Topical Editor review of "Incorporation of aerosols into the COSPv2 satellite
lidar simulator for climatea model evaluation", by Marine Bonazzola et al.

This manuscript describes the incorporation and testing of a "lidar simulator"
module within the CF-MIP Observation Simulation Package (COSP), progressing
the existing COSP concept to additionally enable General Circulation Model
to evaluate simulated aerosol profiles, compared to the extensive information
gathered from satellite-borne lidar measurements such as CALIOP.

Two reviewers have provided reviews on the submitted manuscript, both confirming
the manuscript to be within scope for publication in GMD. The reviewers have
provided a set of minor revisions, mainly aimed at improving the manuscript's
communication of the necessarily quite-complicated specifics of the sampling
and aerosol attenuation calculations that enable a General Circulation Model's
simulated aerosols to be evaluated consistently with that observed from
space-borne lidar.

The authors have replied to each of the reviewer comments, and made appropriate
revisions to the text, and the manuscript is improved as a result, now close to
being ready for publication in GMD.

From reading the track-changes manuscript, I noticed however that there are still
quite a few places where the wording could still be improved, and have provided
below a pre-final list of minor revisions to further sharpen up the text.

The only 1 of these revisions that requires some explanation, is in relation to
the text in the revised manuscipt still tending to refer to "CALIPSO" when it
should refer to "CALIOP". If the text is referring to a satellite orbit, then
it is correct to refer to "CALIPSO", since this is the name of the satellite.
But there are multiple cases where the text refers to "CALIPSO data", when
this should be clear it's the data from the CALIOP lidar instrument, that
being only one of the instruments on the CALIPSO satellite.

The acronym CALIPSO stands for "Cloud-Aerosol Lidar and Infrared Pathfinder
Satellite Observation", and in addition to the CALIOP cloud-aerosol lidar,
the CALIPSO satellite also hosts for example an imaging infra-red radiometer
to measure cirrus cloud emissivity and particle size (see for example the
information here https://calipso.cnes.fr/en/CALIPSO/GP_iir.htm).

In my initial Topical Editor review, I corrected some of the instances where
the term CALIPSO was used when CALIOP should have been stated. But it's clear
that the revised manuscript, including in the Observation section (lines 18
to 40 of page 8 of the author track-changes manuscript), the text still refers
to CALIPSO, when it is referring to the CALIOP lidar (on the CALIPSO satellite).

The other minor revisions refer to improving the initial sentences of the
Abstract, some parts of the Introduction and to improve the new Table 1 (page 7
of the ATC-manuscript) the authors added to explain the sub-scripts 1, 2, 3 and 4
in the variable names used in the code, as requested by reviewer 1.

Once the authors have revised the manuscript to address these remaining minor
issues, the manuscript can then proceed to publication in GMD.

Remaining minor revisions
-------------------------

1) Abstract, lines 1 & 2 -- the authors have addressed reviewer 2's request to change
the term "aerosols" instead to "aerosol", but the grammar of the sentence from the
plural "aerosols" now does not read correctly with the change to simply "aerosol".

Whilst reviewer 2 was correct to request this change (avoiding the term "aerosols"),
the sentence should also be adapted to be correct for the new singular word, even
though technically the word "aerosol" can be considered to refer to different types
of aerosol with the aerosol.

To further clarify the issue, my recommended change here is to, for this initial
overarching sentence, add also the word "atmospheric" prior to "aerosol".

I'm also requesting, considering the size distribution of the particles is one aspect
pf the science related to the lidar emulator, to avoid the word "large" in this
context of the magnitude of the impacts on climate, suggesting to refer instead
to "substantial impacts".

The requested change then, is to replace the current text "Aerosol have a large impact
on climate, air quality and biogeochemical cycles" instead with "The atmospheric
aerosol has substantial impacts on climate, air quality and biogeochemical cycles".

I am also suggesting to make the current very short 2nd sentence instead be a
continuation of this short first sentence, changing ". Their concentrations are..."
instead to ", and its concentrations are...".

With both of those changes, the recommendation is to make the first sentence of the
Abstract be, "The atmospheric aerosol has substantial impacts on climate, air quality
and biogeochemical cycles, and its concentrations are highly variable in space and time."

2) Abstract lines 2 to 3 -- using a possessive determiner such as "their" is not really
appropriate in this formal scientific context, particularly in these initial sentences
of the Abstract. In changing the wording, I'm requesting to make this 2nd sentence
start to refer to the simulation of aerosol in models, this being the main application
within the manuscript's topic.

