Abstract:

Using air quality monitoring data, surface meteorological data, and LiDAR detection data, we analyzed the variation of air pollutants and meteorological parameters and the influence mechanisms during a haze pollution event in Changchun during January 10-15, 2019.The results showed that the heaviest pollution period occurs on January 12-13, with mass concentrations of PM_2.5 and PM₁₀ exceeding 150 μg·m^-3 and the aerosol extinction coefficient reaching the highest level.The PM_2.5/PM₁₀ ratio values are higher than 0.7 at most times (>70%), indicating the important contribution of fine particles to this heavy pollution event.During heavy pollution period, near-surface wind speed remains low, relative humidity increases, air pressure varies hardly, and low-level wind direction changes.Weak descending motion, temperature inversion, and shallow boundary layer weaken the horizontal and vertical diffusion capacity of the atmosphere together, which favors the accumulation of air pollutants and the formation of this haze pollution.Changchun is located ahead of a trough and in the rear of a ridge at 500 hPa.Meanwhile, weak westerly winds prevail and relative humidity is high at 850 hPa.The sea-surface air pressure field is characterized by low-pressure cyclones and weak southwest flows, which results in the transport of pollutants to Changchun and enhances haze pollution.On January 14-15, the upper-level trough is deepened and moves eastwards, and the northwest airflow at 850 hPa and the near-surface pressure gradient are strengthened, leading to the dispersion of air pollutants and ending this haze pollution event.

Key words: Haze pollution, Meteorological condition, Aerosol extinction coefficient