CN109918770A - One kind, which is increased rain artificially, removes fine grained prediction model - Google Patents
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Abstract
One kind, which is increased rain artificially, removes fine grained prediction model, and the present invention relates to urban air quality studying technological domains；Its establishment step is as follows: the foundation of rainfall removing polydispersed aerosol theoretical model: the foundation of model formation；Arresting efficiency of the raindrop to aerosolE(D p,d p) seek；Raindrop final Sedimentation Velocity V (Dp's) seeks；Raindrop number scale Spectral structure n (Dp's) seeks；Aerosol size distribution n (dp's) seeks；Polydispersed aerosol Modifying model and verifying are removed in rainfall.Using existing result of study, on the basis of considering polydispersed aerosol distribution, by theory analysis and to the discussion of observed result, come the cleaning effect estimated and evaluate rainfall to particulate matter, to provide necessary rationale for follow-up study.
Description
Technical field
The present invention relates to urban air quality studying technological domains, and in particular to one kind, which is increased rain artificially, removes fine grained prediction
Model.
Background technique
For urban atmosphere, rainfall is the most basic natural removing approach of particulate pollutant, and wet removing can be short
Improve near-earth air environment in time.In past over half a century, raining for the cloud of particulate, it is existing to wash journey
Many researchs and observed result, but focusing on for concern is be easy to cause haze weather and is good in turn to human body by few researchs
Health and atmospheric visibility etc. have the granule subdivision for seriously affecting and threatening.Such as most during the nearly last ten years, about PM10, fine grained and
PM1Deng concentration spatial and temporal variation and its source, generation and chemical component analysis it is existing many as a result, but existing research
The discussion and analysis how small particles in rainfall are removed and removed with how degree is estimated also lacked.
Summary of the invention
In view of the defects and deficiencies of the prior art, the present invention intends to provide a kind of structure is simple, design rationally, make
Fine grained prediction model is removed with easily increasing rain artificially, using existing result of study, is considering polydispersed aerosol distribution
On the basis of, by theory analysis and to the discussion of observed result, the cleaning of particulate matter is imitated to estimate and evaluate rainfall
Fruit, to provide necessary rationale for follow-up study.
To achieve the above object, the technical solution adopted by the present invention is that: its establishment step is as follows:
1, the foundation of polydispersed aerosol theoretical model is removed in rainfall:
1.1, the foundation of model formation:
According to rainfall purification theory under cloud, the governing equation that atmospheric aerosol is removed in rainfall is expressed as follows:
C (t) is the aerosol quality and concentration of t moment, μ g/m in formula3；Λ represents rainfall removing coefficient (s-1)；
It is assumed that rainfall removing coefficient Λ does not change at any time, then the solution of (formula 1) are as follows:
C (t)=c0C in exp (- Λ t) (formula 2) formula0Aerosol matter when starting in atmosphere is cleaned for rainfall
Measure concentration, μ g/m3；T is the scavenging period calculated when being cleaned and started with precipitation, s；
From equation (formula 2) as can be seen that obtain aerosol quality and concentration in atmosphere with the changing rule of rain time,
Obtaining rainfall removing coefficient Λ is a critical issue；For the rainfall removing coefficient Λ of polydispersed aerosol, by following public
Formula acquires:
D in formulapAnd dpThe diameter of raindrop and particulate matter is respectively indicated, μm；n(Dp) indicate raindrop scale spectrum number concentration
Distribution function, 1/ (m3·μm)；n(dp) indicate aerosol scale spectrum Particle density distribution function, 1/ (m3·μm)；V(Dp) indicate
The final Sedimentation Velocity of raindrop, m/s；E(Dp,dp) indicate raindrop to the arresting efficiency of particulate matter；(formula 3) shows usually to influence
The factor of rainfall removing coefficient includes raindrop to the arresting efficiency of particulate matter, raindrop final Sedimentation Velocity, raindrop and aerosol particle
Diameter spectral distribution function；
1.2, arresting efficiency E (D of the raindrop to aerosolp,dp) seek:
Each parameter definition is as follows in formula:
Here DdiffFor Particle diffusion coefficients；St is particle Stokes number；τ is the particle characteristics time；μa/μwIt is pneumatic for water-
Mechanics viscosity ratio.
