The formation mechanism of air pollution episodes in Beijing city: Insights into the measured feedback between aerosol radiative forcing and the atmospheric boundary layer stability.

摘要: Based on the high-resolution observation of meteorological factors profiles, particulate matter concentration and aerosol radiative forcing (ARF) from 25 August to 17 November 2018 in Beijing, feedback between ARF atmospheric boundary layer (ABL) stability was systematically investigated during air pollution episodes. There initial explosive growth (PM) that PM2.5 sharply increased ~8μgm-3 ~100μgm-3, with optical depth (AOD) increasing ~0.25 ~0.58. This transport phase dominated by southerly winds. As PM increased, high loading scattered more solar radiation cooling earth-atmosphere system (ARF at top column (TOA): ~5Wm-2 ~-52Wm-2). Meanwhile, absorbed heated interior (ATM) ~21Wm-2 ~42Wm-2. The absorption scattering effects together cooled surface (SFC): ~-16Wm-2 ~-90Wm-2). Thus, ABL rapidly following cumulative heavy a strong temperature inversion (inversion ~300-1000m) occurring. In turn, persistent caused significant accumulation moisture (water vapor density ~5-10gm-3) pollutants, were prone physicochemical reactions high-humidity environment, further PM. It constant effect continually reduced environmental capacity aggravated (PM2.5 AOD reaching ~95-125μgm-3 ~1.38-1.75, respectively). Finally, broken dry, clean north winds appearing Beijing dissipation phase.