the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 May 2025
A radar view of ice microphysics and turbulence in Arctic stratiform cloud systems
Abstract. Ice microphysical processes are inherently complex because of their sensitivity to temperature and humidity, the diversity of ice crystal habits, and their interaction with supercooled liquid water (SCL) and turbulence. Long-term surface-based radar observations have been systematically used to unravel the different processes that affect ice particle growth. In this study, we present a statistical analysis of 6.5 years of Ka-band radar observations, combined with thermodynamic profiles derived from radiosonde measurements. For the first time, ice particle growth and sublimation—diagnosed from vertical gradients of radar reflectivity and mean Doppler velocity—are systematically mapped across a broad range of temperature and moisture conditions. These vertical gradients correspond closely with saturation levels relative to ice and exhibit a strong temperature dependence in supersaturated regions. Notably, distinct signatures near -15 °C are indicative of dendritic growth. Turbulence, quantified via the eddy dissipation rate (EDR), is most frequently observed in regions containing SCL. When SCL is located near cloud base, it often appears decoupled from high EDR values, suggesting that latent heat release from SCL alone is insufficient to generate strong turbulence. Instead, the presence of turbulence appears to actively support the formation and maintenance of SCL. The co-occurrence of SCL and elevated turbulence results in significantly enhanced ice particle growth compared to conditions in which either is present alone.
This work provides new observational constraints that are critical for improving the representation of ice microphysics in atmospheric models.
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RC1: 'Comment on egusphere-2025-2149', Peter May, 15 Jun 2025
This paper analyses a large volume of K-band radar data from the North Slope of Alaska ARM site and uses novel statistical methods to infer some key ice microphysical processes from the data. This is well within the scope of ACP and these broad statistical studies are to be encouraged. The analysis appears quite robust and I think this manuscript should be published with relatively minor edits. I also suggest that some discussion is made on the potential use of longer wavelength data given the quite large number of Microwave Rain Radars operating at high latitudes. For scatter from ice particles there should not be too much sensitivity.
There are a couple of gaps in the discussion. The introduction of Z being proportional to the sixth power of D is true for Rayleigh scatter, but scattering from ice crystals is much more complex with dependencies on shape, density and how much air is trapped than such a simple relation. There is an excellent discussion in Chapter 3 by Tynelä et al in the recent book, Volume 2 of Advances in Weather Radar edited by V.N Bringi, K.V. Mishra and M. Thurai. Likewise, the variations in(reflectivity weighted) fall speed for different crystals and the impact of this on the discussion and interpretation needs some further discussion. This discussion goes back a long way, at least to Locatelli and Hobbs (JGR, 1974). This is mentioned in the latter part of the manuscript, but again needs some more detail and nuancing.
The discussion on EDR retrievals also needs further explanation and what equations are being used? It is certainly different from spectral width based estimates. What is the confidence in these retrievals?
How robust is the “detection” of SCL? For samples where you argue that there is SCL near cloudbase, have you validated with lidar data? This would give more confidence to the conclusions. I certainly wouldn’t expect that turbulence contributes to the formation of SCL. In contrast, I thought it would increase collision rates and riming.
Minor comments:
Do you make a density correction for the fallspeeds? This will be needed for more quantitative discussion.
The colorscale of Fig 1, panel b should be changed so that detail between 0 and 1 m/s is more clearly visible.
Overall ratings:
Scientific significance: Excellent
Scientific quality: Good
Presentation quality: Good to excellent
Citation: https://doi.org/10.5194/egusphere-2025-2149-RC1 -
RC2: 'Comment on egusphere-2025-2149', Anonymous Referee #2, 22 Jul 2025
Review of Yan et al., ACPD 2025 (egusphere-2025-2149)
General comments to the manuscript
In the manuscript titled “A radar view of ice microphysics and turbulence in Arctic stratiform cloud systems” by J. Yan et al., the authors present a study on ice microphysics and turbulence in Arctic stratiform clouds, based on 6.5 years of Ka-band radar and radiosonde observations at the DOE ARM North Slope of Alaska site. The research focuses on understanding ice particle growth and sublimation processes (via tracking of vertical gradients of radar reflectivity and mean Doppler velocity), their temperature and moisture dependencies, and the role of turbulence in these processes.
