Preprints
https://doi.org/10.5194/egusphere-2023-1214
https://doi.org/10.5194/egusphere-2023-1214
13 Jun 2023
 | 13 Jun 2023

Opinion: Tropical cirrus — From micro-scale processes to climate-scale impacts

Blaž Gasparini, Sylvia C. Sullivan, Adam B. Sokol, Bernd Kärcher, Eric Jensen, and Dennis L. Hartmann

Abstract. Tropical cirrus clouds play a critical role in the climate system and are a major source of uncertainty in our understanding of global warming. Tropical cirrus are affected by processes spanning a wide range of spatial and temporal scales, from ice microphysics on cloud scales to mesoscale convective organization and planetary wave dynamics. This complexity makes tropical cirrus clouds notoriously difficult to model and has left many important questions stubbornly unanswered. At the same time, their multi-scale nature makes them well positioned to benefit from the rise of global, high-resolution simulations of Earth's atmosphere and a growing abundance of remotely sensed and in situ observations. Rapid progress requires coordinated efforts to take advantage of these modern computational and observational abilities.

In this Opinion, we review recent progress in cirrus studies, highlight important questions that remain unanswered, and discuss promising paths forward. We find that significant progress has been made in understanding the life cycle of convectively generated ``anvil" cirrus and how their macrophysical properties respond to large-scale controls. On the other hand, much work remains to be done to understand how small-scale anvil processes and the climatological anvil radiative effect may respond to global warming. Thin, in situ-formed cirrus are now known to be closely tied to the thermal structure and humidity of the tropical tropopause layer (TTL), but uncertainty at the microphysical scale remains a significant barrier to understanding how these clouds regulate the TTL moisture and temperature budgets, as well as the mixing ratio of water vapor entering the stratosphere. Model representation of ice-nucleating particles, water vapor supersaturation, and ice depositional growth continue to pose great challenges to cirrus modeling. We believe that major advances in the understanding of tropical cirrus can be made through a combination of cross-tool synthesis and cross-scale studies conducted by cross-disciplinary research teams.

Journal article(s) based on this preprint

18 Dec 2023
| Highlight paper
Opinion: Tropical cirrus – from micro-scale processes to climate-scale impacts
Blaž Gasparini, Sylvia C. Sullivan, Adam B. Sokol, Bernd Kärcher, Eric Jensen, and Dennis L. Hartmann
Atmos. Chem. Phys., 23, 15413–15444, https://doi.org/10.5194/acp-23-15413-2023,https://doi.org/10.5194/acp-23-15413-2023, 2023
Short summary Executive editor

Blaž Gasparini et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1214', Maximilien Bolot, 24 Jul 2023
  • CC1: 'Comment on egusphere-2023-1214', Claudia Stubenrauch, 13 Aug 2023
  • RC2: 'Comment on egusphere-2023-1214', Aurélien Podglajen, 14 Aug 2023
  • AC1: 'Replies to Referee comments', Blaž Gasparini, 16 Oct 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1214', Maximilien Bolot, 24 Jul 2023
  • CC1: 'Comment on egusphere-2023-1214', Claudia Stubenrauch, 13 Aug 2023
  • RC2: 'Comment on egusphere-2023-1214', Aurélien Podglajen, 14 Aug 2023
  • AC1: 'Replies to Referee comments', Blaž Gasparini, 16 Oct 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Blaž Gasparini on behalf of the Authors (16 Oct 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (17 Oct 2023) by Martina Krämer
RR by Aurélien Podglajen (17 Oct 2023)
RR by Maximilien Bolot (02 Nov 2023)
ED: Publish subject to technical corrections (03 Nov 2023) by Martina Krämer
ED: Publish subject to technical corrections (03 Nov 2023) by Timothy Garrett (Executive editor)
AR by Blaž Gasparini on behalf of the Authors (06 Nov 2023)  Author's response   Manuscript 

Journal article(s) based on this preprint

18 Dec 2023
| Highlight paper
Opinion: Tropical cirrus – from micro-scale processes to climate-scale impacts
Blaž Gasparini, Sylvia C. Sullivan, Adam B. Sokol, Bernd Kärcher, Eric Jensen, and Dennis L. Hartmann
Atmos. Chem. Phys., 23, 15413–15444, https://doi.org/10.5194/acp-23-15413-2023,https://doi.org/10.5194/acp-23-15413-2023, 2023
Short summary Executive editor

Blaž Gasparini et al.

Blaž Gasparini et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

This article offers a wide ranging review of current understanding of the role various tropical cirrus cloud types play in the redistribution of water within the atmosphere and how they affect the changing Earth's energy balance by reflecting sunlight and preventing the escape of thermal energy to outer space. Improved understanding of these dynamics has been identified as critical for predicting whether such clouds may amplify or slow future global climate change. A clear exposition is provided of the various methods used to study tropical cirrus cloud characteristics and processes, including remote sensing, in situ measurements, modeling and laboratory work. Key questions include identifying how small-scale microphysical processes affect larger cloud structure, and how cirrus altitude and extent responds to changing radiation and thermodynamic profiles. A call is made not only for improved representations of cloud processes at finer scales, but also for a more holistic approach using a hierarchy of model detail. Such efforts would enable new knowledge obtained from studying even the smallest scales to be more readily placed within a broader context applicable to climate studies.
Short summary
Tropical cirrus clouds are essential for the climate, but our understanding of these clouds is limited due to their dependence on a wide range of small- and large-scale climate processes. In this Opinion, we review recent advances in the study of tropical cirrus clouds, highlight remaining open questions, and discuss what we can do to resolve them.