Under-cloud aerosol extinction coefficient laser radar detection inversion method

Abstract

The invention discloses an under-cloud aerosol extinction coefficient laser radar detection inversion method, and the method comprises the steps: obtaining an aerosol extinction coefficient corresponding to an echo signal of a laser radar in a horizontal direction, and taking the aerosol extinction coefficient as a first calibration value EXTI; the height of a calibration point at the cloud bottom is judged according to the distance correction square signal at the set moment, and an atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom is obtained and serves as a second calibration value EXT0; obtaining a second extinction coefficient profile based on the second calibration value EXT0, obtaining an extinction coefficient at the first height X according to the second extinction coefficient profile, and taking the extinction coefficient as a second calibration value EXTX; the first height X is greater than the height of the blind area; the first calibration value EXTI and the second calibration value EXTX are compared, when EXTX-EXTI is larger than EXTI * delta, the second calibration value EXT0 is adjusted, the step of obtaining the second extinction coefficient profile is executed again based on the adjusted second calibration value EXT0 till EXTX-EXTI is smaller than EXTI * delta, the second calibration value EXTX is output, and delta is a relative error. The method has the advantage that the aerosol extinction coefficient can be accurately inverted even in the presence of clouds based on the method.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radar, and in particular relates to a laser radar detection inversion method for sub-cloud aerosol extinction coefficient. Background Art

[0002] LiDAR can not only monitor the intensity changes of atmospheric aerosols, but also observe the vertical distribution of atmospheric aerosols, and perform quantitative analysis after inverting the observation results.

[0003] When performing vertical detection, the LiDAR uses the Fernald method to invert the atmospheric aerosol extinction coefficient in most cases. This requires finding a height with less atmospheric aerosol content as the calibration point height, and using Fernald backward integration to obtain the aerosol extinction vertical profile. However, when there are low and thick clouds in the sky, the LiDAR echo signal first increases sharply and then decreases, and eventually tends to background noise. In this case, the laser cannot penetrate the cloud layer, and it is impossible to determine the calibration point height required for inversion, which makes it difficult to invert the aerosol under the cloud. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method for detecting and inverting the aerosol extinction coefficient under clouds by a lidar. The specific technical scheme is as follows:

[0005] A method for detecting and inverting the subcloud aerosol extinction coefficient by lidar, comprising:

[0006] Obtain the aerosol extinction coefficient corresponding to the laser radar echo signal in the horizontal direction as the first calibration value EXT I ; Determine the height of the calibration point at the cloud bottom according to the distance correction square signal at the set time, and obtain the atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom, which is used as the second calibration value EXT 0 ;

[0007] Based on the second calibration value EXT 0 Obtain a second extinction coefficient profile, obtain the extinction coefficient at the first height X according to the second extinction coefficient profile, and use it as the second calibration value EXT X ; The first height X is greater than the blind spot height;

[0008] Compare the first calibration value EXT I and the second calibration value EXT X ,|EXT X -EXT I |>EXT I ·δ, adjust the second calibration value EXT 0 , based on the adjusted second calibration value EXT 0Return to the above step of obtaining the second extinction coefficient profile until |EXT X -EXT I |<EXT I ·δ, output the second calibration value EXT X , where δ is the relative error.

[0009] The inversion method of the aerosol extinction coefficient under clouds as described above, further, the obtaining of the aerosol extinction coefficient corresponding to the laser radar echo signal in the horizontal direction includes: obtaining the aerosol extinction coefficient of the laser radar echo signal in the horizontal direction by using the slope method.

[0010] The above-mentioned inversion method of the aerosol extinction coefficient under the cloud further uses the slope method to obtain the aerosol extinction coefficient of the laser radar echo signal in the horizontal direction as the first calibration value EXT I ,include:

[0011] Assuming that the atmosphere is uniform, the atmospheric backscatter echo signal power P(Y) received by the lidar at a horizontal distance Y is:

[0012] P(Y)=P t k -2 β H exp(-2α H Y) (2)

[0013] Where P t is the laser transmission power (W), k is the radar system constant (W km 3 ·Sr), β H is the horizontal atmospheric backscatter coefficient (km -1 Sr -1 ), α H Indicates the horizontal atmospheric extinction coefficient (km -1 );

[0014] Multiply both sides of formula (2) by the square of the distance, take the logarithm and take the derivative to obtain:

[0015]

[0016] Under the condition of uniform atmospheric level, dβ / dz=0; then:

[0017]

[0018] For ln[P(Y)Y 2 ] and Y are fitted by the least square method, and half of its slope is the horizontal atmospheric extinction coefficient α H , α H As the first calibration value EXT I .

