Impact of Aerosol-PBL Interaction on Haze Pollution: Multiyear Observational Evidences in North China

Atmospheric aerosols have been found to influence the development of planetary boundary layer (PBL) and hence to enhance haze pollution in megacities. Previous works on aerosol-PBL interaction were mainly based on model simulation for short-term cases; so far, there is a lack of long-term observational evidences. In this study, based on multiyear measurements and reanalysis meteorological data, we give observational evidences on aerosol-PBL interaction and its impact on pollution aggravation. We found a significant heating in upper PBL with maximum temperature change about 0.7 degrees C on average and a substantial dimming near surface with a mean temperature drop of -2.2 degrees C under polluted condition. By integrating Eulerian forward simulation and Lagrangian backward trajectory calculation, we demonstrated that the atmospheric heating was mainly induced by light-absorbing aerosols like black carbon. Then an index representing such effect was proposed, which could well characterize aerosol-PBL interaction and its impact on air pollution. Plain Language Summary In polluted regions like China, atmospheric aerosols can influence the meteorology by warming the upper air and blocking sunlight that would otherwise warm the surface. The opposite temperature tendencies due to aerosol, that is, atmospheric heating and surface dimming, make the air increasingly stable and stagnant. These effects then greatly weaken the diffusion and dilution of pollutants, thereby worsening air quality.