Urban low-altitude wind field monitoring method and system

Abstract

The invention discloses an urban low-altitude wind field monitoring method and system, and relates to the field of urban environment forecasting, and the method comprises the steps: building a four-dimensional variation assimilation system based on a four-dimensional variation target extensive function formula by taking a wind field state variable of a target urban region as a state variable in the four-dimensional variation target extensive function formula; inputting the wind field observation data of each observation point in the target city area into a four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; taking the assimilated wind field data as initial meteorological field data, performing wind field simulation calculation by using a preset WRF-LES mode, and obtaining wind field forecast data in the target urban area; real-time monitoring data of each observation point in a target city area is assimilated into an initial and boundary meteorological condition input field of a preset WRF-LES mode through a four-dimensional variational assimilation system, so that wind field information in the target city area is reflected, and city low-altitude wind field forecast data can be acquired in near real time with high resolution.

Description

Technical Field

[0001] The invention relates to the technical field of urban environment forecasting, in particular to a method for monitoring a low-altitude urban wind field, and also to a system for monitoring a low-altitude urban wind field using the method. Background Art

[0002] Urban low-altitude meteorological conditions have a significant impact on aviation, urban planning, environmental monitoring and other fields. Existing monitoring methods, such as setting up observation stations and meteorological towers on the ground, have problems such as low spatial resolution and untimely data acquisition.

[0003] Among them, wind measuring lidar can provide high-precision wind speed and direction data at different vertical heights, but it is difficult to reflect the wind field information of the entire city when used alone, and the monitoring area is relatively small; the numerical weather forecast system coupled with the large eddy simulation mode can simulate the impact of complex urban terrain on the wind field, which is suitable for the refined simulation and forecast of urban near-ground wind fields, and can expand the coverage of monitoring and early warning, but it requires accurate input of initial meteorological fields and boundary conditions, parameterization scheme settings suitable for the regional environment, and post-processing and application of high-resolution model output data.

[0004] Therefore, there is an urgent need for a method or system that can reflect the wind field information of the entire urban area when used alone and can obtain the urban low-altitude wind field forecast in near real time and with high resolution. Summary of the invention

[0005] In order to reflect the wind field information of all areas of the city and obtain the city's low-altitude wind field forecast in near real time and with high resolution, the present invention provides a city's low-altitude wind field monitoring method and system.

[0006] The present invention is implemented by the following technical scheme: a method for monitoring a low-altitude wind field in an urban area, comprising the following steps: based on a four-dimensional variational objective functional formula, a four-dimensional variational assimilation system is established with the wind field state variables of a target urban area as the state variables in the four-dimensional variational objective functional formula; wind field observation data of each observation point in the target urban area is input into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; the assimilated wind field data is used as initial meteorological field data, a preset WRF-LES mode is used to perform wind field simulation calculations to obtain wind field forecast data in the target urban area.

[0007] As a further improvement of the above scheme, the four-dimensional variational objective functional formula is as follows: in, is the state variable in the four-dimensional variational assimilation system, For the background field, is the background error covariance; is the observed variable, i represents the moment, N is the assimilation time window, is the observation error covariance, represents the model simulation value, is the mode state vector, is the observation error covariance matrix.

[0008] As a further improvement of the above scheme, the wind field observation data of each observation point in the target city area is input into the four-dimensional variational assimilation system for initial field assimilation, which includes the following steps: based on the target city area, a regular quadrilateral containing the target city area is obtained; the four corners of the regular quadrilateral are set as observation points, and wind measuring lidars are respectively set at the observation points; and the wind field observation data of each of the observation points is obtained through the wind measuring lidar.

[0009] As a further improvement of the above scheme, the assimilated wind field data is used as the initial meteorological field data, and the preset WRF-LES model is used to perform wind field simulation calculations, which includes the following steps: setting a simulation parameterization scheme of the WRF-LES model based on the observed wind field sample set and the target urban area; determining the optimal simulation parameterization scheme based on the comparison results of the observed wind field sample set and the simulated wind field sample set; coupling the optimal simulation parameterization scheme with the urban boundary layer parameterization scheme to obtain a target parameterization scheme, and obtaining the preset WRF-LES model based on the target parameterization scheme.