[0019] The inversion method of the aerosol extinction coefficient under the cloud as described above, further, the second calibration value EXT 0 Obtain a second extinction coefficient profile, including the second calibration value EXT 0 The second extinction coefficient profile is obtained using the Fernald backward integration method.

[0020] As described above, the inversion method of the aerosol extinction coefficient under the cloud further includes that the value range of the horizontal distance Y received by the laser radar is 60-1000m.

[0021] In the inversion method of the aerosol extinction coefficient under clouds as described above, further, the first height X is greater than the blind spot height, and specifically, the first height X has a value range of 60-1000m.

[0022] The inversion method of the aerosol extinction coefficient under the cloud as described above, further, the adjustment of the second calibration value EXT 0 ,include:

[0023] The ratio of the laser radar echo signal to the molecular signal R(Z C ) Increase the iteration step value and update it to the ratio of the laser radar echo signal to the molecular signal R(Z C ) target value, based on the ratio of the laser radar echo signal to the molecular signal R(Z C ) The target value obtains the corresponding backscatter coefficient β α (Z C ), using the aerosol extinction backscattering ratio formula S a Get the aerosol extinction coefficient boundary value α a (Z c ), the aerosol extinction coefficient α a (Z c ) is the atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom, which is used as the second calibration value EXT corresponding to the target value 0 .

[0024] In the inversion method of the sub-cloud aerosol extinction coefficient as described above, further, the iteration step value ranges from 0.01 to 0.5.

[0025] The inversion method of the aerosol extinction coefficient under the cloud as described above, further, the ratio of the laser radar echo signal to the molecular signal R(Z C ) has an initial value of 1.01.

[0026] In the inversion method of the sub-cloud aerosol extinction coefficient as described above, further, the relative error δ has a value range of 0.01-0.05.

[0027] The advantages of the present invention are:

[0028] (1) The method of the present application does not rely on an absolutely accurate calibration height, and the inversion results of the aerosol under the cloud can be obtained within a certain range. The extinction coefficient color map obtained based on the method of the present application can clearly invert the position of the cloud layer and the distribution of aerosol under the cloud, indicating that the method described in the present application can accurately invert the aerosol extinction coefficient even in the presence of clouds.

[0029] (2) In this application, the calibration height remains unchanged during each iteration, and the ratio of the laser radar echo signal to the molecular signal R (Z C ) and continuously iterate to achieve the goal of getting closer to the true value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention provides a flow chart of a method for detecting and inverting the sub-cloud aerosol extinction coefficient using a laser radar.

[0031] Figure 2 This is a graph of the relationship between the range correction signal and altitude at 11:30 (local time) on April 9, 2024.

[0032] Figure 3 The present invention is a flowchart of a method for detecting and inverting the sub-cloud aerosol extinction coefficient using a laser radar in an embodiment of the present invention.

[0033] Figure 4 The upper middle part is a color map of the extinction coefficient obtained by inverting the portable infrared lidar echo signal using the traditional Fernald backward integration method, and the lower part is a color map of the extinction coefficient obtained by inverting the portable infrared lidar signal using this method.

[0034] Figure 5 Comparison diagram of lidar echo signals obtained by traditional Fernald backward integration method and this method.

[0035] Figure 6 is the average relative error of this method at different heights. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. In the description of the embodiments of the present application, it should be understood that the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0037] When LiDAR is used for vertical detection, the Fernald method is usually used to invert the atmospheric aerosol extinction coefficient, which can be used to quantitatively analyze the aerosol content. C According to the Fernald backward integration formula (see formula 1), if we want to obtain the atmospheric aerosol extinction coefficient α based on the lidar echo signal, a (Z), four parameters need to be determined, namely, aerosol extinction backscattering ratio S a , air molecule extinction backscattering ratio S m , the extinction coefficient of air molecules α m (Z), calibration point height Z C The aerosol extinction coefficient α at a (Z c ).

