Disclosure of Invention
The invention provides a laser radar ratio region transmission method based on a novel foundation laser radar network, which can realize the balance between the precision of observation data of the laser radar network and the system cost on the premise of not increasing the cost of additional instruments.
A laser radar ratio area transmission method based on a novel foundation laser radar net comprises a high-spectral-resolution laser radar module arranged at the center and a plurality of meter-scattering laser radar modules arranged around the high-spectral-resolution laser radar module; the distance between each millimeter scattering laser radar module and the high spectral resolution laser radar module is different;
the high-spectral-resolution laser radar module comprises a high-spectral-resolution laser radar and a corresponding sunshine photometer which are cooperatively observed at the same position;
the meter scattering laser radar module comprises a meter scattering laser radar and a corresponding sunshine photometer which are arranged at the same position and used for cooperative observation;
the laser radar specific area transmission method comprises the following steps:
(1) selecting an O position and an aerosol type of an area to be researched, and arranging a novel foundation laser radar net by taking the O position as a center; respectively calculating the aerosol laser radar ratio observed by the high-spectral-resolution laser radar and the aerosol content observed by the corresponding sunshine photometer at the O position at the same moment;
(2) screening the aerosol laser radar ratio obtained in the step (1) and the data of the corresponding aerosol content by combining the historical data of the aerosol at the O position;
(3) after data screening, establishing a nonlinear regression model between the aerosol laser radar ratio at the O position and corresponding aerosol content data;
(4) calculating the content of aerosol observed by all sunlight meters within 500km around the O position by taking the O position as a center;
(5) substituting the aerosol content calculated in the step (4) into the nonlinear regression model in the step (3), and establishing a mathematical relation between relative distances (transmission distances) between a plurality of groups of different sunlight meter positions and a laser radar comparison relative error;
(6) and (5) determining the upper limit of the relative error of the laser radar ratio, and determining the transmission range applicable to the laser radar ratio regional transmission method by combining the established mathematical relation in the step (5).
In the step (1), the same time refers to data that the aerosol laser radar ratio and the aerosol content need to be selected at the integral time (0, 1 … 22, 23) of each day.
The calculation process of the aerosol laser radar ratio is as follows:
the high spectral resolution lidar obtains lidar equations for three channels:
in the formula (I), the compound is shown in the specification,
indicating that the lidar attenuated backscatter signal after system correction,
=1, 2 or 3;
representing the vertical channel backscatter coefficient of aerosol or atmospheric molecules,
represents vertical;
representing the parallel channel backscatter coefficients of aerosol or atmospheric molecules,
which represents a parallel,
and
respectively representing aerosol and atmospheric molecules;
and
respectively representing the detected initial height and the detected end height;
represents the extinction coefficient of an aerosol or atmospheric molecule;
represents the transmittance of an aerosol or molecular channel;
through the laser radar equation of the three channels
、
、
And
the aerosol laser radar ratio observed by the high spectral resolution laser radar is calculated by the following formula:
the calculation of the aerosol content is as follows:
the aerosol content is calculated by adopting an observation parameter inversion formula based on a sunshine photometer, which is proposed by Bahadur:
in the formula (I), the compound is shown in the specification,
represents the optical thickness of the absorbed aerosol, and can be obtained from the observation data of a solar photometer;
which represents the wavelength of the light emitted by the light source,
440, 675 or 880 nm;
which represents the reference wavelength(s) of the light,
440, 675 or 880 nm;
representing the optical thickness of the absorbing aerosol based on different aerosol contents at a reference wavelength,
is black carbon
Brown carbon
Or dust and sand
;
Which represents the absorption of the light in the angstrom index,
=1 or 2;
the optical aerosol thickness of the aerosol components is obtained by the following formula:
in the formula (I), the compound is shown in the specification,
represents the optical thickness of the aerosol of black carbon, brown carbon or sand dust;
representing the single scattering albedo of black carbon, brown carbon or sand dust; by calculation of
Account for
The content of the corresponding aerosol can be calculated and obtained.
