阅读说明：本技术 一种静止气象卫星观测中获取近地面pm2.5浓度的方法及系统 (Method and system for acquiring near-ground PM2.5 concentration in static meteorological satellite observation ) 是由 陈林 田林 梁红丽 高玲 张鹏 于 2021-05-13 设计创作，主要内容包括：本发明公开了一种静止气象卫星观测中获取近地面PM2.5浓度的方法及系统,利用新一代静止气象卫星观测辐射,脱离气溶胶光学厚度这一中间变量,直接反演近地面PM2.5浓度的方法。瞄准近地面PM2.5浓度高分辨率时空分布遥感连续监测这一目标,基于风云四号静止气象卫星的高时空分辨的直接连续观测辐射,突破传统近地面PM2.5浓度估算中对气溶胶光学厚度的依赖关系,考虑卫星光谱和时间约束作用,提出一种直接从静止气象卫星观测中获取近地面PM2.5的算法,促进大气环境卫星遥感监测研究深入发展。(The invention discloses a method and a system for acquiring the concentration of near-ground PM2.5 in static meteorological satellite observation, which are methods for directly inverting the concentration of the near-ground PM2.5 by utilizing the intermediate variable of the new generation of static meteorological satellite observation radiation and aerosol optical thickness. Aiming at the target of near-ground PM2.5 concentration high-resolution space-time distribution remote sensing continuous monitoring, based on the high-space-time-resolution direct continuous observation radiation of a wind cloud four-model static meteorological satellite, the method breaks through the dependence on the optical thickness of aerosol in the traditional near-ground PM2.5 concentration estimation, considers the satellite spectrum and time constraint effect, provides an algorithm for directly obtaining the near-ground PM2.5 from static meteorological satellite observation, and promotes the deep development of atmospheric environment satellite remote sensing monitoring research.)

1. A method for obtaining near-ground PM2.5 concentration in geostationary meteorological satellite observations, the method comprising:

the method comprises the steps of monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data based on a ground station, and constructing a characteristic quantity data set;

performing optimization training on a pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by using a characteristic quantity data set, and calculating a target function;

performing second-order Taylor expansion on the target function during each iteration to obtain an optimized target function;

adding a threshold value to the optimized objective function, and performing pruning treatment to obtain a loss function after node segmentation so as to determine new monitoring information;

inputting new monitoring information, and estimating the near-ground PM2.5 concentration through satellite observation radiation.

2. The method of claim 1, wherein: the construction of the characteristic quantity data set comprises the following steps:

collecting ground station monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data, and constructing multi-source truth samples with different space-time scales;

and obtaining a matching data set formed by characteristic quantities corresponding to the multi-source truth-value samples, and using the matching data set for training and verifying the statistical model.

3. The method of claim 1, wherein: the satellite remote sensing inversion near-ground PM2.5 concentration statistical model is constructed by adopting an optimized distributed gradient enhancement theory.

4. The method of claim 1, wherein: the optimization training of the pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by adopting the characteristic quantity data set comprises the following steps:

selecting various surface and atmospheric parameters as characteristic items, and carrying out sensitivity analysis on the characteristic items according to a haze physical mechanism;

initializing the weight of the statistical model according to the sensitivity analysis result;

the model carries out second-order Taylor expansion on the loss function, the loss function is fitted by utilizing the information of the first-order derivative and the second-order derivative, and the optimal solution is obtained through the following formula:

in the formula (I), the compound is shown in the specification,representing the objective function at the t iteration; y is_iRepresenting the corresponding truth value of the original sample;representing the predicted value of the sample at the t-1 iteration in the model; f. of_t(x_i) Representing the predicted value of the sample at the t iteration of the model; omega (f)_t) Is a regular term.

5. The method of claim 4, wherein: performing a second order Taylor expansion on the objective function by:

in the formula (2), g is a first derivative, and h is a second derivative.

