Research On The Influence Of High-rise Residential Green Space On The Microclimate In Xi'an

Rapid urbanization brings opportunities for human development,but also brings a series of environmental problems.This includes the emergence of urban heat island,a typical urban ecological problem.With global warming,the problem of high summer temperatures is getting worse.Changsha,chongqing,fuzhou,xi 'an and other cities are experiencing longer and longer periods of high temperature in summer,and the maximum temperature is on the rise,which has greatly damaged people's physical and mental health and living comfort.With the development of cities,population gathering,land shortage and other related problems gradually break out,especially in the old city areas of large cities or small and medium-sized cities with land shortage.As an important part of the urban built environment,the residential area develops gradually to the high altitude under the macro-guiding mechanism of intensive utilization of urban land resources,which makes the high-rise residential area usher in a new high level of construction.The green space in urban residential areas is the main place for residents' leisure activities and neighborhood communication,which has an important impact on the outdoor micro-climate environment of residential areas.By extracting the layout model of typical buildings in xi 'an residential area and the corresponding green space form,this paper starts from three aspects of green rate,tree proportion and green space layout form,and mainly simulates and analyzes the wind environment,thermal environment and thermal comfort under different green space layout and parameters in high-rise residential area by building the model of envi-met.The main work and research contents are as follows:(1)In order to understand the climatic characteristics of the city and the characteristics of high-rise settlements,A field survey was conducted on 150 high-level residential areas in the xi 'an economic and technological development zone,Xi'an Hi-Tech Industrial Development Zone,Qujiang new district,Chanba Ecological District four state-level development zone,Based on the analysis of the architectural layout of theseresidential areas and the classification and reading of the green space pattern,two kinds of typical building layout forms of high-rise residential areas in xi 'an and the typical green space layout forms under these two typical building layout forms are finally extracted.(2)with reference to the model of typical high-rise settlements in xi 'an,four cases with similar scale,spatial location and geographical environment conditions are selected to conduct hourly measurement of microclimatic factors on typical summer and winter climate days.Then,through dynamic analysis and comparison,the distribution,variation characteristics and microclimate of air temperature,relative humidity and wind speed in measured high-rise residential areas are summarized.(3)Outdoor thermal comfort index was introduced to evaluate the microclimate of high-rise residential area.Based on the relationship between indexes and environmental parameters such as air temperature and wind speed,the accuracy difference of different indexes is studied,which provides the accuracy basis for the index PMV used in this paper.(4)The microclimate of high-rise residential areas in xi 'an was simulated by Envi-met,and the microclimate was evaluated from three aspects: temperature,wind speed and thermal comfort.The results show that : combining with the climate characteristics and simulation results of xi 'an,the micro-climate effect of high-rise residential greening is mainly heat preservation and wind shield in winter and sun shading and cooling in summer.The cooling effect of the percentage of green land and tree in the daytime was positively correlated with the thermal comfort and negatively correlated with the wind speed.Comparatively speaking,the increase of tree proportion has more obvious effect on the improvement of microclimate than the increase of green land ratio.The more homogeneous and dispersed the green space layout in the residential area,the worse the cooling effect in summer and the weaker the heat preservation and windshield effect in winter.Tall and dense trees can play a good role in cooling and humidifying in summer,but also reduce the overall wind speed in the residential area,thus affecting the thermal comfort.Therefore,when increasing the proportion of trees,the tree arrangement should be considered to form ventilation corridors in high-rise residential areas.