Review of the AMT manuscript amt-2024-57

“CIAO observatory main upgrade: building up an ACTRIS compliant aerosol in-situ laboratory”

by Teresa Laurita, Alessandro Mauceri, Francesco Cardellicchio, Emilio Lapenna, Benedetto De Rosa, Serena Trippetta, Michail Mytilinaios, Davide Amodio, Aldo Giunta, Ermann Ripepi, Canio Colangelo, Nikolaos Papagiannopoulos, Francesca Morrongiello, Claudio Dema, Simone Gagliardi, Carmela Cornacchia, Rosa Maria Petracca Altieri, Aldo Amodeo, Marco Rosoldi, Donato Summa, Gelsomina Pappalardo, and Lucia Mona, 2024

The above manuscript describes the set-up and characteristics of a combined aerosol in situ and remote sensing measurement side, operated by CNR in ACTRIS. At the beginning, I had my doubts if AMT is the right place for this. But there are, at least for me, two strong arguments, why the manuscript should become an AMT publication. Firstly, for each infrastructure, a reference paper is needed, where, hopefully, all the scientific papers to come can refer to. Secondly, as the authors claim, such a paper can act as “a practical guide for implementation”, in particular for researchers in America or Asia, where ACTRIS is probably not so well known. However, to make these two arguments valid, some more detailed information must be provided that the paper can act as reference. And if it should be a practical guide for implementation, for me it is a must to give at least an overview about associated resources (time, man-power, maintenance costs, etc.), both concerning the implementation as well as for the operation later on. This would a with ACTRIS not familiar person allow to do a cost benefit analysis. It would be interesting to go further into that direction and give an estimation on how much of these stations would be needed across Europe or globally to cover the scientific needs. But this is only a nice-to-have remark, no request.

Specific remarks:

1. p. 1, l. 13: CNR, IMAA and all the other abbreviations in the manuscript. Please write the full name, when you us the acronym the first time. And as the manuscript has so many acronyms, please add a glossary.
2. p. 1. l. 18: I´m not so sure if the provided examples are examples for a “synergistic approach”, both approaches, remote sensing and in situ, a complementary and hence help each other to get the full picture. My understanding of synergy would be that a combination of these two methods provide a totally new aspect, which cannot be obtained by one method alone. But please convince me that I´m wrong.
3. p. 1 l. 28: Pöschl, 2005 reference is fine, but two decades old. Maybe add also a newer reference?
4. p. 2 l. 34: I miss the refrence to the ACTRIS BAMS  overvies paper here
5. p. 2 l. 56: the “labelling process” is well known for ACTRIS people. But already European users are unfamiliar with this, not to speak about people from other continents. As the labelling process is an important part of the data quality assurance in ACTRIS, it should be shortly described what it is for and how it works, and for the details reference should be given.
6. p. 3 l. 67: “reference observatory for atmospheric research”? Who claims this? A reference for atmospheric dynamics and ozone hole chemistry? Probably not. I can imagine that it is “a reference station for short-live atmospheric constituents in Italy and the Mediterranean”.
7. p. 3 photo: a lot of infrastructure, all of this is in situ aerosol? Better to zoom in and show the in situ aerosol containers and the inlets.
8. p. 5 l. 122: you state to list the “research lines” in the following rows here. But “development of”, “implementation of”, “harmonization of” etc. are no research lines, they are intended steps to allow your research later on. Hence the simplest way to make this consistent would be to replace “research lines” here with a more adequate wording.
9. p. 6, table 1: the list of instruments is compelling, but, as an in situ person, I would rather like to know which parameters are provided by the remote sensing devices. This would be a good suggestion anyhow, make a table providing all the remote sensing and in situ parameters at the same spot, thus the potential synergy gets more visible.
10. p. 6 l. 144: “Observational Platform” and “Exploratory Platform” are known to some of us, but not to the waste majority of the readers. Please explain shortly (in parentheses) what these terms stand for.
11. p. 6 l. 152: The description of the Central Facility part of CIAO is surely correct, but not needed for the purpose of the paper and rather confusing for the reader. Please omit this here, it is better described elsewhere.
12. p. 9. L 211.: which heads do the PMx instruments have? Please give this information.
13. p. 9 l. 218: the isokinetic flow splitter: which one did you use? Or can you provide as drawing of it?
14. p. 9 l. 219: I have some experience with sampling lines, but I only can guess the argument of the sharp tube ends, please be more specific.
15. p. 9 table 2: first of all, the two first Reynolds numbers are equal, even if the flow rate is different. The upper one is wrong in my opinion. Same for the speed there.
    
