Concentration weight trajectory calculation method integrated with air mass height and boundary layer height data

Abstract

The invention discloses a concentration weight trajectory calculation method integrated with air mass height and boundary layer height data, and belongs to the technical field of meteorological models. According to the method, the CWT contribution values of different height layers are multiplied by the corresponding weight factors respectively and then are corrected, the HCWT value considering the height influence is finally obtained, the comprehensive influence of the air mass on the pollutant concentration of the target area at different heights can be reflected more accurately, then the HCWT value is corrected, the corrected WHCWT value is obtained, and the target pollutant concentration of the target area is calculated. And the actual conditions that the influence of low-altitude pollution air mass on the near ground is relatively serious and the influence of high-altitude pollution air mass on the near ground is relatively light are fully considered.

Description

Technical Field

[0001] The present invention relates to the technical field of meteorological models, and in particular to a concentration weight trajectory calculation method that incorporates air mass height and boundary layer height data. Background Art

[0002] Concentration Weighted Trajectory (CWT) is a professional method for tracing the source of atmospheric pollutants. This method relies on the atmospheric trajectory data calculated by the HYSPLIT trajectory model, and on this basis, integrates the pollutant concentration information of the area through which the trajectory passes to achieve a deep insight into the pollution source. As the cornerstone of atmospheric trajectory calculation, the importance of the HYSPLIT trajectory model is self-evident.

[0003] At present, in the calculation practice of concentration weighted trajectory (CWT) in a certain area, people often only focus on the latitude and longitude grid where the air mass particle is located and the pollution level when the trajectory reaches the target point, but ignore the height factor of the air mass during its movement. Specifically, the actual situation that the pollution of near-ground air masses has a greater impact while the pollution of high-altitude air masses has a lighter impact is not fully considered. To this end, the present invention proposes a concentration weighted trajectory calculation method that incorporates air mass height and boundary layer height data. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to combine air mass flight altitude parameters with boundary layer altitude parameters to determine concentration weight trajectory, and provides a concentration weight trajectory calculation method that incorporates air mass altitude and boundary layer altitude data.

[0005] The present invention solves the above technical problems through the following technical solutions, and the present invention comprises the following steps:

[0006] Step S100: using the HYSPLIT trajectory model to calculate and obtain the backward moving trajectory data of the air mass in the target area;

[0007] Step S200: obtaining the latitude and longitude, height, and boundary layer height PBLH of the air mass at different times;

[0008] Step S300: Divide the target area into multiple grid areas, where the grid has i rows and j columns, determine the number of nodes of the backward moving trajectory in the grid area and the pollutant concentration when the trajectory passes through the grid area, and calculate the CWT contribution value of each grid area;

[0009] Step S400: The CWT contribution values ​​in different grid areas are integrated into the air mass height height and the boundary layer height PBLH for weighted correction to obtain the concentration weight trajectory HCWT value integrated into the air mass height and the boundary layer height, and a weight function is introduced to correct the HCWT value to obtain the corrected concentration weight trajectory WHCWT value integrated into the air mass height and the boundary layer height.

[0010] Furthermore, in step S100, the trajectory data includes latitude, longitude and altitude information at each time step.

[0011] Furthermore, in step S100, the specific calculation process of the trajectory data is as follows:

[0012] Step S110: inputting the meteorological data and pollutant concentration of the target area into the HYSPLIT trajectory model;

[0013] Step S120: Calculate the backward movement trajectory as needed;

[0014] Step S130: Record the latitude, longitude and altitude information of each track at different time steps.

[0015] Furthermore, in step S200, the specific process is as follows:

[0016] Step S210: obtaining the height of the air mass at different times according to the height of the grid area passed by the backward moving trajectory;

[0017] Step S220: The boundary layer height is obtained based on the simulation of the atmospheric environment by the HYSPLIT trajectory model and the comprehensive analysis of relevant meteorological parameters, thereby determining the boundary layer height PBLH corresponding to different times.

[0018] Furthermore, in step S300, the calculation formula of the CWT contribution value is as follows:

[0019]

[0020] Among them, C ij is the contribution concentration of the grid area in row i and column j, i.e., the CWT contribution value; C l is the pollutant concentration when the backward moving trajectory passes through the grid area, that is, the pollutant concentration of a single node on the backward moving trajectory; τ ijl It is the length of time that the backward moving trajectory stays in the grid area of ​​the i-th row and j-th column. The length of time is represented by the number of nodes of the backward moving trajectory in the grid area of ​​the i-th row and j-th column. The more the number of nodes, the longer the length of time that the backward moving trajectory stays in the grid area.

