Raman lidar system and method for near-ground layer non-blind area water vapor and aerosol detection

Abstract

The disclosed near-ground layer blind area-free water vapor and aerosol detection Raman laser radar system comprises a laser emission subsystem, a lateral telescope group receiving and light splitting subsystem, and a data acquisition and inversion subsystem; the laser emission subsystem can emit laser of specific wavelength and vertically emit to the atmosphere; the lateral telescope group receiving and light splitting subsystem is used for receiving and separating and extracting the lateral nitrogen vibration Raman echo signal with 2331cm ‑1 frequency shift and the water vapor vibration Raman echo signal with 3652cm ‑1 frequency shift relative to the laser emission spectrum; the data acquisition and inversion subsystem is used for recording the lateral Raman scattering echo signals of nitrogen and water vapor, and the data acquisition and inversion subsystem is connected with the lateral telescope group receiving and light splitting subsystem. The system realizes the detection of the water vapor content and the aerosol optical parameter of the near-ground layer atmosphere. The near-ground layer blind area-free water vapor and aerosol detection Raman laser radar method is also disclosed.

Description

Technical Field

[0001] The present invention belongs to the technical field of atmospheric water vapor and aerosol detection, and specifically relates to a Raman lidar system for detecting water vapor and aerosols in the near-ground layer without blind spots, and also relates to a Raman lidar method for detecting water vapor and aerosols in the near-ground layer without blind spots. Background Art

[0002] Water vapor is a vital component of the atmosphere, closely intertwined with human life and the entire biological world. Water vapor in the atmosphere originates from abundant sources and is released into the atmosphere as a gas. It is continuously diffused through the air by atmospheric convection and turbulence, resulting in uneven distribution of water vapor and rapid spatial and temporal variations.

[0003] Aerosols are important substances for studying the Earth's environment, climate, and atmospheric radiation transmission. At the same time, atmospheric water vapor can condense on the aerosol surface, causing aerosol particles to form cloud condensation nuclei, affecting the cloud's microstructure and optical properties at different levels.

[0004] Raman lidar uses laser radar technology to measure water vapor and aerosol profiles. However, traditional backscattering Raman lidars are unable to detect water vapor and aerosol concentrations in the lower atmosphere due to blind spots and transition zones caused by geometric overlap. Therefore, backscattering Raman lidar has certain limitations for detecting water vapor and aerosols throughout the atmosphere, especially in the lower atmosphere. To achieve blind-spot-free detection, the lidar receiving system was redesigned, employing side Raman scattering lidar technology to enable water vapor and aerosol detection in the lower atmosphere. Summary of the Invention

[0005] The first object of the present invention is to provide a Raman lidar system for detecting water vapor and aerosols in the near-surface layer without blind spots, so as to realize the detection of atmospheric water vapor content and aerosol optical parameters in the near-surface layer.

[0006] The second object of the present invention is to provide a Raman lidar method for detecting water vapor and aerosols in the near-surface layer without blind spots.

[0007] The first technical solution adopted by the present invention is a Raman lidar system for detecting water vapor and aerosols in the near-surface layer without blind spots, comprising a laser emission subsystem, a side telescope group receiving and spectroscopic subsystem, and a data acquisition and inversion subsystem;

[0008] A laser emission subsystem capable of emitting laser light of a specific wavelength and shooting it vertically into the atmosphere;

[0009] The side telescope group receiving and spectroscopic subsystem is used to receive, separate, extract and detect the relative laser emission spectrum with 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman echo signal and the 3652 cm-1 Frequency-shifted water vapor vibration Raman echo signal;

[0010] Data acquisition and inversion subsystem, collects relative laser emission spectra with 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman scattering echo signal and the 3652 cm -1 The frequency-shifted lateral water vapor vibration Raman scattering echo signal is obtained, and the data inversion of the water vapor mixing ratio is realized. The data acquisition and inversion subsystem is connected to the lateral telescope group receiving and spectroscopic subsystem.

[0011] The present invention is also characterized in that

[0012] The laser emission subsystem includes a laser, a laser beam expander and a 45° total reflector; the laser, the laser beam expander and the 45° total reflector are placed on the same horizontal plane, and the horizontal laser emitted by the laser passes through the laser beam expander and the 45° total reflector and then vertically emits into the atmosphere.

