Method for Detecting Atmospheric Characteristics of Geometric Factor Region by Using Scanning Lidar

Abstract

A method for detecting the atmospheric characteristics of the geometric factor region by using a scanning lidar, comprising the following steps: S1. Vertically detect the lidar, and calculate the aerosol extinction coefficients at each height within the range from the height z above the geometric factor region to the calibration distance z according to the Fernald method; g above to the calibration distance z c ; S2. Obliquely scan the lidar from the vertical direction to the horizontal direction at a certain zenith angle in sequence, that is, fan-shaped scanning. The number of scanning groups is n, the height resolution is dr, and find out the zenith angle a(n) of each scanning group and its corresponding calibration height z(n); S3. Assume that the whole atmosphere is horizontally uniform during the fan-shaped scanning process, and calculate the aerosol extinction coefficient α within the range of the geometric factor region z from the aerosol extinction coefficient profiles measured by each scanning group. g ; The present invention can measure the atmospheric characteristics within the lidar geometric factor region by using a scanning lidar, and can provide measurement data within the corresponding geometric factor for other lidar systems. a ​

Description

Technical Field

[0001] The present invention relates to the technical field of laser radar, and in particular to a method for detecting atmospheric characteristics of a geometric factor region by using a scanning laser radar. Background Art

[0002] Aerosols, as condensation nuclei, can directly affect the distribution of precipitation. They are also directly involved in the production of secondary pollutants and haze, which seriously endanger human life. Therefore, the study of atmospheric aerosol characteristics, especially near-ground aerosol characteristics, is particularly important.

[0003] Traditional Mie scattering lidar has achieved real-time monitoring of atmospheric aerosols, but due to the structure of the lidar itself, whether it is a coaxial structure or an off-axis structure, it is impossible to directly measure the atmospheric characteristics within the geometric factor area. To solve this problem, researchers from various countries have tried various methods, but they all have their limitations to a greater or lesser extent.

[0004] In 1979, Sasano et al. proposed the atmospheric horizontal calibration method. This method starts from the lidar equation and assumes that the atmosphere is approximately uniform when the laser propagates in the horizontal direction, and the atmospheric backscattering coefficient and the extinction coefficient are constants. Then, a far-field base point is selected and linear fitting is performed using the slope method to obtain the uniform extinction coefficient. Since this method selects a fitting point at a relatively far distance as the slope, the fitting error is continuously superimposed along the near-field direction, resulting in a large error in the near-field geometric factor. In addition, affected by multiple scattering of particles, the geometric factors corrected for different weather conditions have poor adaptability.

[0005] In 2002, Ulla Wandinger et al. proposed a method to measure geometric factors by combining vibrational Raman signals with aerosol Mie scattering signals. First, because the Raman scattering signals of nitrogen molecules in the atmosphere received are 3 to 4 orders of magnitude weaker than the Mie scattering signals and the Rayleigh scattering signals of atmospheric molecules, observations can generally only be made at night. Secondly, this method has high requirements for the optical matching of the two detection channels. Finally, this method assumes the aerosol wavelength index and also brings about large inversion errors.

[0006] Another new method that uses CCD cameras and lidar to measure geometric factors in the area has been proposed by scholars. That is, the horizontal beam image and the vertical aerosol angular scattering grayscale image are measured by a CCD camera, and the relative value of the atmospheric scattering phase function obtained from the horizontal image is used to invert the vertical extinction profile. This method requires high accuracy in determining the geometric position of the system and is difficult to operate. At the same time, due to the angular dependence of aerosol scattering, that is, the aerosol phase function in the geometric factor area varies, especially in the range of 90° to 180°, it is difficult to determine accurately, which further limits the application of the CCD measurement method. Summary of the invention

[0007] To solve the above technical problems, the present invention proposes a method for detecting the atmospheric characteristics of the geometric factor region using a scanning lidar. The specific technical solution is as follows:

[0008] S1. In the measurement inversion of the scanning lidar for measuring the atmospheric characteristics of the geometric factor region, first vertically detect the lidar, and calculate the geometric factor region z from the upper part to the calibration distance z g at each height within the range c of the aerosol extinction coefficient;

