Near-surface blind-zone-free atmospheric temperature detection Raman lidar system and method

Abstract

The Raman lidar system for near-surface blind-zone-free atmospheric temperature detection disclosed by the present invention includes a laser emission subsystem, a lateral telescope receiving and spectrometer subsystem, and a data acquisition and inversion subsystem; the laser emission subsystem can emit laser with a specific wavelength and vertically shoot it into the atmosphere; the lateral telescope group receiving and spectrometer subsystem is used to receive, separate and extract, and detect and extract the pure rotational Raman scattering echo signals of the high and low quantum number channels of the lateral scattering relative to the laser emission spectrum; the data acquisition and inversion subsystem collects the lateral pure rotational Raman scattering echo signals with high and low quantum channels relative to the laser emission spectrum and realizes the data inversion of the atmospheric temperature, and the data acquisition and inversion subsystem is connected to the lateral telescope group receiving and spectrometer subsystem. A method for near-surface blind-zone-free temperature detection by Raman lidar is also disclosed.

Description

Technical Field

[0001] The present invention belongs to the technical field of atmospheric temperature detection, and particularly relates to a Raman lidar system for detecting the atmospheric temperature in the near-surface layer without blind areas, and also relates to a method for detecting the atmospheric temperature in the near-surface layer without blind areas by using a Raman lidar. Background Art

[0002] Atmospheric temperature is an important meteorological and atmospheric physical parameter. Various natural weather phenomena and atmospheric state changes such as physical and chemical processes occurring in the atmosphere, weather forecasting, and environmental detection can be studied through the atmospheric temperature parameter. In particular, the atmospheric temperature at the bottom and middle of the troposphere is closely related to human life. The change of atmospheric temperature also indirectly reflects the change of ozone concentration, resulting in frequent extreme weather events around the world under the trend of global warming in recent years. Therefore, it is of great significance to carry out real-time detection of atmospheric temperature with high spatio-temporal resolution and to deeply study the correlation between atmospheric science, global warming, and extreme weather.

[0003] The pure rotational Raman lidar is a method for measuring the atmospheric temperature profile by using lidar technology. However, due to the existence of blind areas and transition zones caused by the geometric overlap factor, the traditional backward pure rotational Raman scattering lidar cannot detect the low-layer atmospheric temperature information when measuring the atmospheric temperature. Therefore, the implementation of the backward pure rotational Raman scattering lidar for detecting the temperature of the whole layer of the atmosphere, especially for detecting the low-layer atmospheric temperature, has certain limitations. In order to achieve blind area-free detection, the lidar receiving system is redesigned, and the lateral pure rotational Raman scattering lidar technology is adopted to realize the detection of the low-layer atmospheric temperature. Summary of the Invention

[0004] The first object of the present invention is to provide a Raman lidar system for detecting the atmospheric temperature in the near-surface layer without blind areas, so as to realize the detection of the near-surface atmospheric temperature.

[0005] The second object of the present invention is to provide a method for detecting the atmospheric temperature in the near-surface layer without blind areas by using a Raman lidar.

[0006] The first technical solution adopted by the present invention is a Raman lidar system for detecting the atmospheric temperature in the near-surface layer without blind areas, which is characterized by comprising a laser emission subsystem, a lateral telescope receiving and spectroscopic subsystem, and a data acquisition and inversion subsystem;

[0007] The laser emission subsystem can emit laser with a specific wavelength and vertically irradiate the atmosphere;

[0008] The lateral telescope group receiving and spectroscopic subsystem is used for receiving, separating, extracting, and detecting the pure rotational Raman scattering echo signals of the high and low quantum number channels of the lateral scattering relative to the laser emission spectrum;

[0009] The data acquisition and inversion subsystem collects the lateral pure rotational Raman scattering echo signals with high and low quantum channels relative to the laser emission spectrum, and performs data inversion of the atmospheric temperature. The data acquisition and inversion subsystem is connected to the lateral telescope receiving and photon-splitting subsystem.

[0010] The features of the present invention also lie in that

[0011] The laser emission subsystem includes a laser, a laser beam expander, and a 45° total reflection mirror; the laser, the laser beam expander, and the 45° total reflection mirror are placed on the same horizontal plane. The horizontal laser emitted by the laser is vertically emitted into the atmosphere after passing through the laser beam expander and the 45° total reflection mirror; the 45° total reflection mirror is an electrically adjustable 45° total reflection mirror.

[0012] The laser is a high-energy pulsed laser or a high-power continuous laser.