6. The method of claim 1, wherein: adding a threshold value for the optimization objective function, and performing pruning treatment to obtain a loss function after node segmentation, wherein the loss function comprises the following steps:

the standard for searching the segmentation point is maximization, when the tree structure is determined, the structural score of the tree is only related to the first derivative and the second derivative, and the smaller the score is, the better the structure is;

starting from a single leaf node, adding nodes to the tree by iterative splitting to obtain a loss function after node splitting:

in the formula (3), gamma is a threshold value and represents a coefficient of the leaf node number T in the regularization term, and the coefficient lambda is a coefficient of the L2 modulo square of the leaf score in the regularization term, and the leaf score is smoothed; g_R、G_LAnd H_R、H_LThe first-order second-order derivatives of the left and right subtrees of the current node are respectively.

7. The method of claim 1, wherein: the determining new monitoring information comprises:

first, the remaining information of the last time is determined, and a value between 0 and 1 is calculated by formula (4):

f_t＝σ(W_f[h_t-1,x_t]+b_f) (4)

wherein h is_t-1Denotes the last time result, x_tIndicating the current time, calculating the remaining information f by forgetting the gate_t，W_fRepresenting a forgetting gate weight, b_fTo forget the offset vector of the gate, σ represents the sigmod function:

the output range of the sigmoid function is 0 to 1, wherein 0 represents all abandons, and 1 represents all reserves;

adding new information to the observation information at the current moment, and using h_t-1And x_tDeciding information i to update_tAnd then reuse h_t-1And x_tObtaining new candidate information through a neural network tanh layerThis information may be updated into the new monitoring information; finally, theUpdating old monitoring information C_t-1Updated to new monitoring information C_t；

i_t＝σ(W_i[h_t-1,x_t]+b_i)

The updated rule is that new cell information C is obtained by (4) selecting to forget a part of the old information and (5) selecting to add a part of the candidate information_t：

8. The method of claim 2, wherein: the inputting of new monitoring information and the estimation of the near-ground PM2.5 concentration through satellite observation radiation comprise the following steps: the method comprises the steps of establishing a regression relation between apparent radiance of a direct observation channel of a cloud-free observation area of the geostationary satellite, surface parameters, a satellite observation angle, meteorological elements and near-ground PM2.5 observation data based on a statistical model, carrying out near-ground PM2.5 concentration inversion by fully utilizing high timeliness of satellite data, and obtaining a near-ground PM2.5 concentration monitoring value with high space-time resolution.

9. A system for obtaining near-surface PM2.5 concentrations in geostationary meteorological satellite observations, the system comprising:

the construction module is used for monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data based on a ground station, and constructing a characteristic quantity data set;

the calculation module is used for carrying out optimization training on a pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by adopting a characteristic quantity data set and calculating a target function;

the acquisition module is used for performing second-order Taylor expansion on the target function during each iteration to obtain an optimized target function;

the processing module is used for adding a threshold value to the optimized objective function, performing pruning processing to obtain a loss function after node segmentation so as to determine new monitoring information;

and the estimation module is used for inputting new monitoring information and estimating the concentration of the near-ground PM2.5 through satellite observation radiation.

Technical Field

The invention relates to the technical field of meteorological satellite remote sensing, in particular to a method and a system for acquiring near-ground PM2.5 concentration in static meteorological satellite observation.

Background

The near-ground PM2.5 concentration monitoring is the basis of pollution control, and China urgently needs to develop corresponding research and measures to strengthen and improve monitoring technology so as to accurately grasp air quality conditions and pollution rules and mechanisms and further promote domestic air quality monitoring and pollution control. The traditional near-ground PM2.5 concentration monitoring is mainly based on ground acquisition, monitoring network and other modes, although the method can provide accurate near-ground PM2.5 concentration monitoring data all the day without being influenced by weather, the space coverage of a ground measurement station is very limited, regional and global air quality evaluation data is difficult to provide, and different types of measurement methods and monitoring instruments have different calibration, and the near-ground PM2.5 concentration distribution data with unified standard is difficult to obtain.

