CN113655454B - Terahertz cloud detection radar reflectivity factor calibration method based on millimeter wave radar - Google Patents
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- 239000012798 spherical particle Substances 0.000 claims abstract description 7
- 239000002245 particle Substances 0.000 claims description 24
- 238000005259 measurement Methods 0.000 claims description 21
- 238000002834 transmittance Methods 0.000 claims description 9
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- 238000004904 shortening Methods 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 15
- 238000010521 absorption reaction Methods 0.000 description 6
- 239000008276 ice cloud Substances 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/40—Means for monitoring or calibrating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/95—Radar or analogous systems specially adapted for specific applications for meteorological use
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Abstract
A terahertz cloud-detection radar reflectivity factor calibration method based on millimeter wave radar comprises the following steps: s1, correcting transmitting power and echo power by adopting internal calibration measured values; s2, calculating radar reflectivity factors under the conditions of spherical particles and Rayleigh scattering; s3, performing Mie scattering correction and attenuation correction on the radar reflectivity factor; and S4, evaluating the accuracy of the radar reflectivity factor. The invention has the advantages of small error of the calibration result, high reliability, shortening the calibration period and improving the calibration efficiency.
Description
Technical Field
The invention relates to the technical field of active measurement Yun Lei, in particular to a terahertz cloud radar reflectivity factor calibration method based on millimeter wave radar.
Background
The international electrounion determines 237.9-238 GHz as the working frequency band of the terahertz active cloud testing radar. Compared with a microwave radar, the terahertz active cloud measurement radar has the advantages of sensitivity to ice cloud targets, high cloud particle Doppler speed measurement precision and the like, and has the characteristics of strong penetrability, multi-layer cloud measurement and the like compared with laser measurement Yun Lei. The terahertz active cloud testing radar obtains the cloud particle radar reflectivity factor in the cloud by transmitting electromagnetic waves to the cloud and receiving echo data, and obtains Yun Hong microcosmic physical parameters by adopting a data inversion technology, so that the terahertz active cloud testing radar is applied to numerical weather forecast and climate mode research.
The measurement accuracy of the cloud particle radar reflectivity factor directly influences the accuracy of the data inversion Yun Hong microcosmic physical parameters, and the cloud particle radar reflectivity factor has important significance on numerical weather forecast. In order to meet the measurement precision of the radar reflectivity factor, an internal calibration method and an external calibration method are adopted, the terahertz measurement Yun Lei reaches the system parameters, and the measurement deviation is corrected. Besides the antenna subsystem, the internal calibration method can measure system parameters such as a radar receiver and a transmitter, and the internal calibration lacks the mutual influence among the system components, so that the system integrity is not fully considered; the external calibration is an end-to-end measurement mode, and the measurement result comprises the antenna parameters and the mutual influence among all components, so that the defect of the internal calibration is overcome. The external calibration mainly adopts a target or target simulator with known detection radar reflection sectional area (RCS), and compares the difference between a nominal value and an actual observed value, so as to correct the error of the radar system. The commonly known targets comprise targets such as a standard body and a sea surface, and the test is supported by test flight or by outdoor erection of a huge test tower, so that the method has huge engineering quantity and great cost of manpower and material resources.
Disclosure of Invention
The invention aims to provide a terahertz cloud-measuring radar reflectivity factor calibration method based on a millimeter wave radar, which has the advantages of small calibration result error, high reliability, shortened calibration period and improved calibration efficiency.
In order to achieve the above purpose, the invention provides a terahertz cloud testing radar reflectivity factor calibration method based on millimeter wave radar, which comprises the following steps:
s1, correcting transmitting power and echo power by adopting internal calibration measured values;
s2, calculating radar reflectivity factors under the conditions of spherical particles and Rayleigh scattering;
s3, performing Mie scattering correction and attenuation correction on the radar reflectivity factor;
and S4, evaluating the accuracy of the radar reflectivity factor.
