CN106323920B - Aerosol Multiple Scattering analogy method and system based on Monte carlo algorithm - Google Patents
Aerosol Multiple Scattering analogy method and system based on Monte carlo algorithm Download PDFInfo
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Abstract
The present invention provides a kind of aerosol Multiple Scattering analogy method and system based on Monte carlo algorithm, a series of subprocess such as it is transmitting that method therein, which is photon transmission procedure decomposition, absorbs, scatters and reflect, by establishing the probabilistic model of each subprocess, stochastic problem is translated into solve.Relatively accurately atmospheric aerosol Multiple Scattering process can be simulated through the invention, to help to further increase atmospheric radiative transfer computational accuracy under the conditions of high particle concentration.
Description
Technical field
The present invention relates to satellite atmosphere remote sensing technology field, more specifically, is related to a kind of based on Monte carlo algorithm
Aerosol Multiple Scattering analogy method and system.
Background technique
With the rapid industrial development in our country, pollutant emission and the substantial increase of city suspended matter are so that some areas are sent out
The frequency of raw haze weather increases sharply, and the atmosphere of this high aerosol particle object concentration not only affects air quality, can see
Degree and human health, also exacerbate the Multiple Scattering effect of atmosphere.Therefore, the Multiple Scattering process of accurate simulation aerosol is
Calculate the premise of atmospheric radiative transfer precision.
Atmospheric radiative transfer is one and covers astrophysics, Application Optics and physics, planetary space science and atmospheric science
It is not only ancient but also obtain booming interdisciplinary study.The existing method for calculating atmospheric radiative transfer has gradually scattering method, ball
Hamonic function method, discrete-ordinate method, extraordinarily-summation, two flux methods, four-flux method, four stream approximate solutions etc..
Discrete-ordinate method is that the variation progress by radiation intensity on direction in space is discrete, and assumes that space is a certain
Radiation intensity is a definite value in solid angle, to will be related to the discrete complicated integrated form of angle or Integrated Derivative form
Radiation transfer equation be reduced to the linear differential equation of simple differential or partial differential form.Discrete-ordinate method can be very
Radiation transfer equation and other transport equations is set to carry out couple solution and can very easily handle anisotropic scattering well
Deng.
Extraordinarily-summation is reflection and the transmission property of known two dielectric layers, according to two layers total reflection and transmittance
Matter obtains atmospheric radiative transfer equation by the continuous reflection process between two layers.The conforming layer thick for one, can be by it
Be divided into 2n completely just as thin layer, reflection and the transmission property of flood can be rapidly obtained by doubling method.
Spheric harmonic function method is similar with discrete-ordinate method, is by radiation transfer equation discretization, difference is this
Radiation intensity is launched into spheric harmonic function by method.The second-rate form of spheric harmonic function is Eddington approximation.
Gradually scattering method is that Radiation Transfer Problems are solved by way of iteration.Theoretically, gradually scattering method not only can be with
For parallel atmosphere, and it can also be used for various uneven textures.
More flux theories can export succinct accurate formula, calculate simple and guarantee precision, be usually used in solving transport issues.
The diffusion flux of the collimated beam and forward and backward flowing that are flowed in four flux theories with forward and backward is measured for four totally
To represent flux.
Although the algorithm of above-mentioned calculating atmospheric radiative transfer all has their own advantages, in the spoke for solving some complex geometric shapes
It is still had some limitations in terms of penetrating transmission problem.
Summary of the invention
In view of the above problems, the object of the present invention is to provide a kind of aerosol Multiple Scattering mould based on Monte carlo algorithm
Quasi- method and system, to solve the problems, such as the atmospheric radiative transfer of some complex geometric shapes.