In the step (2), the screening conditions for the aerosol laser radar ratio comprise height, backscattering ratio, aerosol depolarization ratio and laser radar ratioA range of (d); wherein the backscattering ratio
Deviation ratio of aerosol
The formula of (1) is as follows:
in the formula (I), the compound is shown in the specification,
and
respectively representing the depolarization ratio of the aerosol and the depolarization ratio of atmospheric molecules; the laser radar ratio value is an average value of data with the height of 0.5-4 km after screening by using the conditions of a backscattering ratio, an aerosol depolarization ratio and a laser radar ratio;
the screening condition for the aerosol content is to screen based on the month in which the O position was explored to have a higher aerosol content as a lower limit.
The specific process of the step (5) is as follows:
(5-1) optionally selecting the two sites of the sun photometer mentioned in the step (4), wherein one site is set as an M site, and the other site is set as an N site; converting the content of the aerosol observed by the two stations into a laser radar ratio through the nonlinear regression model in the step (3);
(5-2) assuming that the M site is taken as the center, and the longitude and latitude of the M point and the N point are respectively
And
the relative distance between the two stations is calculated M, N, as follows:
in the formula (I), the compound is shown in the specification,
representing the radius of the earth, respectively selecting the data of aerosol contents of two stations in the same hour, wherein the data is the data of the whole point time of each day, and the laser radar ratio of the M stations is used as the true value
The laser radar ratio of N sites is a reference value
Calculating the relative error of the laser radar ratio; the laser radar relative error and the transmission distance of the two stations are called a group of corresponding points;
(5-3) repeating the step (5-2), and calculating the laser radar relative error and relative distance between any two stations to obtain a plurality of groups of corresponding points;
and (5-4) establishing a mathematical relation between the laser radar specific relative error and the relative distance according to the plurality of groups of corresponding points calculated in the step (5-3).
In the step (6), an error transfer relation between a backscattering coefficient, an extinction coefficient and an aerosol laser radar ratio needs to be established, and the formula is as follows:
in the formula (I), the compound is shown in the specification,
indicating the total relative error of the aerosol lidar ratio,
representing the statistical standard deviation of the corresponding quantity; order to
And
respectively is
And
then the total relative error of the aerosol lidar ratio is solved as
(ii) a And (5) determining the applicable transmission range of the laser radar ratio region transmission method by combining the upper limit of the aerosol laser radar ratio relative error with the mathematical relation obtained in the step (5).
In addition, the specific number (more than or equal to 1) of the Mi scattering laser radars can be arranged according to the station positions and the number of the sunshine photometers existing in the range of 500km by taking the high-spectral-resolution laser radars as the center.
Compared with the prior art, the invention has the following beneficial effects:
1. the novel laser radar network provided by the invention realizes the balance between the observation data precision and the system cost of the laser radar network on the premise of not increasing the cost of additional instruments, fully exerts the respective advantages of advanced laser radars and meter scattering laser radars, and can promote the large-scale deployment of the laser radar network in China;
2. the method has simple thought, provides an important thought for realizing the precision transmission of the parameters between the laser radar networks, and has strong popularization value.
Detailed Description
The invention will be described in further detail below with reference to the drawings and examples, which are intended to facilitate the understanding of the invention without limiting it in any way.
As shown in fig. 1, the novel ground-based lidar network in this embodiment includes a high spectral resolution lidar module 1 and a plurality of millimeter-scattering lidar modules 2. The high spectral resolution laser radar module 1 mainly comprises a combination of a high spectral resolution laser radar and a sun photometer, and the meter scattering laser radar module 2 mainly comprises a combination of a meter scattering laser radar and a sun photometer. High spectral resolution lidar module 1 is arranged at the central position, meter scattering lidar module 2 is arranged at the surrounding position, and the distances between different meter scattering lidar modules 2 and high spectral resolution lidar module 1 are different.
