Spatio-temporal variations and trends of MODIS C6.1 Dark Target and Deep Blue merged aerosol optical depth over China during 2000–2017

Abstract

The variations and trends of the AOD (aerosol optical depth, at 550 nm) from 2000 to 2017 in mainland China were analyzed in this paper with monthly, seasonal, and yearly mean data, derived from the NASA combined MODIS Dark Target and Deep Blue AOD retrievals. Particularly, the distribution and variation of AOD over the desert region of the southern Xinjiang basin which is one of the major Asian dust sources was described. To investigate the seasonal and yearly variation trends of the AOD over China, the linear trend was analyzed for each point during the 18 years. The correlations between AOD and terrain, Gross Domestic Product and Population Density were also analyzed. The results were as follows. (1) In China, the all-year high value (τMODIS>0.50) of the AOD occurred in the Sichuan basin, the Two Lakes Plain, North China, the Yangtze River Delta, the Pearl River Delta, the Guangzhong Plain, and the Jingjinji Metropolitan Region. In particular, the southern Xinjiang basin is not the high value center. While the all-year low value (τMODIS<0.20) of the AOD occurred in Northwest Sichuan, Southeast Xizang, the Qinghai-Xizang Plateau (Tibetan Plateau), Northern Xinjiang, Shanxi, Gansu, and Inner Mongolia. (2) The AOD over China varied with years from 2000 to 2017, which increased in the previous decade but gradually decreased from 2011. (3) The AOD changed more significantly with the seasons, with higher AOD in spring and summer, and lower in autumn and winter. (4) The AOD was negatively associated with Digital Elevation Model, with a Spearman correlation coefficient of −0.733, which was positively associated with Gross Domestic Product and Population Density, with Spearman correlation coefficients of 0.698 and 0.688.