[0010] As a further improvement of the above scheme, the urban boundary layer parameterization scheme is described by the momentum equation and the turbulent kinetic energy equation.

[0011] As a further improvement of the above scheme, the momentum equation is as follows: in, are the wind speed components in the horizontal and vertical directions, is the pressure gradient term, is the momentum diffusion coefficient, is the drag introduced by the urban canopy, is the friction coefficient, It is the building surface area per unit volume.

[0012] As a further improvement of the above scheme, the turbulent kinetic energy equation is as follows: in is the turbulent kinetic energy, is the turbulence dissipation term, is the turbulent kinetic energy production term, is the momentum flux, represents the vertical wind shear, Turbulence source terms introduced for buildings and street canyons, where is a constant related to the shape and layout of the building.

[0013] The present invention also provides a system for monitoring low-altitude wind farms in cities, which uses any of the above-mentioned methods for monitoring low-altitude wind farms in cities, and comprises: An assimilation system establishment module, which is used to establish a four-dimensional variational assimilation system based on a four-dimensional variational objective functional formula, taking the wind field state variables of the target urban area as the state variables in the four-dimensional variational objective functional formula; An assimilation module, which is used to input the wind field observation data of each observation point in the target urban area into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; The wind field simulation module is used to use the assimilated wind field data as initial meteorological field data, use a preset WRF-LES mode to perform wind field simulation calculations, and obtain wind field forecast data within the target urban area.

[0014] Compared with the existing urban low-altitude wind farm monitoring method, the urban low-altitude wind farm monitoring method and system of the present invention have the following beneficial effects: The server obtains a four-dimensional variational objective functional formula, takes the wind field state variables of the target city area as the state variables in the four-dimensional variational objective functional formula, and establishes a four-dimensional variational assimilation system; the wind field observation data of each observation point in the target city area are input into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; the assimilated wind field data are used as the initial meteorological field data, and the preset WRF-LES model is used to perform wind field simulation calculations to obtain the wind field forecast data in the target city area; the real-time monitoring data of each observation point in the target city area are assimilated into the initial and boundary meteorological condition input fields of the preset WRF-LES model through the four-dimensional variational assimilation system, which not only reflects the wind field information in the target city area but also can obtain the urban low-altitude wind field forecast data in near real time and with high resolution.

[0015] The beneficial effects of the urban low-altitude wind field monitoring system are the same as those of the above-mentioned urban low-altitude wind field monitoring method, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flowchart of a method for monitoring a low-altitude urban wind farm according to an embodiment of the present invention.

[0017] Figure 2 4 is a method flow chart of the assimilation step of an embodiment of the present invention.

[0018] Figure 3 The figure is a flow chart of a method for simulating a wind farm according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] See also Figure 1 In the embodiment of the present application, a method for monitoring a low-altitude wind field in an urban area is proposed, and the method comprises the following steps: S101, based on a four-dimensional variational objective functional formula, a four-dimensional variational assimilation system is established with the wind field state variables of the target urban area as the state variables in the four-dimensional variational objective functional formula; Specifically, the four-dimensional variational assimilation algorithm combines background information, observation information and dynamic model constraints through a four-dimensional variational objective function, and uses the calculation of the forward model and the adjoint model to iterate repeatedly to find the optimal initial conditions, thereby efficiently integrating observation data with different temporal and spatial distributions and improving the model prediction accuracy; the four-dimensional variational objective function formula is as follows: Among them, the first term is the background constraint term, which describes the deviation between the optimization result and the background field: is the initial state vector to be optimized, is the initial background state vector derived from previous model runs or climatological data, represents the background error covariance matrix, which is used to describe the uncertainty of the background field. The second term is the observation constraint term, which represents the model simulation value With observed value Deviation: For actual measurement data, Represents the observation operator, which is used to map variables in the model space to the observation space. is the mode state vector, is the observation error covariance matrix, which is used to describe the uncertainty of the observation data. The mode state in the objective function The constraints of the power mode need to be met: in From the initial moment arrive The mode evolution operator is used to simulate the change of mode state over time. The gradient of the objective function is the key to its minimization, and the gradient can be efficiently calculated by the adjoint method, and its expression is as follows: Among them, the first term is the background term gradient, which describes the optimization solution With background field The second term is the observation term gradient, which describes the gradient of the error between the model simulation and the observation: is the adjoint operator, is the transpose of the observation operator.

