| 30 Jun 2025
Future Rime Ice Conditions for Energy Infrastructure over Fennoscandia Resolved with a High-Resolution Regional Climate Model
Abstract. Societies today are increasingly reliant on electricity, underscoring the need for reliable energy production. In cold climate regions, ice accumulation can cause significant harm to structures such as power transmission lines, leading to power loss or, in the worst case, the collapse of wires or transmission towers. Thus, since climate change is expected to impact winter weather conditions in northern Europe, its effects on atmospheric icing occurrence over the Fennoscandian region is a crucial area of study. Here we utilize an ice accretion model based on ISO 12494, driven by outputs from the high-resolution regional climate model HCLIM, to analyze in-cloud icing conditions over two twenty-year periods: mid-century (2040–2060) and end-of-century (2080–2100). The regional outputs are bounded by two global climate models (EC-EARTH and GFDLCM3, respectively) under the highly warming RCP 8.5 emission scenario. The results suggest a general decrease in in-cloud icing conditions over northern Europe compared to the historical period (1985–2005). An exception lies in the northern parts of Fennoscandia and locally over higher altitudes, where some increasing trend is seen, particularly for annual maxima. Under the RCP 8.5 scenario, freezing temperatures become less common; however, rising temperatures allow for more moisture, potentially enhancing in-cloud icing if enough freezing temperatures remain.
The authors provide possible future climate change effects on icing conditions over Fennoscandia, a issue specifically relevant for the energy industry. The study is generally carried out properly, well written and reveals relevant results for the region.
I have only one major and some minor points and suggestions to the text to be considered before the manuscript may be accepted for publication.
Major point
Please double check the absolute units/amount you get for ice masses. The values you show for instance in Figure 4a) and 4c), Table 2 and Figure A1 are very low compared to e.g. Iversen et al. 2023, considering that an ice load < 1kg would not be an issue I guess and that a max icing thickness of 70 mm is shown in Fig. 4d). Also, I think in Fig 4a) and 4c), the unit should be [kg/m] not [kg].
Suggestions to the text
Abstract
l6: two twenty-year periods -> two future twenty-year periods
1. Introduction
l54: expense of small ensemble size. -> expense of a small ensemble size and usually shorter time periods.
2.1 Rime ice model
l68: close to 1 for large particles (for which inertia dominates) and vice versa for small particles -> close to 1 for large particles (for which inertia dominates) and close to 0 for small particles.
2.2 HARMONIE-Climate
l96: EC-EARTH shows a colder and drier response to climate change in northern Europe compared to GFDL-CM3. -> May be confusing or interpreted as EC-EARTH showing a cooling and drying. Maybe change to "EC-EARTH shows a more moderate warming and increasing humidity response to climate change in northern Europe than to GFDL-CM3."
l103: I would drop the "business as usual" remark for RCP85. It is a debated term and it does not add any relevant information.
l104: A similar remark; whether "RCP 8.5 is considered to be increasingly unlikely" is also disputed, I'd say. I don't think there is a common agreement on this. Especially taking recent global developments into account. -> "Although RCP 8.5 may be considered to be increasingly unlikely ..."
l105: "it remains to be an useful tool for" -> "it remains a useful tool for"
2.3 Processing of the ice model outputs
l109: 1) results calculated for 50 meters -> 1) results calculated for 50 meters above ground
l117: calculated from all heights -> calculated for all heights
l118: a maximum of all grid points -> the maximum of all grid points
3.1.1 Fennoscandia (50 m) -> Fennoscandia (50 m height)
l148: the GFDL-CM3 boundary model -> the GFDL-CM3 boundary data
3.1.2 Test areas 6–7: Power line perspective (50m)
l176-180: "In box plots ..." -> You may consider dropping the description of the figure (e.g. "solid lines" etc.) in the text and leave it to the caption of the figure.
l187: both model configurations show increase -> both model configurations show an increase
l192: "Yellow represents the historical period, red the mid-century, and black the end-of-century." -> Again, consider dropping the description of the figure in the text and leave it to the caption of the figure.
3.1.3 Test areas 1-5: Wind power perspective (50-400m)
l209: The mean value is highlighted with a diamond symbol. -> Again, consider dropping the description of the figure in the text and leave it to the caption of the figure.
3.2.1 Temperature
l249: In Fig. A3 -> In case you have not reached a figure limit, move this to the main text. It seems relevant information for the main text to me.
3.2.2 Liquid water content
l265: "LWC only included the cloud liquid water content (CLWC) because cloud rain water content (CRWC) was not available in the pre-calculated HCLIM data. Thus, the modeled atmospheric ice type is primarily rime ice." -> I don't entirely understand what you refer to with cloud rain water content (CRWC) and how it relates to total LWC. Please explain in more details (maybe refering to relevant literature) and maybe move this part to section 2.
3.2.3 Wind speed
l275: where the possible ice forms. -> "where ice may form." or "where it may turn into ice."
4 Conclusions
l333: "is a business-as-usual scenario" -> (maybe) consider changing it to a more neutral term, e.g. "is a high emission scenario"
Table 1: the domains to which -> the domains for which
Table 2 and A1- A4: Please add the units of IM, IE and IH to the table. Either in the table or the caption.