The first item of (formula 4) represents Blang's diffusion, and Section 2, which represents, to be intercepted, and Section 3 represents inertial collision；Section 3
Only it is greater than St in St*Just effectively；
1.3, raindrop final Sedimentation Velocity V (Dp) is sought:
Raindrop final Sedimentation Velocity is predicted using following formula, it may be assumed that
V(Dp)=4854Dpexp(-1.95Dp) (formula 5)
Table 1 calculates raindrop final Sedimentation Velocity V (Dp) calculation formula summarize (cm/s)
D in tablepUnit is cm.
1.4, raindrop number scale Spectral structure n (Dp) is sought:
n(Dp)=n0exp(-ψDp) in (formula 6) formula, n0=8 × 1031/(m3Mm), slope factor ψ=
4.1I-0.21, wherein I is rainfall intensity, mm/h.N (D hereinp) unit be 1/ (m3Mm), DpUnit be mm；
Heterogeneity, different time and the precipitation of different location, raindrop size distribution will be different, however, Marshall-Paar
Silent exponential distribution is generally obtained the result close to fact to the stability rainfall of middle latitude continent；Therefore, the index is now used
Distribution is to provide rain-induced attenuation, and the diameter range of raindrop is taken as 0.2-5.8mm；
1.5, Aerosol size distribution n (dp) is sought:
Existing research all shows that atmospheric aerosol size distribution approximation obeys logarithm normal distribution, and aerosol scale
Spectral structure can regard the superposition of three kinds of logarithm normal distributions as, and the spectral distribution function of this compound lognormal form is such as
Under:
In formula, NiRepresent the particulate matter total quantity of i-th kind of distribution, RiRepresent the geometrical mean radius of i-th kind of distribution, σiGeneration
The geometric standard deviation of i-th kind of table distribution, their value have determined the spectral shape and particulate particle diameter distribution of aerosol
Range size；
Now indicate the scale Spectral structure of aerosol using formula (formula 7), related parameter reference therein is from Jaenicke
As a result, and be listed in table 2:
The parameter of 2 three kinds of aerosol extinction types of table
Based on the city parameter and formula (formula 6) in table 2, aerosols from major cities mass concentration and partial size spectral distribution function can be obtained
Transforming relationship, see below formula:
In formula, MpmRepresent aerosol quality and concentration, CjFor the particle size intervals of use, CpmIt is related with aerosol particle size range,
Other parameters can be shown in Table city a line in 2；The aerosol mass of the research area is found according to the sampling observation to research area
Concentration is about 1.7g/cm3, now use density of this value as aerosol；In addition, study carefully simulation calculate when, by aerosol with
0.001 μm is divided for interval；
Based on the above analysis, Particle density partial size Spectral structure, simultaneously is now converted for aerosol quality and concentration by formula (formula 8)
Raindrop scale Spectral structure, raindrop terminal sedimentation speed are respectively obtained by formula (formula 6), (formula 5), (formula 4) and (formula 3)
Degree, raindrop, to the removing coefficient of polydispersed aerosol, obtain gas eventually by (formula 2) to the arresting efficiency of aerosol and rainfall
Colloidal sol mass concentration with rain time changing rule；
It is calculated to solve the double integral of formula (formula 3), now uses rectangle algorithm, simultaneously, it is assumed that partial size is identical or phase
Close aerosol feature having the same and dynamic behavior, these aerosols can be in numerical estimations with an appropriate number of virtual
Representated by aerosol, i.e., every virtual aerosol has the weight of certain amount, to represent the practical aerosol of respective number, this
Sample, just sets up rainfall to the removing prediction model of polydispersed aerosol, strong with rainfall to simulate aerosol quality and concentration c (t)
Degree and the changing rule of time；
2, polydispersed aerosol Modifying model and verifying are removed in rainfall
Selection verifying area, and in verifying area within 2016~2018 observation phases, only statistical data analysis is effective
And continuous rainfall is more than 4 hours catchments, is obtained:
Λ=(ln (c0)-ln (c (t))/t (formula 9)
Parameter in formula can be found in the explanation of formula (formula 2)；
According to (formula 9) and 12 daily rain amount April in 2016 to fine grain removing situation, rainfall can be obtained to fine grain clear
Except coefficient is 3.0 × 10-5s-1；And find out, on April 12nd, 2016 12:00 to 17:00 this section of rainfall, be averaged rainfall it is strong
Degree is 0.9mm/h.
