Research On The Influence Of Street Greening On Microclimate Of Old Urban Areas In Severe Cold Region

As an important part of exterior space,street space on the one hand has the function of traffic,on the other hand,the physical environment of street is closely related with the micro climate environment in the street which also has an effect on human thermal comfort.As the period of winter in severe cold region is very long,and the environment of climate in street space is not comfortable,which brings the city residents inconvenience.Therefore,it is urgent to study on the improvement of street micro-climate environment in severe cold region.Based on the research of the typical old city streets greening in severe cold region,this paper compares and analyses street micro-climate environment conditions under the influence of different greening forms,and then sums up the most suitable streets greening strategy which can be applied to the climatic characteristics of severe cold region.By reading the literature and doing field investigations,this paper chooses greening structure,tree planting density and canopy differences as factors affecting street micro climate environment.In order to ensure the scientificalness and comprehensiveness of the research,on the one hand,this paper selects the representative street of the old urban area in Harbin to do the field measurements,on the other hand,using ENVI-met software to simulate the micro climate of street in the old urban area based on the database from field measurements.The results show that the green layout of streets has a significant influence on the microclimate of street pedestrian space.In terms of the greening structure,the more complex the green structure is,the smaller the wind speed,the lower the air temperature and the higher the relative humidity will be,which is especially obvious in spring;Tree planting density should be determined according to the crown of the tree,and when the width of planting spacing is equal to or slightly less than the crown of the tree,the micro climate gets better;The crown width of tree has a relatively significant influence on air temperature,while leaf area density effects on wind speed in a more obvious way.According to the climate characteristics of severe cold region,elm and willow are suggested to be street greening trees.In addition,when only a few trees scattered in the street,the trees have little effect on the wind speed;In the winter,trees and shrubs still have an effect on the micro climate of street space even they are leafless,and the effect is more obvious when the greening structure gets more complicated or the crown of tree gets bigger.