the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Oct 2023
Spatial spin-up of precipitation in limited-area convection-permitting simulations over North America
François Roberge
Alejandro Di Luca
René Laprise
Philippe Lucas-Picher
Julie Thériault
Abstract. A fundamental issue associated with the dynamical downscaling technique using limited-area models is related to the presence of a “spatial spin-up” belt close to the lateral boundaries where small-scale features are only partially developed. Here, we introduce a method to identify the distance from the border that is affected by the spatial spin-up (I.e., the spatial spin-up distance) of the precipitation field in convection-permitting model (CPM) simulations. Using a domain over eastern North America, this new method is applied to several simulations that differ on the nesting approach (single or double nesting) and the 3-D variables used to drive the CPM simulation. Our findings highlight three key points. Firstly, when using a single nesting approach, the spin-up distance from lateral boundaries can extend up to 300 km (around 120 CPM grid points), varying across seasons, boundaries, and driving variables. Secondly, the greatest spin-up distances occur in winter at the western and southern boundaries, likely due to strong atmospheric inflow during these seasons. Thirdly, employing a double nesting approach with a comprehensive set of microphysical variables to drive CPM simulations offers clear advantages. The computational gains from reducing spatial spin-up outweigh the costs associated with the more demanding intermediate simulation of the double nesting. These results have practical implications for optimizing CPM simulation configurations, encompassing domain selection and driving strategies.
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François Roberge et al.
Status: final response (author comments only)
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CEC1: 'Executive editor comment on egusphere-2023-1512', Astrid Kerkweg, 23 Oct 2023
Dear authors,
in my role as Executive editor of GMD, I would like to bring to your attention our Editorial version 1.2:
https://www.geosci-model-dev.net/12/2215/2019/
This highlights some requirements of papers published in GMD, which is also available on the GMD website in the ‘Manuscript Types’ section:
http://www.geoscientific-model-development.net/submission/manuscript_types.html
In particular, please note that for your paper, the following requirements have not been met in the Discussions paper:
- "The main paper must give the model name and version number (or other unique identifier) in the title."
- "If the model development relates to a single model then the model name and the version number must be included in the title of the paper. If the main intention of an article is to make a general (i.e. model independent) statement about the usefulness of a new development, but the usefulness is shown with the help of one specific model,the model name and version number must be stated in the title. The title could have a form such as, “Title outlining amazing generic advance: a case study with Model XXX (version Y)”.''
- "Code must be published on a persistent public archive with a unique identifier for the exact model version described in the paper or uploaded to the supplement, unless this is impossible for reasons beyond the control of authors. All papers must include a section, at the end of the paper, entitled "Code availability". Here, either instructions for obtaining the code, or the reasons why the code is not available should be clearly stated. It is preferred for the code to be uploaded as a supplement or to be made available at a data repository with an associated DOI (digital object identifier) for the exact model version described in the paper. Alternatively, for established models, there may be an existing means of accessing the code through a particular system. In this case, there must exist a means of permanently accessing the precise model version described in the paper. In some cases, authors may prefer to put models on their own website, or to act as a point of contact for obtaining the code. Given the impermanence of websites and email addresses, this is not encouraged, and authors should consider improving the availability with a more permanent arrangement. Making code available through personal websites or via email contact to the authors is not sufficient. After the paper is accepted the model archive should be updated to include a link to the GMD paper."
As your study is based on simulation of the CRCM6/GEM5 model please add something like "a case study based on CRCM6/GME5 model results" to the title of your article. Additionally, please add the information how to access the (exact version) of the model code in the code and data availability section.
Yours,
Astrid Kerkweg
Citation: https://doi.org/10.5194/egusphere-2023-1512-CEC1 -
AC1: 'Reply on CEC1', François Roberge, 30 Oct 2023
Dear Executive Editor,
Thank you for your feedback. We have now incorporated the source code of the model used for our experiments into a version control system on Git, with the following DOI: https://doi.org/10.5281/zenodo.10054619 .
Once we receive all reviewers' comments, we will update the manuscript as requested. This includes adding the model's name and version to the title and including the DOI for the source code.
Thank you very much,
François RobergeCitation: https://doi.org/10.5194/egusphere-2023-1512-AC1
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RC1: 'Comment on egusphere-2023-1512', Anonymous Referee #1, 09 Nov 2023
Dear authors,
I want to add some suggestions to your work that I think it’s generally relevant for CPM modelers in order to have more efficient dynamical downscaling strategies, since the spatial spin-up issue is often handled with generic suggestion and not very in-depth analysis.- The definition of spatial spin-up is often directly managed by individual models, where it is possible to set some parameters for relaxation layer. For this reason I believe that the model description section should be expanded with a particular focus on this settings.