[0013] The lateral telescope receiving and photon-splitting subsystem includes an electrically adjustable pitching bracket. Two lateral telescope groups are installed on the electrically adjustable pitching bracket. Each lateral telescope group includes two lateral telescopes. After the light outlet of one lateral telescope, a first lens a, a first filter a, a second filter a, a second lens a, and a PMT photodetector a are sequentially installed; after the light outlet of the other lateral telescope, a first lens b, a first filter b, a second filter b, a second lens b, and a PMT photodetector b are sequentially installed; the PMT photodetector a records the lateral pure rotational Raman scattering echo signals of the lateral scattering high quantum number channel relative to the laser emission spectrum, and the PMT photodetector b records the lateral pure rotational Raman scattering echo signals of the lateral scattering low quantum number channel relative to the laser emission spectrum.

[0014] The central wavelengths of the high quantum channels of the first filter a and the second filter a are: having the largest negative temperature change rate of the Raman signal relative to the laser emission wavelength; the specific parameters are: bandwidth: 0.2 - 0.3 nm, suppression rate: OD is greater than or equal to 6, working angle: 5° - 7°;

[0015] The central wavelengths of the low quantum channels of the first filter b and the second filter b are: having the largest positive temperature change rate of the Raman signal relative to the laser emission wavelength; the specific parameters are: bandwidth: 0.2 - 0.3 nm, suppression rate: OD is greater than or equal to 6, working angle: 5° - 7°.

[0016] The second technical solution adopted by the present invention is a Raman lidar method for detecting the atmospheric temperature without blind areas in the near-surface layer, which is specifically implemented according to the following steps:

[0017] Step 1, Initialize the lateral pure rotational Raman scattering lidar;

[0018] Step 2: The data received by the lateral telescope group from the pitch rotation platform are DC level signals; the lateral Raman scattering echo signals received at each rotation angle within the pitch angle θ range of 0° to 90° by the telescope are fitted for all the collected level signals to obtain the lateral Raman scattering echo signals;

[0019] Step 3: Optimization of the calibration function for the atmospheric temperature detection by the lateral pure rotational Raman lidar;

[0020] Step 4: Obtaining the low-layer atmospheric temperature profile through the inversion algorithm of the lateral pure rotational Raman scattering atmospheric temperature detection lidar;

[0021] Step 5: Calculating the uncertainty of the lateral pure rotational Raman atmospheric temperature;

[0022] Step 6: Stitching the low-layer atmospheric temperature profile obtained by the inversion of the lateral pure rotational Raman scattering lidar and the high-layer atmospheric temperature profile obtained by the inversion of the backward pure rotational Raman scattering lidar to obtain the whole-layer atmospheric temperature profile for blind-free detection.

[0023] The feature of the present invention further lies in that,

[0024] Step 3 is specifically implemented according to the following steps:

[0025] Step 3.1: Let y = lnQ(z, T) and x = 1 / T, and the fitting function can be expressed as

[0026] Step 3.2: Add the term x = 1 / T, then the calibration function is: The expression of temperature T CF1 is:

[0027]

[0028] In the formula: is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, Q(T, z) is the ratio of the lateral pure rotational Raman scattering signals, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively, Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, is the atmospheric transmittance correction function, T is the temperature, and a, b, c are undetermined coefficients;

[0029] Step 3.3: Add the term y = lnQ(z, T), then the calibration function is: The expression of temperature T CF2The expression is:

[0030]

[0031] In the formula: is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, Q(T,z) is the ratio of the lateral pure rotational Raman scattering signals, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively, is the atmospheric transmittance correction function, T is the temperature, Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral low and high quantum number channels, and a, b, and c are undetermined coefficients.

[0032] Step 4 is specifically implemented according to the following steps:

[0033] Step 4.1: From the geometric structure of the lateral Raman lidar, the pure rotational Raman scattering echo signals of the lateral low and high quantum channels and The formulas are as follows:

[0034]

[0035]

[0036] In the formula, and are the signal powers of the lateral pure rotational Raman scattering low and high quantum channels respectively, E0 is the power of the high-energy pulsed laser or the high-power continuous laser, z is the detection altitude, θ is the scattering angle, J is the rotational quantum number, A is the receiving area of the telescope, K is the system constant, D is the horizontal distance between the lateral telescope and the vertical laser beam, T is the temperature, N(z) is the atmospheric molecular number density, represents the volume ratio of nitrogen and oxygen molecules in the low quantum channel in the atmosphere, represents the volume ratio of nitrogen and oxygen molecules in the high quantum channel in the atmosphere, σ i (J,T) represents the backscattering cross section of the pure rotational Raman lines of nitrogen and oxygen molecules, f L (θ) is the pure rotational Raman scattering phase function of the low quantum channel, f H (θ) is the pure rotational Raman scattering phase function of the high quantum channel, λ0 is the laser emission wavelength, T z (z,λ0) is the on-way atmospheric transmittance, is the slant-path atmospheric transmittance of the low quantum channel, is the atmospheric transmittance of the high quantum channel, dθ is the field of view angle of the lateral telescope, and The scattering wavelengths of the low quantum channel and the high quantum channel, respectively;

[0037] Step 4.2: Extract a single spectral line in the high and low quantum number channels respectively, and the ratio Q(T,z) of the lateral pure rotational Raman scattering signals is expressed as:

[0038]

[0039] In the formula, and are the Raman scattering signal powers of the lateral high and low quantum channels respectively. σ(J L ,T) and σ(J H ,T) are the backscattering cross-sections of the pure rotational Raman spectra of the low quantum channel and the high quantum channel. Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels. is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, T is the temperature. and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively. A and B are the calibration coefficients derived from the theoretical definitions.