As shown in fig. 2, a lidar specific area transmission method based on a novel ground-based lidar network includes the following steps:
s1: the place selected in this example is seoul university, seoul, korea, whose latitude and longitude is (126.95E, 37.56N). The high spectral resolution laser radar is selected as 'AHSRL' developed by Wisconsin university. The time period of the data is selected to be 2016.1.1-2018.12.31, the time-space resolution of the data is 1 hour (hour of the whole point of the day, 0, 1 … 22, 23 hours) and 7.5m, and the height range is 0-10 km. The AHSRL high spectral resolution lidar can obtain lidar equations for three channels:
in the formula (I), the compound is shown in the specification,
indicating that the lidar attenuated backscatter signal after system correction,
i=1, 2 or 3;
representing the vertical channel backscatter coefficient of aerosol or atmospheric molecules,
represents vertical;
representing the parallel channel backscatter coefficients of aerosol or atmospheric molecules,
which represents a parallel,
and
respectively representing aerosol and atmospheric molecules;
and
respectively representing the detected initial height and the detected end height;
to representExtinction coefficient of aerosol or atmospheric molecules;
represents the transmittance of an aerosol or molecular channel;
through the laser radar equation of three channels can be solved
、
、
And
the aerosol laser radar ratio observed by the AHSRL high spectral resolution laser radar can be obtained by the following calculation:
in this embodiment, the AERONET site name is selected as "Yonseii University". The solar photometer model is CE318, which is manufactured by CIMEL electronics of france. The selected time period is 2016.1.1-2018.12.31. The data selected were 1.5 levels of AERONET version 3 and were averages at each hour time (0, 1 … 22, 23) which had to be the same time as the selection of the lidar ratio described above. The aerosol content is calculated by adopting an inversion formula based on observation parameters of a sunshine photometer, which is proposed by American scientist Bahadur:
in the formula (I), the compound is shown in the specification,
representing the optical thickness of the absorbed aerosol, which can be measured from a solar photometerObtaining;
which represents the wavelength of the light emitted by the light source,
440, 675 or 880 nm;
which represents the reference wavelength(s) of the light,
440, 675 or 880 nm;
representing the optical thickness of the absorbing aerosol based on different aerosol contents at a reference wavelength,
is Black carbon (Black carbon,
) Brown carbon (Brown carbon,
) Or dust (a)
);
Which represents the absorption of the light in the angstrom index,
=1 or 2; in the present embodiment, the first and second electrodes are,
、
and
the values are respectively 0.55 +/-0.24, 4.55 +/-2.01 and 2.20 +/-0.50;
、
and
the values are respectively 0.85 plus or minus 0.40, 0 and 1.15 plus or minus 0.50.
The optical aerosol thickness of the aerosol components is obtained by the following formula:
in the formula (I), the compound is shown in the specification,
represents the optical thickness of the aerosol of black carbon, brown carbon or sand dust;
the values of the single scattering albedo of black carbon, brown carbon or sand dust are 0.480, 0.772 and 0.870 respectively in this embodiment.
By calculation of
Account for
The content of the corresponding aerosol can be calculated and obtained.
S2: in this embodiment, the sand aerosol is selected, and the screening conditions for the sand lidar ratio include the height, the backscattering ratio, the aerosol depolarization ratio, and the lidar ratio range. Wherein the backscattering ratio
Deviation ratio of aerosol
The formula of (1) is as follows:
in the formula (I), the compound is shown in the specification,
and
respectively representing the depolarization ratio of the aerosol and the depolarization ratio of the atmospheric molecules. Wherein
Can be solved by radar equations of three channels of the high-spectral-resolution laser radar in the embodiment
The value was 0.0143. The screening conditions were as follows: the height is 0.5-4 km; backscatter ratio: 1.2-10; aerosol depolarization ratio: 0.15 to 0.3; laser radar ratio: 30 to 90 Sr. The laser radar ratio value is an average value of data with the height of 0.5-4 km after screening conditions of a backscattering ratio, an aerosol depolarization ratio and a laser radar ratio.