[0009] S2. The lidar is scanned obliquely in a fan shape from the vertical direction to the horizontal direction at a certain zenith angle. Let the height of the geometric factor region be z g , the number of scanning groups be n, where n ∈ [1, 2, 3... N], and the height resolution be dr. Then the sizes of the zenith angles of each group are:

[0010] a(n) = acos((z g - n·dr) / z g ) (5)

[0011] Set the calibration distance as z c , and thus determine the calibration heights corresponding to different zenith angle scanning groups:

[0012] z(n) = z c ·cos[a(n)] (6)

[0013] S3. Assume that the entire atmosphere is horizontally uniform during the fan-shaped scanning process, and the aerosol extinction coefficient at the same height is the same as the molecular extinction coefficient; that is, when n = 1, the aerosol extinction coefficient α a and the molecular extinction coefficient α m at P1 are the same as the aerosol extinction coefficient and the molecular extinction coefficient at A1, P2 is the same as A2, and so on, P n is the same as A n ; define the aerosol backscatter ratio R b = (S2·α a ) / (S1·α m ) + 1, where S1 and S2 are the aerosol extinction backscatter ratio and the molecular extinction backscatter ratio respectively, both of which are constants. Therefore, it can be known that the backscatter ratio Rb at the same horizontal height is also the same; assume that the calibration heights of the 1st to mth scanning groups are above the height z g of the geometric factor region, and the calibration heights of the (m + 1)th to nth scanning groups are below the height z g of the geometric factor region; the calibrated backscatter ratios R bIt can be calculated based on the aerosol extinction coefficient at the corresponding calibrated height measured in S1. Substitute the obtained R1~R m into the Fernald equation to calculate A1~A m of the aerosol extinction coefficient; the calibrated backscattering ratio R m+1 of the (m + 1)-th group is calculated from the extinction coefficient of the m-th scanning group at this height. According to the obtained value of R m+1 and the Fernald equation, calculate the aerosol extinction coefficient of A m+1 ; the calibrated backscattering ratio R m+2 of the (m + 2)-th group is calculated from the extinction coefficient at the corresponding height measured in the (m + 1)-th group. According to the obtained value of R m+2 and the Fernald equation, calculate the aerosol extinction coefficient of A m+2 ; and so on until the aerosol extinction coefficient at A n is calculated. According to the above steps, obtain the aerosol extinction coefficients from A1 to A n , and then the aerosol extinction coefficient α g within the geometric factor region z a can be obtained.

[0014] The advantages of the present invention are as follows:

[0015] (1) Compared with the method in the background art, this method does not require the phase function of the aerosol, effectively avoiding the measurement error caused by calculating the phase function.

[0016] (2) This method has low dependence on time and space and can be used in cloudless weather during the day and at night. Compared with the method in the background art, it is more convenient, faster, and more efficient.

[0017] (3) The geometric factor corrected by this method has high adaptability and can be jointly detected with other lidars to make up for the deficiency in the measurement within the geometric factor region. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the schematic diagram of detecting by using a scanning lidar;

[0019] Figure 2 is the vertical aerosol extinction coefficient profile;

[0020] Figure 3 is the aerosol extinction profiles at different angles;

[0021] Fig. 4(a) shows the relative error distribution of the first 35 groups on a sunny day;

[0022] Fig. 4(b) shows the relative error distribution of the first 26 groups on a sunny day;

[0023] Fig. 5(a) shows the relative error distribution of the first 35 groups on a foggy day;

[0024] Figure 5(b) Statistical relative error distribution for the first 26 groups in foggy weather;

[0025] Figure 6(a) Measurement error when the boundary layer height is 0.7 km;

[0026] Figure 6(b) Measurement error when the boundary layer height is 1.2 km;

[0027] Figure 6(c) Measurement error when the boundary layer height is 1.7 km;

[0028] Figure 7(a) Statistical relative error distribution for the last 4 groups on sunny days;

