the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Oct 2026
Online single-particle characterization of ice-nucleating particles (INPs) at the High Altitude Research Station Jungfraujoch (3580 m a.s.l.), Switzerland
Abstract. Ice-nucleating particles (INPs) modulate the phase, radiative properties, and lifetime of clouds, yet direct observational evidence linking single aerosol particles to atmospheric ice nucleation (IN) remains challenging because of the low abundance of INPs. We sampled ambient aerosols by coupling an INP counter to a single-particle mass spectrometry (SPMS) via a pumped counter-flow virtual impactor at Jungfraujoch during wintertime. Ice crystal residuals (ICRs) sampled under conditions representative of mixed-phase and cirrus cloud formation and total aerosol sampled directly by the SPMS were chemically characterized. Mineral dust (MD) dominated the ICR population under both cloud regimes despite its minor contribution to ambient aerosol particles by number. Two distinct MD subclasses associated with local construction activities (MD-K/Al/Fe) and transported sources (MD-Ca) were identified. MD-K/Al/Fe contributed substantially to the INP population in the cirrus cloud regime, demonstrating that local anthropogenic activity can influence atmospheric INPs populations. In contrast, sulfate, organics, nitrate, and biomass burning aerosol (BBA) particles contributed only a minor fraction of ICRs despite dominating the ambient aerosol population, indicating low IN activity under the investigated conditions. However, Pb signatures were enriched in BBA ICRs, suggesting enhanced IN activity of Pb-containing BBA particles, whereas no corresponding enrichment was observed for Pb-containing MD-K/Al/Fe particles. Sporadic meteoric particles detected during stratospheric-intrusion events indicate a potential contribution of stratospheric aerosols to tropospheric primary IN. Limited in-cloud observations suggest that natural cloud processing may modify the IN activity of MD-K/Al/Fe and BBA particles.
Competing interests: Ottmar Möhler is a member of the editorial board of Atmospheric Chemistry and Physics and a co-author of this paper.
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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Status: open (until 23 Nov 2026)
- RC1: 'Comment on egusphere-2026-5645', Anonymous Referee #1, 27 Oct 2026 reply
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RC2: 'Comment on egusphere-2026-5645', Anonymous Referee #2, 31 Oct 2026
reply
Summary
This manuscript (“Online single-particle characterization of ice-nucleating particles (INPs) at the High Altitude Research Station Jungfraujoch (3580 m a.s.l.), Switzerland”) by Zhang et al. This paper investigates the composition and sources of ice nucleating particles (INPs) at Jungfraujoch observatory in Switzerland by measuring the composition of ice crystal residuals (ICRs) using a single particle mass spectrometer. They measured ICR composition under mixed-phase and cirrus cloud conditions. They observed that mineral dust was the most important contributor under both conditions, despite being a minor contributor in ambient particles. Mineral dust was separated into two classes with distinct composition. Sulfate, organics, nitrates, and biomass burning (BB) aerosol were minor contributors to INP populations despite dominating ambient concentrations. BB ICR particles exhibited enhanced lead relative to ambient. BB. They also note the presence of meteoric material during what appear to be stratospheric intrusion events.
Overall, I like this study, think it is interesting, and that it warrants publication in ACP after some revisions. My suggestions are below.
General comments
One major comment is that measurement uncertainty is not considered for calculating particle fractions. Many of the analyses presented in this study are based upon a small number of particles (e.g. section 3.3.2) and could actually be statistically insignificant. Including some estimate of the uncertainty will allow the authors to determine significance and would strengthen the conclusions of the manuscript.
Another issue is that it is unclear how the authors are defining anthropogenic dust. For instance, in the abstract they state that are “[t]wo distinct MD subclasses associated with local construction activities (MD-K/Al/Fe) and transported sources (MD-Ca).” However, it is never explicitly stated in the manuscript and if the MD-K/Al/Fe is indeed anthropogenic, then it is not proven anywhere. For example, the authors state “ambient MD-K/Al/Fe particles are consistently 4 to 6 times more abundant than MD-Ca.” If the MD-K/Al/Fe particles are a result of anthropogenic activities, then we would expect this ratio to change dramatically during the construction period. I also think the lack of concrete definition makes it easy to conflate the anthropogenic production of dust via digging/drilling (section 3.1) that I would not expect to change the composition of the particles much with “classical” anthropogenic emissions, such as the emission of particles containing Pb.
Another comment is that the analysis feels incomplete without also discussing the size of the ICR. The PALMS-NG provides size-resolved composition and the authors are also using a UHSAS to measure the INP size distribution. Given that particle size is well known to affect ice nucleation activity, I think it is warranted to expand the analysis to reflect this.
