the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 Mar 2025
Life cycle studies and liquid-phase characterization of Arctic mixed-phase clouds: MOSAiC 2019–2020 results
Abstract. Height-resolved monitoring of life cycles of mixed-phase clouds (MPCs) was performed in the free troposphere over the central Arctic during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition from October 2019 to September 2020. The research icebreaker Polarstern served as a platform for state-of-the-art remote sensing of aerosols and clouds. The use of the recently introduced dual field-of-view polarization lidar technique in combination with the well-established lidar-radar retrieval technique provided, for the first time, a robust instrumental basis to monitor the evolution of the liquid and the ice phase of MPCs and the interplay between the two phases. We discuss two long-lasting Arctic MPC cases observed close to the North Pole. During the late summer MPC event, most likely three gravity waves strongly disturbed the cloud evolution. We documented this perturbation in detail in terms of liquid and ice-phase properties and the recovery of the strongly disturbed liquid phase within a few hours. For the first time, cloud statistics, covering all seasons of a year, are presented for liquid-bearing stratiform clouds in the central Arctic. The focus is on the optical and microphysical properties of the liquid phase which is of key importance for a long MPC lifetime. The observations confirmed that ice formation occurs predominantly via immersion freezing. We also found that activation of aerosol particles to form droplets is of great importance for the longevity of MPCs and that the free tropospheric reservoirs of cloud-condensation nuclei and ice-nucleating particles seem to be usually well-filled.
Competing interests: Daniel A. Knopf is a member of the editorial board of Atmospheric Chemistry and Physics
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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RC1: 'Comment on egusphere-2025-967', Anonymous Referee #1, 08 Apr 2025
Review of Jimenez et al., ACPD 2025 (egusphere-2025-967)
General comments to the manuscript
In the study titled “Life cycle studies and liquid-phase characterization of Arctic mixed-phase clouds: MOSAiC 2019-2020 results” by C. Jimenez et al., the authors show results of long-term lidar-radar observations onboard the RV Polarstern during the MOSAiC cruise. Radiosonde profiles helped to interpret the data. Four detailed case studies are presented: two of them explain liquid- and ice phase retrieval results, two only liquid retrieval results. Furthermore, statistical results related to free-tropospheric stratiform liquid-containing cloud layers were presented.
Recommendation:
I would suggest the manuscript to be published after minor revisions considering the remarks below. The authors should address the following points:
General/Major comments:
Title and throughout the text: Is “life cycle studies” the most fitting term? Throughout the study it was not clear to me how the life cycle of the cloud is assessed. Firstly, for the presented statistical analysis the focus is not the life-cycle and thus it is somewhat misleading in the title? Secondly and more generally, I think the term “temporal evolution” is more fitting than life-cycle. You acknowledge on lines 344-346 that from observations at a fixed location (Eulerian perspective) it is hard to perform life cycle analysis (Lagrangian perspective) – but you don’t say how you can be sure you really do study the life-cycle as claimed. I suggest referring to the case study analysis as “temporal evolution” unless you can convincingly show that the onset/end of the observation of the cloud over RV Polarstern marks the formation/dissipation of the cloud and not the times the cloud was advected over the observatory.
Further remark on title: At the same time, “2019-2020” after “MOSAiC” can be omitted. Furthermore, in Section 5 results of “Pure liquid” clouds are presented. This should be added to the title. How about rephrasing the title to sth. like “Characterization of Arctic liquid-containing free-tropospheric clouds observed during MOSAiC”
Third remark on title: “liquid-phase characterization” is somewhat misleading: In the first two case studies, liquid- and ice phase are characterized. Why was the ice phase not characterized in the statistical analysis in Section 5? It is strange that case study analysis is done for liquid- and ice-phase but the statistics are not. Remove the ice-phase analysis in case study 1 + 2?
Section 4.3 with two more case studies comes as a surprise, as the abstract and the conclusions section mention only 2 case studies. Also, why was only the liquid phase analyzed for these case studies? What is the added value of having four instead of two case studies? – I find the two additional case studies do not add much new content to the manuscript, consider removing them.
It would be good to firstly, mention the limitations of the lidar-based retrievals more clearly (briefly done on line 317): Complete lidar attenuation at optical depth > 2.5-3 leads to underrepresentation of multilayer cloud situations.
Minor comments:
Throughout the text many facts are added in brackets – consider removing those or splitting the sentences in two to improve readability.
Line 2: Were MPC really only observed in the free troposphere during MOSAiC? – If not, please remove the “free troposphere” here and refer to it later.
Line 16-17: Is it possible to be more exact than stating “aerosol reservoirs of CCN and INP are well-filled”?
Line 53 – 69: Consider reordering/adding an introductory sentence, so that it becomes clear, that in this paper both, retrievals for liquid phase based on lidar-only observations and ice phase based on lidar-radar observations, are employed.
Line 77: Here you state the focus is on liquid-phase properties. In line 67-68 you state ice phase properties are also retrieved. – So the reader would assume the focus is on both, liquid and ice? – Clarify.
Line 92: Add that the ocean was also studied in depth during MOSAiC.
Line 96 - 101: Who is “we”? - It is very uncommon to refer to a group of co-authors as “we” and to focus the literature study on own publications that are not pertinent to the study subject of the manuscript. Consider removing reference to wildfire smoke publications. Consider merging this paragraph with the one on lines 102 – 108 and extend your references to other studies using the MOSAiC atmospheric remote-sensing instrumentation, e.g. https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2193/egusphere-2024-2193.pdf or https://acp.copernicus.org/articles/23/14521/2023/ , https://doi.org/10.1525/elementa.2021.000071 among others.
Line 120: The acronym MOSAiC has been introduced before and does not need to be explained again here.
Line 127: add “profiles of”
Line 128: “retrievals of” instead of “observations of”
Line 147: “vertical profiles” instead of “height profiles”
Line 149: Either expand on the “even” by explaining what is special about summer aerosol conditions” or remove it
Line 152: I am confused by the wording “reservoir” – Why not call it “proxy for INP concentration”?
Line 156: replace “our” by “the”
Line 157: add “troposphere”, add a sentence on why altitude ranges below 500m and above 7 km are excluded from the analysis.
Line 161: add “liquid-containing” before cloud layer
Line 172: move the “well” to the end of the sentence
Line 175, line 232, line 237 etc: “On” the order of
Line 182-183: This sounds confusing: What is the MPC top layer? Is it the liquid-containing layer? - Then you could refer to the base of it as “base of the liquid-containing layer of the MPC” instead of as “cloud base” (here and elsewhere, e.g. line 314)
Line 184: What are these virga representative for? The evolution of ice properties (e.g. IWC, ice particle effective radius) with increasing distance from the base of the liquid-containing layer is e.g. dependent on the relative humidity. – Expand/clarify.
Line 210: Are only single-layer stratiform clouds considered or also multi-layer scenarios? Why are clouds > 7 km excluded from the analysis?