[0029] Figure 7(b) Statistical relative error distribution for the last 4 groups on foggy days;

[0030] Figure 8(a) Relative error distribution on sunny days;

[0031] Figure 8(b) Relative error distribution on foggy days;

[0032] Figure 9(a) Variation of relative error with the number of zenith angle groups when the boundary layer height is 0.5 km;

[0033] Figure 9(b) Variation of relative error with the number of zenith angle groups when the boundary layer height is 1.2 km;

[0034] Figure 9(c) Variation of relative error with the number of zenith angle groups when the boundary layer height is 1.7 km;

[0035] Figure 10(a) Relative error caused by systematic error when the boundary layer height is 1.7 km and the extinction coefficient is 0.15 km -1 ;

[0036] Figure 10(b) Relative error caused by systematic error when the boundary layer height is 1.7 km and the extinction coefficient is 0.5 km -1 ;

[0037] Figure 10(c) Relative error caused by systematic error when the boundary layer height is 1.7 km and the extinction coefficient is 2 km -1 ;

[0038] Figure 10(d) Relative error caused by systematic error when the boundary layer height is 1.2 km and the extinction coefficient is 2 km -1 ;

[0039] Figure 10(e) Relative error caused by systematic error when the boundary layer height is 0.7 km and the extinction coefficient is 2 km -1 ; Detailed implementation manners

[0040] A method for detecting the atmospheric characteristics of a geometric factor region by using a scanning lidar, comprising the following steps:

[0041] S1. In the measurement inversion of a scanning lidar for measuring the atmospheric properties in the geometric factor region, first, the lidar is vertically detected, and the geometric factor region z is calculated according to the Fernald method from the calibration distance z g above to the calibration distance z c to the aerosol extinction coefficients at each height within the range.

[0042] The steps for calculating the atmospheric aerosol backscatter coefficient in step S1 are as follows:

[0043] S11. Determine the received echo signal of the large climate scattering:

[0044]

[0045] where P(z) is the echo power (W) received at distance z in the lidar equation, C is the system constant (W·km 3 ·sr), β a (z) and β m (z) are the aerosol backscatter coefficient and the molecular backscatter coefficient at distance z (km -1 ·sr -1 ), α a (z′) and α m (z′) are the aerosol extinction coefficient and the molecular extinction coefficient at distance z (km -1 );

[0046] S12. Define the aerosol backscatter ratio at the calibration distance:

[0047]

[0048] S13. Substitute the backscatter ratio into equation (1) to calculate the atmospheric aerosol backscatter coefficient:

[0049]

[0050] The atmospheric aerosol extinction coefficient is:

[0051] α a (z) = S1·β a (z) (4)

[0052] where X(z) = P(z)z 2 is the distance squared signal, S1 is the aerosol extinction backscatter ratio, whose value is affected by the aerosol size spectrum and refractive index, usually between 10 sr and 100 sr. In the Fernald method, it is assumed that this value is a constant independent of height. During the tropospheric and stratospheric background periods, S1 = 50 can be taken. S2 = α m (z) / β m(z) is the molecular extinction backscattering ratio, which is taken as 8π / 3 in this scheme, and β m (z) is obtained by calculating according to Rayleigh scattering theory.

[0053] As Figure 1 shown, let the height of the geometric factor area be z g , the number of scanning groups is n, where n ∈ [1, 2, 3... N], and the height resolution is dr. Then the zenith angle sizes of each group are:

[0054] a(n) = acos((z g - n·dr) / z g ) (5)

[0055] To make the spatial resolution distribution as uniform as possible under the condition of meeting the mechanical accuracy, several groups of measured zenith angles and their corresponding calibration heights are selected when the height resolution is approximately the set value, and the calibration distance z c is determined. According to the calibration distance, the calibration heights corresponding to different zenith angle sizes are determined:

[0056] z(n) = z c ·cos[a(n)] (6)

[0057] In this embodiment, 39 groups of measured zenith angles and their corresponding vertical heights are selected when the height resolution is approximately 15m, as shown in Table 1, where the calibration distance z c is 5.0175km.

