrying out inversion calculation of D m on the corresponding association relation between the D m and the D m.
Table 1 DFR numerical statistics
As shown in Table 1, by calculationThe number of DFRs less than or equal to 0 is greatly reduced, and the numerical ratio of DFR >0 capable of giving a unique solution is improved from 58.57% to 84.69%. FIG. 6 is a schematic view of the scattered points of the DFR-D m without TF conversion provided by the invention, as shown in FIG. 6, but the DFR (Ka, W). Ltoreq.0 also exists, resulting in certain errors in inversion D m.
In view of this, the present invention further comprises, after determining the raindrop mass weighted average diameter:
Correcting the raindrop mass weighted average diameter by using a conversion function TF under the condition that the raindrop mass weighted average diameter is determined to be in a first preset range and the double-frequency ratio of the X/Ka wave band radar is smaller than a second preset range;
the first preset range, the second preset range and the transfer function TF are predetermined by inversion using historical observation data.
As an alternative embodiment, the first preset range is shown in formula (23):
（23）
The second preset range is shown in formula (24):
（24）
the expression of the transfer function TF is shown in formula (25):
（25）
Wherein, For the X/Ka band radar dual-band ratio,/>The average diameter is weighted for the mass of the raindrops,And weighting the average diameter for the modified raindrop mass.
FIG. 7 is a schematic view of the scatter plot of the TF-converted DFR-D m, as shown in FIG. 7, with significantly reduced errors in the inverted and measured raindrop spectra after correction by the transfer function TF.
Fig. 8 is a schematic structural diagram of the dual-band radar raindrop spectrum inversion apparatus provided by the present invention, as shown in fig. 8, mainly including a data acquisition unit 81 and a data inversion unit 82, wherein:
the data acquisition unit 81 is mainly used for acquiring X/Ka dual-band radar observation data in a detection range.
The data inversion unit 82 is mainly used for performing the following operations:
according to the X/Ka dual-band radar observation data, determining the X/Ka dual-band radar dual-frequency ratio ；
According to the X/Ka band radar double-frequency ratioAnd X-band reflectance factor truth/>Determining the true value/>, of the Ka band reflectivity factor；
True value according to the Ka band reflectivity factorDetermining the double-frequency ratio/>, of the LWC and Ka/W wave band radars；
In determining the double-frequency ratio of the X/Ka band radarAnd under the condition of being smaller than or equal to zero, according to the Ka/W wave band radar dual-frequency ratio/>Determining the weighted average diameter of raindrops/>；
Weighted average diameter according to the raindrop massAnd the liquid water content LWC, determining the raindrop spectrum distribution of the detection range.
It should be noted that, when the dual-band radar raindrop spectrum inversion device provided by the present invention specifically operates, the dual-band radar raindrop spectrum inversion method described in any one of the foregoing embodiments may be executed, which is not described in detail in this embodiment.
The raindrop spectrum inversion device for the dual-band radar solves the double-solution problem of DFR-D m when the raindrop spectrum is inverted by the X/Ka dual-band radar, establishes a raindrop spectrum inversion method based on the DFR, does not need to classify a precipitation process, does not need to introduce an adjustment factor, has advantages compared with the R-D m raindrop spectrum inversion method adopted by the conventional GPM satellite, and inverts the raindrop spectrum more accurately.
In order to more intuitively explain the advancement of the inversion effect of the dual-band radar raindrop spectrum inversion method and the device provided by the invention compared with the existing raindrop spectrum inversion method, the invention is described below with reference to related test data:
According to the flow of the raindrop spectrum inversion method of the dual-band radar shown in fig. 5, the reflectivity factor observation value of the X/Ka dual-band is input first.
FIG. 9 is a schematic diagram of an X/Ka dual-band reflectance factor observation taken at a proximal end provided by the present invention, and FIG. 10 is a schematic diagram of an X/Ka dual-band reflectance factor observation taken at a distal end provided by the present invention, wherein Z x-Obs represents the X-band reflectance factor observation and Z Ka-Obs represents the Ka-band reflectance factor observation. As shown in connection with fig. 9 and 10, the observation time 2022, 6, 11, 4:19-16:19 spans 12 hours.
