Aerosol correction method and system suitable for high spectral resolution lidar

Abstract

The application discloses an aerosol correction method and system suitable for a hyperspectral resolution laser radar, and relates to the technical field of laser radar detection. Specifically, the method comprises the following steps: a first auxiliary detection channel and a second auxiliary detection channel specially added and containing iodine molecular absorption cells are used to filter out aerosol Mie scattering components in specific frequency laser echoes; pure first atmospheric temperature data is obtained based on data inversion of the auxiliary detection channels; atmospheric aerosol backscattering ratios are calculated in combination with reference channel data; the backscattering ratios are used to correct wind speed and temperature inversion models of the laser radar, and then corrected atmospheric wind speed and temperature data are obtained. The application aims to expand the minimum detection height of a hyperspectral resolution Rayleigh temperature and wind measurement laser radar by accurately quantifying and eliminating aerosol interference, and to realize high-precision synchronous measurement of wind speed and temperature in low-altitude and aerosol-rich areas.

Description

Aerosol Correction Methods and Systems for High-Spectral-Resolution LiDAR Technical Field

[0001] This invention relates to the field of lidar detection technology, and in particular to an aerosol correction method and system suitable for high spectral resolution lidar. Background Technology

[0002] Rayleigh thermo-wind lidar retrieves atmospheric wind and temperature field information by detecting Rayleigh scattering signals from atmospheric molecules. Traditional Rayleigh Doppler wind and temperature lidar typically emits a single-frequency laser. During measurement, they require atmospheric models or other atmospheric temperature measurement methods to obtain atmospheric temperature as known conditions for wind speed or temperature retrieval, thus they cannot achieve absolute measurement of atmospheric wind speed or temperature.

[0003] Hyperspectral resolution Rayleigh thermo- and wind-measuring lidar utilizes technologies such as iodine molecule absorption filters to simultaneously achieve absolute measurements of atmospheric wind speed and temperature without external reference point calibration, effectively solving the pain point of traditional Rayleigh lidar relying on external references. However, in the lower atmosphere or areas with high aerosol concentrations, atmospheric echo signals contain not only Rayleigh scattering components caused by molecular thermal motion but also strong aerosol Mie scattering components. Since the spectral characteristics of aerosol Mie scattering signals differ from those of Rayleigh scattering signals, and existing inversion algorithms typically struggle to completely separate these two signals over a large altitude range, hyperspectral resolution Rayleigh thermo- and wind-measuring lidar is highly susceptible to aerosol interference in low-altitude wind speed and temperature measurements. This interference significantly reduces inversion accuracy, causing measurement results to deviate from the true values, thus limiting the minimum effective detection altitude of this type of lidar system.

[0004] Therefore, how to accurately eliminate the influence of aerosol mi scattering signals on wind speed and temperature inversion while retaining the absolute measurement advantages of high-spectral-resolution radar, thereby expanding the low-altitude detection capability of radar, has become an urgent technical problem to be solved. Summary of the Invention

[0005] The main objective of this invention is to provide an aerosol correction method and system suitable for hyperspectral resolution lidar, aiming to accurately eliminate the influence of aerosol mi scattering signals on wind speed and temperature inversion while retaining the absolute measurement advantages of hyperspectral resolution lidar, thereby expanding the low-altitude detection capability of the lidar.

[0006] To achieve the above objectives, this invention proposes an aerosol correction method suitable for high spectral resolution lidar.

[0007] The lidar is configured to alternately emit pulsed lasers at three frequencies, including a frequency of [frequency missing]. The first laser;

[0008] The receiving optical path of the lidar includes a temperature and wind measurement detection channel, a reference channel, and a first auxiliary detection channel and a second auxiliary detection channel for auxiliary correction.

[0009] Both the first and second auxiliary detection channels include iodine molecule absorption cells, and the iodine molecule absorption cells of the first and second auxiliary detection channels are configured to filter out molecules at a frequency of [frequency missing]. The aerosol mi scattering component in the echo signal of the first laser; and the iodine molecule absorption cells of the first auxiliary detection channel and the second auxiliary detection channel have different atmospheric temperature response characteristics.

[0010] The method includes:

[0011] The initial atmospheric wind speed data obtained by the temperature and wind measurement detection channel based on the echo signal inversion is acquired. ;

[0012] Based on the first auxiliary detection channel and the second auxiliary detection channel, the frequency is... The echo signal of the first laser was detected, and the first atmospheric temperature data was obtained by inversion. ;

[0013] Based on the echo signal from the first auxiliary detection channel or the second auxiliary detection channel, the echo signal from the reference channel, and utilizing the first atmospheric temperature data The transmittance of the Rayleigh scattering echo signal was determined, and the atmospheric aerosol backscattering ratio was calculated. ;

[0014] Utilizing the atmospheric aerosol backscattering ratio The wind speed and temperature inversion model of the lidar is updated, and the echo signal of the temperature and wind measurement detection channel is processed using the updated wind speed and temperature inversion model to obtain corrected atmospheric wind speed data and atmospheric temperature data.

