Preprints
https://doi.org/10.5194/egusphere-2024-3805
https://doi.org/10.5194/egusphere-2024-3805
20 Dec 2024
 | 20 Dec 2024

Simulated mixing in the UTLS by small-scale turbulence using multi-scale chemistry-climate model MECO(n)

Chun Hang Chau, Peter Hoor, and Holger Tost

Abstract. The chemical composition of the upper troposphere/lower stratosphere (UTLS) plays an important role for the climate by affecting the radiation budget. Small-scale diabatic mixing like turbulence has a significant impact on the distribution of tracers which further affect the energy budget via their radiative impact. Current models usually have a higher resolution near the surface and a coarser grid spacing in the free atmosphere, which is insufficent to resolve the occurrence of small-scale turbulence in the UTLS. In this work, we utilise enhanced vertical resolution (200 m in the UTLS) simulations focusing on mixing events in the Scandinavian region using the state-of-the-art multi-scale atmospheric chemistry model system MECO(n). These model simulations are able to represent different distinct turbulent mixing events in the UTLS and depict a significant impact of mixing on the tracer distribution in the UTLS. A novel diagnostic (delta tracer-tracer correlation) is introduced to determine the direction of the vertical mixing. The strength of the UTLS turbulent mixing depends on the particular situation, i.e., the vertical tracer gradient, and dynamical and thermodynamical forcing, i.e., vertical wind shear, deformation and static stability. This work provides evidence that high resolution simulations are able to represent significant turbulent mixing in the UTLS region, allowing for further research on the UTLS turbulent mixing and its implications for the climate system.

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Journal article(s) based on this preprint

21 Oct 2025
Simulated mixing in the UTLS by small-scale turbulence using multi-scale chemistry-climate model MECO(n)
Chun Hang Chau, Peter Hoor, and Holger Tost
Atmos. Chem. Phys., 25, 13123–13140, https://doi.org/10.5194/acp-25-13123-2025,https://doi.org/10.5194/acp-25-13123-2025, 2025
Short summary
Chun Hang Chau, Peter Hoor, and Holger Tost

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3805', Anonymous Referee #1, 23 Jan 2025
  • RC2: 'Comment on egusphere-2024-3805', Anonymous Referee #2, 24 Jan 2025
  • RC3: 'Comment on egusphere-2024-3805', Anonymous Referee #3, 04 Feb 2025
  • AC1: 'Reply to RC1,RC2 and RC3 comments on egusphere-2024-3805', Chun Hang Chau, 17 Apr 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3805', Anonymous Referee #1, 23 Jan 2025
  • RC2: 'Comment on egusphere-2024-3805', Anonymous Referee #2, 24 Jan 2025
  • RC3: 'Comment on egusphere-2024-3805', Anonymous Referee #3, 04 Feb 2025
  • AC1: 'Reply to RC1,RC2 and RC3 comments on egusphere-2024-3805', Chun Hang Chau, 17 Apr 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Chun Hang Chau on behalf of the Authors (18 Apr 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (24 Apr 2025) by Petr Šácha
RR by Anonymous Referee #2 (21 May 2025)
RR by Anonymous Referee #3 (23 May 2025)
ED: Reconsider after major revisions (23 May 2025) by Petr Šácha
AR by Chun Hang Chau on behalf of the Authors (29 May 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (02 Jun 2025) by Petr Šácha
RR by Anonymous Referee #3 (26 Jun 2025)
ED: Reconsider after major revisions (01 Jul 2025) by Petr Šácha
AR by Chun Hang Chau on behalf of the Authors (30 Aug 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (01 Sep 2025) by Petr Šácha
AR by Chun Hang Chau on behalf of the Authors (02 Sep 2025)  Manuscript 

Journal article(s) based on this preprint

21 Oct 2025
Simulated mixing in the UTLS by small-scale turbulence using multi-scale chemistry-climate model MECO(n)
Chun Hang Chau, Peter Hoor, and Holger Tost
Atmos. Chem. Phys., 25, 13123–13140, https://doi.org/10.5194/acp-25-13123-2025,https://doi.org/10.5194/acp-25-13123-2025, 2025
Short summary
Chun Hang Chau, Peter Hoor, and Holger Tost
Chun Hang Chau, Peter Hoor, and Holger Tost

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Short summary
This study examines how the turbulence in the upper troposphere/lower stratosphere could modify the tracer distribution under different situations. Using a multi-scale chemistry model, we find that both the pre-existing tracer gradient and the dynamical and thermodynamically forcing play a role in modifying the tracer distribution. These results allow further research on the UTLS turbulent mixing and its implications for the climate system.
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