the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Mar 2026
Sensitivity of Arctic mixed-phase cloud simulations to ice microphysical modifications in the WDM6 scheme of WRF (v4.3.1)
Abstract. Arctic mixed-phase clouds (MPCs) remain challenging to represent in atmospheric models, with bulk microphysics schemes typically biased toward either excessive glaciation or inadequate ice formation. This study evaluates the behavior of the Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) scheme and its modified version (WDM6_ICE), which incorporates spherical ice shape, constrained nucleation, and prognostic cloud ice number concentration, under Arctic conditions using the Mixed-Phase Arctic Cloud Experiment case (9–10 October 2004).
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RC1: 'Comment on egusphere-2026-1486', Anonymous Referee #1, 30 Apr 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-1486/egusphere-2026-1486-RC1-supplement.pdfCitation: https://doi.org/
10.5194/egusphere-2026-1486-RC1 -
RC2: 'Comment on egusphere-2026-1486', Anonymous Referee #2, 14 May 2026
The authors have examined the influence of ice shape and ice nucleation parametrizations on cloud properties inside the WDM6 microphysics scheme in WRF. The manuscript is well written and of good scientific quality. However, there are some aspects that are not clear enough yet that I will list in the following comments.
General comments:
- I miss a clearer motivation for why ice shape is modified to begin with. Is spherical ice shape known to be more common than bullet rosettes or is the implemented change just to test what happens if ice surface area is minimized?
- The discussion part contains comparisons with other studies from the M-PACE campaign and that is good, but the manuscript could benefit from a broader picture. If the authors want to convey that their conclusions are only relevant for this specific cloud regime/case, that should be made clearer. On the other hand, if their conclusions should be valid more generally, it is necessary to better describe how the selected cloud case compares to others. Other cases may be other cases from M-PACE, but may also be cases from different Arctic campaigns (e.g. MOSAIC, NASCENT).
- Regarding the cloud droplet nucleation: Why was the minimum CCN number chosen to be 100 cm-3? The authors state that this is a higher value than realistic for Arctic conditions and discuss the implications, but I miss an explanation for why this value was chosen from the beginning. (Even if it simply is, because that’s the default value of the WDM6 scheme, this should be mentioned.)
Specific comments:
Abstract: I suggest to include in the abstract that this study analyses a case from the M-PACE campaign.
Line 42: What do you mean by “distinct ice representation behavior”? Please consider reformulation.
Line 50-52: This statement needs a reference.
Line 78: The city of Barrow is now called Utqiagvik.
Section 2.1/2.2: I think, the introduction of section 2.2 would better fit at the beginning of the whole Section 2. Maybe you could move it there or merge 2.1 and 2.2 in general?
Line 109: I am not sure if I understand what you mean by “Arctic boundary layer conditions” and suggest to reformulate.
Line 116: Correct the reference: Skamarock et al., not Wet al., 2021.
Fig. 2: Could you compare cloud fraction with ERA5 as well?
Line 189: Please start a new paragraph when starting to write about WDM6_ICE.
Line 208-209: Can you compare PBL with observations, too?
Line 235: It is quite a surprising finding that the LWC in WDM6_ICE is higher than in WDM6_SP_IN even though WDM6_ICE has more ice formation processes. Please highlight and try to explain, don’t just go on to IWC that quick.
Figure 7: To combine orange and green lines in a plot is not very colorblind-friendly. Please adapt your color choice.
Line 275-277: This is an interesting teaser. Could you expand a bit on the impacts of the remaining structural differences?
Line 308-311: This statement is too general in its current formulation. This sentence implies for example that secondary ice production is “effectively inactive under the present Arctic conditions”. While this might be true for the studied case, many other studies find that secondary ice production is important in Arctic mixed-phase clouds. Please change accordingly.
Line 318, 330, and more places: In the majority of the manuscript, processes are abbreviated with capital letters, but not in these lines. Please make that consistent across the whole manuscript.
Citation: https://doi.org/10.5194/egusphere-2026-1486-RC2
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