[0013] The laser is a high-energy pulse laser or a high-power continuous laser.

[0014] The side telescope group receiving and spectroscopic subsystem includes an electrically adjustable pitch bracket, on which a side telescope group is installed. The side telescope group includes two side telescopes, one of which is provided with a first lens a, a first filter, a second lens a, and a PMT photodetector a in sequence behind the light exit port of the side telescope; the other is provided with a first lens b, a second filter, a second lens b, and a PMT photodetector b in sequence behind the light exit port of the side telescope; the PMT photodetector a detects a relative laser emission spectrum having a wavelength of 2331 cm -1 The frequency-shifted lateral nitrogen vibration Raman echo signal; PMT photodetector b is used to detect the 3652cm -1 Frequency-shifted water vapor vibration Raman echo signal; First filter: center wavelength is: 2331cm relative to the laser emission wavelength -1 Frequency shift, bandwidth is 1nm~1.2nm, suppression rate is OD6~OD7; second filter: center wavelength is 3652cm relative to laser emission wavelength -1 Frequency shift, bandwidth is 1nm~1.5nm, suppression rate is OD6~OD7.

[0015] The second technical solution adopted by the present invention is:

[0016] The Raman lidar method for detecting water vapor and aerosols in the near-surface layer without blind spots is implemented in the following steps:

[0017] Step 1: Initialize the side Raman scattering lidar.

[0018] Step 2: The side telescope group receives the side scattered echo signal and obtains the N2 and H2O side vibration Raman echo signals through spectrometry and photoelectric conversion;

[0019] Step 3: Obtain low-level water vapor profile and aerosol extinction profile through the side Raman scattering water vapor and aerosol detection lidar inversion algorithm;

[0020] Step 4: Splice the low-level water vapor and aerosol profiles obtained by the side Raman scattering lidar inversion with the high-level water vapor and aerosol profiles obtained by the back Raman scattering lidar inversion to obtain the entire layer of water vapor and aerosol profiles to achieve blind-spot detection.

[0021] The present invention is also characterized in that

[0022] Step 3 is implemented as follows:

[0023] Step 3.1: Based on the geometric structure of the side Raman scattering lidar, the power of the side nitrogen Raman scattering signal can be obtained as P(z,λ N ,θ) and the power of the lateral water vapor Raman scattering signal is P(z,λ H ,θ), the formula is as follows:

[0024]

[0025]

[0026] Where, P(z,λ N ,θ) and P(z,λ H ,θ) are the Raman scattering signal powers of lateral nitrogen and water vapor respectively, E0 is the power of high energy pulse laser or high power continuous laser, z is the detection height, θ is the scattering angle, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively, λ0 is the laser emission wavelength, A is the receiving area of ​​the telescope, η(λ N ) and η(λ H ) are the optical efficiencies of the side Raman scattering nitrogen and water vapor channels, D is the horizontal distance between the side telescope group and the vertical laser beam, r is the slant distance from the side scattered light at the detection height z to the side telescope group 5, dθ is the field of view of the side telescope, α aer (z,λ N ) and α aer (z,λ H ) are the aerosol extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α mol (z,λ N ) and α mol (z,λ H) are the atmospheric molecular extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α aer (z,λ0) and α mol (z,λ0) are the aerosol and atmospheric molecule extinction coefficients corresponding to the initial wavelength, β N (z,λ N ,θ) and β H (z,λ H ,θ) are the side scattering coefficients of nitrogen and water vapor vibration Raman scattering, respectively;

[0027] Step 3.2: The inversion algorithm for the water vapor mixing ratio detected by side Raman scattering lidar is:

[0028]

[0029] Where w r (z) is the water vapor mixing ratio of the side Raman scattering lidar, P(z,λ N ,θ) and P(z,λ H ,θ) are the Raman scattering signal powers of nitrogen and water vapor respectively, Δf r (θ) is the Raman scattering phase function, ΔT r (λ H ,λ N ,z,θ) is the specific transmittance, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively, z is the detection height, θ is the scattering angle, K * (z) is the system constant;

[0030] K * (z) is the system constant, expressed as:

[0031]

[0032] Where, O N (z) and O H (z) LiDAR geometric overlap factor for nitrogen and water vapor channels, η(λ N ) and η(λ H ) are the optical efficiencies of the side Raman scattering nitrogen and water vapor channels, respectively; Δf r (θ) is the Raman scattering phase function, expressed as:

