CN116794681A - Aerosol backscattering coefficient profile inversion method, device and equipment - Google Patents
Aerosol backscattering coefficient profile inversion method, device and equipment Download PDFInfo
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Abstract
The invention discloses an aerosol backscattering coefficient profile inversion method, device and equipment, wherein the method comprises the following steps: preprocessing the received backscattering signals, obtaining undisturbed backscattering signals, detecting cloud pollution, rejecting the undisturbed backscattering signals with cloud pollution according to a preset mode, obtaining target backscattering signals, carrying out Rayleigh fitting, and determining the optimal reference height; acquiring a backward scattering coefficient of the atmospheric molecules and generating a night radar ratio profile based on the optimal reference height; and finally, obtaining an aerosol backscattering coefficient profile based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar specific profile inversion. According to the invention, undisturbed backscattering signals with cloud pollution are removed in a preset mode, so that the effectiveness of the optimal reference height is improved, and then a night radar comparison profile is generated according to the optimal reference height and the atmospheric molecular backscattering coefficient, so that the inversion precision of the aerosol backscattering coefficient profile is further improved.
Description
Technical Field
The invention relates to the technical field of aerosol detection, in particular to an aerosol backscattering coefficient profile inversion method, device and equipment.
Background
Gaseous or liquid particulate matter (aerosols) suspended in the atmosphere have a direct and indirect effect on the radiation budget of the earth-atmosphere system. Knowledge of the spatial-temporal distribution of the optical and microscopic physical properties of an aerosol is crucial to assessing the effect of an aerosol on the radiation budget.
In the current stage of aerosol research, the atmospheric aerosol extinction coefficient profile, the backscattering coefficient profile and the depolarization ratio profile are used to characterize the particle size, shape, absorption and scattering characteristics of the aerosol, and are the main parameters for evaluating the optical and microscopic physical properties of the aerosol. The inversion of the aerosol depolarization ratio profile and the determination of the aerosol extinction coefficient profile are both dependent on the aerosol backscattering coefficient, so that the accurate inversion of the aerosol backscattering coefficient is the core for realizing the inversion of the aerosol optical parameters.
At present, a classical Fernald algorithm backward model is used for the inversion of the m-scattering channel aerosol backward scattering coefficient, but the Fernald algorithm needs four key inputs: 1. the reference height, the atmosphere at which is required to be relatively clean, the contribution of the aerosol to the backscattering is negligible, and under the situation that cloud exists, the unsuitable reference height can cause inversion failure of the extinction coefficient and the backscattering coefficient of the aerosol; 2. an aerosol backscattering coefficient at a reference height; 3. the radar ratio profile of the aerosol is usually assumed to be a certain value, but for different types of aerosols, the radar ratio is usually changed greatly, the inversion error of the backscattering coefficient of the aerosol can be more than 50% due to inappropriate radar ratio assumption during inversion, and the inversion effect on the extinction coefficient of the aerosol is larger; 4. the atmospheric molecular extinction coefficient and the atmospheric molecular backscattering coefficient, which can be calculated from the atmospheric temperature and pressure profile. Therefore, the three elements of cloud pollution, radar ratio hypothesis, and atmospheric temperature and pressure profile greatly limit the stability and accuracy of the aerosol backscatter coefficient profile inversion.
The foregoing is provided merely for the purpose of facilitating understanding of the technical scheme of the present invention and is not intended to represent an admission that the foregoing is related art.
Disclosure of Invention
The invention mainly aims to provide an aerosol backscattering coefficient profile inversion method, device and equipment, and aims to solve the technical problems of low stability and precision of aerosol backscattering coefficient profile inversion in the prior art.
To achieve the above object, the present invention provides an aerosol backscattering coefficient profile inversion method, comprising the steps of:
receiving a back scattering signal sent by a preset laser radar, and preprocessing the back scattering signal to obtain an undisturbed back scattering signal;
cloud pollution detection is carried out on the undisturbed back scattering signals, the undisturbed back scattering signals with the cloud pollution are removed according to a preset mode, and target back scattering signals are obtained;
determining an optimal reference height by performing rayleigh fitting on the target backscatter signal;
acquiring an atmospheric molecular backscattering coefficient, and generating a night radar ratio profile based on the optimal reference height and the atmospheric molecular backscattering coefficient;
and inverting based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile to obtain an aerosol backscattering coefficient profile.
Optionally, the receiving the backscatter signal sent by the preset lidar, and preprocessing the backscatter signal to obtain an undisturbed backscatter signal, includes:
receiving a backscattering signal sent by a preset laser radar, and denoising the backscattering signal to obtain a denoised backscattering signal;
performing smoothing filtering treatment on the denoised back scattering signal to obtain a filtered back scattering signal;
performing geometric overlap factor correction processing on the filtered back scattering signal to obtain a corrected back scattering signal;
and carrying out signal-to-noise ratio screening on the corrected backscatter signal to obtain an undisturbed backscatter signal.