Request to change

"A key variability is in their vertical distribution, because it influences..."

instead to

"A key variability to evaluate within models that simulate aerosol is the
vertical distribution, this influencing..."

3) Abstract, lines 3 to 4 -- the text correctly points out the vertical distribution
influences atmopsheric heating profiles and aerosol-cloud interactions, but continuing
also to "aerosol lifetime" is not correct with that sentence construction. The sentence
then refers to the vertical profile having an influence on aerosol lifetime, but it's
rather that the vertical profile is indicative of a particular aerosol lifetime.
I'd also advise to use the term "residence time" rather than "lifetime".

The end of this sentence also needs re-wording because the "as a result" is not quite
correct either, since aerosol concentations at the surface are probably less affected
by residence time than those aloft -- so the surface concentrations are not really the
correct aspect to refer to in relation to changes in aerosol lifetime/residence-time.

My suggestion here is to have the text refer to changes in the lifetime affecting the
strength of the effects referred to in the 1st sentence.

And the specific suggested re-wording is then to change

", aerosol-cloud interactions, aerosol lifetime and, as a result, surface concentrations"

instead to

"and aerosol-cloud interactions, to help constrain aerosol residence time, to better
represent the magnitude of simulated impacts."

4) Introduction, page 2 lines 36 to 39 -- I do not understand why the authors have chosen
to talk about these specifics for configuring a general circulation model: nudging,
fixed sea-surface temperatures or interactive ocean. Firstly the nudging capability
within a model does not preclude it from having fixed sea-surface temperatures, so
the text is not quite right where it refers to these as different configurations.
Secondly, and most importantly, this referring to these different configurations of a
general circulation model is irrelevant to the description of the lidar emulator described
in the manuscript, and including this only serves to divert the focus of the reader.

Including some discussion on page 3 from lines 1 to 9 is OK, but constructing these
in this way suggests they are alternative configurations, which is not the case,
(tha nudging to re-analysis can be applied whether the model is using fixed SST or
coupled to an interactive ocean).

Having this single-sentence paragraph on lines 36 to 39 will also seem strange when the
accepted manuscript is type-set, and my suggestion here is to delete the text on
lines 37-39 of page 2 of the revised manuscript. And instead have the re-worded sentence
be the 1st sentence of the next paragraph, i.e. join up with the text on line 41.

Referring to "the closer bridge between observations and models" I'm suggesting should
instead have the re-worded sentence refer to the observational constraints the
satellite lidar measurements provide.

Specfically, I suggest to re-word the current sentence starting on line 36 instead to
"These studies point to the potential for satellite lidars to provide important
constraints for the aerosol distributions in climate models, of benefit to a range
of different configurations."

5) Introduction, page 2 line 41 -- with the lines 36-39 reworded to the shorter
sentence above, and now referring to constraints, delete "the constraints of"
from this sentence, changing the start of the sentence from "First, the constraints
of 15 years of ..." instead to "The 15-year record of..."
Further to my general comments above, it's important to be clear here that CALIOP is the
name of the lidar, and CALIPSO is the name of the satellite.
And with that re-wording, insert "the space-borne CALIOP lidar on" after "15-year record of",
and insert "satellite" after "Satellite Obervations (CALIPSO)".
The current sentence is already a bit too long, and then with making the wording clarify
this common misunderstanding of CALIPSO being the name of the lidar, the suggested
re-wording is to split this into 2 sentences, the first reading:

"There is now a 15-year record of the space-borne CALIOP lidar on the Cloud-Aerosol Lidar
and Infrared Pathfinder Satellite Observations (CALIPSO) satellite (2016-2020)."

The second sentence can then refer to the utility of this re: the evaluating transport
and removal processes in models, changing the wording then to continue after that, as:

"In evaluating the simulated vertical aerosol distribution, these measurements can provide
important observational constraints to improve transport and removal processes in models."

And then change ", when those observations are.." instead to re-start another new sentence,
adding "satellite lidar" there -- i.e. "When the satellite lidar observations are..."

6) Introduction, page 3, line 33 -- Change the "within the COSPv2 to leverage.."
instead to "within the COSPv2 software package to leverage.." and change to past tense
(since that is already done) -- then "We choose to implement" instead written as
"We have chosen to implement...." -- it's just easier for the reader to appreciate
what the sentence is aiming to communicate there.