- Add additional multimodel CPM initiatives, e.g. CORDEX Flagship pilot studies on convection ( Coppola et al. 2019)
- I appreciate the section “Implications of the spatial spin-up for computing resources” because it’s fundamental in the Convection permitting experiment and in particular the information on the data size. The more demanding storage requirements is related to the production of 3D boundary data.
- It’s relevant to integrate this evaluation on other variables that’s important especially in the configuration of the climate experiment. So, this method is fundamental to assess a good quality of analysis but it needs a more robust integration and consideration in the definition of nesting strategies.
Citation: https://doi.org/10.5194/egusphere-2023-1512-RC1 -
RC2: 'Comment on egusphere-2023-1512', Anonymous Referee #2, 24 Nov 2023
- General comments
Thank you for providing an interesting and thought-provoking article on the spatial spin-up of precipitation in convection permitting model domains. Overall, I think that the article is of a high-quality and the experimental design is efficiently described with results of relevance to the wider CPM community discussed. I find the discussion of relative computational costs of different CPM configurations to be a useful addition to the article and thank the authors for including it. I have a few comments and suggestions for possible extensions below – some of these may be appropriate for future work considerations rather than in the current article.
- Specific comments
Have the authors considered how the spatial spin up of precipitation will vary according to the region a CPM is located e.g. tropical vs mid-latitude. As the authors state, the SSUD will be dependent on inflow so possibly larger in mid-latitude CPM domains but then perhaps the change from predominantly frontal rainfall in the mid-latitudes to deep convection in the tropics is also important? Perhaps it takes a larger number of grid points to spin up realistic deep convective structures in the tropics (particularly when nesting a CPM inside a coarse resolution GPM that parameterises convection). Maybe the authors could add a comment or sentence in the conclusions on whether they think their results are applicable across all CPM domains?
In the model description section I wonder if the authors would consider adding a table outlining the similarities and differences between the GEM12 and GEM2.5 models e.g. detailing differences in horizontal and vertical resolution, the convection parameterisation schemes, the cloud microphyics schemes. I think the inclusion of such a table would allow the authors to reduce the amount of text between lines 120 and 151.
I wonder if in your conclusions section you would want to make a stronger statement about the minimum number of grid points that should be removed prior to analysis for single nested experiments investigating precipitation e.g. “given the results shown here for mid-latitude RCM experiments using a single-nested technique a minimum of 50 grid points should be removed at the inflow boundary(ies) prior to analysis of the precipitation field”. I understand if you don’t want to make this point too strongly, but it may be useful to other researchers if a minimum value was outlined that could be adopted if using a single nested approach.
In the final sentence of your conclusion you state that “the determination of SSUD values is based on seasonal mean variable and thus we should expect SSUD values to be larger in some specific situations.” – could you provide some example meteorological situations where you’d expect the SSUD to be larger than the seasonal mean?
In Figure 3 – consider the ordering of your panels, I think it might be more logical to the reader if ERA-5 precip is in the top left panel.
In Figure 4 – would it be more useful to show these panels for the full domain i.e. x axis just becomes e.g. number of grid points from southern border – then the reader can see the relative magnitude of spin up at both northern (western) and southern (eastern) boundaries on a single panel?
Figures 4 and 5 – consider whether you can differentiate more clearly between the two GEM2.5 configurations shown. Particularly in Fig. 5 as for the solid horizontal lines showing the standard deviation of the relative difference are hard to see which line refers to which model.
Could your naming convention of the different simulations be made clearer and more concise for the benefit of the reader? E.g. removal of the GEM12 section of the naming GEM2.5 (GEM12_SU) could become GEM2.5 SU? (as long as it remains clear that the change is to the parent model and not the GEM2.5 simulations)
Line 120 – “Two versions of the CRCM6/GEM5 model are used in this study 120 and differ mainly in their horizontal resolution.” – I would consider revising this sentence, I understand what you are trying to say but I think the differences between GEM12 and GEM2.5 are larger than this – particularly thinking about the parameterisation of convection. I think the idea of having a table outlining the differences between GEM12 and GEM2.5 (see above) would be helpful.
- Technical corrections
Line 59 – “The Big Brother and(?) idealized CPM simulations…”
Section 2.3 – could the section header title be more informative – e.g. “Experimental design of simulations”
Line 191 – Consider using “All four GEM2.4 (GEM12_P3xx)” rather than “All 4”
Line 218 – “While GEM2.5 precipitation fields (left panels)” – shouldn’t this read ““While GEM2.5 precipitation fields (top row)”?
Line 308 – Delete “egligible”
Citation: https://doi.org/10.5194/egusphere-2023-1512-RC2
François Roberge et al.
François Roberge et al.
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