Abstract：Using MODIS 3 km AOD products from satellite Terra and mass concentrations of PM_2.5 in air quality monitoring stations over the mainland China from 2015 to 2016, the AOD and PM_2.5 hourly mass concentration data were matched and the total matching samples were divided into different sets. By comparing the correlation coefficients of the samples in different sets, the temporal and spatial changes of the correlation between AOD and PM_2.5 were analyzed. The results show that the correlation coefficient between AOD and PM2.5 is 0.40 for the overall sample set within two years in China, and the correlation are 0.49, 0.53, 0.48 and 0.36 for the sample sets of spring, summer, autumn and winter in China, respectively. For the 2-year sample set of each of the 1497 sites, the correlation coefficient of 906 sites can pass the significance test of 0.05 level, the maximum value is 0.92, the minimum value is 0.17, and the mean value is 0.44. For 1 497 sites in different seasons, the proportion of sites with significant correlations in spring, summer, autumn and winter are 43.9%, 51.3%, 39.8% and 10.1%, respectively. The number of significant sites in summer is the largest with the largest geographical distribution and the mean of correlation coefficients is high. It is indicated that in China, although the MODIS 3 km AOD can be effectively used to retrieve PM_2.5 hourly mass concentration, the effectiveness of the inversion has obvious time and spatial difference.

Keywords：aerosol optical depth; particulate matter; hourly mass concentration; correlation