[0038] The aerosol extinction backscattering ratio S a =α a (Z) / β a (Z) is usually between 10 and 90 Sr. Air molecule extinction backscattering ratio S m Usually a constant, i.e. S m =8π / 3. Extinction coefficient of air molecules α m (Z) is usually obtained from the US Standard Atmosphere Model. Usually, the first three parameters are relatively easy to determine. C The aerosol extinction coefficient α at a (Z c ) It is usually difficult to get an accurate value. The selection of the calibration point height usually needs to be determined through a clean atmosphere. Calculate the calibration point height Z C It is usually calculated by the ratio of the laser radar range correction signal to the molecular backscatter coefficient (P(Z)·Z 2 / β m) is obtained. The height of the calibration point Z C The boundary value of atmospheric aerosol extinction coefficient is usually an empirical value, which is 1+β a (Z c ) / β m (Z c )=1.01 to infer the atmospheric aerosol backscattering coefficient β at the calibration point height a (Z c ) is concluded.

[0039]

[0040] Wherein, P(Z) is the power (W) of the atmospheric scattered echo signal received by the lidar at a distance of Z.

[0041] After analysis, when there are low and thick clouds in the sky, the lidar echo signal first increases sharply and then decreases, and finally tends to background noise. This signal trend shows that the laser does not penetrate the cloud layer, which makes it challenging to determine the calibration height required for the inversion. Therefore, this introduces a significant error in the inversion of the aerosol extinction coefficient under the clouds. Since it is impossible to determine the height of the calibration point, it is impossible to invert the true atmospheric aerosol extinction coefficient using only the Fernald method. In this context, if Figure 1 As shown, the present application discloses a method for detecting and inverting the aerosol extinction coefficient under clouds by a laser radar, comprising:

[0042] Obtain the aerosol extinction coefficient corresponding to the laser radar echo signal in the horizontal direction as the first calibration value EXT I ; Determine the height of the calibration point at the cloud bottom according to the distance correction square signal at the set time, and obtain the atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom, which is used as the second calibration value EXT 0 ;

[0043] Based on the second calibration value EXT 0 Obtain a second extinction coefficient profile, obtain the extinction coefficient at the first height X according to the second extinction coefficient profile, and use it as the second calibration value EXT X ; The first height X is greater than the blind spot height;

[0044] Compare the first calibration value EXT I and the second calibration value EXT X ,|EXT X -EXT I |>EXT I ·δ, adjust the second calibration value EXT 0 , based on the adjusted second calibration value EXT 0 Return to the above step of obtaining the second extinction coefficient profile until |EXT X-EXT I |<EXT I ·δ, output the second calibration value EXT X , where δ is the relative error.

[0045] In one of the embodiments, obtaining the aerosol extinction coefficient corresponding to the laser radar echo signal in the horizontal direction includes: obtaining the aerosol extinction coefficient of the laser radar echo signal in the horizontal direction using a slope method.

[0046] In detail, assuming that the atmosphere is uniform, the atmospheric backscatter echo signal power P(Y) received by the lidar at a horizontal distance Y is:

[0047] P(Y)=P t k -2 β H exp(-2α H Y) (2)

[0048] Where P t is the laser transmission power (W), k is the radar system constant (W km 3 ·Sr), β H is the horizontal atmospheric backscatter coefficient (km -1 Sr -1 ), α H Indicates the horizontal atmospheric extinction coefficient (km -1 ).

[0049] Multiply both sides of formula (2) by the square of the distance, take the logarithm and take the derivative to obtain:

[0050]

[0051] Under the condition of uniform atmospheric level, dβ / dz=0. Then:

[0052]

[0053] For ln[P(Y)Y 2 ] and Y are fitted by the least square method, and half of its slope is the horizontal atmospheric extinction coefficient α H , α H As the first calibration value EXT I In order to obtain more accurate parameters, the value range of Y is 60-90m. Since the extinction coefficient of air molecules near the ground is one order of magnitude smaller than that of atmospheric aerosols, it can also be considered that α H The atmospheric aerosol extinction coefficient will not cause too much error.