In the step S1, the actual transmission power P t And the power value P obtained by detection t0 The relation of (2) is:
P t ＝P t0 L 1 (1)
wherein L is 1 The scale factor for the detector diode is related to the operating temperature;
received power P r Power P output from receiver r0 The relation of (2) is:
P r ＝P r0 L 2 /A r (2)
wherein L is 2 Is the loss between the antenna and the receiver input; a is that r For the receiver gain.
The step S2 includes the steps of:
the radar reflectivity calculation formula is:
wherein P is r For received power, the unit is W; p (P) t The unit is W for transmitting power; r is distance, and the unit is m; c is a radar constant, and the calculation formula is:
wherein lambda is wavelength and the unit is m; g t 、G r The gain of the transmitting antenna and the gain of the receiving antenna are respectively; ρ r The unit is m, which is the distance resolution; omega is a normalized two-way antenna pattern calculated as gaussian beams:
wherein θ andthe beam widths of the azimuth direction and the pitching direction are 3dB respectively, and the unit is rad;
under the conditions of spherical particles and Rayleigh scattering, the calculation formula of the radar reflectivity factor is as follows:
where k= (m-1)/(m+2), m represents the complex refractive index of water or ice particles, which is related to wavelength.
The step S3 includes the steps of:
s3.1, calculating an atmospheric attenuation coefficient k by adopting atmospheric temperature and humidity data and Liebe mode a According to the cloud attenuation coefficient k c =0, calculateThe double-pass transmittance tau (R) of the cloud drop at the distance R is obtained to obtain a radar reflectivity factor Z after correction of atmospheric attenuation m1 ：
Z m1 (R)＝Z m (R)/τ(R)
Where k is the atmospheric attenuation coefficient k a And a cloud attenuation coefficient k c And (3) summing;
s3.2, correcting cloud attenuation according to a library-by-library correction method, calculating double-pass transmittance tau (R) from a distance unit closest to the radar, wherein the double-pass transmittance tau from the distance unit closest to the radar to the i-1 th distance library is i-1 The actual value after attenuation correction of the radar reflectivity factor of the ith range bin is approximated by:
Z m2 (R)＝[Z m1 (R)/τ i-1 ]exp{α[Z m1 (R)/τ i-1 ] β ΔR}
wherein Δr is the distance resolution;
wherein alpha and beta are regression coefficients;
s3.3, inverting the probability distribution N (D) of the size of the cloud particles to obtain the Mie scattering correction parameter f Mie Calculate the correction value Z m3 ＝Z m2 f Mie Repeating the step S3.2, and obtaining a new Z by performing the attenuation correction on a library-by-library basis m2 ' then carrying out data inversion and Mie scattering correction to obtain a new correction value Z m3 ' until a value Z is defined m3 Rate of change of |Z' m3 -Z m3 |/Z m3 Less than a threshold value, obtaining a radar reflectivity factor Z of the range bin r (R)。
The step S4 includes the steps of:
calculating the millimeter wave radar reflectivity factor Z according to (1) to (6) r1 Average value of (2) and terahertz radar reflectivity factor Z r2 According to the average value of the (1), respectively calculating radar reflectivity factors of millimeter wave cloud radar and terahertz radar Yun Lei according to steps S1-S3 to obtain the distance between the millimeter wave radar reflectivity factorsDistribution Zr in the separation direction 1 (R) distribution Zr of terahertz cloud radar reflectivity factors in distance direction 2 (R) calculation of Zr in one sample 1 (R)-Zr 2 (R) averaging M samples to obtain the terahertz cloud-measuring radar measurement deviation delta Z and Zr 2 (R) adding to obtain a correction result;
calculating root mean square error by using the corrected terahertz cloud radar reflectivity factor to evaluate measurement accuracy, wherein the calculation formula is as follows:
wherein Z is r2,i (R) is the range-wise distribution of the terahertz cloud radar reflectivity factor of the ith sample,and the distance distribution of the mean value of the terahertz cloud radar reflectivity factors is obtained.
