CN103175759A - Method for acquiring complex refractive index of urban aerosol on basis of various ground-based remote sensing technologies - Google Patents

Abstract

The invention relates to a method for acquiring a complex refractive index of urban aerosol on the basis of various ground-based remote sensing technologies. The method comprises the following steps of: acquiring the extinction coefficient and the scattering extinction ratio of the aerosol through an inverse algorithm by virtue of Raman laser radar echo signals, and integrating the extinction coefficient of a certain route to acquire the optical thickness of the aerosol on the route; continuously correcting the extinction coefficient and the scattering extinction ratio by performing iterative alignment on an aerosol optical thickness of a whole atmospheric layer acquired via a sun photometer and the aerosol optical thickness acquired via a laser radar according to a Monte Carlo principle; then acquiring the particle size distribution of the aerosol via a particle spectrometer; and finally, acquiring the complex refractive index of the urban aerosol according to a mie-scattering model by virtue of the known scattering extinction ratio of the aerosol and the particle size distribution of the aerosol. According to the invention, the complex refractive index of the urban aerosol is acquired by the Raman laser radar, the sun photometer and the particle spectrometer, and the method has the advantages of small error, high discriminability and high universality.

Description

Obtain the method for aerosols from major cities complex refractive index based on multiple Ground-based remote sensing technology

Technical field

The present invention relates to gasoloid optical detector technology field, especially a kind of method of obtaining the aerosols from major cities complex refractive index based on multiple Ground-based remote sensing technology (Raman lidar, heliograph, grain spectrometer).

Background technology

Urban environment is the key factor of the big city sustainable development of socio-economy, to the monitoring of the atmosphere quality in overhead, city with analyze the life health that is closing the city people.Although atmospheric aerosol content is seldom, climate change there be important directly and indirectly affecting, be the important factor in urban climate change modeling and remote sensing of environment.The atmospheric aerosol complex refractive index is the important parameter of performance aerosol optical characteristics, by decisions such as aerocolloidal chemical composition, the distributions of grain spectrum, is that the atural object remote sensing atmosphere is corrected and the important indicator of gasoloid climatic effect research aspect.The complex refractive index of atmospheric aerosol particle is made of real part and imaginary part two parts, is expressed as m=n _r-n _ii。Wherein the refractive index real part is main relevant with light scattering, and the refractive index imaginary part is main relevant with light absorption, is that the effect of atmospheric aerosol in radiation and climatic effect is heating or cooling factor of determination.Therefore, explore measuring the particulate birefringence has great importance to the radiation effect of atmosphere to understanding gasoloid.The measuring method of complex refractive index mainly contains dry gas colloidal sol chemical composition mole fraction accounting method at present, the filter membrane sampling method, and individual particle analytic approach etc., but this several method error is larger; It is highly sensitive that photoacoustic method is measured, but to the having relatively high expectations of equipment and technology, complicated operation.Raman lidar can be broken away from the constraint that the conventional laser radar need to be supposed the scattering extinction ratio, the aerocolloidal space distribution of inverting preferably, can also obtain simultaneously Aerosol Extinction, scattering coefficient and scattering extinction ratio accurately have quick, efficient, continuous characteristics; Heliograph can be measured the aerocolloidal optical thickness of the whole layer of atmosphere, and in order to proofread and correct the radargrammetry result, improves radar inversion result degree of accuracy; The grain spectrometer can provide the grain spectrum of gasoloid in certain particle size range to distribute, and this is that the Mie scattering model calculates needed another important calculating parameter.Above-mentioned three kinds of remote sensing technologies are all used extensively in the atmospheric aerosol field of detecting, and inversion technique is also comparatively ripe.Therefore, how effectively to analyze the concertedness between these several Ground-based remote sensing apparatus measures results, comprehensive utilization Ground-based remote sensing measurement data, and in conjunction with the Mie scattering model theory, effectively obtain the aerosols from major cities optical characteristics, especially the gasoloid complex refractive index is the research emphasis of atmospheric exploration analysis field always.

Summary of the invention

The purpose of this invention is to provide a kind of method of obtaining the aerosols from major cities complex refractive index based on multiple Ground-based remote sensing Detection Techniques,, complicated operation large with the error that solves classic method can not obtain the problem of information needed preferably.

