Research On Climate Adaptation Of Traditional Neighbourhoods Morphology In Hot-humid Climate

Neighbourhood is the basic unit of urban.Its morphology not only effects on the spatial atmosphere but also relates with its microclimate.However,the modern neighbourhood morphology in China is difficult on providing comfortable living environment and meeting the challenge from climate change,since the core principle of planning behind it is following the rational functionalism and ignoring the urban climate and environment.On the contrary,given the impact from regional climate and culture,the traditional urban present special characteristic morphology and climate adaptation.The experience of historical planning is standing behind those neighbourhoods,which is a valuable paradigm for modern urban design.The Traditional Shophouse Neighbourhoods?TSNs?,featured with continuously arcade for pedestrians,are widely distributed in hot-humid climate zone of South China,and mainly formed at the beginning of 20^th century.They are considered as climate-adapted morphology by means of their compact layout and shading strategy.This research integrates the perspective of urban design with methodology of urban climatology for investigating on the climate adaptation in TSNs and providing practical guidance for urban planning and design.Firstly,the history,distribution district,and corresponding climate of TSNs are investigated from a global perspective.Then,their layout typology,street type design and spatial scale range are summarized.A series of on-site microclimatic measurement were conducted in a classic TSN of Guangzhou and Xiamen respectively during typical summer day.The ENVI-met was adopted to simulate the microclimate in selected area and the Physiological Equivalent Temperature?PET?was applied on assessing the pedestrian-level thermal comfort?PTC?.Meanwhile,the effectiveness of the climate design strategies in TSNs were verified and their thermal environment characteristics were compared.From the perspective of urban design,a simplified parametrical model for neighbourhood morphology design is generated,which can describe the layout type,street design and spatial scale of TSNs.By means of Grasshopper and Ladybug,a toolkit is developed for achieving the following workflow:parametrical model generation,simulation model transformation,numerical simulation?in ENVI-met?and result analysis.Based on the above measurement and toolkit,the parametrical simulations are carried out for studying the synergistic effects between different variables on outdoor thermal environment at the two-scale level,which are block and street respectively.The impact from neighborhood layout,street aspect ratio,orientation,the aspect ratio of arcade and the coverage of the canopy cover on pedestrian thermal comfort are investigated.For comparing the performance of outdoor thermal environment in different models,the Desirable Thermal Perception?DTP?and Cumulative PET Load?cPETL?are adopted as the assessment index in different scales.The results illustrate that the impact from variables on the PTC are distinguished in different street type.The street with high tree canopy coverage presents the most stable thermal environment.Alleys and boulevards have better thermal environment in the neighbourhood under the net pattern,but arcade streets provide better thermal environment in the neighbourhood which is mainly consisted of east-west-oriented streets.The moderating tendencies of PTC with varying aspect ratio of street are different between neighbourhood layouts.Moreover,the benefit from shading strategy will be limited for pedestrians when the aspect-ratio of arcade is greater than2 or the tree canopy coverage is less than 22%in its street.For avoiding the street environment is deteriorated by over shaded,the relationship between the Sky View Factor?SVF?in models and its corresponding cooling performance??cPETL?are investigated to balance the needs of shading and urban heat dissipation.According to the results,the SVF in a street is linearly related to its cooling effectiveness in the same street type.Building presents higher effectiveness on reducing cPETL comparing vegetations,since the?cPETL in alleys and arcade streets is greater than that in boulevards with the same SVF.In order to construct relative comfortable environment in a street canyon and avoid over shaded on pavement?SVF over 0?,the SVF of arcade-street midpoint should be controlled in the range of 0.3-0.5 and the aspect-ratio of arcade is between 1-1.33;in boulevards,the SVF of the road midpoint should be over 0.2 and the tree coverage area is not less than 33%.According to the above research,the paper finally discusses the core issues in the modern urban planning system from a critical point of view and proposes the necessity of applying the urban design guidelines on controlling the morphology in neighbourhood.The urban design strategies are proposed for achieving climate-adapted neighbourhood morphology in hot-humid climate zone,based on historical experiences,practical references,and research results.