Line 218: add “interpolated” to the radiosonde temperature information
Line 223: Why is a cloud still counted as the same cloud if the cloud-free gap is almost an hour? It seems like a very high allowed gap time. Please clarify.
Line 236: What is meant by “time interval of ice nucleation of 60s”?
Line 240-241: The sentence “the CCN and INP reservoirs are well-filled” is used 4 times throughout the manuscript. – I still don’t understand it. Please only this phrase once and rephrase elsewhere to give readers the chance to understand the meaning once differently expressed.
Line 227 – 242, Fig 1: You previously mention that you consider clouds with tops up to 7 km. Please motivate clearly, why you only show the particle number concentrations at 2 km height instead of at different altitudes.
Line 243: Begin what? – Consider removing the phrase.
Line 257: Is the start of the winter-time MPC Dec 30 as stated here or Dec 29 as stated on line 246?
Line 260: clarify if you mean horizontal or vertical wind velocities
Line 263: what do you mean by “a few percent of the air mass were advected from 30-60 N”?
Line 264: I suggest adding “likely” in front of “soil material” as soil moisture content also plays an important role in lifting of soil dust that is not considered
Line 310: Can you substantiate your hypothesis that riming occurred with the available observations? Also, explain how would riming lead to strong ice production?
Line 312: Substantiate your claim of homogeneously distributed ice crystals in the virgae column.
Line 321: add “lidar volume” in front of depol ratio
Line 321-324: Following your explanation in this paragraph, the low lidar volume depolarization ratios marked in green at the lower end of the virgae are caused by droplets backscattering. – Clarify/expand.
Line 332: Consider displaying the cloud radar mean Doppler velocity time-height display to see if you can identify the same virgae structure as well as cycles of up- and downdrafts (superimposed on particle fall velocity) in it. This might substantiate your hypothesis of decreased up- and downdraft strength in the later part of the case study observation as well (lines 355-359).
Line 336-337: consider discussion of the Sep 21, 2020 case study to its corresponding section. What can we learn from differing horizontal separation of the updrafts in the two considered case studies?
Line 340: What is the other measured depolarization ratio?
Line 341-343: This was mentioned earlier and can thus be removed.
Line 353-354: You attributed the enhanced ice virgae at the beginning of the observation period to potential ice seeding from the cloud above. The strong virgae extends to after when the upper left cloud was not observed anymore (until around 9 UTC). Why?
Line 364ff: Please add the definitions of the ice-phase fractions from IWC, LWC, CDNC, and ICNC. – ok, partly shown on line 401, move here at first mention
Line 38ff: To me the conclusion that a time-dependent INP activation is central for the longevity to MPC should be added to the abstract.
In the discussion of the wintertime case study (Section 4.1.), the feature at 22-23 UTC below 1 km with increased values of several parameters is not mentioned yet and should be discussed.
Line 418: 88.5°N is “near” the North Pole, not “over” the North Pole. Please correct it.
Line 420: Rephrase “the air mass came from Iceland, Greenland, northern Canada, and even from Alaska” – unclear how the same air mass can come from all of these different directions.
Line 431: Do you have a reference to substantiate your assumption of gravity wave crossing over RV Polarstern?
Line 432: In which way does “the gravity wave significantly disturb the
development of the liquid and the ice phase of the MPC deck and the interaction between both phase for hours.” – In Fig 5, I don’t see evidence of a disturbed development, if anything, the development of ice phase seems enhanced (enhanced radar reflectivity) and the lidar volume depol ratio seems to have similar values in the liquid-containing cloud-top layer.
Line 434-435. +section 454-459: Please list in which products you see perturbations. – I don’t see any at the indicated times. Also, this paragraph seems very speculative. Often the word “expected” is mentioned and then it is acknowledged that the expected behavior of variables was not observed. – As the information content is thus limited, I suggest shortening this section considerably.
Line 446: The term “precipitation fields” sounds not appropriate, the radar reflectivity is very low suggesting that just few ice crystals fell below the main virga features without sublimating, I suggest rephrasing. Please mention if any precipitation was observed by ground-based sensors.
Line 450-451: The scale of Fig 5 is too coarse to see the mentioned features.
Line 460-463: The methodology was previously introduced and can be omitted here.
Line 466: State why you think riming occurred. – Do you see that in specific variables?
Line 472: You mention that “The stable phase in the MPC evolution could not establish before 15:00 UTC.” – The ice production from 12 – 15 UTC lasted three hours and thus seems pretty stable to me. Why is this not considered as stable?
Line 479-480: Explain why the alternative hypothesis is not convincing.
Line 481-482: It is stated that ice crystal effective radius was 50 microns during the stable phase of the MPC. In Fig 6, it looks like as if this was the case for the entire observation period. – Clarify.
Line 485: 2x “alpha_liq” used
Line 490: Not quite true, IWC peaked again at 15 UTC.
Line 488-489: description of LWP time series is incomplete (10-15 UTC is missing). Why is there no LWP from 11-12 UTC in Fig7 Panel c).
Line 504: does the “most” refer to the entire MOSAiC observation period or to June and July?
Line 517: add a verb to the sentence
Line 521-22: at which times do you expect seeding to play a role (not clear to me in Fig. 8 as most pronounced virgae are mostly not at the same time as lower-liquid-containing cloud layers
Line 553-554: The sentence is unclear.
Line 555: What were the criteria for the selection of the subset?
Line 561: Why are cloud layers observed for < 20min not considered?
Line 565-566: How do the statistics of your analysis compare to these values?
Line 574: I don’t think the pure liquid layers refer only to clouds before ice nucleation sets in: In Fig 11 you show that quite a large fraction of PL layers have CCT of > 0C – so there won’t be ice formation setting in. rephrase.
Line 665: repeat the height range for “low cloud layers” here
Comments on Tables:
Table 1: Very good that a table regarding uncertainties is included. Please expand by adding two more columns: One indicating if the parameter is lidar-derived or lidar-radar derived and one more adding a reference in which the uncertainty is derived.
Comments on Figures:
Consider using logarithmic scale units for displaying radar reflectivity instead of linear units as commonly done in order to allow visual comparison of reflectivity with other manuscripts focusing on detailed case study analysis.
Fig. 1: Please explain the reason for the data gaps in the caption.
Fig. 2: Shorten the caption by removing sentences giving an analysis of the figure (virga is formed etc). Also, it is mentioned that the black vertical lines in b refer to the radiosonde launches at 5 and 17 UTC on Dec 31 etc. In panel b), the vertical black lines are at 0, 6, 12, and 18 UTC though and I count five (instead of four mentioned) black vertical lines. – Correct.
Also, in the description of Fig.2, pls comment on the cause of the layers of enhanced signal strength between roughly 1.5-2km altitude and 0-3 UTC.
Fig 2, 3 etc: Consider rephrasing “life-cycle” to “temporal evolution” unless you can prove that the onset/end of the observation of the cloud over RV Polarstern marks the formation/dissipation of the cloud and not the times the cloud was advected over the observatory.
