Cross-analysis of fine particulate matter's values, transport and aerosol vertical structures in three severe polluted cities of China

The cross-analysis among observed PM_2.5, air mass backword trajectory and aerosol vertical structures is helpful for understanding the aerosol spatio-temporal distribution. In this study, the PM_2.5 values, aerosol extinction profiles and air mass backword trajectories exported from Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model were clustered into representative clusters in three severe polluted cities of China, Beijing, Shanghai and Guangzhou. The analysis of relationship between air mass trajectories and aerosol profiles from 2014 to 2016 showed that the air masses from the northern direction had positive effects for the pollution diffusion. The southern and coastal air masses kept the pollutant hovering in the vertical sky from near surface to the height about 1km above sea level. Comparing the effect of air masses in these three cities, the effect of air masses from the northern direction was more and more huge as the latitude increased. At the same time, the effect of air masses from the coastal direction were hugest in Guangzhou. As for PM_2.5 distributions, high PM_2.5 values in these three cities all occurred mostly in winter while low PM_2.5 distribution in each city had its own characters. The PM_2.5 pollutions from severe to slight were Beijing, Shanghai and Guangzhou. In addition, the PM_2.5 and aerosol extinction coefficient values in the near surface had positive relationship that the extinction coefficient values in high PM_2.5 days were larger than the extinction values in good air quality days. As the altitude increased but < 1km, the aerosol profiles in high PM_2.5 days sharply declined while the extinction coefficient values in low PM_2.5 days decreased slowly. Therefore, there're close relationship along the PM_2.5 values, air mass backword trajectories and aerosol profiles which can be helpful for other air quality studies in China.