[0021] Furthermore, in step S400, the calculation expression of the concentration weight trajectory HCWT value incorporating the air mass height and the boundary layer height is as follows:

[0022]

[0023] Among them, C ijis the contribution concentration of the grid area in row i and column j; height ij is the air mass height in the grid area of ​​row i and column j; PBLH ij is the boundary layer height of the grid area in the i-th row and j-th column.

[0024] Furthermore, in step S400, the weight function W(n ij )The formula is as follows:

[0025]

[0026] Among them, n ave is the average number of nodes per grid area within the target area; n ij is the number of nodes in the grid area of ​​row i and column j that the backward moving trajectory passes through.

[0027] Furthermore, in the step S400, the expression of the concentration weight trajectory WHCWT value obtained after correction and integrated with the air mass height and the boundary layer height is as follows:

[0028] WHCWT=HCWT ij *W(n ij ).

[0029] Compared with the prior art, the present invention has the following advantages: the concentration weight trajectory calculation method that incorporates air mass height and boundary layer height data multiplies the CWT contribution values ​​of different altitude layers by corresponding weight factors and then corrects them, and finally obtains the HCWT value that takes the altitude influence into consideration, which can more accurately reflect the comprehensive influence of air masses on the pollutant concentration in the target area at different altitudes, and then corrects the HCWT value to obtain the corrected WHCWT value, which fully considers the actual situation that low-altitude polluted air masses have a more serious impact on the near-ground while high-altitude polluted air masses have a relatively lighter impact on the near-ground. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a concentration weight trajectory calculation method incorporating air mass height and boundary layer height data in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0032] like Figure 1 As shown, this embodiment provides a technical solution: a concentration weight trajectory calculation method integrating air mass height and boundary layer height data, comprising the following steps:

[0033] Step S100: Use the HYSPLIT trajectory model to calculate and obtain a large number of backward moving trajectories of the air mass; the trajectory data includes the latitude, longitude and altitude information of the trajectory at each time step. The details are as follows:

[0034] The prepared meteorological data is input into the HYSPLIT trajectory model to obtain a large number of backward trajectories of air masses passing through the grid area to reach the receptor point (such as an air quality monitoring station); during the trajectory calculation process, the position (latitude, longitude and altitude) information of each trajectory at different time steps is recorded; at the same time, the influence of terrain on the trajectory should be considered, especially in areas with complex terrain, to ensure the accuracy of trajectory calculation.

[0035] Among them, meteorological data are collected with high temporal and spatial resolution, such as wind speed, wind direction, temperature, air pressure, humidity, etc. These data come from the Global Data Assimilation System (GDAS) reanalysis data.

[0036] Step S200, obtaining the latitude and longitude, altitude height, and boundary layer height PBLH of the air mass at different times;

[0037] In this step, the specific process is as follows:

[0038] Step S210: Obtain the height of the air mass at each moment according to the height of the grid area passed by the backward moving trajectory.

[0039] Step S220, the acquisition of the boundary layer height is also based on the simulation of the atmospheric environment by the HYSPLIT trajectory model and the comprehensive analysis of relevant meteorological parameters, so as to determine the boundary layer height PBLH corresponding to different times.

[0040] Step S300: Determine the number of nodes of the backward moving trajectory in the grid area and the pollutant concentration when the trajectory passes through the grid area, and obtain the contribution concentration of the grid.

[0041] When determining the number of nodes of the backward moving trajectory in the grid area and the pollutant concentration when the backward moving trajectory passes through the grid area, it is first necessary to import the hourly pollutant concentration (such as the six-parameter data of the air quality monitoring station), and then distribute the hourly pollutant concentration to each backward moving trajectory, so as to obtain the pollutant concentration when each backward moving trajectory passes through the grid area, and calculate the grid contribution concentration of the grid area. The calculation formula is as follows:

[0042]

[0043] Among them, C ij is the contribution concentration of the grid area in row i and column j, i.e., the CWT contribution value; Cl is the pollutant concentration when the backward moving trajectory passes through the grid area, that is, the pollutant concentration of a single node on the backward moving trajectory; τ ijl It is the length of time that the backward moving trajectory stays in the grid area of ​​the i-th row and j-th column. The length of time is represented by the number of nodes of the backward moving trajectory in the grid area of ​​the i-th row and j-th column. The more the number of nodes, the longer the length of time that the backward moving trajectory stays in the grid area.

