Carbon dioxide laser radar inversion method based on aerosol cooperative modulation

Abstract

The invention discloses a carbon dioxide laser radar inversion method based on aerosol cooperative modulation. The method comprises the following steps: firstly, acquiring multi-wavelength laser radar echo signals of a strong absorption wavelength, a weak absorption wavelength and an aerosol reference channel; inverting the extinction coefficient and the backscattering coefficient of the aerosol and characteristic parameters representing the micro-physical form of the aerosol; constructing a collaborative modulation model based on the radiation transmission model and calculating an aerosol collaborative optical modulation factor; and the carbon dioxide concentration profile is explicitly introduced into a differential absorption inversion equation, and multiple scattering and wavelength-related scattering differences caused by the aerosol are corrected, so that a high-precision carbon dioxide concentration profile is obtained through inversion. According to the method, the influence of high-concentration aerosol and complex weather conditions on carbon dioxide detection can be effectively weakened, the inversion stability and precision of the laser radar in near-earth and polluted environments are remarkably improved, and the method has a good engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric laser remote sensing technology, and particularly relates to a carbon dioxide lidar inversion method based on aerosol cooperative modulation. Background Technology

[0002] With the implementation of the "dual carbon" strategy, high-precision, all-weather vertical profile detection of atmospheric carbon dioxide concentration has become a key focus of environmental monitoring and meteorological research. Ground-based differential absorption lidar, with its high spatiotemporal resolution and all-weather observation capabilities, has become the primary means of detecting atmospheric carbon dioxide profiles.

[0003] The basic principle of ground-based differential absorption lidar is to emit a pair of laser beams with very similar wavelengths (strong absorption on-line wavelength and weak absorption off-line wavelength) into the atmosphere. By comparing the differences in the echo signals of the two laser beams with distance, the distribution information of carbon dioxide in the atmosphere can be obtained.

[0004] However, in real-world observation environments, especially under high aerosol load conditions such as urban and industrial areas, atmospheric aerosols significantly impact laser propagation. On one hand, aerosol-induced multiple scattering leads to a longer effective laser propagation path, weakening the idealized assumptions about the laser propagation path in differential absorption retrieval. On the other hand, the wavelength dependence of aerosol scattering characteristics introduces additional systematic differences between strong and weak absorption wavelengths, resulting in non-gas absorption error signals being mixed into the echo signal ratio. These effects are difficult to effectively characterize within the traditional differential absorption retrieval framework, leading to significant deviations in carbon dioxide retrieval results under high aerosol and complex scattering conditions.

[0005] Existing methods typically address aerosol effects through simplification assumptions or empirical corrections, but these methods struggle to simultaneously account for multiple scattering effects and wavelength-dependent scattering differences. Furthermore, they lack a unified characterization and constraint of aerosol microphysical properties, limiting the inversion accuracy and applicability of ground-based differential absorption lidar under complex atmospheric conditions. Therefore, it is necessary to propose a novel inversion method that explicitly introduces an aerosol cooperative modulation mechanism into the differential absorption inversion framework to systematically eliminate aerosol interference with carbon dioxide detection. Summary of the Invention

[0006] Objective of the Invention: To address the problems existing in the prior art, the objective of this invention is to provide a carbon dioxide lidar inversion method based on aerosol-coordinated optical modulation. This method constructs a coordinated modulation model characterizing the influence of aerosol scattering states on differential absorption inversion, explicitly introducing the optical path changes caused by aerosols into the carbon dioxide absorption inversion process, thereby improving the stability and accuracy of carbon dioxide inversion results under complex aerosol conditions.

[0007] Technical solution: The present invention provides a carbon dioxide lidar inversion method based on aerosol-coordinated optical modulation, comprising the following steps:

[0008] Step 1: Acquire the raw echo signals collected by the differential absorption lidar detection system. The signals include strong absorption wavelength (On-line) echo signals and weak absorption wavelength (Off-line) echo signals used for gas inversion, as well as echo signals from at least one aerosol reference channel detected synchronously with the aforementioned wavelengths.

[0009] Step 2: Based on the echo signal from the aerosol reference channel, calculate the aerosol optical parameters on the path under test using a lidar inversion algorithm. These parameters include at least the aerosol extinction coefficient and characteristic parameters reflecting the aerosol's microphysical morphology and scattering characteristics. Specifically, the characteristic parameters reflecting the aerosol's microphysical morphology and scattering characteristics mainly include lidar ratio and linear depolarization ratio.