The satellite remote sensing data has the advantages of time and high spatial resolution, the space change and the time dynamic change of the aerosol can be quickly obtained through satellite remote sensing, the defects of observation of a ground monitoring station in time and space can be effectively overcome, the method has obvious advantages in the aspects of environmental quality current situation evaluation and emergency monitoring, particularly the development of a new generation of static meteorological satellite improves the time-space resolution of satellite observation, and the method for monitoring the concentration of air pollutants by utilizing satellite observation gradually becomes an important monitoring means. Most current research estimates the near-ground PM2.5 concentration based on satellite inversion of aerosol optical thickness secondary products, and the aerosol optical thickness products have inversion errors, which are substituted into the near-ground PM2.5 concentration estimation and cause larger uncertainty. The aerosol optical thickness product can be inverted through satellite observation radiation, theoretically, the satellite observation radiation and the near-ground PM2.5 concentration can be directly related, and the method has smaller uncertainty than a method for estimating the near-ground PM2.5 concentration through the aerosol optical thickness.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method and a system for acquiring the near-ground PM2.5 concentration in static meteorological satellite observation aiming at the characteristic that atmospheric aerosol has time sequence change, and the method and the system skip the intermediate variable of the optical thickness of the aerosol on the basis of fully analyzing the generation and monitoring physical mechanism of the near-ground PM2.5 and consider the satellite spectrum and time constraint action. The near-ground PM2.5 concentration is directly estimated through satellite observation radiation, aerosol optical thickness products are not relied on, and the near-ground PM2.5 concentration inversion accuracy is improved.

The purpose of the invention is realized by adopting the following technical scheme:

a method of acquiring near-ground PM2.5 concentrations in geostationary meteorological satellite observations, the method comprising:

the method comprises the steps of monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data based on a ground station, and constructing a characteristic quantity data set;

performing optimization training on a pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by using a characteristic quantity data set, and calculating a target function;

performing second-order Taylor expansion on the target function during each iteration to obtain an optimized target function;

adding a threshold value to the optimized objective function, and performing pruning treatment to obtain a loss function after node segmentation so as to determine new monitoring information;

inputting new monitoring information, and estimating the near-ground PM2.5 concentration through satellite observation radiation.

Preferably, the constructing of the feature quantity data set includes:

collecting ground station monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data, and constructing multi-source truth samples with different space-time scales;

and obtaining a matching data set formed by characteristic quantities corresponding to the multi-source truth-value samples, and using the matching data set for training and verifying the statistical model.

Preferably, the satellite remote sensing inversion near-ground PM2.5 concentration statistical model is constructed by adopting an optimized distributed gradient enhancement theory.

Preferably, the optimization training of the pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by using the feature quantity data set includes:

selecting various surface and atmospheric parameters as characteristic items, and carrying out sensitivity analysis on the characteristic items according to a haze physical mechanism;

initializing the weight of the statistical model according to the sensitivity analysis result;

the model carries out second-order Taylor expansion on the loss function, the loss function is fitted by utilizing the information of the first-order derivative and the second-order derivative, and the optimal solution is obtained through the following formula:

in the formula (I), the compound is shown in the specification,representing the objective function at the t iteration; y is_iRepresenting the corresponding truth value of the original sample;representing the predicted value of the sample at the t-1 iteration in the model; f. of_t(x_i) Representing the predicted value of the sample at the t iteration of the model; omega (f)_t) Is a regular term.

Further, the second order taylor expansion is performed on the objective function by the following formula:

in the formula (2), g is a first derivative, and h is a second derivative.

Preferably, the adding a threshold to the optimized objective function, and performing pruning processing to obtain a loss function after node segmentation includes:

the standard for searching the segmentation point is maximization, when the tree structure is determined, the structural score of the tree is only related to the first derivative and the second derivative, and the smaller the score is, the better the structure is;

starting from a single leaf node, adding nodes to the tree by iterative splitting to obtain a loss function after node splitting:

in the formula (3), γ is a threshold value and represents a coefficient of the leaf node number T in the regularization term, and λ is a coefficient of modulo square of L2 of the leaf score in the regularization term, and the leaf score is smoothed.