[0021] In an embodiment of the present application, the wind field state variables of the target urban area are used as the state variables that need to be optimized in the four-dimensional variational objective functional formula.

[0022] S102, inputting the wind field observation data of each observation point in the target city area into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; Since the locations of the observation points in the target city area are different, the wind field observation data obtained at each observation point are also different. In order to ensure the high consistency of the time and spatial data of different measurement equipment in the WRF initial conditions and boundary conditions, the wind field observation data of each observation point in the target city area are input into the four-dimensional variational assimilation system for initial field assimilation, which reduces the uncertainty of the wind field observation data and improves the quality of the wind field observation data.

[0023] S103: Using the assimilated wind field data as initial meteorological field data, using a preset WRF-LES model to perform wind field simulation calculations to obtain wind field forecast data in the target city area.

[0024] Among them, the preset WRF-LES model is obtained by setting a simulation parameterization scheme of the WRF-LES model based on the observed wind field sample set and the target urban area; determining the optimal simulation parameterization scheme according to the comparison results of the observed wind field sample set and the simulated wind field sample set; numerically coupling the optimal simulation parameterization scheme with the urban boundary layer parameterization scheme to obtain the target parameterization scheme, and obtaining the preset WRF-LES model based on the target parameterization scheme.

[0025] Specifically, the assimilated wind field data is used as the initial meteorological field data, and the initial conditions and boundary conditions of the preset WRF-LES model are set according to the initial meteorological field data, so as to perform wind field simulation calculations and obtain wind field forecast data in the target urban area.

[0026] In the present application, based on the four-dimensional variational objective functional formula, a four-dimensional variational assimilation system is established with the wind field state variables of the target city area as the state variables in the four-dimensional variational objective functional formula; the wind field observation data of each observation point in the target city area is input into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; the assimilated wind field data is used as the initial meteorological field data, and the preset WRF-LES mode is used to perform wind field simulation calculations to obtain the wind field forecast data in the target city area; the real-time monitoring data of each observation point in the target city area is assimilated into the initial and boundary meteorological condition input fields of the preset WRF-LES mode through the four-dimensional variational assimilation system, which not only reflects the wind field information in the target city area, but also can obtain the urban low-altitude wind field forecast data in near real time and with high resolution.

[0027] See also Figure 2 In one embodiment of the application, the following steps are included before step S102: S201, based on the target city area, obtaining a regular quadrilateral including the target city area; S202, setting the four corners of the regular quadrilateral as observation points, and respectively setting wind measurement laser radars at the observation points; In the target urban area that needs to be monitored, a regular quadrilateral containing the target urban area is determined, and a wind measuring lidar is deployed at each of the four corners of the regular quadrilateral to form a monitoring network; the placement distance of the lidar can be changed according to the specific regional environment to better capture the wind field characteristics of densely populated areas.

[0028] S203: Acquire wind field observation data of each observation point through the wind measuring laser radar.

[0029] In the embodiment of the present application, compared with the two-point deployment, it is difficult to capture the complex three-dimensional wind field structure and there is greater uncertainty; the hexagonal grid deployment helps to improve the spatial resolution and observation accuracy of the wind field, but may significantly increase the cost, data processing complexity and transmission pressure; the four-point deployment adopted in this application can better cover the target urban area, reduce data blind spots, and ensure uniform spatial distribution, which is conducive to interpolation or grid reconstruction, and provides more stable wind field data.

