CN109521406B - Differential reflectivity ZDR calibration method and device - Google Patents
Differential reflectivity ZDR calibration method and device Download PDFInfo
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Abstract
The embodiment of the application discloses a differential reflectivity ZDR calibration method, which comprises the steps of firstly obtaining complex I/Q signals of a horizontal channel and a vertical channel corresponding to each distance library in each radial direction; then, correspondingly calculating ZDR related data corresponding to each distance library according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance library and the radial noise of the horizontal channel; then, screening target distance libraries from all distance libraries according to the bragg scattering characteristics and the ZDR related data corresponding to each distance library to form a target distance library set; and further judging whether the target distance library set meets the ZDR deviation evaluation standard, and if so, determining the ZDR deviation for calibrating the ZDR according to the ZDR related data corresponding to each target distance library in the target distance library set. When the method is adopted to calibrate the ZDR, the normal service executed by the radar does not need to be stopped, and the real-time update of the ZDR deviation can be realized.
Description
Technical Field
The application relates to the technical field of communication, in particular to a differential reflectivity ZDR calibration method and device.
Background
The dual polarization radar is a radar capable of transmitting and receiving both horizontally polarized waves and vertically polarized waves, and is widely applied to the field of meteorological detection; the differential reflectivity ZDR is used as an important observed quantity of the dual-polarization radar, plays an important role in the meteorological prediction process, and can be used for accurately calibrating the ZDR to directly influence the accuracy of the meteorological prediction.
However, since the horizontal channel and the vertical channel of the dual-polarization radar are generally not guaranteed to be completely consistent, and devices, installation, and the like in the two channels are different to some extent, there is a systematic deviation in the ZDR determined from the measured data, and the ZDR needs to be corrected. In addition, the ZDR offset may also change due to system operation, device aging, and maintenance updates, and therefore, the ZDR offset needs to be monitored to perform ZDR calibration based on the monitored ZDR offset.
In the current dual-polarization weather radar service system, a zenith calibration method is usually adopted to calibrate the ZDR; the zenith calibration method requires that a radar antenna vertically points to the sky, namely the radar antenna is required to reach an elevation angle of 90 degrees, 360-degree Plane Position Indicator (PPI) scanning is carried out, data are collected under the condition of laminar cloud with small rain intensity, then the data meeting the requirements are selected to determine the ZDR deviation, and the ZDR is calibrated according to the ZDR deviation.
When the zenith calibration method is adopted to calibrate the ZDR, the radar antenna is required to reach an elevation angle of 90 degrees, and the elevation angle of the radar antenna can only reach 19.5 degrees at most when the current normal service runs; that is, when the zenith calibration method is used for calibrating ZDR, the radar is required to stop the normal service operation and perform calibration under special configuration. In addition, because the ZDR can be calibrated only when the radar stops normal service, it is difficult to update the ZDR deviation in time by using the zenith calibration method, and accordingly, the ZDR is calibrated according to the inaccurate ZDR deviation.
Disclosure of Invention
In order to solve the technical problem, the application provides a ZDR calibration method which is not limited by a scanning mode and does not need to stop normal service of a radar in the process of calibrating the ZDR.
The embodiment of the application discloses the following technical scheme:
in a first aspect, an embodiment of the present application provides a differential reflectivity ZDR calibration method, where the method includes:
acquiring complex I/Q signals of a horizontal channel and a vertical channel corresponding to each radial distance library;
correspondingly calculating ZDR related data corresponding to each distance library according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance library and the radial noise of the horizontal channel;
screening target distance libraries according to the bragg scattering characteristics and the ZDR related data corresponding to each distance library to form a target database set;
judging whether the target distance library set meets the ZDR deviation evaluation standard or not;
and if so, determining a ZDR deviation according to the ZDR related data corresponding to the target distance library set, wherein the ZDR deviation is used for calibrating the actually measured ZDR.
In a second aspect, an embodiment of the present application provides a differential reflectivity ZDR calibration apparatus, including:
the acquisition module is used for acquiring complex I/Q signals of a horizontal channel and a vertical channel corresponding to each radial distance library;
the calculation module is used for correspondingly calculating ZDR related data corresponding to each distance bank according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance bank and the radial noise of the horizontal channel;
the screening module is used for screening out a target distance library according to the bragg scattering characteristics and the ZDR related data corresponding to each distance library to form a target database set;
the judging module is used for judging whether the target distance library set meets the ZDR deviation evaluation standard or not;
and the deviation determining module is used for determining the ZDR deviation according to the ZDR related data corresponding to the target distance library set if the target distance library set is consistent with the ZDR deviation, and the ZDR deviation is used for calibrating the actually measured ZDR.
According to the technical scheme, in the ZDR calibration method provided by the application, complex I/Q signals of a horizontal channel and a vertical channel corresponding to each distance library in each radial direction are obtained firstly; then, correspondingly calculating ZDR related data corresponding to each distance library according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance library and the radial noise of the horizontal channel; then, screening target distance libraries from all distance libraries according to the bragg scattering characteristics and the ZDR related data corresponding to each distance library to form a target distance library set; and further judging whether the target distance library set meets the ZDR deviation evaluation standard, and if so, determining the ZDR deviation for calibrating the ZDR according to the ZDR related data corresponding to each target distance library in the target distance library set.
The ZDR calibration method determines a target distance library set capable of being used for calculating the ZDR deviation based on a bragg scattering characteristic, wherein the bragg scattering characteristic refers to that the ZDR mean value of the area is 0 under a clear air condition due to the random orientation of turbulent eddies at the top of a convection boundary layer; compared with a zenith calibration method in the prior art, the ZDR calibration method provided by the application has no special limitation on the scanning mode of the radar when determining the ZDR deviation, and can calibrate the ZDR while the radar performs normal service, namely, when the ZDR calibration method provided by the application is used for calibrating the ZDR, the normal service executed by the radar does not need to be stopped, and the ZDR can be calibrated in real time in the process of performing normal service by the radar.