[0015] Preferably, the frequency is based on the first auxiliary detection channel and the second auxiliary detection channel. The echo signal of the first laser was detected, and the first atmospheric temperature data was obtained by inversion. The specific steps include:

[0016] Using the TentiS6 model and the measured transmittance curves of the first and second auxiliary detection channels, the transmittance at different atmospheric temperatures was calculated. The first auxiliary detection channel has a frequency of First transmittance of the Rayleigh scattering echo signal of the first laser And the second auxiliary detection channel with a frequency of The second transmittance of the Rayleigh scattering echo signal of the first laser ;

[0017] Calculate the first transmittance With the second transmittance ratio And use a fitting function to measure the ratio and the atmospheric temperature By fitting the data, the temperature inversion function is obtained. ;

[0018] Calculate the ratio of the echo signal intensity actually detected by the first auxiliary detection channel to the echo signal intensity actually detected by the second auxiliary detection channel, and substitute this ratio into the temperature inversion function. In the process, the first atmospheric temperature data is obtained. .

[0019] Preferably, the first auxiliary detection channel and the second auxiliary detection channel are located in a follow-up optical path connected to a tilting telescope;

[0020] The obtained temperature inversion function Following this step, it also includes: utilizing the initial atmospheric wind speed data For the temperature inversion function Make corrections;

[0021] The first atmospheric temperature data is obtained. The specific steps are as follows: Substitute the ratio of the echo signal intensities into the corrected temperature inversion function. In the process, the first atmospheric temperature data is obtained. .

[0022] Preferably, the TentiS6 model is a theoretical model based on the Boltzmann equation. The physical process described by the TentiS6 model is as follows: when a laser interacts with atmospheric molecules, the scattering spectrum contains Rayleigh scattering components caused by molecular thermal motion, and is superimposed with Brillouin scattering components generated by sound waves induced by density fluctuations.

[0023] Preferably, in the step of calculating the atmospheric aerosol backscattering ratio, the echo signal from the first auxiliary detection channel or the second auxiliary detection channel, the echo signal from the reference channel, and the first atmospheric temperature data are used. The transmittance of the Rayleigh scattering echo signal was determined, and the atmospheric aerosol backscattering ratio was calculated. In the step of calculating the atmospheric aerosol backscattering ratio The formula is:

[0024]

[0025] in, The echo signal detected by the reference channel. The echo signal detected by the first auxiliary detection channel or the second auxiliary detection channel. Based on the first atmospheric temperature data Determined Rayleigh scattering echo signal The selected auxiliary detection channel corresponds to the theoretical transmittance of the iodine molecule absorption cell. This refers to the channel constant of either the first auxiliary detection channel or the second auxiliary detection channel. is the channel constant of the reference channel.

[0026] Preferably, updating the wind speed and temperature inversion model of the lidar specifically involves calculating a two-dimensional calibration curve after aerosol correction; the two-dimensional calibration curve includes temperature ratio and wind speed ratio The calculation formula is as follows:

[0027]

[0028]

[0029] In the formula, The transmittance is the three-frequency laser Rayleigh scattering echo signal of the temperature and wind detection channel, wherein the transmittance is determined based on the known iodine molecule absorption cell transmission spectrum. The transmittance of the tri-frequency laser aerosol mi-scattered echo signal of the temperature and wind measurement detection channel is given by [the value of the transmittance]. The values ​​0, 1, and 2 correspond to the three frequencies of the three-frequency laser, respectively.

[0030] Preferably, the temperature and length of the iodine molecule absorption cell included in the first auxiliary detection channel are different from the temperature and length of the iodine molecule absorption cell included in the second auxiliary detection channel.

[0031] Preferably, the temperature and wind measurement detection channels include an eastward temperature and wind measurement detection channel and a northward temperature and wind measurement detection channel; the initial atmospheric wind speed data obtained from the temperature and wind measurement detection channels based on echo signals is then acquired. The specific steps are as follows: using the echo signals detected by the eastward temperature and wind measurement detection channel and the echo signals detected by the northward temperature and wind measurement detection channel, the initial eastward line-of-sight wind speed data and northward line-of-sight wind speed data are obtained by inversion.

[0032] This application also discloses a high spectral resolution lidar system, the system comprising:

[0033] The laser emitting unit is configured to alternately emit pulsed lasers at three frequencies, including one with a frequency of [frequency missing]. The first laser, the frequency of which is The first laser beam is located at the bottom of the iodine molecule absorption line.

