Ice-nucleating particles in precipitation  samples from the Texas Panhandle

Vepuri, Hemanth S. K.; Rodriguez, Cheyanne A.; Georgakopoulos, Dimitrios G.; Hume, Dustin; Webb, James; Mayer, Gregory D.; Hiranuma, Naruki

doi:https://doi.org/10.5194/acp-21-4503-2021

Articles | Volume 21, issue 6

https://doi.org/10.5194/acp-21-4503-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-21-4503-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 6

Research article

|

24 Mar 2021

Research article |

| 24 Mar 2021

Ice-nucleating particles in precipitation samples from the Texas Panhandle

Hemanth S. K. Vepuri, Cheyanne A. Rodriguez, Dimitrios G. Georgakopoulos, Dustin Hume, James Webb, Gregory D. Mayer, and Naruki Hiranuma

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Final revised paper (published on 24 Mar 2021)
Supplement to the final revised paper
Preprint (discussion started on 14 Sep 2020)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'comments', Anonymous Referee #1, 02 Oct 2020
- AC1: 'Vepuri_et_al_PCPT_AC_Ref_1', Naruki Hiranuma, 22 Dec 2020
RC2: 'Review of Vepuri et al.', Anonymous Referee #2, 14 Oct 2020
- AC2: 'Vepuri_et_al_PCPT_AC_Ref_2', Naruki Hiranuma, 22 Dec 2020
RC3: 'review', Anonymous Referee #3, 20 Oct 2020
- AC3: 'Vepuri_et_al_PCPT_AC_Ref_3', Naruki Hiranuma, 22 Dec 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Naruki Hiranuma on behalf of the Authors (22 Dec 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (16 Jan 2021) by Susannah Burrows

RR by Anonymous Referee #1 (22 Jan 2021)

Suggestions for revision or reasons for rejection

General comments

Concerns I had raised in my earlier review were taken seriously. The manuscript is is better shape now than initially. Still, there are numerous issues left to solve before it might be in a form where it can recommended for publication. I have to say that my earlier review did not address all issues in detail because the manuscript seemed to require more than one iteration anyway, initially a coarse one and then one to solve remaining intermediate and minor issues.

My main concern with the revised manuscript is its still insufficient focus. It should focus on the immediate objective of the study and the progress made towards achieving it. New insights generated by the study is what the reader is interested in. Currently, these insights are diluted with lengthy explanations of general issues that are well known to most of those who chose to read papers on ice-nucleating particles. For readers, who are not yet familiar with INPs, there are numerous excellent review papers available for a general introduction. I see no need for explaining in the Introduction sections of a specific study in detail what INPs are or why immersion freezing is important. Also section 2.5 can be shortened substantially. I would not call it "IN Parameterization" because what the section describes is the estimation of INP concentration in cloud volume from INP concentration measured in precipitation samples.

If I was to revise the manuscript, I would start with Section 1.4, Study Objectives. This section summarises what has been done (not necessary in such a section), but does not convincingly state why it has been done. The only statement somewhat pointing in such a direction needs to be specified ("...help understanding of ambient INPs in the West Texas region..."). Perhaps it means something similar to: "...to understand whether the high density of animals on dusty ground in large feed yards (feedlot), which are typical for Western Texas, has a discernible impact on regional atmospheric INP concentration and composition near the gound and in clouds." If this was indeed the objective, it should be introduced by a short description of feedlot operations, the extent of these operations in terms on number of animals and their spatial extent in Western Texas to give the reader a flavour of these features in the landscape. In most other regions of the world feedlot operations of that kind are unknown. Once the objective is clear, all other changes to the manuscript follow naturally from that point onwards. As I am not sure whether my idea of the specific objective of this study is correct, it makes little sense for me to datail all changes that would follow.

Other comments

Line 17: Please specify that "nINP" stands for INP concentration in air.

Lines 78 to 82: I do not understand the argument. There is a high number concentration of INPs (up to 20'000 per litre) and at the same time there are liquid droplets. Why should this be an argument for immersion freezing to be important? If it had happened in these clouds, there would have been up to 20'000 ice crystals formed per litre and the clouds would quickly have completely glaciated, so liquid droplets would not have been observed.

Line 92: What is an "INP episode"?

Lines 98 to 100: Do you mean "...have shown that the addition of INPs at the base of warm clouds would result in stronger updrafts and lead to increased amounts of precipitation..."?

Line 121: "studied" or "compared"?

Line 123: What is "bio-speciation"?

Line 263/264: What are the feedlot samples, airborne dust collected next to a feedlot or soil samples taken from the surface of a feedlot?

Line 267: "tornado warning", not "tornado warming"

Lines 218 to 220: I do not understand why in the case of overlapping INP spectra those with the "lower nINP values" were taken for merging when they had the "lowest confidence intervals". Did you mean "lower uncertainty"?

Line 229: Please say what "CINP" stands for.

Line 239: What is a "factor of few more"?

Line 346: A standard deviation that is larger than the mean implies that there is a substantial fraction of data with negative values. This is not possible when the unit of the data is mass per volume. Most likely, the data does not have a normal, but a log-normal distribution. If so, it should be treated and reported accordingly (cf. Limpert et al, 2001, https://doi.org/10.1641/0006-3568(2001)051[0341:LNDATS]2.0.CO;2, or Limpert et al., 2008, DOI 10.1007/s10453-008-9092-4)

Lines 350 to 362: A range of potential sources of particulate matter in the sampled air are discussed, but why not soil dust from feedlot? I thought this study intends to understand the possible impact of this source on regional INP concentrations in air and precipitation (or clouds)?

Line 367: What do you mean with "surface material rupture"?

Section 3.4: Here, I am missing a discussion of the results of the present study in a wider context. There have been others, who analysed the microbiome of precipitation samples (e.g. Woo and Yamamoto, 2020, https://doi.org/10.1186/s40793-020-00369-4). How do their results compare to your results. Is there much similarity? Are there major differences, perhaps pointing at the influence of dust from feedlot operations? I am not expecting a list of names and percentages of microorganisms found in numberous other places ot the world, but a discussion focused on what I presume is the aim of your study: do feedlot operations affect what is found in terms of microorganisms and INPs in air and precipitation in Western Texas.

Line 460: I do not understand the statement in brackets: Did the back-trajectories show a possible marine influence or not?

Line 459: What was the limit of detection again?

Section 4. Conclusion: The first paragraph (lines 510 to 533) is a summary of results and only the second, much shorter paragraph contains conclusions. I would suggest to shorten the first and to strengthen the second paragraph.

Lines 514 to 515: Is it not self-evident that severe precipitation has the highest rainfall intensity? It is measured rainfall intensity that leads to the categorisation of an event as severe rainfall. Or, was there any other criteria for that category?

Table 1: Are the PM really reliable to a precision of 1 ng/m3? If not, reduce the number of digits.

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RR by Anonymous Referee #3 (25 Jan 2021)

ED: Publish subject to minor revisions (review by editor) (06 Feb 2021) by Susannah Burrows

AR by Naruki Hiranuma on behalf of the Authors (16 Feb 2021) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (16 Feb 2021) by Susannah Burrows

AR by Naruki Hiranuma on behalf of the Authors (17 Feb 2021) Author's response Manuscript

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Short summary

Due to a high frequency of storm events, West Texas is an ideal location to study ice-nucleating particles (INPs) in severe precipitation. Our results present that cumulative INP concentration in our precipitation samples below −20 °C could be high in the samples collected while observing > 10 mm h⁻¹ precipitation with notably large hydrometeor sizes and an implication of cattle feedyard bacteria inclusion. Marine bacteria were found in a subset of our precipitation and cattle feedyard samples.