FIG. 11 is a schematic view of the X/Ka dual-band differential attenuation rate provided by the present invention, as shown in FIG. 11, the X/Ka dual-band differential attenuation rate is calculated from the acquired X/Ka dual-band radar observation data using the formula (21) provided in the above embodiment。
FIG. 12 is a schematic view of the X-band attenuation ratio provided by the present invention, as shown in FIG. 12, after calculating the dual-band differential attenuation ratioThe X-band attenuation rate/>, can then be calculated according to equation (16) in the above embodiment。
FIG. 13 is a schematic diagram of the true value of the X-band reflectance factor provided by the present invention, as shown in FIG. 13, after the X-band attenuation ratio is calculatedThereafter, the X-band attenuation rate/>, can be employedRevising the observed value of the X-band reflectivity factor to obtain the true value/>, of the X-band reflectivity factor。
FIG. 14 is a graph showing the dual-band ratio of the X/Ka band radar according to the present invention, as shown in FIG. 14, after obtaining the true value of the X-band reflectivity factorThen, the formula (18) provided by the embodiment can be adopted to invert to obtain the double frequency ratio/>, of the X/Ka band radar。
FIG. 15 is a graph showing the true value of the Ka-band reflectivity factor provided by the present invention, as shown in FIG. 15, using the X/Ka-band radar dual-band ratio according to equation (14) provided by the above embodimentAnd the true value of the X-band reflectivity factorCalculating to obtain true value/>, of Ka-band reflectivity factor。
FIG. 16 is a graph showing the dual-band ratio of the Ka/W band radar of the present invention, as shown in FIG. 16, using equation (15) to determine the true value of the reflectance factor according to the Ka bandCalculating the double frequency ratio/>, of the Ka/W wave band radar。
Finally, the double-frequency ratio of the radar can be calculated according to the X/Ka wave bandWhether is greater than 0 is judged by utilizing the double frequency ratio/>, of the X/Ka band radarOr utilize Ka/W wave band radar dual-frequency ratio/>To make raindrop mass weighted average diameter/>Is a function of the inversion of (a). Specific procedures can be referred to the raindrop mass weighted average diameter provided in any of the above embodimentsIs not described in detail herein.
FIG. 17 is a graph comparing inversion and true values of mass-weighted average diameters provided by the present invention, FIG. 18 is a graph comparing inversion and true values of liquid water content provided by the present invention, and FIG. 19 is a graph comparing inversion and true values of normalized number concentration provided by the present invention, wherein LWC represents the liquid water content inversion and LWC -est represents the liquid water content true value; d m represents the mass-weighted average diameter inversion value, D m-est represents the mass-weighted average diameter true value; n w represents a normalized number concentration inversion value, N w-rst represents a normalized number concentration true value, and as shown in fig. 17 to 19, the accuracy of the inversion value can be evaluated by an average deviation (Average Deviation) and a Correlation Coefficient (CC), and the average deviation and the correlation coefficient are defined as shown in formula (26) and formula (27):
（26）/>
（27）
Wherein, For the inversion value of the ith sample point,/>True value of the ith sampling point,/>Covariance of inversion value and true value of ith sampling point,/>For the inversion value variance of the ith sampling point,/>Is the true value variance of the ith sample point.
The average deviation AD represents the deviation between the inversion value and the true value, and the smaller the value is, the smaller the deviation between the inversion value and the true value is; the correlation coefficient CC represents the correlation degree of the inversion value and the true value, and the closer to 1, the higher the correlation is, and the specific comparison result can be shown in table 2:
Table 2 inversion evaluation
Fig. 20-23 are schematic diagrams showing comparison of measured raindrop spectra (solid lines) and inverted raindrop spectra (broken lines) under different reflectivity factors, DSD represents a raindrop spectrum true value, and DSD -est represents a raindrop spectrum inversion value.
Wherein, fig. 20 is a graph of comparing an inverted raindrop spectrum with an actual measured raindrop spectrum when the reflectivity factor provided by the invention is 23.4dBZ, fig. 21 is a graph of comparing an inverted raindrop spectrum with an actual measured raindrop spectrum when the reflectivity factor provided by the invention is 36.7dBZ, fig. 22 is a graph of comparing an inverted raindrop spectrum with an actual measured raindrop spectrum when the reflectivity factor provided by the invention is 46.9dBZ, and fig. 23 is a graph of comparing an inverted raindrop spectrum with an actual measured raindrop spectrum when the reflectivity factor provided by the invention is 53.4 dBZ.
As can be seen by comparison, the inversion method and the inversion device for the raindrop spectrum of the dual-band radar provided by the invention have the advantages that the obtained inversion raindrop spectrum has higher coincidence degree with the actually measured raindrop spectrum, and the actual situation of the raindrop spectrum is better reflected.
