Preprints
https://doi.org/10.5194/acp-2021-139
https://doi.org/10.5194/acp-2021-139

  07 Apr 2021

07 Apr 2021

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

The effect of black carbon on aerosol-boundary layer feedback: Potential implications for Beijing haze episodes

Jessica Slater1,2, Hugh Coe1, Gordon McFiggans1, Juha Tonttila3, and Sami Romakkaniemi3 Jessica Slater et al.
  • 1Stockholm Environment Institute, Department of Environment and Geography, University of York, York, UK
  • 2Centre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
  • 3Finnish Meteorological Institute, Atmospheric Research Centre of Eastern Finland, Kuopio, Finland

Abstract. Beijing suffers from poor air quality particularly during wintertime haze episodes when concentrations of PM2.5 can peak at > 400 ug/m3. Black carbon (BC), an aerosol which strongly absorbs solar radiation can make up to 10 % of PM2.5 in Beijing. Black carbon is of interest due to its climatic and health impacts. Black carbon has also been found to impact planetary boundary layer (PBL) meteorology. Through interacting with radiation and altering the thermal profile of the lower atmosphere, BC can either suppress or enhance PBL development to various degrees depending on the properties and altitude of the BC layer.

Previous research assessing the impact of BC on PBL meteorology has been investigated through the use of regional models which are limited both by resolution and the chosen boundary layer schemes. In this work, we apply a high resolution coupled large eddy simulation-aerosol-radiation model (UCLALES-SALSA) to quantify the impact of black carbon at different altitudes on PBL dynamics using conditions from a specific haze episode which occurred from 1st–4th Dec 2016 in Beijing. Results presented in this paper quantify the heating rate of BC at various altitudes to be between 0.01 and 0.016 K/h per μg/m3 of BC, increasing with altitude but decreasing across the PBL. Through utilising a high resolution model which explicitly calculates turbulent dynamics, this paper showcases the impact of BC on PBL dynamics both within and above the PBL. These results show that BC within the PBL increases maximum PBL height by 0.4 % but that the same loading of BC above the PBL can suppress PBL height by 6.5 %. Furthermore, when BC is present throughout the column the impact of BC suppressing PBL development is further maximised, with BC causing a 17 % decrease in maximum PBL height compared to only scattering aerosols. Combining these results in this paper, we present a mechanism through which BC may play a prominent role in the intensity and longevity of Beijing’s pollution episodes.

Jessica Slater et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-139', Mona Kurppa, 28 Apr 2021
  • RC2: 'Comment on acp-2021-139', Anonymous Referee #2, 03 Jul 2021

Jessica Slater et al.

Jessica Slater et al.

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Short summary
This paper shows the specific impact of black carbon (BC) on the aerosol-planetary boundary layer (PBL) feedback and its influence on a Beijing haze episode. Overall, this paper shows that strong temperature inversions prevent BC heating within the PBL from significantly increasing PBL height, while BC above the PBL suppresses PBL development significantly through the day. From this we suggest a method by which both locally and regionally emitted BC may impact Beijing haze episodes.
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