    To get a feeling about the sampling lines could you please add line length and number of bends?
16. p. 10 l. 228: for me one of the most critical points. Knowing from the literature and also from own experience, conductive “plastic” tubes can be critical, both concerning particle losses as well as chemical composition. The chosen tube MIGHT be OK, but please either provide a reference for that or provide own measurement data e. g. on the size-resolved particle transmission. Otherwise all your data are always “conditionally” correct only.
17. p. 10 l. 232: the Nafion dryer, which one? Please provide reference or explain, what this is
18. p. 10 l. 240: why is the 2:1 flow ratio desired, please explain
19. p. 13 l. 317: “unattended measurements … on the timescale of years” is an overstatement, you have to check the instruments regularly, even if they might be OK for one or the other year (which I personally doubt). Please soften this statement.
20. p. 13 l. 338: the statement that Potenza is a rural site is a trivial statement, please remove or phrase differently, what you want to highlight
21. p. 15 l. 366: in the manuscript, I miss some more evaluation data, checking the consistence of the measurements e.g. here, how good the mass measurements of the different instruments agree with the size distribution derived mass etc.
22. p. 15 l. 370ff: The elemental analysis, what is given in ACTRIS there or is this just an add-on to the in situ aerosol particle properties?
23. p. 17 l. 433: the three cases: I believe I understood what the authors wanted to show here, but I have the feeling that most of the statements can be already given with only one of the two methods, in situ and remote. I do not see the real synergy. This would be the case, at least for me, if you would use in situ and remote sensing data to generate another data product. Please elaborate a little bit more on that section, otherwise you weaken your own argument that collocated measurements are valuable. At the same time please shorten the section, there is too much “text book” knowledge in.
    
    Moreover, I believe modelling could strongly benefit from collocated in situ and remote sensing measurements, but this is not addressed in the manuscript.
24. p. 24. l. 620: the conclusion is not a conclusion, it is mainly written as outlook. Outlook is fine in at the end of the conclusion, but should not cover the major part of the text. Hence please rephrase the conclusions. Therefore imagine, e.g. the three most important statements the reader should have learned reading your paper.

Technical corrections:

1. p. 1, title: isn´t it “building-up” with a hyphen?
2. p. 1 l. 21: not sure if “container organization” does fit in here, “container layout” sounds better. Also “optimization” should be deleted in l. 22 in order to make the list more homogeneous.
3. p. 1 l. 26: might sound nitpicking but I believe it is important to state “aerosol particle” or “particle” everywhere, where the particles are meant, and not “aerosol”, which are the particles and the surrounding gas. Please check this in the whole manuscript.
4. p. 2 l. 33: Please add “The” before “Aerosol Clouds and Tr….”
5. p. 2 l. 45: here CNR-IMAA has a hyphen, on page one not. Please be consistent.
6. p. 4 wind rose: you might have used all the wind speed classes shown in the legend, but in practical, only winds up to 10 m/ show up. Hence make the higher wind speed classes just one additional “ and larger” bin. This also prevents that the same color shows up more than once in the legend.
7. p. 5 l. 95: either “Small and Medium-sized Enterprises” or “small and medium-sized enterprises” but not a mixture of both small and capital letters.
8. p. 5 l. 98: delete the “and”, because there still follows the “or” in the list
9. p. 5 l. 98: please make it either “to contribute instruments,” or “to contribute to the instrumentation,”
10. p. 5 l. 100: please exchange “revolve around” with “evolved within”
11. p. 5 l. 104: please exchange “measurements” with “data”, because you provide the quality-assured data for the satellite validation.
12. p. 5 l. 114: please exchange “smokes” with “smoke plumes”
13. p. 6 l. 128: please add an “and “ before “ i)”
14. p. 6, table 1.: “lidar and optical laboratories” are infrastructure, no “instrument” as stated in the table caption.
15. p. 6 l. 149: I learned that there should always be a space between the number and the unit, i. e. should be “20 km” here. (Only exception “10°C”). Please check the whole manuscript.
16. p. 7 l. 152: should be “Central Facilities” starting with capital letters. Please check the whole manuscript.
17. p. 8 l. 199: please make it either “particulate matter collected on filters.” or “aerosol particles collected on filters.”
18. p. 8 Fig. 4 caption: please add “aerosol” before “facility”
19. p. 9 l. 206/209: please exchange “under” with “downstream”, because that is meant
20. p. 9 l. 208: please move the comma after “3938” and remove the hyphen to be consistent
21. p. 9 Fig. 4: please add the information of the inlet heads also to the PMx instruments
22. p. 10 l. 244: please exchange “Instead” with “In contrast”
23. p. 10 l. 244: please move the “since …” half sentence to the end of the sentence, the subject and the verb should not be separated.
24. p. 11 l. 250: please exchange “input” with “inflow”
25. p. 11 l. 259: please add “matter” after “particulate”.
26. p. 12 l. 281: “human range of visibility” sounds strange for me, maybe “the visible part of the electromagnetic spectrum” is better
27. p. 13 l. 322: what is “ < ng m^-3”, please complete this equation or write it in words
28. p. 14 l. 340: please exchange “increasing” with “peaks”
29. p. 14 Fig. 7: please add “a)” and “b)” to the two rows of plots and change the figure caption accordingly
30. p. 16 l. 415: “aerosol load” is very unspecific, please use a more appropriated term for what is meant here
31. p. 17 l. 446: please exchange “in short” with “over short”
32. p. 20 l. 530/532: please remove the “%” after “BB”, same in fig. 8 b
33. p. 21 l. 553: should be “coarse” not “carse”
34. p. 25 l. 649: why some words in the “authors contribution” section are written in capital letters and others not, is not clear to me.
35. p. 25 l. 662, acknowledgement: Most of the guidelines for setting-up an in situ aerosol side in ACTRIS are given by the in situ aerosol Topical Centre. Hence, here and also in the text this TC should be acknowledged, as many years of hard work are the basis for this.