As an alternative embodiment, the raindrop spectrum inversion method and device for the dual-band radar provided by the invention adopt X/Ka dual-band radar observation data as an analysis object to invert the raindrop spectrum, and in fact, the raindrop spectrum inversion method for the dual-band radar provided by the invention is also applicable to Ka/W dual-band radar and Ku/Ka dual-band radar, and is used for inverting the raindrop spectrum under the conditions of cloud drop spectrum and weak precipitation, and the implementation principle is similar to that of the raindrop spectrum inversion method and device provided by the invention, and detailed description is omitted.
Fig. 24 is a schematic structural diagram of an electronic device according to the present invention, and as shown in fig. 24, the electronic device may include: processor 410, communication interface (Communications Interface) 420, memory 430, and communication bus 440, wherein processor 410, communication interface 420, and memory 430 communicate with each other via communication bus 440. The processor 410 may invoke logic instructions in the memory 430 to perform a dual band radar raindrop spectrum inversion method comprising: acquiring X/Ka dual-band radar observation data in a detection range; determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data; determining a Ka band reflectivity factor true value according to the X/Ka band radar double-frequency ratio and the X band reflectivity factor true value; determining the liquid water content and the Ka/W band radar double-frequency ratio according to the Ka band reflectivity factor true value; under the condition that the X/Ka band radar double-frequency ratio is less than or equal to zero, determining the raindrop mass weighted average diameter according to the Ka/W band radar double-frequency ratio; under the condition that the X/Ka band radar double-frequency ratio is larger than zero, determining the raindrop mass weighted average diameter according to the X/Ka band radar double-frequency ratio; and determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content.
Further, the logic instructions in the memory 430 described above may be implemented in the form of software functional units and may be stored in a computer-readable storage medium when sold or used as a stand-alone product. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In another aspect, the present invention also provides a computer program product comprising a computer program stored on a non-transitory computer readable storage medium, the computer program comprising program instructions which, when executed by a computer, are capable of performing the dual-band radar raindrop spectrum inversion method provided by the above embodiments, the method comprising: acquiring X/Ka dual-band radar observation data in a detection range; determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data; determining a Ka band reflectivity factor true value according to the X/Ka band radar double-frequency ratio and the X band reflectivity factor true value; determining the liquid water content and the Ka/W band radar double-frequency ratio according to the Ka band reflectivity factor true value; under the condition that the X/Ka band radar double-frequency ratio is less than or equal to zero, determining the raindrop mass weighted average diameter according to the Ka/W band radar double-frequency ratio; under the condition that the X/Ka band radar double-frequency ratio is larger than zero, determining the raindrop mass weighted average diameter according to the X/Ka band radar double-frequency ratio; and determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content.
In yet another aspect, the present invention further provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, is implemented to perform the dual-band radar raindrop spectrum inversion method provided by the above embodiments, the method comprising: acquiring X/Ka dual-band radar observation data in a detection range; determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data; determining a Ka band reflectivity factor true value according to the X/Ka band radar double-frequency ratio and the X band reflectivity factor true value; determining the liquid water content and the Ka/W band radar double-frequency ratio according to the Ka band reflectivity factor true value; under the condition that the X/Ka band radar double-frequency ratio is less than or equal to zero, determining the raindrop mass weighted average diameter according to the Ka/W band radar double-frequency ratio; under the condition that the X/Ka band radar double-frequency ratio is larger than zero, determining the raindrop mass weighted average diameter according to the X/Ka band radar double-frequency ratio; and determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The raindrop spectrum inversion method for the dual-band radar is characterized by comprising the following steps of:
acquiring X/Ka dual-band radar observation data in a detection range;
Determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data;
Determining a Ka band reflectivity factor true value according to the X/Ka band radar double-frequency ratio and the X band reflectivity factor true value; determining the liquid water content and the Ka/W band radar double-frequency ratio according to the Ka band reflectivity factor true value;
under the condition that the X/Ka band radar double-frequency ratio is less than or equal to zero, determining the raindrop mass weighted average diameter according to the Ka/W band radar double-frequency ratio;
Under the condition that the X/Ka band radar double-frequency ratio is larger than zero, determining the raindrop mass weighted average diameter according to the X/Ka band radar double-frequency ratio;
correcting the raindrop mass weighted average diameter by using a conversion function under the condition that the raindrop mass weighted average diameter is determined to be in a first preset range and the double-frequency ratio of the X/Ka band radar is smaller than a second preset range;
Determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content;
The first preset range, the second preset range and the transfer function are predetermined by inversion using historical observation data.