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In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic flowchart of a differential reflectivity ZDR calibration method provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of a differential reflectivity ZDR calibration apparatus provided in an embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terms "first," "second," "third," "fourth," and the like in the description and in the claims of the present application and in the drawings described above, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In the prior art, the ZDR is usually calibrated by using a zenith calibration method. Because the zenith calibration method requires that the elevation angle of the radar antenna reaches 90 degrees, and the elevation angle of the radar antenna can only reach 19.5 degrees at most when normal services are operated, when the zenith calibration method is adopted to calibrate the ZDR, the normal services executed by the radar need to be stopped, and the ZDR is calibrated under special configuration; in addition, since the ZDR cannot be calibrated while the radar performs normal traffic, it is difficult to ensure that the ZDR deviation is updated in time, and accordingly, there may be a case where the ZDR cannot be accurately calibrated due to inaccuracy of the adopted ZDR deviation.
In view of the technical problems in the prior art, embodiments of the present application provide a ZDR calibration method, which can calibrate ZDR without affecting normal service executed by a radar, and can ensure that a ZDR deviation is updated in time.
The core technical idea of the ZDR calibration method provided by the embodiment of the present application is introduced as follows:
in the ZDR calibration method provided by the application, a radar scans based on a preset volume scanning mode and correspondingly receives complex I/Q signals of a horizontal channel and a vertical channel corresponding to each distance bin in each radial direction; then, correspondingly calculating ZDR related data corresponding to each distance library according to the received complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance library and the radial noise of the horizontal channel; then, judging whether the ZDR related data corresponding to each distance library meets the bragg scattering characteristics or not, and taking the distance library corresponding to the ZDR related data meeting the bragg scattering characteristics as a target distance library, thereby screening the target distance library from all the distance libraries to form a target distance library set; and further judging whether the target distance set meets the ZDR deviation evaluation standard, and if so, determining the ZDR deviation of the radar system according to the ZDR related data corresponding to the target distance library set.
The ZDR calibration method screens target distance libraries which can be used for determining the ZDR deviation from all the distance libraries based on the bragg scattering characteristics, and then determines the ZDR deviation of the radar system based on the ZDR related data corresponding to the target distance libraries; the bragg scattering characteristic specifically means that the average ZDR of a turbulent vortex region at the top of a convection boundary layer is 0 under clear sky conditions due to the random orientation of the turbulent vortex region. Compared with the existing zenith calibration method, the ZDR calibration method provided by the embodiment of the application has no special limitation on the scanning mode of the radar when determining the ZDR deviation, namely, has no special limitation on the elevation angle of the radar antenna, so that the radar can calibrate the ZDR while performing normal service, and further, the ZDR can be calibrated while performing normal service, and the timeliness of updating the ZDR deviation can be ensured.
The ZDR calibration method provided by the present application is specifically described below by way of an embodiment.
Referring to fig. 1, fig. 1 is a schematic flow chart of a ZDR calibration method provided in an embodiment of the present application.
As shown in fig. 1, the method includes:
step 101: and acquiring complex I/Q signals of a horizontal channel and a vertical channel corresponding to each radial distance library.
When the radar performs normal services, scanning is generally required to be performed based on a preset volume scan mode, and the common volume scan mode mainly includes three types: VCP11, VCP21, and VCP 31; wherein, the VCP11 volume sweep mode refers to the completion of 14 elevation PPI scanning at 5 minutes, the VCP21 volume sweep mode refers to the completion of 9 elevation PPI scanning at 6 minutes, and the VCP31 volume sweep mode refers to the completion of 5 elevation PPI scanning at 10 minutes. When the radar executes normal service, the radar can complete scanning by adopting any one of the body scanning modes.
The PPI scanning is a scanning mode in which 360-degree omni-directional scanning is performed at a certain elevation angle of a radar antenna with a radar station as a center, and a plan view of the azimuth and the distance of a target object is displayed in a polar coordinate manner.
It should be understood that, in practical applications, the radar may perform scanning based on the three body scan modes, and may perform scanning based on other body scan modes according to practical requirements, where no limitation is imposed on the body scan mode adopted by the radar.
Under a preset body scanning mode, the radar completes multiple 360-degree scanning at different elevation angles; correspondingly, when the radar receives the echo signals, the radar receives complex I/Q signals of a horizontal channel and complex I/Q signals of a vertical channel corresponding to each radial distance bank in different elevation angles.
Radial specifically refers to a linear direction along a diameter or radius, which may also be understood as a linear direction perpendicular to the axis; the range bin refers to a small range unit divided by distance along the radial direction in the radar echo signal processing process.
Step 102: and correspondingly calculating ZDR related data corresponding to each distance bank according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance bank and the radial noise of the horizontal channel.
After the horizontal channel complex I/Q signals and the vertical channel complex I/Q signals corresponding to each distance bin in each radial direction are obtained, part of ZDR related data corresponding to each distance bin can be correspondingly calculated according to the horizontal channel complex I/Q signals and the vertical channel complex I/Q signals corresponding to each distance bin, and further, another part of ZDR related data corresponding to each distance bin can be correspondingly calculated according to the calculated part of ZDR related data and horizontal channel radial noise.
It should be noted that the ZDR-related data may specifically include: horizontal channel reflectivity ZhHorizontal channel radial velocity VhHorizontal channel velocity spectrum width WhSNR of horizontal channel and rho of zero lag cross correlation coefficienthv0And a differential reflectivity Zdr。
Specifically, when calculating the ZDR related parameters corresponding to each distance bin, the ZDR related parameters corresponding to each distance bin may be calculated one by one according to the following manner:
taking the calculation of the ZDR-related parameters corresponding to the distance bin k as an example, the method can be usedFirstly according to the complex I/Q signal x of the horizontal channel corresponding to the distance library khAnd the complex I/Q signal x of the vertical channelvCorrespondingly, the horizontal channel echo power P corresponding to the distance library k is calculatedh(k) And the vertical channel echo power Pv(k)。
Calculating the echo power P of horizontal channelh(k) And the vertical channel echo power Pv(k) Are respectively shown in formula (1) and formula (2):
wherein x ish(k, I) is the complex I/Q signal of the horizontal channel collected by the ith sampling corresponding to the distance library k, xvAnd (k, I) is a complex I/Q signal of a vertical channel acquired by the ith sampling corresponding to the distance library k, and N is the pulse sampling frequency.
