The Research On Microclimate Effect Of The Landscape Spatial Structure On Waterfront Green Space

With the development of urbanization,the urban construction rate continues to increase,and the contradiction between man and land is gradually intensifying.Eco-environmental issues have become the main issues affecting human settlements and urban development.In order to solve climatic and environmental problems such as urban heat islands,climate-adaptive urban planning has become one of the focuses of urban research.A large number of studies have proved that waterfront green spaces can improve the urban climate.Reasonable landscape space structure design can guide the improvement of the waterfront green space microclimate,and is of great significance for improving the urban thermal environment,wind environment and thermal comfortIn this research,the definition method of green space spatial form in the research of landscape spatial pattern is applied to the identification of the spatial structure of waterfront green landscape at the site scale.Aiming at the spatial form and surface coverage of waterfront green space,a landscape spatial structure index system for waterfront green space for microclimate research was established.The spatial form includes 9 indicators in three dimensions:flat form:patch area(A),edge density(ED),patch shape index(PSI),spatial relationship:offshore distance,angle to shore,corridor Height-to-width ratio(H/W),vegetation morphology:vegetation height(H),leaf area index(LAI),sky view factor(SVF);surface cover includes two indicators:grass coverage and surface permeability.Based on the climatic conditions in Shanghai and the environmental conditions of the on-site waterfront green space,waterfront green space models with different values of various indicators were established,and microclimate simulations were conducted through ENVI-met to analyze and summarize the microclimate impact of each indicator.Finally,based on the above analysis,the landscape space structure optimization research of the on-site waterfront green space case is carried out.The key index values that affect the overall and local microclimate effects of the green space and the reasonable landscape spatial structure configuration method are summarized.Provide theoretical basisThe results show that:(1)Rivers have the effects of cooling,humidifying,increasing wind speed,and increasing thermal comfort in vegetation,bare land,and river areas,and the effect intensity increases from the shore to the inland;The micro-climate effect is obvious,with strong effects of cooling,humidification,wind speed and thermal comfort.(2)For the flat form of vegetation,green areas with large area,small edge density,and large patch shape index have the best improvement effect on the overall microclimate,which can effectively reduce temperature and humidity,and improve thermal comfort.When the patch area is 2400 m2 and the edge density is 0.75,the overall wind speed of the green area is the highest.Green areas with large area,small edge density,and patch shape index of 1 can concentrate and efficiently improve the thermal environment and thermal comfort on the northwest side of the vegetation,and the wind speed around the southwest is accelerated.Green areas with high patch shape index and high edge density help to expand the thermal environment improvement range,the wind speed around the vegetation is reduced,and the high comfort zone is widely distributed.(3)For the spatial relationship of vegetation groups,reducing the offshore distance,keeping the angle to the shore at 135 °,and maintaining the height-to-width ratio at 1,can improve the greenfield microclimate effect.The increase of the distance from the shore helps the cooling and humidification south of the vegetation area and the improvement of thermal comfort.The increase of the height-to-width ratio of the corridor makes the microclimate at the corridor and the surrounding vegetation tend to be consistent.(4)For the vegetation form of green space,the vegetation height is 12m,the greater the LAI and the smaller the SVF,the better the overall microclimate effect of the green space.The microclimate effect is best in the green space corridor with a vegetation height of 8m.The temperature of the corridor with a vegetation height of 16m is higher than that of the green space with a vegetation height of 8m and 12m.(5)For the surface coverage of green land,increasing the surface permeability can help improve the microclimate,and the impact of grassland coverage on air temperature is weaker than the surface permeability.Increased surface water permeability contributes to the improvement of the thermal environment,but it has a negative impact on thermal comfort and little impact on the wind environment.(6)The climate simulation results after the improvement of the spatial structure of the on-site waterfront green space landscape show that vegetation morphology is the key to cooling and humidification.The increase in vegetation effectively improves the thermal environment.The 12m high vegetation compared to 8m vegetation increases The promoting effect of moisture is more obvious.Based on the improvement of the thermal environment,the control of the relationship between the planar shape and space of the vegetation improves the ventilation efficiency of the green space and promotes the improvement of the thermal comfort of the green space.Waterfront green spaces have better microclimate improvement benefits than ordinary green spaces or rivers.The effects of waterfront green spaces and rivers such as cooling,humidification,wind speed,and thermal comfort are all synergistic and mutually reinforcing.