Reinforcement Of Secondary Circulation By Aerosol Feedback And Pm2.5 Vertical Exchange In The Atmospheric Boundary Layer

The secondary circulation (SC) plays a vital role in the vertical exchange of meteorological variables and aerosol particles between the atmospheric boundary layer (ABL) and the free atmosphere. We show that, under favorable synoptic-scale weather conditions aggravating PM2.5 pollution, heavy particle contaminations reduce wind speed in the low ABL via an aerosol feedback mechanism that perturbs the SCs. We examine the aerosol feedback impact on the reinforcement of SCs subject to heavy PM2.5 pollution occurring in Beijing and its surroundings in China. Results reveal that episodic and composite heavy PM2.5 events simulated by the aerosol feedback model runs reduce the ABL wind speeds and enhance the SC. We identify the SC signals by the differences of resultant wind speeds and PM2.5 concentrations between "feedback" and "nonfeedback" simulations under the presence of a hill topographic forcing, which is conducive to the vertical exchange of PM2.5 between the ABL and free atmosphere.