General Comments

The overall quality of the manuscript is in my opinion very good, and a perfect match for this journal. The writing is concise yet detailed, the displayed graphs are of high quality and informative, and the structure is easy to follow. The topic is highly relevant for the audience of GMD and the authors seem to have a great expertise in it. The proposed model evaluation software is a valuable contribution to the field of atmospheric science, deepening the impact of the incorporated measurement campaigns in the modelling community. This package could become an indispensable tool to improve aerosol-cloud interactions, particle formation and other parametrizations in the E3SM – and potentially other GCM’s as well. Investments in well-documented, open-source model validation software should be encouraged because they allow the community to get the most out of the available observation data.

Specific Comments

• Figure 1 caption: I wouldn’t call this a workflow but a directory structure. I personally think a workflow – boxes representing functions and arrows representing data flows – is more informative to understand the processing steps, so I would recommend to make such a graph, and perhaps move the current directory structure of Fig. 1 to an appendix
• Line 158: Here I believe it is appropriate to actually mention the applied thresholds in the text.
• Line 186: This information to me seems crucial for applicability of ESMAC Diags beyond E3SM, and I would therefore clearly state what the package exactly needs from E3SM, on which resolution and which frequency, maybe even in a small table. Also it would be great to have a remark on the applicability of this software to CMIP6 data. On line 490 we again encounter a short statement about generalization beyond E3SM, and also there I believe the paper would benefit from elaborations on the necessary model output for this.
• Line 312: I see a discrepancy between organic aerosol composition during IOP1 at 300 m height (from Fig. 6) and the surface measurements (Fig. 7); where the simulations agree with the former, the difference with the latter is striking when one looks at Fig. 7. The authors have a similar observation for the ACE-ENA campaign and address this on line 349, could that explanation cover the HI-SCALE case too?
• Figure 10: The clipping of the heat map at (I believe) 700 nm due to the range of the (nano)SMPS is somewhat confusing in a comparison graph: maybe the model graph could be cut off there too? Or just limit both y-axes to that threshold?
• Line 390-407: This is an interesting section showcasing the ability to focus upon single events and assess the representation of aerosol-cloud interactions on shorter time scales. Is this event automatically chosen by the package, or does the user need to select this particular day by hand? Are there other interesting events the authors could mention (possibly involving precipitation)?
• Figure 14+15: It is somewhat confusing to me the authors chose to display the aerosol number concentrations for the ship measurements on a log scale and for the aircraft measurements on a linear scale.
• Line 433+446: This section contains a digression into cloud scheme assessment. I understand from the summary that the authors intend to expand this capability of the package, but I would consider dropping this paragraph or moving it elsewhere because it may distract from the main topic.
• Summary section: The authors present an outlook into future development of the package, including more cloud-related diagnostics and supporting high-resolution versions of the model. Here I would expect a few sentences about which other measurement campaigns the authors wish to include in a future version of ESMAC Diags (or if none: why current observation datasets provide a complete assessment of aerosol processes).

Technical Corrections

• Line 98: SOA and MOA should be spelled out, they are mentioned first here
• Line 154: CPC should be spelled out, it is mentioned first here

This manuscript describes the ESMAC Diags version 1.0 package and provides useful examples of its application. I have only minor concerns and some hopefully useful suggestions below, but otherwise I believe the manuscript is ready for prompt publication. Kudos to the authors for this nice service to the community, and I hope the package gets good use. -MD

General comments:

Addition of future campaigns:

Would it be possible to discuss more about which other campaigns are being considered for inclusion in future versions of the diagnostics package? The southeast Atlantic smoke-cloud campaigns (NASA ORACLES, DOE LASIC, plus CLARIFY and AEROCLO-SA internationally) in particular could be great testbeds for aerosol representation and have good ground- and air-based sampling. ATom could also be really interesting for its global reach.

