This study presents interesting insights that could be valuable for the WRF modeling community, particularly in an understudied region. While the data and modeling approach are generally sound, several areas need improvement before publication.

Firstly, the structure and writing style require significant enhancement to meet publication standards. The results should be more detailed, offering specific recommendations—such as which schemes or combinations of schemes to use and which ones to avoid. Additionally, there should be greater emphasis on the processes driving these extreme rainfall events and how these processes are represented in the simulations. Finally, it is essential to identify and highlight key limitations of the study.

Please see the attached comments and also consider the following major points:

- Please use standard terminology (e.g., “Planetary Boundary Layer – PBL” or “convection-permitting”).

- The way of phrasing the aims of the study (i.e., using research questions) is not appropriate for a scientific article. In addition, some of these questions are not so relevant and could be removed (e.g., #10.”How generalizable are our findings?”). The same applies to section or sub-section headings, and the Conclusions, where I would avoid using questions.

- More information should be provided on why the selected processes (PBL and cloud microphysics) were investigated. How do these parameterizations influence the simulation of precipitation? For example, elaborate on what a single and a double moment scheme is. Are there other processes relevant (e.g., convection in the coarser-resolution domain)?

- The selection and definition of extreme cases is problematic, since for many events there is unknown information on the observed precipitation amounts (Table 2). I recommend including an additional column which will show the IMERG nearest grid-cell precipitation.

- It is also unclear if any events lasted more than one day, and if yes, how were these events treated in the analysis? Is one day of spin-up time enough for these runs?

- For extracting the overall statistics, all events were weighted equally. However, in the interpretation of  results, it would have been useful to differentiate, for example, between the most and the less extreme events, or between events affecting different parts of the Arabian Peninsula.

- More information on the interpretation of KGE should be provided in Section 3.5. Some references to other studies that use KGE in a spatial context could also be added. Moreover, I strongly recommend using additional evaluation metrics and not relying only on KGE for your conclusions.  

- Extensive parts of Section 4 are not results (e.g., L148-161, L217-222, L275-280, L326-332). Please move this and other non-results material to the introduction, data or discussion sections, if relevant.

- The approach described in lines 251-257 should be presented in more detail in the Methods section.

- Figures 6 and 7 should be merged to facilitate the comparison between observations and simulated rainfall. Please be consistent in the date format (panel titles).

- Sections 4.9 and 4.10 are definitely not results material. Please move to other more relevant section(s).

General Comments

The authors present a valuable study investigating the performance of the Weather Research and Forecasting model (WRF) over the Arabian Peninsula. They did an extensive evaluation of various cloud microphysics (MP) and planetary boundary layer (PBL) with respect to precipitation and standard meteorological variables like near-surface temperature, humidity, and wind speed by means of most recent satellite and in situ data.

In fact, there are not that many extensive studies on the performance of model physics of extreme rainfall events over the Arabian Peninsula (AP). As shown by the authors, different combinations of physics schemes can lead to considerably different results which makes it difficult to use numerical weather prediction (NWP) model simulations for early warning systems.

I clearly see the benefit of such an extensive model evaluation over arid regions, however a major point of concern for me is the experimental setup. While I clearly understand the purpose of applying ERA5 as forcing data, it is critical to apply only 53 model levels on a convection permitting resolution. Several studies, also with other NWP models like COSMO (e.g., Schär, C., and Coauthors, 2020: Kilometer-Scale Climate Models: Prospects and Challenges. Bull. Amer. Meteor. Soc., 101, E567–E587, https://doi.org/10.1175/BAMS-D-18-0167.1.) show that a higher vertical resolution is beneficial on a convection-permitting horizontal resolution.

Also the work of Schwitalla et al. (2020), which was mentioned in Table 1, applied 100 levels at a horizontal resolution of 2700 m. In my opinion it is necessary to have this layer density as, you mentioned this is your manuscript, the AP is usually very dry but you have an extremely strong vertical temperature and moisture gradient, especially near the coast which in case the winds are coming from the sea. This gradient is unlikely to be captured with only 53 levels.

Please make sure that you clearly distinguish between “schemes” and combinations as this is very confusing for the reader.

