|Review of “Northern Hemisphere storminess in the Norwegian Earth System Model (NorESM1-M)” by E. M. Knudsen and J. E. Walsh|
The authors have made considerable changes and improvements to this manuscript after the first set of reviews. There is now a lot more information, fuller discussion of the results in the context of previous work, and more figures.
I think the authors have satisfactorily responded to most of the reviewer comments. There are still some issues that need to be addressed, most of which are fairly minor.
1. The authors state in the responses to the reviewer comments regarding the link between sea ice loss and storminess: “However, as the main focus in this manuscript is on representation of storminess in NorESM in historical and future climate, we consider such an analysis outside the scope of this study.”
Based on this and the title of the paper, I wonder why the first paragraph of the introduction to the paper is all about sea ice loss. I think the introduction needs to be restructured to introduce the most important aspect first. The sea ice loss may then motivate the region of focus.
2. I find that having a “Results and discussion” section rather than “Results”, then “Discussion” makes the results hard to follow. I would suggest restructuring this section somewhat, to present the results in a simple way, then have a section discussing the context and comparison with other studies and the implications of the results. An example is the second paragraph of section3, where the discussion of the comparison with Catto et al and Zappa et al might be better later.
3. Line 57: “decreasing September sea ice edge” might be better as “retreating September sea ice edge” or “decreasing sea ice edge extent.
4. Lines 83-95: There are also energetic arguments for the changes (see O’Gorman and Schneider (2008) for a good additional reference here).
5. Section 2: This section would be much easier to read if there were some subheadings, such as “Models”, “Sea Ice Data”, “Methods”.
6. Lines 159-174: Can you say somewhere in this section what the difference between sea ice concentration and sea ice extent is, how are each of them used in the study, and from which datasets?
7. Lines 180-182: These lines could be made clearer. Is it that the vorticity method identifies more cyclones than a SLP method, but there are other methods that identify even more cyclones?
8. Line 208: There are more recent polar low climatologies that you could also include here – Yanase et al (2016) and Zappa et al.
9. Line 227: The intermediate scenario in that study was a 2XCO2 idealized scenario, which is different to the scenarios investigated here. This would be worth noting and bearing in mind.
10. Line 231: It is not clear what is meant by “diverging” here.
11. Section 3: It gets quite confusing jumping between the main figures and the appendix figures. Would it be possible to have the extra figures as part of the body of the manuscript?
12. Lines 273-276: This jumps around between sea ice concentration and sea ice extent, which is quite confusing.
13. Line 279: “discrepancy” would be clearer as “positive bias”.
14. Line 283: “The signal…” of what?
15. Line 311: Please be clear what is meant by “coherent”.
16. Line 374-376: Catto et al 2015 also showed that the precipitation biases are larger for light precipitation, but heavier frontal precipitation is well represented.
17. Section 3.2: When giving the percentage changes for September and December in brackets, it would be good to make it clear that this is what they refer to (at least the first time).
18. Line 435: “While more cyclones are expected…” Why is this expected?
19. Line 491: “thus foster the cyclones.” Are you saying this is the cyclogenesis mechanism? I don’t think the word “foster” is a good one here – it is not clear what is meant.
20. Line 529: Have you seen in your data a decrease equatorward of 40 degrees N? If you have seen it but are not showing it in a figure, I would just say “not shown”. If you haven’t seen it, I would remove this.
21. Section 4: The first two bullet points of the conclusions are related to sea ice. Again, since the focus of this paper is on the storminess, these bullet points need to be revised.
22. Line 616: “where cyclones foster from…” should be “where cyclones are generated by…” or something similar.
Catto, J. L., C. Jakob, and N. Nicholls (2015), Can the CMIP5 models represent winter frontal precipitation?, Geophys. Res. Lett., doi: 10.1002/2015gl066015.
OGorman, P. A., and T. Schneider (2008), Energy of midlatitude transient eddies in
idealized simulations of changed climates, Journal of Climate, 21 (22), 5797–5806, doi:10.1175/2008JCLI2099.1.
Yanase, W., H. Niino, S.-I. I. Watanabe, K. Hodges, M. Zahn, T. Spengler, and I. A. Gurvich (2016), Climatology of polar lows over the Sea of Japan using the JRA-55 reanalysis, J. Climate, 29, 419–437, doi:10.1175/JCLI-D-15-0291.1.
Zappa, G., L. Shaffrey, and K. Hodges (2014), Can polar lows be objectively identified
and tracked in the ecmwf operational analysis and the era-interim reanalysis?, Monthly Weather Review, 142 (8), 2596–2608, doi:10.1175/MWR-D-14-00064.1.