[0040] Step 4.3: The temperature T can be obtained and is expressed as:

[0041]

[0042] In the formula: Q(T,z) is the ratio of the lateral pure rotational Raman scattering signals. is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle. and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively. Δf r (θ) is the ratio of the phase functions of the lateral pure rotational Raman scattering high and low quantum number channels. T is the temperature. A and B are the calibration coefficients derived from the theoretical definitions.

[0043] Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels and is expressed as:

[0044]

[0045] In the formula, f L (θ) is the pure rotational Raman scattering phase function of the low quantum channel. f H (θ) is the pure rotational Raman scattering phase function of the high quantum channel. β L (θ,λ L ) and β H (θ,λ Hare the side-scattering coefficients of the low and high quantum channels, respectively, β L (λ L ) and β H (λ H ) are the backscattering coefficients of the low and high quantum channels, respectively;

[0046] is the atmospheric transmittance correction function, expressed as:

[0047]

[0048] In the formula, is the slant-path atmospheric transmittance of the low quantum channel, is the atmospheric transmittance of the high quantum channel, θ is the scattering angle, is the extinction coefficient of the low quantum channel, is the extinction coefficient of the high quantum channel, z is the detection altitude;

[0049] In step 5, the temperature measurement uncertainty ΔT of the side pure rotational Raman can be expressed as:

[0050]

[0051] In the formula: is the ratio of the Raman high and low quantum number signal intensities of the side pure rotational Raman, Q1 and Q2 are the ratios of the signal intensities of the high and low quantum number channels of the side pure rotational Raman scattering at different temperature pairs, and are the signal powers of the high and low quantum channels of the side pure rotational Raman scattering, respectively, and T1 and T2 are the temperatures calculated for the first and second times.

[0052] Step 6 is specifically implemented according to the following steps:

[0053] Method 1: Use the phase function to correct the echo signals of the high and low quantum channels of the side pure rotational Raman scattering respectively, convert them into the echo signals of the high and low quantum channels of the back pure rotational Raman scattering, and then invert the low-level and high-level data to obtain the normalized atmospheric temperature profile;

[0054] Or,

[0055] Method 2: Perform splicing in the range of scattering angles from 178° to 180°. At this time, f L (θ)≈1, f H (θ)≈1. At this time, the lidar equations of the side pure rotational Raman scattering and the back pure rotational Raman scattering only differ by a constant, and the two lidar data can be spliced to obtain the whole-layer atmospheric temperature profile.

[0056] The beneficial effects of the present invention are:

[0057] The system of the present invention is very different from the traditional monostatic backscattering lidar. It adopts the form of bistatic side-scattering lidar, which solves the problem of accurate detection of the temperature of the lower atmosphere. The Raman lidar system for non-blind-zone atmospheric temperature detection consists of three major parts: a laser emission subsystem, a side telescope group receiving and photon-splitting subsystem that can rotate in the pitch direction from 0 to 90°, and a data acquisition and inversion subsystem. Among them, the laser emission subsystem can emit pulsed laser or continuous laser with a specified wavelength towards the atmosphere, and scatter with atmospheric particulate matter and atmospheric molecules; the side telescope group receiving and photon-splitting subsystem is used to receive the side pure rotational Raman scattering echo signals of high and low quantum channels; the data acquisition and inversion subsystem is used for data acquisition and data inversion of the atmospheric echo signals to obtain the temperature information of the lower atmosphere. The range resolution dz of the non-blind-zone side Raman scattering lidar is the length of the laser beam received corresponding to the receiving field of view dθ of the telescope at the pitch angle θ. The atmospheric temperature profile of the side Raman scattering lidar can be realized by continuously rotating the pitch angle of the telescope receiving subsystem and recording the side pure rotational Raman scattering echo signals of high and low quantum channels at each angle θ. Since each pitch angle corresponds to a height information, two Raman lidar profile equations for high and low quantum channels can be formed to calculate and obtain the atmospheric temperature profile of the near-surface layer.