Then, the echo power P of the horizontal channel corresponding to the distance library k obtained by the calculation is usedh(k) Calculating the horizontal channel reflectivity Z corresponding to the distance library kh(k) (ii) a Using the vertical channel echo power P corresponding to the distance library k obtained by the calculationv(k) Calculating the vertical channel reflectivity Z corresponding to the distance library kv(k)。
Calculating the horizontal channel reflectivity Zh(k) And vertical channel reflectivity Zv(k) Are respectively shown in formula (3) and formula (4):
Zh(k)＝10log(Ph(k))+C (3)
Zv(k)＝10log(Pv(k))+C (4)
wherein, Ph(k) For the horizontal channel echo power, P, corresponding to the range bin kv(k) The vertical channel echo power corresponding to the distance library k.
Wherein, C is 20log (reo · k) + Ax (reo · k) + syscal, the first term in C is distance attenuation correction, the second term is atmospheric attenuation correction, and the third term is system deviation correction; here, reso is the resolution corresponding to the distance bin k, a is the atmospheric attenuation correction constant, and syscal is the radar constant.
Further, the horizontal channel echo power P corresponding to the distance bin k obtained by the above calculation is usedh(k) And the vertical channel echo power Pv(k) Calculating the differential reflectivity Z corresponding to the distance library kdr(k)。
Calculating the differential reflectivity Zdr(k) Is shown in equation (5):
it will be appreciated that this differential reflectivity Zdr(k) The ZDR is calculated based on the actually acquired parameters, and may be biased and not corrected.
Further, according to the complex I/Q signal x of the horizontal channel corresponding to the distance library khAnd the complex I/Q signal x of the vertical channelvCorrespondingly calculating the zero-order autocorrelation R of the horizontal channel corresponding to the distance library khh0(k) Horizontal channel first order autocorrelation Rhh1(k) And zero order cross correlation R for horizontal and vertical channelsvh0(k)。
Specifically calculating the zero-order autocorrelation R of the horizontal channelhh0(k) Horizontal channel first order autocorrelation Rhh1(k) And zero order cross correlation R for horizontal and vertical channelsvh0(k) Are shown in equations (6), (7) and (8), respectively:
wherein x ish(k, I) is the complex I/Q signal of the horizontal channel collected from the ith sampling corresponding to the distance bank k,
is xh(k, i) conjugation; x is the number ofh(k, I-1) is the complex I/Q signal of the horizontal channel collected by the I-1 th sampling corresponding to the distance library k,
is xhConjugation of (k, i-1); x is the number ofv(k, I) is a complex I/Q signal of the vertical channel acquired by the ith sampling corresponding to the distance library k; and N is the number of pulse samples.
Further, the zero-order cross correlation R of the horizontal channel and the vertical channel corresponding to the distance library k obtained by the above calculation is usedvh0(k) Horizontal channel echo power Ph(k) And the vertical channel echo power Pv(k) Calculating the zero lag cross correlation coefficient rho corresponding to the distance library khv0(k)。
Specifically calculating the zero lag cross-correlation coefficient rhohv0(k) Is shown in equation (9):
further, the zero-order autocorrelation R of the horizontal channel corresponding to the distance bin k obtained by the above calculation is usedhh0(k) And horizontal channel first order autocorrelation Rhh1(k) Calculating the horizontal channel radial velocity V corresponding to the distance library kh(k) And velocity spectrum width Wh(k)。
Calculating the radial speed V of horizontal channelh(k) And velocity spectrum width Wh(k) Are respectively shown in formula (10) and formula (11):
wherein the content of the first and second substances,
λ is radar wavelength, TSIs a pulse repetition period.
Further, the horizontal channel reflectivity Z corresponding to the distance bin k obtained by the above calculation is usedh(k) And horizontal channel radial noise NhCalculating the signal-to-noise ratio SNR (k) of a horizontal channel corresponding to the distance library k; wherein the horizontal channel radial noise NhMay be determined from the continuous noise received by the horizontal channel.
The formula for specifically calculating the horizontal channel signal-to-noise ratio snr (k) is shown in formula (12):
SNR(k)＝Zh(k)-Nh (12)
in this way, each ZDR-related data is calculated one by one in the above calculation manner.
Step 103: and screening out the target distance libraries according to the bragg scattering characteristics and the ZDR related data corresponding to each distance library to form a target database set.
After calculating the ZDR related data corresponding to each distance library, correspondingly judging whether the distance library meets the bragg scattering characteristics one by one according to the ZDR related data corresponding to each distance library, namely judging whether the distance library is in a turbulent vortex area at the top of a convection boundary layer, further screening the distance libraries meeting the bragg scattering characteristics from all the distance libraries to serve as target distance libraries, and forming a target distance library set by using the screened target distance libraries.
When the target distance library is specifically screened, the screening can be performed in the following manner:
firstly, screening out first distance libraries from all distance libraries according to the distance between each distance library and a radar and the elevation angle corresponding to each distance library to form a first distance library set; the distance between the first distance library and the radar is within a preset distance range, and the elevation angle corresponding to the first distance library is within a preset angle range.
It should be understood that the radar generally needs to scan according to a preset volume sweep mode when performing normal services, a volume sweep mode generally includes a plurality of elevation angles, accordingly, during the process of receiving echo signals, the received echo signals correspond to the elevation angles of the corresponding transmitted signals, and since the receiving unit of echo signals is a range bank, each range bank also corresponds to an elevation angle accordingly.
And selecting the distance library with the distance between the distance library and the radar within a preset distance range and the corresponding elevation angle within a preset angle range from all the distance libraries as a first distance library, and forming a first distance library set by using all the first distance libraries screened in the way, thereby reducing the influence of ground objects. That is, by means of the above-mentioned screening, the distance bank partially affected by the ground object is filtered out, and the region where the distance bank is located obviously does not belong to the turbulent vortex region at the top of the convection boundary layer.