[0010] Step 3: Based on the aerosol optical parameters obtained in Step 2, and using a preset cooperative modulation model, calculate the aerosol cooperative optical modulation factor Ψ(R) by using the aerosol optical parameters as a characterization index of the aerosol scattering state. Note that the aerosol optical parameters do not directly participate in the calculation of the ratio of strong to weak absorption wavelength echo signals.

[0011] Step 4: Substitute the calculated aerosol synergistic modulation factor Ψ(R) into the corrected differential absorption lidar equation. Specifically, during the calculation of the differential absorption optical thickness, a ln(Ψ(R)) correction term is introduced to subtract the non-gas absorption components introduced by the differences in aerosol multiple scattering and wavelength-dependent scattering, thereby obtaining the corrected differential absorption optical thickness, and using this as a basis to invert and obtain the carbon dioxide concentration profile.

[0012] Furthermore, in step 1, the strong absorption wavelength echo signal and the weak absorption wavelength echo signal are located at wavelengths of 1.57 μm or 2.05 μm, which are relatively ideal detection bands for atmospheric carbon dioxide absorption lines. The echo signal of the aerosol reference channel is used to synchronously detect the optical properties of aerosols, and its wavelength preferably includes at least one of 532 nm, 1064 nm, or 355 nm. The aerosol reference channel is also specially configured with a polarization beam splitter module. Specifically, this channel uses a polarization beam splitter to decompose the atmospheric echo signal into two orthogonal components, and simultaneously acquires the parallel component signal that is parallel to the polarization state of the emitted laser and the vertical component signal that is perpendicular to the polarization state of the emitted laser.

[0013] Furthermore, in step 2, the aerosol reference channel employs high-spectral-resolution lidar technology, and the specific steps are as follows:

[0014] S21. Inversion to obtain aerosol backscattering coefficients With extinction coefficient The calculation formula is as follows:

[0015]

[0016]

[0017] Where R is the distance. The molecular Rayleigh backscattering coefficient is calculated based on the standard atmospheric model. The known Rayleigh extinction coefficient of the molecule. The system gain ratio constant for the two channels; This is the echo signal from the molecular scattering channel. This represents the echo signal from the total scattering channel, which includes both aerosol and molecular scattering. In actual calculations, conventional corrections for the transmittance differences between molecular and aerosol spectra by filters must also be considered. The aerosol extinction coefficient obtained through the above calculations serves as one of the independent optical parameters required to find the Ψ(R) factor.

[0018] S22. Based on the extinction coefficient obtained independently above. and backscattering coefficient Directly calculate the actual lidar ratio at the current distance The calculation formula is as follows:

[0019]

[0020] Through the above calculations, the present invention can obtain a truth that requires no assumptions. And as one of the independent optical parameters required to find the Ψ(R) factor.

[0021] S23. Calculate the linear depolarization ratio The formula is as follows:

[0022]

[0023] Subscript and These represent two directions, one parallel and one perpendicular to the polarization direction of the emitted laser; and These are the parallel polarization component and the vertical polarization component of the atmospheric backscattered echo power received by the lidar at a distance R, respectively. Ψ(R) is the ratio of the gain constants of the two channels, i.e., the calibration factor, which is mainly affected by factors such as the depolarization effect of the lidar system and the detection efficiency of the two channels. The depolarization ratio calculated above is used as one of the independent optical parameters required to find the Ψ(R) factor.

[0024] Furthermore, in step 3, the cooperative modulation model is essentially a multidimensional lookup table, constructed based on a large-scale forward modeling of the radiative transfer model. It is used to characterize the cooperative modulation effect of aerosols on the effective propagation path and absorption weight of lasers under different aerosol optical conditions. The specific construction steps are as follows:

[0025] S31. Determine the radiative transfer model and parameter space: Select an atmospheric radiative transfer model that can describe the laser transmission process in a non-uniform medium, preferably using the Monte Carlo simulation method. This model is used to break through the single scattering assumption of traditional lidar equations and explicitly characterize the contribution of aerosol multiple scattering effects to the echo signal by tracing the scattering trajectory of photons in the atmosphere. In the construction of the parameter space, in order to eliminate parameter redundancy and optimize the model dimension, this invention is based on the physical constraint relationship between the aerosol extinction coefficient, backscattering coefficient, and lidar ratio (i.e., Selecting the aerosol extinction coefficient Compared to LiDAR As two independent variables characterizing the optical properties of aerosols; simultaneously, the linear depolarization ratio is introduced. As a third independent variable.