Optionally, the signal-to-noise ratio screening of the corrected backscatter signal to obtain an undisturbed backscatter signal includes:
calculating the signal-to-noise ratio of the corrected back scattering signal to obtain a signal-to-noise ratio calculation result;
based on the signal-to-noise ratio calculation result, obtaining a corresponding height when the signal-to-noise ratio of the corrected back scattering signal is attenuated to a first preset value for the first time;
and eliminating the corrected backscatter signal with the corresponding height lower than a second preset value to obtain an undisturbed backscatter signal.
Optionally, the cloud pollution detection on the undisturbed backscatter signal, the undisturbed backscatter signal detected to have the cloud pollution is rejected according to a preset mode, and a target backscatter signal is obtained, including:
cloud pollution detection is carried out on the undisturbed back scattering signal, and when cloud pollution is detected, the cloud base height of the undisturbed back scattering signal is calculated;
and eliminating the undisturbed backscatter signals with the cloud bottom height lower than a third preset value to obtain target backscatter signals.
Optionally, before the acquiring the atmospheric molecular backscatter coefficient, generating a night radar profile based on the optimal reference height and the atmospheric molecular backscatter coefficient, the method further includes:
measuring the atmospheric temperature and the pressure profile in real time by a microwave radiometer;
an atmospheric molecular backscatter coefficient is determined based on the atmospheric temperature and the pressure profile.
Optionally, after the inversion is performed based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile, the method further includes:
inversion is carried out based on an aerosol depolarization ratio calculation formula and the aerosol backscattering coefficient profile to obtain an aerosol depolarization ratio profile;
the calculation formula of the aerosol depolarization ratio is as follows:
wherein, PDR aer For aerosol depolarization ratio, PDR mol Is the depolarization ratio of atmospheric molecules, beta aer Is the backscattering coefficient of the aerosol, PDR vol For large gas depolarization ratio, it is defined as the ratio of the corrected vertical channel backscatter signal to the backscatter signal of the parallel channel.
Optionally, after the inversion is performed based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile, the method further includes:
multiplying the aerosol backscattering coefficient profile with the night radar ratio profile to obtain an aerosol extinction coefficient profile.
In addition, to achieve the above object, the present invention also proposes an aerosol backscattering coefficient profile inversion apparatus, the apparatus comprising:
the signal receiving module is used for receiving a back scattering signal sent by a preset laser radar, and preprocessing the back scattering signal to obtain an undisturbed back scattering signal;
the pollution detection module is used for carrying out cloud pollution detection on the undisturbed backscatter signal, eliminating the undisturbed backscatter signal with the cloud pollution according to a preset mode, and obtaining a target backscatter signal;
the signal fitting module is used for determining the optimal reference height by carrying out Rayleigh fitting on the target back scattering signal;
the profile generation module is used for acquiring the atmospheric molecular backscattering coefficient and generating a night radar ratio profile based on the optimal reference height and the atmospheric molecular backscattering coefficient;
and the profile inversion module is used for inverting the profile based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile to obtain an aerosol backscattering coefficient profile.
In addition, to achieve the above object, the present invention also proposes an aerosol backscattering coefficient profile inversion apparatus, the apparatus comprising: a memory, a processor, and an aerosol backscatter coefficient profile inversion program stored on the memory and executable on the processor, the aerosol backscatter coefficient profile inversion program configured to implement the steps of the aerosol backscatter coefficient profile inversion method as described above.
In addition, in order to achieve the above object, the present invention also proposes a storage medium having stored thereon an aerosol backscattering coefficient profile inversion program which, when executed by a processor, implements the steps of the aerosol backscattering coefficient profile inversion method as described above.
The invention obtains undisturbed back scattering signals by receiving back scattering signals sent by a preset laser radar and preprocessing the back scattering signals; cloud pollution detection is carried out on the undisturbed backscatter signals, and the undisturbed backscatter signals with the cloud pollution are removed according to a preset mode, so that target backscatter signals are obtained; determining an optimal reference height by performing Rayleigh fitting on the target backscatter signal; acquiring an atmospheric molecular backscattering coefficient, and generating a night radar specific profile based on the optimal reference height and the atmospheric molecular backscattering coefficient; and inverting based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar specific profile to obtain the aerosol backscattering coefficient profile. According to the invention, the undisturbed backscatter signal with cloud pollution is removed according to the preset mode, so that the effectiveness of the optimal reference height is improved, a night radar profile is generated according to the optimal reference height and the atmospheric molecular backscatter coefficient, and finally inversion is performed based on the optimal reference height, the atmospheric molecular backscatter coefficient and the night radar profile to obtain an aerosol backscatter coefficient profile, and compared with the processing mode in the prior art that the radar ratio is assumed to be a constant value, the inversion precision and stability of the aerosol backscatter coefficient profile are further improved.
