Re-adding science page for percusion

[mckimb]

This pull request is my response to the issue I raised here: #364

This is what I did

• Brought back the science page
• Added a post on the scientific motivation for percusion

I am interested in your feedback on what I wrote @hgloeckner @JuliaWindmiller1987. I would like to know if you think the following questions are worth answering in the post, or if they might distract from the main message.

• Should I go into more detail about the energetic constraints? (i.e. Kang et al, 2008; Schneider et al, 2014; Byrne and Schneider, 2016)
• Why does moist static energy $m(z)$ have a c-shape? Is it really okay to assume that $m$ is constant in the horizontal?
• Should I include some example sonde profiles of $w(z)$? And should I provide a brief analysis of what they tell us? Or perhaps that should be its own page (at some point in the future)?
• Why is $m$ conserved during convection?

[lkluft]

Thanks for (re)adding this! I just fixed a small error in an image path, otherwise the PR seems to be fine from a technical point of view.

Not sure if we want an in-depth scientific review or if we are just happy that science is back and the "S" in ORCESTRA no longer stands for Sal 😉

[JuliaWindmiller1987]

I am looking at it now, so please don't merge yet :)

[JuliaWindmiller1987]

I have only managed to glance take a first glance so far but from what I have seen so far: fantastic job, Brett, thanks a lot for this nice summary! I am happy to provide some more detailed feedback tomorrow. One thing I noted so far is that it might be nice to mention in a bit more detail why we are looking at the ITCZ in CWV space to explain the motivation behind the flight pattern. There are a number of aspects to this, I am trying to list a few but maybe we can also chat about it as I really enjoyed our last discussion :).

• we want to fly a statistical flight pattern so we can combine our flights from different days in a meaningful way
• as we are interested in the edges vs. the center of the ITCZ, an obvious question to ask is how to identify the edges of the ITCZ; during PERCUSION we follow the idea of the moist margin (Mapes et al., 2018) which also allows direct comparison with Masunaga (2023) as they define the ITCZ edges as 50 mm CWV contour
• Mapes et al. (2018) show that the CWV distribution in the tropics is bimodal with a local minimum at 48 mm, with the convective region separated from the non-convective region by a steep gradient in CWV (a persistent steep gradient at 48 mm would explain the few CWV values close to 48 mm and thus the local minimum); this raises the question of what causes these steep gradients that separate the deep convecting tropics from the dry subsiding tropics --- this is another reason why we place the circles at this margin since we want to understand what sharpens and smoothens this gradient by analysing the cross margin gradients
• the bimodality also nicely links to self-aggregation and this is also where the original idea of looking at circulations in moisture space (placing circles at edges) originated (see Fig. 10 in Bretherton et al., 2005); self-aggregation also leads to a bimodality in CWV and the interesting question is whether or not the processes leading to a bimodal distribution in SA are connect to the bimodality in the tropics and which of the processes are most important (see Allison's review paper)
• I could go on but have to go for dinner :) happy to chat more though

[hgloeckner]

Thank you so much for the summary Brett :) I feel like you explained it such that even I after three days on the plane can get the idea (maybe not all details, but that's expected).

I wouldn't include example profiles. That can be done later and separate. It's kind of nice that it's a relatively short and easy to understand explanation. Making it longer does not necessarily help in my opinion. I'll try to read it again tomorrow to answer your first question and I think Julia can probably help better with the others :)

@JuliaWindmiller1987 I am not sure if I would add the explanation for the exact placement of the circles there since Brett is giving a broader overview. Maybe that's more for another, more detailed subpage? Like Brett is explaining the 'why' (and maybe generally how) and your points would go a bit more into detail about the 'how'. But that's just my first impression^^.. maybe tomorrow that has changed...

[JuliaWindmiller1987]

@hgloeckner Agreed, I did not mean for Brett to go into any detail on the circles (they don't even have to be mentioned) but it might be great to add a bit on the topic of the moist margin (Mapes et al.) and self-aggregation (Wing et al., 2017) because it plays such a crucial role for our measurement strategy and is linked very much to the why. The big question being: what couples convection to the column water vapour field or, since the causality is unclear, the column water vapour field to the convection and, since the convection lives in the moist region, what sets its width and moves its boundaries? What role do the processes that sharpen the gradients between dry and moist regions in idealised simulations play in reality? If they play a role this might have a significant impact on the future of the ITCZ since these processes have been shown to be temperature dependent (albeit in a complicated way). For example, some of these processes are suspected to become stronger with global warming. This would make dry regions drier and moist regions moister. Since the radiative effect of the dry regions dominates the overall OLR budget this might be a significant negative feedback on climate change. This is one of the reasons we are so interested in the margins.

[bjorn-stevens]

@JuliaWindmiller1987 as I mentioned today, I always interpreted your nice idea of using the PW contour as a way to avoid the perils of using latitude and thereby sampling the trades too much, i.e.,it helped us define a region that was more dynamic than simply picking latitudes. There are good reasons to use PW, but we could, and do, use winds, rain and clouds to inform the sampling. I think we wouldn't really only want to sample PW = 48 and PW >> 48 if we want to look statistically at the influence of water vapor. Now again 50-55 might also be interesting. I don't think I am saying anything controversial, but I do get the idea that in emphasizing a particular contour too much we are leading people astray as they think this is somehow magical (it isn't, i.e., PW has no\ meaning separate from temperature) .. and today we had an example where people following this strategy with too much fealty would have us follow hurricanes to new york :) ...

[bjorn-stevens]

On a broader point, one could be forgiven for getting the impression from this page that PERCUSION has nothing to do with its P, E, R, C and U. Would there be a way to structure the material to bring out the breadth of what we are doing better, so that more people can find themselves in the campaign.

In the Grand Challenge we posed the Question of what controls the position, strength and variability of the tropical rain belts which led to trying to understand the interplay between tropical oceans and organized convection, for instance as influenced by air-sea interaction and atmospheric radiative heating (TOOC), and I think this is still something we can hope to do. Later we became more interested in the dynamical evolution of vorticity and divergence. The budget of moist static energy plays a role in all of this, and it might be the only thing that matters, but I suspect not, and its analysis presents the challenge inherent in all budgets.

So I like this page very much, but I think we would all be enriched if the intellectual landscape we are painting had a bit more of this guy

and a bit less of this guy

reflected in it.

[mckimb]

Thank you for all of your comments. I've tried to broaden the scope by adding paragraphs on column water vapor, moist margins and self aggregation; EarthCare, statistical sampling and relating process observations to climate change; and different ways of understanding the ITCZ (air-sea interactions, conservation of momentum/evolution of vorticity and divergence, etc.). My impression is that the edit has brought the page from SION to percuSION. Let me know if this edit hits the mark or if some changes are necessary. Iit might need some editing for conceptual coherence.

If there is the energy and appetite for it, I think some of these paragraphs could be expanded on in separate posts. (For instance, Divya and Marius could write about conservation of momentum/evolution of vorticity and divergence and the ITCZ; Jakob and I could write about cloud radiative effects; Silke/Florian could write about EarthCare validation, etc...)

By the way, who is the second person pictured?

[lkluft]

Thanks for moving this to the PERCUSION page, Yuting! Is there anything else holding this up?

[yu71ng]

Thanks for moving this to the PERCUSION page, Yuting! Is there anything else holding this up?

Not in my opinion. Let's merge!