[0058] The method of the present invention adopts the detection method of bistatic side Raman scattering lidar with separate transceiver, and designs a Raman lidar system for non-blind-zone atmospheric temperature detection in the near-surface layer to achieve accurate detection of the atmospheric temperature in the near-surface layer. Under the condition that a pulsed laser is used in the laser emission unit, the atmospheric temperature detection system of the back Raman scattering lidar can be designed and built at the same time. The combined use of the non-blind-zone side Raman scattering lidar system and the back Raman scattering lidar system can realize the fine detection of the temperature from the near surface to the upper atmosphere, providing new laser remote sensing technologies and new methods for climate and environmental research. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a schematic structural diagram of the Raman lidar system for non-blind-zone atmospheric temperature detection in the near-surface layer according to the present invention;

[0060] Figure 2 It is a spectral distribution diagram of the side pure rotational Raman scattering lidar atmospheric echo signal received according to the present invention;

[0061] Figure 3 It is a schematic diagram of the calculation model of the field of view angle and range resolution of the side-scattering lidar in the method of the present invention;

[0062] Figure 4 It is a schematic structural diagram of the back and side whole-layer atmospheric temperature lidar detection system;

[0063] Figure 5 This is a flowchart of the method of the present invention.

[0064] In the figure, 1. laser, 2. laser beam expander, 3. 45° total reflection mirror, 4. backward telescope, 5. lateral telescope group, 6. first lens a, 7. first filter a, 8. second filter a, 9. second lens a, 10. PMT photodetector a, 11. electrically adjustable pitching bracket, 12. first data acquisition system, 13. prism, 14. backward pure rotational Raman scattering atmospheric temperature detection lidar spectroscopy system, 15. second data acquisition system, 16. first lens b, 17. first filter b, 18. second filter b, 19. second lens b, 20. PMT photodetector b. Specific embodiments

[0065] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0066] The present invention provides a Raman lidar system for detecting the atmospheric temperature without blind areas in the near-surface layer, as Figure 1-2 shown, including a laser emission subsystem, a lateral telescope receiving and splitting subsystem, and a data acquisition and inversion subsystem;

[0067] The laser emission subsystem can emit laser with a specific wavelength and vertically shoot it into the atmosphere;

[0068] The lateral telescope group receiving and splitting subsystem is used to receive, separate and extract, and detect and extract the pure rotational Raman scattering echo signals of the high and low quantum number channels of the lateral scattering relative to the laser emission spectrum;

[0069] The data acquisition and inversion subsystem, namely the first data acquisition system 12, acquires the lateral pure rotational Raman scattering echo signals of the high and low quantum channels relative to the laser emission spectrum, and performs data inversion of the atmospheric temperature. The data acquisition and inversion subsystem is connected to the lateral telescope receiving and splitting subsystem.

[0070] The laser emission subsystem includes a laser 1, a laser beam expander 2 and a 45° total reflection mirror 3; the laser 1, the laser beam expander 2 and the 45° total reflection mirror 3 are placed on the same horizontal plane. The horizontal laser emitted by the laser 1 passes through the laser beam expander 2 and the 45° total reflection mirror 3 and then vertically shoots into the atmosphere; the 45° total reflection mirror 3 is an electrically adjustable 45° total reflection mirror.

[0071] The laser 1 is a high-energy pulsed laser or a high-power continuous laser.

[0072] The lateral telescope receiving and spectrometer subsystem includes an electrically adjustable pitching bracket 11. Two lateral telescope groups 5 are installed on the electrically adjustable pitching bracket 11. The lateral telescope group 5 includes two lateral telescopes. After the light outlet of one lateral telescope, a first lens a6, a first filter a7, a second filter a8, a second lens a9, and a PMT photodetector a10 are sequentially installed; after the light outlet of the other lateral telescope, a first lens b16, a first filter b17, a second filter b18, a second lens b19, and a PMT photodetector b20 are sequentially installed; the PMT photodetector a10 records the lateral pure rotational Raman scattering echo signal of the lateral scattering high quantum number channel relative to the laser emission spectrum, and the PMT photodetector b20 records the lateral pure rotational Raman scattering echo signal of the lateral scattering low quantum number channel relative to the laser emission spectrum.

[0073] The central wavelengths of the high quantum channels of the first filter a7 and the second filter a8 are: having the largest negative temperature change rate of the Raman signal relative to the laser emission wavelength; the specific parameters are: bandwidth: 0.2 - 0.3 nm, suppression ratio: OD greater than or equal to 6, working angle: 5° - 7°;

[0074] The central wavelengths of the low quantum channels of the first filter b17 and the second filter b18 are: having the largest positive temperature change rate of the Raman signal relative to the laser emission wavelength; the specific parameters are: bandwidth: 0.2 - 0.3 nm, suppression ratio: OD greater than or equal to 6, working angle: 5° - 7°.

[0075] As Figure 4 shown, it is an example of the combination of the system of the present invention and a backscattering Raman lidar system. The backscattering Raman lidar system is composed of a backscattering telescope 4, a prism 13, a backscattering pure rotational Raman scattering atmospheric temperature detection lidar spectroscopy system 14, and a second data acquisition system 15, and can be combined with the lateral pure rotational Raman scattering lidar to achieve fine detection of the temperature from the near surface to the upper atmosphere.