The invention has the following advantages:
1. and correcting the radar reflectivity factor deviation of the terahertz cloud-measuring radar by using the calibrated millimeter wave radar measurement data as a reference value. The internal calibration method is filled with the fact that only parameters of the subsystem are measured, influences between the antenna and the subsystem are not considered, and meanwhile compared with the external calibration method, a test tower or a hanging test is not needed to be erected, and cost is low.
2. The invention takes into consideration the same and different points of the terahertz low frequency band and the millimeter wave frequency band. The low-frequency-band terahertz cloud-detection radar detects the coincidence of a backscattering mechanism, and the radar reflectivity factor is obtained according to a meteorological radar equation as the millimeter wave cloud-detection radar. The terahertz wave band is different from the millimeter wave band, the size of part of ice cloud particles is the same magnitude as the wavelength, the Mie scattering effect is prominent, and larger error is caused according to Rayleigh scattering calculation; for the water cloud, the terahertz wave absorption attenuation is more serious than that of millimeter waves, and the correction of the terahertz cloud-sensing radar needs to consider different attenuation amounts, so that an effective calibration result is obtained.
Drawings
Fig. 1 is a flow chart of a terahertz cloud testing radar reflectivity factor calibration method based on millimeter wave radar.
Detailed Description
The following describes a preferred embodiment of the present invention in detail with reference to fig. 1.
As shown in fig. 1, the invention provides a terahertz cloud testing radar reflectivity factor calibration method based on millimeter wave radar, which comprises the following steps:
s1, correcting transmitting power and echo power by adopting internal calibration measured values;
s2, calculating radar reflectivity factors under the conditions of spherical particles and Rayleigh scattering;
s3, performing Mie scattering correction and attenuation correction on the radar reflectivity factor;
and S4, evaluating the accuracy of the radar reflectivity factor.
The terahertz cloud testing radar system comprises an internal calibration link and has the capability of measuring radar transmitting power and receiver gain. Taking ground-based radar observation as an example, the millimeter wave cloud-based radar and the terahertz cloud-based radar are adjacently placed, and meanwhile, the same cloud target is observed, and echo data are respectively obtained. According to a weather radar equation, the terahertz cloud-testing radar reflectivity factor and the millimeter wave radar reflectivity factor can be calculated by utilizing echo data, radar transmitting power, receiver gain and the like. And correcting the terahertz cloud radar reflection factor by considering that the terahertz wavelength is short and similar to the cloud particle size and the Mie scattering effect exists. And repeatedly observing for multiple times to obtain enough sample data, correcting the deviation of the terahertz cloud-measuring radar reflection factor after Mie scattering correction by taking the average value of the millimeter wave radar reflection factor as a reference, and calculating the root mean square error to obtain the terahertz cloud-measuring radar precision. The effectiveness of radar reflectivity factor accuracy depends on millimeter wave radar accuracy, path deviation and mie scattering correction accuracy.
The step S1 includes the steps of:
the transmit power at the antenna end, which is associated with a high power amplifier, may vary over time and is monitored in real time. The peak power detector of the cloud radar consists of a detection diode and an amplifier. Power value P obtained by detection t0 And the actual transmission power P t The relation of (2) is that
P t ＝P t0 L 1 (1)
Wherein L is 1 The scaling factor for the detector diode is dependent on the operating temperature and is provided by the manufacturer.
Power P output by receiver r0 And received power P r The relation of (2) is that
P r ＝P r0 L 2 /A r (2)
Wherein L is 2 For losses between the antenna and the receiver input, this quantity is measured before the radar complete machine is assembled; a is that r For the receiver gain. When the gain of the receiver is scaled, an adjustable attenuator is adopted to attenuate the transmitted signals to different intensities, the signals are input into the receiver, the output power is obtained through signal processing, and the input-output curve of the receiver is obtained, so that the gain of the receiver is determined.