[0033]

[0034] Where Δf r (θ) is the Raman scattering phase function, f N (θ) and f H (θ) are the side Raman scattering phase functions of nitrogen and water vapor, βN (θ,λ N ) and β H (θ,λ H ) are the side scattering coefficients of nitrogen and water vapor, β N (λ N ) and β H (λ H ) are the backscattering coefficients of nitrogen and water vapor respectively;

[0035] ΔT r (z,λ H ,λ N ,θ) is the atmospheric transmittance correction function, which is expressed as:

[0036]

[0037] Where, ΔT r (z,λ H ,λ N ,θ) is the atmospheric transmittance correction function, T r (z,λ N ,θ) and T r (z,λ H ,θ) are the atmospheric transmittances of nitrogen and water vapor respectively, z is the detection height, θ is the scattering angle, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α aer (z,λ N ) and α aer (z,λ H ) are the aerosol extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α mol (z,λ N ) and α mol (z,λ H ) are the atmospheric molecular extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively;

[0038] Step 3.3: The aerosol extinction coefficient detected by the side Raman scattering lidar is:

[0039]

[0040] Where, α aer (z,λ0) is the aerosol extinction coefficient f detected by the side Raman scattering lidar N (z) is the phase function of nitrogen molecules, P(z,λ N ,θ) is the Raman scattering signal power of nitrogen in the side direction, α mol (z,λ N) is the atmospheric molecular extinction coefficient corresponding to the nitrogen lateral vibration Raman scattering wavelength, λ0 is the laser emission wavelength, λ N is the lateral vibration Raman scattering wavelength of nitrogen, θ is the scattering angle, and z is the detection height.

[0041] The beneficial effects of the present invention are:

[0042] The proposed system significantly differs from traditional monostatic backscatter lidars. It utilizes a bistatic sidescatter lidar format, addressing the challenge of accurately detecting low-level water vapor and aerosols. This blind-spot-free Raman lidar system for water vapor and aerosol detection consists of three main components: a laser emission subsystem, a side-viewing telescope receiving and spectrometer subsystem capable of 0-90° elevation, and a data acquisition and inversion subsystem. The laser emission subsystem emits pulsed or continuous laser light of a specified wavelength into the atmosphere, where it scatters off atmospheric particles and molecules. The side-viewing telescope receiving and spectrometer subsystem receives side Raman scattering echo signals from atmospheric nitrogen and water vapor. The data acquisition and inversion subsystem collects and inverts the atmospheric echo signals to obtain information on the low-level water vapor mixing ratio and aerosol optical parameters. The range resolution dz of this blind-spot-free sidescatter lidar is calculated as the length of the laser beam received, corresponding to the telescope's receiving field of view dθ at an elevation angle θ. The water vapor and aerosol extinction profiles of a side Raman scattering lidar can be obtained by continuously rotating the telescope's receiving subsystem's elevation angle and recording the side Raman scattering echo signals of atmospheric nitrogen and water vapor at each angle θ. Since each elevation angle corresponds to a specific altitude, two Raman lidar profile equations for nitrogen and water vapor can be generated, which are used to calculate and obtain the near-surface atmospheric water vapor mixing ratio profile and the near-surface aerosol extinction coefficient profile.

[0043] The method proposed in this paper utilizes a bistatic side Raman scattering lidar detection method with separate transmitters and receivers to design a Raman lidar system for detecting water vapor and aerosols in the near-surface layer without blind spots, enabling precise detection of water vapor and aerosols in the near-surface layer. Using a pulsed laser as the laser transmitting unit, a backscattering lidar system for atmospheric water vapor and aerosol detection can be designed and constructed simultaneously. The combined use of a side Raman scattering lidar system with no blind spots and a backscattering lidar system enables precise detection of water vapor and aerosols from the near-surface to the upper atmosphere, providing novel laser remote sensing technologies and methods for climate and environmental research. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic structural diagram of a Raman lidar system for detecting water vapor and aerosols in near-surface layers without blind spots according to the present invention;

[0045] Figure 2This is a spectrum distribution diagram of the atmospheric echo signal received by the lateral vibration Raman scattering laser radar of the present invention;

[0046] Figure 3 Schematic diagram of the calculation model of the side scatter laser radar field of view angle and range resolution in the method of the present invention;

[0047] Figure 4 Schematic diagram of the structure of the backward and lateral full-layer water vapor and aerosol lidar detection system;

[0048] Figure 5 Flowchart of the method of the present invention.

[0049] In the figure, 1. Laser, 2. Laser beam expander, 3. 45° fully reflective mirror, 4. Backward telescope, 5. Side telescope group, 6. First lens a, 7. First filter, 8. Second lens a, 9. PMT photodetector a, 10. Electric adjustable pitch bracket, 11. First data acquisition system, 12. Prism, 13. Backward Raman scattering water vapor and aerosol detection lidar spectrometer system, 14. Second data acquisition system, 15. First lens b, 16. Second filter, 17. Second lens b, 18. PMT photodetector b. DETAILED DESCRIPTION

[0050] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] The present invention provides a Raman lidar system for detecting water vapor and aerosols in the near-surface layer without blind spots. Figure 1-2 , including laser emission subsystem, side telescope group receiving and spectroscopic subsystem, data acquisition and inversion subsystem;

[0052] A laser emission subsystem capable of emitting laser light of a specific wavelength and shooting it vertically into the atmosphere;

[0053] The side telescope group receiving and spectrophotometer system is used to receive, separate, extract and detect the relative laser emission spectrum with 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman echo signal and the 3652 cm -1 Frequency-shifted water vapor vibration Raman echo signal;

[0054] The data acquisition and inversion subsystem is the first data acquisition system 11, which collects the relative laser emission spectrum with 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman scattering echo signal and the 3652 cm -1 The frequency-shifted lateral water vapor vibration Raman scattering echo signal is obtained, and the water vapor mixing ratio data inversion is realized. The data acquisition and inversion subsystem is connected to the lateral telescope group receiving and spectrometer subsystem.

[0055] The laser emission subsystem includes a laser 1, a laser beam expander 2 and a 45° total reflector 3; the laser 1, the laser beam expander 2 and the 45° total reflector 3 are placed on the same horizontal plane, and the horizontal laser emitted by the laser 1 passes through the laser beam expander 2 and the 45° total reflector 3 and then vertically emits into the atmosphere; the 45° total reflector 3 is an electrically adjustable 45° total reflector.

[0056] The laser 1 is a high-energy pulse laser or a high-power continuous laser.

[0057] The side telescope group receiving and spectroscopic subsystem includes an electrically adjustable pitch bracket 10, on which a side telescope group 5 is mounted. The side telescope group 5 includes two side telescopes. A first lens a6, a first filter 7, a second lens a8, and a PMT photodetector a9 are sequentially mounted behind the light exit of one side telescope; a first lens b15, a second filter 16, a second lens b17, and a PMT photodetector b18 are sequentially mounted behind the light exit of the other side telescope; the PMT photodetector a9 detects a relative laser emission spectrum having a wavelength of 2331 cm -1 The frequency-shifted lateral nitrogen vibration Raman echo signal; PMT photodetector b18 is used to detect the 3652cm -1 Frequency-shifted water vapor vibration Raman echo signal; First filter 7: The center wavelength is 2331cm relative to the laser emission wavelength -1 Frequency shift, bandwidth is 1nm~1.2nm, suppression rate is OD6~OD7; second filter 16: center wavelength is 3652cm relative to laser emission wavelength -1 Frequency shift, bandwidth is 1nm~1.5nm, suppression rate is OD6~OD7.

[0058] like Figure 4 As shown, it is an example of the use of the system of the present invention in combination with a backscattering Raman lidar system. The backscattering Raman lidar system consists of a backscattering telescope 4, a prism 12, a backscattering Raman lidar spectroscopic system 13 for detecting water vapor and aerosols, and a second data acquisition system 14. It can be combined with a side Raman lidar to realize precise detection of water vapor and aerosols from near the surface to the upper atmosphere without blind spots.

[0059] The side telescope group receiving and spectroscopic subsystem and the laser emission subsystem are located in two separate locations, and the distance D between the light outlet of the side telescope group 5 and the 45° total reflector 3 is. It can be composed of two separate side telescopes. The field of view of the side telescope group is perpendicular to and points to the laser beam to maintain a consistent field of view. The side scattered light received by the side telescope group 5 is collimated by the first lens a6 and then separated by the first filter 7 to extract the side vibration Raman scattering echo signal of nitrogen. The light is then converged by the second lens a8 and received by the PMT photodetector a9. The side scattered light received by the side telescope group 5 is collimated by the first lens b15 and then separated by the second filter 16 to extract the side vibration Raman scattering echo signal of water vapor. The light is then converged by the second lens b17 and received by the PMT photodetector b18.

[0060] The receiving subsystem of the side telescope group 5 consists of two independent side telescopes. The field of view of the side telescope group is perpendicular to and points towards the laser beam, and the field of view is consistent;

[0061] The first lens a6, the first filter 7, and the second lens a8, as well as the first lens b15, the second filter 16, and the second lens b17 are respectively arranged behind the light exit of the side telescope group 5. One of the side telescopes receives and separates with the spectroscopic system to extract the lateral vibration Raman scattering echo signal of nitrogen, and the other side telescope receives and separates with the spectroscopic system to extract the lateral vibration Raman scattering echo signal of water vapor;

[0062] The data acquisition and inversion subsystems collect the relative laser emission spectrum with 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman scattering echo signal and the 3652 cm -1 The frequency-shifted lateral water vapor vibration Raman scattering echo signal is used to invert the water vapor mixing ratio. The relative laser emission spectrum has a 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman scattering echo signal can be used to invert aerosol optical parameters.

[0063] Two PMT photodetectors detect the relative laser emission spectrum with 2331 cm -1 The frequency-shifted lateral nitrogen vibration Raman echo signal and the 3652 cm -1 Frequency-shifted water vapor vibration Raman echo signal;

[0064] The relative laser emission spectrum recorded by the PMT photodetector and data acquisition system has a wavelength of 2331 cm -1 The frequency-shifted lateral nitrogen vibration Raman scattering echo signal and the 3652 cm -1The frequency-shifted lateral water vapor vibration Raman scattering echo signal is used to invert the water vapor mixing ratio. The relative laser emission spectrum recorded by the PMT photoelectric detector and data acquisition system has a wavelength of 2331 cm -1 The frequency-shifted lateral nitrogen vibration Raman scattering echo signal is also used to invert aerosol optical parameters;

[0065] The profile of the side-view lidar data is achieved by receiving the side-view telescope group and rotating the pitch angle of the spectrometer system;

[0066] The range resolution of the side-view LiDAR is non-equidistant and is determined by the spacing D between the transceiver systems and the field of view of the side telescope group.

[0067] The side laser radar range resolution dz is the length of the laser beam received corresponding to the receiving field of view dθ of the side telescope at the pitch angle θ;

[0068] When the light source is a pulsed laser, it can be used as an excitation light source to construct a backscattering Raman lidar, and together with the near-ground layer water vapor and aerosol detection Raman lidar system, a comprehensive laser remote sensing system can be constructed for accurate detection of water vapor and aerosols from low to high layers without blind spots.

[0069] The present invention also provides a Raman lidar method for detecting water vapor and aerosol in the near-surface layer without blind spots, such as Figure 3 and 5 As shown, please follow the steps below:

[0070] Step 1: Initialize the side Raman scattering lidar.

[0071] Step 2: The side telescope group 5 on the electrically adjustable pitch bracket 10 receives the side scattered echo signal and obtains the N2 and H2O side vibration Raman echo signals through spectrometry and photoelectric conversion;

[0072] Step 3: Obtain low-level water vapor profile and aerosol extinction profile through the side Raman scattering water vapor and aerosol detection lidar inversion algorithm;

[0073] Step 3 is implemented as follows:

[0074] Step 3.1: Based on the geometric structure of the side Raman scattering lidar, the power of the side nitrogen Raman scattering signal can be obtained as P(z,λ N ,θ) and the power of the lateral water vapor Raman scattering signal is P(z,λ H ,θ), the formula is as follows:

[0075]

[0076]

[0077] Where, P(z,λ N ,θ) and P(z,λ H ,θ) are the Raman scattering signal powers of lateral nitrogen and water vapor respectively, E0 is the power of high energy pulse laser or high power continuous laser, z is the detection height, θ is the scattering angle, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively, λ0 is the laser emission wavelength, A is the receiving area of ​​the telescope, η(λ N ) and η(λ H ) are the optical efficiencies of the side Raman scattering nitrogen and water vapor channels, D is the horizontal distance between the side telescope group and the vertical laser beam, r is the slant distance from the side scattered light at the detection height z to the side telescope group 5, dθ is the field of view of the side telescope, α aer (z,λ N ) and α aer (z,λ H ) are the aerosol extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α mol (z,λ N ) and α mol (z,λ H ) are the atmospheric molecular extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α aer (z,λ0) and α mol (z,λ0) are the aerosol and atmospheric molecule extinction coefficients corresponding to the initial wavelength, β N (z,λ N ,θ) and β H (z,λ H ,θ) are the side scattering coefficients of nitrogen and water vapor vibration Raman scattering, respectively;

[0078] Step 3.2: The inversion algorithm for the water vapor mixing ratio detected by side Raman scattering lidar is:

[0079]

[0080] Where w r (z) is the water vapor mixing ratio of the side Raman scattering lidar, P(z,λ N ,θ) and P(z,λ H ,θ) are the Raman scattering signal powers of nitrogen and water vapor respectively, Δf r (θ) is the Raman scattering phase function, ΔT r (λ H ,λ N ,z,θ) is the specific transmittance, λ N and λ Hare the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively, z is the detection height, θ is the scattering angle, K * (z) is the system constant;

[0081] K * (z) is the system constant, expressed as:

[0082]

[0083] Where, O N (z) and O H (z) LiDAR geometric overlap factor for nitrogen and water vapor channels, η(λ N ) and η(λ H ) are the optical efficiencies of the side Raman scattering nitrogen and water vapor channels, respectively; Δf r (θ) is the Raman scattering phase function, expressed as:

[0084]

[0085] Where Δf r (θ) is the Raman scattering phase function, f N (θ) and f H (θ) are the side Raman scattering phase functions of nitrogen and water vapor, β N (θ,λ N ) and β H (θ,λ H ) are the side scattering coefficients of nitrogen and water vapor, β N (λ N ) and β H (λ H ) are the backscattering coefficients of nitrogen and water vapor respectively;

[0086] ΔT r (z,λ H ,λ N ,θ) is the atmospheric transmittance correction function, which is expressed as:

[0087]

[0088] Where, ΔT r (z,λ H ,λ N ,θ) is the atmospheric transmittance correction function, T r (z,λ N ,θ) and T r (z,λ H ,θ) are the atmospheric transmittances of nitrogen and water vapor respectively, z is the detection height, θ is the scattering angle, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, αaer (z,λ N ) and α aer (z,λ H ) are the aerosol extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α mol (z,λ N ) and α mol (z,λ H ) are the atmospheric molecular extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively;

[0089] Step 3.3: The aerosol extinction coefficient detected by the side Raman scattering lidar is:

[0090]

[0091] Where, α aer (z,λ0) is the aerosol extinction coefficient f detected by the side Raman scattering lidar N (z) is the phase function of nitrogen molecules, P(z,λ N ,θ) is the Raman scattering signal power of nitrogen in the side direction, α mol (z,λ N ) is the atmospheric molecular extinction coefficient corresponding to the nitrogen lateral vibration Raman scattering wavelength, λ0 is the laser emission wavelength, λ N is the lateral vibration Raman scattering wavelength of nitrogen, θ is the scattering angle, and z is the detection height.

[0092] Step 4: Splice the low-level water vapor and aerosol profiles obtained by the side Raman scattering lidar inversion with the high-level water vapor and aerosol profiles obtained by the back Raman scattering lidar inversion to obtain the entire layer of water vapor and aerosol profiles to achieve blind-spot detection.

Claims

1. Raman lidar system for detecting water vapor and aerosols in the near-surface layer without blind spots, characterized by: It includes laser emission subsystem, side telescope group receiving and spectroscopic subsystem, data acquisition and inversion subsystem; The laser emission subsystem is capable of emitting laser light of a specific wavelength and shooting it vertically into the atmosphere; The side telescope group receiving and spectrophotometer system is used to receive, separate, extract and detect the relative laser emission spectrum with 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman echo signal and the 3652 cm -1 Frequency-shifted water vapor vibration Raman echo signal; The side telescope group receiving and spectroscopic subsystem comprises an electrically adjustable pitch bracket (10), a side telescope group (5) is mounted on the electrically adjustable pitch bracket (10), and the side telescope group (5) comprises two side telescopes, wherein a first lens a (6), a first filter (7), a second lens a (8) and a PMT photodetector a (9) are sequentially mounted behind the light outlet of one side telescope; a first lens b (15), a second filter (16), a second lens b (17) and a PMT photodetector b (18) are sequentially mounted behind the light outlet of the other side telescope; the PMT photodetector a (9) detects a relative laser emission spectrum having a wavelength of 2331 cm -1 The frequency-shifted lateral nitrogen vibration Raman echo signal; PMT photodetector b (18) is used to detect the 3652cm -1 Frequency-shifted water vapor vibration Raman echo signal; first filter (7): the center wavelength is 2331cm relative to the laser emission wavelength -1 Frequency shift, bandwidth is 1nm~1.2nm, suppression rate is OD6~OD7; second filter (16): center wavelength is 3652cm relative to laser emission wavelength -1 Frequency shift, bandwidth is 1nm~1.5nm, suppression rate is OD6~OD7; The data acquisition and inversion subsystem collects the relative laser emission spectrum with 2331cm -1 The frequency-shifted lateral nitrogen vibration Raman scattering echo signal and the 3652 cm -1 The frequency-shifted lateral water vapor vibration Raman scattering echo signal is used to invert the water vapor mixing ratio data. The data acquisition and inversion subsystem is connected to the lateral telescope group receiving and spectrometer subsystem; The power of the lateral nitrogen Raman scattering signal is P(z,λ N ,θ), the power of the lateral water vapor Raman scattering signal is P(z,λ H ,θ), the formula is as follows: Where, P(z,λ N ,θ) and P(z,λ H ,θ) are the Raman scattering signal powers of lateral nitrogen and water vapor respectively, E0 is the power of high energy pulse laser or high power continuous laser, z is the detection height, θ is the scattering angle, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively, λ0 is the laser emission wavelength, A is the receiving area of ​​the telescope, η(λ N ) and η(λ H ) are the optical efficiencies of the side Raman scattering nitrogen and water vapor channels, D is the horizontal distance between the side telescope group and the vertical laser beam, r is the slant distance from the side scattered light at the detection height z to the side telescope group (5), dθ is the field of view of the side telescope, α aer (z,λ N ) and α aer (z,λ H ) are the aerosol extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α mol (z,λ N ) and α mol (z,λ H ) are the atmospheric molecular extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α aer (z,λ0) and α mol (z,λ0) are the aerosol and atmospheric molecule extinction coefficients corresponding to the initial wavelength, β N (z,λ N ,θ) and β H (z,λ H ,θ) are the side scattering coefficients of nitrogen and water vapor vibration Raman scattering, respectively; The aerosol extinction coefficient detected by side Raman scattering lidar is: Where, α aer (z,λ0) is the aerosol extinction coefficient detected by the side Raman scattering lidar, f N (z) is the phase function of nitrogen molecules, P(z,λ N ,θ) is the Raman scattering signal power of nitrogen in the side direction, α mol (z,λ N ) is the atmospheric molecular extinction coefficient corresponding to the nitrogen lateral vibration Raman scattering wavelength, λ0 is the laser emission wavelength, λ N is the lateral vibration Raman scattering wavelength of nitrogen, θ is the scattering angle, and z is the detection height.

2. The Raman lidar system for detecting water vapor and aerosol in the near-surface layer without blind spots according to claim 1 is characterized in that: The laser emission subsystem comprises 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, and the horizontal laser emitted by the laser (1) passes through the laser beam expander (2) and the 45° total reflection mirror (3) and then is vertically emitted into the atmosphere.

3. The Raman lidar system for detecting water vapor and aerosol in the near-surface layer without blind spots according to claim 2 is characterized in that: The laser (1) is a high-energy pulse laser or a high-power continuous laser.

