GMD Topical Editor Review at "Decision stage" of "Investigating the impact of aerosol climatologies in regional climate model simulations over Europe", by Vasileios Pavlidis et al.

Although both reviewers of this manuscript found major revisions were required, in each case this was to do with the way the research was presented or organised.

The reviewers have provided some specific ways the analysis could be better presented.

The authors have responded positively to the suggestions and replied to each comment, with the replies to reviewer comments well set out, first summarising the main ways the article has been improved, and the replies have certainly addressed most of the reviewer's concerns.

The added Figure (new Figure 2) showing the vertical profile in aerosol extinction for the different runs provides additional insight into the way the system adjusts to the aerosol-radiation and aerosol-cloud interactions.

However, in many cases the new excerpts of text added are surprisingly poorly worded, suggesting these have not been properly checked among the author team.

There remain still basic structural errors unresolved -- section 3.3 in particular is not properly organised into subsections, somehow losing the subsection-title style in the previous sections, which were well organised. This section needs to be re-written with clear distinct subsections.
Some parts of the article are in good shape, but other parts have not been carefully checked.

There has been an improvement, and the article can be publishable after the new Figure 2 is re-plotted, the section 3.3 re-written, and some other minor points remedied.

The reviewers' comments were almost entirely restricted to the way the research was carried out, and the authors have clearly made efforts to improve the manuscript, the reviewer comments properly answered in the replies, but with the changes added poorly worded.

I am providing a Topical Editor review at this Decision stage to specify the changes needed.

The article is close to publication standard but remains poorly worded in several places and section 3.3 needs to be properly organised.

I am providing pointers to these as a list of minor corrections, which I suggest the full author team go through and remedy.

These are not major revisions and just a question of re-wording to then make the manuscript ready for publication in GMD.

Topical Editor (Decision stage) Review
-----------------------------------------------

1) Figure 2 -- the authors have added this Figure to demonstrate the response effects of the aerosol-radiation and aerosol-cloud interactions. And the Figure does help to understand the how the tropospheric aerosol layer responds in vertical profile, the regional weather model's high resolution resolving the dynamics and mixing more realisitically than in global models.

However, the graphs currently show AOD-increments at each model level, whereas to analyse "the vertical distribution of AOD", requires to show the vertical profile with units of extinction per unit altitude.

Please re-plot Figure 2 with the graph showing the vertical profile in aerosol extinction (per km).

2) Aerosol optical property acronyms/symbols need to have corresponding wavelength

Whenever AOD is given in the text, it should be provided with the corresponding wavelength.
The same goes in general for single scattering albedo and asymetry parameter, although since in this manuscript these terms are only discussed in general terms, these can remain without a specific wavelength.

Aside from where AOD is discussed in general terms, please change all instances of AOD (and extinction when this is introduced) to be given with the wavelength in subscript. For the Figures the wavelength can be specified in the caption, but specifying the wavelength is essential good practice within the aerosol community and is required throughout section 3 and in Table 2. Section 2.3 is OK since the wavelength is introduced within that subsection.

3) Section 3.1 -- new para of text beginning "We mainly compare..." -- this para is mostly fine and it helps to give the overview text here, -- minor point "use the SEVIRI product to increase robustness" -- re-word to "as an additional test for the model" or similar. The sentence re: winter and autumn needs to be clarified to better explain what you mean. They are obviously very different types of satellite instrument, so please clarify the specifics of what you mean here, or delete the sentence.

4) Section 3.1 -- new para of text beginning "The fields of the satellite datasets..." -- this is strange wording to begin the para -- you mean "AOD distribution" I guess -- please re-word.
This para is an example of the specific values given for AOD without corresponding wavelength. Please add subscript 550 after AOD. "have larger AOD values" -- you need to generalise to "have a systematically higher AOD on average" or similar more scientific statement.

5) Section 3.1 -- The new paragraph beginning "vertical AOD profiles" -- since AOD is implicitly a column-integrated property it does not make sense to plot the vertical profile, unless presenting per unit altitude -- that is the definition of the properity "aerosol extinction". It's just a case of re-plotting Figure 2 to show aerosol-extinction (per km) and re-wording this paragraph to refer to "vertical extinction profile" rather than "vertical AOD profile" -- also in the caption. Similarly decrease in extinction at higher altitude not decrease in AOD at higher altitude.