It should be noted that the preset distance range may be specifically 10 to 80km, and the preset angle range may be specifically 2.5 ° to 4.5 °, and of course, the preset distance range and the preset angle range may also be adaptively modified according to actual requirements, and the preset distance range and the preset angle range are not specifically limited herein.
Then, according to the horizontal channel reflectivity Z corresponding to each first distance libraryhAnd the horizontal channel signal-to-noise ratio SNR, screening out a second distance library from the first distance library set to form a second distance library set; the horizontal channel reflectivity Z corresponding to the second distance libraryhAnd the SNR of the horizontal channel corresponding to the second distance library is smaller than a second preset threshold.
Judging the horizontal channel reflectivity Z corresponding to each first distance library one by onehWhether the signal to noise ratio (SNR) of the horizontal channel corresponding to each first distance library is smaller than a second preset threshold value or not, and if the SNR of the horizontal channel corresponding to each first distance library is smaller than the second preset threshold value, determining the reflectivity Z of the horizontal channel corresponding to the first distance libraryhIs less than a first preset threshold value, and the SNR of the corresponding horizontal channel is less than a second preset threshold valueSetting a threshold value, which indicates that the echo signal received on the first distance library is a weak echo signal, and correspondingly, taking the first distance library as a second distance library; therefore, each first distance library in the first distance library set is judged one by one, so that each second distance library meeting the two conditions is screened out from the first distance library set to form a second distance library set.
It should be noted that the first preset threshold may be 10dBZ, and the second preset threshold may be 15dB, that is, the horizontal channel reflectivity Z corresponding to the second distance libraryhLess than 10dBZ, and the signal-to-noise ratio SNR of the horizontal channel corresponding to the second distance library is less than 15 dB; of course, the first preset threshold and the second preset threshold may also be adaptively modified according to actual requirements, and the first preset threshold and the second preset threshold are not specifically limited herein.
Furthermore, according to the zero lag cross correlation coefficient rho corresponding to each second distance bankhv0Screening a third distance library from the second distance library set to form a third distance library set; zero lag cross correlation coefficient rho corresponding to the third distance libraryhv0Greater than a third preset threshold.
Judging zero lag cross correlation coefficient rho corresponding to the second distance library one by onehv0Whether the value is larger than a third preset threshold value or not, if the value is larger than the third preset threshold value, the zero lag cross-correlation coefficient rho corresponding to the second distance libraryhv0If the second distance library is larger than the third preset threshold, the echo particles received at the second distance library are uniform in shape, and the second distance library is used as a third distance library; thereby, from the second distance library, the zero lag cross-correlation coefficient ρ is selectedhv0And forming a third distance library set by the third distance library which is larger than a third preset threshold.
It should be noted that the third preset threshold may be specifically 0.98, that is, the zero lag cross-correlation coefficient ρ corresponding to the third distance binhv0Is more than 0.98; of course, the third preset threshold may also be adaptively modified according to actual requirements, and the third preset threshold is not specifically limited herein.
Finally, according to the horizontal channel corresponding to each third distance libraryRadial velocity VhAnd horizontal channel velocity spectrum width WhScreening a target distance library from the third distance library set to form a target distance library set; horizontal channel radial velocity V corresponding to target distance libraryhIs greater than a fourth preset threshold, and the corresponding horizontal channel velocity spectrum width WhGreater than a fifth preset threshold.
Judging the radial speed V of the horizontal channel corresponding to each third distance library one by onehWhether the absolute value of the first distance library is larger than a fourth preset threshold value or not, and judging the horizontal channel velocity spectrum width W corresponding to the third distance libraryhIf the radial speed is greater than the fifth preset threshold, if the radial speed is greater than the second preset threshold, the horizontal channel corresponding to the second distance bank has a radial speed VhIs greater than a fourth preset threshold, and the corresponding horizontal channel velocity spectrum width WhIf the distance is greater than the fifth preset threshold, the corresponding speed spectrum width of the third distance library is wider, and the radial speed of the third distance library is not close to zero, and the third distance library is used as a target distance library, so that the influence of weather signals with narrow spectrum width and radial speed close to zero on the determination of the ZDR deviation is reduced. Therefore, all the third distance libraries which simultaneously meet the two conditions are screened out from the third distance library set to serve as target distance libraries, and then all the target distance libraries are combined into a target distance library set.
It should be noted that the fourth preset threshold may be specifically 2m/s, and the fifth preset threshold may be specifically 0.5m/s, that is, the absolute value | V of the horizontal channel radial velocity corresponding to the target distance libraryhIf is greater than 2m/s, the horizontal channel velocity spectrum width W corresponding to the target distance libraryhMore than 0.5 m/s; of course, the fourth preset threshold and the fifth preset threshold may also be adaptively modified according to actual requirements, and the fourth preset threshold and the fifth preset threshold are not specifically limited herein.
It should be understood that the above-mentioned screening sequence is only an example, and in practical application, the above-mentioned screening sequence may be arbitrarily changed according to actual requirements, that is, the screening may be performed according to the distance between the distance library and the radar and the elevation angle corresponding to the distance library, or according to the horizontal channel reflectivity Z corresponding to the distance libraryhAnd horizontal channel informationThe noise ratio SNR is screened, or the zero lag cross correlation coefficient rho corresponding to the distance library is firstly screenedhv0Screening can be carried out according to the radial speed V of the horizontal channel corresponding to the distance libraryhAnd horizontal channel velocity spectrum width WhScreening is performed without any restriction on the specific screening order.
Step 104: and judging whether the target distance library set meets the ZDR deviation evaluation standard.
And after the target distance library set is screened out, further judging whether the target distance library set meets the ZDR deviation evaluation standard, namely judging whether the screened target distance library set can be used for determining the ZDR deviation, and determining the ZDR deviation according to the ZDR related data corresponding to the screened target distance library set only under the condition that the screened target distance library set can be used for determining the ZDR deviation.
In specific implementation, the horizontal channel reflectivity Z corresponding to each target distance library in the target distance library set can be judged firstlyhWhether the proportion smaller than or equal to the sixth preset threshold value reaches the preset proportion or not.