The step S2 includes the steps of:
the radar back-scattering area per unit volume is also called radar reflectivity, and the calculation formula is:
wherein P is r For received power, the unit is W; p (P) t The unit is W for transmitting power; r is distance, and the unit is m; c is a radar constant, and the calculation formula is:
wherein lambda is wavelength and the unit is m; g t 、G r The gain of the transmitting antenna and the gain of the receiving antenna are respectively; ρ r The unit is m, which is the distance resolution; omega is a normalized two-way antenna pattern calculated as gaussian beams:
wherein θ andthe beam widths in rad are azimuth and elevation 3dB, respectively.
Under the conditions of spherical particles and Rayleigh scattering, the calculation formula of the radar reflectivity factor is as follows:
wherein: k= (m-1)/(m+2), m represents the complex refractive index of water or ice particles, which is related to wavelength.
The step S3 includes the steps of:
in the terahertz wave band, the particle size of ice cloud is generally smaller than the wavelength, and Rayleigh scattering approximation can be used for calculating the particle reflectivity factor, but for large particles which do not meet the Rayleigh scattering condition, larger deviation can be caused according to the fact that the radar reflectivity factor is proportional to the six-degree of the particle size. In order to correct the deviation, the ratio f of actual scattering and Rayleigh scattering of terahertz wave band ice cloud particles is introduced Mie 。
Attenuation correction includes atmospheric attenuation correction (path attenuation correction) and cloud particle scattering absorption correction. The atmospheric attenuation correction refers to the absorption of electromagnetic waves by water and oxygen in the atmosphere, and the atmospheric attenuation coefficient k a The method can be calculated by adopting atmospheric temperature and humidity data and Liebe mode. The cloud particle scattering absorption correction is calculated firstly by the cloud attenuation coefficient k c It represents the attenuation ratio of electromagnetic wave in unit distance, and the cloud attenuation coefficient k c And true radar reflectivity factor Z r There are generally the followingRelationship:
wherein k is c And Z r Are in km respectively -1 And mm 6 m -3 The method comprises the steps of carrying out a first treatment on the surface of the Alpha and beta are regression coefficients.
Terahertz measurement Yun Lei is carried out, cloud particle scattering energy within a specific received distance is the result of bidirectional attenuation of atmosphere and cloud layers on a path passing through the cloud particle scattering energy, and the actual measured value Z of the radar reflectivity factor is obtained according to formula (6) m And true value Z r The relation of (2) is:
Z m (R)＝Z r (R)·τ(R) (8)
where τ is the two-pass transmission of the cloud at distance R.
Where k is the atmospheric attenuation coefficient k a And a cloud attenuation coefficient k c And (3) summing; q (Q) ext The extinction cross section is the sum of a scattering cross section and an absorption cross section; n (D) is a cloud particle size probability distribution, typically using Gamma distribution; d (D) max ，D min The maximum and minimum of the cloud particle size, respectively.
The attenuation correction process is as follows:
1. calculating the atmospheric attenuation coefficient k a According to k c =0, calculating the double pass transmittance τ (R) to obtain the radar reflectivity factor Z after correction for atmospheric attenuation m1 ：
Z m1 (R)＝Z m (R)/τ(R)
2. According to a library-by-library correction method, correcting cloud attenuation, calculating a double pass transmittance tau (R) from a distance unit nearest to a radar, and calculating a target value from the distanceThe double-pass transmittance from the nearest distance unit of the radar to the ith-1 distance library is tau i-1 . The actual value after the attenuation correction of the radar reflectivity factor of the ith range bin can be approximated by:
Z m2 (R)＝[Z m1 (R)/τ i-1 ]exp{α[Z m1 (R)/τ i-1 ] β ΔR}
wherein: Δr is the distance resolution.