According to an aspect of the present invention, a kind of aerosol Multiple Scattering simulation side based on Monte carlo algorithm is provided
Method, comprising:
Initialize photon weight, photon atmosphere top layer random site and the direction of the launch；
Sampling obtains the transmission range of photon before collision next time occurs in an atmosphere；
Photon is obtained in physical space according to the extinction coefficient in acquired transmission range and aerosol scattering parameter library
In transmission range, and determine whether photon collides according to transmission range of the acquired photon in physical space, gas
Parameter in colloidal sol scattering parameter library includes Scattering Phase Function, single scattering albedo and the delustring system of every kind of aerosol components
Number；Wherein,
When photon collides, the new weight of the photon after collision is determined according to the crash type of photon；Wherein,
The crash type of photon includes scattering collision and earth surface reflection collision；
The new weight of photon is compared with preset threshold；Wherein,
When the new weight of photon is not less than preset threshold, the new transmission direction after photon collides is calculated, is laid equal stress on
New sampling obtains the transmission range of photon before collision next time occurs in an atmosphere；
When the new weight of photon is less than preset threshold or photon does not collide, by the photon number of tracking and preset
Photon number be compared；Wherein,
When the photon number of tracking is less than preset photon number, photon weight, photon are reinitialized in big pneumatic jack
The random site and the direction of the launch of layer；
When the photon number of tracking is identical as preset photon number, photon error statistics are carried out, atmosphere is obtained and penetrates
Rate and atmosphere top layer average reflectance.
According to another aspect of the present invention, a kind of aerosol Multiple Scattering simulation system based on Monte carlo algorithm is provided
System, comprising:
Initialization unit, for initialize photon weight, photon atmosphere top layer random site and the direction of the launch；
Transmission range acquiring unit obtains the transmission distance of photon before collision next time occurs in an atmosphere for sampling
From according to transmission distance of the extinction coefficient acquisition photon in physical space in acquired distance and aerosol scattering parameter library
From, wherein the parameter in aerosol scattering parameter library includes the Scattering Phase Function of every kind of aerosol components, single scattering albedo
And extinction coefficient；
The new Weight Acquisition unit of photon, in the photon obtained according to transmission range acquiring unit in physical space
After transmission range determines that photon collides, the new weight of the photon after collision is obtained according to the crash type of photon；Its
In, the crash type of photon includes scattering collision and earth surface reflection collision；
Photon transmission direction acquiring unit for calculating the new transmission direction after photon collides, and is sampled again
Obtain the transmission range of photon before collision next time occurs in an atmosphere；Wherein, it is obtained when the new Weight Acquisition unit of photon
When the new weight ratio preset threshold of photon is big, photon transmission direction acquiring unit obtains the new transmission side after photon collides
To；
Comparing unit, for the photon number of tracking to be compared with preset photon number；Wherein, new when photon
When weight is less than preset threshold or photon and does not collide, comparing unit is by the photon number of tracking and preset photon number
It is compared；Wherein, when the photon number of tracking is less than preset photon number, initialization unit reinitializes photon power
Random site and the direction of the launch of the heavy, photon in atmosphere top layer；
Statistic unit obtains atmospheric transmittance and atmosphere top layer average reflectance for carrying out photon error statistics；Its
In, when the new weight ratio preset threshold for the photon that the new Weight Acquisition unit of photon obtains is small, and the photon number tracked reaches pre-
If photon number when, statistic unit carry out photon error statistics.
Using above-mentioned aerosol Multiple Scattering analogy method and system according to the present invention based on Monte carlo algorithm, no
Only it is capable of handling any single scattering albedo and the very strong Scattering Phase Function of anisotropy, additionally it is possible to handle random geometry
Under atmospheric radiative transfer, and the calculated result of other atmospheric radiative transfer algorithms is verified, and then accurately to gas
The Multiple Scattering process of colloidal sol is simulated.
To the accomplishment of the foregoing and related purposes, one or more aspects of the present invention include be particularly described below and
The feature particularly pointed out in claim.Certain illustrative aspects of the invention is described in detail in the following description and the annexed drawings.
However, these aspects indicate only usable some of the various ways in the principles of the present invention.In addition, of the invention
It is intended to include all such aspects and their equivalent.
