See attached. It is a nice dataset. My main concerns are how valid is comparing Dmax between model and observations when the model seems to be lacking the aggregation process. 

The manuscript titled "A Microphysics Guide to Cirrus – Part 3: Occurrence patterns of cloud particles" presents an analysis of cloud particle size distributions (PSDs) derived from 270 hours of measurements, encompassing approximately 975,000 PSDs. The study focuses on cirrus clouds and provides heat maps illustrating PSDs across a range of temperatures and cloud thicknesses. Key findings include the identification of three characteristic ice crystal size ranges:

- Nucleation/Evaporation Size Interval (∼3–20 μm): Predominantly observed in the coldest and thinnest in situ-origin cirrus clouds.​

- Overlap Size Interval (∼20–230 μm): Characterized by the coexistence of both in situ-origin and liquid-origin cirrus crystals.​

- Uplift/Sedimentation Size Interval (>∼230 μm): Consists mainly of liquid-origin ice crystals.​

General comments

The use of a large data set (270 hours of measurements and ∼975,000 PSDs) is a significant strength of the study and the volume of data contributes to the robustness and reliability of the findings. The study’s focus on cloud particle size distributions (PSDs) in cirrus clouds is highly relevant for advancing the understanding of cloud microphysics, particularly in terms of how PSDs evolve with temperature and cloud thickness. The model based identification of the three main ice crystal size intervals is independent from observations which is definitely a weakness of the study. Nevertheless, the study provides first limited insights into the processes governing the formation and transformation of cloud particles under different environmental conditions. However, the major weakness of the study is the lack of quantification of in-situ and liquid-origin crystal number and mass fractions, which might have been an objective of the study, but this has not been pursued any further.

The effort of investigating quantitatively number and mass fractions of in-situ cirrus and liquid origin cirrus, derived from in situ and liquid origin crystal size distributions would give much more practical use (parameterisations) of these data to the modelling community.  Without this effort the authors cannot claim percentages of in situ and liquid origin crystal number percentages, as is presented in the text.

The additional work will be useful for climate modelers, as the detailed analysis of cirrus cloud microphysics could improve the representation of these clouds in global models. Also it is the third part of a series of papers, thus the authors should insist being more quantitative.

Criticism

It would be helpful to provide more detailed descriptions of the measurement methods used during the 270 hours of observation. Specifically, the instruments employed and any potential sources of error should be clearly discussed and quantified.

1. Line 65: how you differentiate liquid from ice and from mixed phase clouds in the observations?
2. How do you correct CDP / FCDP data for ice crystals? If not, what’s the error and consequences on PSD and subsequent interpretation?
3. Have 2DC images been reprocessed for under-sampling in flight direction due to smaller acquisition speed compared to TAS? How is this done? What’s the pixel resolution of the 2DC probe? Do you really believe in 60µm crystal concentration data from old 2DC? What would be the uncertainty in size and concentration
4. Also 2DS has considerable uncertainties below 100, if not 150µm. You really believe in 25 µm concentration data from those probes? Uncertainties have to be quantified here to judge on interpretation of subsequent results.

Likewise for the model: How realistic is the model as compared to other modelling efforts quantifying in situ versus liquid origin cirrus? What is the estimated error in your model with respect to calculated size thresholds? An answer to this question is necessary to make this study not just a qualitative one. As presented, you can’t say that below modelled crystal diameter thresholds the crystals are of in situ origin and above of liquid origin. You don’t state about overlapping size range.

Line 407: …. 15% / 30% of the data points are from liquid origin cirrus.  That’s wrong and authors should better not publish these percentages, the rest is not in situ cirrus percentages. Taking into account the overlapping size range of 20–230 μm for “co-existing” in situ and liquid origin cirrus, the mentioned fractions may be more like 50 / 75%, or even more? I feel that there is potential to do better. As it stands the study is qualitative. Can you delimit percentages a bit more, taking into account distributions crystals in overlapping in situ and liquid origin size ranges ?

That would make the study a much better paper, since more quantitative. In addition to corrected number fraction of in situ and liquid origin cirrus, what would be the corresponding mass fractions then? I’d like to insist that authors add an effort to argue percentages in number and mass, with underlying overlapping size distributions of the in situ and liquid cirrus crystal origins. This would make this paper a more valuable paper.

Specific comments

Line 25: Old ICCP report. Update with newer insights

Line 60: Improve differentiation between this study and Bartholomé Garcia et al (2024) publication

Line 106: What is the reason to use the mean mass radius/diameter and not the commonly used median mass radius/diameter

Line 117: What about in situ cirrus formed of bullet rosette type crystals formed in situ at -35°C?

Line 127: a new nucleation event… I don’t think that you can distinguish between in situ cirrus and liquid origin cirrus events. There might be rather a continuum with dominating in situ or liquid origin clouds in numerous cases of cirrus cloud formation.

Line 149: can you prove the argument with gravity waves? Otherwise skip…

Line 158: Please summarize numbers in Table 1 in few clear sentences!

Line 274: Mention mass diameter (which) relationship used here..

Line 2901-290: This sentence has to be written more carefully. We know about significant errors in PSD retrievals from OAP probes. Also you may hide factors of up to 5 in concentration differences between probe pairs in the transition size range on a log scale.

Line 329: It seems that you mis up aerosol spectra from optical spectrometer with cloud spectra, since the largest aerosol particles should be activated, no? What’s the consequence of that?

Line 327: Those larger droplets may produce secondary ice, thus your argument is not supportable…

Line 331: Why the Dollner (2024) algorithm is not applied then?

Line 345-348: Unclear sentence. Please clarify

Line 474-475: unreadable!

Figure 3: what is s09 what is MD, figure caption simply uncomprehensible

Figure 4a, then 4b,c : chose same colours for identical campaigns

Technical comments

Line 53 improve wording: …in dependence..

Line 83-84: sentence unclear

Line 107 discussion Fig 2: black and white contour lines almost invisible

Line 124: wording: ….on a time scale faster with….?

Line 126: wording: ….sediment out…

Line 128: wording: ….shrink back…

Line 157: wording: For an impression….

Line 240: replace should by is….

Line 242: replace ‘secondly’…

Line 373/ contour lines really hard to see