the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Jan 2026
Ice nucleation activity of mineral dust from Morocco and Iceland in immersion freezing mode and its relationship with mineralogy and particle size
Abstract. Ice nucleation activity (INA) in the mixed-phase cloud regime has been extensively studied. Nevertheless, most research has focused on particles smaller than a few micrometers. Moreover, the INA dependence on mineralogical composition and size of the tested particles is often not well characterized, particularly for particles larger than ten micrometers in diameter. This gap is significant, as studies suggest that large mineral dust particles can travel long distances.
Here, we used natural soil dust samples collected during field campaigns in Morocco and Iceland and characterized in terms of their mineralogical composition and size. The samples’ INA was tested in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber, the Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology (INSEKT), the new AIDA mini (AIDAm), and the IR-DROFA freezing assay in more than 300 experiments. Moroccan samples exhibited INA comparable to that reported for K-feldspar in previous studies, with no dependence on particle size. In contrast, Icelandic samples showed lower INA than in other studies using samples of similar composition, along with a subtle size dependence, linking to pyroxene content as an important driver of INA. Our findings elucidate the role of larger dust particles in ice nucleation through immersion freezing, and their relationship with mineralogy and size for low- and high-latitude sources.
Competing interests: At least one of the (co-) authors 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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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-6240', Anonymous Referee #1, 23 Feb 2026
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RC2: 'Comment on egusphere-2025-6240', Anonymous Referee #2, 03 Mar 2026
The paper investigates the immersion freezing ice‑nucleating activity (INA) of natural mineral dust from Morocco (low latitude) and Iceland (high latitude). The authors focused on coarse and super‑coarse particles and how INA relates to particle size and mineralogy. It combines a large number of experiments in multiple instruments and shows that Moroccan dust exhibits INA comparable to K‑feldspar with no clear size dependence, whereas Icelandic dust is less ice active, with a weaker, mineralogy‑linked size dependence. This work is important because it extends INA characterization to larger particle sizes and high‑latitude dust sources that are poorly constrained in current INP parameterizations. Overall, the manuscript could be made more concise to improve readability and easier to follow. Authors pointed out importance of how INAS density calculations can be revised for coarse and "super-coarse" particles. The study would benefit from clearer, quantitative discussion of size effects, a more explicit separation of instrument‑related differences from true dust‑property differences.
Here are the comments to consider:
I feel the restructuring of the paper and highlights the main points would improve the readability of the paper. Maybe move some of the more detailed derivations, intermediate equations, or sensitivity analyses to the Appendix and keep the main text focused on key steps and conclusions.
For Morocco, you state that INA shows no dependence on particle size, while for Iceland you find a “subtle” size dependence linked to pyroxene content. Given the central role of size in the paper, I suggest bit more quantitative discussion of this if possible. For example, include more explicit statistics for the size effect.
Moroccan samples showed no dependence on particle size, likely because the K-feldspar content remained constant across all sizes. How confident are you about your composition measurements for larger particles?
Emphasizing what is new for high‑latitude dust parameterizations (e.g., capturing pyroxene‑associated variability, broader spread in ns) and what that implies for Arctic/boreal mixed‑phase cloud simulations.
You showed an important comparison of INAS densities from AIDA and INSEKT and show systematic offsets. However, it is sometimes unclear whether observed differences in INA are driven more by sample properties (size, mineralogy) or by methodological differences between instruments.
In its current form, the manuscript focuses heavily on instrument intercomparisons and systematic biases, ns calculations, giving it the tone of a technical report rather than a science-driven study. It would strengthen the paper to expand the scientific discussion, particularly regarding the implications of these biases.
The link to atmospheric relevance part could be improved. For example, how using your Morocco vs Iceland parameterizations would change predicted INP concentrations in a simple idealized case?
Citation: https://doi.org/10.5194/egusphere-2025-6240-RC2
Data sets
Ice nucleation activity of mineral dust from Morocco and Iceland in immersion freezing mode: experimental data from AIDA, AIDAm, and INSEKT Sebastian Vergara Palacio et al. https://doi.org/10.5281/zenodo.17933358
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The authors investigated the ice nucleation ability of large size dust particles. The results are interesting and contribute towards advancement of ice nucleation research. I have couple of comments and suggest the publication.