[0034] The receiving unit includes a temperature and wind measurement detection channel, a reference channel, and a first auxiliary detection channel and a second auxiliary detection channel; wherein, both the first and second auxiliary detection channels include an iodine molecule absorption cell, and the iodine molecule absorption cell is configured to filter out the frequency of... The aerosol mi scattering component in the echo signal of the first laser, and the iodine molecule absorption cells of the first and second auxiliary detection channels have different atmospheric temperature response characteristics; and

[0035] The processing unit, connected to the receiving unit, is configured to perform the following operations:

[0036] The initial atmospheric wind speed data obtained by the temperature and wind measurement detection channel based on the echo signal inversion is acquired. ;

[0037] Based on the first auxiliary detection channel and the second auxiliary detection channel, the frequency is... The first atmospheric temperature data was obtained by inverting the echo signal of the first laser. ;

[0038] Based on the echo signal from the first auxiliary detection channel or the second auxiliary detection channel, the echo signal from the reference channel, and utilizing the first atmospheric temperature data The transmittance of the Rayleigh scattering echo signal was determined, and the atmospheric aerosol backscattering ratio was calculated. ;

[0039] Utilizing the atmospheric aerosol backscattering ratio The wind speed and temperature inversion model of the lidar is updated, and the echo signal of the temperature and wind measurement detection channel is processed using the updated wind speed and temperature inversion model to obtain corrected atmospheric wind speed data and atmospheric temperature data.

[0040] The above technical solution has the following advantages:

[0041] This invention adds an auxiliary detection channel to the receiving optical path, incorporating iodine molecule absorption cells with different atmospheric temperature response characteristics. Utilizing the laser frequency characteristics located at the bottom of the iodine molecule absorption spectral line, it effectively filters out aerosol Mie scattering components from the echo signal while retaining Rayleigh scattering signals. The purified temperature information obtained from the auxiliary channel is used to further calculate the atmospheric aerosol backscattering ratio, which is then substituted into the wind speed and temperature inversion model to correct the two-dimensional calibration curve, thereby eliminating the influence of aerosols on the accuracy of temperature and wind measurements. This application explicitly introduces the superposition relationship between Rayleigh and Mie scattering into the traditional inversion framework and uses the aerosol backscattering ratio to correct the temperature and wind speed ratios. When this ratio approaches 0, it degenerates into a traditional two-dimensional calibration curve; when aerosol levels increase, it can compensate for system biases, thus the mathematical form is consistent with the physical mechanism. This method not only maintains the advantage of high-spectral-resolution lidar requiring no external calibration but also significantly improves the measurement accuracy in low-altitude and aerosol-rich regions, effectively extending the minimum detection altitude of lidar. Attached Figure Description

[0042] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, wherein:

[0043] Figure 1 is a frequency diagram of the three-frequency laser emitted by the high-spectral-resolution Rayleigh thermo-wind lidar with aerosol correction function in an embodiment of the present invention.

[0044] Figure 2 is a schematic diagram illustrating the principle of measuring aerosol backscattering ratio in an embodiment of the present invention.

[0045] Figure 3 is a schematic diagram illustrating the principle of measuring atmospheric temperature using a double iodine bath in an embodiment of the present invention.

[0046] Figure 4 is a flowchart of the aerosol correction method for a high-spectral-resolution Rayleigh thermo-wind lidar with aerosol correction function according to an embodiment of the present invention.

[0047] Figure 5 is a schematic diagram of a high-spectral-resolution Rayleigh temperature and wind measurement lidar with aerosol correction function in an embodiment of the present invention.

[0048] Figure 6 shows the atmospheric wind speed measurement results in the simulation experiment without aerosol correction.

[0049] Figure 7 shows the atmospheric temperature measurement results in the simulation experiment without aerosol correction.

[0050] Figure 8 shows the atmospheric wind speed measurement results after aerosol correction using the method of this invention in the simulation experiment.

[0051] Figure 9 shows the atmospheric temperature measurement results after aerosol correction using the method of this invention in the simulation experiment. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0053] Example 1

[0054] This embodiment provides an aerosol correction method suitable for hyperspectral resolution Rayleigh thermo- and wind-measuring lidar. This method aims to address the problem of existing hyperspectral resolution Rayleigh thermo- and wind-measuring lidars being easily interfered with by aerosols in lower atmospheric detection. By introducing a specific auxiliary detection channel and combining it with an aerosol correction algorithm, this embodiment can accurately invert the atmospheric aerosol backscattering ratio and correct the wind speed and temperature inversion model accordingly. This significantly extends the minimum effective detection altitude of the lidar and achieves high-precision simultaneous measurement of atmospheric wind and temperature fields under aerosol conditions.

