Dear Authors,

I have reviewed the comments from three referees and your responses. While two of them recommended this work to be published in Atmospheric Chemistry and Physics, Referee #3 has pointed out the technical issues for quantifying BC absorption enhancement due to lensing effect using the filter-based measurement techniques that can affect the subsequent argument regarding suppression of lensing effect by BrC at the shorter wavelength. Overall, I find this manuscript presents valuable observations to advance our understanding on atmospheric BC and BrC absorptions and to address the potential impacts of BC-BrC interactions on total aerosol absorptions. Nevertheless, I would like to make two major comments on the revised version that are related to some of the comments from Referee #3 before considering this work to be published in Atmospheric Chemistry and Physics.

1) Section 3.5: The authors speculate that the observed BC absorption enhancement (Eabs) is primarily due to the lensing effect of BC coatings (line 365). However, it is possible that only a fraction of BC coating proxy (e.g., OOA+BBOA+NO3+SO4) are internally mixed with airborne BC. I suggest the authors to further comment whether the filter-based Eabs can be also caused by those chemical components that are externally mixed with BC and perhaps other factors such as calibration uncertainties and particle morphology. If so, the filter-based BC lensing effects (or Eabs) can be fundamentally different from the “true” lensing effects for airborne BC, and hence the two terms should not be interchangeable although the filter-based Eabs values are not significantly different from those reported in the literature based on in-situ measurements (lines 395-398). If this is the case, it is strongly recommended to use the operational-defined term “Filter-based Eabs” all the time (including the sub-heading) to avoid over-interpretation of data/misleading conclusion.

2) Section 3.6 and 3.7: While the suppression of filter-based BC lensing induced by BrC coatings is a novel observation that can provide important insight into our understanding of BC-BrC interaction and total aerosol absorption as well as uncertainties of filter-based measurements for quantifying BrC absorption, I agree with Referee #3 that the closure calculation involves many assumptions and simplified concepts that may lead to over-interpretation of results. Overall, I think it is still important to report the possibility of filter-based BC lensing suppression due to BrC coatings and such data analysis approach to the scientific communities for future research but the authors should tone down some of the related arguments/conclusion throughout the manuscript. Both quantifiable and non-quantifiable uncertainties described in Appendix C should be clearly presented in the main text to ensure the reader can easily recognize the major uncertainties and limitation of the closure calculation.

Alex

Dear Authors,

I have reviewed your revision, and found that my major comments have been addressed appropriately. I am happy to recommend this work to be published in ACP. Congratulations!

Alex