[0076] The lateral telescope receiving and splitting photon subsystem and the laser emitting subsystem are placed separately. The distance between the light outlet of the lateral telescope group 5 and the 45° total reflection mirror 3 is D. It can be composed of two separate lateral telescopes. The field of view of the lateral telescope group is perpendicular to the laser beam and points to the laser beam to keep the field of view consistent. The lateral scattered light received by one lateral telescope is collimated by the first lens a6, and the lateral pure rotational Raman high quantum channel signal is separated by the first filter a7 and the second filter a8, and then converged by the second lens a9 and received by the PMT photodetector a10. The lateral scattered light received by the other lateral telescope is collimated by the first lens b16, and the lateral pure rotational Raman low quantum channel signal is separated by the first filter b17 and the second filter b18, and then converged by the second lens b19 and received by the PMT photodetector b20.

[0077] One of the lateral telescopes receives and separates the lateral pure rotational Raman scattered echo signal of the high quantum channel from the splitting photon subsystem, and the other lateral telescope receives and separates the lateral pure rotational Raman scattered echo signal of the low quantum channel from the splitting photon subsystem.

[0078] The data acquisition and inversion subsystem respectively acquires the lateral pure rotational Raman scattered echo signals of the high and low quantum channels for inverting the atmospheric temperature.

[0079] The two PMT photodetectors respectively detect the lateral pure rotational Raman scattered echo signals with high and low quantum channels relative to the laser emission spectrum.

[0080] The profile of the lateral lidar data is realized by the pitch angle rotation of the lateral telescope receiving and splitting photon subsystem.

[0081] The range resolution of the lateral lidar is unequal and is jointly determined by the spacing D of the transceiver system and the field of view angle of the lateral telescope.

[0082] The range resolution dz of the lateral lidar is the length of the laser beam received corresponding to the receiving field of view dθ of the lateral telescope at the pitch angle θ.

[0083] When the light source is a pulsed laser, it can be used as the excitation source to construct a backward pure rotational Raman scattered lidar at the same time, and a comprehensive laser remote sensing system for accurate detection of the atmospheric temperature without blind areas from the lower layer to the upper layer is constructed with the Raman lidar system for detecting the atmospheric temperature without blind areas in the near surface layer.

[0084] The present invention also provides a method for detecting the atmospheric temperature by a Raman lidar without blind areas in the near surface layer, as Figure 3 、 Figure 5 shown, and is specifically implemented according to the following steps:

[0085] Step 1, Initialize the lateral pure rotational Raman scattered lidar;

[0086] Step 2: The data received by the lateral telescope group 5 from the pitching rotation platform 11 are DC level signals; at the pitching angle θ of 0 - 90°, for the lateral Raman scattering echo signals received at any rotated angle by the telescope, fitting all the collected level signals can obtain the lateral Raman scattering echo signals;

[0087] Step 3: Optimization of the calibration function for the atmospheric temperature detection by the lateral pure rotational Raman lidar;

[0088] Step 3 is specifically implemented according to the following steps:

[0089] Step 3.1: Let y = lnQ(z, T) and x = 1 / T, and the fitting function can be expressed as

[0090] Step 3.2: Add the term x = 1 / T, then the calibration function is: The expression for the temperature T CF1 is:

[0091]

[0092] In the formula: is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, Q(T, z) is the ratio of the lateral pure rotational Raman scattering signals, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively, Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, is the atmospheric transmittance correction function, T is the temperature, and a, b, c are undetermined coefficients;

[0093] Step 3.3: Add the term y = lnQ(z, T), then the calibration function is: The expression for the temperature T CF2 is:

[0094]

[0095] In the formula: is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, Q(T, z) is the ratio of the lateral pure rotational Raman scattering signals, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively, is the atmospheric transmittance correction function, T is the temperature, Δf r(θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, and a, b, and c are undetermined coefficients.

[0096] Step 4: Obtain the low-level atmospheric temperature profile through the inversion algorithm of the lateral pure rotational Raman scattering lidar for atmospheric temperature detection;

[0097] Step 4 is specifically implemented according to the following steps:

[0098] Step 4.1: From the geometric structure of the lateral Raman scattering lidar, the pure rotational Raman scattering echo signals of the lateral high and low quantum channels can be obtained and The formulas are as follows:

[0099]

[0100]