[0044] Step S400: weighted correction is performed on the CWT contribution values ​​in different grid areas by integrating the air mass height and the boundary layer height PBLH, and the concentration weight trajectory HCWT integrated with the air mass height and the boundary layer height is obtained as follows:

[0045]

[0046] Among them, C ij is the contribution concentration of the grid area in row i and column j; height ij is the air mass height in the grid area of ​​row i and column j; PBLH ij is the boundary layer height of the grid area in the i-th row and j-th column.

[0047] In this embodiment, the CWT contribution values ​​of different altitude layers are multiplied by the corresponding weight factors and then summed up to finally obtain the HCWT value considering the height effect, which can more accurately reflect the comprehensive impact of air masses at different altitudes on the pollutant concentration in the target area.

[0048] Furthermore, in order to reduce the number of trajectories n on the grid ij For smaller uncertainties, a weight function W(n ij ), the concentration weight trajectory HCWT integrated into the air mass height and boundary layer height is corrected, and the weight function W(n ij )The formula is as follows:

[0049]

[0050] Among them, n ave is the average number of nodes per grid area within the target area; n ij is the number of nodes in the grid area of ​​row i and column j that the backward moving trajectory passes through.

[0051] The expression of the corrected concentration weight trajectory WHCWT that incorporates the air mass height and boundary layer height is as follows:

[0052] WHCWT=HCWT ij *W(n ij ).

[0053] In this embodiment, step 300 is specifically as follows:

[0054] Step S310: reasonably divide the target area into grids according to the terrain characteristics and pollutant diffusion characteristics of the target area;

[0055] Terrain considerations:

[0056] (1) Mountains and valleys: If there are mountains in the target area, the airflow near the mountains may be blocked and lifted by the terrain, affecting the diffusion path and concentration distribution of pollutants. Therefore, when dividing the grid, it is necessary to set a finer grid in the mountain area to better capture the changes in airflow and pollutants. For example, on the windward and leeward slopes of the mountains, due to the different rising and sinking movements of the airflow, the diffusion of pollutants is also very different. Therefore, according to the direction and slope of the mountains, smaller grid units can be set along the direction of the mountains, and the grid width can be adjusted as needed in the vertical direction of the mountains to accurately reflect the impact of the terrain on the diffusion of pollutants.

[0057] (2) Plains and plateaus: Plains are relatively flat, airflow is relatively smooth, and pollutant diffusion is relatively uniform. In this case, the grid division can be relatively regular and uniform, but it is also necessary to consider the local terrain changes that may exist on the plains, such as the impact of rivers and lakes on airflow and pollutant diffusion. For plateaus, due to their high altitude, the atmospheric environment is different from that of plains. It is necessary to consider the impact of airflow changes at the edge of the plateau and the topographic undulations within the plateau on pollutant diffusion, and reasonably adjust the size and shape of the grid.

[0058] (3) Water and land boundary: If the target area contains a large area of ​​water (such as lakes, oceans, etc.), the temperature difference at the boundary between water and land will lead to the generation of thermal circulation, thereby affecting the diffusion of pollutants. In areas close to water, the grid division should be more refined to capture the changes in airflow and pollutants at the boundary between water and land. At the same time, considering the adsorption and dilution effect of water on pollutants, different grid parameters need to be set for water and land respectively to accurately reflect the diffusion characteristics of pollutants at the boundary between water and land.

[0059] Pollutant dispersion characteristics considerations:

[0060] (1) Distribution of pollution sources: It is very important to understand the location and distribution of pollution sources in the target area. If the pollution sources are concentrated in a certain area, such as an industrial cluster or a busy traffic area in the city center, then a finer grid needs to be set up near these pollution sources to better track the process of pollutants spreading outward from the pollution sources. For dispersed pollution sources, such as small-scale farms or farmers' stove emissions in rural areas, although the emissions from a single pollution source may be small, the overall number is large, and it is also necessary to reasonably divide the grid according to its distribution to ensure that the diffusion path and concentration distribution of pollutants can be accurately calculated.