[0026] S32. Constructing aerosol parameter combinations and performing forward modeling: Within a preset parameter range, discretize and combine the aerosol optical parameters, including the aerosol extinction coefficient. LiDAR and linear depolarization ratio It should be noted that the aerosol extinction coefficient... LiDAR and linear depolarization ratio These parameters are used solely to characterize the aerosol scattering state and serve as the index dimension for a multidimensional lookup table. During lookup table construction, these parameters are not directly substituted into the calculation of the ratio of strong and weak absorption wavelength echo signals. Specifically, in the forward modeling stage, for each set of discretized aerosol parameter combinations, the set of parameters is treated as an assumed aerosol scattering state condition. While keeping the aerosol scattering state parameters unchanged, the radiative transfer model independently performs forward modeling calculations at both strong and weak absorption wavelengths to obtain the corresponding echo signals, and further calculates the ratio of the dual-wavelength echo signals from the differential absorption lidar.

[0027] S33. Calculation of Aerosol Cooperative Optical Modulation Factor: Based on the forward modeling results, Ψ(R) is defined as the ratio of the two-wavelength ratio under real atmospheric conditions to the two-wavelength ratio under the ideal single scattering assumption. The calculation formula is as follows:

[0028]

[0029] in, and Let represent the echo signals at distance R for the strong absorption wavelength (On-line) and weak absorption wavelength (Off-line), respectively. The subscript eff indicates the ratio of the actual simulated signal considering the aerosol multiple scattering effect, and the subscript ss indicates the ideal signal ratio considering only the single scattering condition (i.e., the assumption made by traditional differential absorption lidar). Based on this definition, the corresponding cooperative optical modulation factor can be calculated for different combinations of aerosol optical parameters.

[0030] S34. Establish a multidimensional lookup table: The independent variables determined in step S31 (i.e., aerosol extinction coefficients) are used to create a multidimensional lookup table. LiDAR and linear depolarization ratio Using the corresponding cooperative optical modulation factor Ψ(R) calculated in step S33 as the index dimension, a multidimensional cooperative modulation lookup table (LUT) is constructed using the corresponding output factor. Its general form is as follows:

[0031]

[0032] Where LUT represents a three-dimensional lookup mapping relationship constructed based on radiative transfer forward modeling.

[0033] Furthermore, in step S34, the multidimensional lookup table can be stored discretely, and the cooperative optical modulation factor under arbitrary aerosol conditions can be obtained by interpolation during the actual inversion process.

[0034] Furthermore, in step 4, the specific steps are as follows:

[0035] S41. First, calculate the corrected differential absorption optical thickness. The formula introduces the logarithm of the aerosol co-modulation factor Ψ(R) to remove the baseline drift caused by non-gas absorption. The calculation formula is as follows:

[0036]

[0037]

[0038] in, The definition of standard difference absorption optical thickness. The corrected differential absorption optical thickness. For reference distance.

[0039] S42. Using the corrected spatial rate of change of differential absorption optical thickness, invert the range-resolved carbon dioxide concentration profile. The inversion formula is as follows:

[0040]

[0041] in, For distance resolution, and This represents the absorption cross-section of carbon dioxide at strong / weak absorption wavelengths.

[0042] S43. For ease of comparison and application, the obtained carbon dioxide number density is usually... (Unit: m) -3 Convert to dry air mixing ratio (i.e., concentration) (Unit: ppm), the conversion formula is as follows:

[0043]

[0044] in, According to the ideal gas law The calculated total number density of air molecules, is the Boltzmann constant, approximately 1.38 × 10⁻⁶. -23 J / K.

[0045] The present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method of the present invention.

[0046] The present invention also discloses a computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implements the steps of the method of the present invention.

[0047] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0048] 1. This invention introduces an aerosol-synergistic optical modulation factor to explicitly modify the differential absorption lidar inversion equation, and incorporates the aerosol multiple scattering effect and wavelength-dependent scattering differences into a unified quantization framework, thereby effectively eliminating the systematic interference of aerosols on carbon dioxide differential absorption inversion.

[0049] 2. Compared with the existing technology that treats the aerosol effect as noise or a simple smoothing term, the present invention transforms the aerosol effect into a calculable and table-lookup-able cooperative modulation factor, which directly participates in the calculation process of differential absorption optical thickness, thus fundamentally avoiding the inversion bias caused by aerosols.

