Evaluate Relationship Between Urban Forms And Carbon Emission In China At The Prefecture-level City Scale Based On Nighttime Light Data

Global warming has become an indisputable fact.The massive emissions of carbon dioxide and other greenhouse gases have exacerbated this process,and urban built-up areas as the center of human production activities have contributed more than 70% of global carbon dioxide emissions.Studies have shown that urban form affects the spatial organization and arrangement of urban infrastructure,and have an important impact on carbon dioxide emissions.In the context of rapid urbanization in China,the issue of carbon dioxide emissions has attracted widespread attention.Effectively assessing the impact of urban forms on carbon dioxide emissions can provide a scientific basis for the exploration of low-carbon city models and sustainable social and economic development.Therefore,the use of multi-source remote sensing data to measure urban form and establish a correlation model between urban form and carbon dioxide emissions is a hot topic in the context of rapid urbanization.Because of its all-weather,all day and night characteristics,remote sensing data can quickly and accurately extract information such as the shape of urban built-up areas.At present,there have many studies based on remote sensing images of different data sources and different spectral ranges,producing global to regional data sets of urban built-up areas.Nighttime light data can record the lights produced by humans at night,and it has been proved that it can be used to quickly extract information about urban built-up areas.However,at present,the use of nighttime lights data to carry out research on the relationship between China's urban form and carbon dioxide emissions is mostly limited to individual urban agglomerations or parts of cities.After analyzed and summarized the existing research,this study based on nighttime lighting data and normalized vegetation index and other remote sensing product data,to obtain the urban form of China 's prefecture-level city scale under long time series,and uses geographic weighted regression analysis to evaluate the relationship between urban form and carbon dioxide emissions.Then,explored the effect of different urban form factors on carbon dioxide emissions.The main contents of this study are as follows:1)Combine the NPP-VIIRS monthly composite nighttime light data and normalized vegetation data,use the remote sensing image classification method based on threshold segmentation to extract China's urban built-up areas from 2012 to 2015.The results were corrected with the existing urban built-up area data extracted from DMSP-OLS stable night light data from 2000 to 2012.2)Based on the extraction results of urban built-up areas,the landscape morphology index algorithm is used to measure the city morphology of prefecture-level cities in China.Based on previous research experience,the morphological index representing different aspects of urban morphology is selected,including city size,connectivity,agglomeration,and dispersion.3)Based on the spatial autocorrelation test of the urban form index,the classical geographic weighted regression analysis method is used to analyze the correlation between the urban form index and carbon dioxide emissions of China's prefecture-level cities under long time series.The research results show that the urban built-up area extracted based on NPPVIIRS night light data and the previous results based on the DMSP-OLS stable night light data have higher spatial and temporal continuity and can be used as a consistent data set.In addition,the results found that for China's small and medium-sized cities that are still in the process of rapid urbanization,increasing the compactness of the urban form is favorable to improving urban efficiency,thereby reducing carbon dioxide emissions.The higher complexity and irregularity of the urban form will also promote carbon dioxide emissions,especially in prefecture-level cities in eastern China and most parts of northeast China.With the further development of China's urbanization process,the complexity of urban form has reduced the promotion of carbon dioxide emissions.The degree of aggregation of urban forms varies with the size of the city and has a different effect on carbon emissions.The accumulation of small and medium-sized cities is conducive to reducing carbon dioxide emissions.The high concentration of large and ultra-large cities will reduce the efficiency of urban carbon dioxide emissions.In addition,the results of the study show that the improvement of connectivity and regularity of urban forms is conducive to the development of public transportation,reducing the pressure on transportation and logistics,thereby reducing carbon dioxide emissions.The empirical conclusions of this study are of great significance for understanding and exploring the mechanism of China 's prefecture-level city-scale urban forms that affects carbon dioxide emissions and the temporal and spatial differences in its impact mode,which can provide science basis for decision-makers in low-carbon city planning.