| 26 Sep 2025
In-Tandem Multi-Waveband Particulate Absorption and Size Observations Yield Substantial Increase in Radiative Forcing over Industrial Central China
Abstract. Coal-based industry in Shanxi, China, including power generation, steel, coke, and chemical manufacturing, emits large quantities of black carbon (BC), contributing significantly to regional aerosol radiative forcing. However, there are substantial scientific uncertainties in the radiative properties of the aerosols in these types of regions due to multiple sources of BC and high emissions of co-emitted aerosol precursors, producing mixed aerosols of different ages, sizes, and morphologies. This study combined optical particle size and multi-band in-situ BC mass and column aerosol optical depth, with MIE modeling to simulate optical properties per particle and over the atmospheric column for absorbing aerosols. These results are applied in a radiative transfer model to constrain regional radiative forcing. First, BC shows a trimodal fine-mode (size<2.5 μm) size distribution, substantially differing from current assumptions of aerosol size made by satellite and atmospheric modeling communities. Second, the coating ratio between absorbing-core and refractive-shell varies dynamically, challenging the widely used fixed mixing ratio assumption. Thirdly, absorbed solar radiation under 500 nm is weaker than from 500 to 700 nm, and weaker still than above 800 nm, challenging assumptions of flat or decreasing absorption with radiative band. Our results yield a reduced single scattering albedo (-0.049 to -0.008) and substantial change in column number (-1.73×1012 to 5.74×1010 # m-2), resulting in radiative forcing from 0.3 to 3.0 W m-2, surpassing local CO2 and CH4 forcing. This work provides a realistic probabilistic framework to quantify BC aging and mixing induced optical properties in industrial regions.
Competing interests: One of the authors is a member of the editorial board of ACP.
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Comment to “In-Tandem Multi-Waveband Particulate Absorption and Size Observations Yield Substantial Increase in Radiative Forcing over Industrial Central China”
This study combined optical particle size and multi-band in-situ BC mass and column aerosol optical depth, with MIE modeling to simulate optical properties per particle and over the atmospheric column for absorbing aerosols, providing a realistic probabilistic framework to quantify BC aging and mixing induced optical properties in industrial regions. Valuable results have been shown. In principle, I would suggest its acceptance with necessary revisions.
Line 25-26, In addition to relatively old studies, recent studies could also be cited as supporting material, such as Chen et al., (2024, doi: 10.1038/s41467-024-52255-z) for direct climate effect.
Line 31-34, Regarding the solar radiation absorption of BC along with its impact on atmospheric thermal structure has also been examined by a recent study of Pei et al. (2025, doi: 10.5194/acp-25-10443-2025), which is also worthy to mention here.
Line 35-36, Actually, BC is not only from industrial regions, but also from natural sources such as biomass burning.
Line 39-41, The sentence could be rephrased to make it easier to follow.
Line 41-42, “properties” and “varies” cannot be used together.
Line 47-50, Gamma distribution is often used by previous studies.
Line 72, “quantification” and “estimates” cannot be used together.
Line 90, I wonder if there are many industrial areas in part countries of Global South.
Line 116, I am curious if it is right that the BC absorption is strong across various wavebands.
Line 124, Note that the Beer-Lambert law is an approximate solution to AOD, without considering multiple scattering, which might be worthy to mention?
Line 129-131, I wonder if the 2 times standard deviation threshold value is too small. I remember many studies use 3 times standard deviation threshold value. In other words, how do this threshold value affect the analysis results?
Line 137-139, please rephrase the sentence. It is currently weird with “in order to” at the end.
Line 139-140, To me, this sentence is also weird with grammar issue.
Line 160, TOA should be put behind the “top of atmosphere”
Line 170-174, How large uncertainties could this assumption introduce?
Line 187 along with other places, please check reference format to make them suitable.
Line 202, “sources” and “is” – grammar error.
Line 207, TOA has already been defined earlier in this study.
Line 211-213, Description writing issues! It seems that there are still many writing issues, with some of them pointed out here and earlier. I would suggest that the authors make a careful writing revision.
Line 215-219, Why do the authors select these three statistics?
Figure 2, I would change “orange” color to others so that it could be more clear.
Line 295-297, I understand the logic and agree the assumption, but still wonder how would this assumption affect the results?
Line 323, “can presents”?