Review of egusphere-2024-1689-version3.pdf
I think this is a significantly improved manuscript. It's very close to publication quality. I think this manuscript deserves to be highlighted, and I thus I reviewed it below as a highlights candidate. In my opinion, it requires a bit of editing to make it highlights worthy, which I hope the authors agree with. I list my comments below for potential improvements, and I hope the authors find them constructive. All my comments below should be considered minor (unless the authors deem them otherwise) and they should be considered non-blocking for publication.
Minor comments:
- The manuscript is still hard to read; if the authors can spare some time improving readability and presentation, that will go a long way. In general, it's improved significantly, and it is publishable as-is, but it could be improved and should ideally be highlighted (because it is a pretty good study)
- There several minor/technical issues that may warrant minor fixes (I list all of these below). I encourage the authors to fix them
- I think the authors downplay the usefulness of their idealized setup, MACv2-SP. I think it would be nice if the authors make it clear where they see advantages in simplified schemes beyond computational performance (e.g., causality, process isolation) and where they see shortcomings (e.g., non-interactive nature of aerosols and lack of mesoscale features shown in ICON-HAM-Lite). The authors do plenty of the latter (shortcomings) but not enough of the former (advantages). After all, you're using a simplified scheme and if the only reason you're doing this study is because you had to, then that's no good. I think there's value in these simplified schemes in that they allow us easier access to some process aspects that are significantly harder to disentangle with fully interactive schemes. If you disagree with me, feel free to ignore. I just feel it is a missed opportunity not to forcefully defend these simplified schemes as practical and appropriate for some endeavors (you could also make your argument by carefully citing Stevens et al and Fiedler et al papers where they described the original MACv2-SP scheme)
- Finally, I think the discussion around convection could be improved, but I will admit (like I do below) that this is not my area of expertise, so I cannot judge the claims sufficiently. After reading these parts a few times, I felt the arguments were wishy washy and not very convincing when it comes to convection. They strongly imply significant convection changes at times, but other times the authors caution over-interpretation. I would encourage a careful reread of those parts dealing with convection, then assessing if more careful phrasing and revision could be used. I also suggested referring (and/or reminding) the readers to a convection assessment of ICON (if at all). Would any conclusions about aerosol–convection interactions be affected if the convection itself isn't as good/robust?
More comments:
L9: It’s not readily clear to me how this sentence implies anything about atmospheric dynamics — even with controlled dynamics (say nudged simulations), we will see strong regional dependence, no? I’d recommend removing it from the abstract unless you can justify it later? I didn’t really see enough strong evidence supporting it. I would remove the part about atmospheric dynamics especially that the next point is by far the least controversial and most important point of this manuscript. Note my point here isn’t debating if the statement is true in general (I think it is true; e.g., I agree with your framing near L275), but rather, your manuscript/results don’t have enough evidence to support “complex interplay with atmospheric dynamics” highlight imo
L10: Imho, this is the most important point of this manuscript. I think this alone justifies the manuscript and effort. It is also highlighted in the title. Great work!
L13: This may benefit from a slight clarification to drive the point home stronger. I think you’re trying to say something like “Because we observe pronounced diurnal cycles … we think polar-orbiting satellites may be even more limited than we already know.” If so, I would rephrase to something like “, suggesting the usefulness of using polar-orbiting satellites to quantify ACI may be even more limited than presently assumed”
L17: I found the statement about ACI/ARI in the Conclusion section (e.g., L485) to be quite important and remarkable and I thus recommend including more about it in the abstract (maybe as a follow-up sentence to the great sentence on L10?)
L86: Usually, models prescribe the sea ice extent, but let the sea-ice thermodynamics run. If that’s the case in your model, I would simply add “extent” or “cover” after sea ice to avoid confusion
L117: I would mention the exact process (which you do later anyway, but might as well do it here too: autoconversion)
L118: I thought they are non-interactive but spatially and temporally varying? Like AOD is different over Africa compared to Poles. Same for Nc and/or Nd. Are you talking about something else here? When I read “fields … provided by MACv2-SP” I think of fields that MACv2-SP prescribes for your simulations (optical depths + Nd + Nc). Maybe you’re talking about the inputs to the plume model or something else here…
L164: Minor point: is it more or less consistent with obs than the prior tuning?