2. The dual-band radar raindrop spectrum inversion method of claim 1, wherein said determining the X/Ka-band radar dual-frequency ratio from the X/Ka dual-band radar observation data comprises:
According to the X/Ka dual-band radar observation data, determining an X/Ka dual-band differential attenuation rate;
determining the X-band attenuation rate according to the X/Ka dual-band differential attenuation rate;
Correcting an X-band reflectivity factor observation value by utilizing the X-band attenuation rate to obtain an X-band reflectivity factor true value, wherein the X-band reflectivity factor observation value is one of the X/Ka dual-band radar observation data;
And determining the double-frequency ratio of the X/Ka band radar according to the true value of the X band reflectivity factor.
3. The raindrop spectrum inversion method of the dual-band radar according to claim 2, wherein the function expression for determining the differential attenuation rate of the dual-band X/Ka according to the observed data of the dual-band X/Ka radar is:
；
Wherein, For the X/Ka dual-band differential attenuation rate,/>Is near-end of radar,/>For the far-end of radar,/>Representing the near-end Ka-band reflectance factor observations,/>Representing the far-end Ka band reflectance factor observations,Representing near-end X-band reflectivity factor observations,/>Representing a far-end X-band reflectivity factor observation value;
The function expression for determining the X-band attenuation rate according to the X/Ka dual-band differential attenuation rate is as follows:
；
Wherein, The attenuation rate of the X wave band is set;
The function expression for determining the double-frequency ratio of the X/Ka band radar according to the true value of the X band reflectivity factor is as follows:
；
Wherein, For the X/Ka band radar dual-band ratio,/>True value of the X-band reflectivity factor;
The function expression for determining the double-frequency ratio of the Ka/W band radar according to the true value of the Ka band reflectivity factor is as follows:
；
Wherein, And the Ka/W band radar double-frequency ratio is obtained.
4. A method of inverting a raindrop spectrum of a dual band radar according to any one of claims 1 to 3, wherein the function expression for determining the raindrop mass weighted average diameter according to the Ka/W band radar dual frequency ratio is:
；
Wherein, The average diameter is weighted for the raindrop mass.
5. A method of inverting a raindrop spectrum of a dual band radar according to any one of claims 1 to 3, wherein the function expression for determining the raindrop mass weighted average diameter according to the X/Ka band radar dual frequency ratio is:
；
Wherein, The average diameter is weighted for the raindrop mass.
6. The method for inverting the raindrop spectrum of a dual-band radar according to claim 1, wherein,
The first preset range is as follows:；
the second preset range is as follows: ；
The expression of the transfer function is: ；
Wherein, For the X/Ka band radar dual-band ratio,/>Weighting the average diameter for said raindrops mass,/>And weighting the average diameter for the modified raindrop mass.
7. The utility model provides a dual-band radar raindrop spectrum inversion device which characterized in that, includes data acquisition unit and data inversion unit, wherein:
the data acquisition unit is used for acquiring X/Ka dual-band radar observation data in a detection range;
A data inversion unit for performing the following operations:
Determining the double-frequency ratio of the X/Ka band radar according to the X/Ka double-band radar observation data;
Determining a Ka band reflectivity factor true value according to the X/Ka band radar double-frequency ratio and the X band reflectivity factor true value; determining the liquid water content and the Ka/W band radar double-frequency ratio according to the Ka band reflectivity factor true value;
under the condition that the X/Ka band radar double-frequency ratio is less than or equal to zero, determining the raindrop mass weighted average diameter according to the Ka/W band radar double-frequency ratio;
Under the condition that the X/Ka band radar double-frequency ratio is larger than zero, determining the raindrop mass weighted average diameter according to the X/Ka band radar double-frequency ratio;
and determining the raindrop spectrum distribution of the detection range according to the raindrop mass weighted average diameter and the liquid water content.
8. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the dual band radar raindrop spectrum inversion method of any one of claims 1 to 6.
9. A non-transitory computer readable storage medium having stored thereon a computer program, which when executed by a processor, implements the steps of the dual band radar raindrop spectrum inversion method of any of claims 1 to 6.
10. A computer program product comprising a computer program which, when executed by a processor, implements the steps of the dual band radar raindrop spectrum inversion method of any one of claims 1 to 6.
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