The authors use an LES coupled to a Lagrangian particle model to investigate the optimal sprayer placement for the dispersion and eventual activation of sea salt aerosol for marine cloud brightening in trade cumulus regions. They find that near-surface sprayers are most effective because they take advantage of the greater turbulence lower in the boundary layer and activate as cloud droplets at cloud base/are spread within cloudy updrafts efficiently. Cloud-layer spraying leads to lateral aerosol entrainment, which is inefficient for activation. Only the deepest clouds reach the aerosol plume and entrain the injected salt, leading to a non-physical relationship between cloud water and aerosol in the higher altitude cases. Even with this bias in the rCRE calculations, the surface sprayer is by far the most effective at brightening the scene. The analysis is well-done and presented appropriately. The writing is sharp and concise. I recommend publication following minor revisions addressing the comments below. -Michael Diamond

1. Line 6: Near-surface?
2. Line 4: Is the vertical domain really 20,480 m? Seems like it’s a bit over 3,500 m?
3. Figure 2: What is the time of the snapshot?
4. Line 92: Relative CRE?
5. Figure 3: How is cloud fraction defined here?
6. Figure 3: Why is rCRE not shown? You spend a lot of time talking about how to calculate it and show all its components, but it’s somehow missing itself…
7. Figure 3: Can ensemble spread be indicated?
8. Line 127: 3h instead of g?
9. Line 180: It seems odd to talk about the GBR campaign being “proposed” by the 2024 review… Is there a more classic citation possible here? E.g., the 2019 “Reef Restoration and Adaptation Program: Environmental Modelling of Large Scale Solar Radiation Management. A Report provided to the Australian Government by the Reef Restoration and Adaptation Program” document. McDonald et al. (2019) or Condie et al. (2021) could also be appropriate.
   
   
   
   McDonald, J., McGee, J., Brent, K., & Burns, W. (2019). Governing geoengineering research for the Great Barrier Reef. Climate Policy, 19(7), 801-811. https://doi.org/10.1080/14693062.2019.1592742
   
   
   
   Condie, S. A., Anthony, K. R. N., Babcock, R. C., Baird, M. E., Beeden, R., Fletcher, C. S., Gorton, R., Harrison, D., Hobday, A. J., Plaganyi, E. E., & Westcott, D. A. (2021). Large-scale interventions may delay decline of the Great Barrier Reef. R Soc Open Sci, 8(4), 201296. https://doi.org/10.1098/rsos.201296
   
   
   
   
10. Lines 205-210: Changing to talking about some example W m-2 values could be helpful here. It’s hard to get an intuitive feel for what is or isn’t an important difference in rCRE.