Detailed description of the invention
By reference to the following description in conjunction with the accompanying drawings and the contents of the claims, and with to it is of the invention more comprehensively
Understand, other objects and results of the present invention will be more clearly understood and understood.In the accompanying drawings:
Fig. 1 is according to the first of the aerosol Multiple Scattering analogy method based on Monte carlo algorithm of the embodiment of the present invention
Flow diagram；
Fig. 2 is according to the second of the aerosol Multiple Scattering analogy method based on Monte carlo algorithm of the embodiment of the present invention
Flow diagram；
Fig. 3 is the logic according to the aerosol Multiple Scattering simulation system based on Monte carlo algorithm of the embodiment of the present invention
Structural schematic diagram.
Identical label indicates similar or corresponding feature or function in all the appended drawings.
Specific embodiment
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.
For the aforementioned existing algorithm for calculating atmospheric radiative transfer in the Radiation Transfer Problems for solving complex geometric shapes
There is limitation in aspect, the present invention based on the probability sampling of Monte Carlo, the transmission process of photon be converted into
Machine problem solves, and can relatively accurately simulate, is conducive to atmospheric aerosol Multiple Scattering process through the invention
Further increase atmospheric radiative transfer computational accuracy under the conditions of high particle concentration.
Before the present invention will be described, a preliminary introduction first is carried out to Monte carlo algorithm.
Monte carlo algorithm is that the scattering of photon is regarded as to a random process, using radiation transfer equation as foundation, and it is straight
Connect simulation radiation transfer equation.It is a kind of Method of Stochastic, i.e., by scattering process as the collision in photon and medium
Journey, the distance that photon is walked in medium between collision twice is related with extinction coefficient, and photon will change direction of advance after collision, dissipates
Firing angle is determined by phase function, is tracked to a large amount of photons " behavior " and is counted the result that can obtain particular problem.Monte Carlo
The advantages of algorithm, is: its Radiation Transfer Problems that can solve some complex geometries or the result as other radiation transmission algorithms
Verifying, the Radiation Transfer Problems being capable of handling under random geometry are also capable of handling any single scattering albedo and each
The very strong Scattering Phase Function of anisotropy, and other existing radiation transmission algorithms all have certain limitation in this respect.
In order to illustrate the aerosol Multiple Scattering analogy method provided by the invention based on Monte carlo algorithm, Fig. 1 is shown
The first pass of aerosol Multiple Scattering analogy method according to an embodiment of the present invention based on Monte carlo algorithm.
As shown in Figure 1, the aerosol Multiple Scattering analogy method provided by the invention based on Monte carlo algorithm includes:
S110: calculating and establishes aerosol scattering parameter library；Wherein, the parameter in the aerosol scattering parameter library includes every
Scattering Phase Function, single scattering albedo and the extinction coefficient of kind aerosol components.
S120: initialization photon weight, photon atmosphere top layer random site and the direction of the launch.
S130: sampling obtains the transmission range of photon before collision next time occurs in an atmosphere.
S140: photon is obtained in physics according to the extinction coefficient in acquired transmission range and aerosol scattering parameter library
Transmission range in space, and determine whether photon touches according to transmission range of the acquired photon in physical space
It hits.
S150: when photon collides, the new weight of the photon after collision is determined according to the crash type of photon；
Wherein, the crash type of photon includes scattering collision and earth surface reflection collision.
S160: the new weight of photon is compared with preset threshold；Wherein, when the new weight of photon is not less than default threshold
When value, S170 is entered step；When the new weight of photon is less than preset threshold or photon does not collide, enter step
S180。
S170: the new transmission direction after photon collides is calculated, and returns to S130.
S180: the photon number of tracking is compared with preset photon number；
S190: when the photon number of tracking is less than preset photon number, S120 is returned to；When tracking photon number with
When preset photon number is identical, photon error statistics are carried out, obtain atmospheric transmittance and atmosphere top layer average reflectance.
In order to which the present invention will be described in more detail, Meng Teka is based on Fig. 2 shows according to an embodiment of the present invention
The second procedure of the aerosol Multiple Scattering analogy method of Lip river algorithm.It is as shown in Figure 2:
S1: calculating and establishes aerosol scattering parameter library.
