Optimizing Urban Thermal Environment:Based On Spatial And Temporal Characteristics

The Urban Heat Island(UHI)phenomenon is constantly exacerbating in increasing number of cities because of intensifying urbanization.The relevant issues,such as Extreme heat event,Air Pollution and so forth,are threatening human health.To optimize urban living environment and improve human well-being,moderating urban thermal environment is a hot issue concerned by more and more cities.Urban planning as the main guidance of urban construction,management and development,improving the living environment is one of its responsibility.However,real applications of mitigating UHI from the view of urban planning are still very rare.Based upon these background,this study aims to investigate the impacts of planning indicators on urban thermal environment,then give some practical approaches for UHI mitigation.Specifically,taking Wuhan as an example,this study employed GIS(Geographic Information System)techniques,RS(Remote Sensing)techniques and statistical methods to explore the relationships between planning indicators and temperature,and determine the temporal-spatial characteristics of the relationships,so as to propose some mitigation strategies for UHI mitigation.The planning indicators mainly refers to urban buildings and urban vegetation,including Building Density,Building Height,local Moran's I of Buildings,Floor Area Ratio,Normalized Difference Vegetation Index.The objectives of this study are:1)explore the dynamic relationships of planning indicators and temperature at varying geographic scales,so as to determine the optimal study scale,namely the proper calculation scale for these indicators;2)examine how the relationships change with time;3)propose strategies for UHI mitigation based on the thoughts of zoning and priority,and the results of the scaling effects and temporal patterns.Results of this study include:1)Urban buildings have positive relationship with temperature,and 200m is the optimal scale for studying "building-temperature”relationships;urban vegetation has negative relationship with temperature,and the proper scale for "vegetation-temperature" is 1000m.2)Urban buildings and vegetation only significantly impact nighttime temperature,their impacts on daytime temperature are negligible;comparing with a cool day,the impacts of buildings and vegetation are more significant on a hot day;adjusting planning indicators can achieve best cooling effects during 0:00?1:00.3)Optimizing the spatial configuration of urban buildings is an effective way for UHI mitigation,especially on a hot day.4)The thoughts of zoning and priority is conducive for systematic implementation of strategies,and the mitigation approaches are more feasible based on the spatial-temporal patterns,but the strategies for specific area should take the current construction situation into consideration.This study is conducive to fill the gap between planners and geographers,climatologists,or environmentalists,and help urban planners or decision-makers better understand urban environment issues.The framework proposed for UHI mitigation is feasible and specific,which can potentially improve the mitigation effectiveness and push our step further toward sustainable development.