Fig 3: In panel b,c add “lidar” to the title to make it coherent with panel a where you state the instrument name (radar)
Fig 4: add a horizontal line at 250m below liquid-containing layer base as well as 75m above it to show at which altitudes the values presented in Fig 3 are from.
Fig5. +line 452: In the caption refer to Panel c) as “Mean Doppler Velocity” as “vertical velocity” could be mistaken as “vertical air velocity”. Shorten the caption by removing the last sentence (“The orange regions may indicate upwind areas when taking permanent ice crystal sedimentation into account.”) since it is an interpretation of the figure which belongs to the main text.
Fig.7: “and produced strong ice virgae and triggered strong ice production.” is discussion and should thus be avoided in the caption. What happens at 15 UTC? IWC as well as IWP show a peak and should also be discussed.
Fig 8: shorten the caption by removing “All cloud layers show a blue color at cloud base (not always visible) in panel b, in an unambiguous sign for liquid-dominated cloud layers so that ice is produced by immersion freezing. The strong increase of the depolarization ratio with height (from blue to light greem yellow or even red) is caused by multiple light scattering by the water droplets.”
Fig. 11: Panel e) should have CDNC as x-axis label.
Citation: https://doi.org/10.5194/egusphere-2025-967-RC1 -
AC1: 'Reply on RC1', Cristofer Jimenez, 07 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-967/egusphere-2025-967-AC1-supplement.pdf
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AC1: 'Reply on RC1', Cristofer Jimenez, 07 Jul 2025
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RC2: 'Comment on egusphere-2025-967', Anonymous Referee #2, 24 Apr 2025
General comments:
This paper summarises the new information added to the body of knowledge regarding mixed-phase clouds (MPCs) by analysis of the data collected from the research vessel Polarstern. The paper presents four case studies and a statistical analysis of all observations in support of some generalised conclusions about the behaviour and formation of MPCs. This is a worthwhile expansion of the current scientific understanding of MPCs, and my recommendation is for publication after the minor issues outlined below have been addressed.
Specific comments:
The main issue that stands out to me is the statement in lines 670–671 that ‘The decreasing moisture content of an air mass, rather than empty CCN and INP reservoirs, is probably the reason for the dissolution of stratiform cloud layers in most cases’. While you do clearly establish that in your case studies you observed water droplets nucleating on a sufficient supply of background aerosol, that does not by itself conclusively answer the question of whether most MPCs dissipate because they exhaust their supply of water or because they exhaust their supply of aerosol (c.f. Sterzinger et al. [no affiliation] 2022, ‘Do Arctic mixed-phase clouds sometimes dissipate due to insufficient aerosol?’ or Loewe et al. [no affiliation] 2017, ‘Modelling micro-and macrophysical contributors to the dissipation of an Arctic mixed-phase cloud during the Arctic Summer Cloud Ocean Study (ASCOS)’). Both are physically possible causes. If your argument is that throughout the full year of MOSAiC observations you never saw evidence of cloud dissipation as a result of low aerosol (and thus low CCN and INP), this point should be made more explicitly and in more detail.
I agree with RC1 (no known affiliation) that ‘temporal evolution’ would be preferable to ‘lifecycle’, especially in the context of observations taken from a drifting vessel under advected cloud. Separately, referring to the cloud as ‘alive’ (e.g. line 35: ‘keeps the MPC top layer alive, frequently for hours’) is idiomatic and unclear. A description of the cloud processes would always be preferable to an analogy to biological life, e.g. ‘The steady resupply of water droplets allows the MPC supercooled liquid top layer to persist despite the continuously forming ice below, frequently for hours’.
The existence of the gravity wave in the September case also seems to me inconclusive. In the first mention on line 249 it is understood to be the ‘best guess’ theoretical explanation for the upward motion: ‘Gravity waves may have caused the perturbations.’ Similarly line 431: ‘probably the result of a gravity wave’, and line 669: ‘ probably by gravity wave activity’. However, the caption for Figure 7 states definitively: ‘Gravity waves crossed Polarstern between 12:00 and 14:00 UTC’. What evidence is there for this?
Lines 8–9: ‘We discuss two long-lasting Arctic MPC cases (one mid winter case and one late summer case) observed close to the North Pole in December 2019 and in September 2020.’ This should be edited to include mention of the 18 June and 25–28 July cases.
Line 40: define ‘fall strikes’.
Lines 98–101: Remove the sentence ‘We even illuminated a potential role of stratospheric wildfire smoke on polar ozone depletion (Ohneiser et al., 2021; Ansmann et al., 2022) and the relationship between vertically integrated tropospheric water vapor and the downward, broadband thermal-infrared irradiance at the ground during the MOSAiC winter half year (Seidel et al., 2024).’ These achievements are not directly relevant to the fous of this paper.
Lines 137–137: ‘The basic lidar data analysis applied to obtain the geometrical and optical properties (backscatter, extinction, linear depolarization ratio) is outlined in Baars et al. and Hofer et al. (2017).’ The placement of this parenthetical list suggests that all of these are both geometrical and optical properties. ‘Geometrical’ also does not occur in either of the sources cited, so the meaning is not immediately clear. I would suggest changing to e.g. ‘The basic lidar data analysis applied to obtain the geometrical (cloud base and cloud top heights) and optical (backscatter, extinction, linear depolarization ratio) properties is outlined in Baars et al. and Hofer et al. (2017).’
Lines 150–152: ‘The particle number concentration n50, considering all particles with radius >50 nm, is used as a proxy for the CCN concentrations, and n250, considering the large particle fraction (particles with radius >250 nm), is used to indicate the reservoir of INPs.’ Why is one a proxy and the other a reservoir? ‘Proxy for the INP concentrations’ would make more sense here, especially if you explained immediately thereafter that you are treating 1% of the n250 as ice-nucleating dust.
Table 1: It would be very helpful to include a column for the abbreviations for each aerosol and cloud property e.g. Re,liq for cloud droplet effective radius.
Lines 179–180: ‘Since lidar observation of pure ice crystal backscattering is only available for the virga zones’ – explain why in physical terms.
Lines 182–183: ‘the cloud base of the MPC top layer’ – unclear phrasing. I would suggest changing this to ‘base of the liquid-dominated cloud layer of the MPC’ as in line 170 and keeping this phrasing consistent throughout the text. A simple schematic diagram might also be helpful to the reader.
Lines 183–184 and 199–200: ‘these virga observations are well representative for the entire MPC height range, including the liquid-dominated cloud top layer’; ‘we use the virga IWC value at the top of the virga zone to be representative for the entire liquid-dominated cloud top layer as well’ – justify this briefly in-text as well as giving the Mioche et al. (2017) citation.
Line 210: ‘After applying several quality assurance procedures to the lidar observations’ – detail these.
Lines 222–223: ‘we counted a cloud field as one single cloud system if the detected cloud-free periods lasted for less than an hour’ – an hour seems like a very long gap. Explain the selection of this threshold.