[0050] 3. This invention utilizes an independent aerosol reference channel to obtain aerosol optical parameters and constructs a pre-set cooperative modulation model. In the actual inversion process, only table lookup and interpolation are needed to obtain the modulation factor, which has low computational complexity, is easy to implement in engineering, and is suitable for long-term continuous automated operation.

[0051] 4. This invention can maintain high carbon dioxide inversion stability and reliability even under high aerosol concentration and complex meteorological conditions, which significantly expands the application range of differential absorption lidar in actual atmospheric environments. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the overall process of the carbon dioxide lidar inversion method based on aerosol-coordinated optical modulation.

[0053] Figure 2 This is a schematic diagram of the multiple scattering effect of atmospheric aerosols and the effective optical path stretching. The dashed arrows represent single scattering paths, and the solid broken arrows represent multiple scattering paths. Detailed Implementation

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0055] Figure 1 This is a flowchart of the overall process for the carbon dioxide lidar inversion method based on aerosol-coordinated optical modulation proposed in this invention, as follows: Figure 1 As shown, the carbon dioxide lidar inversion method based on aerosol-coordinated optical modulation in this embodiment includes the following steps:

[0056] Step 1: Acquire the raw echo signals collected by the differential absorption lidar detection system. The signals include strong absorption wavelength (On-line) echo signals and weak absorption wavelength (Off-line) echo signals used for gas inversion, as well as echo signals from at least one aerosol reference channel detected synchronously with the aforementioned wavelengths.

[0057] Step 2: Based on the echo signal from the aerosol reference channel, calculate the aerosol optical parameters on the path under test using a lidar inversion algorithm. These parameters include at least the aerosol extinction coefficient, backscattering coefficient, and characteristic parameters reflecting the aerosol's microphysical morphology. Specifically, the characteristic parameters reflecting the aerosol's microphysical morphology mainly include lidar ratio and linear depolarization ratio.

[0058] Step 3: Based on the various aerosol optical parameters obtained in Step 2, calculate the aerosol cooperative optical modulation factor Ψ(R) using a preset cooperative modulation model.

[0059] Step 4: Substitute the calculated aerosol synergistic modulation factor Ψ(R) into the corrected differential absorption lidar equation. Specifically, during the calculation of the differential absorption optical thickness, a ln(Ψ(R)) correction term is introduced to subtract the non-gas absorption systematic bias introduced by the differences in aerosol multiple scattering and wavelength-dependent scattering, thereby obtaining the corrected differential absorption optical thickness, and using this as a basis to invert and obtain the carbon dioxide concentration profile.

[0060] In specific implementation step 1, a composite detection system combining a ground-based differential absorption lidar and a hyperspectral resolution lidar is used to invert the vertical distribution of atmospheric carbon dioxide under urban environmental conditions. The lidar system can sequentially or synchronously emit a pair of laser pulses located near the carbon dioxide absorption line, preferably with an emission wavelength in the 1.57 μm band, including the strong absorption wavelength (On-line). The wavelength selected was 1572.024 nm, near the absorption peak of carbon dioxide, which is a weak absorption wavelength (off-line). Selecting 1572.150 nm as the weakest absorption wavelength, the corresponding echo signals are as follows: and Simultaneously, the system is also equipped with at least one aerosol reference detection channel, employing high spectral resolution technology with a wavelength selected at 532 nm, and includes a polarization beam splitting module to obtain parallel polarized echo signals. and vertically polarized echo signal The parallel component is further separated into molecular scattering channel signals by an iodine molecule filter. and the echo signal from the total scattering channel, which includes aerosol scattering and molecular scattering. .

[0061] When implementing step 2, the specific implementation steps are as follows:

[0062] S21. Utilizing the principle of high spectral resolution lidar, through the echo signal of the molecular channel... echo signal from the total scattering channel The aerosol backscattering coefficient can be directly obtained without assuming a lidar ratio. and extinction coefficient The calculation formula is as follows:

[0063]

[0064]

[0065] Where R is the distance. The molecular Rayleigh backscattering coefficient is calculated based on the standard atmospheric model. The known Rayleigh extinction coefficient of the molecule. This is the system gain ratio constant for the two channels. In the actual calculation, the difference in filter transmittance has been corrected.