Overall 

The paper describes the CIAO laboratory that have been recently added an aerosol in-situ measurement component that is aimed to add to the ACTRIS RI in future.  

Overall, I am a bit worried if the paper is publishable in it's current shape. On the one hand there is the title stating the in-situ upgrade. That is described but ther eis as well a large portion of general description of the station that have in part already described by some papers of some of the authors.

The processes that are linked to the compliance with ACTRIS and the procedures to achive that, like "labelling" are a very specific in frame of European research infrastructures and play a minor role outside these communities. Therefore, such terms are kind of a jargon and needed some explanation, at least. 

The paper tries to fulfil AMT's requirements but that leads to a situation where the scientific strenght remains low and the bare description of a measurement station or system alone without innovation may not qualify for the journal. However, I can imagine that AMT may set rules to make descriptions of such large scale efforts and stations or systems and by that reduce the antagonistic problem these type of descriptions are causing.

Comments

page 1, line 26ff: You use the term aerosol here but actually that are the particles or the particulate matter that has these effects. It need to be changed in the whole manuscript.

page 3/4, line 74 and Fig 2: Why to use the radiosonde ground level measurement for RH ant temperature to assess ground level dewpoint temperatures? This can be done with any meteorological equipment with higherdata resolution.

page 4, fig 3: The color scheme in intervals to show also the percentage is a good idea but the color repetition and the polar plot that has its advantage in showing the wind direction makes the reading of low wind speed percentages rather complicated. Btw, the Vaisala MILOS is the data logger of the weather station if I remember well. What anemometer was used?

page 8, section 4: While the inlets are described in high detail, I didn't find the simple parameter of the inlets heights? You tell they are vertical, i.e. rooftop inlets and a height above the roof, but how heigh is that above the ground? Especially as you have a weather station there, mentioned in fig 3. 

page 9, lines 212ff: You describe here the inlet lines diameters in great detail. In the part where you describe the isokinetic splitter it remains unclear if you have one splitter with several outputs or if you use several splitters one after another? From the description this can be only guessed. 

page 9, line 219: Its not clear what you mean with sharp ends here? Their position to be right-angled (90°) in the air stream?

page 9, line 220: The statement of the sampling from the laminar main stream is, at least in engineering, a trivial statement. Do you use an off-the-shelf splitter or was it self made? 

page 9/10, table 2: The table layout is a bit awkward which is most probably due to the split over two pages and may be solved by change in the place of the table. 

page 10/11: Paragraphs on the Nafion dryer system, you discuss the drying capacities, however, did you also determine the losses in the dryer and the whole inlet line in general? E.g. Zoller et al. (2000) report for a rather similar system up to 37% losses on 10nm particles where 20% is lost in the dryer section. Do you have strategies to compensate for inevitable losses in sample lines? 

(Zoller, J., Gulden, J., Meyer, J. _et al._ Loss of Nanoparticles in a Particulate Matter Sampling System Applied for Environmental Ultrafine Particle Measurements. _Aerosol Sci Eng_ **4**, 50–63 (2020). https://doi.org/10.1007/s41810-020-00054-6)

page 16, section 5: Synergistic approach or synergy between measurement systems. The way these are described here is complementary, not synergistic. Two or more measurement systems give details on the same process and each could be used to explain the process. A synergy would create a new aspect that can not be reached by each of the methods alone. 

 Technical remarks

page 13, line 316: TOF-ACSM; I think you already introduced the manufacturer before (page 8) no need for redundant mentioning, maybe check over the manuscipt and as well for other devices. 

page 25, line 641: filed = field