Temperature and mixing ratio retrieval method in high aerosol concentration scenarios

Abstract

The application provides a temperature and water vapor mixing ratio inversion method in a high-aerosol-concentration scene, and belongs to the technical field of laser atmospheric remote sensing data inversion. The application obtains EAE and aerosol extinction coefficients at 355nm wavelength, 532nm wavelength and 1064nm wavelength through iterative inversion; performs interpolation operation based on the aerosol extinction coefficients and the EAE to obtain aerosol extinction coefficients at 353nm wavelength, 354nm wavelength, 387nm wavelength and 407nm wavelength; calculates a first spectral attenuation correction term based on the aerosol extinction coefficients at 387nm wavelength and 407nm wavelength, and the first spectral attenuation correction term is used for inversion of water vapor mixing ratio; calculates a second spectral attenuation correction term based on the aerosol extinction coefficients at 353nm wavelength and 354nm wavelength, and the second spectral attenuation correction term is used for inversion of temperature. The application realizes accurate calculation of the spectral attenuation correction term by constraining the EAE, and finally realizes significant improvement in inversion accuracy of the temperature and the water vapor mixing ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of laser atmospheric remote sensing data inversion, and in particular to a method for inverting temperature and water vapor mixing ratio in a high aerosol concentration scenario. Background Art

[0002] Temperature and water vapor profiling (also known as thermodynamic profiling) play a key role in understanding the hydro-energy cycle and improving extreme weather forecasting capabilities. Their importance is growing, particularly in the context of global climate change. The World Meteorological Organization's requirements for lower-tropospheric profiling for nowcasting and short-term weather forecasting require that the uncertainty in temperature measurements be 0.5 K and the uncertainty in water vapor mixing ratio measurement be 5% at a vertical resolution of 100 m. However, existing technologies, such as radiosondes, microwave radiometers, and differential absorption spectroscopy, face significant challenges in both temporal and spatial resolution and measurement uncertainty, making it difficult to meet these stringent requirements.

[0003] As an active remote sensing technology with high temporal and spatial resolution, temperature and humidity Raman lidar has become an important tool for detecting temperature and water vapor mixing ratios in the lower to middle and upper troposphere. Limited by factors such as laser energy, receiving field of view, optical filter bandwidth, and detector sensitivity, temperature and humidity Raman lidar was initially used only for nighttime measurements and primarily for atmospheric research. In recent years, the rapid development of laser and optoelectronic technologies has significantly improved the performance of temperature and humidity Raman lidar, enabling significant advances in detection accuracy, operational capability, and system stability, thereby expanding its application potential in meteorological monitoring and environmental research.

[0004] Temperature and humidity Raman lidar signals are affected by attenuation caused by atmospheric molecules and aerosols during atmospheric propagation. Different wavelengths experience varying degrees of attenuation, resulting in differences in signal transmittance across different receiving channels. To mitigate inversion errors caused by these variations, spectral attenuation correction is required for the echo signals. The extinction coefficients of atmospheric molecules at different incident wavelengths can be calculated using standard atmospheric profiles, while the extinction coefficients of aerosols can be obtained using Raman methods. To incorporate spectral attenuation corrections in temperature and water vapor inversions, the extinction-related aerosol wavelength index (EAE) is used. However, conventional inversion methods often simplify the inversion calculations by assuming a fixed EAE value. For example, in temperature inversions, the EAE is assumed to be 0 (ignoring the spectral attenuation correction term), and in water vapor mixing ratio inversions, the EAE is assumed to be 1. While this assumption simplifies the inversion calculations, it can introduce additional errors due to the large EAE variations. The EAE is determined by the aerosol size distribution and complex refractive index and typically ranges between 0 and 2. For example, the EAE of volcanic ash is about 0.8, smoke aerosol is about 1.3, pollution aerosol is about 1.8, and the EAE of Central Asian dust is about 0.1. Therefore, the EAE assumption will affect the accuracy of temperature and water vapor mixing ratio retrieval.