Polydispersed aerosol prediction model is removed according to the rainfall built up, estimates 12 daily rain amount April in 2016 to fine grained
Removing；The parameter Ta of (formula 4) is taken as 273.15K, μ in modelaTake 1.72 × 10-5Pas, μwTake 1.792 × 10-3pa·
S, ρaTake 1.29kg/m3, λ is taken as 6.53 × 108m；Using the city parameter in table 2；
The removing coefficient that model is calculated brings (formula 2) into, and you can get it fine grained is under 0.9mm/h rainfall intensity
Change with time rule；
It using above-mentioned similar method, can ask within 2016~2018 observation phases, continuous rainfall is more than 4 hours realities
Survey rainfall removing coefficient and simulated rainfall removing coefficient；As a result it is listed in table 3:
Rainfall removing coefficient Actual measurement value model calculation value compares under the different rainfall intensities of table 3
In a linear relationship between rainfall removing coefficient model calculation value and Actual measurement value, relational expression is as follows:
Λs=1.59 × 10-5+0.61Λm,R2=0.7 (formula 10)
Therefore, formula (formula can be passed through to the removing coefficient model calculation value of fine grained range particle by verifying regional rainfall
10) it is modified.
Further, in the step 2 on April 12nd, 2016 12:00-17:00 period wind speed average value ± standard
Difference is 1.2m/s.From the point of view of calculated result, wind speed is to the certain effect that is diffused with of aerosol, but in a short time, with rainfall phase
Than being relatively a small amount of.
After adopting the above structure, the invention has the following beneficial effects: one kind of the present invention is increased rain artificially, to remove fine grained pre-
Model is surveyed, using existing result of study, on the basis of considering polydispersed aerosol distribution, by theory analysis and to observation
As a result discussion, come the cleaning effect estimated and evaluate rainfall to particulate matter, to provide necessary reason for follow-up study
By basis.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
It obtains other drawings based on these drawings.
Fig. 1 the present invention in raindrop final Sedimentation Velocity with raindrop diameter variation diagram.
The probability density distribution figure of aerosol Particle density is surveyed in Fig. 2 present invention.
Fig. 3 the present invention in fine grained with rainfall hour variation characteristic figure.
Analog variation characteristic pattern of the fine grained in 0.9mm/h at any time in Fig. 4 present invention.
Fig. 5 is the relational graph of the fine grained rainfall removing coefficient analogue value and Actual measurement value in the present invention.
Actual measurement and model calculation value comparison diagram in Fig. 6 present invention.
Specific embodiment
The present invention will be further described below with reference to the drawings.
Referring to as shown in Figure 1, present embodiment the technical solution adopted is that: its establishment step is as follows:
1, the foundation that polydispersed aerosol theoretical model is removed in rainfall (removes theoretical, choosing according to existing aerosol rainfall
It selects and establishes suitable rainfall and remove polydispersed aerosol theoretical model, for predicting removing of the rainfall to atmospheric aerosol, and
Estimate aerosol quality and concentration with the changing rule of rain time):
1.1, the foundation of model formation:
According to rainfall purification theory under cloud, the governing equation that atmospheric aerosol is removed in rainfall is expressed as follows:
C (t) is the aerosol quality and concentration of t moment, μ g/m in formula3；Λ represents rainfall removing coefficient (s-1)；
It is assumed that rainfall removing coefficient Λ does not change at any time, then the solution of equation (formula 1) are as follows:
C (t)=c0C in exp (- Λ t) (formula 2) formula0Aerosol mass when starting in atmosphere is cleaned for rainfall
Concentration, μ g/m3；T is the scavenging period calculated when being cleaned and started with precipitation, s；
From equation (formula 2) as can be seen that obtain aerosol quality and concentration in atmosphere with the changing rule of rain time,
Obtaining rainfall removing coefficient Λ is a critical issue；For the rainfall removing coefficient Λ of polydispersed aerosol, by following public
Formula acquires:
D in formulapAnd dpThe diameter of raindrop and particulate matter is respectively indicated, μm；n(Dp) indicate raindrop scale spectrum number concentration
Distribution function, 1/ (m3·μm)；n(dp) indicate aerosol scale spectrum Particle density distribution function, 1/ (m3·μm)；V(Dp) indicate