Preferably, the determining new monitoring information includes:

first, the remaining information of the last time is determined, and a value between 0 and 1 is calculated by formula (4):

f_t＝σ(W_f[h_t-1,x_t]+b_f) (4)

wherein h is_t-1Denotes the last time result, x_tIndicating the current time, calculating the remaining information f by forgetting the gate_t，W_fRepresenting a forgetting gate weight, b_fTo forget the offset vector of the gate, σ represents the sigmod function:

the output range of the sigmoid function is 0 to 1, wherein 0 represents all abandons, and 1 represents all reserves;

adding new information to the observation information at the current moment, and using h_t-1And x_tDeciding information i to update_tAnd then reuse h_t-1And x_tObtaining new candidate information through a neural network tanh layerThis information may be updated into the new monitoring information; finally, the old monitoring information C is updated_t-1Updated to new monitoring information C_t；

The updated rule is that new cell information C is obtained by (4) selecting to forget a part of the old information and (5) selecting to add a part of the candidate information_t：

Further, the inputting new monitoring information and the estimating the near-ground PM2.5 concentration through satellite observation radiation comprises: the method comprises the steps of establishing a regression relation between apparent radiance of a direct observation channel of a cloud-free observation area of the geostationary satellite, surface parameters, a satellite observation angle, meteorological elements and near-ground PM2.5 observation data based on a statistical model, carrying out near-ground PM2.5 concentration inversion by fully utilizing high timeliness of satellite data, and obtaining a near-ground PM2.5 concentration monitoring value with high space-time resolution.

A system for acquiring near-ground PM2.5 concentrations in geostationary meteorological satellite observations, the system comprising:

the construction module is used for monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data based on a ground station, and constructing a characteristic quantity data set;

the calculation module is used for carrying out optimization training on a pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by adopting a characteristic quantity data set and calculating a target function;

the acquisition module is used for performing second-order Taylor expansion on the target function during each iteration to obtain an optimized target function;

the processing module is used for adding a threshold value to the optimized objective function, performing pruning processing to obtain a loss function after node segmentation so as to determine new monitoring information;

and the estimation module is used for inputting new monitoring information and estimating the concentration of the near-ground PM2.5 through satellite observation radiation.

The invention has the beneficial effects that:

according to the method and the system for acquiring the near-ground PM2.5 concentration in the observation of the static meteorological satellite, provided by the invention, aiming at the characteristic that atmospheric aerosol has time sequence change, the characteristic of high-time resolution observation of a new generation of static meteorological satellite is fully utilized, the near-ground PM2.5 concentration is directly estimated through satellite observation radiation by observing the change of aerosol particle concentration in a time sequence and considering time constraints of previous and subsequent times, and the inversion precision of the near-ground PM2.5 concentration is improved without depending on aerosol optical thickness products.

By utilizing the method and the system provided by the invention, the near-ground PM2.5 concentration can be obtained by directly inverting the observation radiation of the wind-cloud four-satellite multichannel scanning imaging radiometer. According to the time constraint considered near-ground PM2.5 concentration method, the PM2.5 concentration inspection result of radiation inversion is observed through a wind cloud four-satellite multi-channel scanning imaging radiometer, and it can be seen that the inversion result has high consistency with a station monitoring value and a relative error is small.

Drawings

In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

FIG. 1 is a flowchart of a method for obtaining a near-ground PM2.5 concentration in geostationary meteorological satellite observations, according to an embodiment of the present invention;

FIG. 2 is a flowchart of a technique for obtaining near-ground PM2.5 directly from geostationary meteorological satellite observations as provided in an embodiment of the present invention;

fig. 3 is a schematic diagram of a PM2.5 concentration inspection result obtained by observing radiation inversion through a wind cloud four-satellite multichannel scanning imaging radiometer by the near-ground PM2.5 concentration method considering time constraints, provided in the embodiment of the present invention;

fig. 4 is an exemplary diagram of a contamination process detection and verification provided in the embodiment of the present invention (note: this diagram is a local map of china).

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.

