Analysis Of Spatial Pattern And Microclimate Environment In Typical Street Blocks Of Shanghai Central City

Global climate change and Urbanization are two important global issues in the21 st century.On the one hand,climate change has led to the emergence of extreme weather phenomena such as high-temperature heat waves and increasing precipitation.On the other hand,the rapid development of urbanization has led to an increase in the density of urban population and buildings,and the impact of human activities on cities gradually increased.Under the background of climate change and rapid urbanization,urban climate problems such as urban heat islands,rain islands,and dry islands have emerged,which have brought a series of impacts on the daily life of urban residents.As one of the most frequent places for daily activities of people,the comfort of the microclimate environment directly affects people's daily life experience and quality.Therefore,research on urban microclimate effects is important for the healthy development of urban climate and the production and life of residents.Shanghai,as China's first-tier big city,has become a leading city in the development of the Yangtze River Delta city group.Since the reform and opening up,it has undergone an extraordinary development.The phenomenon of urban heat island is more obvious.Therefore,Shanghai is regarded as representative study area.Based on the study of urban climate effects,this paper focuses on the micro-climate environmental effects in urban areas at block scales.It mainly studies the interaction among the environment capacity control indicators of block,building layout,air temperature,relative humidity,average radiation temperature and physiological equivalent temperature(PET).The main contents of the study are as follows:First of all,we investigated the environmental capacity control indicators including floor area ratio,building density,average building height and so on,and the architectural layout of blocks in the 152 blocks of residential areas in the enclosed area of Inner Ring,southern and northern elevated highway in Puxi district.The survey found that the spatial pattern parameters in the area are very wide: The floorarea ratio ranges from 0.81 to 6.49,the building density ranges from 16.58% to66.72%,the average building height ranges from 7.91 m to 78.13 m,and the green space rate ranges from 0.71% to 48.29%.The architectural layout of this block includes four types of determinants,point groups,enclosures and hybrids,so the architectural forms in the area are complex and diverse.On this basis,we chose 41 blocks as typical cases to study in combination with environmental capacity control indicators and architectural layout patterns.Secondly,the author took the floor area ratio index,which indicates the comprehensive development intensity of the block as the primary factor and took the floor area ratio 6,5,4,3,2.5,2,1.5,1.2,and 0.8 as the dividing line,divided the 41 typical street blocks into nine types.The number of 91 named Xietuxin Village in the Appendix was selected for actual measurement to verify the accuracy of the model.The comparison of the measured value and the simulated value indicates that the software can reasonably simulate the temperature change in the neighborhood.After verification,we used ENVI-MET software to establish a microclimate model and conducted numerical simulation.Based on the simulation results,we analyzed the distribution characteristics of air temperature,relative humidity,average radiation temperature and physiological equivalent temperature for various cases,and proposed improvement strategies for high temperature areas of individual cases,then further simulated and analyzed.In addition,when analyzing the air temperature and relative humidity,we input data of the initial boundary conditions as the reference value and then calculated the difference among all temperature values,relative humidity values and input values of each grid point within the block(represented by ?T and ?RH respectively)to characterize the influential strength and range of all factors,such as block building or greening,on the air temperature and relative humidity of the block.Finally,on the basis of the above,the multivariate regression analysis method was used to explore microclimate effecting factors both in street block level andmonitoring site level.In street block level,we mainly studied the effects of block shape parameters such as volume ratio,building density,average building height,green space rate,block size on air temperature,relative humidity,average radiation temperature,and physiological equivalent temperature.The study found that compared with the green area rate and the use of high reflectance materials,the three environmental capacity control indicators of volume ratio,building density,and building average height have a greater impact on the microclimate environment of the block.At the monitoring sites of the blocks,the influence factors of physiological equivalent temperature were discussed.We found that the influence of air temperature,average radiation temperature,and relative humidity was significantly positively correlated with the physiological equivalent temperature.When the wind speed is in the range of 0.01198~4.3767m/s,there is a significant negative correlation with the effect of physiological equivalent temperature.The different locations of the monitoring points also have an influence on the physiological equivalent temperature,and the thermal comfort of the monitoring points above the road is usually worse than that under the tall trees.In addition,the mean radiation temperature has a greater explanation for the physiological equivalent temperature than other factors.Through this study,we found that the layout of the architectural forms in the neighborhood is the main factor that affects the microclimate environment of the neighborhood.However,for the built blocks,we can still fine-tune the elements of the blocks in the details to further improve the microclimate environment in the blocks.Studying the micro-climate environmental effects mechanisms in urban block scales is beneficial to develop adaptive measures for climate change in block scale and provide positive suggestions for creating green settlements.