That is, the horizontal channel reflectivity Z corresponding to each target range binhAccording to the sequence from small to large, determining the horizontal channel reflectivity ZhThe number of target distance bins which are less than or equal to a sixth preset threshold value is calculated, and then the horizontal channel reflectivity Z is calculatedhAnd if the proportion of the target distance library which is smaller than or equal to the sixth preset threshold value in all the target distance libraries reaches the preset proportion, the precipitation echo is filtered in the process of screening the target distance libraries.
It should be noted that the sixth preset threshold may be specifically-3 dB, and the preset ratio may be specifically 90%; of course, the sixth preset threshold and the preset ratio may also be adaptively modified according to actual requirements, and the sixth preset threshold and the preset ratio are not specifically limited herein.
And then, judging whether the number of the target distance libraries in the target distance library set is greater than the preset distance library number.
That is, it is determined whether the number of all target distance bins in the target distance bin set exceeds the preset number of distance bins, and if so, it indicates that the target distance bin set screened in step 103 has statistical characteristics, and the ZDR deviation determined according to the ZDR related data corresponding to the target distance bin set has a certain reliability.
It should be noted that the number of the preset distance bins may be 10000 specifically, that is, the number of the target distance bins in the target distance bin set needs to be greater than 10000; of course, the number of the preset distance bins may also be adaptively modified according to actual requirements, and no limitation is made on the number of the preset distance bins.
And finally, judging whether the quartile distance of the differential reflectivity corresponding to all the target distance libraries in the target distance library set is smaller than a seventh preset threshold value.
Specifically, the differential reflectivity Z corresponding to all target distance binsdrArranging the Z's thus arranged in order from small to largedrThe sequence is quartered and differential reflectivity Z at three division points is obtaineddr(ii) a Z isdrZ at the first segmentation point in the sequencedrI.e. in the 25 th% of ZdrA first quartile Q1, also known as the smaller quartile; z isdrZ at the second split point in the sequencedrI.e. Z at 50%drIs a second quartile Q2, also known as the median; z isdrZ at the third segmentation point in the sequencedrI.e. at 75% of ZdrA third quartile Q3, also known as the larger quartile; the difference between the third Quartile Q3 and the first Quartile Q1 is the interquartile Range (IQR). And then, judging whether the quartile range IQR of the differential reflectivity ZDR obtained by calculation is smaller than a seventh preset threshold, if so, indicating that the target distance library screened in the step 103 is the distance library with the biological clutter filtered.
It should be noted that the seventh preset threshold may be specifically 0.9, that is, the quartile distance IQR of the differential reflectivity corresponding to all the target distance bins is less than 0.9; of course, the seventh preset threshold may also be adaptively modified according to actual requirements, and the seventh preset threshold is not limited herein.
It should be understood that the above-mentioned determination sequence is only an example, and in practical applications, the above-mentioned determination sequence may be modified arbitrarily, that is, the horizontal channel reflectivity Z corresponding to each target range bin in the target range bin set may be determined firsthWhether the ratio smaller than or equal to the sixth preset threshold reaches the preset ratio or not can be judged, whether the number of the target distance bins in the target distance bin set reaches the preset distance bin number or not can be judged first, whether the quartile distance of the differential reflectivity corresponding to all the target distance bins in the target distance bin set is smaller than the seventh preset threshold or not can be judged first, and no limitation is made on the judgment sequence.
And if the target distance library set is determined to meet the three judgment conditions, the target distance library set is determined to meet the ZDR deviation evaluation standard. I.e. if the horizontal channel reflectivity Z corresponding to each range bin in the target range bin sethWhether the proportion smaller than or equal to the sixth preset threshold value reaches the preset proportion or not, the number of the target distance bins in the target distance bin set reaches the preset distance bin number, and the quartile distance of the differential reflectivity corresponding to all the target distance bins in the target distance bin set is smaller than the seventh preset threshold value, so that the target distance bin set can be determined to accord with the ZDR deviation evaluation standard; conversely, if the target distance library does not satisfy any one or more of the above conditions, it may be determined that the target distance library does not comply with the ZDR deviation evaluation criteria.
Step 105: and if so, determining a ZDR deviation according to the ZDR related data corresponding to the target distance library set, wherein the ZDR deviation is used for calibrating the actually measured ZDR.
If the target distance library set is determined to meet the ZDR deviation evaluation standard, the ZDR deviation of the system is further determined according to ZDR related data corresponding to all target distance libraries in the target distance library, and the actual measured ZDR is corrected according to the ZDR deviation thus determined, through step 104.
It should be noted that, through step 103 and step 104, if it is determined that ZDR-related data corresponding to the target distance library set conforms to the ZDR deviation evaluation standard, it is determined that the target distance libraries in the target distance library set are substantially all located in the turbulent vortex region at the top of the convection boundary layer; since the turbulent vortex region at the top of the convection boundary layer has random orientation, the ZDR mean value corresponding to this region is 0, and if the ZDR determined based on the ZDR-related data corresponding to each of the target distance bins is not 0, this ZDR value can be used as the ZDR deviation of the system accordingly.
During specific implementation, according to the difference reflectivity Z corresponding to each target distance library in the target distance library setdrDrawing a probability density distribution curve; further, the differential reflectance Z corresponding to each target range bin is determineddrAs the ZDR deviation.
That is, the difference reflectance Z corresponding to each target range bin is useddrPlotting the differential reflectivity ZdrAccording to the differential reflectivity ZdrDetermining the differential reflectivity ZdrThe mode ZDR _ mod of (a) is taken as the ZDR deviation on the system.
It should be understood that, in practical applications, the ZDR deviation may also be determined in other manners according to ZDR related data corresponding to each target distance library, and the manner of determining the ZDR deviation is not limited herein.
The method for calibrating the ZDR comprises the steps of determining a target distance library set capable of being used for calculating the ZDR deviation based on a bragg scattering characteristic, wherein the bragg scattering characteristic refers to that the average value of the ZDR of a region is 0 under a clear air condition due to the random orientation of turbulent eddies at the top of a convection boundary layer; compared with a zenith calibration method in the prior art, the ZDR calibration method provided by the application has no special limitation on the scanning mode of the radar when determining the ZDR deviation, and can calibrate the ZDR while the radar performs normal service, namely, when the ZDR calibration method provided by the application is used for calibrating the ZDR, the normal service executed by the radar does not need to be stopped, and the ZDR can be calibrated in real time in the process of performing normal service by the radar.
