Abstract:

To study the influence of atmospheric circulation background and meteorological conditions on PM2.5 pollution in Midwest of Shandong Province, this paper uses meteorological and PM2.5 concentration data and selects Jinan as a typical representative city to diagnose and analyze the effect of atmospheric circulation background and meteorological evolution process on PM2.5 concentration in Jinan for the month of January 2014. The stable weather index formula of Jinan is established. Analysis shows that from the north of East China to the south of North China in January 2014, wind speed from the ground to the middle troposphere was a negative anomaly; thus, the ability of horizontal diffusion was very weak. Water vapor transportation enhanced by abnormal southerly winds helps gaseous pollutant to transform into aerosol and results in higher PM2.5 concentration. The East Asian winter monsoon is considerably weaker, with increased inversion temperature and poor vertical pollution diffusion ability. An abnormally high pressure of 500 hPa has inhibited the development of the East Asian trough and is more conducive to the accumulation of pollutants in the lower troposphere. Analysis of the weather evolution process shows that the meteorological conditions in both the horizontal direction at the ground and the vertical direction at high altitude can affect PM2.5 concentration. Results indicate that light wind, high humidity, and surface wind convergence can increase PM2.5 concentration; moreover, low depth of the planetary boundary layer, vertical airflow sinking, and increasing instability of atmospheric stratification in the middle and lower atmosphere can increase PM2.5 concentration and vice versa. A stable index can better predict air quality and heavy pollution process.

Key words: PM2.5, atmospheric circulation, haze; visibility, weather conditions;stable weather index