A prediction method for the intensity of artificial green space in alleviating urban heat island

Abstract

The method for predicting the intensity of artificial green space in alleviating urban heat islands disclosed in the present invention calculates the temperature (T gl ) i,j , according to (T gl ) i,j Calculate the air temperature T in all grid areas i,j , T i,j The pre-established urban canopy model is used as the boundary condition for simulation calculation to obtain the effect of different green space layout schemes on alleviating the intensity of urban heat island. It can effectively predict the effect of artificial green space on alleviating the intensity of urban heat island, so that the green space type and green space area can be reasonably arranged to improve or alleviate the urban heat island effect, which is of great significance for the study of alleviating the urban heat island effect.

Description

Technical Field

[0001] The invention relates to the field of computer technology, and in particular to a method for predicting the intensity of artificial green space in alleviating urban heat islands. Background Art

[0002] As cities continue to develop at a high speed, the urban heat island effect is becoming increasingly serious. Alleviating urban heat islands can help curb the spread of infectious diseases, reduce greenhouse gas emissions, and reduce building energy consumption. The planning and layout of urban artificial green spaces can effectively alleviate the urban heat island effect.

[0003] Green space has a significant mitigating effect on the urban heat island effect. Studies have shown that the local air temperature above green space is lower than the air temperature on the surrounding non-green space surface, and a green space area with a certain area is equivalent to a local cold source, and the surrounding area of ​​the green space will be affected and the temperature will drop. The impact of green space on the surrounding environmental temperature is strongly correlated with factors such as the scale and type of green space. Therefore, considering the limited land in the urban area, how to effectively predict the cooling effect of green space is of great significance for the reasonable arrangement of green space types and green space areas to improve or alleviate the urban heat island effect.

[0004] At present, the intensity of mitigating the urban heat island effect is mainly considered from the aspects of building planning and layout, building unit optimization design, site environment shading, urban landscape greening, etc. In recent years, many studies on the effect of green space on urban heat island effect have shown that green space has a significant impact on urban temperature. Many studies have explored the correlation between various factors of urban green space and urban surface temperature, and also proved the effect of reasonable layout of urban green space on mitigating the urban heat island effect. In many studies, effective measures to improve or alleviate the urban heat island effect under the limited conditions of urban land use are fully considered, but there is no model that can directly predict the intensity of different green space layouts on mitigating the urban heat island effect. In addition, there are many studies on the mitigation effect of a single green space on the urban heat island effect, but there is no relevant literature report on the mitigation effect of multiple green spaces in coordination with buildings, streets, etc. on the urban heat island. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, an embodiment of the present invention provides a method for predicting the intensity of artificial green space in alleviating urban heat island, the method comprising the following steps:

[0006] According to the formula Calculate the temperature of the air inside the artificial green space area in each grid (T gl ) i,j , where (T soil ) i,j is the air temperature of the ground surface in each grid area with the same area and shape and without green space coverage, A i,jis the area of ​​each artificial green space, Θ(SMI,T,RH) i,j is the correction factor for the cooling effect of artificial green space with solar radiation as SMI, air temperature on artificial green space as T and humidity as RH based on local common climate parameters, Θ(SMI,T,RH)=Θ(SMI)+Θ(T)+Θ(RH),Θ(SMI=b2(SMI) 2 +b1SMI+b0, Θ(T)=c1T+c0, Θ(RH)=d1RH+d0, is the cooling effect function produced by artificial green space coverage, a0, a1, b0, b1, b2, c0, c1 are regression coefficients, which are obtained by linear regression fitting based on the test results of local experiments. γ is the artificial green space cooling index, which is obtained by random assignment based on the normal distribution of artificial green space. is the proportion of artificial green space coverage in each grid;

[0007] According to the formula

[0008] Calculate the air temperature T in all grid areas respectively i,j , where c v is the specific heat of air, α f is the air convection heat transfer coefficient on the green space surface, Δx and Δy are the length and width of the grid respectively, ρ is the air density, u is the air flow velocity in the horizontal direction, and v is the air flow velocity in the vertical direction;

[0009] T i,j The pre-established urban canopy model was input as the boundary condition for simulation calculation, and the effects of different green space layout schemes on alleviating the intensity of urban heat island were obtained.