The technical solution used in the present invention is:

The purpose of this invention is to provide and a kind ofly obtain the aerosols from major cities complex refractive index based on multiple Ground-based remote sensing Detection Techniques (Raman lidar, heliograph and grain spectrometer), it is characterized in that: after at first utilizing the Raman lidar echoed signal through the algorithm inverting, obtain Aerosol Extinction and scattering extinction ratio, and the extinction coefficient in certain path is carried out integration, obtain the aerosol optical depth on this path; According to the Monte Carlo principle, the aerosol optical depth that the atmosphere that utilizes heliograph to obtain whole layer aerosol optical depth and laser radar obtain carries out iteration to be compared, and constantly revises extinction coefficient and scattering extinction ratio; Then obtain the aerosol particle spectrum by the grain spectrometer; Utilize aerosol extinction scattering ratio and aerosol particle spectrum to distribute, according to the Mie scattering model, acquisition is based on Aerosol Extinction and the scattering extinction ratio of Mie scattering model, compare calculating the result and the actual measured results that obtain, obtain at last the actual complex refractive index of aerosols from major cities, the specific algorithm step is:

(1) the echo equation of single wavelength nitrogen Raman scattering laser radar is to be expressed as:

$P_{{\mathrm{\λ}}_R}\left(z\right)=K_{{\mathrm{\λ}}_R}O\left(z\right)N_R\left(z\right)z^{-2}{N}_R\left(z\right)\frac{{\mathrm{d\σ}}_{{\mathrm{\λ}}_R}\left(\mathrm{\π}\right)}{\mathrm{d\Ω}}\exp \{-\underset{0}{\overset{z}{\∫}}[{\mathrm{\α}}_{{\mathrm{\λ}}_0}^{\mathrm{mol}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_0}^{\mathrm{aer}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_R}^{\mathrm{mol}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_R}^{\mathrm{aer}}\left(\mathrm{\ζ}\right)\left]\mathrm{d\ζ}\right\}---\left(1\right)$

Wherein, The distance z place wavelength X that receives for Raman lidar _RNitrogen Raman backscatter signal,

Be the Raman laser radar system constant, O (z) is the geometric overlap factor function, N _R(z) be nitrogen number density in atmosphere, It is independently nitrogen molecule Raman back scattering differential cross-section of distance; λ ₀Be laser emission wavelength,

With

Be atmospheric molecule and the aerocolloidal extinction coefficient of height z place laser emission wavelength, subscript mol and aer represent respectively the extinction coefficient of gasoloid and atmospheric molecule;

With

Be respectively height z place's atmospheric molecule and aerocolloidal extinction coefficient;

(2) utilize the Ansmann method to carry out Aerosol Extinction inverting based on Raman lidar, obtain the extinction coefficient at height Z place

And scattering coefficient

:

(3) utilize formula

(2)

Obtain aerosol scattering extinction ratio BER;

(4) utilize formula

(3) obtain the whole layer of atmosphere aerosol optical depth τ _Lidar

(5) according to the Bouguer law, the direct projection solar radiation E(W/m2 that heliograph records) be expressed as on specific wavelength:

E=E ₀R ^-2exp(-mτ)T _g （4）

E wherein ₀Be the solar irradiance in the atmosphere external world on an astronomical unit (AU) distance, R measures solar distance (AU) constantly, and m is the air quality number, and τ is the total vertical optical thickness of atmosphere, T _gFor absorbing gas permeation rate;

(6) obtain atmosphere optical thickness τ based on heliograph:

If the instrument output voltage V is directly proportional to E, formula (4) can be write as:

V=V ₀R ^-2exp(-mτ)T _g （5）

V wherein ₀Be the calibration constant, refer to that being extrapolated to m from a series of observed readings is the magnitude of voltage V of 0 o'clock, by lnV+lnR ²Draw straight line with m, the slope of straight line is exactly vertical optical thickness-τ;

(7) obtain aerosol optical depth τ based on heliograph _α:

The total extinction optical thicl ness T of atmosphere is by molecular scattering τ _r, aerosol scattering τ _αWith gas absorption delustring τ _gThree parts form:

τ=τ _r+τ _α+τ _g （6）

Molecular scattering opticalthicknessτ wherein _rCalculated by the surface pressure measured value, at visible near-infrared band gas

Absorbing is mainly the absorption of ozone and steam, there is no the passage of gas absorption, τ _gCan ignore, deduct the molecular scattering opticalthicknessτ from total optical thickness so _r, can obtain aerocolloidal opticalthicknessτ _α