[0061] (2) Pollutant type: Different types of pollutants have different physical and chemical properties, and their diffusion characteristics are also different. For example, gaseous pollutants (such as sulfur dioxide, nitrogen oxides, etc.) are generally easier to diffuse than particulate pollutants (such as smoke, dust, etc.). For gaseous pollutants, a relatively large grid range can be appropriately considered when dividing the grid, but it should also be noted that some gaseous pollutants may react chemically with other substances, thereby changing their diffusion characteristics, which need to be adjusted according to specific circumstances. For particulate pollutants, since their diffusion is relatively difficult and may be affected by multiple factors such as gravity sedimentation and air flow, more precise grid division is required to accurately capture their diffusion path and concentration distribution.

[0062] Step S320: Calculate the contribution of the air mass to the pollutant concentration in the grid area during its trajectory based on the characteristics of each grid area and the position and height factors of the air mass trajectory when it passes through the area; and calculate the contribution of different air mass trajectory segments to the pollutant concentration in the grid area.

[0063] Consider the position of the air mass trajectory

[0064] (1) Horizontal position: When the air mass trajectory passes through the grid area, its horizontal position determines the approximate distribution range of pollutants in the area. If the air mass trajectory enters the grid area from one side and passes through the other side, then the pollutants may have a certain distribution in this horizontal direction. By calculating the residence time of the air mass at different horizontal positions in the grid area, a preliminary estimate of the horizontal distribution of pollutants in the area can be made. For example, if the air mass stays in the center of the grid area for a long time, then the pollutant concentration in the center of the area may be relatively high.

[0065] (2) Vertical position (height): The vertical position of an air mass has a more complex effect on pollutant concentrations. Air masses at different heights may contain different pollutant concentrations, and height will affect the way pollutants diffuse. For example, air masses near the ground may have a relatively slow diffusion of pollutants due to ground friction and thermal effects, and the concentration may be higher; whereas air masses at high altitudes may have a relatively fast diffusion of pollutants due to relatively smooth airflow, and the concentration may be lower. Therefore, when calculating the contribution of an air mass to the pollutant concentration in a grid area, it is necessary to consider the vertical position of the air mass and make calculations based on the influence of its height on the pollutant concentration.

[0066] Combined with the characteristics of the target area

[0067] (1) The impact of terrain on pollutant concentration: As mentioned above, the terrain of the target area will affect the diffusion and concentration distribution of pollutants. When the air mass trajectory passes through the grid area, if the area is located on the windward slope of the mountain, the air mass may be lifted, causing the pollutant concentration to change in the area. If it is located on the leeward slope, the air mass may sink, which will also affect the pollutant concentration. In plain areas, the terrain is relatively flat, but if there are water bodies such as rivers and lakes, the air mass may be affected by the temperature of the water body when passing through, thereby changing the pollutant concentration.

[0068] (2) Impact of pollution sources on pollutant concentration: The distribution of pollution sources in the target area will directly affect the pollutant concentration. If there is a pollution source in the grid area, the air mass trajectory will carry the pollutants emitted by the pollution source when passing through the area, thereby increasing the pollutant concentration in the area. If there is no pollution source, the air mass may only carry pollutants transmitted from other areas, and the concentration may be relatively low.

[0069] Calculate the contribution of different air mass trajectory segments separately

[0070] (1) Impact of different paths: Air masses may pass through the grid area from different directions and paths, and different trajectory segments contribute different values ​​to the pollutant concentration in the grid area. For example, one air mass trajectory enters the grid area from the north and the other enters from the south. Due to the possible presence of pollution sources or different meteorological conditions in the north, the contribution of the two trajectories to the pollutant concentration in the grid area may be very different. Therefore, it is necessary to calculate the contribution of each trajectory segment to the pollutant concentration in the grid area separately.

[0071] (2) The influence of different altitude layers (boundary layer altitude): When the same air mass trajectory passes through the grid area at different altitude layers, the contribution value to the pollutant concentration is also different. As mentioned above, air masses at different altitudes have different influences on the pollutant concentration. For example, if an air mass trajectory passes through the grid area at the near-ground layer and the high-altitude layer respectively, the air mass at the near-ground layer may increase the pollutant concentration in the grid area more, so it is necessary to calculate the contribution value of the trajectory at different altitude layers to the pollutant concentration in the grid area.

