The Evapotranspiration Characteristics and Evaporative Cooling Effects of Different Vegetation Types on an Intensive Green Roof: Dynamic Performance Under Different Weather Conditions

Previous research has demonstrated that the multiple environmental benefits of green roofs are primarily associated with their evaporative cooling effect. However, current studies on green roof evapotranspiration (ET) mainly focus on extensive green roofs, and the evaporative cooling effect of intensive green roofs is still unclear. Using the intensive green roof of AQUA City in Nanjing as a case study, this research employs the three-temperature (3T) model combined with high-resolution thermal infrared imagery obtained via an unmanned aerial vehicle (UAV) to estimate the ET of different vegetation types. The study aims to explore the spatiotemporal variations in surface temperature, evapotranspiration (ET) rate, and evaporative cooling rate for various vegetation types under typical seasonal (summer and winter) and weather conditions (sunny, cloudy, and rainy before and after rainy days). The results showed that: (1) the ET rates and evaporative cooling effects of different types of vegetation differed significantly, with shrubs having the fastest ET rates, followed by arbors, and grasslands having relatively low ET rates. (2) Solar radiation and air temperature are the most crucial meteorological parameters for inducing ET on green roofs. In this study, the evaporative cooling performance showed the patterns of summer > winter and sunny > cloudy > rainy days. (3) In the spatial distribution of tree and irrigation plant groups, some low-temperature diffusion phenomena to the adjacent small microenvironments were evident, while the diffusion effect in winter is smaller and mainly shows the opposite warming characteristics. This study offers a valuable reference for quantifying the ET and evaporative cooling effects of various vegetation types on intensive green roofs, facilitating the optimization of vegetation configuration and supporting sustainable urban development.