(8) utilize Monte Carlo method, the opticalthicknessτ that laser radar is obtained _LidarOpticalthicknessτ with the heliograph acquisition _αCarry out the iteration comparison, when satisfying condition | τ _Lidar-τ _α|＜ ^-4The time, output aerosol scattering extinction value BER; If do not satisfy, with the new input as the Raman radar equation of the BER value calculated, begin another iteration, until condition is satisfied;

(9) so carry out iterative computation, until all BER values that final search goes out to satisfy condition;

(10) utilizing the grain spectrometer to obtain the aerosol particle spectrum distributes;

(11) select wave band 355nm, suppose certain refractive index, utilize the grain spectrum data that obtain, calculate extinction coefficient α by the Mie model _calWith scattering extinction ratio BER _cal

(12) with the α that calculates _cal, BER _calObtain with radargrammetry

Compare with the BER result, if close or identical in certain error range, in calculating, the refractive index of hypothesis is exactly aerocolloidal actual complex refractive index.

Advantage of the present invention is:

The present invention fully utilizes Raman lidar, heliograph and these three kinds of ground instruments of grain spectrometer, obtaining respectively Aerosol Extinction value, scattering extinction value, scattering extinction ratio BER, optical thickness value and gasoloid particle diameter distributes, with these gasoloid basic optical parameters in conjunction with the Mie scattering model, carry out the iteration comparison, finally obtained the complex refractive index (comprising real part and imaginary part) of aerosols from major cities, has error little, the advantage that resolving ability is high, universality is strong.

Description of drawings

Fig. 1 is laser radar detection Aerosol Extinction, scattering coefficient and BER profile figure.

Fig. 2 is surveyed aerosol optical depth τ by heliograph _αThe curve map of value.

Fig. 3 is the aerosol particle spectrum distribution plan that the grain spectrometer obtains.

The schematic diagram of the real part of the gasoloid complex refractive index that Fig. 4 (a) obtains for this method.

The schematic diagram of the imaginary part of the gasoloid complex refractive index that Fig. 4 (b) obtains for this method.

Fig. 5 is algorithm flow chart.

Embodiment

A kind of method of obtaining the aerosols from major cities complex refractive index based on Raman lidar, heliograph and grain spectrometer, implementation process mainly is divided into three parts: first obtains Aerosol Extinction, scattering coefficient, scattering extinction ratio and optical thickness value from Raman lidar; Second portion obtains the aerosol optical depth value from heliograph; Third part obtains the aerosol particle spectrum from the grain spectrometer and distributes; The 4th part is utilized the Mie scattering model, inverting aerosols from major cities complex refractive index value.

First: obtain Aerosol Extinction, scattering extinction ratio BER and sun aerosol optical depth from Raman lidar:

Step 1: the echo equation of listing single wavelength nitrogen Raman scattering laser radar:

$P_{{\mathrm{\λ}}_R}\left(z\right)=K_{{\mathrm{\λ}}_R}O\left(z\right)N_R\left(z\right)z^{-2}{N}_R\left(z\right)\frac{{\mathrm{d\σ}}_{{\mathrm{\λ}}_R}\left(\mathrm{\π}\right)}{\mathrm{d\Ω}}\exp \{-\underset{0}{\overset{z}{\∫}}[{\mathrm{\α}}_{{\mathrm{\λ}}_0}^{\mathrm{mol}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_0}^{\mathrm{aer}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_R}^{\mathrm{mol}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_R}^{\mathrm{aer}}\left(\mathrm{\ζ}\right)\left]\mathrm{d\ζ}\right\}---\left(1\right)$

Wherein,

The distance z place wavelength X that receives for Raman lidar _RNitrogen Raman backscatter signal,

Be the Raman laser radar system constant, O (z) is the geometric overlap factor function, N _R(z) be nitrogen number density in atmosphere,

It is independently nitrogen molecule Raman back scattering differential cross-section of distance; λ ₀Be laser emission wavelength,

With

Be atmospheric molecule and the aerocolloidal extinction coefficient of height z place laser emission wavelength, subscript mol and aer represent respectively the extinction coefficient of gasoloid and atmospheric molecule;

With Be respectively height z place's atmospheric molecule and aerocolloidal extinction coefficient;