[0072] In summary, the concentration weight trajectory calculation method that incorporates the air mass height and boundary layer height data in the above-mentioned embodiment multiplies the CWT contribution values ​​of different altitude layers by the corresponding weight factors and then corrects them, and finally obtains the HCWT value that takes into account the height effect, which can more accurately reflect the comprehensive impact of the air mass on the pollutant concentration in the target area at different altitudes. The HCWT value is then corrected to obtain the corrected WHCWT value, which fully considers the actual situation that low-altitude polluted air masses have a more serious impact on the near-ground and high-altitude polluted air masses have a relatively lighter impact on the near-ground.

[0073] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A concentration weighted trajectory calculation method incorporating air mass height and boundary layer height data, characterized in that: The following steps are involved: Step S100: using the HYSPLIT trajectory model to calculate and obtain the backward moving trajectory data of the air mass in the target area; Step S200: obtaining the latitude and longitude, height, and boundary layer height PBLH of the air mass at different times; Step S300: Divide the target area into multiple grid areas, where the grid has i rows and j columns, determine the number of nodes of the backward moving trajectory in the grid area and the pollutant concentration when the trajectory passes through the grid area, and calculate the CWT contribution value of each grid area; Step S400: The CWT contribution values ​​in different grid areas are integrated into the air mass height height and the boundary layer height PBLH for weighted correction to obtain the concentration weight trajectory HCWT value integrated into the air mass height and the boundary layer height, and a weight function is introduced to correct the HCWT value to obtain the corrected concentration weight trajectory WHCWT value integrated into the air mass height and the boundary layer height.

2. The method for calculating concentration weighted trajectories incorporating air mass height and boundary layer height data according to claim 1, characterized in that: In step S100, the trajectory data includes latitude, longitude and altitude information at each time step.

3. The concentration weight trajectory calculation method incorporating air mass height and boundary layer height data according to claim 2 is characterized in that: In step S100, the specific calculation process of the trajectory data is as follows: Step S110: inputting the meteorological data and pollutant concentration of the target area into the HYSPLIT trajectory model; Step S120: Calculate the backward movement trajectory as needed; Step S130: Record the latitude, longitude and altitude information of each track at different time steps.

4. The method for calculating concentration weighted trajectories incorporating air mass height and boundary layer height data according to claim 3, characterized in that: In step S200, the specific process is as follows: Step S210: obtaining the height of the air mass at different times according to the height of the grid area passed by the backward moving trajectory; Step S220: The boundary layer height is obtained based on the simulation of the atmospheric environment by the HYSPLIT trajectory model and the comprehensive analysis of relevant meteorological parameters, thereby determining the boundary layer height PBLH corresponding to different times.

5. The method for calculating concentration weighted trajectories incorporating air mass height and boundary layer height data according to claim 4, characterized in that: In step S300, the calculation formula of the CWT contribution value is as follows: Among them, C ij is the contribution concentration of the grid area in row i and column j, i.e., the CWT contribution value; C l is the pollutant concentration when the backward moving trajectory passes through the grid area, that is, the pollutant concentration of a single node on the backward moving trajectory; τ ijl It is the length of time that the backward moving trajectory stays in the grid area of ​​the i-th row and j-th column. The length of time is represented by the number of nodes of the backward moving trajectory in the grid area of ​​the i-th row and j-th column. The more the number of nodes, the longer the length of time that the backward moving trajectory stays in the grid area.

6. The method for calculating concentration weighted trajectories incorporating air mass height and boundary layer height data according to claim 5, characterized in that: In step S400, the calculation expression of the concentration weight trajectory HCWT value incorporating the air mass height and the boundary layer height is as follows: Among them, C ij is the contribution concentration of the grid area in row i and column j; height ij is the air mass height in the grid area of ​​row i and column j; PBLH ij is the boundary layer height of the grid area in the i-th row and j-th column.

7. The method for calculating concentration weighted trajectories incorporating air mass height and boundary layer height data according to claim 6, characterized in that: In step S400, the weight function W(n ij )The formula is as follows: Among them, n ave is the average number of nodes per grid area within the target area; n ij is the number of nodes in the grid area of ​​row i and column j that the backward moving trajectory passes through.

8. The method for calculating concentration weight trajectory incorporating air mass height and boundary layer height data according to claim 7, characterized in that: In step S400, the expression of the concentration weight trajectory WHCWT value obtained after correction and integrated with the air mass height and boundary layer height is as follows: WHCWT=HCWT ij *W(n ij )。

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