Please make sure that you do not repeat the explanations of the MP and BL option combinations. Explaining them once and then use “MP8_BL1” throughout the manuscript should be sufficient. Figure captions in the continuous test should start with “Fig.” instead of “Figure”. “Figure” is only used at the beginning of a sentence.

What is your final recommendation regarding the combination of PBL and MP? This should be mentioned as this is an important outcome of your study.

Specific comments:

Manuscript title: Please include the WRF version you are using as different WRF versions can lead to different results.

Line 5: I think “convection-permitting” is more widely used than “convective-permitting”.

Line 11: Where are the “21” combinations are coming from? The abstract suggest you performed 36 combinations.

Line 20: Are there more recent publications which cover the aspect of climate change?

Line 33: “can feed early warning systems”

Line 36: “inform” seems not an appropriate word here.

Line 37: The acronyms “AP” and “WRF” are not explained. Please ensure that all acronyms are explained before they are used in the manuscript. Also add the reference for the WRF model here.

Line 37: “Numerical Weather Prediction (NWP) model”…

Line 41: The microphysics also have an impact on radiation.

Line 53: “to evaluate the best combination”….

Line 56: “using WRF in a two-way nested”… What was your motivation to apply a two-way nesting approach?

Line 66: I do not think that number 9 is a key question of your study.

Line 69: “spans from 16°N to 33°N and 34°E to 56°E”

Starting line 73: The readers may be not familiar with all the different regions of the Arabian Peninsula and Saudi Arabia. I think it would be good to add at least some of the regions and major cities you mentioned to Fig. 1.

Table 1: The study of Schwitalla et al. (2020) is the only experiment in your table with a convection-permitting model resolution. This should be mentioned in the table itself (maybe as a separate column) and/or in the text. Please consider to add the number of model layers of the different studies as this can help the reader to further interpret your findings.

Line 94: Did you use ERA5 pressure or model level data for the initialization of the model? This has influence on the accuracy of the initial conditions as the number of model levels in ERA5 is about 100 up to 30 km while the number of pressure levels is 32 up to approx. 30 km altitude. If you use pressure level data, please explain your decision.

Line 101: Radiosonde stations are plotted in Fig. 1 but were never used or described explicitly throughout the manuscript. Or are they included in the analysis shown in sec. 4.6? If yes, I think it is dangerous to combine them together as you would combine prognostic (3D) variables with diagnostic (2D) variables. Did you consider differences between the station altitude and the model orography in case stations are located in the mountains? If this difference is large, this can alter your results for T, RH, and WS.

Line 108: WRF version 4.4.0?

Line 110: Please add the corresponding number of grid cells and the model top pressure here and to Table 3.

Line 120: The Kessler scheme is an extremely old scheme. Please consider whether it is necessary to apply this in your study on a convection-permitting resolution. It is preferably used in idealized cloud modeling studies.

Line 130: the simulations were run for 84 hours with a 48 hour spin-up followed by a 24h forecast. Why did you run the model for 84 hours? Did you reinitialize the atmosphere after your 48h spin-up?

Figure 1: Please use a different color table as there is too much blue color in the figure. Depending on the printer, it can be difficult to see the red markers on a blue background. Also, add the METAR stations here as this is important for the interpretation of your results.

Table 2: It would be great if you could add the rainfall amount for all cases. Otherwise it is difficult for the reader to judge the level of extreme of the particular event. It really matters if you have 200 mm within a day of more than 40 mm in 30 min.

Table 3: Does the Arakawa-C grid play a role in your study? As far as I know it cannot be changed anyway. Also, the reference for the NOAH LSM is missing here. Regarding the CU scheme: I think you mean that for D02 no CU scheme is used.

Regarding the model setup: Did you use the default data sets for soil texture and land cover? This should be mentioned either in Table 3 or in the text.

Line 140: Please add a short sentence about what a perfect KGE would be. I guess 1 is ideal.  What does a KGE of 0.5 tell us (most of the values are below this threshold)? Did you interpolate the simulated precipitation from the WRF model to the IMERG grid? If it was done the other way round, I doubt that this is meaningful. Which interpolation method did you use (bilinear, conservative, nearest neighbor, etc.)? Please also mention the tool or software package used for interpolation.