4. A Raman lidar method for detecting water vapor and aerosols in the near-surface layer without blind spots, characterized in that: Please follow the steps below to implement it: Step 1: Initialize the side Raman scattering lidar; Step 2: The side telescope group (5) receives the side scattered echo signal and obtains the N2 and H2O side vibration Raman echo signals through spectrometry and photoelectric conversion; Step 3: Obtain low-level water vapor profile and aerosol extinction profile through the side Raman scattering water vapor and aerosol detection lidar inversion algorithm; Step 3 is implemented as follows: Step 3.1: Based on the geometric structure of the side Raman scattering lidar, the power of the side nitrogen Raman scattering signal is P(z,λ N ,θ), the power of the lateral water vapor Raman scattering signal is P(z,λ H ,θ), the formula is as follows: Where, P(z,λ N ,θ) and P(z,λ H ,θ) are the Raman scattering signal powers of lateral nitrogen and water vapor respectively, E0 is the power of high energy pulse laser or high power continuous laser, z is the detection height, θ is the scattering angle, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively, λ0 is the laser emission wavelength, A is the receiving area of ​​the telescope, η(λ N ) and η(λ H ) are the optical efficiencies of the side Raman scattering nitrogen and water vapor channels, D is the horizontal distance between the side telescope group and the vertical laser beam, r is the slant distance from the side scattered light at the detection height z to the side telescope group (5), dθ is the field of view of the side telescope, α aer (z,λ N ) and α aer (z,λ H ) are the aerosol extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α mol (z,λ N ) and α mol (z,λ H ) are the atmospheric molecular extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α aer (z,λ0) and α mol (z,λ0) are the aerosol and atmospheric molecule extinction coefficients corresponding to the initial wavelength, β N (z,λ N ,θ) and β H (z,λ H ,θ) are the side scattering coefficients of nitrogen and water vapor vibration Raman scattering, respectively; Step 3.2: The inversion algorithm for the water vapor mixing ratio detected by side Raman scattering lidar is: Where w r (z) is the water vapor mixing ratio of the side Raman scattering lidar, P(z,λ N ,θ) and P(z,λ H ,θ) are the Raman scattering signal powers of nitrogen and water vapor respectively, Δf r (θ) is the Raman scattering phase function, ΔT r (λ H ,λ N ,z,θ) is the specific transmittance, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively, z is the detection height, θ is the scattering angle, K * (z) is the system constant; K * (z) is the system constant, expressed as: Where, O N (z) and O H (z) are the lidar geometric overlap factors of the nitrogen and water vapor channels, η(λ N ) and η(λ H ) are the optical efficiencies of the side Raman scattering nitrogen and water vapor channels, respectively; Δf r (θ) is the Raman scattering phase function, expressed as: Where Δf r (θ) is the Raman scattering phase function, f N (θ) and f H (θ) are the side Raman scattering phase functions of nitrogen and water vapor, β N (θ,λ N ) and β H (θ,λ H ) are the side scattering coefficients of nitrogen and water vapor, β N (λ N ) and β H (λ H ) are the backscattering coefficients of nitrogen and water vapor respectively; ΔT r (z,λ H ,λ N ,θ) is the atmospheric transmittance correction function, which is expressed as: Where, ΔT r (z,λ H ,λ N ,θ) is the atmospheric transmittance correction function, T r (z,λ N ,θ) and T r (z,λ H ,θ) are the atmospheric transmittances of nitrogen and water vapor respectively, z is the detection height, θ is the scattering angle, λ N and λ H are the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α aer (z,λ N ) and α aer (z,λ H ) are the aerosol extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor, α mol (z,λ N ) and α mol (z,λ H ) are the atmospheric molecular extinction coefficients corresponding to the lateral vibration Raman scattering wavelengths of nitrogen and water vapor respectively; Step 3.3: The aerosol extinction coefficient detected by the side Raman scattering lidar is: Where, α aer (z,λ0) is the aerosol extinction coefficient detected by the side Raman scattering lidar, f N (z) is the phase function of nitrogen molecules, P(z,λ N ,θ) is the Raman scattering signal power of nitrogen in the side direction, α mol (z,λ N ) is the atmospheric molecular extinction coefficient corresponding to the nitrogen lateral vibration Raman scattering wavelength, λ0 is the laser emission wavelength, λ N is the lateral vibration Raman scattering wavelength of nitrogen, θ is the scattering angle, and z is the detection height; Step 4: Splice the lower-level water vapor and aerosol profiles obtained by the side Raman scattering lidar inversion with the upper-level water vapor and aerosol profiles obtained by the back Raman scattering lidar inversion to obtain the entire layer of water vapor and aerosol profiles to achieve blind-spot detection.

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