[0010] Preferably, before calculating the temperature of the air inside the artificial green space area in each grid according to the formula, the method further includes:

[0011] On a plan view corresponding to the urban area, the locations of artificial green spaces and streets are marked and the urban area is divided into a plurality of square grids;

[0012] According to the coordinate positions of the grids, the plurality of square grids are numbered according to a set rule;

[0013] According to the size of the area covered by the artificial green space of the plurality of square grids, the artificial green space coverage area ratio is set for the plurality of square grids respectively. Among them, i and j are the numbers of the grid.

[0014] Preferably, using the formula Calculate the horizontal air flow velocity u and the vertical air flow velocity v, where μ is the viscosity of the air and p is the air pressure.

[0015] Preferably, the method further comprises:

[0016] According to the formula Get the formula

[0017] Among them, c v is the specific heat capacity of air, T is the air temperature, A is the area of ​​artificial green space, ΔT is the temperature difference between the surface temperature of artificial green space and the air temperature, V cv is the volume of the control body.

[0018] The artificial green space provided in the embodiment of the present invention has the following beneficial effects on the prediction method of alleviating the intensity of urban heat island:

[0019] By comprehensively considering the influence of factors such as the area of ​​artificial green space, plant transpiration and solar radiation intensity, the problem of the impact of multiple green spaces on the air temperature of the entire region can be solved. It can effectively predict the effect of artificial green spaces on alleviating the intensity of urban heat islands, and make it possible to reasonably arrange green space types and areas to improve or alleviate the urban heat island effect, which is of great significance to the study of alleviating the urban heat island effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic flow chart of a method for predicting the intensity of urban heat islands to be alleviated by artificial green space provided in an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of a green space layout model provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, an embodiment of the present invention provides a method for predicting the intensity of artificial green space in alleviating urban heat island, the method comprising the following steps:

[0024] S101, according to the formula Calculate the temperature of the air inside the artificial green space area in each grid (T gl ) i,j , where (T soil ) i,j is the air temperature of the ground surface in each grid area with the same area and shape and without green space coverage, A i,j is the area of ​​each artificial green space, Θ(SMI,T,RH) i,jis the correction factor for the cooling effect of artificial green space with solar radiation as SMI, air temperature on artificial green space as T and humidity as RH based on local common climate parameters, Θ(SMI,T,RH)=Θ(SMI)+Θ(T)+Θ(RH),Θ(SMI=b2(SMI) 2 +b1SMI+b0, Θ(T)=c1T+c0, Θ(RH)=d1RH+d0, is the cooling effect function produced by artificial green space coverage, a0, a1, b0, b1, b2, c0, c1 are regression coefficients, which are obtained by linear regression fitting based on the test results of local experiments. γ is the artificial green space cooling index, which is obtained by random assignment based on the normal distribution of artificial green space. is the proportion of artificial green space coverage in each grid.

[0025] Among them, due to the influence of buildings, roads, etc., some artificial green spaces cannot cover all grids. In order to solve the problem that only part of the grid is covered by green space, a coefficient describing the proportion of green space in the grid is introduced.

[0026] The green space cooling index γ refers to the cooling effect of the green space on the air, in degrees Celsius, and is related to factors such as the type, density and growth status of the plants in the green space. The cooling index of the green space in the study area can be based on the usual green space cooling index distribution law under local climatic conditions. For such a large number of random events, it can be set to satisfy the law of large numbers and the central limit theorem. The law of large numbers shows that the number of green space grids with a certain green space cooling index is almost the same as the probability of its occurrence. The green space cooling index of each green space grid is obtained by randomly assigning values ​​according to its normal distribution. First, a common local green space plant is determined, and the green space cooling index of the green space under the usual planting density and growth state of the plant is used as the mathematical expectation of the normal distribution.