3. Inverting the cloud particle size probability distribution N (D) to obtain the Mie scattering correction parameter f Mie Obtain the correction value Z m3 ＝Z m2 f Mie Repeating step 2 to obtain new Z by means of library-by-library attenuation correction m2 ' then carrying out data inversion and Mie scattering correction to obtain a new correction value Z m3 ' until a value Z is defined m3 Rate of change of |Z' m3 -Z m3 |/Z m3 Less than a threshold, typically less than 10%, resulting in a radar reflectivity factor Z for the range bin r (R)。
The step S4 includes the steps of:
calculating the millimeter wave radar reflectivity factor Z according to (1) to (6) r1 Average value of (2) and terahertz radar reflectivity factor Z r2 Average value of (2). According to steps S1-S3, respectively calculating radar reflectivity factors of the millimeter wave cloud radar and the terahertz radar Yun Lei to obtain the distribution Zr of the millimeter wave radar reflectivity factors in the distance direction 1 (R) distribution Zr of terahertz cloud radar reflectivity factors in distance direction 2 (R) calculation of Zr in one sample 1 (R)-Zr 2 (R) averaging M samples to obtain the terahertz cloud-measuring radar measurement deviation delta Z and Zr 2 (R) adding to obtain a correction result.
Calculating root mean square error by using the corrected terahertz cloud radar reflectivity factor to evaluate measurement accuracy, wherein the calculation formula is as follows:
wherein Z is r2,i (R) is the range-wise distribution of the terahertz cloud radar reflectivity factor of the ith sample,and the distance distribution of the mean value of the terahertz cloud radar reflectivity factors is obtained.
The invention has the following advantages:
1. and correcting the radar reflectivity factor deviation of the terahertz cloud-measuring radar by using the calibrated millimeter wave radar measurement data as a reference value. The internal calibration method is filled with the fact that only parameters of the subsystem are measured, influences between the antenna and the subsystem are not considered, and meanwhile compared with the external calibration method, a test tower or a hanging test is not needed to be erected, and cost is low.
2. The invention takes into consideration the same and different points of the terahertz low frequency band and the millimeter wave frequency band. The low-frequency-band terahertz cloud-detection radar detects the coincidence of a backscattering mechanism, and the radar reflectivity factor is obtained according to a meteorological radar equation as the millimeter wave cloud-detection radar. The terahertz wave band is different from the millimeter wave band, the size of part of ice cloud particles is the same magnitude as the wavelength, the Mie scattering effect is prominent, and larger error is caused according to Rayleigh scattering calculation; for the water cloud, the terahertz wave absorption attenuation is more serious than that of millimeter waves, and the correction of the terahertz cloud-sensing radar needs to consider different attenuation amounts, so that an effective calibration result is obtained.
It should be noted that, in the embodiments of the present invention, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the embodiments, and do not indicate or imply that the apparatus or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the 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.
While the present invention has been described in detail through the foregoing description of the preferred embodiment, it should be understood that the foregoing description is not to be considered as limiting the invention. Many modifications and substitutions of the present invention will become apparent to those of ordinary skill in the art upon reading the foregoing. Accordingly, the scope of the invention should be limited only by the attached claims.
