A method for quantitatively evaluating urban vegetation evapotranspiration and shading cooling effect

Abstract

This invention belongs to the field of urban microclimate regulation technology, specifically a quantitative assessment method for the effects of urban vegetation evapotranspiration and shading cooling. This invention presents the concepts of vegetation evapotranspiration cooling effect and vegetation shading cooling effect, with parameters obtained from SCOPE simulations. The method includes: collecting basic data required for urban climate simulation, including characteristic data of vegetation, meteorology, and soil; applying the time-series simulation mode of the SCOPE model to simulate the dynamic changes in urban vegetation-atmosphere-soil energy, and correcting the model output, especially latent heat flux, based on the urban impervious surface cover; calculating ECoV and SCoV based on the correction results; and using GIS technology to spatially interpolate ECoV and SCoV to obtain a high-resolution spatiotemporal distribution map of urban vegetation evapotranspiration and shading cooling effects. This invention helps guide urban greening and planning, providing decision support for urban planners and policymakers to optimize urban vegetation layout, mitigate the urban heat island effect, and improve the quality of life for residents.

Description

Technical Field

[0001] This invention belongs to the field of urban microclimate regulation technology, specifically involving a quantitative evaluation method for the effects of urban vegetation evapotranspiration and shading cooling. Background Technology

[0002] With the acceleration of global climate change and urbanization, the urban heat island effect has become increasingly prominent, causing temperatures in urban centers to be significantly higher than in surrounding areas. The urban heat island effect poses serious challenges to urban ecosystems and human health; therefore, finding effective mitigation strategies is of paramount importance.

[0003] Urban vegetation is widely recognized as an effective strategy for mitigating the urban heat island effect. Its main mechanisms include two aspects: transpiration and shading. Transpiration primarily involves vegetation absorbing water from the soil and releasing it into the atmosphere as water vapor, thus effectively lowering the ambient temperature. Shading, on the other hand, reduces ground temperature by blocking solar radiation, especially during the hottest daytime hours. However, the cooling capacity of urban vegetation under extreme high-temperature conditions remains somewhat controversial. Some studies suggest that urban vegetation has an enhanced cooling effect at high temperatures, while others hold the opposite view.

[0004] To accurately assess the cooling effect of urban vegetation, researchers primarily employed two methods: field measurements and numerical simulation. Field measurements directly measure surface temperature and other relevant parameters, providing researchers with valuable in-situ data; numerical simulation allows for studies on a larger spatial scale, offering excellent spatial accuracy and flexibility. However, both methods have limitations. For example, field measurements are costly and cannot be widely applied; numerical simulation faces challenges such as the inherent heterogeneity of the urban environment and the complexity of the models.

[0005] Furthermore, most current research tends to study shading and evapotranspiration independently, while understanding of their interrelationships and interactions remains limited. To address these limitations, this invention proposes a quantitative method for urban vegetation cooling based on the Soil-Canopy-Observation of Photosynthesis and Energy (SCOPE) model. This method builds upon previous research but introduces more precise input data and refined quantitative indicators to accurately quantify urban vegetation evapotranspiration and shading cooling under various meteorological backgrounds. This method aims to explore the potential of urban vegetation evapotranspiration-shading cooling, filling a key gap in current research. This invention provides strong scientific support for the development of strategies for urban cooling and climate resilience. Summary of the Invention

[0006] The purpose of this invention is to provide a rapid and highly accurate quantitative evaluation method for urban vegetation evapotranspiration and shading cooling effects.

[0007] The quantitative evaluation method for urban vegetation evapotranspiration and shading cooling effect provided by this invention includes the following steps:

[0008] (1) For the research objectives and regions, basic data, including meteorological, vegetation and soil characteristic data, are collected according to the requirements of the SCOPE model.