As shown in fig. 1, the present embodiment 1 provides a method for acquiring a near-ground PM2.5 concentration in a stationary meteorological satellite observation, the method comprising:

s1, constructing a characteristic quantity data set based on the PM2.5 concentration monitored by the ground station, satellite observation radiation, earth surface and meteorological element data;

s2, optimizing and training a pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by adopting a characteristic quantity data set, and calculating a target function;

s3, performing second-order Taylor expansion on the objective function to obtain an optimized objective function during each iteration;

s4, adding a threshold value for the optimized objective function, and performing pruning to obtain a loss function after node segmentation so as to determine new monitoring information;

s5 inputs new monitoring information, and the near-ground PM2.5 concentration is estimated through satellite observation radiation.

In step S1, the constructing of the feature quantity data set includes:

collecting ground station monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data, and constructing multi-source truth samples with different space-time scales;

and obtaining a matching data set formed by characteristic quantities corresponding to the multi-source truth-value samples, and using the matching data set for training and verifying the statistical model.

And S2, constructing the near-ground PM2.5 concentration statistical model by adopting an optimized distributed gradient enhancement theory.

In step S3, the performing optimization training on the pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by using the feature quantity data set includes:

selecting various surface and atmospheric parameters as characteristic items, and carrying out sensitivity analysis on the characteristic items according to a haze physical mechanism;

initializing the weight of the statistical model according to the sensitivity analysis result;

the model carries out second-order Taylor expansion on the loss function, the loss function is fitted by utilizing the information of the first-order derivative and the second-order derivative, and the optimal solution is obtained through the following formula:

in the formula (I), the compound is shown in the specification,representing the objective function at the t iteration; y is_iRepresenting the corresponding truth value of the original sample;representing the predicted value of the sample at the t-1 iteration in the model; f. of_t(x_i) Representing the predicted value of the sample at the t iteration of the model; omega (f)_t) Is a regular term.

Performing a second order Taylor expansion on the objective function by:

in the formula (2), g is a first derivative, and h is a second derivative.

In step S4, the adding a threshold to the optimized objective function and performing pruning to obtain a loss function after node segmentation includes:

the standard for searching the segmentation point is maximization, when the tree structure is determined, the structural score of the tree is only related to the first derivative and the second derivative, and the smaller the score is, the better the structure is;

starting from a single leaf node, adding nodes to the tree by iterative splitting to obtain a loss function after node splitting:

in the formula (3), gamma is a threshold value and represents a coefficient of the leaf node number T in the regularization term, and the coefficient lambda is a coefficient of the L2 modulo square of the leaf score in the regularization term, and the leaf score is smoothed; g_R、G_LAnd H_R、H_LThe first-order second-order derivatives of the left and right subtrees of the current node are respectively.

The determining new monitoring information comprises:

first, the remaining information of the last time is determined, and a value between 0 and 1 is calculated by formula (4):

f_t＝σ(W_f[h_t-1,x_t]+b_f) (4)

wherein h is_t-1Denotes the last time result, x_tIndicating the current time, calculating the remaining information f by forgetting the gate_t，W_fRepresenting a forgetting gate weight, b_fTo forget the offset vector of the gate, σ represents the sigmod function:

the output range of the sigmoid function is 0 to 1, wherein 0 represents all abandons, and 1 represents all reserves;

adding new information to the observation information at the current moment, and using h_t-1And x_tDeciding information i to update_tAnd then reuse h_t-1And x_tObtaining new candidate information through a neural network tanh layerThis information may be updated into the new monitoring information;finally, the old monitoring information C is updated_t-1Updated to new monitoring information C_t；

The updated rule is that new cell information C is obtained by (4) selecting to forget a part of the old information and (5) selecting to add a part of the candidate information_t：

In step S5, inputting new monitoring information, and estimating the near-ground PM2.5 concentration by satellite observation radiation includes: the method comprises the steps of establishing a regression relation between apparent radiance of a direct observation channel of a cloud-free observation area of the geostationary satellite, surface parameters, a satellite observation angle, meteorological elements and near-ground PM2.5 observation data based on a statistical model, carrying out near-ground PM2.5 concentration inversion by fully utilizing high timeliness of satellite data, and obtaining a near-ground PM2.5 concentration monitoring value with high space-time resolution.