Specifically, it is based on Mie algorithm, obtains different component, the Scattering Phase Function of the aerosol of different-grain diameter size, single
Scattering albedo and Extinction Cross；By acquired different component, the Scattering Phase Function of the aerosol of different-grain diameter size, single
Scattering albedo and Extinction Cross are integrated with volume size distribution function, establish the scattering phase letter comprising every kind of aerosol components
The scattering parameter library of number, single scattering albedo and extinction coefficient.
Such as: utilize Mie scattering method, calculate different radii be 0.01~15 micron black carbon, sulfate, organic carbon,
Scattering Phase Function, single scattering albedo and the Extinction Cross of the particulates such as sand and dust, sea salt；By above-mentioned calculated result and just
State distribution volume size distribution function integrated, establish comprising black carbon, sulfate, organic carbon, sand and dust, marine aerosol dissipate
Penetrate the scattering parameter library of phase function, single scattering albedo and extinction coefficient.
S2: random site in atmosphere top layer of initialization photon weight, photon, the direction of the launch.
Specifically, the initial weight of photon is set as 1, sets photon in big pneumatic jack in the initial position of atmosphere top layer
Any random site on layer x-y plane is determined based on local time and longitude and latitude by solar zenith angle and solar azimuth
The direction of the launch of photon.
For example, assuming that the sun is under the premise of uniform irradiation, for by the photoemissive photon of the sun, by its initial bit
It installs as any random site on atmosphere top layer x-y plane.That is: x0=ξx(xmax-xmin)+xmin；y0=ξy(ymax-ymin)
+ymin；z0=zmax；
Wherein, ξxAnd ξyIt is the equally distributed random number in [0,1] range, [xmin, xmax]、[ymin, ymax]、[zmin,
zmax] be respectively the direction x, y and z atmosphere cell value range, wherein xmin=0km, xmax=10km, ymin=0km,
ymax=10km, zmin=0km, zmax=12km.
As for the direction of the launch of photon, then can be described by 150 ° of 30 ° of solar zenith angle and solar azimuth, light
The direction of the launch of son is related with local time and longitude and latitude, rather than a random process.
S3: transmission range of the simulated photons before scattering collision occurs next time in an atmosphere, and judge whether photon is escaped
Escape zoning.
Specifically, random sampling obtains corresponding to the transmission range of photon before scattering collision occurs next time in an atmosphere
Opticalthicknessτ, i.e. τ=- ln (1- ξ), wherein ξ be in [0,1] range equally distributed random number；Based in step S1
The Aerosol Extinction β being calculated obtains transmission range S, i.e. S=τ/β of the photon in physical space；Whether judge S
Distance (i.e. preset zoning) greater than photon current location along transmission direction away from zoning boundary.
Wherein, when the transmission range S when the photon of acquisition in physical space is less than preset zoning, illustrate photon
Preset zoning is not escaped out, and scattering collision occurs for photon at this time, enters step S4；When the photon of acquisition is in physical space
In transmission range S be not less than preset zoning when, illustrate that photon has escaped out preset zoning, enter step
S5。
S4: photon is moved to position of collision, and judges the crash type of photon, subsequently into S6.
Specifically, photon is moved to the position (x that scattering collision occursnew, ynew, znew)；It establishes black carbon, sulfate, have
Machine carbon, sand and dust, marine aerosol extinction coefficient meter probability search table；By the equally distributed random number in [0,1] range
ξ successively searches the scattering collision type of photon in existing extinction coefficient cumulative probability look-up table, until determining random number ξ
Corresponding scattering collision type, with the determining aerosol components that scattering collision occurs with photon.
S5: judging whether photon occurs earth surface reflection collision, if photon is preset there is no earth surface reflection collision
The end of transmission in zoning, enters step S9；If earth surface reflection collision occurs, S6 is entered step.
S6: new weight of the photon after collision is calculated.
Specifically, if scattering collision occurs for photon, then the new weight of photon is present weight value and selected collision
The product of the single scattering albedo of aerosol components；If earth surface reflection occurs for photon, then the new weight of photon is present weight
The product of value and surface albedo.