In view of the ZDR calibration method, an embodiment of the present application further provides a ZDR calibration apparatus, see fig. 2, and fig. 2 is a schematic structural diagram of a ZDR calibration apparatus 200 provided in the embodiment of the present application. As shown in FIG. 2, the ZDR calibration device 200 includes:
an obtaining module 201, configured to obtain complex I/Q signals of a horizontal channel and a vertical channel corresponding to each distance bin in each radial direction;
a calculating module 202, configured to correspondingly calculate ZDR related data corresponding to each distance bin according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance bin and the horizontal channel radial noise;
the screening module 203 is used for screening out the target distance databases according to the bragg scattering characteristics and the ZDR related data corresponding to each distance database to form a target database set;
a judging module 204, configured to judge whether the target distance library set meets a ZDR deviation evaluation standard;
and a deviation determining module 205, configured to determine a ZDR deviation according to ZDR-related data corresponding to the target distance library set if the ZDR deviation matches the target distance library set, where the ZDR deviation is used to calibrate the actually measured ZDR.
Optionally, the ZDR-related data includes: horizontal channel reflectivity ZhHorizontal channel radial velocity VhHorizontal channel velocity spectrum width WhSNR of horizontal channel and rho of zero lag cross correlation coefficienthv0And a differential reflectivity Zdr。
Optionally, the calculation module specifically includes:
a first calculation submodule for calculating the complex I/Q signal x of the horizontal channel corresponding to the distance library khAnd the complex I/Q signal x of the vertical channelvCalculating the echo power P of the horizontal channel corresponding to the distance library kh(k) And the vertical channel echo power Pv(k)；
A second calculation submodule for calculating the echo power P of the horizontal channel corresponding to the distance library kh(k) Calculating the horizontal channel reflectivity Z corresponding to the distance library kh(k) (ii) a According to the vertical channel echo power P corresponding to the distance library kv(k) Calculating the vertical channel reflectivity Z corresponding to the distance library kv(k)；
A third computing submodule for computing the echo power P of the horizontal channel corresponding to the distance library kh(k) And the vertical channel echo power Pv(k) Calculating the differential reflectivity Z corresponding to the distance library kdr(k)；
A fourth calculation submodule for calculating the complex I/Q signal x of the horizontal channel corresponding to the distance library khAnd the complex I/Q signal x of the vertical channelvCorrespondingly calculating the zero-order autocorrelation R of the horizontal channel corresponding to the distance library khh0(k) Horizontal channel first order autocorrelation Rhh1(k) And zero order cross correlation R for horizontal and vertical channelsvh0(k)；
A fifth calculation submodule for calculating the zero-order cross correlation R of the horizontal channel and the vertical channel corresponding to the distance library kvh0(k) Horizontal channel echo power Ph(k) And the vertical channel echo power Pv(k) Calculating the zero lag cross correlation coefficient rho corresponding to the distance library khv0(k)；
A sixth calculation submodule for calculating the zero-order autocorrelation R of the horizontal channel corresponding to the distance bin khh0(k) And horizontal channel first order autocorrelation Rhh1(k) Correspondingly calculating the horizontal channel radial velocity V corresponding to the distance library kh(k) And velocity spectrum width Wh(k)；
A seventh calculation submodule for calculating the horizontal channel reflectivity Z corresponding to the distance library kh(k) And the horizontal channel radial noise NhAnd calculating the signal-to-noise ratio SNR (k) of the horizontal channel corresponding to the distance library k.
Optionally, the horizontal channel echo power P corresponding to the distance library kh(k) And the vertical channel echo power Pv(k) Respectively calculated according to formula (1) and formula (2):
wherein x ish(k, I) is the complex I/Q signal of the horizontal channel collected by the ith sampling, xv(k, I) is a complex I/Q signal of the vertical channel acquired by the ith sampling, and N is the pulse sampling frequency;
the horizontal channel reflectivity Z corresponding to the distance library kh(k) And vertical channel reflectivity Zv(k) Calculated according to formula (3) and formula (4), respectively:
Zh(k)＝10log(Ph(k))+C (3)
Zv(k)＝10log(Pv(k))+C (4)
wherein C is 20log (reo · k) + a × (reo · k) + syscal, where reo is the resolution of the range bin k, a is the atmospheric attenuation correction constant, and syscal is the radar constant.
The differential reflectivity Z corresponding to the distance library kdr(k) Is calculated according to the formula (5):
the zero-order autocorrelation R of the horizontal channel corresponding to the distance library khh0(k) Horizontal channel first order autocorrelation Rhh1(k) And zero order cross correlation R for horizontal and vertical channelsvh0(k) Calculated according to equations (6), (7) and (8), respectively:
said distanceZero lag cross correlation coefficient rho corresponding to k away from the binhv0(k) Is calculated according to the formula (9):
the radial velocity V of the horizontal channel corresponding to the distance library kh(k) And velocity spectrum width Wh(k) Calculated according to equation (10) and equation (11), respectively:
wherein the content of the first and second substances,
λ is radar wavelength, TSIs a pulse repetition period.
The horizontal channel signal-to-noise ratio SNR (k) corresponding to the distance library k is calculated according to the formula (12):
SNR(k)＝Zh(k)-Nh (12)
wherein N ishHorizontal channel radial noise.