[0054] In one embodiment, the height of the calibration point at the cloud bottom is determined based on the distance correction square signal at a set time, such as Figure 2 As shown in the figure, the relationship between the distance correction signals obtained during the experimental observation is obtained. The distance correction square signal at a certain moment is used to determine the height of the calibration point at the cloud bottom. The height of the cloud bottom is about 1 km. In this case, when thick clouds appear, the lidar cannot penetrate the cloud layer, that is, it cannot detect the effective atmospheric echo signal above the cloud. Therefore, it is impossible to determine the height of the calibration point required for inversion through the height of the "clean atmosphere" in the traditional Fernald method. In order to invert the aerosol extinction coefficient under the cloud, the cloud bottom is selected as the calibration point height of about 1.35-1.4km in this method.

[0055] The atmospheric extinction coefficient corresponding to the height of the calibration point at the bottom is obtained as the second calibration value EXT 0 Based on the second calibration value EXT 0 Specifically, the height Z of the calibration point C Select the height of the clean atmosphere that contains almost no atmospheric aerosols and calculate the calibration point height Z C The ratio of the laser radar echo signal to the molecular signal R(Z C ) is determined by the minimum value of. Calibration point height Z C The backscatter coefficient β α (Z C ) is usually selected by R(Z C ) empirical value, the initial value is 1.01, and 1.01 is used as the ratio of the laser radar echo signal to the molecular signal R(Z C ) target value, given by Inversely calculate the height Z of the calibration point C The atmospheric extinction coefficient β α (Z C ), where the height of the calibration point is Z C The molecular backscattering coefficient β m (Z C ), given by the US Standard Atmosphere Model (which can be understood as a known value). According to the inferred backscatter coefficient β α (Z C ), and then use the aerosol extinction backscattering ratio formula S a Get the aerosol extinction coefficient boundary value α a (Z c ), the aerosol extinction coefficient α a (Z c ) is the atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom, which is used as the second calibration value EXT 0 The aerosol extinction backscattering ratio formula corresponding to lasers of different wavelengths is S aThe values ​​between 10 and 90 Sr are different. For example, the aerosol extinction backscattering ratio formula for a laser with a wavelength of 1064 nm is S a The value is 40. Therefore, after determining the laser wavelength, the aerosol extinction backscattering ratio formula S a The value of is determined, which can be realized by inferring the backscattering coefficient β α (Z C ), and then use the aerosol extinction backscattering ratio formula S a Get the aerosol extinction coefficient boundary value α a (Z c ).

[0056] In one embodiment, the second calibration value EXT 0 Obtain a second extinction coefficient profile, including the second calibration value EXT 0 The second extinction coefficient profile is obtained using the Fernald backward integration method.

[0057] The first height X is greater than the blind spot height. Specifically, the first height X is in the range of 60-80 m. The first height X can be any one of 60 m, 65 m, 68 m, 70 m, 72 m, 75 m, 78 m, and 80 m. The extinction coefficient at the first height X is obtained according to the second extinction coefficient profile and used as the second calibration value EXT X When the first height X is 60m, the second calibration value is EXT 60 , when the first height X is 70m, the second calibration value is EXT 70 , and so on for other heights.

[0058] Adjust the second calibration value EXT 0 ,include:

[0059] The ratio of the laser radar echo signal to the molecular signal R(Z C ) Increase the iteration step value and update it to the ratio of the laser radar echo signal to the molecular signal R(Z C ) target value, based on the ratio of the laser radar echo signal to the molecular signal R(Z C ) The target value obtains the corresponding backscatter coefficient β α (Z C ), using the aerosol extinction backscattering ratio formula S a Get the aerosol extinction coefficient boundary value α a (Z c ), the aerosol extinction coefficient α a (Z c ) is the atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom, which is used as the second calibration value EXT corresponding to the target value 0.

