Identifying Suburbs And Analyzing Their Effects On Surface Urban Heat Island Intensity In China Based On Nighttime Light Remote Sensing Data

China’s rapid urbanization has posed threats to the ecosystem and climate around cities,of which the surface urban heat island effect(SUHI)has long been of interest to scholars and urban planners due to its prominent effect on human production and life.An important parameter in the study of the SUHI,which is defined as a higher temperature in urban area than in nearby suburban area,is the surface urban heat island intensity(SUHII).However,the traditional methods for calculating SUHII makes it difficult to reflect suburban structural differences and suffer from unstable results.Although the temperature dichotomy method can compensate for these shortcomings to some extent,the method requires defining reasonable and accurate suburban boundaries.However,the existing studies have defined suburban boundaries in simple terms,leading to an over/underestimation the SUHII.In addition,there is no publicly available Chinese suburban dataset as auxiliary to calculate/validate the SUHII.Suburban areas,as fronts of urban expansion and key areas of rural urbanization,have the potential to change the intensity and process of the heat island cycle through changes in their natural and socioeconomic attributes.To date,no clear studies have been conducted to show the effect of the natural and socioeconomic attributes of suburban areas on SUHII.Based on this context,the extent of suburban areas in China were identified and validated first in this study using the new generation of nighttime light data,Suomi National Polar–Orbiting Partnership-Visible Infrared Imaging Radiometer Suite(SNPP–VIIRS).Then the SUHII index was constructed based on the extent of suburban areas.Finally,the effects of suburban greening and suburbanisation on SUHII were analysed from the perspective of the natural and socioeconomic attributes of suburban areas,respectively.The main findings of the study are as follows.(1)Accuracy verification results show that suburb identification based on SNPP–VIIRS data can identify more details and more accurate than the existing urban area data and Defense Meteorological Satellite Program’s Operational Linescan System(DMSPOLS)data.Compared with traditional mutation detection methods,the proposed method has the advantages of being fast,efficient,and less subjective.Furthermore,we found that China’s suburban areas present a fluctuation-growth trend,with the proportions increasing from 0.6% to 1.3% in the period 2012–2020.China’s suburban areas development was mainly driven by the development of population density,GDP,and road network.Our study provides an innovative way to conduct a rapid,efficient,and largescale and accurate suburban areas identification over a long time series,which can provide reference for formulating policies to alleviate human-land conflicts,social tensions and ecological damage caused by provide reference for formulating policies to alleviate human-land conflicts,social tensions and ecological damage caused by unclear suburban boundaries.The findings also contribute to facilitate the study of socioenvironmental issues in the urbanization process.The annual series(2012–2020)of suburban areas in China are available free of charge at https://doi.org/10.7910/DVN/M5EED5.(2)The SUHII trend in Chinse cities is generally increasing both annually and seasonally(except in winter)from 2012 to 2020.During the summer daytime,the number of cities with the increasing and decreasing trend in SUHII is the highest,and during the winter daytime,the number is the lowest.Suburban areas in China trended greener,where greener suburban areas resulted in 53.7% and 68.7% increases in SUHII during the day and night,respectively,mainly in mega-cities,large cities and medium-sized cities.Suburbanization levels trended downwards,with decreasing suburbanization levels leading to increases in SUHII of 51.7% and 56.7% during the day and night respectively,mainly in megacities.Sensitivity tests indicated the findings were robust during the daytime,whereas the relationship between suburban greening and SUHII at nighttime was sensitive to the suburban extent.Our study suggests that strengthening urban greening and improving suburbanization levels are important to reduce the urban heat island in cases of suburban greening and suburbanization decreasing.A new perspective on SUHII studies was provided in this study,which provides evidence for the development of a coordinated suburban and urban development strategy.