Lines 229–230: ‘The retrieval of these particle number concentrations are explained in detail in Ansmann et al. (2023)’ – it would still be good to have a sentence or two briefly outlining the methods here.
Line 240: ‘At these high temperatures, mineral dust particles are ice-inactive’ – a citation would be good here.
Lines 296–297: ‘Increasing cooling of the MPC top layer also leads to an increase of available INPs.’ By what mechanism?
Lines 281–282: ‘The longevity of the MPC deck is, to our opinion, the result of the continuous production of liquid water, especially of the formation of new droplets’ – the water itself is not being produced. Rephrase to something like ‘The longevity of the MPC deck is, in our opinion, the result of the continuous nucleation of liquid water to form new droplets’.
Line 307: ‘seeder-feeder effects’ is used on this line for the first time but not defined in physical terms until lines 349–351; move that definition to accompany this first occurrence.
Line 364: ‘ice-phase fraction’ is used on this line for the first time but not defined in physical terms until line 401; move that definition to accompany this first occurrence.
Line 379: ‘permanently’ is an odd word here; rephrase. ‘Persistently’ would be one alternative.
Line 387: Explain in greater detail the significance of the time-dependent ice nucleation mechanism in the model and how this relates to your results. This is interesting but seems as though it is mentioned almost in passing.
Line 391: ‘the number of ice-nucleating particles (INPs) available for ice formation, termed INP reservoir’ – move this definition earlier, to lines 150–152 when you first introduce the term.
Line 419–420: ‘As on 30-31 December 2019, the air mass came from Iceland, Greenland, northern Canada, and even from Alaska.’ I suggest rephrasing to something like ‘the air mass contained aerosols from …’, and clarifying that this was known through the Radenz air mass attribution scheme (assuming that was how) and explaining briefly.
Line 455: as on line 379, ‘permanently’ is not the right word here.
Lines 456–459: The phenomenon you describe (vertical motions at 12:00 and 12:40) is frankly still not visible to me in Figure 5c despite the adjustments.
Line 479–480: ‘The alternative hypothesis that changes in the cloud properties are simply the result of changing aerosol conditions is not convincing’ – explain why not.
Lines 528–529: ‘Mineral dust particles were probably responsible for strong ice nucleation in the air mass above 6 km height’ – what is your reason for assuming this?
Lines 539–540: ‘Mineral dust is the most favorable INP type at these low temperatures’ – c.f. line 240, a citation would be good here.
Lines 558–559: ‘A careful data quality check with special focus on properly aligned dual FOV receiver characteristics was applied to all of the selected cloud events’ – again, outline what this check consisted of. An appendix detailing what all of these checks were (c.f. line 210) would be very useful as supplementary material.
Line 579: ‘The histograms of the PL cloud properties in Fig. 11a, b,d, and e are slightly and partly even considerably broader’ – this phrasing is not at all clear. Rephrase to something like ‘The histograms of the PL cloud properties in Fig. 11a, b, d, and e are all at least slightly broader, and some considerably broader, than the respective frequency-of-occurrence distributions for MPCs’.
Line 679: ‘We presented two case studies’ – rephrase to four case studies, unless you have decided to omit the June and July cases.
Lines 685-686: ‘The measurements further provided the impression that the CCN and INP reservoirs were always well filled, i.e., never depleted upon ice crystal formation.’ This statement only makes sense if you are treating CCN as synonymous with INP – rephrase.
Lines 690–691: ‘A first MPC lidar study was performed by Hofer et al. (2024)’ – add a sentence or two with more detail on this.
Technical corrections
The use of ‘rather’ throughout (e.g. line 92, ‘A rather detailed monitoring of the atmosphere…’) sounds informal and could in all occurrences be omitted without changing the meaning of the sentence.
‘Year-around’ and ‘year around’ are nonstandard and should be replaced with ‘year-round’ in all cases.
Figure 2: ‘indicate times with now useful lidar observations’ should read ‘indicate times with non-useful lidar observations’.
Figure 10: ‘as a function of the time period, needed by the cloud field to cross the Polarstern’ should read ‘as a function of the time period needed by the cloud field to cross the Polarstern’.
Figure 11: ‘The black histogram lines s are based on 3070 cloud data sets’ should read ‘The black histogram lines are based on 3070 cloud data sets’. Because all the histograms are outlined in black, consider rephrasing as ‘The thick black histogram lines are based on 3070 cloud data sets’ to differentiate that set of lines.
Line 50: ‘recognozed as the mian’ should read ‘recognized as the main’.
Line 80: ‘an introduction in the MOSAiC Polarstern route’ should read ‘an introduction to the MOSAiC Polarstern route’.
Line 113: ‘cloud micropyhsical properties’ should read ‘cloud microphysical properties’.
Line 157 and onwards: ‘recently introduced’ and ‘new’ are already established as a property of the dual FOV polarization lidar method. This does not need to be repeated on subsequent occurrences.
Lines 162–163: ‘The multiple scattering effect is a strong function of the number concentration of cloud droplets, their size, as well as of the receiver FOV of the lidar’ should read ‘The multiple scattering effect is a strong function of the number concentration of cloud droplets and of their size, as well as of the receiver FOV of the lidar’.
Lines 275–276: ‘The strongest temperatures decrease’ should read ‘the strongest temperature decrease’.
Line 307: ‘These crystals may have influence the MPC evolution’ should read ‘These crystals may have influenced the MPC evolution’.
Line 302: ‘Microphyscial properties’ should read ‘Microphysical properties’.
Line 315: ‘clout top layer’ should read ‘cloud top layer’.
Line 337: ‘the retrieval products for both, the liquid and the ice phase’ should read ‘the retrieval products for both the liquid and the ice phase’.
Line 350: ‘on the expense of liquid water droplets’ should read ‘at the expense of liquid water droplets’.
Line 479: ‘taking strong CCN activation into considerations’ should read ‘taking strong CCN activation into consideration’.
Line 494–495: ‘covered the sky above Polarstern in 50-55% of the time’ should read ‘covered the sky above Polarstern 50-55% of the time’.
Line 603: ‘ice cyrstal growth’ should read ‘ice crystal growth’.
Line 611: ‘Most PL clouds layers’ should read ‘Most PL cloud layers’.
Line 634: ‘before ice nucleation sets’ should read ‘before ice nucleation sets in’ or ‘before ice nucleation starts’.
Lines 665–666: ‘Low clouds layers occurr approximately 50% of the time’ should read ‘Low cloud layers occur approximately 50% of the time’.
Line 666: ‘the aerosol emitted in the Arctic..’ should read ‘the aerosol emitted in the Arctic.’
Lines 681–682: ‘These observations demonstrate, that CCN activation is an important process to assure a longevity of an MPC deck’ should read ‘These observations demonstrate that CCN activation is an important process to assure the longevity of an MPC deck’.
Line 705: ‘the elaboration of the final design of the manuscript’ should read ‘the elaboration of the final design of the manuscript.’