The final Sedimentation Velocity of raindrop, m/s；E(Dp,dp) indicate raindrop to the arresting efficiency of particulate matter；The trapping effect that single raindrop generate
Rate E (Dp,dp) refer in its section is inswept in raindrop dropping process region, the aerosol number trapped in the unit time with should
The ratio of the total number of particles passed through in area；Usual arresting efficiency assume it is equal with collision efficiency, that is, assume particulate matter with
Collision between raindrop is adherency completely (being captured after collision), this assumes for dp/Dp< < 1 is reasonable；Since gas is molten
The movement velocity of glue be compared with the final Sedimentation Velocity of raindrop it is relatively a small amount of, therefore, speed of related movement between the two can be with
Ignore；The factor that equation (formula 3) shows usually to influence rainfall removing coefficient includes arresting efficiency of the raindrop to particulate matter, rain
Drip final Sedimentation Velocity, the gentle aerosol particle size spectral distribution function of raindrop；
1.2, arresting efficiency E (D of the raindrop to aerosolp,dp) seek:
E(Dp,dp) be the various power resultant forces that aerosol particle and raindrop mutually move result.For example, particulate matter is with fluid
When moving across raindrop, it may be captured due to Blang's diffusion or interception function.It intercepts and occurs when particulate matter is with fluid
It moves to apart from raindrop dpWhen/2.Big particulate matter (dp> 3 μm) due to cannot when being moved around raindrop with biggish inertia
The direction of motion is rapidly changed with fluid, therefore, is intended to occur inertial collision to be captured.It intercepts and inertial collision has very greatly
Correlation, intercept only consider particulate matter size and ignore its quality, and inertial collision then be consider particulate matter quality and neglect
Omit its size:
Blang's diffusion, intercept and inertial collision be generally considered to be in the wet reset procedure of aerosol under cloud three it is most important
Trap mechanism；In practical applications, a calculating E (D is proposed by non-dimension analysis and Binding experiment datap,dp) public affairs
Formula, expression formula are as follows:
Each parameter definition is as follows in formula:
Here DdiffFor Particle diffusion coefficients；St is particle Stokes number；τ is the particle characteristics time (when also known as relaxing
Between)；μa/μwFor water-aerodynamics viscosity ratio.
The first item of equation (formula 4) represents Blang's diffusion, and Section 2, which represents, to be intercepted, and Section 3 represents inertial collision.It needs
It is noted that Section 3 is only greater than St in St*Just effectively；
1.3, raindrop final Sedimentation Velocity V (Dp) is sought:
Raindrop final Sedimentation Velocity V (Dp) it is another parameter in rainfall removing coefficient formula, refer to that raindrop are finally steady
Fix the speed of drop.Due to the diversity of rainfall form, the number obtained according to the raindrop descent of observation and laboratory simulation
According to some empirical equations for calculating whereabouts raindrop final Sedimentation Velocity are listed in table 1；
To compare clear period, the raindrop final Sedimentation Velocity V (D for now providing empirical equation each in table 1p) straight with raindrop
Diameter DpVariation be plotted in Fig. 1；
From figure 1 it appears that there is the result of 4 research in DpIt is essentially identical less than in the range of 6mm, but compare
1013hPa, under the conditions of 20 DEG C in still air water droplet whereabouts terminal velocity, now predict that raindrop terminal is heavy using following formula
Reduction of speed degree:
V(Dp)=4854Dpexp(-1.95Dp) (formula 5)
It can also be obtained from table 1, the raindrop final Sedimentation Velocity that the formula that Atlas etc. is provided for 1973 calculates is straight in raindrop
Diameter is negative value when being less than 0.108mm, and the formula that Brandes etc. is provided is negative value when raindrop diameter is less than 0.02mm.Certainly, lead to
Often the water droplet by diameter in atmosphere greater than 0.2mm is known as raindrop, and the water droplet less than 0.2mm is known as water dust.Therefore, from actual angle
From the point of view of, the two formula are used for the calculating of raindrop final Sedimentation Velocity under cloud also and no problem.
Table 1 calculates raindrop final Sedimentation Velocity V (Dp) calculation formula summarize (cm/s)
D in tablepUnit is cm.
