The global spatial-temporal distribution and EOF analysis of AOD based on MODIS data during 2003–2021

Abstract

The long-term global distribution study of Aerosol Optical Depth (AOD) has great significance for air pollution control, forest fire prevention and climate studies. The global spatial-temporal distribution and variation of the AOD at 550 nm are analyzed using AOD550 product of Modis/Aqua during 2003–2021. The AOD550 is also studied by Empirical Orthogonal Function (EOF) analysis method. The results show that the distribution of AOD550 has obvious regional and seasonal characteristics, and the interannual variation is distinct. The AOD550 distribution with latitude/longitude is closely related to the distribution of population and aerosol natural source. The high-AOD550 areas are mainly distributed in eastern Asia, southeast Asia, south Asia, the Middle East, northwestern Africa, central and western Africa, western waters of Africa and the Amazon region of South America; The AOD550 seasonal distribution results are JJA > MAM > DJF > SON over globe, SON > DJF > (MAM ≈ JJA) over the southern hemisphere, and MAM > JJA > DJF > SON over the northern hemisphere, respectively. Moreover, the seasonal distribution characteristics varies in different regions especially over ocean and land. The results of interannual variation show an upward trend during 2005–2011, and fluctuates during 2012–2020. The annual mean AOD550 over the northern hemisphere (0.187–0.207) is significantly higher than that of southern hemisphere (0.110–0.135), while the latter shows an increasing trend (0.0009/year). The EOF analysis results demonstrate the complexity of the AOD550 global distribution. The annual mean results show the change trends of aerosols in different regions and find some special aerosol events. While the monthly mean results show that aerosols over ocean are mostly dominated by land sources (dust and biomass burning sources), and the ocean transport pattern presents an annual cycle.