[0055] As shown in Figure 5, the method described in this embodiment relies on a high-spectral-resolution Rayleigh thermo- and wind-measuring lidar system. This system is configured to alternately emit pulsed lasers of three frequencies into the atmosphere. These three frequencies are respectively... , and (As shown in Figure 1). The frequency is... The first laser beam is optimized so that its center frequency is locked at the bottom of the iodine molecule absorption spectral line. At this frequency, the absorption of iodine molecules is extremely strong, effectively filtering out the aerosol Mie scattering components in the echo signal, while retaining only a portion of the Rayleigh scattering components caused by molecular thermal motion. This physical characteristic is the basis for aerosol correction in this embodiment. The receiving optical path of this lidar adds a first auxiliary detection channel and a second auxiliary detection channel to the existing temperature and wind measurement detection channel and reference channel. In this embodiment, the first auxiliary detection channel is specifically an eastward-facing temperature aerosol detection channel containing a high-temperature iodine molecule absorption cell, and the second auxiliary detection channel is specifically a northward-facing temperature aerosol detection channel containing a high-temperature iodine molecule absorption cell. Both auxiliary detection channels contain special iodine molecule absorption cells, and these two iodine molecule absorption cells are configured to have different atmospheric temperature response characteristics, for example, by setting different iodine cell temperatures or iodine cell lengths.

[0056] As shown in Figure 4, the aerosol correction method in this embodiment specifically includes the following steps:

[0057] First, the system executes step 1, which involves acquiring the initial atmospheric wind speed data derived from the echo signal by the temperature and wind measurement channels. In practice, after the lidar emits a three-frequency laser into the atmosphere, the eastward and northward laser receiving devices receive the echo signals from the atmosphere. These signals enter the eastward temperature and wind measurement detection channel containing a low-temperature iodine molecule absorption cell, the northward temperature and wind measurement detection channel containing a low-temperature iodine molecule absorption cell, and the corresponding eastward and northward reference channels. The processing unit uses the raw echo signals detected by these channels to calculate the initial eastward and northward line-of-sight wind speed data using a conventional Rayleigh-Doppler inversion algorithm. It should be noted that although the inversion results at this time have not yet undergone aerosol correction, under low wind speed conditions or due to... The special selection of frequency, this initial wind speed data It already has some reference value and is sufficient to be used for the correction of the temperature inversion function in subsequent steps.

[0058] Subsequently, the system executes step 2, which involves using the first and second auxiliary detection channels to detect frequencies of... The first atmospheric temperature data was obtained by inverting the echo signal of the first laser. This process utilizes a double iodine molecule absorption cell technology to eliminate aerosol interference (its basic principle is shown in Figure 3). Specifically, since the iodine molecule absorption cells in the first and second auxiliary detection channels both operate at high temperatures, they are sensitive to frequencies of [missing information - likely a specific frequency range]. The laser light has extremely high absorption and its transmittance is approximately zero. This means that the aerosol Mie scattering component in the echo signals entering these two channels is completely filtered out, and the signal received by the detector consists almost entirely of the Rayleigh scattering spectrum of atmospheric molecules. Since the width of the Rayleigh scattering spectrum is directly related to atmospheric temperature, and the iodine molecule absorption cells in these two auxiliary channels have different edge filtering characteristic curves due to differences in temperature or length, their transmittance responses to the same Rayleigh scattering spectrum are different.

[0059] In retrieving primary atmospheric temperature data In this embodiment, the TentiS6 model is used as the theoretical basis. The TentiS6 model is a theoretical model based on the Boltzmann equation, which accurately describes the physical process of laser-atmospheric molecular interaction. Specifically, the scattering spectrum includes not only Rayleigh scattering caused by molecular thermal motion but also Brillouin scattering components induced by density fluctuations. Using this model and pre-measured transmittance curves of eastward and northward temperature aerosol detection channels, the system calculates the transmittance at different atmospheric temperatures. Below, the first auxiliary detection channel is for a frequency of The first transmittance of the Rayleigh scattering echo signal of the laser and the second transmittance of the signal by the second auxiliary detection channel. Next, the ratio of these two transmittance values ​​is calculated. .because and The ratio varies with temperature, and this ratio changes accordingly. With atmospheric temperature There exists a monotonic correspondence between them. The system uses a fitting function to apply the ratios obtained from a series of theoretical calculations. and atmospheric temperature By performing fitting, a temperature inversion function can be constructed. .

[0060] In actual detection, if a tilted telescope is used for the detection optical path, such as the eastward or northward receiving optical path in this embodiment, atmospheric wind speed will cause a Doppler frequency shift, resulting in an overall shift of the Rayleigh scattering spectrum relative to the iodine molecule absorption spectrum. This shift will affect the calculation of transmittance. Therefore, this embodiment utilizes the initial atmospheric wind speed data obtained in the previous step. Temperature inversion function Corrections are made to eliminate frequency shift errors caused by wind speed. If the newly added first and second auxiliary detection channels are located in the follow-up optical path connected to the vertical telescope, whether or not to make corrections depends on the actual situation. After correction, the system calculates the ratio of the echo signal intensity actually detected by the first auxiliary detection channel to the echo signal intensity actually detected by the second auxiliary detection channel, and substitutes this measured ratio into the corrected temperature inversion function. In this way, high-precision first atmospheric temperature data can be calculated. Because this temperature data is based on a pure Rayleigh scattering signal that has had aerosol components filtered out, it is unaffected by aerosol pollution and accurately reflects atmospheric temperature.

