Research On The Temporal And Spatial Changes Of Urban Form And Thermal Environment Under The Background Of Urban Expansion

The development of urbanization is accelerating,making urban heat islands and other complex urban problems plaguing the healthy development of cities.How to optimize and improve the urban thermal environment has become a hot issue that cities attach importance to.As an urban entity,the urban spatial form shows different morphological types and specific physical and spatial forms of layout,which significantly affects the degree of heat accumulation,which in turn leads to the spatial and temporal differentiation of urban heat island characteristics.Therefore,optimizing urban spatial form is considered to alleviate the urban heat island effect.effective means.Based on the above research background,using remote sensing dynamic monitoring to obtain the advantages of convenient and revisitable observations,from long-term series,from different spatial scales(city/block),the temporal and spatial evolution rules of urban morphology and thermal environment,as well as the classification of urban morphology,morphological indicators By discussing the mechanism of action of thermal environment,we can grasp the development of urban space and the change of heat island,reasonably predict the expansion trend of urban heat island,and in-depth exploration of the local scale can provide more detailed regional dynamic changes of thermal environment.It can be used as the basic data for the research on the history of contemporary urban development in Chengdu and the history of urban surface heat island changes.Taking the central urban area of Chengdu as the research scope.First,the Landsat5 and Landsat8 satellite images of Chengdu in 1988,2000,2009,2013,and 2018 were used as the main data source for the study.The normalized building index(NDBI)was used to extract the built-up area,and by introducing indicators such as expansion speed,expansion intensity,and expansion direction,the directional characteristics and quantitative characteristics of urban expansion in the central urban area of Chengdu were studied;the Local Climate Zones theory was introduced(LCZ),through the World Urban Database and Portal Tool(WUDAPT)method to build a multi-year local climate zone(LCZ)map,realize the extraction of urban form classification and building density,water permeability form index information,use spatial overlay analysis and conversion Matrix analysis and other methods,combined with urban development policies and overall planning,focus on exploring the evolution laws and characteristics of different urban morphological categories and morphological indicators within the temporal and spatial scope of the above five years.Secondly,by using surface temperature inversion method,heat island intensity calculation,transformation matrix analysis and other methods,the evolution law and characteristics of nighttime and daytime surface heat island in the study area in the abovementioned space-time range are studied.Comparing and analyzing the distribution map of Chengdu’s surface heat island with the urban built-up area expansion map and the urban form classification distribution map,it is concluded that the three have close spatial connections and are greatly affected by urban development policies and overall planning;Buffer analysis,overlay analysis and other methods explore the specific contrasting characteristics of thermal environment and urban form.Finally,the above results and characteristics of the results are applied to the field of urban planning,and the corresponding strategic inspirations are put forward from two levels of urban spatial layout(macro-middle-micro)and urban layout scale.