ObjectiveNowadays, with the continuous improvement of computer performance, numerical simulation has become an important study method in predicting and evaluating microclimate. Vegetation is one of the important elements in landscape design and plays a significant role in thermal environment, its simulation performance under hot-humid conditions is worth evaluating comprehensively. This paper is to validate the adaptability of city microclimate simulating software ENVI-met (V4.2 Science) in simulating both physiological and microclimatic performance of Ficus microcarpa in hot-humid region of Guangzhou, southern China.

MethodBy measuring the crown form, foliage property and root form of Ficus microcarpa in Guangzhou Region and the tree model was built and analyzed by ENVI-met. The simulation result was compared with observation data measured from spring and summer in 2017.

ResultResults showed that, for physiological parameters, the simulated leaf temperature has the same trend with the measured one, while the simulated data is much higher in the summer afternoon. The simulated transpiration rate was close to the measured data in the morning and evening, while the peak value in midday was obviously lower than the measured one. In microclimatic parameters, the daily changing trends of simulated microclimate parameters (solar radiation, surface temperature, air temperature, and air humidity) were consistent with the measured ones. The reduction rate of solar radiation and reduction value of surface temperature from tree canopy were close to the measured values. The air temperature data under tree and inside tree crown in varied directions were higher than the measured data, and the humidity data were lower. The temperature and humidity difference between the treeless site and the shading site were much smaller than the measured ones. The root mean square error and index of agreement were used as the indicators of statistical evaluation, hence showing that the ENVI-met model was capable of predicting the microclimate with good accuracy. The error was acceptable and may be caused by the software version, the software calculation setting and the grid size resolution ratio of tree modeling.

ConclusionIn conclusion, ENVI-met can well simulate the physiological property and thermal performance trends of trees in hot-humid climate. This study comprehensively evaluates the performance of vegetation models, hence come up with the optimization suggestions for tree modelling and could be a strong support for the outdoor thermal environmental research in hot-humid regions of further studies.