Preprints
https://doi.org/10.5194/acp-2020-54
https://doi.org/10.5194/acp-2020-54

  17 Feb 2020

17 Feb 2020

Review status: this preprint has been withdrawn by the authors.

Mixing state of black carbon and its impact on optical properties and radiative forcing over East Asia

Xiaoyan Ma1, Hailing Jia1, Rong Tian1, Fangqun Yu2, and Jiagnan Li3 Xiaoyan Ma et al.
  • 1Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD)/Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science & Technology, Nanjing 210044, China
  • 2Atmospheric Sciences Research Center, State University of New York, Albany, NY, USA
  • 3Environment and Climate Change Canada, Victoria, BC, Canada

Abstract. BC mixing state, one of essential aerosol microphysical properties modulating its optical properties and radiative forcing, and climatic and environmental effect, has often been assumed in numerical models previously. In this study, by employing a nested version of GEOS-Chem-APM model with predicted BC mixing state, we carefully examined the effect of BC mixing state on aerosol optical properties, radiative forcing, and heating rate over East Asia (EA) and particularly in East-Central China (ECC). The modelling results show that the mass of both BC core and coating by secondary species (coated SS) are significantly high in ECC and India due to strong anthropogenic emissions but quite low in the other regions. The ratio of total mass (BC + coated SS) to the BC over ECC can be doubled compared to pure BC core mass, indicating quite large coating over the regions with high anthropogenic emissions. Absorptive aerosol optical depth (AAOD) enhances ~ 40 % over ECC once core-shell mixing, rather than external mixing, is taken into account, despite AOD only changes slightly, and the resulting absorption amplification (Aa) normally varies from 1.1 to 1.8 over ECC. Aerosol direct radiative forcing (DRF) under clear sky and all sky indicate that DRF at top of atmosphere (DRFTOA) become weaker but DRF at surface (DRFSRF) become stronger when core-shell mixing, instead of external mixing, is taken in to account in the simulation. The simulation with core-shell mixing presented that over ECC, the regional-averaged atmospheric absorption enhances 39 % while DRFTOA and DRFSRF are reported as −8.3 and −17.8 W m-2, compared to −9.4 and −16.2 W m-2 in the simulation with external mixing state. The heating rate in entire column enhances with core-shell mixing state due to absorption amplification, compared to external mixing state. The heating rate at surface over ECC increases about 43 %, i.e. increase from 0.7 K day-1 (external) to 0.9 K day-1 (core-shell) during the study period. The results in three cities (Beijing, Nanjing, Chengdu), representative of North China Plain (NCP), Yangtze River Delta (YRD), and Sichuan Basin (SCB), major anthropogenic aerosol emissions regions over EA, are also discussed in the study.

This preprint has been withdrawn.

Xiaoyan Ma et al.

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Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Xiaoyan Ma et al.

Xiaoyan Ma et al.

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This preprint has been withdrawn.

Short summary
BC Mixing state, is one of critical microphysical properties to modulate optical properties, radiative forcing (RF), and climatic effect. However, it has been simply assumed previously as either external or internal mixing. In this study, by employing a nested GEOS-Chem-APM with predicted BC mixing state, we examined the effect of mixing state on aerosol optical properties, RF, and heating rate over East Asia. This will improve the predictions of aerosol climatic effect in the future.
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