Line 707: ‘a member of the editorial board of Atmospheric Chemistry and Physics’ should read ‘a member of the editorial board of Atmospheric Chemistry and Physics.’
Lines 774–779: The citation for Baars et al. 2016, ‘An overview of the first decade of PollyNET: an emerging network of automated Raman-polarization lidars for continuous aerosol profiling’ is incomplete.
Citation: https://doi.org/10.5194/egusphere-2025-967-RC2 -
AC2: 'Reply on RC2', Cristofer Jimenez, 07 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-967/egusphere-2025-967-AC2-supplement.pdf
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AC2: 'Reply on RC2', Cristofer Jimenez, 07 Jul 2025
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AC3: 'Comment on egusphere-2025-967', Cristofer Jimenez, 07 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-967/egusphere-2025-967-AC3-supplement.pdf
Status: closed
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RC1: 'Comment on egusphere-2025-967', Anonymous Referee #1, 08 Apr 2025
Review of Jimenez et al., ACPD 2025 (egusphere-2025-967)
General comments to the manuscript
In the study titled “Life cycle studies and liquid-phase characterization of Arctic mixed-phase clouds: MOSAiC 2019-2020 results” by C. Jimenez et al., the authors show results of long-term lidar-radar observations onboard the RV Polarstern during the MOSAiC cruise. Radiosonde profiles helped to interpret the data. Four detailed case studies are presented: two of them explain liquid- and ice phase retrieval results, two only liquid retrieval results. Furthermore, statistical results related to free-tropospheric stratiform liquid-containing cloud layers were presented.
Recommendation:
I would suggest the manuscript to be published after minor revisions considering the remarks below. The authors should address the following points:
General/Major comments:
Title and throughout the text: Is “life cycle studies” the most fitting term? Throughout the study it was not clear to me how the life cycle of the cloud is assessed. Firstly, for the presented statistical analysis the focus is not the life-cycle and thus it is somewhat misleading in the title? Secondly and more generally, I think the term “temporal evolution” is more fitting than life-cycle. You acknowledge on lines 344-346 that from observations at a fixed location (Eulerian perspective) it is hard to perform life cycle analysis (Lagrangian perspective) – but you don’t say how you can be sure you really do study the life-cycle as claimed. I suggest referring to the case study analysis as “temporal evolution” unless you can convincingly show that the onset/end of the observation of the cloud over RV Polarstern marks the formation/dissipation of the cloud and not the times the cloud was advected over the observatory.
Further remark on title: At the same time, “2019-2020” after “MOSAiC” can be omitted. Furthermore, in Section 5 results of “Pure liquid” clouds are presented. This should be added to the title. How about rephrasing the title to sth. like “Characterization of Arctic liquid-containing free-tropospheric clouds observed during MOSAiC”
Third remark on title: “liquid-phase characterization” is somewhat misleading: In the first two case studies, liquid- and ice phase are characterized. Why was the ice phase not characterized in the statistical analysis in Section 5? It is strange that case study analysis is done for liquid- and ice-phase but the statistics are not. Remove the ice-phase analysis in case study 1 + 2?
Section 4.3 with two more case studies comes as a surprise, as the abstract and the conclusions section mention only 2 case studies. Also, why was only the liquid phase analyzed for these case studies? What is the added value of having four instead of two case studies? – I find the two additional case studies do not add much new content to the manuscript, consider removing them.
It would be good to firstly, mention the limitations of the lidar-based retrievals more clearly (briefly done on line 317): Complete lidar attenuation at optical depth > 2.5-3 leads to underrepresentation of multilayer cloud situations.
Minor comments:
Throughout the text many facts are added in brackets – consider removing those or splitting the sentences in two to improve readability.
Line 2: Were MPC really only observed in the free troposphere during MOSAiC? – If not, please remove the “free troposphere” here and refer to it later.
Line 16-17: Is it possible to be more exact than stating “aerosol reservoirs of CCN and INP are well-filled”?
Line 53 – 69: Consider reordering/adding an introductory sentence, so that it becomes clear, that in this paper both, retrievals for liquid phase based on lidar-only observations and ice phase based on lidar-radar observations, are employed.
Line 77: Here you state the focus is on liquid-phase properties. In line 67-68 you state ice phase properties are also retrieved. – So the reader would assume the focus is on both, liquid and ice? – Clarify.
Line 92: Add that the ocean was also studied in depth during MOSAiC.
Line 96 - 101: Who is “we”? - It is very uncommon to refer to a group of co-authors as “we” and to focus the literature study on own publications that are not pertinent to the study subject of the manuscript. Consider removing reference to wildfire smoke publications. Consider merging this paragraph with the one on lines 102 – 108 and extend your references to other studies using the MOSAiC atmospheric remote-sensing instrumentation, e.g. https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2193/egusphere-2024-2193.pdf or https://acp.copernicus.org/articles/23/14521/2023/ , https://doi.org/10.1525/elementa.2021.000071 among others.
Line 120: The acronym MOSAiC has been introduced before and does not need to be explained again here.
Line 127: add “profiles of”
Line 128: “retrievals of” instead of “observations of”
Line 147: “vertical profiles” instead of “height profiles”
Line 149: Either expand on the “even” by explaining what is special about summer aerosol conditions” or remove it
Line 152: I am confused by the wording “reservoir” – Why not call it “proxy for INP concentration”?
Line 156: replace “our” by “the”
Line 157: add “troposphere”, add a sentence on why altitude ranges below 500m and above 7 km are excluded from the analysis.
Line 161: add “liquid-containing” before cloud layer
Line 172: move the “well” to the end of the sentence
Line 175, line 232, line 237 etc: “On” the order of
Line 182-183: This sounds confusing: What is the MPC top layer? Is it the liquid-containing layer? - Then you could refer to the base of it as “base of the liquid-containing layer of the MPC” instead of as “cloud base” (here and elsewhere, e.g. line 314)
Line 184: What are these virga representative for? The evolution of ice properties (e.g. IWC, ice particle effective radius) with increasing distance from the base of the liquid-containing layer is e.g. dependent on the relative humidity. – Expand/clarify.
Line 210: Are only single-layer stratiform clouds considered or also multi-layer scenarios? Why are clouds > 7 km excluded from the analysis?
Line 218: add “interpolated” to the radiosonde temperature information
Line 223: Why is a cloud still counted as the same cloud if the cloud-free gap is almost an hour? It seems like a very high allowed gap time. Please clarify.
Line 236: What is meant by “time interval of ice nucleation of 60s”?
Line 240-241: The sentence “the CCN and INP reservoirs are well-filled” is used 4 times throughout the manuscript. – I still don’t understand it. Please only this phrase once and rephrase elsewhere to give readers the chance to understand the meaning once differently expressed.
Line 227 – 242, Fig 1: You previously mention that you consider clouds with tops up to 7 km. Please motivate clearly, why you only show the particle number concentrations at 2 km height instead of at different altitudes.
Line 243: Begin what? – Consider removing the phrase.
