Evaluation of the ENVI-Met Vegetation Model of Four Common Tree Species in a Subtropical Hot-Humid Area

Abstract

Urban trees can significantly improve the outdoor thermal environment, especially in subtropical zones. However, due to the lack of fundamental evaluations of numerical simulation models, design and modification strategies for optimizing the thermal environment in subtropical hot-humid climate zones cannot be proposed accurately. To resolve this issue, this study investigated the physiological parameters (leaf surface temperature and vapor flux) and thermal effects (solar radiation, air temperature, and humidity) of four common tree species (Michelia alba, Mangifera indica, Ficus microcarpa, and Bauhinia blakeana) in both spring and summer in Guangzhou, China. A comprehensive comparison of the observed and modeled data from ENVI-met (v4.2 Science, a three-dimensional microclimate model) was performed. The results show that the most fundamental weakness of ENVI-met is the limitation of input solar radiation, which cannot be input hourly in the current version and may impact the thermal environment in simulation. For the tree model, the discrepancy between modeled and observed microclimate parameters was acceptable. However, for the physiological parameters, ENVI-met tended to overestimate the leaf surface temperature and underestimate the vapor flux, especially at midday in summer. The simplified calculation of the tree model may be one of the main reasons. Furthermore, the thermal effect of trees, meaning the differences between nearby treeless sites and shaded areas, were all underestimated in ENVI-met for each microclimate variable. This study shows that the tree model is suitable in subtropical hot-humid climates, but also needs some improvement.

Correlative Impact of Shading Strategies and Configurations Design on Pedestrian-Level Thermal Comfort in Traditional Shophouse Neighbourhoods, Southern China

“…The peaks of Ta from the simulated result are approximately 37 • C, while a discrepancy of approximately 1.5 • C exists between the measured points in the alley and the boulevard (i.e., O-Al-s and O-Tr-s) in peak time (38.7 and 36.9 • C at 1600H, respectively). This overestimation of Ta for canopy shading by trees in the ENVI-met simulation was also reported in Liu, Zheng and Zhao [50]. In contrast, the simulated values of MRT and PET illustrate distinct differences among the three canyons, and the PET value is highly related to MRT.…”

“…Developed from the arcade street, Group 2-1 analyses the correlative Table 3 lists additional details about the boundary conditions for simulation. The street greenery in the TR canyon is Flocculus banyan, and the height of the trees is 12 m. The leaf area density (LAD) of tree model in ENVI-met (see Table 4) was built based on the situation in the field; the default settings (tree in very dense and free stem crown layer) and the value in other research [49,50]. 1 13.0 g/kg Soil initial temperature 2 305 K (0-20 cm)/307 K (20-50 cm)/306 K (<50 cm) Soil wetness 2 30% (0-20 cm)/40% (20-50 cm)/50% (<50 cm)…”

Interrelationships between Land Use Land Cover (LULC) and Human Thermal Comfort (HTC): A Comparative Analysis of Different Spatial Settings

“…The majority of the ENVI-met simulations were validated, known as the sensitivity analysis, through site measurement before finalizing their modelled results. Some research tested on one or two microclimate parameters, such as air temperature (e.g., Ghaffarianhoseini et al [40]; Peng and Jim, [28]), while other research tested more than two microclimate parameters, such as such as air temperature, surface temperature, relative humidity, global radiation, and solar radiation (e.g., Salata et al [50]; Liu et al [57]). In this study, we only tested on air temperature data, since there is a limitation to acquire all the data from the Meteorological Department of Malaysia (MET).…”

A microclimate regulation study of Ficus altissima under winter conditions in lower subtropical China

“…Feng et al (2021) found that mango tree transpiration consumed 40% (sunny) to 60% (cloudy) of a canopy's total daily energy and continued to play a role in cloudy days, making vegetation absorb the heat of surrounding air. Liu et al (2018) conducted ENVI-MET simulation on four kinds of trees (Michelia alba, Mangifera indica, Ficus microcarpa, and Bauhinia blakeana), and identi ed that the model data were more stable than the measured data. Leaf surface temperature, steam ux, air temperature, and humidity were lower than the observed values.…”