[0101] In the formula, and are the signal powers of the lateral pure rotational Raman scattering high and low quantum channels respectively, E0 is the power of the high-energy pulsed laser or high-power continuous laser, z is the detection height, θ is the scattering angle, J is the rotational quantum number, A is the receiving area of the telescope, K is the system constant, D is the horizontal distance between the lateral telescope and the vertical laser beam, T is the temperature, N(z) is the atmospheric molecular number density, represents the volume ratio of nitrogen and oxygen molecules in the low quantum channel to the total atmospheric volume, represents the volume ratio of nitrogen and oxygen molecules in the high quantum channel to the total atmospheric volume, σ i (J,T) represents the backscattering cross-section of the pure rotational Raman spectrum of nitrogen and oxygen molecules, f L (θ) is the pure rotational Raman scattering phase function of the low quantum channel, f H (θ) is the pure rotational Raman scattering phase function of the high quantum channel, λ0 is the laser emission wavelength, T z (z,λ0) is the on-path atmospheric transmittance, is the slant-path atmospheric transmittance of the low quantum channel, is the atmospheric transmittance of the high quantum channel, dθ is the field of view angle of the lateral telescope, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively;

[0102] Step 4.2: Extract a single spectral line in each of the high and low quantum number channels. The ratio Q(T,z) of the lateral pure rotational Raman scattering signals is expressed as:

[0103]

[0104] In the formula, and are the Raman scattering signal powers of the lateral high and low quantum channels, σ(J L ,T) and σ(J H ,T) are the backscattering cross-sections of the pure rotational Raman spectra of the low and high quantum channels, Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, T is the temperature, and are the scattering wavelengths of the low and high quantum channels respectively, and A and B are the calibration coefficients derived from the theoretical definitions;

[0105] Step 4.3: The temperature T can be obtained and expressed as:

[0106]

[0107] In the formula: Q(T,z) is the ratio of the lateral pure rotational Raman scattering signals, is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, and are the scattering wavelengths of the low and high quantum channels respectively, Δf r (θ) is the ratio of the phase functions of the lateral pure rotational Raman scattering high and low quantum number channels, T is the temperature, and A and B are the calibration coefficients derived from the theoretical definitions.

[0108] Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels and is expressed as:

[0109]

[0110] In the formula, f L (θ) is the pure rotational Raman scattering phase function of the low quantum channel, f H (θ) is the pure rotational Raman scattering phase function of the high quantum channel, β L (θ,λ L ) and β H (θ,λ H ) are the lateral scattering coefficients of the low and high quantum channels respectively, and β L (λ L ) and β H (λ H ) are the backscattering coefficients of the low and high quantum channels respectively;

[0111] is the atmospheric transmittance correction function and is expressed as:

[0112]

[0113] In the formula, is the slant-path atmospheric transmittance of the low quantum channel, is the atmospheric transmittance of the high quantum channel, θ is the scattering angle, is the extinction coefficient of the low quantum channel, is the extinction coefficient of the high quantum channel, and z is the detection altitude;

[0114] Step 5: Calculate the uncertainty of the lateral pure rotational Raman atmospheric temperature;

[0115] In Step 5, the temperature measurement uncertainty ΔT of the lateral pure rotational Raman can be expressed as:

[0116]

[0117] In the formula: is the ratio of the signal intensities of the high and low quantum numbers of the lateral pure rotational Raman, Q1 and Q2 are respectively the ratios of the signal intensities of the high and low quantum number channels of the lateral pure rotational Raman scattering at different temperature pairs, and are respectively the signal powers of the high and low quantum channels of the lateral pure rotational Raman scattering, and T1 and T2 are respectively the temperatures calculated for the first and second times.

[0118] Step 6: Stitch the low-level atmospheric temperature profile obtained by inverting the lateral pure rotational Raman lidar and the high-level atmospheric temperature profile obtained by inverting the backscattered pure rotational Raman lidar to obtain the whole-layer atmospheric temperature profile for blind-free detection.

[0119] Step 6 is specifically implemented according to the following steps:

[0120] Method 1: Use the phase function to respectively correct the echo signals of the high and low quantum channels of the lateral pure rotational Raman scattering, convert them into the echo signals of the high and low quantum channels of the backscattered pure rotational Raman scattering, and then invert the low-level and high-level data to obtain the normalized atmospheric temperature profile;

[0121] Or,

[0122] Method 2: Stitch in the range of the scattering angle from 178° to 180°. At this time, f L (θ)≈1, f H (θ)≈1. At this time, the lateral pure rotational Raman lidar equation and the backscattered pure rotational Raman lidar equation only differ by a constant, and the data of the two lidars can be stitched to obtain the whole-layer atmospheric temperature profile.