[0030] See also Figure 3 In one embodiment of the application, the following steps are included before step S103: S301, setting a simulation parameterization scheme of the WRF-LES model based on the observed wind field sample set and the target urban area; S302, determining an optimal simulation parameterization scheme according to a comparison result of the observed wind field sample set and the simulated wind field sample set; S303: coupling the optimal simulation parameterization scheme with the urban boundary layer parameterization scheme to obtain a target parameterization scheme, and acquiring a preset WRF-LES model based on the target parameterization scheme.

[0031] Among them, the parameterization scheme of the urban boundary layer is described by the momentum equation and the turbulent kinetic energy equation; In the embodiment of the present application, the obstruction of the urban canopy will add an additional force term to the momentum equation. The influence of the urban canopy on the wind field in the momentum equation is represented by an explicit drag force. The expression of the momentum equation is as follows: in are the wind speed components in the horizontal and vertical directions, is the pressure gradient term, is the momentum diffusion coefficient, is the drag force introduced by the urban canopy (buildings, street canyons, etc.), expressed as: in is the friction coefficient, It is the building surface area per unit volume.

[0032] In the turbulent kinetic energy equation, the turbulent structure introduced by the urban boundary layer can be described by the turbulent kinetic energy equation, and the influence of buildings is added to the turbulence production term; the expression of the turbulent kinetic energy equation is as follows: in is the turbulent kinetic energy, is the turbulence dissipation term, is the turbulent kinetic energy production term, and its specific expression is: in is the momentum flux, usually calculated by the turbulence closure scheme, Represents vertical wind shear.

[0033] and Turbulence source terms introduced for buildings and street canyons, where are constants related to the shape and layout of the building: The roughness effect introduced by buildings affects the calculation of wind speed profiles, and the roughness correction of the urban canopy is added to the expression of the logarithmic wind profile, and the formula is as follows: in is the friction speed, is the von Karman constant, is the roughness length, which is determined by the building height And density determines: ,in, is a constant, It is the zero plane displacement height, usually 2 / 3 of the building height.

[0034] In the embodiments of the present application, the newly released urban boundary layer parameterization scheme in the WRF model is coupled on the basis of the LES parameter scheme to accurately simulate the influence of complex urban underlying surfaces, such as high-rise buildings, street canyons, green spaces, etc. on the turbulent structure of the wind field, and enhance the ability to capture local vortices and airflow disturbances. In addition, a high-performance computing platform and a distributed parallel architecture are used to construct a real-time wind field data feedback mechanism to realize the rapid update of WRF-LES periodic simulation and lidar observation data, thereby improving the response speed of near real-time prediction.

[0035] In one embodiment of the application, a system for monitoring low-altitude wind fields in an urban area is provided, the system comprising: An assimilation system establishment module, which is used to establish a four-dimensional variational assimilation system based on a four-dimensional variational objective functional formula, taking the wind field state variables of the target urban area as the state variables in the four-dimensional variational objective functional formula; An assimilation module, which is used to input the wind field observation data of each observation point in the target urban area into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; The wind field simulation module is used to use the assimilated wind field data as initial meteorological field data, use a preset WRF-LES mode to perform wind field simulation calculations, and obtain wind field forecast data within the target urban area.

[0036] Compared with the prior art, the advantages of the urban low-altitude wind field monitoring device are the same as those of the urban low-altitude wind field monitoring method, which will not be elaborated here.

[0037] In one embodiment of the application, a computer terminal is provided, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. The steps of the urban low-altitude wind farm monitoring method are implemented when the processor executes the program. When the method is applied, it can be applied in the form of software, such as being designed as an independently running program and installed on a computer terminal, which can be a computer, a smart phone, a control system, and other Internet of Things devices. The method can also be designed as an embedded running program and installed on a computer terminal, such as a single-chip microcomputer.

