Numerical simulation of the influence of major meteorological elements on the concentration of air pollutants during rainfall over Sichuan Basin of China

Özet

To study the wet removal effect of rainfall on the air pollutants in Sichuan Basin, the WRF-Chem model isadopted to simulate the changes of air pollutant concentrations before and after a rainfall episode. The resultsshow that continuous rainfall with small-magnitude rainfall (0.3–0.5 mm h−1) has an obvious effect in reducingthe concentrations of PM2.5, PM10, SO2 and NO2 except for O3. There is an upper limit of the impact of continuous rainfall on air pollutants. The reduction of concentrations of particulate pollutants at the level of300–2500 m is due to its participation in the nucleation process. When rainfall occurs and vertical diffusion isnot restricted, the concentration of pollutants on the ground are reduced more quickly by being transported tohigh altitude. In urban areas with near-surface inversion, there is an anti-correlation between concentrations andwind speed. The correlation coefficients for the concentrations of PM2.5, PM10, SO2 and NO2 with the wind speedare −0.85, −0.86, −0.77 and −0.82, respectively. In suburban stations with the small initial concentrations,the decrease of concentrations is mainly due to the increase of rainfall intensity, but has little relationship withthe height of PBL and the wind speed. The small gradient of sea level pressure (less than 1 hPa) and the near surface inversion in the Chengdu Plain are conducive to the accumulation of air pollutants.