Claims (4)
1. A terahertz cloud measurement radar reflectivity factor calibration method based on millimeter wave radar is characterized by comprising the following steps:
s1, correcting transmitting power and echo power by adopting internal calibration measured values;
s2, calculating radar reflectivity factors under the conditions of spherical particles and Rayleigh scattering;
s3, performing Mie scattering correction and attenuation correction on the radar reflectivity factor;
s3.1, calculating an atmospheric attenuation coefficient k by adopting atmospheric temperature and humidity data and Liebe mode a According to the cloud attenuation coefficient k c =0, calculating the double pass transmittance τ (R) of the cloud at the distance R to obtain the radar reflectivity factor Z after correction for atmospheric attenuation m1 ：
Z m1 (R)＝Z m (R)/τ(R)
Where k is the atmospheric attenuation coefficient k a And a cloud attenuation coefficient k c And (3) summing;
s3.2, correcting cloud attenuation according to a library-by-library correction method, calculating double-pass transmittance tau (R) from a distance unit closest to the radar, wherein the double-pass transmittance tau from the distance unit closest to the radar to the i-1 th distance library is i-1 The actual value after attenuation correction of the radar reflectivity factor of the ith range bin is approximated by:
Z m2 (R)＝[Z m1 (R)/τ i-1 ]exp{α[Z m1 (R)/τ i-1 ] β ΔR}
wherein Δr is the distance resolution;
wherein alpha and beta are regression coefficients;
s3.3, inverting the probability distribution N (D) of the size of the cloud particles to obtain the Mie scattering correction parameter f Mie Calculate the correction value Z m3 ＝Z m2 f Mie Repeating the step S3.2, and obtaining a new Z by performing the attenuation correction on a library-by-library basis m2 ' then carrying out data inversion and Mie scattering correction to obtain a new correction value Z m3 ' until a value Z is defined m3 Rate of change of |Z' m3 -Z m3 |/Z m3 Less than a threshold value, obtaining a radar reflectivity factor Z of the range bin r (R)；
And S4, evaluating the accuracy of the radar reflectivity factor.
2. The method for calibrating the terahertz cloud radar reflectivity factor based on millimeter wave radar according to claim 1, wherein in the step S1,
actual transmit power P t And the power value P obtained by detection t0 The relation of (2) is:
P t ＝P t0 L 1 (1)
wherein L is 1 As a scaling factor for the detector diode, is dependent on the operating temperature;
received power P r Power P output from receiver r0 The relation of (2) is:
P r ＝P r0 L 2 /A r (2)
wherein L is 2 Is the loss between the antenna and the receiver input; a is that r For the receiver gain.
3. The method for calibrating the terahertz cloud radar reflectivity factor based on millimeter wave radar according to claim 2, wherein the step S2 includes the steps of:
the radar reflectivity calculation formula is:
wherein P is r For received power, the unit is W; p (P) t The unit is W for transmitting power; r is distance, and the unit is m; c is a radar constant, and the calculation formula is:
wherein lambda is wavelength and the unit is m; g t 、G r The gain of the transmitting antenna and the gain of the receiving antenna are respectively; ρ r The unit is m, which is the distance resolution; omega is a normalized two-way antenna pattern calculated as gaussian beams:
wherein θ andthe beam widths of the azimuth direction and the pitching direction are 3dB respectively, and the unit is rad;
under the conditions of spherical particles and Rayleigh scattering, the calculation formula of the radar reflectivity factor is as follows:
where k= (m-1)/(m+2), m represents the complex refractive index of water or ice particles, which is related to wavelength.
4. The method for calibrating the terahertz cloud radar reflectivity factor based on millimeter wave radar as set forth in claim 3, wherein the step S4 includes the steps of:
calculating the millimeter wave radar reflectivity factor Z according to (1) to (6) r1 Average value of (2) and terahertz radar reflectivity factor Z r2 According to the average value of the (1), respectively calculating radar reflectivity factors of the millimeter wave cloud radar and the terahertz radar Yun Lei according to the steps S1-S3 to obtain the distribution Zr of the millimeter wave radar reflectivity factors in the distance direction 1 (R) distribution Zr of terahertz cloud radar reflectivity factors in distance direction 2 (R) calculation of Zr in one sample 1 (R)-Zr 2 (R) averaging M samples to obtain the terahertz cloud-measuring radar measurement deviation delta Z and Zr 2 (R) adding to obtain a correction result;
calculating root mean square error by using the corrected terahertz cloud radar reflectivity factor to evaluate measurement accuracy, wherein the calculation formula is as follows:
wherein Z is r2,i (R) terahertz cloud detection radar inverse for ith sampleThe distance of the emissivity factor is distributed towards,and the distance distribution of the mean value of the terahertz cloud radar reflectivity factors is obtained.
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