[0061] Next, the system executes step 3, which involves using the echo signals from the first or second auxiliary detection channel and the echo signal from the reference channel, along with the first atmospheric temperature data. The transmittance of the Rayleigh scattering echo signal was determined, and the atmospheric aerosol backscattering ratio was calculated. (The measurement principle is shown in Figure 2). The core logic of this step lies in using the comparison between the pure signal and the mixed signal to determine the aerosol content. No iodine molecule absorption cells were installed in the eastward and northward reference channels, and the received echo signals... It simultaneously includes Rayleigh scattering signals from atmospheric molecules and Mie scattering signals from aerosols. The echo signals received by the eastward and northward temperature aerosol detection channels... As mentioned earlier, only Rayleigh scattering signals are included.

[0062] In this embodiment, the atmospheric aerosol backscattering ratio is calculated. The specific formula is:

[0063]

[0064] in, Indicates altitude; This represents the backscattering cross section of aerosol rice scattering; This represents the backscattering cross section of molecular Rayleigh scattering; The echo signal strength obtained from the reference channel detection; The echo signal strength obtained by the first auxiliary detection channel or the second auxiliary detection channel is specifically... or ; It utilizes the accurate atmospheric temperature data obtained in the previous step. The frequency calculated using the TentiS6 model is The theoretical transmittance of the Rayleigh scattering signal through the corresponding auxiliary channel iodine molecule absorption cell; This is the channel constant of the auxiliary detection channel; Here is the channel constant for the reference channel. Using this formula, the system can quantitatively separate the contribution of aerosols from the mixed signal, obtaining the atmospheric aerosol backscattering ratio as a function of altitude. .

[0065] Finally, the system executes step 4, which utilizes the atmospheric aerosol backscattering ratio. The wind speed and temperature inversion models of the lidar were updated, and the updated models were used to process the echo signals from the wind and temperature measurement channels to obtain corrected atmospheric wind speed and temperature data. In traditional inversion methods, assumptions are typically made... A value of 0 would lead to significant errors at lower altitudes where aerosols are abundant. This embodiment introduces... The two-dimensional calibration curve was recalculated. The aerosol-corrected two-dimensional calibration curve was obtained from the corrected temperature ratio. and wind speed ratio The composition and its calculation formulas are as follows:

[0066]

[0067]

[0068] In the above formula, The representative temperature and wind measurement detection channel has a frequency of The transmittance of the Rayleigh scattering echo signal of the laser, where The values ​​are 0, 1, and 2. The representative temperature and wind measurement detection channel has a frequency of The transmittance of the laser aerosol mi-scattered echo signal. By calculating... Substituting into the above formula, the system generates a corrected calibration curve that includes the influence of aerosols. By reprocessing the original echo signals from the temperature and wind measurement channels using this corrected curve, the final atmospheric wind speed data, now free from aerosol errors, can be obtained. and atmospheric temperature data .

[0069] Using the method described in this embodiment, the high-spectral-resolution Rayleigh thermo- and wind-measuring lidar not only retains its advantage of not requiring external reference calibration, but also overcomes the low-altitude detection blind zone, enabling high-precision simultaneous detection of wind speed and temperature even in the troposphere and lower stratosphere where aerosol concentrations are high. For example, in a simulation experiment, after calibration using this method, at an altitude of 30 km, the measurement uncertainties for temperature and wind speed can be controlled within 0.4 K and 0.35 m / s, respectively, verifying the effectiveness of the method.

[0070] Example 2

[0071] This embodiment further describes in detail a high-spectral-resolution Rayleigh scattering and wind measurement lidar system for implementing the above-described aerosol correction method. Through a specific hardware architecture design, this system can simultaneously acquire Rayleigh scattering signals used for conventional temperature and wind measurement, as well as pure Rayleigh scattering signals used for aerosol correction.

[0072] As shown in Figure 5, the lidar system described in this embodiment mainly consists of a laser emitting unit, a receiving unit, and a processing unit. The core task of the laser emitting unit is to generate and emit three narrowband pulsed lasers of specific frequencies into the atmosphere. This unit includes a timing control device, which serves as the timing command center for the entire system and is connected to the three-frequency generator, seed laser, pulsed laser amplifier, and the downstream receiving electronics. The timing control device, through precise frequency division and delay control, directs the three-frequency generator to sequentially and alternately generate seed lasers of three frequencies using acousto-optic frequency shifting technology. These three frequencies are respectively... , and The fundamental frequency light generated by the seed laser is frequency-stabilized by a laser frequency-locking device to ensure its frequency stability. The frequency is... The first laser was precisely positioned at the bottom of the iodine molecule absorption spectral line. This frequency selection is crucial for the subsequent use of the iodine molecule absorption cell to filter out aerosol signals.