[0066] S22. Based on the independent results of backscattering and extinction coefficients obtained in step S21, directly calculate the true lidar ratio at the current distance. The calculation formula is as follows:

[0067]

[0068] S23. Utilize the parallel polarization echo signal obtained from the lidar in step 1. and vertically polarized echo signal Calculate the linear depolarization ratio The calculation formula is as follows:

[0069]

[0070] in , which is the ratio of the gain constants of the two channels, i.e., the calibration factor, is mainly affected by factors such as the depolarization effect of the lidar system and the detection efficiency of the two channels.

[0071] In specific implementation step 2, the lidar ratio calculated above is used to characterize the equivalent absorption characteristics and particle size mode differences of aerosols, and serves as an important characterization parameter for aerosol scattering state, used to distinguish aerosol types with different scattering characteristics, thereby reflecting the differences in their forward scattering capabilities.

[0072] In specific implementation step 2, the linear depolarization ratio calculated above is used to characterize the geometric morphology of aerosols and is introduced into the cooperative modulation model construction process as a physical constraint parameter for scattering anisotropy. During the model construction process, the distribution characteristics of aerosol scattering direction and the range of values ​​of multiple scattering enhancement terms are constrained according to different depolarization ratio ranges to ensure the physical consistency and numerical stability of the cooperative optical modulation factor Ψ(R).

[0073] In specific implementation step 3, the aerosol synergistic modulation lookup table is used to characterize the synergistic modulation effect of aerosols on the effective propagation path and absorption weight of laser under different optical conditions. The specific construction steps are as follows:

[0074] S31. A Monte Carlo-based atmospheric radiative transfer model is selected to simulate the actual propagation process of laser light in an atmosphere containing aerosols. This model breaks through the single-scattering assumption of traditional lidar equations and can explicitly track the multiple scattering trajectories of photons along the propagation path, thereby obtaining a true echo signal that includes the multiple scattering effect. In constructing the parameter space, to eliminate parameter redundancy and optimize model dimensionality, the aerosol backscattering coefficient is taken into account. It can be determined by the aerosol extinction coefficient and lidar ratio Uniquely determined (i.e.) This invention selects the aerosol extinction coefficient. Compared to LiDAR As an independent variable characterizing the optical properties of aerosols, the linear depolarization ratio is also introduced. As a third independent variable constraining the particle shape and scattering direction distribution characteristics.

[0075] S32. Constructing aerosol parameter combinations and performing forward modeling: Within a preset parameter range, discretize and combine the aerosol optical parameters, including the aerosol extinction coefficient. LiDAR and linear depolarization ratio It should be noted that the aerosol extinction coefficient... LiDAR and linear depolarization ratio These parameters are used solely to characterize the aerosol scattering state and serve as the index dimension for a multidimensional lookup table. During lookup table construction, these parameters are not directly substituted into the calculation of the ratio of strong and weak absorption wavelength echo signals. Specifically, in the forward modeling stage, for each set of discretized aerosol parameter combinations, the set of parameters is treated as an assumed aerosol scattering state condition. While keeping the aerosol scattering state parameters unchanged, the radiative transfer model independently performs forward modeling calculations at both strong and weak absorption wavelengths to obtain the corresponding echo signals, and further calculates the ratio of the dual-wavelength echo signals from the differential absorption lidar.

[0076] The specific implementation steps S32 include the following steps:

[0077] (1) Discretization settings of the index dimensions of the lookup table: Considering the dynamic range of atmospheric aerosol changes and the nonlinear radiative transfer characteristics, this embodiment sets the following discrete nodes for the three independent index dimensions: aerosol extinction coefficient The coverage area is set to [0.01, 5] km. -1 Considering the high frequency of low extinction coefficients and the sensitivity of the Ψ factor to changes in the low-value region, a non-uniform discrete or logarithmic distribution can be used to set the nodes. For example, nodes can be set at 0.01, 0.05, 0.1, 0.2, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0 km. -1 LiDAR is more than The coverage area was set to [20, 100] sr, encompassing typical values ​​from marine aerosols (approximately 20 sr) to strongly absorbing smoke and dust (approximately 40-80 sr), using a uniform discretization method with a step size of 5 sr. The linear depolarization ratio δ was set to a coverage area of ​​[0.0, 0.40], using a uniform discretization method with a step size of 0.05. Based on the above node combination, the radiative transfer model was pre-run to calculate the Ψ value corresponding to each grid point, forming a three-dimensional data matrix.

