Comments on “Evaluating three decades of precipitation in the upper Colorado River basin from a high-resolution regional climate model”, by Rudisill et al., submitted to Geoscientific Model Development, for possible publication.

Accurate precipitation estimate over complex terrains remains a challenge and hot research topic in hydrology communities. The present study demonstrates the utility of high-resolution regional climate model simulations in leveraging both spatial and temporal precipitation variability over the Upper Colorado River basin. They carry out multi-scale evaluation of simulated precipitation fields against in-situ observations and various gridded products (reanalysis, reconstructed). Their results could provide important implications for future precipitation validation studies in complex terrains, and offer a good dataset for hydrology studies in this particular region. The manuscript is comprehensive and overall well-written.

A major concern of mine is since the simulations are implemented in hourly scale, I would suggest comparisons at hourly scale should be carried out as well. The authors emphasize the utility of the hourly rainfall products, but nowhere in the text that we can see how the model is compared against in-situ observations, for instance, does the model capture the daily rainfall cycle well? How about the spectrum of hourly rainfall intensity, etc.? This is missing from the manuscript, but is needed for potential users.

A minor concern of mine is how are the physics options determined, do the authors test other combinations? We know rainfall simulation is particularly sensitive to a couple of parameterization schemes, e.g., microphysics schemes, planetary boundary layer scheme.

The presentation of the manuscript should be improved. The current version seems lengthy. Some paragraphs could not be repeated, for instance, lines 60-80, and also some details in section 2.3 and 4.3 can be presented only once. I also spotted some typos or incomplete sentence, but would suggest the authors to check throughout the manuscript. For instance, line 6, line 31, line 393, line 439.

The subject is relevant and the manuscript has been written well. I think that the paper can be considered for publication after a minor revision.

COMMENTS

- Fig.10 is not clear. Most acronyms have not been explained in the caption or on the graph. Each figure must be understandable individually. Also, add explanations for the plotted lines. Are each color for each year? If yes, explain it in the caption.

- Fig.12: The streamflow values are presented in mm/day which is not a commonly used unit for water flow. I suggest to use any “volume/time” unit instead of “length/time”. Also, on the right plot, “-1” in “RMSD: 0.524…” has to be moved into the parenthesis.

- It is suggested that in the discussion section, add even few explanations about global gridded precipitation data and refer to relevant papers (e.g., in this paper 15 global gridded precipitation data have been investigated, 10.1016/j.agwat.2021.107222). These global gridded precipitation data can be applied for carrying out similar studies outside of the US.