Dear Authors

Thank you for providing the revised manuscript “Assessment of cloud related fine mode AOD enhancements based on AERONET SDA product”.
Your revised manuscript has been re-reviewed and I have also conducted my own assessment of the manuscript. Some open issues remain, relating to potential retrieval errors as well as to the representativeness of the derived dataset.

Based on the reviewer’s comments and my own assessment I have concluded to reconsider your manuscript for publication in Atmospheric Chemistry and Physics after major corrections.

Kind regards,

Philip Stier
Co-Editor
Atmospheric Chemistry and Physics


Major issues:
1. The description of the used retrieval algorithms remains vague but the introduction seems to suggest that the used technique relies on direct-sun measurements, which are only possible for “thin enough” clouds. This is too vague. For any conclusions to be meaningful it needs to be entirely clear and reproducible what subset of observations the “cloudy sky” datasets represents. This also relates to comment 2 by reviewer 1, which has only been partially addressed. The conclusions refer to AOD enhancements of up to about 0.1 and suggest to include those in estimates of corresponding radiative effects but it is impossible to assess which fraction of the overall data this sample represents and what the corresponding synoptic / cloud regimes are. Some of the technical details are given in 2.1 but those do not allow to assess the overall impact on the representativeness of the retained retrievals.

2. With increasing cloud optical depth, the contribution of above cloud aerosol to the signal will presumably be attenuated, while below cloud aerosol still contributes. What role does the vertical distribution play? How sensitive are the results to the assumed cut-off of cloud optical depth? If the overall enhancement AOD under cloudy conditions is predominantly driven by boundary layer relative humidity then the impact on TOA direct radiative effects will be marginal so the meteorological regime and aerosol vertical distribution will matter.

3. The discussion of the AE enhancement through parcel modelling in 3.2 is interesting but I was missing a serious consideration of measurement and sampling uncertainties. The derived AE enhancements are small, but the uncertainties in fine mode AE retrievals (which is on its own highly derived product) are presumably not. Similarly, sampling errors may easily exceed these effects.

Overall, I was wondering if a demonstration of the retrieval accuracy under cloudy conditions based on synthetic data, allowing free variation of aerosol and cloud layers, would be required to demonstrate the accuracy of the approach. I may have missed if this has been done in some of the cited references, if so, some of this should be made more explicit in the introduction.

Other issues:

4. Line 73: “We included all the good quality data available from all AERONET sites for global analysis.” This is too vague.
5. Line 201: “The total column AOD and AE, as Cimel measurement would “see” from these modelled profiles”. Avoid informal language. Cimel is not defined.
6. Fig. 3,4: Are there other measurements available that could explain seasonality, e.g. RH?

Dear Authors

Thank you for providing the revised manuscript “Assessment of cloud related fine mode AOD enhancements based on AERONET SDA product” and the detailed explanations in your author response.

Your revisions have addressed the outstanding issues and I am pleased to inform you that the manuscript is now accepted for publication in Atmospheric Chemistry and Physics.

Thank you for choosing Atmospheric Chemistry and Physics.

Kind regards,

Philip Stier
Co-Editor
Atmospheric Chemistry and Physics