[0058] Table 1 Scanning zenith angles and corresponding calibration heights

[0059]

[0060]

[0061] Assume that the entire atmosphere is horizontally uniform during the fan-shaped scanning process, and the aerosol extinction coefficient is the same as the molecular extinction coefficient at the same height. That is, when n = 1, the aerosol extinction coefficient α a and the molecular extinction coefficient α m at P1 are the same as the aerosol extinction coefficient and the molecular extinction coefficient at A1, the same at P2 and A2, and so on, the same at P n and A n . In addition, define the aerosol backscattering ratio R b = (S2·α a ) / (S1·α m ) + 1, where S1 and S2 are the aerosol extinction backscattering ratio and the molecular extinction backscattering ratio respectively, and both are constants. Therefore, it can be known that the backscattering ratio R b at the same horizontal height is also the same.

[0062] Assume that the calibration heights of the 1st to mth scanning groups are above the height z of the geometric factor region g and the calibration heights of the (m + 1)th to nth scanning groups are below the height z of the geometric factor region. The calibrated backscattering ratios R corresponding to each of the 1st to mth groups g can be calculated based on the aerosol extinction coefficients at the corresponding calibration heights measured in S1. Substituting the obtained R1 to R b into the Fernald equation can calculate the aerosol extinction coefficients A1 to A m ; Since the calibration height of the (m + 1)th scanning group is already within the geometric factor region z m , its corresponding R g cannot be obtained from S1. Due to the fact that R b is the same at the same height, the calibrated backscattering ratio R of the (m + 1)th group b can be calculated from the extinction coefficient of the mth scanning group at this height. Based on the obtained value of R m+1 and the Fernald equation, the aerosol extinction coefficient of A m+1 can be calculated. The calibrated backscattering ratio R of the (m + 2)th group m+1 can be calculated from the extinction coefficient at the corresponding height measured from the (m + 1)th group. Based on the obtained value of R m+2 and the Fernald equation, the aerosol extinction coefficient of A m+2 can be calculated. And so on, until the aerosol extinction coefficient at A m+2 is calculated. According to the above steps, obtaining the aerosol extinction coefficients at A1 to A n , the aerosol extinction coefficient α n within the geometric factor region z g can be obtained. a

[0063] The above scheme is verified by simulation:

[0064] First, using the simulated aerosol backscattering profile as the true value, set the calibration height to 5.0175 km, the height resolution to 15 m, the boundary layer height to 1.7 km, the height of the geometric factor region to 600 m, the aerosol extinction coefficient above the boundary layer to 0.005 km -1 , and the aerosol extinction coefficient below the boundary layer to 0.15 km -1 . As shown in Figure 2 , the solid line and the dashed line respectively represent the aerosol extinction profiles before and after substituting the geometric factor.

[0065] Using the vertical simulation signal and a fixed scanning angle, the aerosol extinction coefficient profiles at different angles can be retrieved. Select the number of scanning groups as 39, and its extinction coefficient profile is as shown in Figure 3As shown in the figure, by assigning the extinction coefficient of each group of contour lines at their corresponding heights to the points corresponding to each height within the geometric factor region, the atmospheric extinction characteristics at each height within the geometric factor region can be obtained.

[0066] Error Analysis

[0067] There are three main error sources in this measurement method, namely, the measurement result error caused by the non-uniform distribution of the atmosphere at the same height in the atmospheric stratification structure model, and the measurement result errors caused by the random error and systematic error of the scanning angle.

[0068] According to the atmospheric stratification structure model, assuming that there is no significant atmospheric movement within the measured space and time range, the atmosphere is uniformly stratified with height, that is, the atmospheric backscattering ratio R at the same height b is the same. For the measurement groups (the first 35 groups) above the geometric factor region in height, assuming that the horizontal distribution of the atmosphere is non-uniform, the R at this height b has a ±10% error compared with the R of the vertical profile. b

[0069] When the boundary layer height is 1.7 km, the error analysis is carried out for two weather conditions, namely sunny days (the atmospheric extinction coefficient below the boundary layer is 0.15 km -1 ) and foggy days (the atmospheric extinction coefficient below the boundary layer is 2 km -1 ), that is Figure 1 the relative error of the aerosol extinction coefficient at height A n and P n , where n ∈ [1, 2, 3... N]. The relative error distributions of the first 35 groups and the first 26 groups are respectively as shown in Figure 4(a) 、 5(b) .