Line 257: Is the start of the winter-time MPC Dec 30 as stated here or Dec 29 as stated on line 246?
Line 260: clarify if you mean horizontal or vertical wind velocities
Line 263: what do you mean by “a few percent of the air mass were advected from 30-60 N”?
Line 264: I suggest adding “likely” in front of “soil material” as soil moisture content also plays an important role in lifting of soil dust that is not considered
Line 310: Can you substantiate your hypothesis that riming occurred with the available observations? Also, explain how would riming lead to strong ice production?
Line 312: Substantiate your claim of homogeneously distributed ice crystals in the virgae column.
Line 321: add “lidar volume” in front of depol ratio
Line 321-324: Following your explanation in this paragraph, the low lidar volume depolarization ratios marked in green at the lower end of the virgae are caused by droplets backscattering. – Clarify/expand.
Line 332: Consider displaying the cloud radar mean Doppler velocity time-height display to see if you can identify the same virgae structure as well as cycles of up- and downdrafts (superimposed on particle fall velocity) in it. This might substantiate your hypothesis of decreased up- and downdraft strength in the later part of the case study observation as well (lines 355-359).
Line 336-337: consider discussion of the Sep 21, 2020 case study to its corresponding section. What can we learn from differing horizontal separation of the updrafts in the two considered case studies?
Line 340: What is the other measured depolarization ratio?
Line 341-343: This was mentioned earlier and can thus be removed.
Line 353-354: You attributed the enhanced ice virgae at the beginning of the observation period to potential ice seeding from the cloud above. The strong virgae extends to after when the upper left cloud was not observed anymore (until around 9 UTC). Why?
Line 364ff: Please add the definitions of the ice-phase fractions from IWC, LWC, CDNC, and ICNC. – ok, partly shown on line 401, move here at first mention
Line 38ff: To me the conclusion that a time-dependent INP activation is central for the longevity to MPC should be added to the abstract.
In the discussion of the wintertime case study (Section 4.1.), the feature at 22-23 UTC below 1 km with increased values of several parameters is not mentioned yet and should be discussed.
Line 418: 88.5°N is “near” the North Pole, not “over” the North Pole. Please correct it.
Line 420: Rephrase “the air mass came from Iceland, Greenland, northern Canada, and even from Alaska” – unclear how the same air mass can come from all of these different directions.
Line 431: Do you have a reference to substantiate your assumption of gravity wave crossing over RV Polarstern?
Line 432: In which way does “the gravity wave significantly disturb the
development of the liquid and the ice phase of the MPC deck and the interaction between both phase for hours.” – In Fig 5, I don’t see evidence of a disturbed development, if anything, the development of ice phase seems enhanced (enhanced radar reflectivity) and the lidar volume depol ratio seems to have similar values in the liquid-containing cloud-top layer.
Line 434-435. +section 454-459: Please list in which products you see perturbations. – I don’t see any at the indicated times. Also, this paragraph seems very speculative. Often the word “expected” is mentioned and then it is acknowledged that the expected behavior of variables was not observed. – As the information content is thus limited, I suggest shortening this section considerably.
Line 446: The term “precipitation fields” sounds not appropriate, the radar reflectivity is very low suggesting that just few ice crystals fell below the main virga features without sublimating, I suggest rephrasing. Please mention if any precipitation was observed by ground-based sensors.
Line 450-451: The scale of Fig 5 is too coarse to see the mentioned features.
Line 460-463: The methodology was previously introduced and can be omitted here.
Line 466: State why you think riming occurred. – Do you see that in specific variables?
Line 472: You mention that “The stable phase in the MPC evolution could not establish before 15:00 UTC.” – The ice production from 12 – 15 UTC lasted three hours and thus seems pretty stable to me. Why is this not considered as stable?
Line 479-480: Explain why the alternative hypothesis is not convincing.
Line 481-482: It is stated that ice crystal effective radius was 50 microns during the stable phase of the MPC. In Fig 6, it looks like as if this was the case for the entire observation period. – Clarify.
Line 485: 2x “alpha_liq” used
Line 490: Not quite true, IWC peaked again at 15 UTC.
Line 488-489: description of LWP time series is incomplete (10-15 UTC is missing). Why is there no LWP from 11-12 UTC in Fig7 Panel c).
Line 504: does the “most” refer to the entire MOSAiC observation period or to June and July?
Line 517: add a verb to the sentence
Line 521-22: at which times do you expect seeding to play a role (not clear to me in Fig. 8 as most pronounced virgae are mostly not at the same time as lower-liquid-containing cloud layers
Line 553-554: The sentence is unclear.
Line 555: What were the criteria for the selection of the subset?
Line 561: Why are cloud layers observed for < 20min not considered?
Line 565-566: How do the statistics of your analysis compare to these values?
Line 574: I don’t think the pure liquid layers refer only to clouds before ice nucleation sets in: In Fig 11 you show that quite a large fraction of PL layers have CCT of > 0C – so there won’t be ice formation setting in. rephrase.
Line 665: repeat the height range for “low cloud layers” here
Comments on Tables:
Table 1: Very good that a table regarding uncertainties is included. Please expand by adding two more columns: One indicating if the parameter is lidar-derived or lidar-radar derived and one more adding a reference in which the uncertainty is derived.
Comments on Figures:
Consider using logarithmic scale units for displaying radar reflectivity instead of linear units as commonly done in order to allow visual comparison of reflectivity with other manuscripts focusing on detailed case study analysis.
Fig. 1: Please explain the reason for the data gaps in the caption.
Fig. 2: Shorten the caption by removing sentences giving an analysis of the figure (virga is formed etc). Also, it is mentioned that the black vertical lines in b refer to the radiosonde launches at 5 and 17 UTC on Dec 31 etc. In panel b), the vertical black lines are at 0, 6, 12, and 18 UTC though and I count five (instead of four mentioned) black vertical lines. – Correct.
Also, in the description of Fig.2, pls comment on the cause of the layers of enhanced signal strength between roughly 1.5-2km altitude and 0-3 UTC.
Fig 2, 3 etc: Consider rephrasing “life-cycle” to “temporal evolution” unless you can prove that the onset/end of the observation of the cloud over RV Polarstern marks the formation/dissipation of the cloud and not the times the cloud was advected over the observatory.
Fig 3: In panel b,c add “lidar” to the title to make it coherent with panel a where you state the instrument name (radar)
Fig 4: add a horizontal line at 250m below liquid-containing layer base as well as 75m above it to show at which altitudes the values presented in Fig 3 are from.
Fig5. +line 452: In the caption refer to Panel c) as “Mean Doppler Velocity” as “vertical velocity” could be mistaken as “vertical air velocity”. Shorten the caption by removing the last sentence (“The orange regions may indicate upwind areas when taking permanent ice crystal sedimentation into account.”) since it is an interpretation of the figure which belongs to the main text.
Fig.7: “and produced strong ice virgae and triggered strong ice production.” is discussion and should thus be avoided in the caption. What happens at 15 UTC? IWC as well as IWP show a peak and should also be discussed.