[0005] In summary, there is an urgent need to develop a technical solution that can realize the constraints of EAE, and then accurately calculate the spectral attenuation correction term, and ultimately improve the inversion accuracy of temperature and water vapor mixing ratio. Summary of the Invention

[0006] In view of the above shortcomings of the existing technology, the present invention provides a temperature and water vapor mixing ratio inversion method under high aerosol concentration scenario to solve the problem of low temperature and water vapor mixing ratio inversion accuracy in the existing technology.

[0007] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0008] The present invention provides a method for inverting temperature and water vapor mixing ratio in a high aerosol concentration scenario, comprising the following steps:

[0009] (1) collecting elastic scattering and Raman scattering signals at multiple wavelengths, including 355 nm elastic scattering signal, 353 nm Raman scattering signal, 354 nm Raman scattering signal, 387 nm Raman scattering signal, 407 nm Raman scattering signal, 532 nm elastic scattering signal, 607 nm Raman scattering signal, 1064 nm elastic scattering signal and 1056 nm Raman scattering signal;

[0010] (2) Perform iterative inversion on the collected signals to obtain the extinction-related aerosol wavelength index (EAE) and the aerosol extinction coefficients at wavelengths of 355 nm, 532 nm, and 1064 nm;

[0011] (3) Based on the aerosol extinction coefficients at 355 nm, 532 nm, and 1064 nm, combined with EAE, interpolation calculations were performed to obtain the aerosol extinction coefficients at 353 nm, 354 nm, 387 nm, and 407 nm.

[0012] (4) Calculating a first spectral attenuation correction term based on the aerosol extinction coefficients at wavelengths of 387 nm and 407 nm, wherein the first spectral attenuation correction term is used to invert the water vapor mixing ratio;

[0013] A second spectral attenuation correction term is calculated based on the aerosol extinction coefficients at wavelengths of 353 nm and 354 nm, and the second spectral attenuation correction term is used to invert the temperature.

[0014] Furthermore, in step (2), before performing iterative inversion on the collected signal, data preprocessing is performed on the collected signal, and the preprocessing includes time zero point correction, dead time correction, overlap factor correction and background noise subtraction.

[0015] Furthermore, in step (3), based on the aerosol extinction coefficients at wavelengths of 355 nm, 532 nm, and 1064 nm, interpolation operation is performed in combination with EAE to obtain the aerosol extinction coefficients at wavelengths of 353 nm, 354 nm, 387 nm, and 407 nm. The calculation formula includes:

[0016] ;

[0017] in, EAE represents the aerosol wavelength index related to extinction; Indicates known wavelength aerosol extinction coefficient at ; Indicates the desired wavelength The aerosol extinction coefficient at .

[0018] Furthermore, in step (4), the calculation formula for calculating the first spectral attenuation correction term based on the aerosol extinction coefficient at a wavelength of 387 nm and a wavelength of 407 nm includes:

[0019] ;

[0020] in, represents the first spectral attenuation correction term; Indicates wavelength The molecular extinction coefficient at is calculated from the vertical profile of the temperature and pressure of the atmosphere; Indicates wavelength aerosol extinction coefficient at ; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength aerosol extinction coefficient at ; Indicates the distance resolution; Indicates the effective optical path height.

[0021] Furthermore, in step (4), the calculation formula for the first spectral attenuation correction term used to invert the water vapor mixing ratio includes:

[0022] ;

[0023] in, represents the water vapor mixing ratio; represents the water vapor calibration factor, which is obtained by calibrating the radiosonde measurement results; and They are represented as echo signals at wavelengths of 407nm and 387nm respectively.

[0024] Furthermore, in step (4), the calculation formula for calculating the second spectral attenuation correction term based on the aerosol extinction coefficient at a wavelength of 353 nm and a wavelength of 354 nm includes:

[0025] ;

[0026] in, represents the second spectrum attenuation correction term; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength aerosol extinction coefficient at ; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength The aerosol extinction coefficient at .