Drawings
FIG. 1 is a schematic diagram of the architecture of an aerosol backscattering coefficient profile inversion apparatus for a hardware operating environment in accordance with an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a first embodiment of an aerosol backscatter coefficient profile inversion method of the present invention;
FIG. 3 is a flow chart of a second embodiment of the aerosol backscatter coefficient profile inversion method of the present invention;
FIG. 4 is a flow chart of a third embodiment of an aerosol backscatter coefficient profile inversion method of the present invention;
FIG. 5 is a flow chart of an aerosol backscattering coefficient, aerosol extinction coefficient, and aerosol depolarization ratio profile data inversion in a third embodiment of the aerosol backscattering coefficient profile inversion method of the invention;
fig. 6 is a block diagram of a first embodiment of an aerosol backscatter coefficient profile inversion apparatus of the present invention.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an aerosol backscattering coefficient profile inversion apparatus of a hardware operation environment according to an embodiment of the present invention.
As shown in fig. 1, the aerosol backscattering coefficient profile inversion apparatus may include: a processor 1001, such as a central processing unit (Central Processing Unit, CPU), a communication bus 1002, a user interface 1003, a network interface 1004, a memory 1005. Wherein the communication bus 1002 is used to enable connected communication between these components. The user interface 1003 may include a Display, an input unit such as a Keyboard (Keyboard), and the optional user interface 1003 may further include a standard wired interface, a wireless interface. The network interface 1004 may optionally include a standard wired interface, a Wireless interface (e.g., a Wireless-Fidelity (WI-FI) interface). The Memory 1005 may be a high-speed random access Memory (Random Access Memory, RAM) or a stable nonvolatile Memory (NVM), such as a disk Memory. The memory 1005 may also optionally be a storage device separate from the processor 1001 described above.
Those skilled in the art will appreciate that the structure shown in fig. 1 does not constitute a limitation of the aerosol backscattering coefficient profile inversion apparatus, and may include more or fewer components than illustrated, or may combine certain components, or a different arrangement of components.
As shown in fig. 1, an operating system, a network communication module, a user interface module, and an aerosol backscatter coefficient profile inversion program may be included in a memory 1005 as one type of storage medium.
In the aerosol backscattering coefficient profile inversion apparatus shown in fig. 1, the network interface 1004 is mainly used for data communication with a network server; the user interface 1003 is mainly used for data interaction with a user; the processor 1001 and the memory 1005 in the aerosol backscattering coefficient profile inversion device of the present invention may be disposed in the aerosol backscattering coefficient profile inversion device, where the aerosol backscattering coefficient profile inversion device invokes an aerosol backscattering coefficient profile inversion program stored in the memory 1005 through the processor 1001, and executes the aerosol backscattering coefficient profile inversion method provided by the embodiment of the present invention.
The embodiment of the invention provides an aerosol backscattering coefficient profile inversion method, and referring to fig. 2, fig. 2 is a schematic flow chart of a first embodiment of the aerosol backscattering coefficient profile inversion method.
In this embodiment, the aerosol backscattering coefficient profile inversion method includes the following steps:
step S10: and receiving a back scattering signal sent by a preset laser radar, and preprocessing the back scattering signal to obtain an undisturbed back scattering signal.
It should be noted that, the execution body of the embodiment may be a computing service device with functions of data processing, network communication and program running, such as a tablet computer, a personal computer, a mobile phone, or other electronic devices capable of implementing the above functions. The present embodiment and the following embodiments will be described by way of example of an aerosol backscattering coefficient profile inversion apparatus (hereinafter referred to as inversion apparatus).
It can be understood that the preset laser radar can be a Raman-polarization laser radar, namely, a polarization signal detector is further arranged on the basis of the Raman laser radar, and the preset laser radar can be used for inverting an aerosol depolarization ratio profile to realize aerosol shape detection so as to identify the type of aerosol; the back scattering signal may be a signal reflected or scattered back by the detection target after a detection signal (i.e. a laser beam) is sent to the detection target by a preset laser radar, and mainly includes an atmospheric raman back scattering signal and a rice scattering back scattering signal; the undisturbed backscatter signal may be a signal obtained after preprocessing the backscatter signal, wherein the preprocessing may include subtraction of background noise, smoothing filtering, geometric overlap factor correction, and signal-to-noise ratio based signal screening.
Step S20: cloud pollution detection is carried out on the undisturbed back scattering signals, the undisturbed back scattering signals with the cloud pollution detected are removed according to a preset mode, and target back scattering signals are obtained.
It can be understood that the cloud pollution detection may be to detect whether a cloud exists in the target atmospheric environment, and when the cloud exists, that is, the cloud pollution exists, because in the situation that the cloud exists, the cloud easily has a negative effect on the subsequent data inversion, so that the accuracy and the effectiveness of the inversion result are not high; the target backscatter signal may be a signal that is retained after signal rejection is performed in a preset manner, or may be an undisturbed backscatter signal in which cloud contamination is not detected.