[0009] (2) Apply the SCOPE model (soil-canopy-photosynthesis energy flux model) for time series simulation to generate simulated data of energy flux in the urban environment;

[0010] (3) For the unique microclimate conditions of the city (impervious surface cover), the permeable surface ratio index is used to correct the latent heat flux (LE) output of the SCOPE model;

[0011] (4) Define Evapotranspiration-induced Cooling of Vegetation (ECoV) to quantify the cooling effect of vegetation evapotranspiration;

[0012] (5) Define Shading-induced Cooling of Vegetation (SCoV) to quantify the cooling effect of vegetation shading;

[0013] (6) Based on GIS (Geographic Information System), spatial interpolation is performed on ECoV and SCoV to generate a high-resolution (hourly, 10-meter) spatial distribution map of vegetation cooling effect.

[0014] Furthermore:

[0015] In step (1), the vegetation feature data includes leaf area index, canopy water content, chlorophyll content, and tree height; the meteorological feature data includes air temperature, air pressure, relative humidity, and wind speed; the soil feature data includes soil relative humidity; and the data are processed to a uniform spatiotemporal precision to provide the necessary input parameters for model calculation.

[0016] The application of the SCOPE model in step (2) generates simulated data of energy flux in the urban environment. Specifically, the basic data collected in the previous step is input, and the SCOPE model based on plant physiology, radiative transfer and micrometeorology is applied to simulate the radiative transfer and energy balance process between soil, vegetation and atmosphere in the city using a time series model to generate simulated data related to the vegetation cooling process.

[0017] The latent heat flux (LE) output of the SCOPE model described in step (3) is corrected by taking into account the unique microclimate conditions in cities, especially the influence of impervious surface cover. The latent heat flux output of the SCOPE model is corrected using the Built-Up Area Index (BUAI), and the calculation formula is as follows:

[0018] LEsimulated=LEc+LEs*(1-BUAI),

[0019] LEc represents vegetation latent heat flux, and LEs represents soil latent heat flux.

[0020] The quantification of vegetation evapotranspiration cooling effect described in step (4) specifically involves clarifying the cooling effect of vegetation evapotranspiration based on the model output, defining the vegetation evapotranspiration cooling effect (ECoV) index, and calculating it using the following formula:

[0021] ECoV=(LE-LEmin) / (LEmax-LEmin);

[0022] LE is the corrected latent heat flux, and LEmin and LEmax represent the minimum and maximum latent heat flux within the urban area, respectively. The model output results are used to quantify them.

[0023] The step (5) described above quantifies the cooling effect of vegetation shading. Specifically, it clarifies the cooling effect of vegetation shading based on the model output, defines the vegetation shading cooling effect (SCoV) index, and calculates it using the following formula:

[0024] SCoV=((Tc-Ts)-(Tc-Ts)min) / ((Tc-Ts)max-(Tc-Ts)min);

[0025] Tc is the canopy surface temperature, Ts is the soil surface temperature, (Tc-Ts) represents the magnitude of the influence of the vegetation canopy on the surface temperature, and (Tc-Ts)min and (Tc-Ts)max represent the minimum and maximum values ​​of (Tc-Ts) within the urban area, respectively. The model output results are used to quantify them.

[0026] Step (6) will include detailed operations such as selecting a suitable interpolation method and defining the output resolution.

[0027] This invention proposes the concepts of "ECoV" and "SCoV," scientifically defining and quantifying the evapotranspiration and shading cooling effects of urban vegetation, providing researchers with a deeper understanding of the cooling effects of urban vegetation. This method has practical significance for guiding urban greening and planning, and by scientifically quantifying the effects of evapotranspiration and shading cooling, it can provide decision support for urban planners and policymakers.

[0028] Beneficial effects of the present invention

[0029] This invention not only provides an accurate and detailed assessment tool, but also offers urban planners and decision-makers a deeper understanding of the role of vegetation in microclimate regulation, helping them to make more rational urban greening plans. Furthermore, this invention utilizes the latest remote sensing and data processing technologies to ensure the accuracy and practicality of the assessment results. Attached Figure Description

[0030] Figure 1 This is a flowchart of the quantitative evaluation method for the urban vegetation evapotranspiration and shading cooling effect of the present invention.

