Spatio-temporal characteristics of aerosol optical depth and their relationship with urbanization over China\u27s land in nearly a decade

Urbanization has been the major cause of increasing aerosol in the environment. Aerosol had great influence on human health and ecological environment, and aerosol optical depth (AOD) was a key indicator of aerosol. In this paper, the impact of urbanization on AOD in China during January 2008 to December 2017 is studied using MODIS AOD (MYD03_M3 remote sensing images) data and DMSP/OLS night-time light data. And the differences of AOD concentration inside and outside the area of three districts and ten groups were especially compared.The results showed that, the overall spatial characteristics of AOD in China exhibited a significant difference on the two sides of Hu Line . High AOD values can be found in Beijing-Tianjin-Hebei, Yangtze River Delta and Central China, while the western region (except the Tarim Basin) has much lower AOD values. During 2008-2017, the average annual AOD value in China was 0.332, while in spring, summer autumn and winter, the average annual AOD value were 0.434, 0.344, 0.248, 0.304, respectively. During 2008-2012, the growth rate of AOD in China was -0.033, while it changes to -0.149 during 2013-2017. The AOD growth rate in spring and winter were -0.318,-0.130, respectively, and the fall was larger in spring. The spatial-temporal characteristics of night-time light in China\u27s land also conformed to the Hu Line , and it was roughly the same as the spatial-temporal characteristics of AOD. In the year of 2008-2013, the eastern coast of China was much brightly than the western interior, and densely populated provinces and cities increased significantly, and the range of brightness increased to a great extent, showing the process of urbanization in China. The AOD values and nighttime light data were highly correlated, and the statistical relationship between them was found by the least square method. The power function\u27s R2 value were 0.8036, 0.8263, 0.7701, 0.8277 and 0.8331 respectively. The process of urbanization had a significant impact on the spatio-temporal characteristics of AOD, which caused the complexity of the aerosol and atmosphere environment