[0073] The alternating seed lasers generated by the tri-frequency generator then enter the pulsed laser amplifier. Here, the seed lasers are chopped and amplified to form high-energy pulsed lasers. Finally, these high-energy pulsed lasers are directed by a laser emitting device into the atmosphere and the target area. The laser emitting device typically includes optical elements such as beam expanders and pointing mirrors to ensure that the laser beam has a good divergence angle and directionality.

[0074] The receiving unit is responsible for collecting atmospheric echo signals and performing spectroscopic processing. This embodiment employs two independent receiving paths, one eastward and one northward, to measure the vector wind field. The eastward laser receiving device receives atmospheric echo signals from the east, which are then distributed into three parallel detection channels: specifically, an eastward temperature and wind measurement detection channel containing a low-temperature iodine molecule absorption cell, an eastward reference channel without an iodine molecule absorption cell, and an eastward temperature aerosol detection channel containing a high-temperature iodine molecule absorption cell.

[0075] The eastward-facing temperature and wind measurement detection channel, containing a low-temperature iodine molecule absorption cell, uses the cell as a frequency discriminator for conventional wind speed and temperature detection. The eastward-facing reference channel, without an iodine molecule absorption cell, directly detects the echo signal to monitor laser energy fluctuations and provide a normalized reference. Most critically, the eastward-facing temperature aerosol detection channel contains a high-temperature iodine molecule absorption cell, which is the first auxiliary detection channel described in Example 1. This channel contains an iodine molecule absorption cell heated to a specific temperature, significantly higher than the iodine cell temperature in the temperature and wind measurement detection channel. This high-temperature setting broadens and deepens the absorption spectrum of iodine molecules, thus enabling the detection of frequencies ranging from [insert frequency here]. The aerosol Mie scattering component in the echo signal is filtered out with extremely high efficiency, allowing only Rayleigh scattering signals to pass through.

[0076] Similarly, the northward laser receiving device receives the northward echo signal and distributes it to the northward temperature and wind measurement detection channel containing a low-temperature iodine molecule absorption cell, the northward reference channel without an iodine molecule absorption cell, and the northward temperature aerosol detection channel containing a high-temperature iodine molecule absorption cell. The northward temperature aerosol detection channel containing a high-temperature iodine molecule absorption cell corresponds to the second auxiliary detection channel described in Example 1. To achieve atmospheric temperature inversion using the dual-channel ratio method, the iodine molecule absorption cells in the eastward and northward temperature aerosol detection channels containing high-temperature iodine molecule absorption cells are configured with different physical parameters. Specifically, the temperatures and lengths of these two iodine molecule absorption cells are different, resulting in differences in their response characteristic curves to changes in atmospheric temperature, thus providing the necessary independent variables for temperature inversion.

[0077] The optical signals output from each of the aforementioned channels converge at a photoelectric conversion device, where they are converted into electrical pulse signals. Subsequently, under the triggering of a timing control device, a photon counter and a data acquisition card perform distance-resolved counting of these electrical pulses. The acquired raw photon count data is ultimately transmitted to a data acquisition and processing computer. This computer, acting as the processing unit, incorporates a wind speed and temperature inversion model and an aerosol correction algorithm. It uses data from the eastward-facing temperature aerosol detection channel containing a high-temperature iodine molecule absorption cell and the northward-facing temperature aerosol detection channel containing a high-temperature iodine molecule absorption cell to invert the aerosol backscattering ratio, and based on this, dynamically corrects the two-dimensional calibration curve, ultimately outputting corrected atmospheric wind and temperature field data.

[0078] Example 3

[0079] This embodiment focuses on describing the physical model and specific calculation formulas used in the above method and system, especially how to achieve high-precision parameter inversion using the TentiS6 model and the corrected two-dimensional calibration curve.

[0080] The first atmospheric temperature data was retrieved using the first auxiliary detection channel and the second auxiliary detection channel. In this embodiment, the TentiS6 model is used as a dynamic model based on the Boltzmann equation. This model provides a detailed description of the microscopic mechanism of the interaction between laser and atmospheric molecules: when the laser is incident into the atmosphere, the scattering spectrum not only includes Rayleigh scattering components with Doppler broadening caused by molecular thermal motion, but also a Brillouin scattering component generated by sound waves induced by medium density fluctuations. This Brillouin scattering component gives the scattering spectrum a complex three-peak structure, the specific shape of which is closely related to atmospheric temperature and pressure. Compared to a simple Gaussian line model, the TentiS6 model can more accurately simulate the actual Rayleigh-Brillouin scattering spectrum, thereby significantly improving the accuracy of temperature inversion.