[0070] As shown in Fig. 4(a), it is the relative error distribution of the first 35 groups on sunny days. To facilitate the observation of the relative error distribution of the first 26 groups, it is magnified to obtain Fig. 4(b). It can be found from Fig. 4(a) and Fig. 4(b) that the error of R b caused by the horizontal inhomogeneity of the atmosphere and the measurement error it causes are approximately linearly related. Above the boundary layer (the first 26 group of profiles), as the scanning zenith angle increases, the relative error gradually decreases, and its range is between ±0.57% and ±0.64%. When first reaching below the boundary layer (the 27th to 35th group of profiles), due to the sudden change in the magnitude of R b , there will also be a relatively large sudden change in the error of the 27th group of profiles compared with the error of the 26th group of profiles, and the error increases as the scanning zenith angle increases, and its range is between ±5.4% and ±7.9%.

[0071] In Figures 5(a) and 5(b), the variation law of the relative error is consistent with that in Figures 4(a) and 4(b). However, the relative error range of the first 26 groups is between ±0.0013% and ±0.006%, while the relative error range of the 27th to 35th groups is between ±0.024% and ±0.93%.

[0072] Because the error of R b is approximately linearly related to the relative measurement error within ±10% and is symmetric about the zero point, R b is selected as the fixed error of 10% to further study the influence of the boundary layer height on the measurement results.

[0073] As Figure 6(a)-6(c) shown, Figures 6(a), 6(b), and 6(c) respectively represent the schematic diagrams of the measurement errors at different extinction coefficients when the boundary layer heights are 0.7 km, 1.2 km, and 1.7 km. The influence of the boundary layer height on the measurement results is reflected in the sharp increase in the errors of two groups of scanning profiles near the boundary layer height due to the mutation of R b . And the "mutation point" gradually moves forward as the boundary layer height increases, while the overall error range does not change. In addition, as the atmospheric extinction coefficient increases, the amplitude of the mutation decreases and the relative error also decreases.

[0074] The relative error below the height of the geometric factor region

[0075] For the measurement groups (groups 36 to 39) with heights below the geometric factor region, assume that there is an error of ±10% between the atmospheric backscattering ratio R b of the 35th group and the R b of the vertical extinction profile at this height. With a step size of 5%, there are a total of 5 groups of data. The 36th group adds another ±10% error on the basis of the 35th group with the step size unchanged, resulting in a total of 25 groups of data. And so on, the 39th group has a total of 3125 groups of data. Figures 7(a) and 7(b) are the relative error probability distribution diagrams of groups 36 to 39 under sunny and foggy conditions.

[0076] By comparing Figures 7(a) and 7(b), it can be found that under the same zenith angle, the overall relative measurement error in foggy days is smaller than that in sunny days. The absolute error is smaller in foggy days than in sunny days, and as the measurement zenith angle increases, the error range of the last four groups of measurement data also increases and generally follows a normal distribution. At the same time, the relative error in foggy days is also significantly better than that in sunny days, and the errors at the half-width are controlled within ±22% and ±7% respectively.

[0077] The random error of the scanning angle

[0078] The random error of the scanning angle is the deviation between the actual angle and the theoretical angle due to the instability of the component fit during the scanning process of the scanning head, as well as component deformation, friction, etc. Currently, the angular accuracy of mainstream scanning lidars can basically be controlled between 0.1° and 0.5°. Therefore, the random error of the angular accuracy is selected as ±0.2°, and the random errors of 39 groups of scanning zenith angles are analyzed.