Claims

1. A Raman lidar system for detecting atmospheric temperature without blind zones in the surface layer, characterized in that, It includes a laser emission subsystem, a lateral telescope receiving and spectral splitting subsystem, and a data acquisition and inversion subsystem; The laser emission subsystem can emit a laser with a specific wavelength and vertically shoot it into the atmosphere; The lateral telescope receiving and spectral splitting subsystem is used to receive, separate, extract, and detect the pure rotational Raman scattering echo signals of the high and low quantum number channels of the lateral scattering relative to the laser emission spectrum; The data acquisition and inversion subsystem acquires the lateral pure rotational Raman scattering echo signals of the high and low quantum channels relative to the laser emission spectrum and realizes the data inversion of the atmospheric temperature. The data acquisition and inversion subsystem is connected to the lateral telescope receiving and spectral splitting subsystem; The laser emission subsystem includes a laser (1), a laser beam expander (2), and a 45° total reflection mirror (3); the laser (1), the laser beam expander (2), and the 45° total reflection mirror (3) are placed on the same horizontal plane. The horizontal laser emitted by the laser (1) is vertically shot into the atmosphere after passing through the laser beam expander (2) and the 45° total reflection mirror (3); the 45° total reflection mirror (3) is an electrically adjustable 45° total reflection mirror; The lateral telescope receiving and spectral splitting subsystem includes an electrically adjustable pitching bracket (11). Two lateral telescope groups (5) are installed on the electrically adjustable pitching bracket (11). The lateral telescope group (5) includes two lateral telescopes. After the light outlet of one lateral telescope, a first lens a (6), a first filter a (7), a second filter a (8), a second lens a (9), and a PMT photodetector a (10) are successively installed; after the light outlet of the other lateral telescope, a first lens b (16), a first filter b (17), a second filter b (18), a second lens b (19), and a PMT photodetector b (20) are successively installed; the PMT photodetector a (10) records the lateral pure rotational Raman scattering echo signals of the high quantum number channel of the lateral scattering relative to the laser emission spectrum, and the PMT photodetector b (20) records the lateral pure rotational Raman scattering echo signals of the low quantum number channel of the lateral scattering relative to the laser emission spectrum.

2. The Raman lidar system for detecting the atmospheric temperature without blind areas in the surface layer according to claim 1, wherein The laser (1) is a high-energy pulsed laser or a high-power continuous laser.

3. The Raman lidar system for detecting atmospheric temperature without blind zones in the surface layer according to claim 1, wherein The central wavelengths of the high quantum channels of the first filter a (7) and the second filter a (8) are: the Raman signal has the largest negative temperature change rate relative to the laser emission wavelength; the specific parameters are: the bandwidth is: 0.2 - 0.3 nm, the suppression rate is: OD is greater than or equal to 6, and the working angle is: 5° - 7°; The central wavelengths of the low quantum channels of the first filter b (17) and the second filter b (18) are: the Raman signal has the largest positive temperature change rate relative to the laser emission wavelength; the specific parameters are: the bandwidth is: 0.2 - 0.3 nm, the suppression rate is: OD is greater than or equal to 6, and the working angle is: 5° - 7°.

4. Raman lidar method for detecting atmospheric temperature without blind area in the surface layer, characterized in that, The near-surface blind-zone-free atmospheric temperature detection Raman lidar system as claimed in claim 1 is specifically implemented according to the following steps: Step 1, initialize the lateral pure rotational Raman scattering lidar; Step 2: The data received by the lateral telescope group (5) from the pitching rotation platform (11) for each altitude layer is a DC level signal; for the lateral Raman scattering echo signal received at each arbitrary angle of rotation within the pitching angle θ of 0 to 90° by the telescope, fitting all the collected level signals can obtain the lateral Raman scattering echo signal; Step 3: Optimization of the calibration function for detecting atmospheric temperature by the lateral pure rotational Raman lidar; Step 4: Obtaining the low-altitude atmospheric temperature profile through the inversion algorithm of the lateral pure rotational Raman scattering atmospheric temperature detection lidar; Step 5: Calculating the uncertainty of the lateral pure rotational Raman atmospheric temperature; Step 6: Stitching the low-altitude atmospheric temperature profile obtained by inverting the lateral pure rotational Raman scattering lidar and the high-altitude atmospheric temperature profile obtained by inverting the backward pure rotational Raman scattering lidar to obtain the whole-layer atmospheric temperature profile and achieve blind-zone-free detection.

5. The method for detecting the atmospheric temperature by Raman lidar without blind area in the surface layer according to claim 4, characterized in that, Step 3 is specifically implemented according to the following steps: Step 3.1: Let y = lnQ(z, T) and x = 1 / T, and the fitting function can be expressed as Step 3.2: Add the term x = 1 / T, then the calibration function is: The expression for the temperature T can be obtained as: CF1 ​ In the formula: is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, Q(T, z) is the ratio of the lateral pure rotational Raman scattering signal, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively, Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, is the atmospheric transmittance correction function, T is the temperature, and a, b, c are undetermined coefficients; Step 3.

3. Add the term y = lnQ(z, T), then the calibration function is: The expression of the temperature T can be obtained as: CF2 as follows: In the formula: is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, and Q(T,z) is the ratio of the lateral pure rotational Raman scattering signal, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively, is the atmospheric transmittance correction function, T is the temperature, Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, and a, b, and c are undetermined coefficients.

