Numerical Study Of The Impact Of Green Space Layout On Microclimate In Residential District

Green space offers great benefits to urban environment quality. There has been lots of research on urban green space planning and landscape ecological effect, however, few quantitative work has been carried out on its microclimate impact. Residential area is one of the major components of urban built environment, and the research on the influence of its inner green space layout on microclimate has great implications. The current relevant studies, have been more focused on greening quantity, with less concern for greening structure. Evaluation of wind field, thermal comfort and air quality is also important for microclimate research as well as thermal environment. Urban microclimate simulation software, like ENVI-met, have been increasingly applied with the development of the numerical modeling technology. Building numerical models are set up by using ENVI-met in consideration of typical residential greening forms and greening indexes. Data are analyzed and compared for different greening layouts. Microclimate analysis in this study includes, wind environment, thermal environment and thermal comfort, and particle concentrations. Associated issues are:definition of greening indexes, case setting of greening layouts, parameter setting and data collection. The main work and conclusions are as follows: (1) Models of central green land and home-site greenbelt are set up, and greening indexes are defined to characterize green land. Relevant indexes are green percentage of ground, green cover percentage, greening plot ratio, eco-greening plot ratio, landscape diversity index and deviation degree index. (2) Outdoor thermal comfort indexes are introduced and compared in relation with environmental parameters such as temperature and mean radiant temperature. And accuracy of using PMV as a thermal comfort index is proved. (3) Main features and numerical methods of the microclimate software ENVI-met are presented. Relevant parameters, such as leaf area density and emission rate, are given. (4) ENVI-met model is set up, and microclimate is evaluated for temperature, wind speed, thermal comfort and concentration of PM10. The results show that eco-greening plot ratio are positively correlated with day-time cooling effects and thermal comfort of green land, and negatively correlated with wind speed and PM10 concentration. Landscape diversity index of tree patch in home-site greenbelt is negatively correlated with cooling effects and deposition, while positively correlated with wind speed. As the landscape diversity index of tree patch in central green land grows larger, area of the single patch becomes smaller and its cooling intensity reduces. Meanwhile low wind speed area becomes larger, leading to low PM10 concentration. The deviation degree index of tree patch is negatively correlated with cooling effects and mean wind speed with no pronounced correlation with thermal comfort and PM10 concentration.