It should be noted that surface albedo is 0.3；The above-mentioned selected aerosol components collided are determining with light
The aerosol components of scattering collision occur for son.
S7: judge whether the new weight of photon is less than given threshold.Wherein, if the new weight of photon is less than given threshold,
The then end of transmission of the photon transmission in zoning, enters step S9；If the new weight of photon is not less than given threshold, into
Enter S8.
S8: transmission direction new after photon collides, and return step S3 are calculated.
For example, given threshold is 0.5, then when the new weight of photon is less than 0.5, a random number ξ and photon are selected
New weight is compared, if the weight of photon is not more than random number ξ, photon transmission termination, stopping chases after the photon
Track；It is 1 by the weights resetting of photon, and continue its transmission process if the weight of photon is greater than random number ξ；If photon is sent out
Raw scattering collision calculates the accumulated probability of the aerosol components Scattering Phase Function of selection collision, and by uniform in [0,1] range
The random number ξ sampling selective scattering angle of distribution；If earth surface reflection collision occurs for photon, angle of reflection cosine value isReflection
Azimuth is 2px2, wherein x1And x2The equally distributed random number in [0,1] range.
Wherein, above-mentioned random number is the equally distributed pseudorandom in [0,1] range generated by Mason's Rotation Algorithm
Number, above-mentioned cumulative probability are the integral of probability density function.
S9: judge whether the photon number of tracking reaches photon number initially set.For example, can will be initially set
Photon number is set as 10000000；When the photon number of tracking reaches the photon number of the setting, S10 is entered step, otherwise
Enter step S2.
S10: photon error statistics are carried out, and calculate atmospheric transmittance and atmosphere top layer average reflectance.
It corresponds to the above method, the present invention provides a kind of aerosol Multiple Scattering simulation system based on Monte carlo algorithm
System.Fig. 3 shows the logic of the aerosol Multiple Scattering simulation system according to an embodiment of the present invention based on Monte carlo algorithm
Structure.
As shown in figure 3, the aerosol Multiple Scattering simulation system 300 based on Monte carlo algorithm of offer of the invention is wrapped
It includes aerosol scattering parameter library and establishes unit 310, initialization unit 320, transmission range acquiring unit 330, the new weight of photon and obtain
Take unit 340, photon transmission direction acquiring unit 350, comparing unit 360, statistic unit 370.
Wherein, aerosol scattering parameter library establishes unit 310 and establishes aerosol scattering parameter library；Wherein, aerosol scattering
Parameter in parameter library includes Scattering Phase Function, single scattering albedo and the extinction coefficient of every kind of aerosol components.
Specifically, it is based on Mie algorithm, obtains different component, the Scattering Phase Function of the aerosol of different-grain diameter size, single
Scattering albedo and Extinction Cross；By acquired different component, the Scattering Phase Function of the aerosol of different-grain diameter size, single
Scattering albedo and Extinction Cross are integrated with volume size distribution function, establish the scattering phase letter comprising every kind of aerosol components
The scattering parameter library of number, single scattering albedo and extinction coefficient.
Initialization unit 320 be used for initialize photon weight, photon atmosphere top layer random site and the direction of the launch.
Specifically, photon initial weight is set as 1, sets photon in the initial position of atmosphere top layer as in atmosphere top layer x-
Any random site on y plane；Based on local time and longitude and latitude, photon is determined by solar zenith angle and solar azimuth
The direction of the launch.
Transmission range acquiring unit 330, which is used to sample, obtains the transmission distance of photon before collision next time occurs in an atmosphere
From according to transmission distance of the extinction coefficient acquisition photon in physical space in acquired distance and aerosol scattering parameter library
From.
The new Weight Acquisition unit 340 of photon is used in the photon obtained according to transmission range acquiring unit in physical space
Transmission range determine that photon collides after, according to the crash type of photon obtain by collision after photon new weight；
Wherein, the crash type of photon includes scattering collision and earth surface reflection collision.