[0078] (2) Forward modeling process: For each set of discrete aerosol parameter combinations The radiative transfer model was simulated in forward mode under both strong and weak absorption wavelengths. Under real scattering conditions, the Monte Carlo method was used to statistically analyze the photon energies returning to the receiving field of view. Under the assumption of ideal single scattering, the corresponding echo signal was calculated based on the same parameters. The cooperative optical modulation factor Ψ corresponding to this parameter combination was calculated based on the ratio between the dual-wavelength echo signals under real and ideal single scattering conditions and stored in the lookup table. The calculation formula is as follows:

[0079]

[0080] Wherein, the subscript eff represents the true signal ratio output from the Monte Carlo simulation, taking into account the effects of multiple scattering by aerosols and differences in wavelength correlation, and the subscript ss represents the ideal signal ratio considering only single scattering conditions (i.e., the assumption made by traditional differential absorption lidar). Through this definition, Ψ(R) quantitatively characterizes the systematic modulation amount of aerosols on the differential absorption echo signal ratio. The corresponding multidimensional cooperative modulation lookup table (LUT) is generally expressed as:

[0081]

[0082] Through the above construction process, in the inversion phase, the user only needs to input directly measurable data. , By using δ, the anisotropy of particle scattering can be implicitly constrained through a lookup table, thus achieving an effective combination of complex radiative transfer physics mechanisms and rapid engineering inversion.

[0083] (3) Interpolation calculation in real-time inversion: In the actual inversion process, for the real-time aerosol parameters obtained in step 2 ( , , The system uses trilinear interpolation to obtain Ψ(R): First, the cubic grid cell in the lookup table is determined based on the real-time parameter value, and the 8 adjacent discrete nodes surrounding the measurement point are identified; second, the distance weights from the measurement point to these 8 nodes are calculated; finally, the weights are used to perform a weighted average of the Ψ values ​​of these 8 nodes, thereby accurately calculating the cooperative optical modulation factor Ψ(R) at the current height.

[0084] By employing the aforementioned discretization and real-time interpolation strategies, this invention effectively controls the size of the lookup table and computational complexity while ensuring coverage of different aerosol states, thus meeting the requirements of real-time inversion applications.

[0085] When implementing step 4, the following specific steps are included:

[0086] S41. When calculating the corrected differential absorption optical thickness, first select a reference distance. In this embodiment, The initial height (e.g., 500 m) is selected when the geometric overlap factor of the lidar is 1 and the signal-to-noise ratio is greater than 10 to avoid the influence of near-field blind zones and transition zones. The corrected differential absorption optical thickness is calculated using a formula. The calculation formula is as follows:

[0087]

[0088]

[0089] in, Here is the definition of standard difference absorption optical thickness, and Ψ(R) is the cooperative modulation factor obtained from the table lookup in step 3.

[0090] S42. The carbon dioxide number density is inverted using the corrected spatial rate of change of the differential absorption optical thickness. Considering the random noise in the lidar echo signal, direct differential may cause oscillations in the inversion results. Therefore, before the inversion, it is preferable to... Spatial smoothing is performed (e.g., using a moving average with a sliding window length of 150m-300m or a Savitzky-Golay filter). After smoothing, the distance-resolved carbon dioxide number density is calculated using the following formula. :

[0091]

[0092] in, For distance resolution, and The absorption cross section of carbon dioxide at strong / weak absorption wavelengths. In this embodiment, these two parameters are calculated layer by layer from the real-time atmospheric temperature profile T(R) and pressure profile P(R) combined with the HITRAN spectral database to accurately reflect the pressure broadening and Doppler broadening effects at different altitudes.

[0093] In this embodiment, to ensure the real-time nature and convenience of the inversion, atmospheric temperature and pressure data are obtained through ground-based measurements and meteorological model extrapolation. First, the ground temperature is measured using an automatic weather station that is simultaneously observing with lidar. and Then, combined with the US Standard Atmosphere model (1976), ground-based measured values ​​were used. and Based on this, the temperature and pressure at different altitudes are derived using the hydrostatic equation and the wet adiabatic lapse rate. The formulas for calculating the atmospheric temperature profile T(R) and the pressure profile P(R) are as follows:

[0094]

[0095]

[0096] In calculating the atmospheric temperature profile, it is assumed that the air temperature in the troposphere decreases linearly with altitude (decline rate γ ≈ 6.5K / km). It is the acceleration due to gravity. , where is the dry air gas constant. It is worth noting that at suitable observation stations, the temperature and pressure profiles can also be obtained directly through inversion using a microwave radiometer observed at the same location, or by interpolation using global meteorological assimilation data from nearby times (such as ERA5 data), to further improve the calculation accuracy of the absorption cross section.

