Analysis The Spatio-temporal Pattern Evolution Of Urban Heat Island In Chengdu Based On Multi-source Data

The remarkable Urban Heat Island(UHI)effect in Chengdu has seriously affected the urban ecological environment and threatened the health of residents.In order to fully understand the UHI effect of the study area and provide information for the development of mitigation measures,this paper focuses on UHI research.At present,the analysis method of UHI spatial pattern evolution of long time series,the research content of UHI related factors and the type of research data are relatively simple,and it's hard to analyze the spatial distribution and expansion trend of UHI.In view of the above problems,this paper built an index system that adapted to the research area based on multi-source remote sensing data,and combined statistical data to comprehensively analyze the temporal and spatial distribution characteristics and influencing factors of the regional UHI.The following work was carried out:(1)Using Landsat7 ETM+ and Landsat8 OLI/TIRS remote sensing images as data sources,the radiation temperature equation was used to invert the surface temperature of the study area from 2013 to 2018,and the UHI region was identified by normalized synergistic mean-standard deviation.(2)Constructed the UHI comprehensive research index system,including Compactness Index(CI),Developmental Strength Index(DSI),Extension Speed Index(ESI)and Relative Strength Index(RSI).Used the center of gravity shift of the UHI region to characterize the UHI migration footprint for five consecutive years.(3)Using night-time remote sensing data,statistical data,POI data and policy planning data,the factors affecting the spatial and temporal distribution of UHI in the study area were explored from the perspective of natural geography and economic geography.(4)Constructed UHI panoramic conversion map.And based on the spatial relationship between UHI distribution and urban architectural pattern,the multi-angle and multi-factor research results were used to predict the UHI of the study area,and propose corresponding prevention measures.The results show that:(1)The spatial and temporal evolution of UHI in the study area in 2013-2018 showed a downward trend as a whole,with short-term fluctuations.From a global perspective,the UHI effect pattern in the study area has changed from agglomeration and bias to fragmentation and equalization.The center of gravity has migrated from northwest to southeast,and the expansion speed has slowed down.From a local point of view,the centralized spatial and temporal characteristics of the UHI in the study area are prominent,showing a ring-shaped radial attenuation distribution pattern;the UHI development intensity of the “one circle” urban area is significantly higher than that of the “two-circle” urban area,especially in Wuhou District and Chenghua District.In addition,the value of DSI in the Longquanyi District and Shuangliu District increased sharply in 2018.(2)From the perspective of natural geography,vegetation and water have an inhibitory effect on UHI,while impervious surfaces such as buildings and roads can aggravate the UHI effect.From the economic geography,the development intensity of UHI effect is significantly positively correlated with residents' behavior,and socio-economic industrial structure also have a significant driving effect on the temporal and spatial pattern of UHI.(3)Research area thermal field distribution has high coupling with urban building pattern and road network distribution.According to UHI panoramic conversion map,UHI phenomenon in research area is mainly distributed in downtown core business district,high-density residential area,economic development area and new Industrial Park.(4)Comprehensive multi-angle analysis results,this paper proposes to further optimize the urban spatial structure of the stable heat island area and transition heat island area,and use the water system and shelterbelt to construct urban green corridors to establish a complete green ecological network.The climate change adaptation strategies of urban environment requires sufficient knowledge system,the research results of this topic are expected to provide reference for urban planners to organize more resistant and flexible urban forms.