Treatment of observations as "truth":

At some locations in the text (e.g., "underestimation" in Line 303) the language sounds like the observations are being treated as base "truth." Other locations more thoroughly discuss limitations in the observed data as well. It might be helpful to address the issue of how observations are treated (not truth, but useful baseline given limitations are known) more in the introduction or methods sections.

Specific comments:

Line 164: Specify that size is referring to aerodynamic dry diameter (or whatever it is you are using) for all uses thereafter. I'm assuming diameter but I don't remember seeing it in the text (but it is in some figure labels).

Line 208: Why choose only latitude? Are there any longitudinal variation issues that should be addressed?

Figures 4-5: It might be helpful to also place markers binned for >10 nm and >100 nm for easy comparison to Table 3 and the discussion in the text.

Line 256 (Table 3): Are there any issues worth discussing between the PCASP and UHSAS data, e.g., different size cutoffs and bins?

Lines 297-299: A citation from a relevant HI-SCALE paper would be useful here.

Lines 400-401: I'm not sure this concern is warranted, as above-cloud CCN concentration has only limited relevance to cloud properties because the timescale for entraining above-cloud air into the cloudy boundary layer is on the order of days (Diamond et al., 2018; Mardi et al., 2019). The below-cloud CCN concentrations seems better-represented, and these should be the relevant metric for ACI considerations.

Lines 440-441: Although this reads the "right" way based on the x-axis in Figures 13-14(a), it's backwards from the Lagrangian/cloud perspective. I'd recommend flipping it ("SSTs increase from CA to HI...").  

Lines 452-458: The commentary here is really sparse as compared to the other sections/campaigns. I'm not as familiar with this region, but I know of a few papers from Daniel and Isabel McCoy and colleagues that seem potentially relevant (listed below), and am sure there are many others that could be usefully discussed here.

Line 453: Do we not need to worry about ice water path here as well, given the mixed-phase regime? It seems difficult to interpret LWP-only results here, unless this is being subset for confidently warm or supercooled clouds only?

References:

Diamond, M. S., Dobracki, A., Freitag, S., Small Griswold, J. D., Heikkila, A., Howell, S. G., Kacarab, M. E., Podolske, J. R., Saide, P. E., and Wood, R.: Time-dependent entrainment of smoke presents an observational challenge for assessing aerosol–cloud interactions over the southeast Atlantic Ocean, Atmospheric Chemistry and Physics, 18, 14623-14636, 10.5194/acp-18-14623-2018, 2018.

Mardi, A. H., Dadashazar, H., MacDonald, A. B., Braun, R. A., Crosbie, E., Coggon, M. M., Aghdam, M. A., Woods, R. K., Jonsson, H. H., Flagan, R. C., Seinfeld, J. H., and Sorooshian, A.: Effects of Biomass Burning on Stratocumulus Droplet Characteristics, Drizzle Rate, and Composition, Journal of Geophysical Research: Atmospheres, 124, 12301– 12318, 10.1029/2018jd029134, 2019.

McCoy, D. T., Burrows, S. M., Wood, R., Grosvenor, D. P., Elliott, S. M., Ma, P.-L., Rasch, P. J., and Hartmann, D. L.: Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo, Science Advances, 1, e1500157, 10.1126/sciadv.1500157, 2015.

McCoy, I. L., McCoy, D. T., Wood, R., Regayre, L., Watson-Parris, D., Grosvenor, D. P., Mulcahy, J. P., Hu, Y., Bender, F. A. M., Field, P. R., Carslaw, K. S., and Gordon, H.: The hemispheric contrast in cloud microphysical properties constrains aerosol forcing, Proceedings of the National Academy of Sciences of the United States of America, 117, 18998-19006, 10.1073/pnas.1922502117, 2020.

McCoy, I. L., Bretherton, C. S., Wood, R., Twohy, C. H., Gettelman, A., Bardeen, C. G., and Toohey, D. W.: Influences of Recent Particle Formation on Southern Ocean Aerosol Variability and Low Cloud Properties, Journal of Geophysical Research: Atmospheres, 126, 10.1029/2020jd033529, 2021.