Based on the same technical concept, the invention also provides a system for acquiring the near-ground PM2.5 concentration in the static meteorological satellite observation, which comprises:

the construction module is used for monitoring PM2.5 concentration, satellite observation radiation, earth surface and meteorological element data based on a ground station, and constructing a characteristic quantity data set;

the calculation module is used for carrying out optimization training on a pre-established satellite remote sensing inversion near-ground PM2.5 concentration statistical model by adopting a characteristic quantity data set and calculating a target function;

the acquisition module is used for performing second-order Taylor expansion on the target function during each iteration to obtain an optimized target function;

the processing module is used for adding a threshold value to the optimized objective function, performing pruning processing to obtain a loss function after node segmentation so as to determine new monitoring information;

and the estimation module is used for inputting new monitoring information and estimating the concentration of the near-ground PM2.5 through satellite observation radiation.

Example 1:

by taking a wind cloud four meteorological satellite as a data source to obtain the concentration of the near-ground PM2.5 as an example, the main technical scheme is explained, and the steps of the related technical method are as shown in FIG. 2:

(1) feature quantity data set construction for statistical model training

The method is based on the PM2.5 concentration monitoring of a ground station, satellite observation radiation, earth surface and meteorological element data, and multi-source truth value samples and characteristic quantity matching data sets with different space-time scales are constructed and used for training and verifying statistical models.

In the in-orbit operation process of the satellite sensor, the problem of inconsistent satellite observation radiation can be caused due to attenuation of instrument calibration coefficients, and the training precision of the statistical model is influenced by the inconsistency of satellite observation radiation input. In order to ensure the consistency of satellite observation radiation data, satellite calibration coefficient correction is required. By means of site calibration, on-satellite calibration and the like, response characteristic decay of the satellite remote sensor in the in-orbit operation process is monitored and corrected, influences of factors such as atmospheric transmission and surface environment change on observation are evaluated and corrected, and the quality and stability of satellite observation radiation data in training are guaranteed.

In addition, in the aspect of characteristic quantity selection, the physical mechanism of haze weather is fully analyzed, and the characteristic quantity is selected in a targeted manner based on a physical model for satellite inversion of near-ground PM2.5 concentration.

(2) Statistical model construction and optimization taking into account temporal constraints

According to the method, an optimized distributed gradient enhancement theory is adopted to construct a satellite remote sensing inversion near-ground PM2.5 concentration statistical model, and the model is improved and optimized according to the training target requirement.

And selecting various surface and atmosphere parameters as characteristic items, and carrying out sensitivity analysis on the characteristic items according to a haze physical mechanism. And the weight initialization of the statistical model is carried out according to the sensitivity analysis result, and the training is carried out more specifically according to the physical mechanism, which has important influence on the convergence speed and performance of the model and has important significance for improving the training efficiency and the result precision.

The model carries out second-order Taylor expansion on the loss function, and first-order derivative and second-order derivative information are utilized, so that the loss function can be better fitted, and errors existing in the optimization process are reduced. The obtained optimal solution has higher efficiency:

in the formula (I), the compound is shown in the specification,representing the objective function at the t iteration; y is_iRepresenting the corresponding truth value of the original sample;representing the predicted value of the sample at the t-1 iteration in the model; f. of_t(x_i) Representing the predicted value of the sample at the t iteration of the model; last term omega (f)_t) Is a regular term. Performing a second-order Taylor expansion on equation (1): g is the first derivative, h is the second derivative:

the criterion for finding the segmentation point is maximization, when the tree structure is determined, the structure score of the tree is only related to the first derivative and the second derivative, and the smaller the score is, the better the structure is. While in general it is not possible to enumerate all possible tree structures and then choose the best, we choose to replace it with a greedy algorithm: we iterate the split to add nodes to the tree starting from a single leaf node. Loss function after node segmentation:

in order to limit the growth of the tree, a threshold value can be added, wherein γ in formula (3) is a threshold value, and is a coefficient of the number T of leaf nodes in the regularization term, so that the model is equivalent to pre-pruning while optimizing the objective function. In addition, a coefficient lambda is also provided in the formula (3), and is a coefficient of the square of the L2 model of the leaf score in the regularization term, so that the leaf score is smoothed, and the overfitting prevention effect is also achieved; g_R、G_LAnd H_R、 H_LThe first-order second-order derivatives of the left and right subtrees of the current node are respectively.