Step 2: obtain the molten extinction coefficient of gas and scattering coefficient

Utilize the Ansmann method to carry out Aerosol Extinction inverting based on Raman lidar, obtain the extinction coefficient at height Z place

And scattering coefficient

Step 3: obtain aerosol scattering extinction ratio BER, see Fig. 1:

(2)

Step 4: obtain the aerosol optical depth based on laser radar:

(3)

Second portion: obtain aerosol optical depth from heliograph:

Step 5: according to the Bouguer law, the direct projection solar radiation E(W/m2 that utilizes heliograph to record) on specific wavelength be:

E=E ₀R ^-2exp(-mτ)T _g （4）

E wherein ₀Be the solar irradiance in the atmosphere external world on an astronomical unit (AU) distance, R measures solar distance (AU) constantly, and m is the air quality number, and τ is the total vertical optical thickness of atmosphere, T _gFor absorbing gas permeation rate.

Step 6: obtain atmosphere optical thickness τ:

If the instrument output voltage V is directly proportional to E, formula (4) can be write as:

V=V ₀R ^-2exp(-mτ)T _g （5）

V wherein ₀Being the calibration constant, is that to be extrapolated to m from a series of observed readings be the magnitude of voltage V of 0 o'clock.According to lnV+lnR ²Draw straight line with m, the slope of straight line is exactly vertical optical thickness-τ;

Step 7: obtain aerosol optical depth τ _α:

The total extinction optical thicl ness T of atmosphere is by molecular scattering τ _r, aerosol scattering τ _αWith gas absorption delustring τ _gThree parts form:

τ=τ _r+τ _α+τ _g （6）

Molecular scattering opticalthicknessτ wherein _rCalculated by the surface pressure measured value, at visible near-infrared band gas

Absorbing is mainly the absorption of ozone and steam.There is no the passage of gas absorption, τ _gCan ignore, deduct the molecular scattering opticalthicknessτ from total optical thickness so _r, can obtain aerocolloidal opticalthicknessτ _α, see Fig. 2.

Step 8: utilize Monte Carlo method, the opticalthicknessτ that laser radar is obtained _LidarOpticalthicknessτ with the heliograph acquisition _αCarry out the iteration comparison, when satisfying condition | τ _Lidar-τ _α|＜ ^-4The time, output aerosol scattering extinction value BER; If do not satisfy, with the new input as the Raman radar equation of the BER value calculated, begin another iteration, until condition is satisfied;

Step 9: so carry out iterative computation, until final search goes out to satisfy all BER values of above-mentioned condition;

Third part: utilize the grain spectrometer to obtain the aerosol particle spectrum and distribute

Step 10: utilize aerodynamic principle, obtain aerosol particle size distribution and distribute, see Fig. 3;

The 4th part: utilize above-mentioned inversion result, in conjunction with the rice model, obtain the aerosols from major cities complex refractive index

Step 11: select wave band 355nm, suppose certain refractive index, utilize the grain spectrum data that obtain, calculate extinction coefficient α by the Mie model _calWith scattering extinction ratio BER _cal

Step 12: with the α that calculates _cal, BER _calObtain with radargrammetry

Compare with the BER result, if close or identical in certain error range, in calculating, the refractive index of hypothesis is exactly aerocolloidal actual complex refractive index, sees Fig. 4.

Whole algorithm flow is seen Fig. 5.

Claims (1)

1. method of obtaining the aerosols from major cities complex refractive index based on multiple Ground-based remote sensing technology, it is characterized in that: at first utilize the Raman lidar echoed signal, through obtaining Aerosol Extinction and scattering extinction ratio after the algorithm inverting, and the extinction coefficient in certain path is carried out integration, obtain the aerosol optical depth on this path; Then according to the Monte Carlo principle, the aerosol optical depth that the atmosphere that utilizes heliograph to obtain whole layer aerosol optical depth and laser radar obtain carries out iteration to be compared, and constantly revises extinction coefficient and scattering extinction ratio; Obtain the aerosol particle spectrum by the grain spectrometer and distribute, utilize at last known aerosol scattering extinction ratio and aerosol particle spectrum to distribute, according to the Mie scattering model, obtain the aerosols from major cities complex refractive index, the specific algorithm step is:

(1) the echo equation of single wavelength nitrogen Raman scattering laser radar is to be expressed as:

