Dear Dr. Mok,

This is a very interesting paper with a lot of new findings, including methods, results, comparisons related with SSA retrieval.

I only have two comments:

Since you are (partly with one figure) presenting the spectral dependence of SSA from VIS-NIR to the UV it would be good to discuss in the introduction other studies with similar findings at urban areas, for example:
Ialongo, I., Buchard, V., Brogniez, C., Casale, G. R., and Siani, A. M.: Aerosol Single Scattering Albedo retrieval in the UV range: an application to OMI satellite validation, Atmos. Chem. Phys.,
10, 331–340, doi:10.5194/acp-10-331-2010, 2010.
Kazadzis, S., Raptis, P., Kouremeti, N., Amiridis, V., Arola, A., Gerasopoulos, E., and Schuster, G. L.: Aerosol absorption retrieval at ultraviolet wavelengths in a complex environment, Atmos. Meas. Tech., 9, 5997-6011, https://doi.org/10.5194/amt-9-5997-2016, 2016.

Secondly:
Following the comment of one of the reviewers on the descrepencies of the two retrievals (AMP, SKYNET) at higher wavelengths:
I think that the discrepencies (fig. 5 and 7) for 675nm and 870nm are relatively quite high with cc 0.55 and 0.41, at least compared the the VIS range. But also compared to the UV range where someone should expect larger discrepencies mainly due to the AOD differences at 340nm.

I think it is important to discuss this issue in the conclusion section so future readers or users of such data can use your an assessment in order to describe their results. Especially becasue of the fact that SSA retrieval with those instruments at those wavelengths are methodologically more standard in the literature.

Congratulations for a very interesting work
SK