1.4, raindrop number scale Spectral structure n (Dp) is sought:
Know the details of raindrop scale spectral distribution function for understanding that particulate matter removes mechanism under cloud, assessment removes and is
Number and the Microphysicalization improved in numerical weather model, Atmospheric Chemistry transmission mode are helpful.Since Marshall
After Palmer pionerring research, many researchers study raindrop size distribution model, and propose many use
In the empirical relational expression of description raindrop number distribution.Analytic results show that raindrop size distribution generally obeys negative exponent distribution,
In, most popular is Marshall-Palmer (Marshall-Palmer) exponential distribution, and relational expression is as follows:
n(Dp)=n0exp(-ψDp) in (formula 6) formula, n0=8 × 1031/(m3Mm), slope factor ψ=
4.1I-0.21, wherein I is rainfall intensity, mm/h.N (D hereinp) unit be 1/ (m3Mm), DpUnit be mm.
It should also be noted that heterogeneity, different time and the precipitation of different location, raindrop size distribution will be different, however,
Marshall-Palmer index distribution is generally obtained the result close to fact to the stability rainfall of middle latitude continent；Therefore, existing
Rain-induced attenuation is provided using the exponential distribution, and the diameter range of raindrop is taken as 0.2-5.8mm.
1.5, Aerosol size distribution n (dp) is sought:
Existing research all shows that atmospheric aerosol size distribution approximation obeys logarithm normal distribution, and aerosol scale
Spectral structure can regard the superposition of three kinds of logarithm normal distributions as.The spectral distribution function of this compound lognormal form is such as
Under:
In formula, NiRepresent the particulate matter total quantity of i-th kind of distribution, RiRepresent the geometrical mean radius of i-th kind of distribution, σiGeneration
The geometric standard deviation of i-th kind of table distribution, their value have determined the spectral shape and particulate particle diameter distribution of aerosol
Range size.
Now indicate the scale Spectral structure of aerosol using formula (formula 7), related parameter reference therein is from Jaenicke
As a result, and being listed in table 2；
The parameter of 2 three kinds of aerosol extinction types of table
Based on the city parameter and formula (formula 6) in table 2, aerosols from major cities mass concentration and partial size spectral distribution function can be obtained
Transforming relationship, see below formula:
In formula, MpmRepresent aerosol quality and concentration, CjFor the particle size intervals of use, CpmIt is related with aerosol particle size range,
Other parameters can be shown in Table city a line in 2.According to Jiang Gao etc.[28]The aerosol quality and concentration in observation discovery Shanghai is sampled to Shanghai
About 1.7g/cm3, now use density of this value as aerosol；In addition, when studying carefully simulation calculating, by aerosol with 0.001 μm
It is divided for interval, for example, the city parameter provided with table 2, can obtain and its number probability density distribution is as shown in Figure 2:
Based on the above analysis, Particle density partial size Spectral structure, simultaneously is now converted for aerosol quality and concentration by formula (formula 8)
Raindrop scale Spectral structure, raindrop terminal sedimentation speed are respectively obtained by formula (formula 6), (formula 5), (formula 4) and (formula 3)
Degree, raindrop, to the removing coefficient of polydispersed aerosol, obtain gas eventually by (formula 2) to the arresting efficiency of aerosol and rainfall
Colloidal sol mass concentration with rain time changing rule.
It is calculated to solve the double integral of formula (formula 3), now uses rectangle algorithm, simultaneously, it is assumed that partial size is identical or phase
Close aerosol feature having the same and dynamic behavior, these aerosols can be in numerical estimations with an appropriate number of virtual
Representated by aerosol, i.e., every virtual aerosol has the weight of certain amount, to represent the practical aerosol of respective number, this
Sample, just sets up rainfall to the removing prediction model of polydispersed aerosol, strong with rainfall to simulate aerosol quality and concentration c (t)
Degree and the changing rule of time.
In view of model above is proposed under the premise of it is assumed that not chemically reacting between aerosol, and in practice
Interaction (such as dynamics and thermodynamic process) sufficiently complex, mould since various regions aerosol component is different, between aerosol
In quasi-, ignoring and simplifying and can bring the deviation of calculated result to certain mechanism.Therefore, field data calculating will be first passed through below
Rainfall removing coefficient verifies above-mentioned rainfall and removes polydispersed aerosol model in the applicability in Guilin, and provides to prediction result
Appropriate amendment, obtains actual removing coefficient Λ.
