Modeling microclimatic effects of trees and green roofs/fa?ades in ENVI-met: Sensitivity tests and proposed model library

Urban green infrastructure furnishes one of the most effective ways to mitigate and adapt to climate change and the consequent thermal environment deterioration. ENVI-met, a holistic computational fluid dynamics model with various plant modules, has become a principal simulation tool to evaluate the thermal effects of urban greenery. This study emphasized the significance of clear and accurate ENVI-met vegetation modeling, aiming to formulate strategies to boost modeling data quality, veracity and rigor of ENVI-met-based simulation studies. This study applied a two-step framework. First, a series of sensitivity tests were conducted under hot and humid meteorological conditions to identify the microclimate-sensitive parameters and their relative cooling effects at the pedestrian level. The results identified leaf area density as the most significant parameter in ENVI-met tree modeling. Some compromises on root properties' input accuracy could be tolerated since they would not considerably hamper the overall simulation quality at the pedestrian level. For green roof/facade modeling, leaf area index and leaf angle distribution were significant and should be accurately input to ensure simulation quality. Second, for the microclimate-sensitive parameters in modeling, this study used commonly-planted species in subtropical South China cities to demonstrate a systematic workflow of developing an ENVI-met vegetation model library. The library could include basic plant physical traits, plant albums, reference values of the microclimate-sensitive parameters, and recommended alternative modeling data sources. The vegetation model library could provide a helpful and actionable package from which researchers can quickly obtain accurate input values without highly specialized knowledge or instruments.