My last general comment is that there is a conflation of cloud processing, and measurement of MPC and CC regimes in the HINC-auto. In other manuscripts, maybe this would not be so confusing, but in this one the authors are sometimes sampling cloud residuals, not just ice crystal residuals. I would recommend changing language regarding the HINC-auto to clarify the distinction.
Specific comments
Line 100: Cornwell et al. (2024) also measured INP composition at site in rural Oklahoma. They also observed an enhancement in dust and dust-containing particles. They also observed that the ICR dust had elevated lead relative to ambient dust. Their work is surely relevant to this study.
Line 141: Why both the UHSAS and PALMS-NG? PALMS-NG provides size as well as composition, so why do you also need to measure the size distribution with the UHSAS?
Line 203: The WIBS measures the optical diameter, not the aerodynamic diameter. Are you sure that you did not do this for the APS data instead? How do you resolve the WIBS and APS data if they both measure da?
Figure 3 caption: Text currently reads “particles with dm < 90 nm (N≥90)”, but these are contradictory. Change to N<=90. What do the red shadings in 3a,b,c represent? Why is the shading lighter in 3b?
Line 277: Cloud processing as you have framed it in the manuscript refers to a pretty specific process and is not what is happening inside the HINC-auto.
Line 325: Is the definition of anthropogenic here solely due to when the particles are emitted?
Line 352: Comparable to what?
Appendix A: Figures come before section title for Appendix A. What are the units of the S-R relationships? Also, I do not see a difference between any of the S-R plots, even though they are supposed to come from different days.
Line 434: Is the station always in-cloud during the construction period? I went back to section
References
Cornwell, G. C., Steinke, I., Lata, N. N., Zelenyuk, A., Kulkarni, G., Pekour, M., et al. (2024). Enrichment of phosphates, lead, and mixed soil-organic particles in INPs at the Southern Great Plains site. Journal of Geophysical Research: Atmospheres, 129, e2024JD040826. https://doi.org/10.1029/2024JD040826
Citation: https://doi.org/10.5194/egusphere-2026-5645-RC2 -
RC3: 'Comment on egusphere-2026-5645', Anonymous Referee #3, 01 Nov 2026
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5645/egusphere-2026-5645-RC3-supplement.pdf
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- 1
This manuscript by Zhang et al. presents measurements conducted at the high-altitude research station at Jungfraujoch during winter. The authors deployed a suite of instruments, including PCVI and PALMS-NG, to directly measure INPs and ice crystal residual (ICR) particles. Such direct observations in a harsh environment provide valuable insights into the formation and evolution of ice crystals in mixed-phase clouds. I support the publication of this manuscript in this journal, subject to some revisions.
Comment 1: My main concern, and a limitation of this study, is the small number of detected ice crystal residuals during the non-construction period (n = 15 and 10 for MPC and CC conditions, respectively). Are these numbers within the expected range, or are they lower than anticipated? If they are lower than expected, could the authors provide a possible explanation?
Given the small sample sizes, the discussion in Page 12, Lines 277-281, for example, should be interpreted with caution. Both 6.7% and 10% correspond to only a single particle. At a minimum, the authors should explicitly acknowledge that some conclusions are based on limited particle counts.
Comment 2: Why were the PALMS-NG measurement periods sporadic (Fig. 2a)? How were these measurement periods selected?
Comment 3: Lines 322-324: Can the ACSM provide any information regarding the presence of sea-salt particles?
Comment 4: Line 338-340: The statement, “EF are conservative and represent the lower limit,” is confusing. It seems that the EF may be overestimated because particles with 0.1 μm ≤ dva < 0.6 μm could contribute to the particles with 0.6 μm ≤ dva ≤ 4 μm, rather than representing a lower limit? I was not sure the exact meaning here and please rephrase this sentence to clarify its meaning.
Comment 5: Lines 363-369: Can WIBS provide any information regarding the presence of biological particles?
Comment 6: Lines 442-443: “The EF for BBA particles increases significantly from 0.23 to 0.65, whereas that for SON aerosol particles drops only slightly from 0.32 to 0.38.” I could not determine how the values 0.65 and 0.38 were derived. Please clarify the meaning of the values and how these values were obtained.
Comment 7: All panel (c) plots in Figures A1-A5 appear identical. Are these panels correct?
Comment 8: In the reference list, the abbreviation “tLDR” and summary sentences appears in several entries. I am unsure whether such sentences are required or permitted in the journal's reference style. Please check and revise the references accordingly.