2, polydispersed aerosol Modifying model and verifying are removed in rainfall
Guilin City's actual measurement on December 11,1 day~2018 January in 2016 rainfall, fine grained, wind speed and direction data are come
Derived from national environmental protection data center.2016~2018 Guilin City's rainfall hourages 1906 hours.
Within 2016~2018 observation phases, only statistical data analysis is effective and continuous rainfall is more than rainfall in 4 hours
Event.Fine grained when now by wherein continuous rainfall, which is shown in Fig. 3 with the concentration variation characteristic of rain time, (can represent rainfall intensity
For the continuous type rainfall of 0.9mm/h), abscissa is rainfall corresponding hour in figure, and the number for scheming top represented in corresponding hour
Rainfall intensity (unit, mm/h).
From figure 3, it can be seen that on April 12nd, 2016, fine grained decreased significantly trend with the growth of rain time, experience
After the rainfall of 6 hours, fine grained is from 62 μ g/m3It is reduced to 36 μ g/m3.It can be obtained according to formula (formula 2):
Λ=(ln (c0)-ln (c (t))/t (formula 9)
Parameter in formula can be found in the explanation of formula (formula 2).
According to formula (formula 9) and 12 daily rain amount April in 2016 to fine grain removing situation, rainfall can be obtained to fine grain
Removing coefficient is 3.0 × 10-5s-1.From figure 3, it can be seen that this section of rainfall of 12:00 to 17:00 on April 12nd, 2016, puts down
Equal rainfall intensity is 0.9mm/h.
Polydispersed aerosol prediction model is removed according to the rainfall that 5.1 sections are built up, estimates 12 daily rain amount April in 2016 to thin
The removing of particle.It should be noted that the parameter Ta of (formula 4) is taken as 273.15K, μ in modelaTake 1.72 × 10-5Pas,
μwTake 1.792 × 10-3Pas, ρaTake 1.29kg/m3, λ is taken as 6.53 × 108m.Show to take 283.15K, μ if being computedaIt takes
1.78×10-5Pas, μwTake 1.519 × 10-3Pas, ρaTake 1.248kg/m3, λ is taken as 6.53 × 108The rainfall that m is calculated is clear
The rainfall removing coefficient difference calculated when except coefficient and 273.15K is respectively less than 4%, therefore, is now all made of parameter when 273.15K
It is calculated.In view of Guilin City's aerosol partial size Spectral structure will be different, with ocean, rural area and the city provided in table 2
Aerosol partial size Spectral structure parameter, on April 12nd, 2016 can be calculated, fine grain removing coefficient is calculated in rainfall
Removing coefficient, the partial size Spectral structure of ocean, rural area and city influences very little for the result of removing coefficient.Therefore, estimate now
When counting Guilin City's rainfall to fine grained removing, using the city parameter in table 2.
The removing coefficient that model is calculated brings (formula 2) into, and you can get it fine grained is under 0.9mm/h rainfall intensity
Change with time rule, as shown in Figure 4.
From the point of view of Fig. 4 and formula 3, the fine grained of polydispersed aerosol prediction model estimation is removed in the rainfall that 5.1 sections are established
Feature change with time compared with actual measurement, trend is consistent.The removing coefficient that model calculates is 1.75 × 10-5s-1, and actual measurement meter
The removing coefficient 3.0 × 10 of calculation-5s-1Substantially quite, measured value is 1.7 times of the analogue value.
It using above-mentioned similar method, can ask within 2016~2018 observation phases, continuous rainfall is more than 4 hours realities
Survey rainfall removing coefficient and simulated rainfall removing coefficient.As a result it is listed in table 3.
Rainfall removing coefficient Actual measurement value model calculation value compares under the different rainfall intensities of table 3
Data in table 3 are plotted in Fig. 5 by the relationship of rainfall removing coefficient measured value and the analogue value in order to obtain.
Fig. 5 shows in a linear relationship between rainfall removing coefficient model calculation value and Actual measurement value, and relational expression is as follows:
Λs=1.59 × 10-5+0.61Λm,R2Therefore, Guilin rainfall is to fine grained range for=0.7 (formula 10)
The removing coefficient model calculation value of particle can be modified by formula (formula 10).
For the difference of model calculation value after intuitively comparing measured value and amendment, by April 12nd, 2016, fine grain reality
It surveys and model calculation value is shown in Fig. 6.