$P_{{\mathrm{\λ}}_R}\left(z\right)=K_{{\mathrm{\λ}}_R}O\left(z\right)N_R\left(z\right)z^{-2}{N}_R\left(z\right)\frac{{\mathrm{d\σ}}_{{\mathrm{\λ}}_R}\left(\mathrm{\π}\right)}{\mathrm{d\Ω}}\exp \{-\underset{0}{\overset{z}{\∫}}[{\mathrm{\α}}_{{\mathrm{\λ}}_0}^{\mathrm{mol}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_0}^{\mathrm{aer}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_R}^{\mathrm{mol}}\left(\mathrm{\ζ}\right)+{\mathrm{\α}}_{{\mathrm{\λ}}_R}^{\mathrm{aer}}\left(\mathrm{\ζ}\right)\left]\mathrm{d\ζ}\right\}---\left(1\right)$

Wherein,

The distance z place wavelength X that receives for Raman lidar _RNitrogen Raman backscatter signal,

Be the Raman laser radar system constant, O (z) is the geometric overlap factor function, N _R(z) be nitrogen number density in atmosphere,

It is independently nitrogen molecule Raman back scattering differential cross-section of distance; λ ₀Be laser emission wavelength,

With

Be atmospheric molecule and the aerocolloidal extinction coefficient of height z place laser emission wavelength, subscript mol and aer represent respectively the extinction coefficient of gasoloid and atmospheric molecule; With

Be respectively height z place's atmospheric molecule and aerocolloidal extinction coefficient;

(2) utilize the Ansmann method to carry out Aerosol Extinction inverting based on Raman lidar, obtain the extinction coefficient at height Z place And scattering coefficient

(3) utilize formula

(2)

Obtain aerosol scattering extinction ratio BER;

(4) utilize formula

(3) obtain the whole layer of atmosphere aerosol optical depth τ _Lidar

(5) according to the Bouguer law, the direct projection solar radiation E(W/m2 that heliograph records) be expressed as on specific wavelength:

E=R ^-2exp(-mτ)T _g （4）

E wherein ₀Be the solar irradiance in the atmosphere external world on an astronomical unit (AU) distance, R measures solar distance (AU) constantly, and m is the air quality number, and τ is the total vertical optical thickness of atmosphere, T _gFor absorbing gas permeation rate;

(6) obtain atmosphere optical thickness τ based on heliograph:

If the instrument output voltage V is directly proportional to E, formula (4) can be write as:

V=V ₀R ^-2exp(-mτ)T _g （5）

V wherein ₀Be the calibration constant, refer to that being extrapolated to m from a series of observed readings is the magnitude of voltage V of 0 o'clock, by lnV+lnR ²Draw straight line with m, the slope of straight line is exactly vertical optical thickness-τ;

(7) obtain aerosol optical depth τ based on heliograph _α:

The total extinction optical thicl ness T of atmosphere is by molecular scattering τ _r, aerosol scattering τ _αWith gas absorption delustring τ _gThree parts form:

τ=τ _r+τ _α+τ _g （6）

Molecular scattering opticalthicknessτ wherein _rCalculated by the surface pressure measured value, at visible near-infrared band gas

Absorbing is mainly the absorption of ozone and steam, there is no the passage of gas absorption, τ _gCan ignore, deduct the molecular scattering opticalthicknessτ from total optical thickness so _r, can obtain aerocolloidal opticalthicknessτ _α

(8) utilize Monte Carlo method, the opticalthicknessτ that laser radar is obtained _LidarOpticalthicknessτ with the heliograph acquisition _αCarry out the iteration comparison, when satisfying condition | τ _Lidar-τ _α|＜ ^-4The time, output aerosol scattering extinction value BER; If do not satisfy, with the new input as the Raman radar equation of the BER value calculated, begin another iteration, until condition is satisfied;

(9) so carry out iterative computation, until all BER values that final search goes out to satisfy condition;

(10) utilizing the grain spectrometer to obtain the aerosol particle spectrum distributes;

(11) select wave band 355nm, suppose certain refractive index, utilize the grain spectrum data that obtain, calculate extinction coefficient α by the Mie model _calWith scattering extinction ratio BER _cal

(12) with the α that calculates _cal, BER _calObtain with radargrammetry

Compare with the BER result, if close or identical in certain error range, in calculating, the refractive index of hypothesis is exactly aerocolloidal actual complex refractive index.

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