Meanwhile, the model needs to consider the time sequence change of the aerosol, so a time sequence training and predicting module is designed in the model construction. First, the remaining information of the last time needs to be determined, and a value between 0 and 1 is calculated by formula (4).

f_t＝σ(W_f[h_t-1,x_t]+b_f) (4)

Wherein h is_t-1The result of the last epoch, x_tIndicating the result of the current time, and calculating the reserved information f through a forgetting gate_t，W_fRepresenting a forgetting gate weight, b_fTo forget the offset vector of the gate, σ represents the sigmod function:

the output range of the sigmoid function is 0 to 1, 0 represents that all the information is discarded, 1 represents that all the information is reserved, and then how much new information is added into the observation information at the current moment is determined.

First of all by using h_t-1And x_tDeciding information i to update_tAnd then reuse h_t-1And x_tThrough a tanh layer to obtainTo new candidate informationThis information may be updated into the new monitoring information. Finally, the old monitoring information C is updated_t-1Updated to new monitoring information C_t. The updated rule is that new cell information C is obtained by (4) selecting to forget a part of the old information and (5) selecting to add a part of the candidate information_t(equation (7)).

(3) Construction of PM2.5 inversion algorithm for satellite remote sensing

On the basis of training sample data set construction and machine learning model improvement optimization, the method establishes a regression relationship between apparent radiance of a direct observation channel of a cloud-free observation area of a geostationary satellite, surface parameters, a satellite observation angle, meteorological elements and near-ground PM2.5 observation data based on a statistical model, performs near-ground PM2.5 concentration inversion by fully utilizing high timeliness of satellite data, and obtains a near-ground PM2.5 concentration monitoring product with high space-time resolution.

Firstly, data quality control needs to be carried out on each characteristic quantity in a training sample data set, and data space-time matching is carried out to correct data of different observation times and geographic positions by considering a space-time weight interpolation algorithm, so that the accuracy and consistency of training samples are ensured. On the basis, aiming at the goal of accurate inversion of the concentration of PM2.5 near the ground in diversified earth surfaces and atmospheric environments, a training scheme is designed by considering the time sequence change of aerosol observation, a training sample data set is input into a statistical model considering time constraint for training, and finally a set of remote sensing inversion model of the concentration of PM2.5 near the ground is generated. And meanwhile, according to a reserved test data set (not participating in training), performing precision effect test, and further performing training optimization on the model according to a feedback result, so that the inversion precision of the model is improved.

By using the processing method, the concentration of the PM2.5 near the ground can be directly obtained by observing radiation through a wind cloud four-satellite multi-channel scanning imaging radiometer and directly inverting the radiation. Fig. 3 shows a PM2.5 concentration check result of radiation inversion observed by a wind cloud four-satellite multichannel scanning imaging radiometer based on a time constraint considered near-ground PM2.5 concentration method, and it can be seen that the inversion result has higher consistency (correlation coefficient is up to 0.93) with a site monitoring value and a relatively small error (root mean square error is 10.01ug/m3, and more than 75% of the inversion result is within an error range of 10%).

On the basis of higher inversion accuracy, the algorithm also obtains better application effect in the monitoring of the pollution process. Fig. 4 (fig. 4a, b, c, d are a wind cloud four satellite multichannel scanning imaging radiometer observation cloud picture, a pollutant classification image, a near-ground PM2.5 concentration inversion result picture, a ground station monitoring near-ground PM2.5 concentration monitoring result in sequence) is a pollution process monitored by a wind cloud four satellite and a near-ground PM2.5 concentration result inverted by an algorithm, and it can be seen that the distribution and the change of the near-ground PM2.5 concentration in the pollution process are well reflected by the algorithm inversion result.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application and not for limiting the protection scope thereof, and although the present application is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: numerous variations, modifications, and equivalents will occur to those skilled in the art upon reading the present application and are within the scope of the claims appended hereto.