| As the country and regional productivity continue to develop rapidly,industrial structure undergoes transformation,and scientific and technological progress advances,urbanization expansion has become one of the most significant human social changes in the world.However,rapid urban expansion and frequent human activities have put enormous pressure on the ecological environment,and environmental degradation in turn hinders high-quality urban development.The level of urban development and the quality of the ecological environment affect each other and are constrained by each other.Therefore,revealing the coupling mechanism and evolutionary mode of the two is not only a practical necessity to promote regional coordination and cooperation,but also an inevitable requirement to scientifically promote modern urban development.China has entered the stage of high-quality economic development,and urban clusters and metropolitan areas have become important carriers of urbanization development.Among them,the Chengdu-Chongqing Economic Circle is geographically advantageous and is a strategic location for the "Belt and Road" and the Yangtze River Economic Belt.The quality and sustainability of its urban cluster development have been widely concerned domestically and internationally.In recent years,remote sensing satellite dynamic monitoring technology has progressed significantly,boasting features such as broad detection range,strong real-time performance,and rich data types.With good timeliness and cost-effectiveness,it has become a mainstream tool for studying and managing the Earth’s natural resources and environment,and is widely utilized in numerous fields such as agriculture,forestry,geology,oceanography,environmental protection,and meteorology.It has unique advantages,especially in urban land monitoring and observing human social activities.In the field of remote sensing,urban ecological indicators derived from remote sensing data support dynamic monitoring and rapid assessment of urban ecological conditions.Additionally,nighttime lighting data can provide direct insight into the intensity of human activity and the process of urbanization.This paper focuses on the Chengdu-Chongqing Economic Circle and utilizes the Google Earth Engine cloud computing platform.Firstly,we improve the original remote sensing ecological index by incorporating the thickness of optical aerosols.The rationality of this index is then evaluated through principal component analysis and correlation analysis.Secondly,we analyze the spatial and temporal distribution pattern of urban remote sensing ecological indicators from 2012 to 2021,and employ the Markov transfer matrix to explore the evolution model of ecological environment quality.Furthermore,we calculate the urbanization quality index and comprehensive night light index based on statistical yearbook data and night light data,and evaluate the latter’s rationality using weight analysis and correlation analysis.Based on this,we comprehensively explore the urban development level and its changes in the research area over the past decade from both the pixel and urban scales.In addition,we conduct further discussions on the Sichuan area using rank analysis,primacy analysis,and rank scale analysis to investigate the urban scale system structure of the Chongqing area and the research area.Finally,we propose an improved coupling model that utilizes the coefficient of variation,Gini coefficient,exploratory spatial analysis,and temporal trend analysis model to comprehensively assess changes in coupling coordination in the study area,from three perspectives: spatiotemporal heterogeneity,regional imbalance,and spatiotemporal change trends.To grade the coupling and coordination degree and balance degree of the city,the study used the dual variable natural breakpoint method.Additionally,the 2021 city was used as an example to classify the coupling types and development stages,and to provide suggestions and development strategies for the future sustainable development of the Chengdu-Chongqing Economic Circle.The main conclusions are as follows:(1)The correlation coefficients between different ecological factors of the improved remote sensing ecological index were significantly related at a 1% level.The correlations with NDVI,NDBSI,LST,AOD,and WET were 0.84,-0.82,-0.57,-0.45,and 0.15,respectively.The overall ecological environment quality of the study area reached 0.681,with a distribution pattern of high quality in the mountainous and suburban areas and low quality in the urban areas.The increase in the past ten years was10.9%.The probability of maintaining the same ecological environment quality level remained unchanged was 0.626,and the probability of changes in adjacent levels was0.226.The probability of an upward transition between adjacent levels was 0.362.(2)The compounded night light index and urbanization quality index are significantly correlated at a 1% level,with a coefficient of 0.732,and their data distribution is basically the same.Due to economic and transportation conditions,the distribution of bright spots of nighttime lights is concentrated on transportation hubs and trunk lines,showing a double-peak distribution trend in the "northwest-southeast" direction.Over time,the trend is first decreasing and then increasing,with an increase of 87.5%.This is basically opposite to the net outflow rate of population,with a decreasing amplitude of 44.0%.The results of the comprehensive nighttime light index indicate that medium and above-level cities are concentrated in the central urban areas of Chengdu and Chongqing.With the advancement of the Chengdu-Chongqing integration project,the number of medium and above-level cities has increased from 6to 9,with an increase of 92%.Spatially,it shows a diffusion and upgrading trend from north to south.The ranking of the head and tail cities in the Sichuan and Chongqing areas remains unchanged,while the ranking of the waist cities is fiercely competitive with significant changes.The average top position coverage of two cities in the Sichuan area and four cities is 2.989 and 1.430,respectively,showing an unbalanced development and a single-center structure.The top coverage of cities in the Chongqing area is relatively low,with higher coordination levels,but influenced by the one circle and two wings of planning,the annual average scale structure index is as high as 1.895,and a single-core structure is more significant overall.With the promotion of regional integration policies,the scale structure indexes in the Sichuan,Chongqing,and research areas have decreased by 17.3%,7.5%,and 16.3%,respectively,all evolving towards a multi-center structure.(3)Improved coupling coordination has resulted in an average value of 0.127,which decreases rapidly as the distance from the urban built-up area increases.At the urban scale,the coupling coordination level shows a dumbbell-shaped pattern,with high levels in the east and west and lows in the central part.Due to policy factors,the proportion of medium and high coupling coordination levels increased from 43.5% to67.4% and expanded from north to south.The variation in the degree of coupling coordination is moderately low,with an annual average of 0.391,which shows an N-shaped change over time.The overall level of the Gini coefficient is relatively high,reaching 0.593,and shows M-shaped fluctuations over time.Coupling coordination shows a clustering feature at the 1% significance level,with high-high aggregation,low-high aggregation,and low-low aggregation concentrated in Chongqing,and the spatial center located near the boundary of Beibei District and Bishan District,extending deep into the Chengyu hinterland along the "northeast-southwest" direction.Coupling coordination will continue to increase significantly in the future.In 2021,the coupling types show that the coupling coordination status and internal balance status are mainly in the uncoordinated type and critical type,respectively,with proportions reaching 57% and 52%.Both the Chengdu and Chongqing urban clusters are in the stage of saturated coordinated development,while the central and northeast parts of Chengyu are in the stage of transitional coordinated development.(4)The research area is still in a stage of regional development imbalance and significant urban-rural gap.To address this,we should improve the construction of a three-dimensional transportation system to promote regional interconnectivity.At the same time,we should also advance the differentiated and characteristic construction of large,medium,and small cities,construct a perfect scale gradient of urban areas,and ultimately achieve the integrated development of the Chengdu-Chongqing Economic Circle in the region. |
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