The average value of the dust content of the Yangshan university in 3 and 4 months per year in the period of 2016.1.1-2018.12.31 is calculated, and the calculation result of the embodiment is 21.6%. For convenience, the screening condition of the present example for the content of sand dust is required to be more than 20%.
Through screening, the present embodiment obtains a value 400 group of the sand-dust lidar ratio and the sand-dust content.
S3: as shown in fig. 3, a non-linear regression model between the sand-dust lidar ratio at the O position and 400 groups of data with the screened corresponding content is established. The embodiment adopts a quadratic polynomial fitting method, the decision coefficient of the fitting is 0.78, and the fitting has strong correlation.
S4: considering the data volume problem, the present example selects six sites of maryland center (76.61W, 39.28N), einz germany (8.30E, 50.00N), carl pomtra france (5.06E, 44.08N), taihu china (120.22E, 31.42N), beijing china (116.38E, 39.98N), and korean university of extension (126.95E, 37.56N) as the center, the data selection time ranges from 2001.1.1 to 2021.3.31, and calculates the content of dust aerosol observed by all the sun photometers at every whole time (0, 1 … 22, 23) within 500km around each center site. In this embodiment, a total of 63 solar photometer sites are selected. In addition, as described in step S2, the present embodiment also requires the screening condition for the content of sand dust in step S4 to be more than 20%.
S5: the embodiment specifically implements the following process in this step:
s5-1: two solar photometric sites mentioned in the step S4 are arbitrarily selected, one of which is set as an M site, and the other is set as an N site. Converting the sand and dust content observed by the two stations into a laser radar ratio through the nonlinear regression model in the step S3;
s5-2: suppose that the M site is taken as the center, and the longitude and latitude of the M point and the N point are respectively
And
the relative distance between the two stations is calculated M, N, as follows:
in the formula (I), the compound is shown in the specification,
representing the radius of the earth. Selecting the data of aerosol contents of the two stations in the same hour (integral time of day, 0, 1 … 22, 23 hours) respectively, and taking the laser radar ratio of the M stations as a real value
The laser radar ratio of N sites is a reference value
The relative error of the lidar ratio is calculated. The relative distance between the laser radar phase comparison relative error and the two stations can be called a group of corresponding points;
s5-3: repeating the step S5-2, and calculating the laser radar relative error and the relative distance between any two stations so as to obtain 1953 groups of corresponding points;
s5-4: the embodiment requires that the total number of the calculated average lidar relative errors in each group of corresponding points is more than 50, and the distance between two stations is less than 500 km. After screening, 78 sets of valid corresponding point data are obtained. As shown in fig. 4, a mathematical relationship between the lidar relative error and the relative distance is established.
S6: the error transfer formulas of the backscattering coefficient, the extinction coefficient and the aerosol laser radar ratio are as follows:
in the formula (I), the compound is shown in the specification,
indicating the total relative error of the aerosol lidar ratio,
representing the statistical standard deviation of the corresponding quantity; order to
And
respectively is
And
then the total relative error of the aerosol lidar ratio is solved as
. The Russian scientist Igor et al thinks that when the method is used for inverting the micro-physical characteristics of the aerosol, the acceptable maximum relative errors of the backscattering coefficient and the extinction coefficient are both 20%. Therefore, this embodiment takes
=
=20%, the calculated maximum relative error of the lidar ratio was 28.3%. With reference to fig. 4, the range of the laser radar applicable to the regional transmission can be determined to be 0-128 km. By using the method provided by the invention in the range, the error of the inversion extinction coefficient of the Mie scattering laser radar can be within 20%. The specific number (more than or equal to 1) of the Mi scattering laser radars can be arranged according to the positions and the number of stations of the sunshine photometer existing in the range of 500km by taking the high-spectral-resolution laser radars as the center.
The embodiments described above are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions and equivalents made within the scope of the principles of the present invention should be included in the scope of the present invention.