[0027] Furthermore, in step (4), the calculation formula for the second spectral attenuation correction term used to invert the temperature includes:

[0028] ; ;

[0029] in, It represents the ratio of the echo signals at wavelengths of 353 nm and 354 nm after correction by the second spectral attenuation correction term; and They are represented as echo signals at wavelengths of 353nm and 354nm respectively; Expressed as the second spectral attenuation correction term; Indicates temperature; 、 and It represents the temperature calibration factor, which is obtained by calibrating the radiosonde measurement results.

[0030] The present invention also provides a computer-readable storage medium storing a program, wherein when the program is executed by a processor, the method is implemented.

[0031] The present invention also provides a system comprising the computer-readable storage medium and a processor, wherein the method is implemented when the processor executes the program in the storage medium.

[0032] Compared with the prior art, the present invention is beneficial in that:

[0033] The present invention provides a temperature and water vapor mixing ratio inversion method for high aerosol concentration scenarios. By constraining EAE, the spectral attenuation correction term can be accurately calculated, and ultimately the inversion accuracy of temperature and water vapor mixing ratio can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the process of the temperature and water vapor mixing ratio inversion method based on high aerosol concentration scenario of the present invention;

[0035] Figure 2 The figure is a comparison of the inversion results of the method of the present invention and the traditional method. DETAILED DESCRIPTION

[0036] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Figure 1 The figure shows a flow chart of the temperature and water vapor mixing ratio inversion method based on a high aerosol concentration scenario provided by the present invention, which is as follows:

[0038] Step S1, collecting elastic scattering and Raman scattering signals of multiple wavelengths, the signals including the signals including 355nm elastic scattering signal, 353nm Raman scattering signal, 354nm Raman scattering signal, 387nm Raman scattering signal, 407nm Raman scattering signal, 532nm elastic scattering signal, 607nm Raman scattering signal, 1064nm elastic scattering signal and 1056nm Raman scattering signal. Specifically, a laser is used to emit pulsed light of wavelengths of 355 nm, 532 nm and 1064 nm, and a telescope is used to receive the returned backscattered light signal. Subsequently, the light signals of different wavelengths are separated by a spectroscopic system and detected by detectors respectively, and finally the intensity of the light signal of each wavelength is recorded using a data acquisition card.

[0039] Step S2: performing data preprocessing on the collected signals, wherein the preprocessing includes time zero point correction, dead time correction, overlap factor correction and background noise subtraction.

[0040] Among them, time zero point correction: due to the delay in the trigger time of the laser and the data acquisition card, the delay will cause the signal to shift in space, making the acquisition start time of the lidar signal inconsistent with the actual zero time. The purpose of time zero point correction is to remove the invalid signals collected due to the trigger delay, thereby ensuring that the signal spatial distance recorded by the lidar is consistent with the actual distance.

[0041] Dead time correction: In photon counting mode, when too many photons arrive at the detector at the same time, the detector may not be able to identify all of them, resulting in the measured photon count rate being lower than the actual value. Therefore, dead time correction is required to obtain the actual photon count rate reaching the detector. The calculation formula for dead time correction is as follows:

[0042] ;

[0043] in, Represents a received signal sequence; Indicates range gate; Indicates the detector dead time; Represents the dead time corrected signal sequence.

[0044] Overlap factor correction: Since the telescope's field of view and the laser's divergence angle partially overlap within a certain height range, the received signal is not a complete signal. The overlap factor correction function can correct the partial signal to a complete signal to ensure measurement accuracy. The calculation formula for the overlap factor correction is as follows:

[0045] ;

[0046] in, A signal sequence representing dead time correction; Indicates range gate; represents the overlap factor; represents the signal sequence after correction of the overlapping factor.

[0047] Background noise subtraction: Background noise primarily originates from the background light of the sky. During the LiDAR reception process, this noise enters the LiDAR field of view along with the laser echo signal, necessitating subtraction. Typically, laser light attenuates as it propagates through the atmosphere, making it difficult for far-field signals to detect Rayleigh scattering from atmospheric molecules and Mie scattering from aerosols. Therefore, this embodiment uses the average value of the last 2 km of the LiDAR far-field signal as background noise subtraction to improve signal quality.