Optionally, the screening module is specifically configured to:
screening out first distance libraries from all the distance libraries according to the distance between each distance library and the radar and the elevation angle corresponding to each distance library to form a first distance library set; the distance between the first distance library and the radar is within a preset distance range, and the elevation angle corresponding to the first distance library is within a preset angle range;
according to the horizontal channel reflectivity Z corresponding to each first distance libraryhAnd a horizontal channel signal-to-noise ratio (SNR), screening a second distance library from the first distance library set to form a second distance library set; the second distance libraryCorresponding horizontal channel reflectivity ZhThe SNR of the horizontal channel corresponding to the second distance library is smaller than a second preset threshold;
according to the zero lag cross correlation coefficient rho corresponding to each second distance libraryhv0Screening a third distance library from the second distance library set to form a third distance library set; zero lag cross-correlation coefficient rho corresponding to the third range binhv0Greater than a third preset threshold;
according to the horizontal channel radial velocity V corresponding to each third distance libraryhAnd horizontal channel velocity spectrum width WhScreening the target distance library from the third distance library to form a target distance library set; the horizontal channel radial velocity V corresponding to the target distance libraryhIs greater than a fourth preset threshold, and the horizontal channel velocity spectrum width W corresponding to the target distance libraryhGreater than a fifth preset threshold.
Optionally, the preset distance range is 10 to 80 km; the preset angle range is 2.5 degrees to 4.5 degrees;
the first preset threshold is 10 dBZ; the second preset threshold is 15 dB;
the third preset threshold is 0.98;
the fourth preset threshold is 2m/s, and the fifth preset threshold is 0.5 m/s.
Optionally, the determining module is specifically configured to:
judging the horizontal channel reflectivity Z corresponding to each target distance library in the target distance library sethWhether the proportion smaller than or equal to a sixth preset threshold value reaches a preset proportion or not;
judging whether the number of the target distance libraries in the target distance library set reaches the preset distance library number or not;
judging whether the quartile distance of the differential reflectivity corresponding to all the target distance bins in the target distance bin set is smaller than a seventh preset threshold value or not;
and if the target distance library set meets the ZDR deviation evaluation standard, determining that the target distance library set meets the ZDR deviation evaluation standard.
Optionally, the sixth preset threshold is-3 dB, and the preset ratio is 90%;
the number of the preset distance libraries is 10000;
the seventh preset threshold is 0.9.
Optionally, the deviation determining module is specifically configured to:
according to the differential reflectivity Z corresponding to each target distance library in the target distance library setdrDrawing a probability density distribution curve; the differential reflectivity Z corresponding to each target distance librarydrAs the ZDR deviation.
The ZDR calibration device provided by the embodiment of the application determines a target distance library set capable of being used for calculating the ZDR deviation based on a bragg scattering characteristic, wherein the bragg scattering characteristic refers to that the average ZDR value of a region is 0 under a clear air condition due to the random orientation of turbulent eddies at the top of a convection boundary layer; compared with a zenith calibration method in the prior art, the ZDR calibration device provided by the application has no special limitation on the scanning mode of the radar when determining the ZDR deviation, and can calibrate the ZDR while the radar performs normal service, namely, when the ZDR calibration device provided by the application is used for calibrating the ZDR, the normal service executed by the radar does not need to be stopped, and the ZDR can be calibrated in real time in the process of performing normal service by the radar.
It should be noted that, in the present specification, all the embodiments are described in a progressive manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the apparatus and system embodiments, since they are substantially similar to the method embodiments, they are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only one specific embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (9)
1. A differential reflectivity ZDR calibration method, the method comprising:
acquiring complex I/Q signals of a horizontal channel and a vertical channel corresponding to each radial distance library;
correspondingly calculating ZDR related data corresponding to each distance library according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance library and the radial noise of the horizontal channel; the ZDR-related data comprises: horizontal channel reflectivity ZhAnd differential reflectivity Zdr；
Screening target distance libraries according to the bragg scattering characteristics and the ZDR related data corresponding to each distance library to form a target database set;
judging whether the target distance library set meets the ZDR deviation evaluation standard or not;
if so, determining a ZDR deviation according to ZDR related data corresponding to the target distance library set, wherein the ZDR deviation is used for calibrating the actually measured ZDR;
the judging whether the target distance library set meets the ZDR deviation evaluation standard includes:
judging the horizontal channel reflectivity Z corresponding to each target distance library in the target distance library sethWhether the proportion smaller than or equal to a sixth preset threshold value reaches a preset proportion or not;
judging whether the number of the target distance libraries in the target distance library set reaches the preset distance library number or not;
judging whether the quartile distance of the differential reflectivity corresponding to all the target distance bins in the target distance bin set is smaller than a seventh preset threshold value or not;
and if the target distance library set meets the ZDR deviation evaluation standard, determining that the target distance library set meets the ZDR deviation evaluation standard.
2. The method of claim 1, wherein the ZDR-related data further comprises: horizontal path radial velocity VhHorizontal channel velocity spectrum width WhSNR of horizontal channel and rho of zero lag cross correlation coefficienthv0。
3. The method of claim 2, wherein calculating ZDR-related data for each range bin based on the complex I/Q signals for the horizontal and vertical channels and horizontal channel radial noise for each range bin accordingly comprises:
according to the complex I/Q signal x of the horizontal channel corresponding to the distance library khAnd the complex I/Q signal x of the vertical channelvCalculating the echo power P of the horizontal channel corresponding to the distance library kh(k) And the vertical channel echo power Pv(k)；
According to the horizontal channel echo power P corresponding to the distance library kh(k) Calculating the horizontal channel reflectivity Z corresponding to the distance library kh(k) (ii) a According to the vertical channel echo power P corresponding to the distance library kv(k) Calculating the vertical channel reflectivity Z corresponding to the distance library kv(k)；
According to the horizontal channel echo power P corresponding to the distance library kh(k) And the vertical channel echo power Pv(k) Calculating the differential reflectivity Z corresponding to the distance library kdr(k)；
According to the complex I/Q signal x of the horizontal channel corresponding to the distance library khAnd the complex I/Q signal x of the vertical channelvCorrespondingly calculating the zero-order autocorrelation R of the horizontal channel corresponding to the distance library khh0(k) Horizontal channel first order autocorrelation Rhh1(k) And zeroth order of horizontal and vertical channelsCross correlation Rvh0(k)；
According to the zero-order cross correlation R of the horizontal channel and the vertical channel corresponding to the distance library kvh0(k) Horizontal channel echo power Ph(k) And the vertical channel echo power Pv(k) Calculating the zero lag cross correlation coefficient rho corresponding to the distance library khv0(k)；
According to the zero-order autocorrelation R of the horizontal channel corresponding to the distance library khh0(k) And horizontal channel first order autocorrelation Rhh1(k) Correspondingly calculating the horizontal channel radial velocity V corresponding to the distance library kh(k) And velocity spectrum width Wh(k)；
According to the horizontal channel reflectivity Z corresponding to the distance library kh(k) And the horizontal channel radial noise NhAnd calculating the signal-to-noise ratio SNR (k) of the horizontal channel corresponding to the distance library k.