[0079] As Figure 8(a) , 8(b) shown, in the two models of sunny days and foggy days, the measurement relative error and the random error of the zenith angle are approximately linearly related within the range of ±0.2°, and as the scanning zenith angle increases, the range of the measurement relative error also increases. In the sunny day model, the relative error range is about ±0.8%, and in the foggy day model, the relative error range is about ±5.5%. In addition, due to the uncertainty of the random error of the scanning angle in the measurement, the actual error is smaller than the above results.

[0080] To further study the influence of the boundary layer height on the measurement results, the random error of the zenith angle is fixed at -0.2°, and the boundary layer heights are selected as 0.7 km, 1.2 km, and 1.7 km, and the bottom extinction coefficients are 0.15 km -1 , 0.25 km -1 , 0.5 km -1 , 1 km -1 and 2 km -1 for a control experiment.

[0081] As Figure 9(a)-9(c) shown, as the scanning zenith angle increases, the overall measurement relative error also increases, but when the measurement group first reaches below the boundary layer, the relative error will have a small decrease compared to the previous group, and the drop point will gradually move forward as the boundary layer height increases, and the downward trend will also gradually become less obvious as the extinction coefficient increases.

[0082] Systematic error of the scanning angle

[0083] The systematic error of the scanning angle is a fixed deviation between the actual measured angle and the theoretical value because the scanning radar is not horizontally calibrated or the calibration is incorrect. The systematic error of the scanning angle is selected as ±5°.

[0084] Figure 10(a)-10(e) is a schematic diagram of the measurement relative error caused by the systematic error of the scanning angle under different boundary layer heights and different extinction coefficients. First, due to the existence of the systematic error, the scanning groups near the boundary layer will have a "mutation" error. Taking Figure 10(a) as an example, the error curves of the 24th to 29th groups near the boundary layer have a "mutation" error compared to other groups. When the boundary layer height remains unchanged and the bottom extinction coefficient is changed, that is, compared with Figure 10(a)-10(c)It can be found that the position of the "mutation point" does not change, but the amplitude of the error change at this point decreases with the increase of the extinction coefficient. At the same time, the error range of each scanning group also increases with the increase of the extinction coefficient.

[0085] Secondly, when the bottom extinction coefficient remains unchanged, the size of the boundary layer height is changed, that is, compared with Figure 10(c)-Figure 10(e) It can be found that with the decrease of the boundary layer height, the position of the "mutation point" gradually moves backward, from the 24th to 29th groups at 1.7 km to the 31st to 37th groups at 0.7 km. And during this process, except for the measurement groups with "mutation", the error ranges of each group basically do not change.

[0086] Finally, from the perspective of the overall error, the higher the extinction coefficient, the greater the measurement error; with the increase of the scanning zenith angle, the measurement error caused also increases; and the overall error range when the measurement zenith angle is small is larger than when it is large. Compared with the uneven horizontal distribution of the atmosphere and the random error of the scanning angle, the systematic error of the scanning angle has a greater impact on the experimental accuracy and should be paid special attention to in subsequent research.

[0087] In summary, it can be obtained that:

[0088] Aiming at the problem that the traditional Mie scattering lidar cannot detect the atmospheric extinction characteristics in the geometric factor region, a method for detecting the atmospheric extinction characteristics in the geometric factor region by using a scanning lidar based on the atmospheric stratification structure model is proposed, and simulation inversion and error analysis are carried out. The experimental results show that: this method is completely feasible in principle, and the influence of different weather conditions on the measurement error is also different. This method provides a new idea for the research of atmospheric characteristics in the geometric factor region. In the follow-up, a simulation model closer to the real atmosphere will be used to further explore the influence of various factors on the measurement error, and the applicability of this method will be further demonstrated through field tests.