6) Section 3.3.1 -- This new para seems to have lost the initial subsection 3.3 title.
The article has italicised subsections "Clear sky radiation at the surface", "Radiation at the surface and RE" and "Total cloud fraction and cloud forcing", and this looks like a minor editing error that these should be labelled 3.3.1, 3.3.2 and 3.3.3, with the "Aerosol-radiation interactions" as the main sub-section 3.3. This is part of what the reviewers were meaning re: improving the readibility/organisation -- and this section seems to have lost focus and remains to be properly organised into distinct sub-sections. That should be easy to do, but until this is done the article will not be publishable.

7) Sub-section "Clear-sky direct radiative effect"

A new acronym has been introduced here that is not explained -- some glitch here in the editing and not properly checked. See comment 6 above -- the subsections here need to be organised into distinct sub-sections.

Also, in the new para beginning "The Tegen climatology" the significance of the decrease in SSA from 1.0 needs to be explained to the reader as an increase in absorption. Also suggest to introduce the term "forcing efficacy" to similarly better communicate the significance of "the decrease of clear sky radiation per unit AOD".

8) Sub-section "Radiation at the surface and RE"

There are some obviously terminology typos here that need to be remedied before publication. I can only assume this section has not been reviewed properly by the co-authors, and perhaps under some pressure to submit within some timescale.

For example DNI text seems unnecessary and that para is not communicated adequately, as identified by the reviewers.

Please re-word this subsection to ensure the article can be published.

9) Sub-section "Radiation at the surface and RE" -- Excerpt of text beginning "However the internal model variability" needs to be re-ordered -- I think you just mean there is an interaction here that you're identifying that can contribute to the climate variability -- but again, the new text added is not clear.

10) Table 2 caption -- "optival" -- please correct this and use spell checker on the article.

11) New text added beginning "Cases of such strong reduction are not spatially extended" is poorly worded and needs to be re-worded -- re-word more scientifically to "are limited in spatial extent" or similar. Also this para says "at grid point level" needs more scientific explanateion such as "in localised areas".

12) Last para before section 3.3.3 -- again the new text added is poorly worded.

You have "In general the decrease of the radiation at the surface leads again to surface cooling"
But that's a tautology. What I think you mean is that the aerosol effects cause a net cooling -- which is expected of course. If this text is summarising, it's OK to keep this but suggest to re-word along the lines of:

"As expected, the net aerosol effects (with both ARI and ACI) lead to a decrease in radiation at the surface" or similar -- but the author team should review this in the context of the rest of this subsection which needs to be properly re-organised -- and almost cetainly reduced -- to then just make the main points in subsections as in section 3.2

13) Conclusion sections -- again the new text added weakens the article -- this needs to be checked more carefully. You have "at the grid point level" but this is basic scientific explanation -- you mean locally to a particular region or so -- re-word to properly explain what is meant.

GMD Topical Editor post-review decision-point review of revised submission of
"Investigating the impact of aerosol climatologies in regional climate model
simulations over Europe", by Vasileios Pavlidis et al.

The two main reviewers of this manuscript found major revisions were required in their
original review, and the authors revised the manuscript addressing most of these comments.
However, although the revised manuscript was close to publication standard at that revised stage,
still some sections remained poorly worded, with also some structural errors in latter parts
of the results (sections 3.3, 3.4) that the co-author team had clearly not properly checked.

As Topical Editor, I carried out a "post-review decision-point Topical Editor review" of the
revised manuscript and found the article could be publishable once a list of minor corrections
were carried out to address the poorly-worded sections and structural deficiencies.

The authors have addressed each of those further corrections in my post-review decision-point
Topical Editor review, and the later sections of the Results are now well-organised, and the
paper hangs together now.

There remain a small number of very minor corrections required (mostly at the typographical level
or to improve how the article reads), and I am therefore now content to recommend publication
once a final set of minor revisions, listed below, are carried out.


Final set of minor revisions required before publication
--------------------------------------------------------

1) Page 13, line 6 -- This new text is clumsily worded, please re-word
"as we move towards higher altitudes" instead to "with increasing altitude".