[0027] S102, according to the formula

[0028] Calculate the air temperature T in all grid areas respectively i,j , where c v is the specific heat of air, α f is the air convection heat transfer coefficient on the green space surface, Δx and Δy are the length and width of the grid respectively, ρ is the air density, u is the air flow velocity in the horizontal direction, and v is the air flow velocity in the vertical direction.

[0029] Once the internal temperature of a green space is determined, its impact on the surrounding air temperature can be considered. The cooling process of the surrounding air by green space is essentially a coupled propagation process of flow and heat, mainly considering the convection transfer process related to air flow. Studies have shown that the impact of green space vegetation on the surrounding ambient temperature is strongly correlated with the area, perimeter and shape of the green space.

[0030] The air temperature inside the green space is affected by the reflection, absorption and shielding of solar radiation by the plants on the plot, as well as the transpiration of the plants. Studies have shown that the temperature inside the green space is only related to the plant coverage (i.e., the plant coverage area and the green space cooling index). The temperature of the air around the artificial green space in the boundary area can also be directly obtained through manual measurement.

[0031] S103, T i,j The pre-established urban canopy model was input as the boundary condition for simulation calculation, and the effects of different green space layout schemes on alleviating the intensity of urban heat island were obtained.

[0032] Optionally, before calculating the temperature of the air inside the artificial green space area in each grid according to the formula, the method further includes:

[0033] like Figure 2 As shown, on a plan view corresponding to an urban area, the locations of artificial green spaces and streets are marked and the urban area is divided into a plurality of square grids;

[0034] According to the coordinate positions of the grids, the plurality of square grids are numbered according to a set rule;

[0035] According to the size of the area covered by the artificial green space of the plurality of square grids, the proportion of the artificial green space coverage is set for the plurality of square grids respectively. Among them, i and j are the numbers of the grid.

[0036] Alternatively, using the formula Calculate the horizontal air flow velocity u and the vertical air flow velocity v, where μ is the viscosity of the air and p is the air pressure.

[0037] As a specific embodiment, if the "east-west" direction is the column and the "north-south" direction is the row, the further east you go, the larger the column number will be; the further south you go, the larger the row number will be.

[0038] Among them, the air flow on each grid is first examined, and then the air velocity above the green space in the canopy above the green space is relatively consistent when it is fully mixed in the height direction (z axis). The difference in the air flow up and down is no longer considered. In this way, the air flow can be decomposed into two velocity fields: the x direction and the y direction. The x direction can be taken as the east and the y direction as the south. When the directions are opposite, the value is negative. The air flow process can be described on a two-dimensional plane by the law of conservation of mass and the law of conservation of momentum. Considering that the density and viscosity of the air in the canopy above the green space change very little, and the volume force is mainly gravity in the vertical direction (z direction), and the seasonal wind above the urban canopy is the main driving force of the air flow in the green space, it can be simplified as a steady-state flow process.

[0039] Optionally, the method further comprises:

[0040] According to the formula Get the formula

[0041] Among them, c v is the specific heat capacity of air, T is the air temperature, A is the area of ​​artificial green space, ΔT is the temperature difference between the surface temperature of artificial green space and the air temperature, V cv is the volume of the control body.

[0042] The widely used finite volume method (FVM) is used for numerical calculation. In a two-dimensional grid, the height is taken as the unit length, and the formula Numerical integration yields:

[0043]

[0044] Assume that the side length of a grid in the square grid is Δx, Δx, and Δx = Δy, the heat exchange area between the green surface and the air is A = ΔxΔy; the volume of the control volume is V ev =ΔxΔy·1.