[0060] In one of the embodiments, the iteration step value ranges from 0.01 to 0.5, and the smaller the iteration step value is, the more accurate the data obtained by measurement is.

[0061] In one of the embodiments, the relative error δ is in the range of 0.01-0.05, and the smaller the relative error is, the more accurate the data obtained by measurement is.

[0062] like Figure 2 As shown, with Y=70, S a =40, X = 70, δ = 0.01, the iteration step is 0.01, the relative error δ is 0.01, a method for detecting and inverting the aerosol extinction coefficient under clouds by lidar, including

[0063] The slope method is used to obtain the aerosol extinction coefficient corresponding to the laser radar echo signal in the horizontal direction as the first calibration value EXT I ; The relationship between the distance correction signals obtained when observing at 11:30 on April 9, 2024. Figure 3 As shown, the calibrated height of the cloud base is 1 km. According to R(Z C ) has an initial value of 1.01, and the calibration point height Z C The molecular backscattering coefficient β m (Z C ) is known, the atmospheric extinction coefficient β corresponding to the calibration point height at the cloud base is obtained α (Z C ), which is used as the second calibration value EXT 0 ;

[0064] Based on the second calibration value EXT 0 Obtain the second extinction coefficient profile, obtain the extinction coefficient at the first height of 70m according to the second extinction coefficient profile, and use it as the second calibration value EXT 70 ;

[0065] Compare the first calibration value EXT I and the second calibration value EXT 70 ,|EXT 70 -EXT I |>EXT I 0.01, R(Z C ) is based on the iteration step size, the value is 1.02, based on the calibration point height Z C The molecular backscattering coefficient β m (Z C ) is known, the atmospheric extinction coefficient β corresponding to the calibration point height at the cloud base is retrieved α (Z C), which is used as the adjusted second calibration value EXT 0 , based on the adjusted second calibration value EXT 0 Return to the above step of obtaining the second extinction coefficient profile until |EXT 70 -EXT I |<EXT I 0.01, output the second calibration value EXT X , thereby obtaining the corresponding second extinction coefficient profile. 70 -EXT I |<EXT I · Before 0.01, R(Z C ) both increase the iteration step size based on the last value, R(Z C ) values ​​are 1.01, 1.02, 1.03, etc.

[0066] Compared with the traditional Fernald backward integration, this method can clearly invert the specific details of the extinction coefficient under clouds. Figure 4 The upper middle part is a color map of the extinction coefficient obtained by inverting the portable infrared lidar echo signal using the traditional Fernald backward integration method. Figure 4 The lower middle part is the extinction coefficient color map obtained by inverting the portable infrared lidar signal using this method. It can be seen from these two pictures that the traditional Fernald backward integration method cannot clearly invert the position of the clouds, and there are "blanks" in the aerosol extinction coefficient under the clouds, which contains negative values. This shows that the traditional Fernald method is significantly affected by the cloud cover and cannot accurately calibrate the portable infrared lidar echo signal, resulting in certain errors. However, the extinction coefficient color map obtained based on the method of the present application can clearly invert the position of the clouds and the distribution of aerosols under the clouds. It can be clearly seen that the processing results of this method for the distribution of clouds and aerosols under the clouds are better than those of the traditional Fernald method. The method described in this application can accurately invert the aerosol extinction coefficient even in the presence of clouds.

[0067] Regarding the accuracy of the verification algorithm, such as Figure 5 As shown in the figure, the laser radar echo signal of a certain moment of the high-energy radar is selected and processed by the traditional Fernald backward integration and this method respectively. The comparison shows that the two methods are not much different. Figure 6 It can be seen that the maximum error of the results obtained by this method relative to the standard value is about 6.5%, and the average relative error is less than 5%. It can be concluded that the inversion results of this method are relatively accurate.

