Due to the aggravating of urban heat island (UHI) phenomenon, the correlation between urban physical spatial form at street level and microclimate has drawn the attention of researchers gradually over recent years. As the densest core area with buildings, traffics and human activities in the city, the urban physical space of Central Business District (CBD) is characterized by high coverage, height and development intensity, and exerts direct effects on urban microclimate. Nevertheless, the quantitative studies on the relationship between the built environment of CBD and microclimate are relatively less for now, and so is the urban design criteria and guidelines for the climate adaptability. Therefore, this work aims to explore the impacts of the urban physical spatial form of CBD on the outdoor microclimate and related thermal comfort and building energy consumption under the typical summer conditions of Nanjing city, and propose the design guidelines and optimization strategies of urban space form for climate adaptability in CBD area.
Firstly, this thesis has investigated the spatial and temporal characteristics of surface and canopy layer heat island distribution in Nanjing city by using the data of land surface temperature and measured air temperature, and analyzed the reason and variation regularities of the UHI in Nanjing. Based on the results, some street blocks in the area with highest UHI intensity are selected as the typical cases, and the correlation between the urban geometries and microclimate has been examined and discussed.
Then, this study has proposed the research methodology of classifying, analyzing and quantifying the parameters and controllable variables related to the urban physical spatial form at three level, including street canyon geometries, urban texture, and building form and arrangements. Furthermore, the numerical simulation is employed to evaluate and analyze the effects of multiple parameters and controllable variables of urban physical spatial form on the microclimate and related outdoor thermal comfort and building energy consumption. The proposed method is propitious to the comparison and preferable selection among various urban design schemes for climate adaptability.
In the meantime, this research has shown the difference between the impacts of the localized weather data and the recorded one on building energy simulation results, and highlighted the importance of the implementing the localized weather data in building energy simulations and predictions which can make the simulation results more pertinent, accurate and practical.
Finally, based on the conclusions and some achievements, the specific optimization strategies and solutions for climate adaptive design on 9 aspects, including street aspect ratio, orientation, street geometry, building site coverage, building height, floor area ratio, plot layout, building form and arrangements etc., have been summarized and induced with the aim of thermal comfort and low energy consumption. Also, some case studies have been conducted by applying these optimization strategies.