[0045] Can be discretized as:

[0046] ρC v TΔuΔy+ρC v TΔvΔx-(α f ΔT a )ΔxΔy=0

[0047] For the grid numbered (i,j) in the middle position,

[0048] C V ΔyT i,j [(ρu) i,j+0.5 -(ρu) i,j-0.5]+C V ΔxT i,j [(ρv) i+0 .5, j -(ρv) i-0 .5, j ]-αΔxΔy(T i,j -(T gl ) i,j )=0, we can get,

[0049] The method for predicting the intensity of artificial green space in alleviating urban heat island provided by the embodiment of the present invention calculates the temperature (T gl ) i,j , according to (T gl ) i,j Calculate the air temperature T in all grid areas i,j , T i,j The pre-established urban canopy model is used as the boundary condition for simulation calculation to obtain the effect of different green space layout schemes on alleviating the intensity of urban heat island. It can effectively predict the effect of artificial green space on alleviating the intensity of urban heat island, so that the green space type and green space area can be reasonably arranged to improve or alleviate the urban heat island effect, which is of great significance for the study of alleviating the urban heat island effect.

[0050] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0051] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0052] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0053] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for predicting the intensity of artificial green space in alleviating urban heat island, characterized in that: include: On a plan view corresponding to the urban area, the locations of artificial green spaces and streets are marked and the urban area is divided into a plurality of square grids; According to the coordinate positions of the grids, the plurality of square grids are numbered according to a set rule; According to the size of the area covered by the artificial green space of the plurality of square grids, the proportion of the artificial green space coverage is set for the plurality of square grids respectively. Among them, i and j are the numbers of the grid; According to the formula Calculate the temperature of the air inside the artificial green space area in each grid (T gl ) i,j , where (T soil ) i,j is the air temperature of the ground surface in each grid area with the same area and shape and without green space coverage, A i,j is the area of ​​each artificial green space, Θ(SMI,T,RH) i,j is the correction factor for the cooling effect of artificial green space with solar radiation as SMI, air temperature on artificial green space as T and humidity as RH based on the common climate parameters of the urban area, Θ(SMI,T,RH)=Θ(SMI)+Θ(T)+Θ(RH), Θ(SMI=b2(SMI) 2 +b1SMI+b0, Θ(T)=c1T+c0, Θ(RH)=d1RH+d0, is the cooling effect function produced by artificial green space coverage, a0, a1, b0, b1, b2, c0, c1, d0, d1 are regression coefficients, which are obtained by linear regression fitting based on the test results of the urban area experiment. γ is the artificial green space cooling index. The green space cooling index γ refers to the cooling effect of green space on the air, in units of ℃, and is obtained by random assignment based on the normal distribution of artificial green space. is the proportion of artificial green space coverage in each grid; According to the formula Calculate the air temperature T in all grid areas respectively i,j , where c v is the specific heat of air, α f is the air convection heat transfer coefficient on the green space surface, Δx and Δy are the length and width of the grid respectively, ρ is the air density, u is the air flow velocity in the horizontal direction, and v is the air flow velocity in the vertical direction; Using the formula Calculate the air flow velocity u in the horizontal direction and the air flow velocity v in the vertical direction, where μ is the viscosity of the air and p is the air pressure; T i,j The pre-established urban canopy model was input as the boundary condition for simulation calculation, and the effects of different green space layout schemes on alleviating the intensity of urban heat island were obtained.

2. The method for predicting the intensity of artificial green space in alleviating urban heat island according to claim 1 is characterized in that: The method further comprises: According to the formula Get the formula Among them, c v is the specific heat capacity of air, T is the air temperature, A is the area of ​​artificial green space, ΔT is the temperature difference between the surface temperature of artificial green space and the air temperature, V cv is the volume of the control body.

3. A computer program product, characterized in that The computer program product comprises a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, and when the program instructions are executed by a computer, the computer is caused to perform the method according to any one of claims 1 to 2.

4. A non-transitory computer-readable storage medium, characterized in that: The non-transitory computer-readable storage medium stores computer instructions, which cause the computer to execute the method according to any one of claims 1 to 2.

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