In a specific implementation, the inversion device performs cloud pollution detection on the undisturbed backscatter signal, if cloud pollution is detected, then calculates the height of the cloud base, if the height of the cloud base is lower than 3km, then eliminates the backscattered signal, wherein the height of the cloud base can be the height corresponding to the first time when the result of deriving the undisturbed backscatter signal is higher than 10, the thresholds (3 km and 10) are all empirical values, and certain deviation exists in threshold setting for different types of laser radars, and the embodiment is not limited to this.
Step S30: and determining the optimal reference height by carrying out Rayleigh fitting on the target backscatter signal.
It will be appreciated that the rayleigh fitting may be a fitting process conforming to a rayleigh distribution, the optimal reference height is the highest reference height after the selection condition is satisfied, the selection of the reference height requires that the extinction coefficient of the aerosol at the reference height is as small as possible, and the atmospheric environment in the reference height range is as pure as possible, the fewer aerosols are, the better, and the specific quantization measures of the selection condition are described in detail in the following third embodiment.
In a specific implementation, the inversion equipment performs corresponding Rayleigh fitting processing according to different types of target backscatter signals, so as to determine an optimal reference height; for example: for undisturbed backscatter signals without cloud pollution, the rayleigh fitting range selects the corresponding height when the signal-to-noise ratio is attenuated to 1 for the first time and the 2km range below the height, and for undisturbed backscatter signals with high cloud pollution (i.e. with the cloud base height not lower than 3 km), the rayleigh fitting range selects the range from the cloud base to the 2km range below the cloud base, and the above thresholds are all empirical values, which is not limited in this embodiment.
Step S40: and acquiring an atmospheric molecular backscatter coefficient, and generating a night radar ratio profile based on the optimal reference height and the atmospheric molecular backscatter coefficient.
It can be understood that the backscattering coefficient of the above-mentioned atmospheric molecules can be the proportion of light scattered to a specific angle in the atmospheric scattering process; the night radar profile may be a radar profile for a specific period of time (night), for example: night 00:00-05:00 or night 19:00-24:00, the radar ratio is the ratio of the extinction coefficient of the aerosol to the backscatter coefficient of the aerosol, without limitation.
In specific implementation, inversion equipment measures atmospheric temperature and pressure profile in real time through a microwave radiometer, determines an atmospheric molecular backscattering coefficient based on the atmospheric temperature and pressure profile, and finally generates a night radar ratio profile through the optimal reference height and the atmospheric molecular backscattering coefficient.
Step S50: and inverting based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile to obtain an aerosol backscattering coefficient profile.
In a specific implementation, the inversion device may perform inversion of the aerosol backscattering coefficient profile by using a Fernald algorithm backscattering coefficient model, where Lei Dabi in the Fernald algorithm brings in night radar specific profile calculation of the current day, and the aerosol backscattering coefficient at the reference height is set to the atmospheric molecular backscattering coefficient at the reference height, so as to obtain the aerosol backscattering coefficient profile.
In the embodiment, the backscattering signal is preprocessed by receiving the backscattering signal sent by the preset laser radar, so that an undisturbed backscattering signal is obtained; cloud pollution detection is carried out on the undisturbed backscatter signals, and the undisturbed backscatter signals with the cloud pollution are removed according to a preset mode, so that target backscatter signals are obtained; determining an optimal reference height by performing Rayleigh fitting on the target backscatter signal; acquiring an atmospheric molecular backscattering coefficient, and generating a night radar specific profile based on the optimal reference height and the atmospheric molecular backscattering coefficient; and inverting based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar specific profile to obtain the aerosol backscattering coefficient profile. According to the invention, the undisturbed backscatter signal with cloud pollution is removed according to the preset mode, so that the effectiveness of the optimal reference height is improved, a night radar profile is generated according to the optimal reference height and the atmospheric molecular backscatter coefficient, and finally inversion is performed based on the optimal reference height, the atmospheric molecular backscatter coefficient and the night radar profile to obtain an aerosol backscatter coefficient profile, and compared with the processing mode in the prior art that the radar ratio is assumed to be a constant value, the inversion precision and stability of the aerosol backscatter coefficient profile are further improved.
Referring to fig. 3, fig. 3 is a flowchart illustrating a second embodiment of the aerosol backscattering coefficient profile inversion method according to the present invention.
Based on the above first embodiment, in order to improve the effectiveness of the backscattered signal and reduce the interference, a second embodiment is proposed, where the step S10 specifically includes:
step S100: and receiving a back scattering signal sent by a preset laser radar, and denoising the back scattering signal to obtain a denoised back scattering signal.
