Spatial Pattern Characteristics Of Urban Agglomerations In The Middle Reaches Of The Yangtze River Under The Background Of New Urbanization

In this study,we obtained the total intensity,average intensity,and lit surface area of the urban agglomerations in the middle reaches of the Yangtze River in China using the NPP-VIIRS night-time light composite data from 2012-2017.Next,using methods such as kernel density analysis,standard deviation ellipse,rank clock theory,and location coefficients,we carried out spatial and temporal analyses of the above night-time light indices to examine the evolutionary characteristics of urban agglomerations' spatial pattern in the middle reaches of the Yangtze River from 2012 to 2017.The main contents are as follows.(1)Spatio-temporal evolution characteristics of urban agglomeration scale in the middle reaches of the Yangtze River:In the first section of Chapter III of this paper,the spatial-temporal trend of urban agglomeration scale and the change of urban agglomeration scale are analyzed by using the method of rank-scale rule,rank clock system and nuclear density analysis.The study finds that the overall urban scale intensity of urban agglomeration is constantly increasing,the urbanization speed is accelerating,and the expansion of urban scale is mainly outward expansion.With Wuhan,Changsha and Nanchang as the core of the triangle,other cities develop in a decentralized way.Medium-sized cities are facing fierce competition and frequent fluctuations in urban rank.The scale of Changde,Jiujiang,Yichang and Xiangyang cities is closely following that of Wuhan,Changsha and Nanchang.(2)Urban spatial development patterns of urban agglomerations in the middle reaches of the Yangtze River:In the second section on Chapter III of this paper,research methods are as follows:Standard deviation ellipse analysis,cold-hot spot analysis,etc.Based on the above research methods,this paper analyses the evolution trend of spatial distribution of urban development and the cold and hot zones of urban agglomeration spatial development.The study finds that the spatial characteristics of urban agglomeration scale show a spatial pattern from north to south,as well as the characteristics of shrinking first and then expanding.The main driving force for the spatial evolution of urban agglomeration in the middle reaches of the Yangtze River is from north to south.From the perspective of the development of sub-urban agglomeration,the city scale of Hunan sub-urban agglomeration has the greatest change.For example,Changde City is a hot city in the development of urban agglomeration.Wuhan,the central city of Hubei sub-group,has a strong core force,so the movement of urban scale center has little change.(3)Level of spatial agglomeration of urban agglomerations in the middle reaches of the Yangtze River:The phenomenon of spatial agglomeration of urban agglomerations is declining and urban development is decentralized.From the perspective of the development of sub-urban agglomeration,since 2012,the spatial agglomeration of Jiangxi sub-group is relatively stable,while the spatial agglomeration level of Hunan sub-group and Hubei sub-group is declining.In urban agglomeration,there are new central cities besides central cities,which promote the evolution of agglomeration spatial structure towards multi-center structure.(4)In order to test the accuracy and comprehensiveness of NPP-VIIRS night light remote sensing image data in the evolution of urban spatial pattern in the middle reaches of the Yangtze River,the fifth chapter of this paper conducts an index verification study on night light remote sensing image data and socio-economic statistical data.It is found that there is a significant correlation between the light indicators and socio-economic statistical indicators.The results of the two data are highly consistent with the results of the urban spatial development pattern of the urban agglomeration.To sum up,the spatial pattern of the urban agglomeration in the middle reaches of the Yangtze River is multi-center structure,and the three provincial capitals play a major role in radiation and attraction.At the same time,its multi-center trend is obvious.Yijingjing,Changde,Yueyang and Jiujiang are developing rapidly.They are the core development forces in the east,middle,West and north of the urban agglomeration.They form a "central and peripheral strong" spatial structure with Wuhan,Changsha and Nanchang.In addition,the study found that the urban agglomeration in the process of new urbanization problems,including urban agglomeration spatial development is not balanced,spatial differences are large and so on.The unreasonable spatial structure is not conducive to the rapid flow of elements,so we should further improve the quality of new urbanization of urban agglomerations in the middle reaches of the Yangtze River and optimize the spatial structure of urban agglomerations.