6. The Raman lidar method for detecting the atmospheric temperature in the near-surface layer without blind areas according to claim 4, characterized in that, Step 4 is specifically implemented according to the following steps: Step 4.1: From the geometric structure of the lateral Raman lidar, the pure rotational Raman scattering echo signals of the lateral high and low quantum channels can be obtained and The formulas are as follows: wherein, and are the signal powers of the high and low quantum channels of the lateral pure rotational Raman scattering respectively, E0 is the power of the high-energy pulsed laser or high-power continuous laser, z is the detection altitude, θ is the scattering angle, J is the rotational quantum number, A is the receiving area of the telescope, K is the system constant, D is the horizontal distance between the lateral telescope and the vertical laser beam, T is the temperature, N(z) is the atmospheric molecular number density, represents the volume ratio of nitrogen and oxygen molecules in the low quantum channel in the atmosphere, represents the volume ratio of nitrogen and oxygen molecules in the high quantum channel in the atmosphere, σ i (J,T) represents the backscattering cross section of the pure rotational Raman spectrum of nitrogen and oxygen molecules, f L (θ) is the pure rotational Raman scattering phase function of the low quantum channel, f H (θ) is the pure rotational Raman scattering phase function of the high quantum channel, λ0 is the laser emission wavelength, T z (z,λ0) is the on-way atmospheric transmittance, is the slant-path atmospheric transmittance of the low quantum channel, is the atmospheric transmittance of the high quantum channel, dθ is the field of view angle of the lateral telescope, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively; Step 4.2: Extract a single spectral line in the high and low quantum number channels respectively, and the ratio Q(T, z) of the lateral pure rotational Raman scattering signal is expressed as: In the formula, and are respectively the Raman scattering signal powers of the lateral high and low quantum channels, σ(J L , T) and σ(J H , T) are the backward scattering cross-sections of the pure rotational Raman spectral lines of the low and high quantum channels, Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, T is the temperature, and are respectively the scattering wavelengths of the low and high quantum channels, and A and B are the calibration coefficients derived from the theoretical definitions; Step 4.3: The temperature T can be obtained and expressed as: where: Q(T,z) is the ratio of the lateral pure rotational Raman scattering signal, is the atmospheric transmittance correction function, z is the detection altitude, θ is the scattering angle, and are the scattering wavelengths of the low quantum channel and the high quantum channel respectively, Δf r (θ) is the ratio of the phase functions of the high and low quantum number channels of the lateral pure rotational Raman scattering, T is the temperature, and A and B are the calibration coefficients derived from the theoretical definitions respectively; Δf r (θ) is the ratio of the pure rotational Raman scattering phase functions of the lateral high and low quantum number channels, expressed as: where f L (θ) is the pure rotational Raman scattering phase function of the low quantum channel, and f H (θ) is the pure rotational Raman scattering phase function of the high quantum channel. β L (θ, λ L ) and β H (θ, λ H ) are the lateral scattering coefficients of the low quantum channel and the high quantum channel respectively. β L (λ L ) and β H (λ H ) are the backscattering coefficients of the low quantum channel and the high quantum channel respectively; is the atmospheric transmittance correction function, expressed as: In the formula, is the slant-path atmospheric transmittance of the low quantum channel, is the atmospheric transmittance of the high quantum channel, θ is the scattering angle, is the extinction coefficient of the low quantum channel, is the extinction coefficient of the high quantum channel, and z is the detection altitude.

7. The Raman lidar method for detecting the atmospheric temperature in the near-surface layer without blind areas according to claim 4, characterized in that In Step 5, the temperature measurement uncertainty ΔT of the lateral pure rotational Raman can be expressed as: In the formula: is the ratio of the signal intensities of the high and low quantum numbers of the lateral pure rotational Raman, and Q1 and Q2 are the ratios of the signal intensities of the high and low quantum number channels of the lateral pure rotational Raman scattering for different temperature pairs, respectively. and are the signal powers of the high and low quantum channels of the lateral pure rotational Raman scattering, respectively, and T1 and T2 are the temperatures calculated for the first and second times, respectively.

8. The Raman lidar method for detecting the atmospheric temperature without blind areas in the near-surface layer according to claim 6, characterized in that, Step 6 is specifically implemented according to the following steps: Method 1: Using the phase function to correct the echo signals of the high and low quantum channels of the lateral pure rotational Raman scattering respectively, converting them into the echo signals of the high and low quantum channels of the backward pure rotational Raman scattering, and then inverting the low-altitude and high-altitude data to obtain the normalized atmospheric temperature profile; Or, Method 2: Stitching is performed within the range of scattering angles from 178° to 180°, where f L (θ) ≈ 1, f H (θ) ≈ 1; at this time, the lateral pure rotational Raman lidar equation and the backscatter pure rotational Raman lidar equation differ only by a constant, and the two lidar data can be stitched to obtain the whole-atmosphere temperature profile.

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