In a specific implementation, the inversion equipment receives a backscattering signal sent by a preset laser radar, and performs denoising treatment, namely background noise removal, on the backscattering signal, so as to obtain a denoised backscattering signal, the background noise can be an average value of the backscattering signal at a position of 15-20km generally, at this time, the laser radar signal is completely attenuated, and the detected signal is sky background noise.
Step S200: and carrying out smoothing filtering treatment on the denoised back scattering signal to obtain a filtered back scattering signal.
In a specific implementation, the inversion equipment performs smoothing filtering processing on the denoised backscatter signal, so as to obtain a filtered backscatter signal, wherein the smoothing filtering can adopt a processing mode of 10-point median filtering.
Step S300: and performing geometric overlap factor correction processing on the filtered back scattering signal to obtain a corrected back scattering signal, wherein the geometric overlap factor correction can be performed by a method proposed by Ulla Wandinger et al.
Step S400: and carrying out signal-to-noise ratio screening on the corrected backscatter signal to obtain an undisturbed backscatter signal.
In a specific implementation, the inversion device performs signal-to-noise ratio calculation on the corrected backscatter signal to obtain a signal-to-noise ratio calculation result, and eliminates the corrected backscatter signal with a corresponding height lower than a second preset value when the signal-to-noise ratio of the corrected backscatter signal is attenuated to the first preset value for the first time based on the signal-to-noise ratio calculation result, so as to obtain an undisturbed backscatter signal, wherein the first preset value may be 1, the second preset value may be 3km, and the preset values are all empirical values.
In the embodiment, after the back scattering signal is subjected to pretreatment such as background noise removal, smooth filtering, geometric overlap factor correction, signal-to-noise ratio screening and the like, the effectiveness of the back scattering signal is effectively improved, and therefore the inversion precision and stability of the subsequent aerosol back scattering coefficient profile are improved.
Referring to fig. 4, fig. 4 is a schematic flow chart of a third embodiment of the aerosol backscattering coefficient profile inversion method according to the present invention.
Based on the above embodiments, in order to further improve the effectiveness and accuracy of the evaluation of the particle size, shape, absorption and scattering characteristics of the aerosol, the above step S50 further includes:
step S60a: and inverting based on an aerosol depolarization ratio calculation formula and the aerosol backscattering coefficient profile to obtain the aerosol depolarization ratio profile.
It can be appreciated that the aerosol depolarization ratio calculation formula may be a formula required for aerosol depolarization ratio profile inversion calculation, and specifically may be:
wherein, PDR aer For aerosol depolarization ratio, PDR mol Is the depolarization ratio of atmospheric molecules, beta aer Is the back-scattering coefficient of the aerosol,PDR vol for large gas depolarization ratio, it is defined as the ratio of the corrected vertical channel backscatter signal to the backscatter signal of the parallel channel.
Step S60b: multiplying the aerosol backscattering coefficient profile with the night radar ratio profile to obtain an aerosol extinction coefficient profile.
It will be appreciated that the atmospheric aerosol extinction coefficient profile, the backscattering coefficient profile and the depolarization ratio profile are the primary parameters used to characterize the particle size, shape, absorption and scattering properties of an aerosol, and to evaluate the optical and microscopic physical properties of an aerosol, wherein the aerosol backscattering coefficient profile is one of the characterizing indicators used to describe the attenuation of light by an aerosol.
Further, referring to fig. 5, a description will be given of the process of inversion of the aerosol backscattering coefficient, aerosol extinction coefficient, and aerosol depolarization ratio profile data.
The aerosol extinction and depolarization ratio profile inversion algorithm of the raman-polarized lidar illustrated in fig. 5 comprises the following steps:
firstly, preprocessing a Raman-polarization laser radar back scattering signal, including background noise subtraction, smooth filtering, geometric overlap factor correction, distance square correction and signal-to-noise ratio calculation. The background noise is usually the average value of the back scattering signal at 15-20km, at this time the laser radar signal is completely attenuated, and the detected signal is sky background noise; smoothing filtering can be 10-point median filtering; the geometric overlap factor correction may be performed by the method proposed by Ulla Wandinger et al; the signal-to-noise ratio (SNR) is calculated as:
wherein P is sig Is a laser radar back scattering signal, z is height, P bg For the background noise of the backscattered signal, the three times the standard deviation of the background noise in the range of 15-20km is taken as P bg 。
And step two, judging the corresponding height when the signal to noise ratio is attenuated to 1 for the first time according to the signal to noise ratio of the back scattering signal in the step one, and eliminating the back scattering signal if the height is smaller than 3 km.
