A typical air pollution event caused by external source transport during 2008 in Qingdao, Shandong province

Based on the global reanalysis data (2.5°×2.5°) from the United States environmental protection center and back trajectory model (HYSPLIT-4) from NOAA, the typical air pollution event from May 27 to June 2, 2008 was simulated in Qingdao. The results show the effect of atmospheric circulation pattern on the air pollution event is significant. There is one ridge and one trough on the 500 hPa upper weather chart. It makes the upper of north China controlled by strong northwest airflow. The center of cyclone formed in Mongolia moves eastward on the surface weather chart, which produces ascending airflow. The airflow carries a lot of surface fine particles into troposphere. The back trajectory analysis indicates that the effect of northwest airflow on the pollution event is significant during pollution period, while the source of air mass is mainly from the Yellow sea during non-pollution period.