Dear Sirs:
I suggest that you improve your paper and re-submit. My comments are attached.
Best wishes,
Alexander Kokhanovsky
Minor comments:
1. Fig.2 must be improved ( see your caption for axis OX; also for clarity I would suggest that you have just 2 lines in this figure - say, solid and broken)
2. Fig.3. Please, check the caption on the axis OX in both panels.
3. Fig.4a. I would suggest to have the same caption on axis OX as in Fig.3. Also I would propose to change the caption for axis OY ( ratio of absorption coefficients ( say, r)). I do not understand why r for the red line is not equal to 1.0 at 450nm. Please, explain in the caption.
Major comments:
You state that the conventional belief is that tar balls are not strong absorbers in the near IR. I would suggest that you extend your Introduction by analyzing some papers, which report smaller absorption by brown carbon in near - IR and also pointing to the possible reasons for the differences with your results.
In particular, I would suggest that you review the results of the following papers in Introduction:
1) ) Laskin et al. (2015): Chemistry of Atmospheric Brown Carbon, Chem. Rev. 115, 4335−4382
2) Chakrabarty et al. (2010): Brown Carbon in Tar Balls from Smoldering Biomass Combustion. Atm. Chem. Phys., 10, 6363-6370.
3) Chakrabarty et al. (2016): Brown carbon aerosols from burning of boreal peatlands: microphysical properties, emission factors, and implications for direct radiative forcing. Atm. Chem. Phys., 16, 3033-3040
4) Drinovec et al. (2017): The filter-loading effect by ambient aerosols in filter absorption photometers depends on the coating of the sampled particles, Atm. Meas. Technol., 10, 1043