Evaluation of the Sea-Ice Simulation in the Upgraded Version of the Coupled Regional Atmosphere-Ocean- Sea Ice Model HIRHAM–NAOSIM 2.0

Round  1

Reviewer 1 Report

The authors described the upgraded version of the coupled Arctic atmosphere-ocean-sea ice model HN2.0. And through the comparisons with the old version, we could see amounts of improvements. And all the contents, improvements already made and other aspects need additional improvement, are fully described in the manuscript. I am pleased to say, the manuscript could accept as it is.

Author Response

Comments and Suggestions for Authors

The authors described the upgraded version of the coupled Arctic atmosphere-ocean-sea ice model HN2.0. And through the comparisons with the old version, we could see amounts of improvements. And all the contents, improvements already made and other aspects need additional improvement, are fully described in the manuscript. I am pleased to say, the manuscript could accept as it is.

Response to the Comments and Suggestions

We thank the reviewer for his/her pleasant rating of the manuscript.

Reviewer 2 Report

I have read “Evaluation of the Sea-Ice Simulation in the Upgraded Version of the Coupled Regional Atmosphere-Ocean-Sea Ice Model HIRHAM-NAOSIM 2.0” by Dorn et al.  The manuscript describes the latest version of the model and compares newly generated results with the previous generation HIRHAM-NAOSIM 1.2 (HN1.2).  Overall, the paper is well-written logically oriented.  The description of model improvements in HN2.0 from HN1.2 appears detailed and well-defined, though I would default to the opinion of a reviewer with more model customization experience.  The comparisons between the HN2.0, HN1.2, PIOMAS, and satellite ice data are interesting and the model improvements are well supported by time series (e.g. Fig 5) and maps (e.g. Fig 7) and supporting text.  

My suggestions for a more comprehensive set of results would be:

1) Add sea ice area and extent correlations analogous to those presented in Table 2

2) Clarify/posit why HN2.0 ensemble September sea ice area and extent displays higher biases over the last two decades relative to HN1.2 (Fig 5)

3) Show a September map for an extreme melt year (i.e. 2012) or composite maps (since 2007) of HN2.0 and HN1.2 versus PIOMAS and satellite observations to highlight the regional areas of bias.  

These additions would further highlight and quantify improvements/changes in the newest iteration of HIRHAM-NAOSIM relative to the previous version and be of interest to researchers possibly looking to apply the model toward understanding sea-ice-ocean-atmosphere interactions, especially for regional case studies (i.e. Greenland Ice Sheet and Baffin Bay early melt in 2019).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper is well written, but there are several grammatical errors in sentence construction making it rather hard to read. I have caught a few of these in my comments, but I advise the authors to be more grammatically thorough in their presentation. 

The results described are worthy of publication. The article however was almost too technical with respect to describing the model development and modeling parameters used in the study. The authors can move some of the technical description in the appendices, and perhaps elaborate a little more  "science" results (sections 3.3 to 3.6). Otherwise, it is ready for publication. Please find my comments below for revision.

1.     Comment 1: Line 19: “….but a variety of other feedbacks exist many of which are not yet  understood in detail, for instance the feedback between sea ice and cyclones”.

2.     Full-form of abbreviation YAC should be provided in abstract as well as in line 328.

3.     Line 390: Remove the word “equally”.

4.     Section 3.2. Kindly check the correct format for citing a website in text.

5.     Line 416: Change to “Nevertheless, the near-surface air temperature bias compared to observations is smaller in ERAI than in other reanalysis products [60].”

6.     Line 477-484: Why is the correlation coefficient and interannual variability calculated for only sea-ice volume? What about sea-ice extent and area?

7.     Figure 7 caption: “PHC3.0 data were interpolated to the T-grid of HN2.0”. Were the data only interpolated to the HN2.0 grid, or for both model (HN1.2 and HN2.) grids? As the model grids differ between the two versions, it is necessary to clarify.

8.     Line 552: “Both HN2.0 and HN1.2 show on average temperatures  below 0 ◦ C in this region which are here around 1.3 ◦ C colder than ERAI”.

9.     Line 557: “Even though this temperature bias is low, it might have consequences for the way how sea ice is melting in the model”.

10.  Line 558: “Due to the air temperatures being below 0 ◦ C, melting of the snow/ice pack from above  is reduced and melt ponds are underrepresented”.

11.  Line 560: Potentially, a restriction of the decrease in sea-ice concentration when melting conditions occur could contribute to reducing both the open water bias and the temperature bias”.

12.  Line 606: Please check grammar. “…which also accounts for to date disregarded form drag caused by the edges of ice floes and melt ponds.” This part of the sentence reads grammatically incorrect.  

13.  Line 617: Discussions based on how such a nonuniform ice thickness distribution can be implemented in  the atmospheric component HIRHAM5 are underway.

14.  Line 619 and throughout section 4: Please check grammar.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf