Preprints
https://doi.org/10.5194/egusphere-2025-1816
https://doi.org/10.5194/egusphere-2025-1816
06 Jun 2025
 | 06 Jun 2025

Microphysical Parameter Choices Modulate Ice Content and Relative Humidity in the Outflow of a Warm Conveyor Belt

Cornelis Schwenk, Annette Miltenberger, and Annika Oertel

Abstract. Warm conveyor belts (WCBs) play a crucial role in Earth's climate by transporting water vapor and hydrometeors into the upper troposphere/lower stratosphere (UTLS), where they influence radiative forcing. However, a major source of uncertainty in numerical weather prediction (NWP) models and climate projections stems from the parameterization of microphysical processes and their impact on cloud radiative properties as well as the vertical re-distribution of water. In this study, we use Lagrangian data from a perturbed parameter ensemble (PPE) of a WCB case study to investigate how variations in microphysical parameterizations influence water transport into the UTLS and the outflow cirrus properties. We find that the thermodynamic conditions (pressure, temperature, specific humidity) at the end of the WCB ascent show little sensitivity to the explored parameter perturbations. In contrast, ice content and relative humidity exhibit substantial variability, primarily driven by the capacitance of ice (CAP) and the scaling of ice formation processes directly influenced by ice-nucleating particle (INP) concentrations. Different combinations of CAP and INP scaling yield vastly different ice and relative humidity distributions at the end of the ascent and in the subsequent hours. These differences are particularly pronounced in fast-ascending air parcels, where modifications to the saturation adjustment scheme (SAT) introduce small variations in pressure and temperature at the end of ascent. Our findings have potential implications for parameter choices in cloud models and considerations for geoengineering strategies. Future comparisons with high-quality observational data could help constrain the most realistic parameter choices, ultimately improving weather and climate forecasts.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
Share

Journal article(s) based on this preprint

26 Sep 2025
Microphysical parameter choices modulate ice content and relative humidity in the outflow of a warm conveyor belt
Cornelis Schwenk, Annette Miltenberger, and Annika Oertel
Atmos. Chem. Phys., 25, 11333–11361, https://doi.org/10.5194/acp-25-11333-2025,https://doi.org/10.5194/acp-25-11333-2025, 2025
Short summary
Cornelis Schwenk, Annette Miltenberger, and Annika Oertel

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1816', Anonymous Referee #1, 18 Jun 2025
  • RC2: 'Comment on egusphere-2025-1816', Anonymous Referee #2, 30 Jun 2025
  • RC3: 'Comment on egusphere-2025-1816', Anonymous Referee #3, 03 Jul 2025
  • RC4: 'Comment on egusphere-2025-1816', Anonymous Referee #4, 03 Jul 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1816', Anonymous Referee #1, 18 Jun 2025
  • RC2: 'Comment on egusphere-2025-1816', Anonymous Referee #2, 30 Jun 2025
  • RC3: 'Comment on egusphere-2025-1816', Anonymous Referee #3, 03 Jul 2025
  • RC4: 'Comment on egusphere-2025-1816', Anonymous Referee #4, 03 Jul 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Cornelis Schwenk on behalf of the Authors (28 Jul 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (28 Jul 2025) by Ann Fridlind
RR by Anonymous Referee #2 (02 Aug 2025)
RR by Anonymous Referee #1 (06 Aug 2025)
ED: Publish as is (07 Aug 2025) by Ann Fridlind
AR by Cornelis Schwenk on behalf of the Authors (11 Aug 2025)  Manuscript 

Journal article(s) based on this preprint

26 Sep 2025
Microphysical parameter choices modulate ice content and relative humidity in the outflow of a warm conveyor belt
Cornelis Schwenk, Annette Miltenberger, and Annika Oertel
Atmos. Chem. Phys., 25, 11333–11361, https://doi.org/10.5194/acp-25-11333-2025,https://doi.org/10.5194/acp-25-11333-2025, 2025
Short summary
Cornelis Schwenk, Annette Miltenberger, and Annika Oertel

Data sets

Trajectory data Annika Oertel https://www.doi.org/10.35097/ecgs4f56mp3ymjmt

Cornelis Schwenk, Annette Miltenberger, and Annika Oertel

Viewed

Total article views: 903 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
789 87 27 903 36 11 31
  • HTML: 789
  • PDF: 87
  • XML: 27
  • Total: 903
  • Supplement: 36
  • BibTeX: 11
  • EndNote: 31
Views and downloads (calculated since 06 Jun 2025)
Cumulative views and downloads (calculated since 06 Jun 2025)

Viewed (geographical distribution)

Total article views: 901 (including HTML, PDF, and XML) Thereof 901 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Latest update: 29 Sep 2025
Download

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

Short summary
We studied how different parameter choices concerning cloud processes affect the simulated transport of water and ice into the upper atmosphere (which affects the greenhouse effect) during a weather system called a warm conveyor belt. Using a set of model experiments, we found that some parameters have a strong effect on humidity and ice, especially during fast ascents. These findings could help improve weather and climate models and may also be relevant for future climate engineering studies.
Share