A Study On The Diffusion Effect Of Urban Park Cold Island In Summer From The Perspective Of Urban Design

Previous studies have shown that urban green land has a cooling island effect,which is beneficial to alleviate urban heat island,especially in hot summer areas.Little research on the phenomenon of the spread of cooling island in urban areas under the influence of urban wind,while the latter has a more positive and broad meaning for mitigating the UHI.It is the main purpose of this study to develop qualitative and quantitative research on the controllable elements from the perspective of urban design,and to develop urban design strategies and tools to maximize the diffusion effect of cold island.The study first selected two green land in Chinese city of Nanjing to conduct field observations.The first-hand data obtained from the field observations contributed an empirical basis for this research.And then to verify and adapt the ENVI-met microclimate simulation platform with measured data.Meanwhile,it is necessary to conduct simulation analysis of various possible factor.Research shows that the spread of cooling island shows a downwind trend in spatial form.and its form is similar a palm shape.The area and temperature difference of the shape are mainly affected by the size,shape,and many other factors of green area,and have a big difference.The more essential key factor-the depth of the greenfield windward surface was selected and through the ideal model simulation and the case simulation test,the quantitative relationship between the windward surface depth of the green land and the diffusion range of the cold island is obtained.Based on this,a fast mapping method for the buffer area of the green land cold island is proposed.It could quickly determine the cold island diffusion range of any green land(morphology,size).The mapping method overcomes the shortcomings of ENVI-met simulation.Through the ideal model simulation and the example simulation test,the quantitative relationship between the windward surface depth of the green space and the diffusion range of the cold island is obtained.At the end of the study,using an example as a carrier,through the development of several urban shape optimization strategies(building windward surface area coefficient,wind gallery)in the buffer zone,it is shown that urban texture optimization at the urban design level in the buffer zone can effectively expand cold island diffusion effect.This study provides knowledge and tool support for the maintenance and expansion of the ecological cold island effect in green land-related urban design and planning control,with academic and practical value.