Articles | Volume 25, issue 18
https://doi.org/10.5194/acp-25-10869-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.Opinion: Inferring process from snapshots of cloud systems
Download
- Final revised paper (published on 22 Sep 2025)
- Preprint (discussion started on 13 May 2025)
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
| : Report abuse
-
RC1: 'Comment on egusphere-2025-1869', Anonymous Referee #1, 23 Jun 2025
- AC2: 'Reply on RC1', Graham Feingold, 05 Aug 2025
-
CC1: 'Comment on egusphere-2025-1869', Jesse Loveridge, 01 Jul 2025
- AC3: 'Reply on CC1', Graham Feingold, 05 Aug 2025
-
RC2: 'Comment on egusphere-2025-1869', Anonymous Referee #2, 03 Jul 2025
- AC1: 'Reply on RC2', Graham Feingold, 05 Aug 2025
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Graham Feingold on behalf of the Authors (05 Aug 2025)
Author's response
Author's tracked changes
Manuscript
ED: Publish as is (05 Aug 2025) by Johannes Quaas

ED: Publish as is (07 Aug 2025) by Ken Carslaw (Executive editor)

AR by Graham Feingold on behalf of the Authors (07 Aug 2025)
This manuscript delivers an elegant and much-needed synthesis of how and when snapshot observations of clouds can justifiably be interpreted as proxies for time-resolved processes. Its intellectual clarity and breadth of examples promise to influence both observationalists and modelers.
Inferring process from snapshots of cloud systems is a thought-provoking synthesis: it distils scattered intuitions about when spatial statistics can stand in for temporal evolution, and it offers a clear vocabulary (ergodicity, D-number, Type 1 vs. Type 2) that would help future cloud research.
In my opinion, apart from a few minor modifications, the paper should be published. It is an “opinion” paper, and as such, it highlights an important question that is highly relevant to cloud/rain/aerosol/climate research in a rather qualitative manner.
Minor comments:
1) In general, I miss a consideration of the variance of the explored processes. In all of the examples, the mapping is not one-to-one. The relevant variables are represented by a distribution (r_e or LWP). When sampling the state space, one must be sure that the variability is covered.
The variance is not necessarily a reflection of the many states. It could reflect variations around a given state. The text in Line 141, for example. The step of translating the satellite snapshot into a few hours of observation is critical. It distills the essence of the paper and should be better explained. We know that the r_e slices (per T, Z, or P) can be highly variable. I miss a discussion of the need for fully covering the statistical variance.
2) On the same note, what is a sufficiently large snapshot? How to scale the spatial length of it to the time it covers? What is the right mapping constant? Is it advection?
3) Line 237: “Because the data derive from many different conditions, the observation timescale t_obs is on the order of many days …” Please explain why, when mixing many observations of different thermodynamical states, we can scale the observation time to days? I guess that by doing so, we average over many thermodynamic scenarios? Again, in this case, the variance of the timescale is important. What is the meaning of ergodicity in the case of averaging many states? I think that discussing it in the introduction would be beneficial to the general message of the paper. Can any system be averaged such that taking enough samples to cover the state distribution will yield an ergodic system?