Specifically, transmission range of the photon according to acquired in transmission range acquiring unit 330 in physical space determines
Whether photon collides, when transmission range of the photon of acquisition in physical space is less than preset zoning, photon
Scattering collision then occurs, photon is moved to the position that scattering collision occurs；It is established according to the extinction coefficient in parameter library all
The extinction coefficient accumulated probability look-up table of aerosol components；By random number ξ equally distributed in [0,1] range, existing
Accumulated probability look-up table successively searches the scattering collision type of photon, until determining scattering collision class corresponding to random number ξ
Type, with the determining aerosol components that scattering collision occurs with photon；The single of the aerosol components to collide with photon is dissipated
New weight of the product of exposure albedo and the current weight of photon as photon.
When transmission range of the photon in physical space of acquisition is not less than preset zoning, and earth surface reflection occurs
When collision, photon is moved to the boundary position of the zoning；The product of the present weight of photon and surface albedo is made
For the new weight of photon.
Photon transmission direction acquiring unit 350 is taken out again for calculating the new transmission direction after photon collides
Sample obtains the transmission range of photon before collision next time occurs in an atmosphere；Wherein, when the new Weight Acquisition unit of photon obtains
Photon new weight unlike preset threshold hour, photon transmission direction acquiring unit 350 obtains new after photon collides
Transmission direction.
Specifically, when the new weight of photon is less than 0.5, a random number is selected to be compared with the new weight of photon；Its
In, when the new weight of photon is not more than selected random number, photon transmission terminates, and stops the tracking to photon, and judgement chases after
Whether the number of the photon of track reaches preset photon number；When the new weight of photon is greater than selected random number, by light
The weights resetting of son is 1, and photon continues to transmit.
During photon continues transmission, when scattering collision occurs for photon, based in aerosol scattering parameter library
Scattering Phase Function corresponding with the aerosol components of identified scattering collision obtains the aerosol components to collide with photon
Scattering Phase Function accumulated probability, and by random number ξ equally distributed in [0,1] range sample selective scattering angle；Work as light
When earth surface reflection collision occurs for son, then angle of reflection cosine value isReflection azimuth is 2px2；Wherein, x1And ξ2Be
Equally distributed random number in [0,1] range.Wherein, above-mentioned random number is to be generated by Mason's Rotation Algorithm in [0,1] model
Interior equally distributed pseudo random number is enclosed, above-mentioned cumulative probability is the integral of probability density function.
Comparing unit 360 is for the photon number of tracking to be compared with preset photon number；Wherein, when photon
When new weight does not collide less than preset threshold or photon, comparing unit is a by the photon number of tracking and preset photon
Number is compared；Wherein, when the photon number of tracking is less than preset photon number, initialization unit reinitializes photon
Weight, photon atmosphere top layer random site and the direction of the launch.
Statistic unit 370 obtains atmospheric transmittance and atmosphere top layer average reflectance for carrying out photon error statistics；Its
In, when the new weight ratio preset threshold for the photon that the new Weight Acquisition unit of photon obtains is small, and the photon number tracked reaches pre-
If photon number when, statistic unit carry out photon error statistics.
According to above-mentioned, the aerosol Multiple Scattering analogy method and system provided by the invention based on Monte carlo algorithm is
It is a series of subprocess such as transmitting, absorption, scattering and reflection by photon transmission procedure decomposition, by establishing the general of each subprocess
Rate model, is translated into stochastic problem to solve, and therefore, the present invention can not only handle any single scattering albedo and each
The very strong Scattering Phase Function of anisotropy, additionally it is possible to handle the atmospheric radiative transfer under random geometry, and to other atmosphere
The calculated result of radiation transmission algorithm is verified, and then is accurately simulated to the Multiple Scattering process of aerosol.
It is more to describe the aerosol according to the present invention based on Monte carlo algorithm in an illustrative manner above with reference to attached drawing
Secondary scattering analogue method and system.It will be understood by those skilled in the art, however, that for aforementioned present invention proposed based on illiteracy
The aerosol Multiple Scattering analogy method and system of special Carlow algorithm, can also make on the basis of not departing from the content of present invention
Various improvement.Therefore, protection scope of the present invention should be determined by the content of appended claims.