Line 142: Isn’t γ the ratio of the variances? “Coefficient of variation” sound a bit inappropriate.

Line 145: What was your motivation to use the nearest model grid cell next to the surface observations instead of, e.g., a distance-weighted 3x3 average? I think you cannot expect that the model can simulate your observation 1:1.

Lines 148-161: Please consider to integrate both paragraphs (or parts of them) to the introduction. I think it better fits there rather than in the discussion section.

Line 169-170: you mention that both MYNN schemes and the BouLac scheme rely on the representation of gradients. As you only have coarse 53 model levels, could the explain the detrimental performance of the MYNN and BouLac simulations?

Line 184: What is a “Stratified” BL?

Line 185: This is in contrast to the study of Schwitalla et al. (2020) which you mentioned in Table 1.

Line 201-204: I think this extensive explanation is not necessary here. You may introduce the abbreviations already in Table 3. This allows for saving space.

Line 205: “MP” is used for a microphysics scheme. Please write “cloud microphysics” instead.

Line 217: See my comment to line 201-204.

Line 218: Which advanced microphysical processes?

Line 221: Which sensitivities?

Line 230: I guess you mean “combination” instead of “scheme”.

Lines 231-232: Do the numbers show the absolute value of the mean of “r-1”? This is a bit confusing to the reader. Regarding the KGE: Did you account for a potential “double-penalty” of your model? In case the extreme precipitation is shifted by one grid cell in the model, the KGE may deteriorate.

Figure 3: What do you mean with “long-term bias” in the caption of Figure 3? In the second line of the figure caption, it should be “combination” instead of “scheme”.

Line 247: “(See later Fig. 5)”.

Line 260: You refer to Fig. S4 before Fig. S3 is used. I think the order of the two supplementary figures need to be changed.

Line 279: Which data sets are you referring to? It is unclear.

Line 280: Did you consider the random error provided in the IMERG data set?

Lines 285-292: It may be worth considering to integrate parts of this paragraph to the conclusion section.

Line 295: Can you really conclude this from your study? Precipitation is the end product of a long chain of processes which can have compensating errors. As pointed out earlier, if you mix both 2D and 3D variables here, this can be misleading.

Line 314-315: “WRF model has indicated….”. This sentence sounds a bit awkward.

Line 321: “The WRF model….”

Line 327: Which simplifications? Please elaborate.

Line 337: “the best performing combination in terms of rainfall”.

Figure 6: Showing negative values for accumulated precipitation is not reasonable. Please start with 0 mm or 1 mm.

Lines 340-344: These sentences are confusing. It is not clear to me what you want so say here, especially in relation to the best performing combination.

Figure 7: “… from WRF using the best performing…”

Line 345: The part of the sentence in parentheses can be deleted as this is already explained in line 336.

Line 350: “… for the 17 EREs is 0.20 (not shown)…”. I also would not call the values of “r-1” scores. In my opinion, it is simply a value.

Section 4.9: It this really relevant for your study? My personal feeling is that this is a bit out of scope.

Line 374: What is a “high-performing scheme”?

Section 4.10: Maybe this can be integrated to the conclusion section?

Line 389: Please give an example for arid or semi-arid regions with similar characteristics.

Line 396: Other boundary layer schemes…

Line 402-407: Did you consider investigating cloud properties like integrated cloud water content (e.g., from CMSAF CLAAS: https://doi.org/10.5676/EUM_SAF_CM/CLAAS/V003)? This can give you a hint of what is happening inside the MP schemes with respect to the cloud formation and thus precipitation.

Line 423: “This underlines the complexity…”. Also radiation has an impact on cloud evolution.

Line 425: Only for a particular physics combination.

Line 432: As already mentioned, please reconsider if this part/question is necessary and gives a benefit. This is not a conclusion.

Line 440: “Similar climatic conditions…” like?

Publisher’s note: this comment is a copy of RC3 and its content was therefore removed on 19 May 2025.

Publisher’s note: this comment is a copy of RC3 and its content was therefore removed on 19 May 2025.