7) Section 2.1, line 9 -- the justification here of the text is incorrect, please
correct this so that it does not stretch the text to the end of the line.

8) Section 2.1, lines 21-22 -- change "which determines the refractive index of
the medium" instead to "the latter determining its refractive index."

9) Section 2.1, lines 12-14 -- This sentence needs to be clearer here, please re-word
the current "The optical properties computed by the GCM can be directly the extinction
and 180o backscatter..." instead to "The aerosol optical properties computed in GCMs
varies, with some models having diagnostics for single-wavelength extinction and
180o backscatter...".

Suggest to have this sentence continue to the key difference, that some models don't
calculate these -- calculating only the waveband-integrated optical properties
(extinction, absorption and phase function). Note that the current text refers to
both "absorption" and "single-scattering albedo" but those are just different measures
of essentially the same property.

In summary, the correction is to change the current sentence

"The aerosol optics diagnostics in GCMs vary, with some models computing
single-wavelength extinction and 180o backscatter, whilst others
calculate only the waveband-integrated aerosol optical properties
(i.e. extinction, absorption and phase function).

With that re-wording the existing wording " which can be used to compute the ATB"
can be deleted.

10) Section 2.2, page 5, lines 17-19 -- Replace "at a given wavelength:" with "monochromatically
(i.e. at specific wavelengths):" and replace ", which are typical outputs" instead
with ", these being standard wavelengths". On lines 21, also change "may also" to
"could also", and delete "inputs for".

11) Section 2.2, page 5, lines 23-24 -- I do not understand why this sentence
has been added here. Is this sentence referring to an example in the code?

In my opinion this is not so relevant to the GMD article, and I would actually
suggest to delete this sentence altogether. Or if this is referring to the
data shown in the Figure, please integrate "shown in Figure 2" or similar
into the sentence.

12) Page 7, Table 1 -- There needs to be text added to an upper row of the Table
to explain what is shown in each of the columns in the Table.

For example in the far-left column in new upper row, the text needs to state
"Variable sub-script in article" or similar, with the 2nd-from-the-left
stating "Description of variable" or similar. These 2 labels could be added
in the existing upper row (in the far-left and 2nd-from-left boxes that
are currently blank). But there does need to be a new upper-row added
at the top of the Table, and suggest to have a banner stretching across
the 3 right-hand columns stating "Name of variable in code", or if there
is space (which there should be, with stretching across those 3 columns)
"Name of variable in lidar simulator code".

Please change "Correspondence between.." instead to "Translations between.."
and also correct the typo in the caption to the Table, at the far-right
end of the 1st line (change "FOr" (or is it "F0r"?) instead to "For").

13) Page 8 -- this is where I found several instances of "CALIPSO" that
should be stated as "CALIOP" when referring to the measurements, or
to the instrument.

13.1) Page 8, line 4, change "CALIPSO" to "CALIOP"

13.2) Page 8, line 7, change "CALIPSO" to "CALIOP"

13.3) Page 8, line 22, change "CALIPSO" to "CALIOP"

13.4) Page 8, line 23, change "CALIPSO" to "CALIOP"

13.5) Page 8, line 26, change "CALIPSO" to "CALIOP"

13.6) Page 8, line 28, change the two instances of "CALIPSO" both to "CALIOP"

14) Page 8, line 35, change "As each" to "Since each"

15) Page 8, line 39, change "simulations, to identify" to "simulations, then able to detect".

16) Page 9, lines 1-6 -- the new text added here is not clear enough re: this gridded
data product -- this is an "example gridded data product", right?

16.1) Page 16, line 1 -- change "a gridded" to "an example gridded"

16.2) Page 16, line 1 -- add a comma after "consisitent with the GCM grid"

16.3) Page 16, line 2 -- change "the model and the simulator results can" instead to
"the translation from the model to the simulator results can"

16.4) Page 16, line 2 -- change "be evaluated against the observational data" instead to
"be more easily understood by the reader, in relation to how it can affect the
interpretation of an comparison to the CALIOP observation profile".

The authors have replied to each of the revisions in my final Topical Editor review, and have
implemented each of the suggested minor revisions (except for one which they replied to
explain why they have preferred to keep the wording there).

And I confirm that, following these minor wording improvements, I am recommending to
publish "as is" in this manuscript version 5.