Claims (9)
1. a kind of aerosol Multiple Scattering analogy method based on Monte carlo algorithm, comprising:
Initialize photon weight, photon atmosphere top layer random site and the direction of the launch；
Sampling obtains the transmission range of photon before collision next time occurs in an atmosphere；
Photon is obtained in physical space according to the extinction coefficient in acquired transmission range and aerosol scattering parameter library
Transmission range, and determine whether photon collides according to transmission range of the acquired photon in physical space, the gas
Parameter in colloidal sol scattering parameter library includes Scattering Phase Function, single scattering albedo and the delustring system of every kind of aerosol components
Number；Wherein,
When photon collides, the new weight of the photon after collision is determined according to the crash type of photon；Wherein, described
The crash type of photon include scattering collision and earth surface reflection collision, if the photon occur scattering collision, the photon it is new
Weight is the single scattering albedo for the aerosol components that scattering collision occurs with photon and the product of present weight value；If the light
Earth surface reflection collision occurs for son, and the new weight of the photon is the product of present weight value and surface albedo；
The new weight of the photon is compared with preset threshold；Wherein,
When the new weight of the photon is not less than the preset threshold, the new transmission side after the photon collides is calculated
To, and sampling obtains the transmission range of photon before collision next time occurs in an atmosphere again；
When the new weight of the photon, which is less than the preset threshold or photon, not to collide, by the photon number of tracking with
Preset photon number is compared；Wherein,
When the photon number of tracking is less than preset photon number, photon weight, photon are reinitialized in atmosphere top layer
Random site and the direction of the launch；
When the photon number of tracking is identical as preset photon number, carry out photon error statistics, obtain atmospheric transmittance and
Atmosphere top layer average reflectance.
2. the aerosol Multiple Scattering analogy method based on Monte carlo algorithm as described in claim 1, wherein according to institute
During transmission range of the photon of acquisition in physical space determines whether photon collides,
When transmission range of the photon of acquisition in physical space is within the scope of preset zoning, the photon occurs to dissipate
Collision is penetrated, the photon is moved to the position that scattering collision occurs, is then established according to the extinction coefficient in the parameter library
The extinction coefficient accumulated probability look-up table of all aerosol components；
By random number ξ equally distributed in [0,1] range, light is successively searched in the extinction coefficient accumulated probability look-up table
With photon scattering collision occurs for the scattering collision type of son until determining scattering collision type corresponding to random number ξ with determining
Aerosol components；
Using the product of the current weight of the single scattering albedo of the aerosol components to collide with photon and photon as photon
New weight.
3. the aerosol Multiple Scattering analogy method based on Monte carlo algorithm as claimed in claim 2, when the photon of acquisition
Transmission range in physical space exceeds preset zoning range, and when photon generation earth surface reflection collision, will be described
Photon is moved to the boundary position of the zoning；
Using the product of the present weight of photon and surface albedo as the new weight of the photon.
4. the aerosol Multiple Scattering analogy method based on Monte carlo algorithm as claimed in claim 2 or claim 3, wherein work as institute
When stating the new weight of photon less than the preset threshold, a random number is selected to be compared with the new weight of the photon；Wherein,
When the new weight of photon is not more than selected random number, the photon transmission terminates, and stopping chases after the photon
Track, judges whether the number of the photon of tracking reaches preset photon number；
It is 1 by the new weights resetting of the photon, the photon continues when the new weight of photon is greater than selected random number
Transmission.
5. the aerosol Multiple Scattering analogy method based on Monte carlo algorithm as claimed in claim 4, wherein in the light
During son continues transmission,
When scattering collision occurs for the photon, based in the aerosol scattering parameter library with identified scattering collision
The corresponding Scattering Phase Function of aerosol components obtains the tired of the Scattering Phase Function of the aerosol components to collide with the photon
Probability is counted, and by random number ξ equally distributed in [0,1] range sampling selective scattering angle；
When earth surface reflection collision occurs for the photon, then angle of reflection cosine value isReflection azimuth is 2 π ξ2；Wherein, ξ1
And ξ2It is the equally distributed random number in [0,1] range.