[0031] Figure 2 This shows the distribution of the cooling effect of urban vegetation evapotranspiration in Shanghai during key moments of the day during a heatwave.

[0032] Figure 3 The distribution of the cooling effect of urban vegetation shading in Shanghai during key moments of the day during a heat wave.

[0033] Figure 4 Comparison of latent heat flux measured by SCOPE simulation and eddy flux tower. (a) Qingpu station; (b) Xujiahui station. Detailed Implementation

[0034] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0035] This invention uses Shanghai as the target area for a quantitative assessment of the effects of urban vegetation evapotranspiration and shading on cooling. As an international metropolis, Shanghai's complex urban structure and ever-expanding green space provide a unique context for this type of research. Shanghai has a subtropical monsoon climate and experienced a prolonged heat wave in the summer of 2022 (June-August).

[0036] First, based on the stability of the meteorological conditions, the simulation was conducted from August 7th to 9th, 2022. Using open high spatiotemporal resolution remote sensing and meteorological data, the data required by the SCOPE model to describe vegetation, soil, and meteorological characteristics were collected (Table 1). Image preprocessing was performed using Sentinel-2 data to calculate vegetation characteristic parameters such as leaf area index, as well as the BUAI parameters required for model output correction. Urban vegetation height parameters were provided using forest canopy height data products obtained from GEDI lidar measurements and Landsat data. Meteorological (e.g., temperature and relative humidity) and soil moisture data were provided from the China Meteorological Administration Land Surface Data Assimilation System (CLDAS-V2.0) dataset. All parameters were resampled and unified to a spatiotemporal resolution of 1 h / 100 m.

[0037] Subsequently, the Soil-Canopy-Observation of Photosynthesis and Energy Fluxes (SCOPE) model was used for data simulation. Model parameters are set as shown in Table 2, yielding preliminary urban energy flux data. BUAI, normalized from 0 to 1, was used to correct the model's predicted soil latent heat flux (LEs), ensuring the model accurately captures the water and energy dynamics of the urban environment. Based on the corrected simulation results, ECoV (Energy Coronavirus) was calculated. Figure 2 ) and SCoV Figure 3 The study also generated a high-resolution spatial distribution map of the cooling effect of vegetation in Shanghai.

[0038] The case study also used data from two eddy flux tower stations located in the city center (Xujiahui Station) and the suburbs (Qingpu Station) to verify the accuracy of the latent heat flux output by the model. Figure 4 By applying urban environmental correction methods, the model's prediction accuracy was significantly improved, enabling it to accurately and efficiently simulate the magnitude and variation of the cooling effect provided by urban vegetation during heat waves.

[0039] Under the influence of extreme high temperatures and other urban environmental factors, urban vegetation evapotranspiration-shading cooling exhibits a unique temporal dynamic pattern, forming different spatial distribution patterns of cooling effects at several key time points. Overall, suburbs show higher vegetation evapotranspiration and shading cooling effects compared to city centers, especially at midday, where the difference is most significant. Parks, green spaces, community green spaces, and farmland show significant evapotranspiration and shading cooling benefits at midday, but more than half of the areas experience insufficient cooling due to low vegetation cover. The overall cooling effect is least significant at sunrise and sunset, possibly influenced by radiation balance and convection. Furthermore, the cooling effect may be slightly anomalously reduced in the afternoon due to extreme heat and high solar angle. The study also found that leaf area index plays a crucial role in the spatiotemporal distribution pattern of urban vegetation evapotranspiration and shading cooling effects, meteorological forcing factors play an important spatiotemporal moderating role, and plant biophysical and biochemical characteristics are fundamental parameters determining the magnitude of plant cooling effects.

[0040] In summary, this case study verifies the effectiveness and feasibility of the method for quantitatively analyzing urban vegetation evapotranspiration and shading cooling effects with high spatiotemporal precision. This model can provide a reference for future research on urban vegetation cooling and has significant application value for urban ecological planning in climate adaptation.

