|Review of “Ice-nucleating particles from open-lot livestock facilities in Texas” by Hiranuma et al.|
This is a valuable contribution to the ice nucleation community and it has a good level of novelty. This is the first time that I reviewed this manuscript and given that this was the second round of revisions I was expecting to see a more readable, clean, and concise document. Although the incorporated changes improved the manuscript, it cannot be accepted in its current verison. I invite the authors to take into account the comment by original reviewer #2 “I do not wish to spend a great deal of time going from line to line trying to edit the manuscript for them”.
The authors wanted to cover too much: i) field (annual trends, seasonal trends, downwind vs, upwind); ii) field vs. lab; iii) lab (heat vs. no heat, super micron vs. sub micron, bulk vs. filter, ); iv) intercomparison between 4 different instruments; and v) a parametrization. Although it is not bad at all to be ambitious and to report several measurements/observations, the authors need to combine the large amount of data into something that is easy to read and to follow.
Given that the samples were found to be heat insensitive, the IN properties are likely coming from the mineral components. Why the mineralogical composition is not reported. In lines 110-112 it is stated “However, our knowledge regarding what particular features of OLLF dust trigger immersion freezing at heterogeneous freezing temperatures (Ts; i.e., size vs. composition) is still lacking”. The authors focused on the size of the particles but in terms of composition the minerals are completely ignored.
This is the second round of revisions and the manuscript still needs to be edited to improve its readability and the language. I was expecting to see a cleaner version.
Lines 367-368 it is mentioned that “These results imply the following: (1) ambient meteorological conditions, as summarized in Table 1, might not be determining factors for nINP for our study sites”. This refers to RH, T and P but not to wind speed, one of the most important meteorological variables to resuspend dust particles. Why is wind speed and wind direction not reported?
Lines 417-418 and Line 524: “For each sample, the spectra nearly overlap each other at T ~ -25 °C, verifying their comparability and complementing features.” and “Upon confirmation of the comparability between field and lab ns,geo values”. Why is this overlap only true at -25C and not at other temperatures? obtaining similar results at this temperature is enough to conclude that the systems are really comparable. Is it not the overlap at -25C suspicious? Why should they be comparable? In the field, aerosol particles are naturally aerosolized and this resuspension from the ground can favor specific aerosol sizes. On the other hand, the aerosolization in the laboratory is mechanical and the particles sizes, and hence, their composition may significantly differ from those found in natural environments.
Lines 438-441: The authors need to show that the composition and particle size distribution of ambient and Laboratory particles are comparable.
The Abstract is extremely long. The authors need to shorten it focusing on the main results only.
Similar to the Abstract, several parts in the Results section (and along the manuscript) are repetitive, longer than needed and not very concrete. The manuscript needs to be further edited to improve its readability.
Avoid self citations. From my personal point of view this is excessive.
Move sections 3.3 and 3.4 to SI as they contribute little to the main text.
The use of “T” and “Ts” instead of “temperature” and “temperatures” add too much noise to the manuscript.
Lines 66-67: “(i.e., the freezing propensity of INP immersed in supercooled water)”. Who freezes the INP or the droplet?
Lines 95-96: How about convection?
Line 99: “where a convective cloud and updraft system persists”. What does it mean? that you have such a system 365 days per year?
Lines 115-118: This is not the right place. Please add this text earlier.
Section 2.2. This Section is not easy to follow. It is longer than needed and it has to be rewritten to be more concise and clear.
Lines 154-155: Add the depth and how were they collected?
Line 186: How about wind speed?
Line 345: “Even assuming we evaluate INP up to 2,000 L-1, our INP fraction is 1%. Thus, our ns parameterization is reasonable.” I don’t get the message here.
Line2 354, 374 and 375: “cumulative mass”, “cumulative PM mass”, and “aerosol particle mass”. What does it mean? In methods two different systems to measure PM10 were described. Do the authors refer to PM10?
Lines 363-364: “However, because the measured nINP is low at high T, the CI95% error of nINP,upwind at around -15 °C is relatively large as compared to that at a lower T (Fig. 3a)”. I do not get it.
Line 366: “on local meteorological conditions”. What was the typical wind speed?
Line 367: “short episode of soil dust”. What do the authors mean? Resuspended dust?
Lines 388.389: “This motivates the need for further characterization of our OLLF samples in a controlled-lab setting in order to identify what particulate size population (i.e., supermicron vs. submicron) and other properties trigger their”. This cannot be evaluated in the field? should not just simply change the cut-off of the filter sampling PM1.0 vs. PM10?
Lines 399-410: This belongs to methods. Most of this information is already known from previous experiments in the AIDA, and therefore, their contribution to the manuscript is little and should not be in this section.