2) Page 13, line 7 -- Also needs to be more scientifically and specifically
worded -- replace "considerably smaller values" with "considerably less extinction"
or "considerably less aerosol-extinction". And "compared to the the MAC-v1..."
with "than the MAC-v1...." -- removes the 2nd "the" and also makes the text easier
to read.

3) Page 13, line 8 -- Again, the wording it clunky -- replace "presents the largest"
with "has highest" and delete "per units of altitude" -- readers of the manuscript
will know that aerosol extinction is defined to be in units of "per unit altitude",
so its implicit in the terminology that is the case and doesn't need to be stated here.

4) Page 13, line 14 -- insert comma between "aerosol option used" and "the shape of"

5) Page 13, line 15 -- insert comma between "large variability" and "but it also"

6) Page 17, line 14 -- change "decreases by -5 to -8%" to "decreases by 5 to 8%".
Since you've said "decreases", you don't need also to have the minus sign in the
percentage values.

7) Page 17, line 16 -- Since DRE is an established acronym (Direct Radiative Effect),
in this case where you are using an type of DRE (the clear-sky DRE), suggest to use
lower-case for the additional letter -- i.e. denote clear-sky direct radiative effect
as cDRE. It just makes it easier for the reader to scan the text and see the established
acronym also identifying the additional letter that specifies the clear-sky. Suggest
however also including lower-case "s" (as well as "c") and a hyphen, i.e. make the
terminology cs-DRE rather than CDRE. It's just that c-DRE could confuse some readers
who might think the "c" is cloudy or so, whereas "cs" is more recognisably clear-sky.
The "CDRE" also is potentially making the reader wonder if there is an existing acronym
CDR that it's referring to. Overall, it's just much easier then to identify the "DRE"
part of the acronym as the primary acronym when you put c-DRE or better cs-DRE.
If you agree, please replace all "CDRE" with "cs-DRE".

8) Page 17, line 17 -- replace "and CON" with "and the control (CON)" -- it's just then
a more understandable sentence -- and also the control is not really an experiment
so it's different to the other model runs where you give the acronym -- there is only
one control run, so you can just say "the control".

9) Page 19, lines 6-7 -- re-word "a part of it transforms into diffuse radiation and
therefore increases diffuse radiation amount", replacing the last part with ".. and
therefore increases diffuse radiation" or "increases the diffuse radiation component"

10) Page 19, lines 7-8 -- Improve the way this sentence is written, reduce the current
"Thus diffuse radiation at the surface (DIF) is consistently increased in all simulations,
with the exception of ARI_Mv1urban due to a general decrease in cloud fraction amount
seen in this simulation" to instead say "As expected, this effect causes an increase in
diffuse radiation in almost all simulations, the exception being the ARI_Mv1urban simulation
which has a large decrease in cloud fraction (see Figure 6)."

11) Page 20, line 6 -- In your revisions you've here replaced "could potentially
modify this effect" with "could potentially modify this cyclonic anomaly". I suggest
here you refer specifically to this being a "cyclonic anomaly effect" -- i.e. add
"effect" after "modify this cyclonic anomaly".

12) Page 20, lines 6-7 -- I think the "cyclonic anomaly effect" you are explaining in
this subsection is an example of a broader class of "circulation effects" or
"aerosol-circulation effects", for example the effects of aerosols on the South Asian monsoon
(e.g. Ganguly et al., 2012; Bollasina et al., 2014). With such monsoon systems dominant
seasonal influence within the regional's weather and climate, those aerosol-circulation
effects are well recognised, but it sounds like here you are identifying there may be
another aerosol-circulation effect for Europe in relation to the influence on this cyclonic
anomaly. Suggest modifiying this last sentence from "Therefore, it would be interesting..."
instead to note this broader context, perhaps something like "The influence of aerosols
on the South Asian monsoon is well recognised (Ganguly et al., 2012; Bollasina et al., 2014)
and it would be interesting to explore whether this cyclonic anomaly effect might also be
an aerosol-circulation effect important for European weather and climate."

13) Page 20, line 15 -- replace "which are mostly affected" with "which are most affected".