4. The method according to claim 3, wherein the distance bin k corresponds to a horizontal channel echo power Ph(k) And the vertical channel echo power Pv(k) Respectively calculated according to formula (1) and formula (2):
wherein x ish(k, I) is the complex I/Q signal of the horizontal channel collected by the ith sampling, xv(k, I) is a complex I/Q signal of the vertical channel acquired by the ith sampling, and N is the pulse sampling frequency;
the horizontal channel reflectivity Z corresponding to the distance library kh(k) And vertical channel reflectivity Zv(k) Calculated according to formula (3) and formula (4), respectively:
Zh(k)＝10log(Ph(k))+C (3)
Zv(k)＝10log(Pv(k))+C (4)
wherein, C is 20log (reo · k) + a × (reo · k) + syscal, where reo is the resolution of the distance bin k, a is the atmospheric attenuation correction constant, and syscal is the radar constant;
the differential reflectivity Z corresponding to the distance library kdr(k) Is calculated according to the formula (5):
the zero-order autocorrelation R of the horizontal channel corresponding to the distance library khh0(k) Horizontal channel first order autocorrelation Rhh1(k) And zero order cross correlation R for horizontal and vertical channelsvh0(k) Calculated according to equations (6), (7) and (8), respectively:
zero lag cross correlation coefficient rho corresponding to the distance library khv0(k) Is calculated according to the formula (9):
the radial velocity V of the horizontal channel corresponding to the distance library kh(k) And velocity spectrum width Wh(k) Calculated according to equation (10) and equation (11), respectively:
wherein the content of the first and second substances,
λ is radar wavelength, TsIs a pulse repetition period;
the horizontal channel signal-to-noise ratio SNR (k) corresponding to the distance library k is calculated according to the formula (12):
SNR(k)＝Zh(k)-Nh (12)
wherein N ishHorizontal channel radial noise.
5. The method of claim 2, wherein screening target distance bins from the bragg scattering features and ZDR-related data corresponding to each distance bin to form a target data bin set comprises:
screening out first distance libraries from all the distance libraries according to the distance between each distance library and the radar and the elevation angle corresponding to each distance library to form a first distance library set; the distance between the first distance library and the radar is within a preset distance range, and the elevation angle corresponding to the first distance library is within a preset angle range;
according to the horizontal channel reflectivity Z corresponding to each first distance libraryhAnd a horizontal channel signal-to-noise ratio (SNR), screening a second distance library from the first distance library set to form a second distance library set; the horizontal channel reflectivity Z corresponding to the second distance libraryhThe SNR of the horizontal channel corresponding to the second distance library is smaller than a second preset threshold;
according to the zero lag cross correlation coefficient rho corresponding to each second distance libraryhv0Screening a third distance library from the second distance library set to form a third distance library set; zero lag cross-correlation coefficient rho corresponding to the third range binhv0Greater than a third preset threshold;
according to the horizontal channel radial velocity V corresponding to each third distance libraryhAnd horizontal channel velocity spectrum width WhScreening the target distance library from the third distance library to form a target distance library set; the horizontal channel radial velocity V corresponding to the target distance libraryhIs greater than a fourth preset threshold, and the horizontal channel velocity spectrum width W corresponding to the target distance libraryhGreater than a fifth preset threshold.
6. The method according to claim 5, wherein the preset distance range is 10 to 80 km; the preset angle range is 2.5 degrees to 4.5 degrees;
the first preset threshold is 10 dBZ; the second preset threshold is 15 dB;
the third preset threshold is 0.98;
the fourth preset threshold is 2m/s, and the fifth preset threshold is 0.5 m/s.
7. The method according to claim 1, wherein the sixth predetermined threshold is-3 dB, and the predetermined ratio is 90%;
the number of the preset distance libraries is 10000;
the seventh preset threshold is 0.9.
8. The method of claim 2, wherein determining ZDR biases from ZDR-related data corresponding to the target range bin set comprises:
according to the differential reflectivity Z corresponding to each target distance library in the target distance library setdrDrawing a probability density distribution curve; the differential reflectivity Z corresponding to each target distance librarydrAs the ZDR deviation.
9. A differential reflectivity ZDR calibration apparatus, said apparatus comprising:
the acquisition module is used for acquiring complex I/Q signals of a horizontal channel and a vertical channel corresponding to each radial distance library;
the calculation module is used for correspondingly calculating ZDR related data corresponding to each distance bank according to the complex I/Q signals of the horizontal channel and the vertical channel corresponding to each distance bank and the radial noise of the horizontal channel; the ZDR-related data comprises: horizontal channel reflectivity ZhAnd differential reflectivity Zdr；
The screening module is used for screening out a target distance library according to the bragg scattering characteristics and the ZDR related data corresponding to each distance library to form a target database set;
the judging module is used for judging whether the target distance library set meets the ZDR deviation evaluation standard or not;
a deviation determining module, configured to determine a ZDR deviation according to ZDR-related data corresponding to the target distance library set if the ZDR deviation matches the target distance library set, where the ZDR deviation is used to calibrate an actually measured ZDR;
the judgment module is specifically configured to:
judging the horizontal channel reflectivity Z corresponding to each target distance library in the target distance library sethWhether the proportion smaller than or equal to a sixth preset threshold value reaches a preset proportion or not;
judging whether the number of the target distance libraries in the target distance library set reaches the preset distance library number or not;
judging whether the quartile distance of the differential reflectivity corresponding to all the target distance bins in the target distance bin set is smaller than a seventh preset threshold value or not;
and if the target distance library set meets the ZDR deviation evaluation standard, determining that the target distance library set meets the ZDR deviation evaluation standard.
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