[0041] Table 1. Sources and processing methods of the main input parameters used in the case study

[0042]

[0043]

[0044] Table 2. SCOPE Model Option Settings

[0045] 1 lite 1 calc_fluor 1 calc_planck 1 calc_xanthophyllabs 1 soilspectrum 1 Fluorescence_model 1 applTcorr 0 verify 1 saveCSV 0 mSCOPE 1 simulation 0 calc_directional 0 calc_vert_profiles 0 soil_heat_method 1 calc_rss_rbs 1 MoninObukhov 0 save_spectral

[0046] Note: The meaning of each option can be found in the SCOPE model usage instructions.

Claims

1. A quantitative evaluation method for the effects of urban vegetation evapotranspiration and shading on cooling, characterized in that, The specific steps are as follows: (1) For the research objectives and regions, collect basic data according to the requirements of the SCOPE model, including meteorological, vegetation and soil characteristic data; (2) Using the SCOPE model for time series simulation, simulated data of energy flux in the urban environment are generated; (3) The latent heat flux (LE) output of the SCOPE model is corrected by using the permeability ratio index in response to the unique microclimate conditions of the city. (4) Define vegetation evapotranspiration cooling effect ECoV to quantify the vegetation evapotranspiration cooling effect; (5) Define vegetation shading and cooling effect SCoV to quantify the vegetation shading and cooling effect; (6) Based on GIS technology, spatial interpolation was performed on ECoV and SCoV to generate a high-resolution spatial distribution map of vegetation cooling effect; The latent heat flux (LE) output of the SCOPE model described in step (3) specifically takes into account the unique microclimate conditions in cities, especially the influence of impervious surface cover. The latent heat flux output of the SCOPE model is corrected using the built-up area index (BUAI). The calculation formula is as follows: LEsimulated=LEc+LEs*(1-BUAI), LEc represents vegetation latent heat flux, and LEs represents soil latent heat flux.

2. The quantitative assessment method according to claim 1, characterized in that, In step (1), the vegetation feature data includes leaf area index, canopy water content, chlorophyll content, and tree height; the meteorological feature data includes air temperature, air pressure, relative humidity, and wind speed; the soil feature data includes soil relative humidity; and the data are processed to a uniform spatiotemporal precision to provide the necessary input parameters for model calculation.

3. The quantitative assessment method according to claim 1, characterized in that, The application of the SCOPE model in step (2) generates simulated data of energy flux in the urban environment. Specifically, for the basic data collected in the previous step, the SCOPE model based on plant physiology, radiative transfer and micrometeorology is applied to simulate the radiative transfer and energy balance process between soil, vegetation and atmosphere in the city using a time series model, generating simulated data related to the vegetation cooling process.

4. The quantitative assessment method according to claim 1, characterized in that, The quantification of vegetation evapotranspiration cooling effect described in step (4) specifically involves clarifying the cooling effect of vegetation evapotranspiration based on the model output, defining the ECoV index of vegetation evapotranspiration cooling effect, and calculating the formula as follows: ECoV=(LE-LEmin) / (LEmax-LEmin), LE is the corrected latent heat flux, and LEmin and LEmax represent the minimum and maximum latent heat flux within the urban area, respectively. The model output results are used to quantify them.

5. The quantitative assessment method according to claim 1, characterized in that, The quantification of the cooling effect of vegetation shading mentioned in step (5) specifically involves clarifying the cooling effect of vegetation shading based on the model output, defining the SCoV index of the cooling effect of vegetation shading, and calculating the formula as follows: SCoV=((Tc-Ts)-(Tc-Ts)min) / ((Tc-Ts)max-(Tc-Ts)min); Tc is the canopy surface temperature, Ts is the soil surface temperature, (Tc-Ts) represents the magnitude of the influence of the vegetation canopy on the surface temperature, and (Tc-Ts)min and (Tc-Ts)max represent the minimum and maximum values ​​of (Tc-Ts) within the urban area, respectively. The model output results are used to quantify them.

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