[0038] In one application embodiment, this embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of the urban low-altitude wind farm monitoring method are implemented. When the method is applied, it can be applied in the form of software, such as a program designed to be independently run by a computer-readable storage medium. The computer-readable storage medium can be a USB flash drive, designed as a USB shield, and the USB flash drive is designed to start the program of the entire method through an external trigger.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for monitoring low-altitude wind fields in cities, characterized in that: The method comprises the following steps: Based on the four-dimensional variational objective functional formula, a four-dimensional variational assimilation system is established with the wind field state variables of the target urban area as the state variables in the four-dimensional variational objective functional formula; Inputting the wind field observation data of each observation point in the target city area into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; The assimilated wind field data is used as the initial meteorological field data, and the preset WRF-LES mode is used to perform wind field simulation calculation to obtain the wind field forecast data in the target urban area.

2. The urban low-altitude wind field monitoring method according to claim 1, characterized in that: The four-dimensional variational objective functional formula is as follows: in, is the state variable in the four-dimensional variational assimilation system, For the background field, is the background error covariance; is the observed variable, i represents the moment, N is the assimilation time window, is the observation error covariance, represents the model simulation value, is the mode state vector, is the observation error covariance matrix.

3. The urban low-altitude wind field monitoring method according to claim 1, characterized in that: The step of inputting the wind field observation data of each observation point in the target city area into the four-dimensional variational assimilation system for initial field assimilation includes the following steps: Based on the target urban area, obtaining a regular quadrilateral including the target urban area; The four corners of the regular quadrilateral are set as observation points, and wind measurement laser radars are respectively set at the observation points; The wind field observation data of each observation point is obtained by using the wind measuring laser radar.

4. The urban low-altitude wind field monitoring method according to claim 1, characterized in that: The assimilated wind field data is used as the initial meteorological field data, and the wind field simulation calculation is performed using the preset WRF-LES mode, which includes the following steps: Based on the observed wind field sample set and the target urban area, setting a simulation parameterization scheme of the WRF-LES model; Determining an optimal simulation parameterization scheme according to a comparison result between the observed wind field sample set and the simulated wind field sample set; The optimal simulation parameterization scheme is coupled with the urban boundary layer parameterization scheme to obtain a target parameterization scheme, and a preset WRF-LES model is obtained based on the target parameterization scheme.

5. The urban low-altitude wind field monitoring method according to claim 4, characterized in that: The urban boundary layer parameterization scheme is described by the momentum equation and the turbulent kinetic energy equation.

6. The urban low-altitude wind field monitoring method according to claim 5, characterized in that: The momentum equation is as follows: in, are the wind speed components in the horizontal and vertical directions, is the pressure gradient term, is the momentum diffusion coefficient, is the drag introduced by the urban canopy, is the friction coefficient, It is the building surface area per unit volume.

7. The urban low-altitude wind field monitoring method according to claim 5, characterized in that: The turbulent kinetic energy equation is as follows: in is the turbulent kinetic energy, is the turbulence dissipation term, is the turbulent kinetic energy production term, is the momentum flux, represents the vertical wind shear, Turbulence source terms introduced for buildings and street canyons, where is a constant related to the shape and layout of the building.

8. An urban low-altitude wind field monitoring system, characterized in that: The system comprises: An assimilation system establishment module, which is used to establish a four-dimensional variational assimilation system based on a four-dimensional variational objective functional formula, taking the wind field state variables of the target urban area as the state variables in the four-dimensional variational objective functional formula; An assimilation module, which is used to input the wind field observation data of each observation point in the target urban area into the four-dimensional variational assimilation system for initial field assimilation to obtain assimilated wind field data; The wind field simulation module is used to use the assimilated wind field data as initial meteorological field data, use a preset WRF-LES mode to perform wind field simulation calculations, and obtain wind field forecast data within the target urban area.

9. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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