And thirdly, carrying out cloud identification on the backscatter signals subjected to signal-to-noise ratio screening, if cloud pollution exists, carrying out cloud bottom height calculation, and if the cloud bottom height is lower than 3km, rejecting the backscatter signals. The cloud identification method is used for calculating the reciprocal of the preprocessed backscattering signal, when cloud pollution exists, the backscattering signal of the laser radar can be obviously enhanced, the characteristic can be further expanded in the deriving process, and the calculation formula is as follows:
wherein C is a derived backscatter signal, δz is a spatial resolution of the lidar, and is generally 7.5m, where considering that the backscatter signal after the lidar correction has a larger noise, a 5-point interval may be used herein, when the maximum value in C is greater than 10, cloud exists, and when the value of C is greater than 10 for the first time, the corresponding height is cloud low, and when the minimum value in C is less than-18 for the first time, the corresponding height is cloud top height, and this threshold is an empirical value, which is not limited in this embodiment, and there is a certain deviation in threshold setting for different types of lidars.
Step four, according to the step three, obtaining the high cloud%>3 km) of the contaminated backscatter signal and the cloud-free backscatter signal, performing rayleigh Li Nige on the two types of backscatter signals, selecting an optimal reference height, for the cloud-free backscatter signal, selecting a range of 2km below the corresponding height when the signal-to-noise ratio is first attenuated to 1, and for high cloud contamination, selecting a range of 2km from the cloud bottom to below the cloud bottom. The reference height is selected so that the extinction coefficient of the aerosol at the reference height is as small as possible, and the extinction coefficient of the atmospheric molecules at the reference height should be much greater than the extinction coefficient of the aerosol. Because the backscattering signal noise at the high position of the laser radar is larger, the window width of the Rayleigh fitting can be selected to be 300m, the sliding fitting is carried out for 30m in the selected range of the reference height,all suitable reference heights were found by two test conditions. Rayleigh fitting refers to laser radar normalized signal (P n ) And molecular backscattering coefficient (. Beta.) m ) The upper and lower boundaries of the fit are Z1 and Z2, respectively. Wherein the lidar normalized signal may be represented as
The molecular backscatter coefficient can be expressed as:
z in the above ref For reference height, beta mol Is the backscattering coefficient of atmospheric molecules, alpha mol Is the extinction coefficient of atmospheric molecules. Beta mol And alpha mol The two parameters are calculated using the atmospheric temperature and pressure profiles measured in real time by a microwave radiometer.
There are mainly two decisions for pure rayleigh conditions, the first one being a negligible aerosol extinction coefficient at the reference height (α aer ) The calculation formula is as follows:
generally, alpha aer The smaller this reference height, the purer it is, the more the pure rayleigh condition is satisfied; in practical application, if the calculated extinction coefficient value at the reference height is smaller than the uncertainty of the extinction coefficient, the pure Rayleigh condition is considered to be satisfied at the moment, and the test can be passed.
The second is the residual (R) of the test lidar normalized signal and the molecular backscatter coefficient:
R(z)＝P n (z)z 2 -β m (z)
if the laser radar normalized signal is less than the molecular backscatter coefficient, the reference height range is impure, contains aerosols, and cannot be used as a reference height, and other regions should be selected. The closer the laser radar normalized signal and the molecular backscattering coefficient are, the lower the residual error is, the better the consistency is, and the higher the quality of the pure Rayleigh condition in the test interval is. Since the laser radar normalized signal has high noise and the window width of Rayleigh fitting is 300m, in practical application, the sum of the mean value and standard deviation of the laser radar normalized signal at the reference height is required to be larger than the sum of the mean value and standard deviation of the molecular backscattering coefficient.
There may be many reference heights that meet both tests, and we generally choose the highest as the reference height.
And fifthly, acquiring an atmospheric temperature and pressure profile, and calculating an atmospheric molecular back scattering coefficient, wherein the atmospheric temperature and pressure profile is obtained from a real-time measurement result of a microwave radiometer.
And step six, inverting the night radar profile by using the method proposed by Ansmann et al [9] in combination with the step four and the step five.
Step seven, combining the step four, the step five and the step six, inverting the backward scattering coefficient of the aerosol by utilizing a Fernald algorithm backward model, wherein the radar ratio in the Fernald algorithm is carried into the radar ratio profile calculation at night, in practical application, the radar ratio profile of 00:00-12:00 is carried into calculation by using the radar ratio profile at night of 00:00-05:00, and the radar ratio profile of 12:00-24:00 is carried into calculation by using the radar ratio profile at night of 19:00-24:00; the aerosol backscattering coefficient at the reference height is set to the atmospheric molecular backscattering coefficient at this height; and multiplying the inverted aerosol backscattering coefficient by the night radar ratio profile to obtain the aerosol extinction coefficient profile.
And step eight, inverting the aerosol depolarization ratio according to the aerosol backscattering coefficient calculated in the step seven. The calculation formula of the aerosol depolarization ratio is as follows:
PDR in the above aer Is the airSol depolarization ratio, PDR mol For the depolarization ratio of atmospheric molecules, 0.014 beta is usually adopted aer Is the backscattering coefficient of the aerosol, PDR vol For large gas depolarization ratio, it is defined as the ratio of the corrected vertical channel backscatter signal to the backscatter signal of the parallel channel.