Fig 8: shorten the caption by removing “All cloud layers show a blue color at cloud base (not always visible) in panel b, in an unambiguous sign for liquid-dominated cloud layers so that ice is produced by immersion freezing. The strong increase of the depolarization ratio with height (from blue to light greem yellow or even red) is caused by multiple light scattering by the water droplets.”
Fig. 11: Panel e) should have CDNC as x-axis label.
Citation: https://doi.org/10.5194/egusphere-2025-967-RC1 -
AC1: 'Reply on RC1', Cristofer Jimenez, 07 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-967/egusphere-2025-967-AC1-supplement.pdf
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AC1: 'Reply on RC1', Cristofer Jimenez, 07 Jul 2025
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RC2: 'Comment on egusphere-2025-967', Anonymous Referee #2, 24 Apr 2025
General comments:
This paper summarises the new information added to the body of knowledge regarding mixed-phase clouds (MPCs) by analysis of the data collected from the research vessel Polarstern. The paper presents four case studies and a statistical analysis of all observations in support of some generalised conclusions about the behaviour and formation of MPCs. This is a worthwhile expansion of the current scientific understanding of MPCs, and my recommendation is for publication after the minor issues outlined below have been addressed.
Specific comments:
The main issue that stands out to me is the statement in lines 670–671 that ‘The decreasing moisture content of an air mass, rather than empty CCN and INP reservoirs, is probably the reason for the dissolution of stratiform cloud layers in most cases’. While you do clearly establish that in your case studies you observed water droplets nucleating on a sufficient supply of background aerosol, that does not by itself conclusively answer the question of whether most MPCs dissipate because they exhaust their supply of water or because they exhaust their supply of aerosol (c.f. Sterzinger et al. [no affiliation] 2022, ‘Do Arctic mixed-phase clouds sometimes dissipate due to insufficient aerosol?’ or Loewe et al. [no affiliation] 2017, ‘Modelling micro-and macrophysical contributors to the dissipation of an Arctic mixed-phase cloud during the Arctic Summer Cloud Ocean Study (ASCOS)’). Both are physically possible causes. If your argument is that throughout the full year of MOSAiC observations you never saw evidence of cloud dissipation as a result of low aerosol (and thus low CCN and INP), this point should be made more explicitly and in more detail.
I agree with RC1 (no known affiliation) that ‘temporal evolution’ would be preferable to ‘lifecycle’, especially in the context of observations taken from a drifting vessel under advected cloud. Separately, referring to the cloud as ‘alive’ (e.g. line 35: ‘keeps the MPC top layer alive, frequently for hours’) is idiomatic and unclear. A description of the cloud processes would always be preferable to an analogy to biological life, e.g. ‘The steady resupply of water droplets allows the MPC supercooled liquid top layer to persist despite the continuously forming ice below, frequently for hours’.
The existence of the gravity wave in the September case also seems to me inconclusive. In the first mention on line 249 it is understood to be the ‘best guess’ theoretical explanation for the upward motion: ‘Gravity waves may have caused the perturbations.’ Similarly line 431: ‘probably the result of a gravity wave’, and line 669: ‘ probably by gravity wave activity’. However, the caption for Figure 7 states definitively: ‘Gravity waves crossed Polarstern between 12:00 and 14:00 UTC’. What evidence is there for this?
Lines 8–9: ‘We discuss two long-lasting Arctic MPC cases (one mid winter case and one late summer case) observed close to the North Pole in December 2019 and in September 2020.’ This should be edited to include mention of the 18 June and 25–28 July cases.
Line 40: define ‘fall strikes’.
Lines 98–101: Remove the sentence ‘We even illuminated a potential role of stratospheric wildfire smoke on polar ozone depletion (Ohneiser et al., 2021; Ansmann et al., 2022) and the relationship between vertically integrated tropospheric water vapor and the downward, broadband thermal-infrared irradiance at the ground during the MOSAiC winter half year (Seidel et al., 2024).’ These achievements are not directly relevant to the fous of this paper.
Lines 137–137: ‘The basic lidar data analysis applied to obtain the geometrical and optical properties (backscatter, extinction, linear depolarization ratio) is outlined in Baars et al. and Hofer et al. (2017).’ The placement of this parenthetical list suggests that all of these are both geometrical and optical properties. ‘Geometrical’ also does not occur in either of the sources cited, so the meaning is not immediately clear. I would suggest changing to e.g. ‘The basic lidar data analysis applied to obtain the geometrical (cloud base and cloud top heights) and optical (backscatter, extinction, linear depolarization ratio) properties is outlined in Baars et al. and Hofer et al. (2017).’
Lines 150–152: ‘The particle number concentration n50, considering all particles with radius >50 nm, is used as a proxy for the CCN concentrations, and n250, considering the large particle fraction (particles with radius >250 nm), is used to indicate the reservoir of INPs.’ Why is one a proxy and the other a reservoir? ‘Proxy for the INP concentrations’ would make more sense here, especially if you explained immediately thereafter that you are treating 1% of the n250 as ice-nucleating dust.
Table 1: It would be very helpful to include a column for the abbreviations for each aerosol and cloud property e.g. Re,liq for cloud droplet effective radius.
Lines 179–180: ‘Since lidar observation of pure ice crystal backscattering is only available for the virga zones’ – explain why in physical terms.
Lines 182–183: ‘the cloud base of the MPC top layer’ – unclear phrasing. I would suggest changing this to ‘base of the liquid-dominated cloud layer of the MPC’ as in line 170 and keeping this phrasing consistent throughout the text. A simple schematic diagram might also be helpful to the reader.
Lines 183–184 and 199–200: ‘these virga observations are well representative for the entire MPC height range, including the liquid-dominated cloud top layer’; ‘we use the virga IWC value at the top of the virga zone to be representative for the entire liquid-dominated cloud top layer as well’ – justify this briefly in-text as well as giving the Mioche et al. (2017) citation.
Line 210: ‘After applying several quality assurance procedures to the lidar observations’ – detail these.
Lines 222–223: ‘we counted a cloud field as one single cloud system if the detected cloud-free periods lasted for less than an hour’ – an hour seems like a very long gap. Explain the selection of this threshold.
Lines 229–230: ‘The retrieval of these particle number concentrations are explained in detail in Ansmann et al. (2023)’ – it would still be good to have a sentence or two briefly outlining the methods here.
Line 240: ‘At these high temperatures, mineral dust particles are ice-inactive’ – a citation would be good here.
Lines 296–297: ‘Increasing cooling of the MPC top layer also leads to an increase of available INPs.’ By what mechanism?
Lines 281–282: ‘The longevity of the MPC deck is, to our opinion, the result of the continuous production of liquid water, especially of the formation of new droplets’ – the water itself is not being produced. Rephrase to something like ‘The longevity of the MPC deck is, in our opinion, the result of the continuous nucleation of liquid water to form new droplets’.
Line 307: ‘seeder-feeder effects’ is used on this line for the first time but not defined in physical terms until lines 349–351; move that definition to accompany this first occurrence.
