Research on air pollution in Beijing and its surroundings with MODIS aerosol products

In this paper the MODIS Level2 aerosol products over Beijing are validated by comparison with the observations from sun-photometer at Peking University (PKU) at first. The MODIS aerosol optical depths (AOD) also correlates well with the averaged mass concentration of respirable suspended particulate (RSP, PM10) calculated from released API data. The relations between the visibilities and the AOD values with distinct aerosol scale heights in different seasons are estimated. The cases described by the AOD distributions over Beijing and its surroundings show some dramatic processes. The analysis assisted by the relevant changes of meteorological variables can help us find the corresponding answer to each air pollution episodes. The seasonal AOD variations in Beijing show the mean AOD value is highest in summer, and has a decreasing trend from summer to autumn, and then to winter. It has a rapid increasing from winter to spring due to spring dust in North China. Finally we gain the seasonal mean visibility distributions of Beijing and its surroundings. The mean air quality gets worst in winter due to increased pollutant source in winter and bad dispersion conditions, and becomes the best in spring because strong wind provides fast dispersion in spite of occasional dust weathers. The results indicate the air pollution in Beijing urban area is both contributed by local urban emission and regional transport. Remote sensing from space has provided us a new view to study the air pollution.