[0089] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting the atmospheric characteristics of a geometric factor region using a scanning lidar, characterized in that, Including the following steps: S1. In the measurement inversion of a scanning lidar for measuring the atmospheric properties in the geometric factor region, first vertically detect the lidar and calculate the aerosol extinction coefficients at each height within the range from the height z above the geometric factor region to the calibration distance z according to the Fernald method. g above to the calibration distance z c range. S2. The radar is scanned in a fan-shaped pattern by tilting it from the vertical direction to the horizontal direction at a certain zenith angle step by step. Let the height of the geometric factor area be z g , the number of scan groups is n, where n ∈ [1, 2, 3... N], and the height resolution is dr. Then the zenith angle of each group is as follows: a(n) = acos((z g - n·dr) / z g ) (5) Set the calibration distance as z c , and thus determine the calibration heights corresponding to different zenith angle scan groups: z(n) = z c ·cos[a(n)] (6) S3. Assume that the entire atmosphere is horizontally uniform during the fan-beam scanning process, and the aerosol extinction coefficient is the same as the molecular extinction coefficient at the same altitude; that is, when n = 1, the aerosol extinction coefficient α a and the molecular extinction coefficient α m at P1 are both the same as the aerosol extinction coefficient and the molecular extinction coefficient at A1, the same as those at A2 at P2, and so on, the same as those at A n at P n ; define the aerosol backscatter ratio R b =(S2·α a ) / (S1·α m ) + 1, where S1 and S2 are the aerosol extinction backscatter ratio and the molecular extinction backscatter ratio respectively, both of which are constants. Therefore, it can be known that the backscatter ratio Rb at the same horizontal altitude is also the same; assume that the calibration altitudes of the 1st to mth scanning groups are above the geometric factor region altitude z g , and the calibration altitudes of the (m + 1)th to nth scanning groups are below the geometric factor region altitude z g ; the calibrated backscatter ratio R b corresponding to each of the 1st to mth groups is calculated based on the aerosol extinction coefficient measured at the corresponding calibration altitude in S1. Substitute the obtained R1 to R m into the Fernald equation to calculate the aerosol extinction coefficients of A1 to A m ; the calibrated backscatter ratio R m+1 of the (m + 1)th group is calculated from the extinction coefficient of the mth scanning group at this altitude. According to the obtained value of R m+1 and the Fernald equation, calculate the aerosol extinction coefficient of A m+1 ; the calibrated backscatter ratio R m+2 of the (m + 2)th group is calculated from the extinction coefficient measured at the corresponding altitude of the (m + 1)th group. According to the obtained value of R m+2 and the Fernald equation, calculate the aerosol extinction coefficient of A m+2 ; and so on, until the aerosol extinction coefficient at A n is calculated; according to the above steps, obtain the aerosol extinction coefficients from A1 to A n , and then the aerosol extinction coefficient α g within the geometric factor region z a can be obtained.

2. The method for detecting the atmospheric characteristics of a geometric factor region using a scanning lidar according to claim 1, characterized in that, The steps for calculating the atmospheric aerosol extinction coefficient in step S1 are as follows: S11. Determine the received atmospheric backscattered echo signal: where \(P(z)\) is the received echo power (W) at distance \(z\) in the lidar equation, \(C\) is the system constant (W·km 3 ·sr), \(\beta\) a (z) and \(\beta\) m (z) are the aerosol backscattering coefficient and the molecular backscattering coefficient at distance \(z\) (km -1 ·sr -1 ), respectively, \(\alpha\) a (z') and \(\alpha\) m (z') are the aerosol extinction coefficient and the molecular extinction coefficient at distance \(z\) (km -1 ), respectively; S12. Define the aerosol backscattering ratio at the calibration distance: S13. Substitute the aerosol backscattering ratio into equation (1) to calculate the atmospheric aerosol backscattering coefficient: where X(z) = P(z)z 2 is the squared distance signal, S1 = α a (z) / β a (z) and S2 = α m (z) / β m (z) are the aerosol and molecular extinction backscattering ratios respectively; The atmospheric aerosol extinction coefficient is: α a ψ(z) = S1·β a ψ(z) (4).

3. The method for detecting the atmospheric characteristics of the geometric factor region using a scanning lidar according to claim 2, wherein S1 = 50, S2 = 8π / 3, β m (z) is obtained by calculating according to the Rayleigh scattering theory.

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