After Fig. 6 shows that removing polydispersed aerosol model to the rainfall that 5.1 sections are established carries out above-mentioned amendment, it is calculated
Fine grained and measured value coincide preferably, can be used to estimate the fine particle mass concentration in Guilin City's atmosphere with the change of rainfall
Change.
Further, in the step 2 on April 12nd, 2016 12:00-17:00 period wind speed average value ± standard
Difference is 1.2m/s.From the point of view of calculated result, wind speed is to the certain effect that is diffused with of aerosol, but in a short time, with rainfall phase
Than being relatively a small amount of.
After adopting the above structure, present embodiment has the beneficial effect that a kind of bright people of present embodiment
Work increases rain and removes fine grained prediction model, is led on the basis of considering polydispersed aerosol distribution using existing result of study
Theory analysis and the discussion to observed result are crossed, come the cleaning effect estimated and evaluate rainfall to particulate matter, so as to for after
Continuous research provides necessary rationale.
The above is only used to illustrate the technical scheme of the present invention and not to limit it, and those of ordinary skill in the art are to this hair
The other modifications or equivalent replacement that bright technical solution is made, as long as it does not depart from the spirit and scope of the technical scheme of the present invention,
It is intended to be within the scope of the claims of the invention.
Claims (2)
1. one kind, which is increased rain artificially, removes fine grained prediction model, it is characterised in that: its establishment step is as follows:
(1), the foundation of polydispersed aerosol theoretical model is removed in rainfall:
(1.1), the foundation of model formation:
According to rainfall purification theory under cloud, the governing equation that atmospheric aerosol is removed in rainfall is expressed as follows:
C (t) is the aerosol quality and concentration of t moment, μ g/m in formula3；Λ represents rainfall removing coefficient (s-1)；
It is assumed that rainfall removing coefficient Λ does not change at any time, then the solution of (formula 1) are as follows:
C (t)=c0Exp (- Λ t) (formula 2)
C in formula0Aerosol quality and concentration when starting in atmosphere, μ g/m are cleaned for rainfall3；T is to calculate when being cleaned and started with precipitation
Scavenging period, s；
It is obtained from equation (formula 2) as can be seen that obtain aerosol quality and concentration in atmosphere with the changing rule of rain time
Rainfall removing coefficient Λ is a critical issue；For the rainfall removing coefficient Λ of polydispersed aerosol, asked by following formula
:
D in formulapAnd dpThe diameter of raindrop and particulate matter is respectively indicated, μm；n(Dp) indicate that the number concentration of raindrop scale spectrum is distributed
Function, 1/ (m3·μm)；n(dp) indicate aerosol scale spectrum Particle density distribution function, 1/ (m3·μm)；V(Dp) indicate raindrop
Final Sedimentation Velocity, m/s；E(Dp,dp) indicate raindrop to the arresting efficiency of particulate matter；(formula 3) shows usually to influence rainfall
The factor of removing coefficient includes that raindrop compose the arresting efficiency of particulate matter, raindrop final Sedimentation Velocity, the gentle aerosol particle size of raindrop
Distribution function；
(1.2), arresting efficiency E (D of the raindrop to aerosolp,dp) seek:
Each parameter definition is as follows in formula:
Here DdiffFor Particle diffusion coefficients；St is particle Stokes number；τ is the particle characteristics time；μa/μwFor water-aerodynamics
Viscosity ratio.