L172: Minor: I would consider using the table to specify the details very clearly and anchor the discussion around it. For example, PI run uses Nd,cld that’s constant (value xyz), but Nd,rad that evolves according to Eq X with constant values for xx and yy. Currently, you do have all the info in the text, it is just slightly hard to parse. But feel free to ignore…
L200–215: Great! I think this is very promising and appropriate!!
L301 (and many other places): You use the word “response” a lot in this manuscript (on one editor, I found 117 instances when I used the pdf search functionality) and you use it to mean at least two different things. On this line, you likely mean just the values of the CFtotal in Figure 8. But elsewhere you use it to mean the PD-PI response (other places you also use in the second sense, related to change). Can you try to clarify this throughout the manuscript? For example, in Figure 7 (just above) you likely just mean “… during diurnal cycle of maximum absolute for each...” And on this line you like just mean “spatially consistent with CFtotal, with” … unless I missed something obvious?! I bring this up because the word response tripped me up multiple times, and I got confused trying to understand what you’re trying to say. I found myself having to go back and cross-check. My recommendation is to use the word “response” only in making an explicit point about “a response to a perturbation” (e.g., your L308, or caption of Figure 10). For everything else, I’d use different ways to describe the signal more matter-of-factly/plainly
L319: Minor, but has there been an assessment of deep convection characteristics in this model? Is it okay compared to obs? I am not a convection expert and I don’t study convection–aerosol interactions, but I keep hearing that 5km models have pretty severe convection problems, so I am not sure how informative it is to study the aerosol impacts on or due to convection, if the convection is poorly simulated to begin with. This is borderline outside your scope here, so my only minor request is to add (somewhere in the manuscript, if not added already) some references about a convection assessment of this specific model config if one exists…
L375 (and thereabouts): I don’t think these variables (Mflux, W*) were defined/introduced, but I may have missed them… I would introduce them with equations or a reference to an equation/methodology elsewhere
L397: which state? Here and elsewhere, I would try to be explicit about which state you mean (dynamic state, thermodynamic state, aerosol state, cloud state, or general atmospheric state, or something totally different?)
L415: Related to the above: you start with localized modification to the convective environment, but here you say convection itself is modified. How did the jump take place? Is the reader supposed to assume that the localized modifications to the convective environment will always lead to convection changes?
L410: Like above, here and elsewhere, I would try to be explicit about what you mean by convective environment. Of course, you can define it the first time you mention it and say “convective environment” is my shorthand for what I just defined throughout the manuscript.
L498: I think I finally get what you’re saying with the “spatially invariable” part… the spatially invariable aerosol as input to MACv2-SP? But this is quite misleading! Your model doesn’t really care about that aerosol input to the MACv2-SP model; what your model cares about is the effect of the aerosol (as proxied by radiation properties like optical depths, Nd,cld, and Nd,rad). These are definitely spatially variable! Am I misunderstanding something here?
L502: I would delete this last sentence advertising modeling groups (doesn’t really add any context beyond what you said)
L520: I would remove this entire paragraph (ending on the prior paragraph is much better imho).
L527: Could you provide a specific commit/sha for the code you used? Or even better include it in a permanent Zenodo repository with its own DOI? Thanks! |
This study investigates the impacts of anthropogenic aerosols on radiation and cloud properties using a global convection-permitting model. Four 40-day simulations are conducted to isolate the aerosol impacts via the aerosol-cloud interaction and the aerosol-radiation interaction. The methodology and analysis are straightforward. However, several severe flaws in the manuscript prevent its publication in its current form.
Major comments:
Minor comments:
Line 7: Please provide the full name of “ICON” for its first appearance.