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:
The literature study in the introduction should be extended to acknowledge further studies on secondary ice production (SIP, the process should be explained first, e.g. https://doi.org/10.5194/acp-20-11767-2020) as well as Hallett-Mossop ice splintering (also explain the process and add references) and also acknowledge studies that studied the influence of environmental conditions affecting SIP (e.g. https://doi.org/10.5194/acp-20-1391-2020, https://doi.org/10.5194/acp-21-14671-2021 among others).
Please make sure you use precise and consistent wording throughout the manuscript. E.g., on line 42 you state that you want to characterize the two ice processes depositional growth and sublimation while later on you also refer to aggregation and riming as ice microphysical processes. Please also try to improve readability in the result section as indicated by specific comments below.
The title states that only stratiform cloud systems are considered. I could not find a section that explains how convective clouds are filtered from the data set. – Please clarify/change title.
Minor comments:
Line 22: replace “vapors” with “water vapor”
Line 37-38: Unclear sentence, please rephrase. What do you consider as limitations of the dataset used in Chellini and Kneifel, 2024?
Line 40: remove “s” from multi-years
Line 41 (and elsewhere): replace radiosonde with radiosondes or “radiosonde observations” and add ceilometer (used in Fig 1a)
Line 48: Add an explanation why you limit your dataset to this specific time frame Jan 2013 – May 2019 instead of extending it to more recent data.
Line 50: reference missing
Line 62: after “grow” add “by water vapor deposition”
Line 66: Clarify what is meant by “overall”.
Line 66-71: This paragraph should acknowledge that besides high relative humidities, cloud condensation nuclei are required for the formation of liquid droplets. Also, consider shading the three defined moisture regimes in Fig 1 c).
Line 74: remove “And” at beginning of sentence, mixed-phase (instead of mix-phase)
Line 89: remove “or”
Line 90-92: Add that this assumption of negligible vertical air motion can be made for stratiform Arctic clouds but not e.g. deep convective systems and give references for other studies where this assumption has been used. Please also state at which altitude you start calculating the gradients – from radar echo top downwards or a certain height within the clouds?
Line 140: “for” temperatures instead of “with” temperatures
Line 142: remove sentence as it has same content as the one on line 140
Line 146: typo “riming”
Line 146-148: sentence unclear, please rephrase
Line 149-154: Please also describe the MDV decrease for the SCL condition in the dendritic growth zone around -15 C – it is even more pronounced than for ISO conditions.
Line 159: Since you are explaining ISO conditions, do you mean Fig 4c) instead of a)?
Line 155 – 169: Please improve the readability of this paragraph. Also, can you explain the other features shown in Fig 4 such as in Fig 4a) negative dBZ gradient for T > -10 C and small reflectivities; Fig 4b) strong positive MDV gradients for T -10 to -20 C and high reflectivities; Fig 4c+d: for T > -10C negative dBZ gradient and positive MDV gradient; Fig 4d: strong positive MDV gradients for T between -25 to -16 C and high reflectivities
Line 166-167: unclear sentence, please rephrase
Line 202+203: typo ice-subsaturated
Line 232-239: unclear sentences, please rephrase
Comments on Figures:
Fig 1: add which time is shown on x-axis (UTC?). in Panel c) and d) please add the SCL bases and tops as done in panel a) and b).
Fig 3: In the caption add the what the dashed red line “DI median” refers to (or replace by “ISO” ?).
Fig 5b: Replace “DI” with “ISO” in the legend
Citation: https://doi.org/10.5194/egusphere-2025-2149-RC2 -
AC1: 'Reply Letter', Jialin Yan, 06 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2149/egusphere-2025-2149-AC1-supplement.pdf
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