The first item of (formula 4) represents Blang's diffusion, and Section 2, which represents, to be intercepted, and Section 3 represents inertial collision；Section 3 only exists
St is greater than St*Just effectively；
(1.3), raindrop final Sedimentation Velocity V (Dp) is sought:
Raindrop final Sedimentation Velocity is predicted using following formula, it may be assumed that
V(Dp)=4854Dpexp(-1.95Dp) (formula 5)
(1.4), raindrop number scale Spectral structure n (Dp) is sought:
n(Dp)=n0exp(-ψDp) (formula 6)
In formula, n0=8 × 1031/(m3Mm), slope factor ψ=4.1I-0.21, wherein I is rainfall intensity, mm/h.N herein
(Dp) unit be 1/ (m3Mm), DpUnit be mm；
Heterogeneity, different time and the precipitation of different location, raindrop size distribution will be different, however, Marshall-Palmer refers to
Number distribution is generally obtained the result close to fact to the stability rainfall of middle latitude continent；Therefore, the exponential distribution is now used
Provide rain-induced attenuation, and the diameter range of raindrop is taken as 0.2-5.8mm；
(1.5), Aerosol size distribution n (dp) is sought:
Existing research all shows that atmospheric aerosol size distribution approximation obeys logarithm normal distribution, and aerosol scale spectrum point
Cloth can regard the superposition of three kinds of logarithm normal distributions as, and the spectral distribution function of this compound lognormal form is as follows:
In formula, NiRepresent the particulate matter total quantity of i-th kind of distribution, RiRepresent the geometrical mean radius of i-th kind of distribution, σiRepresent i-th
Kind distribution geometric standard deviation, their value determined aerosol spectral shape and particulate particle diameter distribution range it is big
It is small；
The scale Spectral structure that aerosol is now indicated using formula (formula 7), obtains aerosols from major cities mass concentration and partial size Spectral structure
The transforming relationship of function, sees below formula:
In formula, MpmRepresent aerosol quality and concentration, CjFor the particle size intervals of use, CpmIt is related with aerosol particle size range, according to
The aerosol quality and concentration of the research area, which is about 1.7g/cm, to be found to the sampling observation of research area3, now use this value conduct
The density of aerosol；In addition, aerosol is divided with 0.001 μm for interval when studying carefully simulation calculating；
Based on the above analysis, Particle density partial size Spectral structure is now converted for aerosol quality and concentration by formula (formula 8) and is passed through
Formula (formula 6), (formula 5), (formula 4) and (formula 3) respectively obtains raindrop scale Spectral structure, raindrop final Sedimentation Velocity, rain
It drips to the arresting efficiency of aerosol and rainfall to the removing coefficient of polydispersed aerosol, obtains aerosol eventually by (formula 2)
Mass concentration with rain time changing rule；
It is calculated to solve the double integral of formula (formula 3), now uses rectangle algorithm, simultaneously, it is assumed that partial size is same or similar
Aerosol feature having the same and dynamic behavior, these aerosols can be molten with an appropriate number of virtual gas in numerical estimation
Representated by glue, i.e., every virtual aerosol has the weight of certain amount, to represent the practical aerosol of respective number, in this way,
Rainfall is just set up to the removing prediction model of polydispersed aerosol, with simulate aerosol quality and concentration c (t) with rainfall intensity and
The changing rule of time；
(2), polydispersed aerosol Modifying model and verifying are removed in rainfall
It selects to verify area, and in verifying area within 2016~2018 observation phases, only statistical data analysis is effective and connects
Continuous rainfall is more than 4 hours catchments, is obtained:
Λ=(ln (c0)-ln (c (t))/t (formula 9)
Parameter in formula can be found in the explanation of formula (formula 2)；
According to (formula 9) and 12 daily rain amount April in 2016 to fine grain removing situation, can obtain rainfall is to fine grain removing
Number is 3.0 × 10-5s-1；And find out, on April 12nd, 2016 12:00 to 17:00 this section of rainfall, average rainfall intensity is
0.9mm/h。
Polydispersed aerosol prediction model is removed according to the rainfall built up, estimates 12 daily rain amount April in 2016 to fine grain clear
It removes；The parameter Ta of (formula 4) is taken as 273.15K, μ in modelaTake 1.72 × 10-5Pas, μwTake 1.792 × 10-3Pas, ρa
Take 1.29kg/m3, λ is taken as 6.53 × 108m；
The removing coefficient that model is calculated brings (formula 2) into, you can get it fine grained under 0.9mm/h rainfall intensity at any time
Between changing rule；
It using above-mentioned similar method, can ask within 2016~2018 observation phases, continuous rainfall is more than 4 hours actual measurement drops
Rain removing coefficient and simulated rainfall removing coefficient；It is in a linear relationship between rainfall removing coefficient model calculation value and Actual measurement value,
Relational expression is as follows:
Λs=1.59 × 10-5+0.61Λm,R2=0.7 (formula 10)
Therefore, verify regional rainfall to the removing coefficient model calculation value of fine grained range particle can by formula (formula 10) come
It is modified.
2. one kind according to claim 1, which is increased rain artificially, removes fine grained prediction model, it is characterised in that: the step
(2) on April 12nd, 2016 12:00-17:00 period wind speed mean+SD be 1.2m/s.
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