|Review of the revision to "Evidence of the complexity of aerosol transport in the lower troposphere on the Namibian coast during AEROCLO-sA" by Chazette et al.|
I appreciate the authors' revisions in response to the two reviews, and in my opinion these revisions have improved the manuscript. In particular, adding the discussion of uncertainties was useful and the discussion of the potential transport of aerosol from South America has been resolved to my satisfaction.
I do have a lingering concern that some of the statements interpreting the lidar results, in particular, the lidar ratio, are over-interpreted. If my understanding of the retrieval technique is correct, the attenuated backscatter profiles are retrieved to extinction using (1) in the free troposphere, the lidar ratio that was assumed by CALIOP or CATS for their retrievals and (2) in the PBL, a lidar ratio selected from the small set of lidar ratio models of CALIOP or CATS, whichever one creates the best match to the sun photometer AOD. Since the lidar ratio in the free troposphere is merely assumed, it is not appropriate to discuss changes in the lidar ratio as if it is an observation. (Of course, the CALIOP and CATS algorithms do not choose it arbitrarily; it's based on other evidence, but it is not a direct observation. If some comment is to be made about it, it should be made about the evidence that was used in the lidar ratio selection, which is probably primarily the altitude of the aerosol layers and the satellite-observed attenuated depolarization.) In the PBL, since only a few lidar ratios are attempted, the precision or resolution of the lidar ratio is extremely coarse, and so the authors should likewise be very careful not to over interpret the results.
If the authors would consent to make the following changes, I would appreciate it. Other than this, I would be happy to see this manuscript published.
line number refer to v5
257: "significant changes in LR are also observed between P1/P2 and P3 with values in the FT evolving". This should be deleted. There is no observation (only assumptions) of lidar ratio in the free troposphere. If the authors want to keep something like this, I suggest something more like "CALIPSO and CATS retrievals suggest differences in the FT aerosols between P1/P2 and P3, with more occurrence of polluted dust in P1/P2 and polluted continental or smoke in P3."
259: and for the PBL, again, since the retrieval here is quite coarse, I suggest rewording to something like "In the PBL, the low value of lidar ratio required to reproduce the sunphotometer AOT is consistent with the presence of clean marine aerosols in the PBL. The higher lidar ratios required in P3 indicate the presence of other aerosol types, which may include smoke or a mixture of smoke and terrigenous aerosols."
268-269: The higher lidar ratio from this retrieval is not by itself indicative of dust. Any aerosol type other than marine aerosol or mixed with marine aerosol would produce a higher lidar ratio than the clean marine case; it does not require dust to explain this. I suggest deleting this sentence and simply waiting a few lines until the depolarization ratio is discussed before bringing up the hypothesis of a dust mixture.
893: I believe this description is still somewhat confusing and I think the Author Response made it clearer. Consider replacing "obtained" with "selected from the discrete set of lidar ratios shown in Table 2" (if, in fact, this is an accurate description of the procedure).
896: consider replacing "are representative of" to "are associated with" and delete "and consistent with the LRs from CALIOP for these aerosol types (compare Table 3 and Table 2)". If the lidar ratio were derived to a precision of a few sr, finding the lidar ratio to match the expected values for clean marine would be evidence of the presence of clean marine aerosol; however, since only a few lidar ratios are attempted, this evidence is rather weak. The statement that they are consistent with lidar ratios for CALIOP types seems to be merely redundant, since the retrieval used only those lidar ratios that correspond to CALIOP aerosol models (if I understand the response in the Author Response correctly).