According to the embodiment, a set of microwave radiometers is added on the Raman-polarization laser radar, so that atmospheric temperature and pressure profile can be detected in real time and used for calculating the backscattering coefficient of atmospheric molecules, and the inversion accuracy of the Fernald algorithm is improved; secondly, synchronously inverting a radar ratio profile at night based on a Raman channel of the Raman-polarization laser radar, and bringing the radar ratio profile into a Fernald algorithm to further improve inversion accuracy of an aerosol backscattering coefficient profile, an aerosol extinction coefficient profile and an aerosol depolarization ratio profile; finally, cloud pollution detection, cloud low-altitude calculation and automatic reference altitude selection algorithms are added, and backscattering signals polluted by low cloud are filtered, so that a stable high-precision automatic inversion aerosol backscattering coefficient profile, an aerosol extinction coefficient profile and an aerosol depolarization ratio profile under high-cloud and cloud-free situations are realized.
In addition, the embodiment of the invention also provides a storage medium, wherein the storage medium is stored with an aerosol backscattering coefficient profile inversion program, and the aerosol backscattering coefficient profile inversion program realizes the steps of the aerosol backscattering coefficient profile inversion method when being executed by a processor.
Referring to fig. 6, fig. 6 is a block diagram illustrating a first embodiment of an aerosol backscattering coefficient profile inversion apparatus according to the invention.
As shown in fig. 6, an aerosol backscattering coefficient profile inversion apparatus according to an embodiment of the present invention includes: a signal receiving module 601, a pollution detecting module 602, a signal fitting module 603, a profile generating module 604 and a profile inverting module 605.
The signal receiving module is used for receiving a back scattering signal sent by a preset laser radar, and preprocessing the back scattering signal to obtain an undisturbed back scattering signal;
the pollution detection module is used for carrying out cloud pollution detection on the undisturbed back-scattering signals, eliminating the undisturbed back-scattering signals with the cloud pollution detected according to a preset mode, and obtaining target back-scattering signals;
the signal fitting module is used for determining the optimal reference height by carrying out Rayleigh fitting on the target backscattering signal;
the profile generating module is used for acquiring an atmospheric molecular back scattering coefficient and generating a night radar ratio profile based on the optimal reference height and the atmospheric molecular back scattering coefficient;
the profile inversion module is used for inverting based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile to obtain an aerosol backscattering coefficient profile.
In the embodiment, the backscattering signal is preprocessed by receiving the backscattering signal sent by the preset laser radar, so that an undisturbed backscattering signal is obtained; cloud pollution detection is carried out on the undisturbed backscatter signals, and the undisturbed backscatter signals with the cloud pollution are removed according to a preset mode, so that target backscatter signals are obtained; determining an optimal reference height by performing Rayleigh fitting on the target backscatter signal; acquiring an atmospheric molecular backscattering coefficient, and generating a night radar specific profile based on the optimal reference height and the atmospheric molecular backscattering coefficient; and inverting based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar specific profile to obtain the aerosol backscattering coefficient profile. According to the invention, the undisturbed backscatter signal with cloud pollution is removed according to the preset mode, so that the effectiveness of the optimal reference height is improved, a night radar profile is generated according to the optimal reference height and the atmospheric molecular backscatter coefficient, and finally inversion is performed based on the optimal reference height, the atmospheric molecular backscatter coefficient and the night radar profile to obtain an aerosol backscatter coefficient profile, and compared with the processing mode in the prior art that the radar ratio is assumed to be a constant value, the inversion precision and stability of the aerosol backscatter coefficient profile are further improved.
Other embodiments or specific implementations of the aerosol backscattering coefficient profile inversion apparatus of the present invention may refer to the above method embodiments, and will not be described herein.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.
The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.
From the above description of the embodiments, it will be clear to those skilled in the art that the above-described embodiment method may be implemented by means of software plus a necessary general hardware platform, but of course may also be implemented by means of hardware, but in many cases the former is a preferred embodiment. Based on such understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium (e.g. read-only memory/random-access memory, magnetic disk, optical disk), comprising instructions for causing a terminal device (which may be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to perform the method according to the embodiments of the present invention.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.
Claims (10)
1. A method of inverting an aerosol backscattering coefficient profile, the method comprising:
receiving a back scattering signal sent by a preset laser radar, and preprocessing the back scattering signal to obtain an undisturbed back scattering signal;
cloud pollution detection is carried out on the undisturbed back scattering signals, the undisturbed back scattering signals with the cloud pollution are removed according to a preset mode, and target back scattering signals are obtained;
determining an optimal reference height by performing rayleigh fitting on the target backscatter signal;
acquiring an atmospheric molecular backscattering coefficient, and generating a night radar ratio profile based on the optimal reference height and the atmospheric molecular backscattering coefficient;
and inverting based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile to obtain an aerosol backscattering coefficient profile.