[0097] S43. For ease of comparison and application, the obtained carbon dioxide number density is usually... (Unit: m) -3 Convert to dry air mixing ratio (i.e., concentration) (Unit: ppm), the conversion formula is as follows:

[0098]

[0099] in, According to the ideal gas law The calculated total number density of air molecules, is the Boltzmann constant, approximately 1.38 × 10⁻⁶. -23 J / K.

[0100] This embodiment uses a 532 nm aerosol reference channel as an example for illustration. In practical applications, the cooperative modulation lookup table can also be constructed based on other visible or near-infrared aerosol reference bands, which does not affect the basic principle and technical effect of the method of the present invention.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any minor modifications, equivalent substitutions, or improvements made to the above embodiments based on the technical essence of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon dioxide lidar inversion method based on aerosol-coordinated modulation, characterized in that, Includes the following steps: Step S1: Acquire the strong absorption wavelength echo signal, the weak absorption wavelength echo signal, and the echo signal of at least one aerosol reference channel detected by the differential absorption lidar. Step S2: Based on the echo signal of the aerosol reference channel, calculate the aerosol optical parameters on the path to be tested. The parameters include the aerosol extinction coefficient and characteristic parameters reflecting the microphysical morphology and scattering characteristics of the aerosol. Step S3: Based on the aerosol optical parameters obtained in step S2, the aerosol optical parameters are used as a characterization index of the aerosol scattering state through a preset cooperative modulation model. The aerosol cooperative optical modulation factor Ψ(R) is calculated. The factor characterizes the non-gas absorption type systematic modulation amount of the aerosol multiple scattering effect and wavelength correlation difference on the ratio of strong and weak absorption wavelengths. Step S4: Substitute the aerosol-coordinated optical modulation factor Ψ(R) into the differential absorption lidar equation to correct the differential absorption optical thickness in order to compensate for the non-gas absorption component introduced by the modulation factor, thereby obtaining the corrected carbon dioxide concentration profile.

2. The carbon dioxide lidar inversion method based on aerosol co-modulation according to claim 1, characterized in that, In step S1, the strong absorption wavelength echo signal and the weak absorption wavelength echo signal are located at a wavelength of 1.57 μm or 2.05 μm; the wavelength of the echo signal of the aerosol reference channel includes at least one of 532 nm, 1064 nm or 355 nm.

3. The carbon dioxide lidar inversion method based on aerosol co-modulation according to claim 1, characterized in that, In step S2, the characteristic parameters reflecting the microphysical morphology and scattering properties of aerosols include lidar ratio and linear depolarization ratio. The aerosol reference channel uses a high-spectral-resolution lidar to directly or indirectly invert the aerosol extinction coefficient and backscattering coefficient, and calculates the true lidar ratio based on their ratio.

4. The carbon dioxide lidar inversion method based on aerosol synergistic modulation according to claim 3, characterized in that, The scattering process of aerosol scattering characteristics is described by a single scattering approximation or by a multiple scattering parameterization correction method based on equivalent scattering parameters.

5. The carbon dioxide lidar inversion method based on aerosol synergistic modulation according to claim 3, characterized in that, The lidar ratio is used to characterize the absorption characteristics and particle size mode differences of aerosols. Different lidar ratios correspond to different aerosol scattering state characteristics.

6. The carbon dioxide lidar inversion method based on aerosol co-modulation according to claim 3, characterized in that, The linear depolarization ratio is used to characterize the non-spherical nature of aerosol scattering and is introduced into the cooperative modulation model as a physical constraint parameter describing the aerosol scattering state.

7. The carbon dioxide lidar inversion method based on aerosol co-modulation according to claim 1, characterized in that, In step S3, the cooperative modulation model is a multidimensional lookup table, which is constructed by forward modeling the radiative transfer model under different combinations of aerosol optical parameters.

8. The carbon dioxide lidar inversion method based on aerosol co-modulation according to claim 7, characterized in that, The multidimensional lookup table uses aerosol extinction coefficient, lidar ratio, and depolarization ratio as index dimensions.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method of claim 1.

10. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method of claim 1.

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