6. the aerosol Multiple Scattering analogy method based on Monte carlo algorithm as described in claim 1, wherein establishing gas
During colloidal sol scattering parameter library,
Based on Mie algorithm, different component, the Scattering Phase Function of the aerosol of different-grain diameter size, single scattering albedo are obtained
And Extinction Cross；
By acquired different component, the Scattering Phase Function of the aerosol of different-grain diameter size, single scattering albedo and delustring
Section is integrated with volume size distribution function, establishes the Scattering Phase Function comprising every kind of aerosol components, the scattering,single reflection of light
The scattering parameter library of rate and extinction coefficient.
7. the aerosol Multiple Scattering analogy method based on Monte carlo algorithm as described in claim 1, wherein initializing
Photon weight, photon during the random site of atmosphere top layer and the direction of the launch,
Photon initial weight is set as 1；
Photon is any random site on atmosphere top layer x-y plane in the initial position of atmosphere top layer；
Based on local time and longitude and latitude, the direction of the launch of photon is determined by solar zenith angle and solar azimuth.
8. the aerosol Multiple Scattering analogy method based on Monte carlo algorithm as described in claim 1, according to acquired in
Distance and the aerosol scattering parameter library in extinction coefficient obtain the process of transmission range of the photon in physical space
In,
Setting sampling obtains optical thickness corresponding to the transmission range of photon before scattering collision occurs next time in an atmosphere
τ, τ=- ln (1- ξ), wherein ξ is the equally distributed random number in [0,1] range；
The extinction coefficient of the aerosol components in the aerosol scattering parameter library is set as β, the photon is in physical space
Transmission range be S, then S=τ/β.
9. a kind of aerosol Multiple Scattering simulation system based on Monte carlo algorithm, comprising:
Initialization unit, for initialize photon weight, photon atmosphere top layer random site and the direction of the launch；
Transmission range acquiring unit obtains the transmission range of photon before collision next time occurs in an atmosphere, root for sampling
Transmission range of the photon in physical space is obtained according to the extinction coefficient in acquired distance and aerosol scattering parameter library,
In, the parameter in the aerosol scattering parameter library includes the Scattering Phase Function of every kind of aerosol components, single scattering albedo
And extinction coefficient；
The new Weight Acquisition unit of photon, in the photon obtained according to the transmission range acquiring unit in physical space
After transmission range determines that photon collides, the new weight of the photon after collision is obtained according to the crash type of photon；Its
In, the crash type of the photon includes scattering collision and earth surface reflection collision, if scattering collision, the light occur for the photon
The new weight of son is the single scattering albedo for the aerosol components that scattering collision occurs with photon and the product of present weight value；If
Earth surface reflection collision occurs for the photon, and the new weight of the photon is the product of present weight value and surface albedo；
Photon transmission direction acquiring unit, for calculating the new transmission direction after photon collides, and again, sampling is obtained
Transmission range of the photon before collision next time occurs in an atmosphere；Wherein, it is obtained when the new Weight Acquisition unit of the photon
When the new weight ratio preset threshold of the photon is big, photon transmission direction acquiring unit obtains new after photon collides
Transmission direction；
Comparing unit, for the photon number of tracking to be compared with preset photon number；Wherein, new when the photon
When weight is less than preset threshold or photon and does not collide, the comparing unit is by the photon number of tracking and preset photon
Number is compared；Wherein, when the photon number of tracking is less than preset photon number, the initialization unit is again initial
Change photon weight, photon atmosphere top layer random site and the direction of the launch；
Statistic unit obtains atmospheric transmittance and atmosphere top layer average reflectance for carrying out photon error statistics；Wherein, when
The new weight ratio preset threshold for the photon that the new Weight Acquisition unit of photon obtains is small, and the photon number tracked reaches
When preset photon number, the statistic unit carries out photon error statistics.
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