Preprints
https://doi.org/10.5194/acp-2021-611
https://doi.org/10.5194/acp-2021-611

  06 Sep 2021

06 Sep 2021

Review status: this preprint is currently under review for the journal ACP.

Simulated impacts of vertical distributions of black carbon aerosol on meteorology and PM2.5 concentrations in Beijing during severe haze events

Donglin Chen1, Hong Liao1, Yang Yang1, Lei Chen1, Delong Zhao2, and Deping Ding2 Donglin Chen et al.
  • 1Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Jiangsu Engineering Technology Research Center of Environmental Cleaning Materials, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing, Jiangsu, China
  • 2Beijing Weather Modification Office, Beijing 100089, China

Abstract. Vertical profiles of black carbon (BC) play a critical role in BC-meteorology interaction which influences PM2.5 (particulate matter with a diameter of 2.5 μm or less) concentrations. In this study, we used the Weather Research and Forecasting with Chemistry model (WRF-Chem) coupled with an improved integrated process (IPR) analysis scheme to investigate the direct radiative effect (DRE) of BC with different vertical profiles on meteorology and PM2.5 concentrations in Beijing during two severe haze events (11–12 December 2016 and 16–19 December 2016). The vertical profiles of BC in Beijing collected by King-Air350 aircraft can be classified into two types: the first type was characterized by decreases in BC concentration with altitude, which was the case mainly controlled by local emissions; the second type had maximum BC concentration around 900 hPa, which was mainly affected by regional transport from the polluted south/southwest region. Compared with measurements in Beijing, the model overestimated BC concentrations by 87.4 % at the surface and underestimated BC mass by 14.9 % at altitudes of 300–900 m altitude as averaged over the two pollution events. The BC DRE with the default vertical profiles from the model heated the air around 300 m altitude but the warming would be stronger when BC vertical profiles were modified for each day using observed data during the two severe haze events. Accordingly, compared to the simulation with the default vertical profiles of BC, planetary boundary layer heights (PBLH) were reduced further by 24.7 m (6.7 %) and 6.4 m (3.8 %) in Beijing and simulated PM2.5 concentrations were higher by 9.3 μg m−3 (4.1 %) and 5.5 μg m−3 (3.0 %) over central Beijing in the first and second haze events, respectively, with modified vertical profiles. Furthermore, we quantified by sensitivity experiments the roles of BC vertical profiles with six exponential decline functions (C(h) = C0 × eh/hs and hs = 0.35, 0.48, 0.53, 0.79, 0.82 and 0.96) parameterized on the basis of the observations and the vertical profile dominated by regional transport. A larger hs leads to a sharper decline of BC concentrations with altitude (less BC at the surface and more BC in the upper atmosphere), resulting in a stronger cooling at the surface (+0.21 with hs of 0.35 vs. −0.13 °C with hs of 0.96) and hence larger reductions in PBLH (larger BC-induced increases in PM2.5). Relative to the simulation without BC DRE, the mean PM2.5 concentrations were increased by 5.5 μg m−3 (3.4 %) and 7.9 μg m−3 (4.9 %) with BC DRE when hs values were 0.35 and 0.96, respectively. Our results indicate that it is very important to have accurate vertical profiles of BC in simulations of meteorology and PM2.5 concentrations during haze events.

Donglin Chen et al.

Status: open (until 18 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Donglin Chen et al.

Donglin Chen et al.

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Short summary
Black carbon (BC) vertical profile plays a critical role in BC-meteorology interaction which also influences PM2.5 concentrations. More BC mass was assigned into high altitudes (above 1000 m) in model, which resulted in stronger cooling effect near the surface, larger temperature inversion below 421 m, more reductions in PBLH and more increase in near-surface PM2.5 in the daytime caused by the direct radiative of BC.
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