14) Page 20, lines 16-17 -- replace "our aerosol concentrations" with "the specified aerosol
concentrations".

15) Page 20, line 21 -- replace "the aerosol related change" with "the aerosol-related change".

16) Page 24, line 14 -- re-word "where the indirect effect is also present" -- I'm not sure if
here you're referring to model simulations that switch on or off the cloud-indirect effects,
or if you're drawing a distinction between different regions, where aerosol-cloud interaction
effects may be a larger proportion of the overall aerosol radiative effects. Certainly you
need to replace "the indirect effect" with "aerosol-cloud interaction effects". You've given
the correct aerosol-radiation effect terminology at the start of the sentence (rather than
the older "direct effect" terminology) -- and you need also to replace "indirect effect" with
"aerosol-cloud interaction effect" here. If you mean to draw a distinction between different
regions, you could replace "in an environment" with "in regions where" and replace "is also present"
with "are also important". Or if you mean model simulations -- then replace "in an environment"
with "in general circulation model simulations" and replace "is also present" with
"are also represented".

17) Page 24, line 14 -- replace "behavior" (American English) with "behaviour" (British/Commonwealth English).

18) Page 30, line 9 -- add comma after "In this study" and replace "we explore the" with
"we have explored the" -- it needs to be in past tense in the conclusions.

19) Page 31, line 11 -- re-word "Clouds responded (semi-direct effect) by letting more radiation to reach",
joining this up with the previous sentence explaining about the effects of absorbing aerosol.
Suggest to either delete "(i.e. urban)" or if you mean the actual urban simulation in the paper,
state this instead as "(here in the simulations with "urban" aerosol type)" and continue the
sentence with a comma, then to continue also explaining it's a reduction in cloud as
", with a reducing cloud-fraction response via semi-direct effect, with more radiation reaching...".
That then reads much better -- the phrase "by letting" somehow implies it is a choice, when in fact
it is simply the way that system responds.

20) Page 31, line 15 -- give a citation for the semi-direct effect -- e.g. Johnson et al. (2004),
Allen et al. (2019) -- and also use the term "aerosol-cloud semi-direct effect" throughout
the paper rather than just "semi-direct effect".

21) Page 31, line 21 -- replace "domain averaged cooling" with "domain-averaged cooling".

22) Page 31, line 26 -- replace "we also show that" with "we have also shown that".

23) Page 31, line 31 -- replace "domain averaged precipitation" with "domain-averaged precipitation".

24) Page 31, line 33 -- insert commas before "investigating" and and after "interactions".

25) Page 31, line 33 -- replace "presented a clear precipitation reduction" with "found a precipitation reduction"

26) Page 31, line 34 -- insert commas between "seasons" and "due to" and between "of SST" and "which in turn".

27) Page 31, line 34 -- delete "finally".

28) Page 32, line 3 -- insert comma after "highly absorbing aerosols".

29) Page 32, line 4 -- replace "Concluding, ..." with "Overall, our study finds..."

References
----------


Allen, R. J., Amiri-Farahani, A., Lamarque, J.-F. et al. (2019)
"Observationally constrained aerosol-cloud semi-direct effects"
Climate and Atmospheric Science, 2:16, https://doi.org/10.1038/s41612-019-0073-9

Bollasina, M, Ming, Y, Ramaswamy, V, Schwarzkopf, MD & Naik, V (2014):
"Contribution of local and remote anthropogenic aerosols to the 20th century
weakening of the South Asian monsoon", Geophysical Research Letters, vol. 41,
no. 2, pp. 680-687. https://doi.org/10.1002/2013GL058183.

Ganguly, D., Rasch, P. J., Wang, H. and Yoon, J.-H. (2012)
"Climate response of the South Asian monsoon system to anthropogenic aerosols"
J. Geophys. Res., vol. 117, D13209, doi:10.1029/2012JD017508.

Johnson, B. T., Shine, K. P. and Forster, P. M.
"The semi-direct effect: Impact of absorbing aerosols on marine stratocumulus"
Q. J. Roy. Meteorol. Soc., vol. 130, pp. 1407-1422, doi:10.1256/qj.03.61