Correlation Research On Urban Micro-climate And Urban Morphologies

With the furthering of urbanization process, the high density and high plot ratio urban development pattern has caused the a series of climate problems to the cities including bad ventilation conditions, air pollution, urban heat island effect and so on. These problems not only decrease the comfortableness from the residents in urban life, but also seriously influence their health. The research is targeting at scientifically analyzing the correlated internal mechanism between urban microclimate and urban morphology, so as to summarize the climate mitigation strategy to corresponding planning and architectural design.The methods of field measurement, numerical experiment and SPSS regression analysis are adopted in the research. The elements of urban microclimate and composition parameters of urban morphology are summarized on the basis of literature consulting. The wind speed ratio and urban heat island strength are employed as microclimate evaluation indicators; the building density, plot ratio, greening rate, wind face area ratio and ventilation overhead ratio are taken as evaluation indicators to the urban morphology parameters. The high density urban area in Lingshuiwan Area Dalian within the range of 2km×2km is taken as research object, the 3D tools as Auto CAD, ArcCIS, Rhino and Grasshopper, etc are comprehensively employed to establish the urban planning information model including landform, underlying surface material, building height and function, and to have model optimization processing according to numerical simulation demands.5-day uninterruptible actual measurement at the field in Lingshuiwan Area, and the microclimate data including temperature, wind speed, humidity, underlying surface material temperature, etc. The internal mechanisms to different underlying surface microclimate changes and generation of differences are preliminarily analyzed through analyzing the actual measured data.The climatic numerical experiment is conducted by means of coupling the two tools with different scales-WRF and CFD. The high precision microclimate information is described in the prerequisite of fully considering the big range of actual meteorological background in the city. Among them, WRF is a mesoscale simulation technique in the field of meteorology, and the background meteorological parameter simulation with grid precision lkm and total study area 156km is conducted through adjusting the boundary conditions, physical plan parameters and grid settings, etc. The WRF results are taken as boundary conditions to CFD simulation, and the microclimate numerical experiment with precision 20m is achieved. The average error between actual measured value and simulated value of wind field is determined by comparison with field actual measured data is 0.17m·s-1; the average error of temperature field is 0.24?. This result indicates that the results of numerical experiment have a very high reliability.Employing SPSS software to analyze the relevance between the numerical experiment results and urban morphology parameters, and to establish the simple linear regression model between the two. The regression results indicate that the relevance between plot ratio and wind speed ratio is the highest, and R2 is 0.591; the relevance between greening rate and wind speed ratio regression is the lowest, and R2is 0.398. When the building density is controlled below 40%, the wind speed ratio could reach above 0.71; when the plot ratio is controlled below 3.0, the wind speed ratio could reach above 0.62; when the greening and water coverage rate is controlled to be above 15%, then the wind speed ratio could reach above 0.96. The relevance of plot ratio, afforestation water coverage rate and heat island intensity regression is very high, and among them the relevance coefficient between plot ratio and heat island intensity R2 is 0.587; the relevance coefficient R2 between the greening rate and heat island intensity is 0.586. When the building density reaches above 40%, the heat island intensity could reach above 7.77?; when the plot ratio reaches above 3.0, the heat island intensity could reach above 8.65?; when the greening rate is controlled above 15%, then the heat island intensity could be controlled within 3.82?. The research results indicate the plot ratio could play a very evident role no matter in improving the wind speed ratio or controlling the heat island intensity, therefore, the plot ratio within the area should be first controlled in urban construction.Dalian urban planning strategy is finally put forward in the research based on microclimate analysis, including rationally improving the land development intensity, protecting the open spaces, establishing the urban ventilation corridor, rational arrangement of roads, controlling urban height and architectural form optimization method, and so on.An urban climatic numerical experiment method from macro to micro is established in this thesis, to analyze the relevance mechanism between urban climate and urban morphology parameters. It could provide a scientific and accurate thermal environment optimization strategy with application prospect for urban planning, urban design plan or the completed areas, and it will contribute to improve the scientificity of urban planning and design, and will provide a technical support to establishment of a sustainable and livable city.