[0081] Obtaining the first atmospheric temperature data Subsequently, the system further calculated the atmospheric aerosol backscattering ratio. Subsequently, using this The system's wind speed and temperature inversion model is updated based on the values. In this embodiment, the core of the wind speed and temperature inversion model is the two-dimensional calibration curve, which describes the temperature ratio. and wind speed ratio The correlation with actual atmospheric temperature and wind speed. After introducing aerosol correction, the calculation formula for the two-dimensional calibration curve is revised as follows:

[0082]

[0083]

[0084] In the above formula, The values ​​0, 1, and 2 correspond to the three laser frequencies emitted by the system, respectively. , , . This indicates that the temperature and wind detection channels have a frequency of [frequency value missing]. The transmittance of the Rayleigh scattering echo signal generated by the laser is calculated by the TentiS6 model in combination with the actual optical path parameters. This indicates that the temperature and wind detection channels have a frequency of [frequency value missing]. The transmittance of the Mie scattering echo signal from the aerosol generated by the laser. Due to the extremely narrow Mie scattering spectrum, It usually depends on the transmittance of the iodine molecule absorption cell at the corresponding frequency.

[0085] The above formula shows that the aerosol backscattering ratio It directly participates as a correction term in the construction of temperature ratio and wind speed ratio. When aerosols are present in the atmosphere, If it is not zero, then if we still follow the traditional assumption... The formula will lead to the calculated and Deviation from the true value leads to significant errors in the inversion results. This embodiment measures in real time and substitutes the true value... The value that makes the calculated and It can accurately reflect atmospheric conditions, thus eliminating the interference of aerosols on the measurement.

[0086] To verify the effectiveness of the method described in this embodiment, simulation verification was performed based on actual system parameters. The simulation conditions were set as follows: time resolution 1 hour, altitude resolution 1 km, laser power 5 W, repetition frequency 50 Hz, and telescope aperture 760 mm. Inversion was performed using a standard atmospheric model and the measured transmittance curve of the iodine molecule absorption cell. As shown in Figures 6 and 7, without aerosol correction, the retrieved atmospheric temperature and wind speed showed significant deviations from the true values ​​in the low-altitude region, such as the altitude range of 15 km to 25 km. In particular, the temperature data showed a sharp increase in error as altitude decreased. However, after applying the aerosol correction method described in this embodiment, as shown in Figures 8 and 9, the retrieved atmospheric temperature and wind speed curves showed extremely high agreement with the true values. In areas where aerosols exist below 30 km, the measurement error was significantly suppressed, and the effective data extended to even lower altitude layers, proving that this correction method can significantly extend the minimum detection altitude of a hyperspectral resolution Rayleigh thermo-and-wind lidar.

[0087] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An aerosol correction method suitable for high spectral resolution lidar, characterized in that, The lidar is configured to alternately emit pulsed lasers at three frequencies, including a frequency of [frequency missing]. The first laser; the receiving optical path of the lidar includes a temperature and wind measurement detection channel, a reference channel, and a first auxiliary detection channel and a second auxiliary detection channel for auxiliary correction; both the first and second auxiliary detection channels contain iodine molecule absorption cells, and the iodine molecule absorption cells of the first and second auxiliary detection channels are configured to filter out the frequency of... Aerosol Mie scattering components in the echo signal of the first laser; Furthermore, the iodine molecule absorption cells of the first and second auxiliary detection channels have different atmospheric temperature response characteristics; the method includes: acquiring initial atmospheric wind speed data derived from the echo signal by the temperature and wind measurement detection channels. Based on the first auxiliary detection channel and the second auxiliary detection channel, the frequency is The echo signal of the first laser was detected, and the first atmospheric temperature data was obtained by inversion. Based on the echo signal from the first auxiliary detection channel or the second auxiliary detection channel, the echo signal from the reference channel, and utilizing the first atmospheric temperature data... The transmittance of the Rayleigh scattering echo signal was determined, and the atmospheric aerosol backscattering ratio was calculated. ； Utilizing the atmospheric aerosol backscattering ratio The wind speed and temperature inversion model of the lidar is updated, and the echo signal of the temperature and wind measurement detection channel is processed using the updated wind speed and temperature inversion model to obtain corrected atmospheric wind speed data and atmospheric temperature data.

2. The aerosol correction method according to claim 1, characterized in that, The frequency is based on the first auxiliary detection channel and the second detection channel. The echo signal of the first laser was detected, and the first atmospheric temperature data was obtained by inversion. The specific steps include: using the TentiS6 model and the measured transmittance curves of the first auxiliary detection channel and the second auxiliary detection channel, calculating the transmittance at different atmospheric temperatures. The first auxiliary detection channel has a frequency of First transmittance of the Rayleigh scattering echo signal of the first laser And the second auxiliary detection channel with a frequency of The second transmittance of the Rayleigh scattering echo signal of the first laser ; Calculate the first transmittance With the second transmittance ratio And use a fitting function to measure the ratio and the atmospheric temperature By fitting the data, the temperature inversion function is obtained. Calculate the ratio of the echo signal intensity actually detected by the first auxiliary detection channel to the echo signal intensity actually detected by the second auxiliary detection channel, and substitute this ratio into the temperature inversion function. In the process, the first atmospheric temperature data is obtained. 。 3. The aerosol correction method according to claim 2, characterized in that, The first auxiliary detection channel and the second auxiliary detection channel are located in a subsequent optical path connected to a tilting telescope; the obtained temperature inversion function Following this step, it also includes: utilizing the initial atmospheric wind speed data For the temperature inversion function Corrections are made; the first atmospheric temperature data is obtained. The specific steps are as follows: Substitute the ratio of the echo signal intensities into the corrected temperature inversion function. In the process, the first atmospheric temperature data is obtained. 。 4. The aerosol correction method according to claim 2, characterized in that, The TentiS6 model is a theoretical model based on the Boltzmann equation. The physical process described by the TentiS6 model is as follows: when a laser interacts with atmospheric molecules, the scattering spectrum contains Rayleigh scattering components caused by molecular thermal motion, and is superimposed with Brillouin scattering components generated by sound waves induced by density fluctuations.

