Dear Dr. Gilbert,

I thank the reviewer for her generally positive review as well as the helpful feedback and suggestions, the majority of which are related to language and clarity and would be included in a revised version of this paper. Of the two main substantive critiques, several additional details are provided below:

Addressing the request for different resolution:

The model cost for these runs is prohibitive over the full Antarctic domain, thus multi-year runs (any meaningful ensemble size) over even higher resolutions (such as a 0.1 degree) were unrealistic. However, very-high resolution runs are currently being evaluated over other regions, and I’m optimistic that those analyses may contribute to the possibility of nested runs over Antarctica in the future. However, a related issue is disambiguating the impact of resolution vs dynamical core. A revised version would include a short comparison of 1° resolution runs with both dynamical cores (not initially included due to space considerations)

We also agree that placing these results into the context of previous work (e.g. Mottram et al. 2021) provides a better context for how VR-CESM2 compares with other models, and we would directly compare our results here with those results.

Thank you again for your time and attention.

Sincerely,

R. Tri Datta

Dear Reviewer,

Thank you for your taking the time to provide a thoughtful and constructive review. In advance of doing additional analyses and making specific corrections to the manuscript, we address a few of your major concerns here:

1) Previous work with a stretched grid vs. refined resolution:

Our interpretation of the main critique here is that, as a stretched grid format has been previously presented by earlier work, a variable-resolution grid over Antarctica is not new. While a revised version of the paper will discuss the difference in more detail (with better referencing and placing in the context of  previous work), the key differences are noted here:

a) This is not a stretched grid (or a nested grid), but a regional refinement – adding resolution over the most salient region of study (rather than redistributing resolution), though like the stretched grid, this preserves two way interactions over the globe. This means that it can more easily be linked to studies with the standard 1° resolution used in, say, CESM2 (although this is with the standard FV dycore).

b) In this case, the enhanced resolution is applied over both Antarctic continent and the Southern Ocean domain, thus capturing regions with evolving sea ice conditions (a regional refinement which will be valuable for future work)

c) Finally, the grid refinement here approaches the 0.25° resolution of reanalysis products as well as higher-resolution RCMs (e.g. RACMO or MAR). This is particularly relevant to regions with variations in fine-scale topography (e.g. the Antarctic Peninsula and portions of W. Antarctica). By comparison, the previous work with a stretched-grid approached a maximum resolution of 1° below 60° and a minimum resolution as high as 5° (see Fig. 1 from Genthon et al., 2002) or a maximum resolution of 60km (Krinner et al., 2014). While enhancing resolution itself in an ESM is not new, this manuscript introduces a regional refinement over Antarctica approaching that of RCMs.

2) References to earlier work using a stretched grid:

This was an oversight on our part which will be corrected in the revised version the paper. 

3) A more rigorous examination of general circulation

We agree that the manuscript would benefit from a more in-depth analysis of key features of general circulation. We have begun some additional diagnostics from what was already in the supplemental material.

4) A disambiguation of the effects of dycore vs resolution:

We omitted this discussion from this paper primarily because the relative impact of a change in dycore vs resolution in a polar region is discussed extensively in Herrington et al., 2022, although this in Greenland. However, similar experiments have been done over Antarctica and these will be analyzed and discussed in a revised version.

5) The use of AWS stations to discuss near-surface winds

A comparison between the ANTSI grid and AWS data was in a draft version of the manuscript (as in Fig.9b, but for wind) and will be included in the revised manuscript for thoroughness.

References:

Genthon, C., Krinner, G., & Cosme, E. (2002). Free and Laterally Nudged Antarctic Climate of an Atmospheric General Circulation Model. Monthly Weather Review, 130(6), 1601–1616. https://doi.org/10.1175/1520-0493(2002)130<1601:FALNAC>2.0.CO;2

Herrington, A. R., Lauritzen, P. H., Lofverstrom, M., Lipscomb, W. H., Gettelman, A., & Taylor, M. A. (2022). Impact of grids and dynamical cores in CESM2.2 on the surface mass balance of the Greenland Ice Sheet. Journal of Advances in Modeling Earth Systems, n/a(n/a), e2022MS003192. https://doi.org/10.1029/2022MS003192

Krinner, G., Largeron, C., Ménégoz, M., Agosta, C., & Brutel-Vuilmet, C. (2014). Oceanic Forcing of Antarctic Climate Change: A Study Using a Stretched-Grid Atmospheric General Circulation Model. Journal of Climate, 27(15), 5786–5800. https://doi.org/10.1175/JCLI-D-13-00367.1

Thank you for your time and consideration.

Sincerely,

Rajashree (Tri) Datta