Lines 420-421: “the INSEKT results suggest that the bulk TXD01 sample is more active than filter-collected samples”. Is this not expected as the bulk likely contain larger particles?
Lines 424-425: “the lab-derived immersion spectra of both surface materials are reasonably comparable to the minimum – maximum boundaries of our field ns,geo spectra for T > -25 °C”. If it is the same samples analyzed by different setups why should they show the large variability observed on the field samples?
Lines 424-426: WWhile the variability of ns,geo at a single T could vary several orders of magnitude, similar variations are found for both lab and field results, implying the similarity of freezing efficiencies of our lab and field samples”. This is expected for field samples as they are not identical and may have different composition, but in the laboratory, the instruments collected exactly the same samples.
Lines 427-430: “there is a difference in the INP abundance between bulk (< 75 μm-sieved) and aerosolized/filtered-samples for TXD01 (⪅ 6.5 μm; Table 3) presumably due to different properties in particles of these two size subsets (6.5 – 75 μm and ⪅ 6.5 μm) and/or different amount of IN-active soil organic matter”. Again, is this not expected?
Line 431: “be more representative of atmospherically relevant dust”. Based on what? This needs to be clearly discussed.
Line 433: “This comparability suggests that freezing ability is similar for condensation and immersion for our surface samples”. I am not sure if such a strong conclusion can be said from just 2 data points from the DFPC.
Line 569: “Our lab and field measurements-based parameterizations”. It is not clear how the laboratory results were incorporated or used into the parametrizations. As stated in Major point #5 Lab and Field data should not be combined.
Lines 643-544: “Additionally, the observed consistency in the spectral slopes (i.e., Table 5) suggests that lab and field measurements exhibit similar IN ability at examined Ts”. This was true at -25C not for the whole temperature range.
Figure 5: In x-axis is it micro or milligrams? In Table 1 it is reported in micrograms
Figure 7: it does not make sense to have a, b,c,d on each panel. The description of panels d are unclear. What is the concentration reported in red and blue?
Figure 9: Why is it that noise? What is the time resolution? Would it not be better to do at a lower time resolution to avoid the noise?
Lines 28: what is the meaning of “3 × 10-7 g L-1” .
Lines 48-51: Delete them.
Line 54: delete “chapter 9”.
Line 56: Add other references in addition to Storelvmo (2017)
Line 78: “Agricultural land use is in excess of 50% of total U.S. land use”. Please rewrite it.
Line 87: Add references after “conditions”.
Line 90: Add references after “head”.
Line 101: “we examinedthe”. Fix it.
Line 106: Add references after “materials”.
Line 125: Add references after “definition”.
Line 161: “using an offline freezing technique”. Which one?
Line 171: “those of previously measured”. Fix it.
Line 184: Remove “Fig 5.”
Lines 196-198: “proxies. We chose the AIDA chamber as our study platform because it simulates ice formation in mixed-phase clouds in a controlled setting with respect to both T (± 0.3 °C) and humidity (± 5%; Fahey et al. 2014).” Delete.
Lines 201-203: “experiment. The AIDA has been applied for the analysis of both ambient and lab-generated INPs and has facilitated characterization of many INP species with the IN efficiency uncertainty of ± 39% (Steinke et al., 2020; Ullrich et al., 2017; Niemand et al., 2012; Hoose and Möhler, 2012).” Delete.
Lines 223-225: “Another motivation for using the AIDA facility is its ice-selecting pumped counterflow virtual impactor (IS-PCVI; Hiranuma et al., 2016). As detailed in Supplemental Information (SI) Sect. S1, IS-PCVI separates ICRs from interstitial particles, including cloud droplets, at Ts below -20 °C.” Delete.
Line 225: “evaporation”. Should it be sublimation?
Line 300: “Texas dust”. Delete.
Line 310: “Next, our metagenomics analysis method of total DNA is described”. Delete.
Line 386: “at below -20 °C”. Fix it.
Lines 386-387: “ambient aerosol particle mass concentrations based”. PM10?
Line 389: “in a controlled lab setting”. Delete.
Line 412: “O14, S16, S20”. Add the origin/source of the samples.
Line 472: Add references after “mass”.
Lines 486-487: “properties. All of our single particle analyses were carried out with the following parameters: electron beam accelerating voltages of 15 keV, spot size of 50, and working distance of 10 mm”. This belongs to Methods.
Line 525: “We elected to use the”. Fix it.
Line 529: “typically substantially lower”. Fix it.
Line 580: “atmospherically relevant”. What do the authors mean?
Line 593: “dust samplew”. Fix it.
Table 6. Last column “Spermicron Size”. Fix it.