Spatio-temporal Pattern Evolution Of Urban Agglomerations In The Middle Reaches Of The Yangtze River Based On Nighttime Light Remote Sensing

In April 2015,with the approval of the “Development planning of Urban Agglomeration in the middle reaches of the Yangtze River”,the development and construction of the middle reaches of the Yangtze River(MRYR)has become a national strategy,an important supporting force for the rise of Central China,and an important engine for promoting economic development in the central region.As an emerging economic growth pole,understanding of the temporal and spatial pattern of urban agglomeration in the MRYR has great practical significance for regional economic development.The emergence of nighttime light remote sensing provides an effective method for regional economic development research in large-scale space-time.This research first reviews the research on cities,urban agglomerations and other fields based on nighttime lighting images,and makes a summary;Secondly,combined with the theory of city size distribution,landscape pattern analysis and urban growth model theory to analyze the city size distribution of the MRYR and the sub-city groups.Understand the regional development of the MRYR,the balance of resource distribution and the evolution of urban patches and the changes in urban growth patterns.And then compare the consistency and difference of sub-city groups in the above three aspects,analyze the growth patterns of different cities.This research explores the spatio-temporal pattern evolution of the MRYR in 2012-2018 according to the above aspects and propose rationalization suggestions for the better development of the MRYR.The conclusions of the research indicate that the city size distribution of the MRYR tends to be concentrated and the regional development is uncoordinated;There is not a typical first-distribution distribution structure of the MRYR.Wuhan is the first city of the agglomeration,its first city role was weakened by the development of the second city,Changsha;the lack of large cities in urban agglomerations makes the overall competitiveness of urban agglomerations slightly insufficient;the city size distribution of each sub-group shows a typical first-distribution structure.Wuhan,Changsha and Nanchang are core cities with significant first role,and the city size distribution of three sub-groups tend to be concentrated.From 2012 to 2018,the urban area has expanded significantly.For the urban agglomerations in the MRYR and the sub-city groups,the differences between cities and towns have increased;There are certain differences in urban growth patterns.The trend of the expansion index of the MRYR and the sub-city groups are roughly the same,while the intensification index shows different trend characteristics.Spatial expansion is dominated by adjacent expansion,and each city also exhibits different levels of expansion and intensification;Most cities are in a low level of expansion and medium level of intensification,and there is no obvious way to focus on spatial expansion.While the core city Wuhan has expanded its existing builtup areas,it also pays more attention to the development of new towns;Nanchang focuses more on the expansion of existing built-up areas,and the development intensity of emerging cities is week.Two expansion ways intensities of Changsha are more balanced with no obvious emphasis.Through the analysis and summary of the above conclusions,the following suggestions are given: Improve the economic strength of the central city and enhance the role of radiation to promote the economic development of the central city and surrounding areas;Strengthen the development of small and medium-sized cities,narrow the city size of them and improve the core competitiveness of the MRYR to promote the coordinated development of the region;Each sub-city group also needs to cooperate with the overall development planning and resource allocation of the MRYR,consistent with the overall development to jointly promote the economic growth of the region.