Research On The Spatial And Temporal Characteristics And Planning Countermeasures Of UHI In The Yangtze River Delta Urban Agglomeration Based On LCZ

Developing and expanding urban agglomerations and metropolitan areas is an important task of the 14 th Five-Year Plan.However,the rapid expansion of urban agglomerations has a potential negative impact on the realization of China’s 2030 "carbon peak" goal.In the context of global warming and urbanization,the urban heat island(UHI)effect of urban agglomerations is inevitable,and how to coordinate urban development and ecological and environmental risks at the planning level is a practical problem that needs to be solved urgently.Taking the Yangtze River Delta(YRD)urban agglomeration as an example,this paper uses GIS technology to extract urban surface parameters based on the Google Earth Engine(GEE)platform and the latest remote sensing data,and combines human subjective influence cognitive experiments and supervised machine learning to draw the distribution map of local climate zones(LCZ)in the main urban areas of the main cities of the YRD urban agglomeration.The spatiotemporal characteristics of land surface temperature(LST)in the YRD urban agglomeration from 2012 to 2021 were analyzed,the main cities were further divided into two levels,the spatiotemporal differentiation of LST and heat island intensity and the main influencing factors between LCZ classes and intra-class were analyzed,and horizontal and longitudinal comparisons of the two levels of cities were carried out to achieve in-depth research on the UHI effect of urban agglomerations.The main characteristics of UHI effect in the YRD urban agglomeration were summarized,and scientific and specific planning strategies were put forward from the perspective of urban planning and construction.The main conclusions are as follows:(1)The YRD urban agglomeration accounts for the highest proportion of open high-rise buildings(LCZ4)and large low-rise buildings(LCZ8),and the proportion of natural surface low vegetation(LCZD)in secondary cities is the highest.The gap between the building surface zoning and the natural surface zoning in the main urban area of Shanghai in the eastern part of the urban agglomeration is the largest,and the gap between Wuhu City in the north-central part is the smallest.(2)From 2012 to 2021,the maximum value of summer daytime LST in the YRD urban agglomeration decreased slightly,the summer nighttime LST high temperature area showed a trend of shrinking,and the maximum value of winter LST increased.In 2021,the highest temperature of LST in the YRD city cluster appeared in first-class cities.Large low-rise buildings(LCZ8),heavy industrial areas(LCZ10),and hardened ground(LCZE)have the highest temperatures,and open low-rise buildings(LCZ6),water(LCZG)and dense trees(LCZA)have the lowest temperatures.The regularity of LST distribution in compact low-rise buildings(LCZ2 and LCZ3)and sparse buildings(LCZ9)is strong.(3)The heat island intensity of large low-rise buildings(LCZ8),heavy industrial areas(LCZ10)and hardened ground(LCZE)in the YRD urban agglomeration is the highest,and dense trees(LCZA)and water area(LCZG)are the lowest.The intensity characteristics of heat islands within trees and vegetation(LCZA,LCZB and LCZD)classes were similar.(4)The impervious surface ratio and night light index have the strongest warming effect on the YRD urban agglomeration,and the permeable surface ratio has the strongest cooling effect.Moreover,there are many special influencing factors of building surface LCZ.(5)According to the research results,the following overall mitigation strategies are proposed: Systematic mitigation of UHI in urban agglomerations;Transforming the values of urban development;Increase the coverage of blue-green spaces;Pay attention to the ratio and matching of vegetation.Specific mitigation measures are proposed in view of the individual characteristics of key districts of major cities.