[0048] Step S3: Iteratively invert the preprocessed signal to obtain the extinction-related aerosol wavelength index (EAE) and the aerosol extinction coefficients at wavelengths of 355 nm, 532 nm, and 1064 nm. Specifically, the iterative inversion process first assumes an initial EAE value as input and uses the Raman method to invert the extinction coefficient. Subsequently, the EAE is recalculated based on the inverted extinction coefficients of multiple bands and the error is calculated compared with the input EAE. If the error is greater than a set threshold and the number of iterations has not reached the maximum limit, the EAE is updated as the input for the next iteration. The above process is repeated until the error is less than a preset threshold (the preset threshold is 5% in this embodiment) or the maximum number of iterations is reached (the maximum number of iterations in this embodiment is 15). At this point, the iterative inversion ends, and the calculated EAE and the aerosol extinction coefficients at wavelengths of 355 nm, 532 nm, and 1064 nm are finally output.

[0049] Step S4: Based on the aerosol extinction coefficients at 355 nm, 532 nm, and 1064 nm, interpolation is performed in combination with EAE to obtain the aerosol extinction coefficients at 353 nm, 354 nm, 387 nm, and 407 nm. The interpolation formula is as follows:

[0050] ;

[0051] in, EAE represents the aerosol wavelength index related to extinction; Indicates known wavelength aerosol extinction coefficient at ; Indicates the desired wavelength The aerosol extinction coefficient at .

[0052] Step S5: Calculate the spectral attenuation correction term using the aerosol extinction coefficients at 387nm and 407nm, and then invert the water vapor mixing ratio. First, calculate the first spectral attenuation correction term based on the aerosol extinction coefficients at 387nm and 407nm, and the formula is as follows:

[0053] ;

[0054] in, represents the first spectral attenuation correction term; Indicates wavelength The molecular extinction coefficient at is calculated from the vertical profile of the temperature and pressure of the atmosphere; Indicates wavelength aerosol extinction coefficient at ; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength aerosol extinction coefficient at ; Indicates the distance resolution; Indicates the effective optical path height.

[0055] The first spectral attenuation correction term is then used to invert the water vapor mixing ratio using the following formula:

[0056] ;

[0057] in, represents the water vapor mixing ratio; represents the water vapor calibration factor, which is obtained by calibrating the radiosonde measurement results; and They are represented as echo signals at wavelengths of 407nm and 387nm respectively.

[0058] Step S6: Calculate the spectral attenuation correction term using the aerosol extinction coefficients at 353nm and 354nm, and then invert the temperature. First, calculate the second spectral attenuation correction term based on the aerosol extinction coefficients at 353nm and 354nm wavelengths, using the following formula:

[0059] ;

[0060] in, represents the second spectrum attenuation correction term; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength aerosol extinction coefficient at ; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength The aerosol extinction coefficient at .

[0061] The second spectral attenuation correction term is then used to invert the temperature, as follows:

[0062] ; ;

[0063] in, It represents the ratio of the echo signals at wavelengths of 353 nm and 354 nm after correction by the second spectral attenuation correction term; and They are represented as echo signals at wavelengths of 353nm and 354nm respectively; Expressed as the second spectral attenuation correction term; Indicates temperature; 、 and It represents the temperature calibration factor, which is obtained by calibrating the radiosonde measurement results.

[0064] like Figure 2 As shown in the figure, compared with the traditional method, in the altitude range of 0.5-3 km, the method provided by the present invention reduces the water vapor mixing ratio inversion error from 0.41 to 1. Reduced to 0.1 The temperature inversion error is reduced from 1.52 K to 0.31 K, which significantly improves the inversion accuracy of temperature and water vapor mixing ratio.

[0065] In summary, the present invention makes full use of multi-wavelength Raman technology and adopts an iterative inversion method to constrain EAE, thereby achieving accurate calculation of the spectral attenuation correction term, and ultimately significantly improving the inversion accuracy of temperature and water vapor mixing ratio.

