(57d) Enhanced Light Absorption and Radiative Forcing By Black Carbon Agglomerates | AIChE

(57d) Enhanced Light Absorption and Radiative Forcing By Black Carbon Agglomerates


Pratsinis, S. E., ETH Zurich
Fan, L. S., Ohio State University
Lohmann, U., ETH Zurich
Neubauer, D., ETH Zurich
The climate models of the Intergovernmental Panel on Climate Change (IPCC) list CO2, CH4 and black carbon (BC), as the most potent contributors to global warming based on their radiative forcing (RF) impact. Among them, the BC contribution comes with the highest uncertainty (~ 90 %). Examining closely these models, it becomes apparent that they might underpredict significantly the direct RF for BC, largely due to their assumed spherical BC morphology (Kelesidis & Pratsinis, 2021). In specific, the light absorption and direct RF of BC agglomerates are enhanced by light scattering between their constituent primary particles (Kelesidis et al., 2020) as determined by the Rayleigh-Debye-Gans theory interfaced with discrete dipole approximation (Kelesidis & Pratsinis, 2019) and recent relations for the refractive index and lensing effect. The resulting light absorption agree very well with the observed absorption aerosol optical depth of BC. ECHAM-HAM simulations accounting for the realistic BC morphology and its coatings reveal high direct RF = 3 - 5 W/m2 in East, South Asia, sub-Sahara, western Africa and the Arabian peninsula (Fig. 1). These are in agreement with satellite and AERONET observations of RF and indicate a regional climate warming contribution by 2.4 - 4 oC, solely due to BC emissions.


Kelesidis, G. A., and Pratsinis, S. E. 2019. Soot light absorption and refractive index during agglomeration and surface growth. Proc. Combust. Inst. 37:1177-1184, doi.org/10.1016/j.proci.2018.08.025.

Kelesidis, G.A., Kholghy, M.R., Zuercher, J., Robertz, J., Allemann, M., Duric, A., and Pratsinis, S.E. 2020. Light scattering from nanoparticle agglomerates. Powder Technol. 365:52–59, doi.org/10.1016/j.powtec.2019.02.003.

Kelesidis, G. A., and Pratsinis, S. E. 2021. Determination of the volume fraction of soot accounting for its composition and morphology. Proc. Combust. Inst. 38:1189-1196, doi.org/10.1016/j.proci.2020.07.055.

Figure 1. Global map of the direct RF of coated BC agglomerates estimated by ECHAM-HAM.