5. The aerosol correction method according to claim 1, characterized in that, In the step of calculating the atmospheric aerosol backscattering ratio, the echo signal from the first auxiliary detection channel or the second auxiliary detection channel, the echo signal from the reference channel, and the first atmospheric temperature data are used. The transmittance of the Rayleigh scattering echo signal was determined, and the atmospheric aerosol backscattering ratio was calculated. In the step of calculating the atmospheric aerosol backscattering ratio The formula is: in, The echo signal detected by the reference channel. The echo signal detected by the first auxiliary detection channel or the second auxiliary detection channel. Based on the first atmospheric temperature data Determined Rayleigh scattering echo signal The selected auxiliary detection channel corresponds to the theoretical transmittance of the iodine molecule absorption cell. This refers to the channel constant of either the first auxiliary detection channel or the second auxiliary detection channel. is the channel constant of the reference channel.

6. The aerosol correction method according to claim 1, characterized in that, The update of the lidar's wind speed and temperature inversion model specifically involves calculating a two-dimensional calibration curve after aerosol correction; the two-dimensional calibration curve includes temperature ratio. and wind speed ratio The calculation formula is as follows: In the official The transmittance is the three-frequency laser Rayleigh scattering echo signal of the temperature and wind detection channel, wherein the transmittance is determined based on the known iodine molecule absorption cell transmission spectrum. The transmittance of the tri-frequency laser aerosol mi-scattered echo signal of the temperature and wind measurement detection channel is given by [the value of the transmittance]. The values ​​0, 1, and 2 correspond to the three frequencies of the three-frequency laser, respectively.

7. The aerosol correction method according to claim 1, characterized in that, The temperature and length of the iodine molecule absorption cell contained in the first auxiliary detection channel are different from those of the iodine molecule absorption cell contained in the second auxiliary detection channel.

8. The aerosol correction method according to claim 1, characterized in that, The temperature and wind measurement detection channels include an eastward temperature and wind measurement detection channel and a northward temperature and wind measurement detection channel; the initial atmospheric wind speed data obtained from the temperature and wind measurement detection channels based on echo signals is then acquired. The specific steps are as follows: using the echo signals detected by the eastward temperature and wind measurement detection channel and the echo signals detected by the northward temperature and wind measurement detection channel, the initial eastward line-of-sight wind speed data and northward line-of-sight wind speed data are obtained by inversion.

9. A high spectral resolution lidar system, characterized in that, The system includes: a laser emitting unit configured to alternately emit pulsed lasers of three frequencies, including a frequency of... The first laser, the frequency of which is The first laser is located at the bottom of the iodine molecule absorption spectrum line; the receiving unit includes a temperature and wind measurement detection channel, a reference channel, and a first auxiliary detection channel and a second auxiliary detection channel; wherein, both the first and second auxiliary detection channels contain an iodine molecule absorption cell, and the iodine molecule absorption cell is configured to filter out the frequency of... The aerosol mi scattering component in the echo signal of the first laser, and the iodine molecule absorption cells of the first and second auxiliary detection channels have different atmospheric temperature response characteristics; and a processing unit, connected to the receiving unit, configured to perform the following operations: acquire the initial atmospheric wind speed data retrieved by the temperature and wind measurement detection channels based on the echo signal. Based on the first auxiliary detection channel and the second auxiliary detection channel, the frequency is The first atmospheric temperature data was obtained by inverting the echo signal of the first laser. Based on the echo signal from the first auxiliary detection channel or the second auxiliary detection channel, the echo signal from the reference channel, and utilizing the first atmospheric temperature data... The transmittance of the Rayleigh scattering echo signal was determined, and the atmospheric aerosol backscattering ratio was calculated. ;Utilizing the atmospheric aerosol backscattering ratio The wind speed and temperature inversion model of the lidar is updated, and the echo signal of the temperature and wind measurement detection channel is processed using the updated wind speed and temperature inversion model to obtain corrected atmospheric wind speed data and atmospheric temperature data.

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