Line 39: What do you mean by lack of memory?
Line 43: “Limited area” to “Regional”?
Line 44-45: What do you mean by large-scale controls on the availability of energy and water vapor?
Line 62: What is the resolution of NICAM?
Line 66: “or” to “nor”?
Lines 74 and 75: The full names of ICON and MACv2-SP?
Line 112: add “separately” after “cloud water.”
Line 115: What is SLEVE?
Lines 140-141: Any references for such an adjustment?
Line 152: Figure 1 shows an overestimation of Nd. Do you have any statistical calculations validating the changes of aN and bN?
Section 2.2: The description of aerosols in ICON needs more detailed clarification. Which type of aerosol variables does ICON need? How do you consider pre-industrial and present-day aerosol conditions? The current description is confusing. Did you only add fN in the model? Where are Nd,cld and Nd,sfc from? Does ICON contain any aerosol microphysical processes (processes converting emissions to aerosol concentrations), or are aerosols entirely prescribed in the model (input aerosol concentrations, AOD, etc.)?
Lines 172-178: I am confused with what MACv2-SP provided to ICON. Anthropogenic aerosol concentrations?
Lines 179-180: Please rewrite this sentence.
Lines 179-185: Both PI and PD simulations contain biomass-burning sources. What are their differences? In Line 132, you mentioned that in MACv2-SP, biomass-burning emissions are anthropogenic sources. Could you please provide more details about that?
Lines 212-213: Can internal variability be eliminated by only focusing on regional responses?
Line 229-230: How did you know it is due to internal variability but not actual model differences? Internal variability refers to variability due to natural internal processes within the climate system. But here, you talked about the differences between the two simulations.
Line 234: Again, how did you know it is due to internal variability?
Line 235: add “outgoing” before “shortwave radiation.”
Line 253: “internal variability” to “spatial heterogeneity.” Please check the whole manuscript to ensure the correct terms are used.
Lines 269-271: Would applying the tool to Section 3 (original model data but not differences) be better also to remove your so-called “internal variability”?
Lines 279-283: There is an assumption here: the long-term component is constant and independent of time. Is it correct? At least Figure 7f doesn’t show that!
Line 286: Delete “with the SE Atlantic region”.
Line 305: Do you have an explanation for the nighttime enhancement?
Line 319: Does ACI increase cloud cover? Did you refer to Figure 4h?
Line 345: Please provide more details about how you constrain ascending air masses. Using hourly or daily data?
Line 349: Why not decompose them given that you did it in Section 4.1?
Line 357: Does the profile of potential temperature changes align with the anthropogenic aerosol loading profile? Do you have any model output showing the suppression of boundary layer mixing and drying aloft? How do you define the boundary layer? 1 km? 2 km?
Line 360-362: Did you mean the daily mean or afternoon mean? If you meant afternoon mean, Figures 11a and 11d showed that Amazon has weaker w effects than Congo. If you meant daily mean, Figure 8 shows the ARI effect is the most significant in the afternoon. Please provide more reasonable descriptions and explanations for the results.
Line 367: How does the delayed release of CAPE increase high-altitude IWC?
Line 367-370: How did you know convection occurred certainly given increased CAPE aloft? More evidence is necessary to support such types of conclusions.
Lines 380-381: Which variables did you refer to?
Lines 381-383: Please provide more details about the reasoning.
Line 391: What do you mean by delayed CAPE? In addition, how can they explain the non-linear response?
Line 400: Is 1 mm day-1 consistent with Figure 9?
Line 415: Do you mean the red line? It is over zero at all hours.
Lines 416-417: ARI is positive in Figure 9h.
Lines 417-418: The ACI effect on LWP is always positive, while its effect on Mflux is negative only between 12:00 and 15:00 LST. How can you explain it?
Lines 422-428: Please provide more detailed reasoning!
Line 440-441: ACI and ARI are comparable in the ice-phase region!