[0068] In the description of this specification, the description with reference to the terms "some embodiments" or "examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0069] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A method for detecting and inverting the aerosol extinction coefficient under clouds by using a laser radar, characterized in that: include: Obtain the aerosol extinction coefficient corresponding to the laser radar echo signal in the horizontal direction as the first calibration value EXT I ; Determine the height of the calibration point at the cloud bottom according to the distance correction square signal at the set time, and obtain the atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom, which is used as the second calibration value EXT0; Based on the second calibration value EXT0, a second extinction coefficient profile is obtained, and the extinction coefficient at the first height X is obtained according to the second extinction coefficient profile, and is used as the second calibration value EXT X ; The first height X is greater than the blind spot height; Compare the first calibration value EXT I and the second calibration value EXT X ,|EXT X -EXT I |>EXT I ·δ, adjust the second calibration value EXT0, and return to the above step of obtaining the second extinction coefficient profile based on the adjusted second calibration value EXT0 until |EXT X -EXT I |<EXT I ·δ, output the second calibration value EXT X , where δ is the relative error.

2. The method for detecting and inverting the subcloud aerosol extinction coefficient by laser radar according to claim 1, characterized in that: The obtaining of the aerosol extinction coefficient corresponding to the laser radar echo signal in the horizontal direction includes: obtaining the aerosol extinction coefficient of the laser radar echo signal in the horizontal direction by using a slope method.

3. The method for detecting and inverting the subcloud aerosol extinction coefficient by laser radar according to claim 2, characterized in that: The slope method is used to obtain the aerosol extinction coefficient of the lidar echo signal in the horizontal direction as the first calibration value EXT I ,include: Assuming that the atmosphere is uniform, the atmospheric backscatter echo signal power P(Y) received by the lidar at a horizontal distance Y is: P(Y)=P t kY -2 β H exp(-2α H Y) (2) Where P t is the laser transmission power (W), k is the radar system constant (W km 3 ·Sr), β H is the horizontal atmospheric backscatter coefficient (km -1 Sr -1 ), α H Indicates the horizontal atmospheric extinction coefficient (km -1 ); Multiply both sides of formula (2) by the square of the distance, take the logarithm and take the derivative to obtain: Under the condition of uniform atmospheric level, dβ / dz=0; then: For ln[P(Y)Y 2 ] and Y are fitted by the least square method, and half of its slope is the horizontal atmospheric extinction coefficient α H , α H As the first calibration value EXT I .

4. The method for detecting and inverting the subcloud aerosol extinction coefficient by laser radar according to claim 1, characterized in that: The obtaining of the second extinction coefficient profile based on the second calibration value EXT0 includes obtaining the second extinction coefficient profile using a Fernald backward integration method based on the second calibration value EXT0.

5. The method for detecting and inverting the subcloud aerosol extinction coefficient by laser radar according to claim 1, characterized in that: The value range of the horizontal distance Y received by the laser radar is 60-1000m.

6. The method for detecting and inverting the sub-cloud aerosol extinction coefficient by laser radar according to claim 1, characterized in that: The first height X is greater than the blind spot height. Specifically, the first height X is in the range of 60-1000 m.

7. The method for detecting and inverting the sub-cloud aerosol extinction coefficient by laser radar according to claim 1, characterized in that: The adjusting the second calibration value EXT0 includes: The ratio of the laser radar echo signal to the molecular signal R(Z C ) Increase the iteration step value and update it to the ratio of the laser radar echo signal to the molecular signal R(Z C ) target value, based on the ratio of the laser radar echo signal to the molecular signal R(Z C ) The target value obtains the corresponding backscatter coefficient β α (Z C ), using the aerosol extinction backscattering ratio formula S a Get the aerosol extinction coefficient boundary value α a (Z c ), the aerosol extinction coefficient α a (Z c ) is the atmospheric extinction coefficient corresponding to the height of the calibration point at the cloud bottom, which serves as the second calibration value EXT0 corresponding to the target value.

8. The method for detecting and inverting the sub-cloud aerosol extinction coefficient by laser radar according to claim 7, characterized in that: The iteration step value ranges from 0.01 to 0.

5.

9. The method for detecting and inverting the sub-cloud aerosol extinction coefficient by laser radar according to claim 7, characterized in that: The ratio of the laser radar echo signal to the molecular signal R(Z C ) has an initial value of 1.

01.

10. The method for detecting and inverting the sub-cloud aerosol extinction coefficient by laser radar according to claim 1, characterized in that: The relative error δ ranges from 0.01 to 0.05.

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