The two-way feedback effect between aerosol pollution and planetary boundary layer structure on the explosive rise of PM2.5 after the “Ten Statements of Atmosphere” in Beijing

Abstract

Are there still persistent heavy aerosol pollution episodes (HPEs) in Beijing one year after the implementation of the “Action Plan for the Prevention and Control of Air Pollution (“Ten Statements of Atmosphere” in China: 2013–2017)”? Will the cumulative aerosol pollution still induce significant two-way feedback between PM2.5 and the planetary boundary layer structure? Answers to these matters are particular concerns of the government and the public. The analysis of the vertical structure of the aerosol and meteorological factors in planetary boundary layer shows that the two-way feedback between unfavorable meteorological conditions and PM2.5 pollution cumulating is still the primary mechanism for the maintenance of HPEs, accounting especially ~66% to 88% for explosive rise in PM2.5, in autumn and winter in Beijing area a year after the “Ten Statements of Atmosphere”. This effect also shows that the concentration of PM2.5 in Beijing had not fallen low enough to decouple the influence of unfavorable meteorological factors. The increased level of PM2.5 mass during the explosive rise stage was similar to those of the precursor gases of NO2, SO2 and CO, as well as to the declining ratio of the boundary layer height (BLH), which also suggest that the interaction between PM2.5 cumulating and the boundary layer structure is playing a leading role for the maintenance of HPEs and the PM2.5 explosive rise in Beijing. The depolarization ratio signal of the Lidar also shows that the transit of mineral aerosols from the northwest over Beijing often appears in the upper layer of the planetary boundary layer or higher atmosphere during the late or subside stage of HPEs.