| With the rapid progress of urbanization,urban development has brought a living environment with high density and high volume ratio,and the living environment and natural climate have gradually deteriorated.The destruction of the structure of the natural underlying surface in the city,the imbalance of material and energy and other factors lead to the urban heat island effect.In recent years,the heat island problem continues to affect human behavior around the world.The decline in the quality of outdoor environment makes many residents more dependent on indoor space.And this in turn aggravates the internal friction in the city,and so on and so on.Therefore,in recent years,many experts and scholars have carried out research on microclimate and landscape space,architecture and city,analyzed and summarized effective design strategies to improve the microclimate environment.As a multifunctional network system,greenway can connect biological habitat,natural landscape elements and towns.Greenway ecology can alleviate the conflict between human beings and nature brought about by the rapid process of urbanization,improve the regional ecological environment,and have a variety of benefits and values.In the existing literature,the microclimate research in the south of the Yangtze River is mainly focused on cooling and humidification in summer,but less on the microclimate landscape in winter,so this paper takes Zijinshan Greenway as the research object.The microclimate improvement schemes of different landscape design elements are analyzed by means of theoretical research,field investigation,field measurement,questionnaire survey,statistical analysis,software simulation,project design and so on,and the optimal site design scheme is obtained.In order to improve the winter microclimate landscape environment and create a more comfortable winter greenway travel environment.The main contents and conclusions of this paper are as follows:The main results are as follows:(1)Based on the field investigation of Zijinshan Greenway,the measurement sites and measured dates of different landscape design elements are selected to measure the autumn and winter microclimate of each survey area,and it is determined that the microclimate factors are affected by different variables.the analysis results show that for plant elements,plants can increase site humidity more effectively than water bodies and hard squares.In the areas with high canopy density and large overall leaf area,the daily average temperature difference is smaller and the daily average humidity difference is larger;plants can not only reduce the wind speed,but also increase the wind speed because of their different combinations;small evergreen trees and evergreen shrubs can effectively reduce the wind speed in winter.For water elements,the average humidity and wind speed of the measuring points with large water area are higher,and the larger the water area is,the stronger the regulating effect on the surrounding microclimate is.For road elements,the average wind speed,temperature and humidity are affected by the direction of the greenway.The wind speed of the greenway in the east-west direction is higher than that in the north-south direction,with an average height of 0.34 m in autumn and 0.3 m in winter;the temperature and humidity of the greenway in the north-south direction is higher than that in the east-west direction,with an average temperature of 0.09 ℃ and an average humidity of 0.8% higher;for the paving material,the temperature around the wooden floor is the lowest and the humidity is the highest in autumn and winter.(2)During the measuring time,a real-time questionnaire survey was conducted among tourists at each measuring point,and the index of human comfort was introduced to analyze the correlation between human comfort,tourists’ subjective feelings and microclimatic factors,as well as regional differences.It is determined that the degree of human comfort is directly related to microclimatic factors,and human comfort varies with temperature and humidity.It is concluded that microclimatic factors have different effects on the feelings of tourists in different types of greenways.The average DI value in autumn and winter is area A > area C > area B.The theoretical and practical values of human comfort index in zone B are low.The actual cold feeling of the human body in autumn is neither cold nor hot;in winter,the actual cold feeling of the human body is cold.The subjective perception and DI value of human body are related to microclimatic factors.The correlation results in autumn and winter are both positive correlation and strong correlation with temperature,negative correlation with humidity,and no correlation with wind speed.(3)By fitting the measured and microclimate simulation software ENVI-met simulation data to verify the feasibility of the software simulation,using ENVI-met to simulate the landscape elements of different schemes which can not meet the measured site conditions,and summarize the characteristics and results of microclimate change of landscape elements under different scenarios: for microtopography,its height is inversely proportional to the surrounding air temperature.The microtopography with large elevation can effectively slow down the wind speed of the site;the microtopography with different shapes has an impact on the surrounding temperature and humidity,but has little influence on the wind speed of the site;the smaller the area of the microtopography is,the greater the wind speed is;under the premise that the wind direction is easterly,the site average temperature ratio of the microtopography distributed in the northwest of the greenway is 0.1 0.2 ℃ higher than that in other directions of the greenway.For the water body,the cooling and humidification effect of the water body with strong continuity is more obvious than that of the site with weak continuity;the larger the water area is,the higher the surrounding wind speed is;the larger the water area is,the more stable the temperature and humidity of the surrounding site is.For plants,to a certain extent,when the plant spacing increases by 1 meter,the temperature decreases by 0.1 ℃;the plant crown width is proportional to temperature and humidity;trees can regulate the site microclimate more effectively than shrubs and ground covers;the wind speed of greenways in grassland and shrub-grassland communities is the highest,while that in the middle of tree-shrub-grassland and tree-grassland is the lowest;when the wind is easterly,the temperature of the north-south-trending greenway is higher than that of the eastwest-trending greenway.The wind speed and direction have a direct impact on the internal temperature of the site.For paving,the heating and humidity reducing ability of asphalt is better than that of concrete and wood pavement;for structures,the wall has a weak influence on the wind speed of greenways at different distances.(4)On the basis of field measurement,questionnaire investigation and software simulation,the measured area B is selected for transformation design,and its plants,water bodies,roads,topography and pavement materials are optimized,and the microclimate before and after the transformation is simulated by ENVI-met software.before and after the transformation,the temperature of the same measuring point in the greenway increases by0.12C-0.42 C,and the humidity increases by 0.1% 2.2%.The wind speed decreased by 0.04ml/ kg and 20 m / s,and the DI value increased by 0.91.The comparison results can verify that the research conclusion is suitable for the transformation and design of landscape elements,and can improve the microclimate environment of Zijinshan greenway in winter.Aiming at the design strategy,it is mainly through changing the selection and combination of elements to achieve the purpose of heating up,reducing humidity,avoiding wind and so on.Finally,the scheme is designed for the different landscape nodes of the greenway,and the design strategy for the landscape design elements is put forward. |
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