Line 364: ‘ice-phase fraction’ is used on this line for the first time but not defined in physical terms until line 401; move that definition to accompany this first occurrence.
Line 379: ‘permanently’ is an odd word here; rephrase. ‘Persistently’ would be one alternative.
Line 387: Explain in greater detail the significance of the time-dependent ice nucleation mechanism in the model and how this relates to your results. This is interesting but seems as though it is mentioned almost in passing.
Line 391: ‘the number of ice-nucleating particles (INPs) available for ice formation, termed INP reservoir’ – move this definition earlier, to lines 150–152 when you first introduce the term.
Line 419–420: ‘As on 30-31 December 2019, the air mass came from Iceland, Greenland, northern Canada, and even from Alaska.’ I suggest rephrasing to something like ‘the air mass contained aerosols from …’, and clarifying that this was known through the Radenz air mass attribution scheme (assuming that was how) and explaining briefly.
Line 455: as on line 379, ‘permanently’ is not the right word here.
Lines 456–459: The phenomenon you describe (vertical motions at 12:00 and 12:40) is frankly still not visible to me in Figure 5c despite the adjustments.
Line 479–480: ‘The alternative hypothesis that changes in the cloud properties are simply the result of changing aerosol conditions is not convincing’ – explain why not.
Lines 528–529: ‘Mineral dust particles were probably responsible for strong ice nucleation in the air mass above 6 km height’ – what is your reason for assuming this?
Lines 539–540: ‘Mineral dust is the most favorable INP type at these low temperatures’ – c.f. line 240, a citation would be good here.
Lines 558–559: ‘A careful data quality check with special focus on properly aligned dual FOV receiver characteristics was applied to all of the selected cloud events’ – again, outline what this check consisted of. An appendix detailing what all of these checks were (c.f. line 210) would be very useful as supplementary material.
Line 579: ‘The histograms of the PL cloud properties in Fig. 11a, b,d, and e are slightly and partly even considerably broader’ – this phrasing is not at all clear. Rephrase to something like ‘The histograms of the PL cloud properties in Fig. 11a, b, d, and e are all at least slightly broader, and some considerably broader, than the respective frequency-of-occurrence distributions for MPCs’.
Line 679: ‘We presented two case studies’ – rephrase to four case studies, unless you have decided to omit the June and July cases.
Lines 685-686: ‘The measurements further provided the impression that the CCN and INP reservoirs were always well filled, i.e., never depleted upon ice crystal formation.’ This statement only makes sense if you are treating CCN as synonymous with INP – rephrase.
Lines 690–691: ‘A first MPC lidar study was performed by Hofer et al. (2024)’ – add a sentence or two with more detail on this.
Technical corrections
The use of ‘rather’ throughout (e.g. line 92, ‘A rather detailed monitoring of the atmosphere…’) sounds informal and could in all occurrences be omitted without changing the meaning of the sentence.
‘Year-around’ and ‘year around’ are nonstandard and should be replaced with ‘year-round’ in all cases.
Figure 2: ‘indicate times with now useful lidar observations’ should read ‘indicate times with non-useful lidar observations’.
Figure 10: ‘as a function of the time period, needed by the cloud field to cross the Polarstern’ should read ‘as a function of the time period needed by the cloud field to cross the Polarstern’.
Figure 11: ‘The black histogram lines s are based on 3070 cloud data sets’ should read ‘The black histogram lines are based on 3070 cloud data sets’. Because all the histograms are outlined in black, consider rephrasing as ‘The thick black histogram lines are based on 3070 cloud data sets’ to differentiate that set of lines.
Line 50: ‘recognozed as the mian’ should read ‘recognized as the main’.
Line 80: ‘an introduction in the MOSAiC Polarstern route’ should read ‘an introduction to the MOSAiC Polarstern route’.
Line 113: ‘cloud micropyhsical properties’ should read ‘cloud microphysical properties’.
Line 157 and onwards: ‘recently introduced’ and ‘new’ are already established as a property of the dual FOV polarization lidar method. This does not need to be repeated on subsequent occurrences.
Lines 162–163: ‘The multiple scattering effect is a strong function of the number concentration of cloud droplets, their size, as well as of the receiver FOV of the lidar’ should read ‘The multiple scattering effect is a strong function of the number concentration of cloud droplets and of their size, as well as of the receiver FOV of the lidar’.
Lines 275–276: ‘The strongest temperatures decrease’ should read ‘the strongest temperature decrease’.
Line 307: ‘These crystals may have influence the MPC evolution’ should read ‘These crystals may have influenced the MPC evolution’.
Line 302: ‘Microphyscial properties’ should read ‘Microphysical properties’.
Line 315: ‘clout top layer’ should read ‘cloud top layer’.
Line 337: ‘the retrieval products for both, the liquid and the ice phase’ should read ‘the retrieval products for both the liquid and the ice phase’.
Line 350: ‘on the expense of liquid water droplets’ should read ‘at the expense of liquid water droplets’.
Line 479: ‘taking strong CCN activation into considerations’ should read ‘taking strong CCN activation into consideration’.
Line 494–495: ‘covered the sky above Polarstern in 50-55% of the time’ should read ‘covered the sky above Polarstern 50-55% of the time’.
Line 603: ‘ice cyrstal growth’ should read ‘ice crystal growth’.
Line 611: ‘Most PL clouds layers’ should read ‘Most PL cloud layers’.
Line 634: ‘before ice nucleation sets’ should read ‘before ice nucleation sets in’ or ‘before ice nucleation starts’.
Lines 665–666: ‘Low clouds layers occurr approximately 50% of the time’ should read ‘Low cloud layers occur approximately 50% of the time’.
Line 666: ‘the aerosol emitted in the Arctic..’ should read ‘the aerosol emitted in the Arctic.’
Lines 681–682: ‘These observations demonstrate, that CCN activation is an important process to assure a longevity of an MPC deck’ should read ‘These observations demonstrate that CCN activation is an important process to assure the longevity of an MPC deck’.
Line 705: ‘the elaboration of the final design of the manuscript’ should read ‘the elaboration of the final design of the manuscript.’
Line 707: ‘a member of the editorial board of Atmospheric Chemistry and Physics’ should read ‘a member of the editorial board of Atmospheric Chemistry and Physics.’
Lines 774–779: The citation for Baars et al. 2016, ‘An overview of the first decade of PollyNET: an emerging network of automated Raman-polarization lidars for continuous aerosol profiling’ is incomplete.
Citation: https://doi.org/10.5194/egusphere-2025-967-RC2 -
AC2: 'Reply on RC2', Cristofer Jimenez, 07 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-967/egusphere-2025-967-AC2-supplement.pdf
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AC2: 'Reply on RC2', Cristofer Jimenez, 07 Jul 2025
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AC3: 'Comment on egusphere-2025-967', Cristofer Jimenez, 07 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-967/egusphere-2025-967-AC3-supplement.pdf
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