[0066] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details of the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

Claims

1. A method for inverting temperature and water vapor mixing ratio in high aerosol concentration scenarios, characterized by: The following steps are involved: Collecting elastic scattering and Raman scattering signals at multiple wavelengths, the signals including 355 nm elastic scattering signal, 353 nm Raman scattering signal, 354 nm Raman scattering signal, 387 nm Raman scattering signal, 407 nm Raman scattering signal, 532 nm elastic scattering signal, 607 nm Raman scattering signal, 1064 nm elastic scattering signal, and 1056 nm Raman scattering signal; The collected signals were iteratively inverted to obtain the extinction-related aerosol wavelength index and the aerosol extinction coefficients at wavelengths of 355 nm, 532 nm, and 1064 nm. Based on the aerosol extinction coefficients at 355nm, 532nm and 1064nm wavelengths, combined with EAE interpolation calculation, the aerosol extinction coefficients at 353nm, 354nm, 387nm and 407nm wavelengths are obtained; Calculating a first spectral attenuation correction term based on aerosol extinction coefficients at wavelengths of 387 nm and 407 nm, wherein the first spectral attenuation correction term is used to invert the water vapor mixing ratio; A second spectral attenuation correction term is calculated based on the aerosol extinction coefficients at wavelengths of 353 nm and 354 nm, and the second spectral attenuation correction term is used to invert the temperature.

2. The temperature and water vapor mixing ratio inversion method under high aerosol concentration scenario according to claim 1 is characterized in that: The calculation formula for the first spectral attenuation correction term used to invert the water vapor mixing ratio includes: ； in, represents the water vapor mixing ratio; Indicates the water vapor calibration factor; and They are represented as echo signals at wavelengths of 407nm and 387nm respectively.

3. The temperature and water vapor mixing ratio inversion method under high aerosol concentration scenario according to claim 2 is characterized in that: The calculation formula of the first spectral attenuation correction term includes: ； in, represents the first spectral attenuation correction term; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength aerosol extinction coefficient at ; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength aerosol extinction coefficient at ; Indicates the distance resolution; Indicates the effective optical path height.

4. The temperature and water vapor mixing ratio inversion method under high aerosol concentration scenario according to claim 1 is characterized in that: The calculation formula for the second spectral attenuation correction term used to invert temperature includes: ； ； in, It represents the ratio of the echo signals at wavelengths of 353 nm and 354 nm after correction by the second spectral attenuation correction term; and They are represented as echo signals at wavelengths of 353nm and 354nm respectively; Expressed as the second spectrum attenuation correction term; Indicates temperature; 、 and Indicates the temperature calibration factor.

5. The temperature and water vapor mixing ratio inversion method under high aerosol concentration scenario according to claim 4 is characterized in that: The calculation formula of the two-spectral attenuation correction term includes: ； in, represents the second spectrum attenuation correction term; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength aerosol extinction coefficient at ; Indicates wavelength The molecular extinction coefficient at ; Indicates wavelength The aerosol extinction coefficient at .

6. The temperature and water vapor mixing ratio inversion method under high aerosol concentration scenario according to claim 1 is characterized in that: Based on the aerosol extinction coefficients at 355nm, 532nm, and 1064nm wavelengths, combined with EAE interpolation calculation, the aerosol extinction coefficients at 353nm, 354nm, 387nm, and 407nm wavelengths are obtained. The calculation formulas include: ； in, EAE represents the aerosol wavelength index related to extinction; Indicates known wavelength aerosol extinction coefficient at ; Indicates the desired wavelength The aerosol extinction coefficient at .

7. The temperature and water vapor mixing ratio inversion method under high aerosol concentration scenario according to claim 1 is characterized in that: Before performing iterative inversion on the collected signals, data preprocessing is first performed on the collected signals, and the preprocessing includes time zero point correction, dead time correction, overlap factor correction and background noise subtraction.

8. A computer-readable storage medium storing a program, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

9. A system, characterized in that: The method comprises the computer-readable storage medium and the processor as claimed in claim 8.

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