2. The method of claim 1, wherein receiving the backscatter signal from the predetermined lidar, and preprocessing the backscatter signal to obtain an undisturbed backscatter signal, comprises:
receiving a backscattering signal sent by a preset laser radar, and denoising the backscattering signal to obtain a denoised backscattering signal;
performing smoothing filtering treatment on the denoised back scattering signal to obtain a filtered back scattering signal;
performing geometric overlap factor correction processing on the filtered back scattering signal to obtain a corrected back scattering signal;
and carrying out signal-to-noise ratio screening on the corrected backscatter signal to obtain an undisturbed backscatter signal.
3. The method of claim 2, wherein said signal-to-noise ratio screening said corrected backscatter signal to obtain an undisturbed backscatter signal, comprising:
calculating the signal-to-noise ratio of the corrected back scattering signal to obtain a signal-to-noise ratio calculation result;
based on the signal-to-noise ratio calculation result, obtaining a corresponding height when the signal-to-noise ratio of the corrected back scattering signal is attenuated to a first preset value for the first time;
and eliminating the corrected backscatter signal with the corresponding height lower than a second preset value to obtain an undisturbed backscatter signal.
4. The method of claim 1, wherein the performing cloud pollution detection on the undisturbed backscatter signal, rejecting the undisturbed backscatter signal in which the cloud pollution is detected in a preset manner, and obtaining a target backscatter signal includes:
cloud pollution detection is carried out on the undisturbed back scattering signal, and when cloud pollution is detected, the cloud base height of the undisturbed back scattering signal is calculated;
and eliminating the undisturbed backscatter signals with the cloud bottom height lower than a third preset value to obtain target backscatter signals.
5. The method of any of claims 1-4, wherein the acquiring atmospheric molecular backscatter coefficients, prior to generating a night radar profile based on the optimal reference altitude and the atmospheric molecular backscatter coefficients, further comprises:
measuring the atmospheric temperature and the pressure profile in real time by a microwave radiometer;
an atmospheric molecular backscatter coefficient is determined based on the atmospheric temperature and the pressure profile.
6. The method of claim 1, wherein the inverting based on the optimal reference height, the atmospheric molecular backscatter coefficient, and the night radar specific profile, after obtaining an aerosol backscatter coefficient profile, further comprises:
inversion is carried out based on an aerosol depolarization ratio calculation formula and the aerosol backscattering coefficient profile to obtain an aerosol depolarization ratio profile;
the calculation formula of the aerosol depolarization ratio is as follows:
wherein, PDR aer For aerosol depolarization ratio, PDR mol Is the depolarization ratio of atmospheric molecules, beta aer Is the backscattering coefficient of the aerosol, PDR vol For large gas depolarization ratio, it is defined as the ratio of the corrected vertical channel backscatter signal to the backscatter signal of the parallel channel.
7. The method of claim 6, wherein the inverting based on the optimal reference height, the atmospheric molecular backscatter coefficient, and the night radar specific profile, after obtaining an aerosol backscatter coefficient profile, further comprises:
multiplying the aerosol backscattering coefficient profile with the night radar ratio profile to obtain an aerosol extinction coefficient profile.
8. An aerosol backscattering coefficient profile inversion apparatus, the apparatus comprising:
the signal receiving module is used for receiving a back scattering signal sent by a preset laser radar, and preprocessing the back scattering signal to obtain an undisturbed back scattering signal;
the pollution detection module is used for carrying out cloud pollution detection on the undisturbed backscatter signal, eliminating the undisturbed backscatter signal with the cloud pollution according to a preset mode, and obtaining a target backscatter signal;
the signal fitting module is used for determining the optimal reference height by carrying out Rayleigh fitting on the target back scattering signal;
the profile generation module is used for acquiring the atmospheric molecular backscattering coefficient and generating a night radar ratio profile based on the optimal reference height and the atmospheric molecular backscattering coefficient;
and the profile inversion module is used for inverting the profile based on the optimal reference height, the atmospheric molecular backscattering coefficient and the night radar ratio profile to obtain an aerosol backscattering coefficient profile.
9. An aerosol backscattering coefficient profile inversion apparatus, the apparatus comprising: a memory, a processor, and an aerosol backscatter coefficient profile inversion program stored on the memory and executable on the processor, the aerosol backscatter coefficient profile inversion program configured to implement the steps of the aerosol backscatter coefficient profile inversion method of any one of claims 1 to 7.
10. A storage medium having stored thereon an aerosol backscatter coefficient profile inversion program, which when executed by a processor, implements the steps of the aerosol backscatter coefficient profile inversion method of any one of claims 1 to 7.
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