Preprints
https://doi.org/10.5194/egusphere-2025-721
https://doi.org/10.5194/egusphere-2025-721
21 Mar 2025
 | 21 Mar 2025

Towards an improved understanding of the impact of clouds and precipitation on the representation of aerosols over the Boreal Forest in GCMs

Sini Talvinen, Paul Kim, Emanuele Tovazzi, Eemeli Holopainen, Roxana Cremer, Thomas Kühn, Harri Kokkola, Zak Kipling, David Neubauer, João C. Teixeira, Alistair Sellar, Duncan Watson-Parris, Yang Yang, Jialei Zhu, Srinath Krishnan, Annele Virtanen, and Daniel G. Partridge

Abstract. General circulation models (GCMs) face uncertainties in estimating Earth's radiative budget due to aerosol-cloud interactions (ACI). Accurate aerosol number size distributions are crucial for improving ACI representation in GCMs, requiring precise modelling of aerosol source and sink processes throughout their lifetime. This study employs a Lagrangian trajectory framework to analyse how clouds and precipitation influence aerosol lifecycles during transport in the boreal forest. A comparison of two GCMs, the United Kingdom Earth System Model (UKESM1) and ECHAM6.3-HAM2.3-MOZ1.0 with the SALSA2.0 aerosol module (ECHAM-SALSA), is conducted. An evaluation against in-situ observations and reanalysis-based trajectories is performed. Results show that overall aerosol-precipitation trends are similar between GCMs and observations. However, seasonal differences emerge: in summer, UKESM1 exhibits more efficient aerosol removal via precipitation than ECHAM-SALSA and observations, whereas in winter, the opposite is observed. These were found to coincide with differences in key variables controlling aerosol activation, such as sub-grid scale updraughts and number size distributions. For example, in winter the removal of the total aerosol mass in ECHAM-SALSA was stronger compared to UKESM1, coinciding with higher activated fractions during airmass transport, which, on the other hand, were likely due to the larger sub-grid scale updraughts in ECHAM-SALSA. For both GCMs, investigation of aqueous-phase chemical processing along the trajectories showed clear increase of SO4 mass for cloud-processed air masses when compared to clear sky conditions, in-line with the observations. As expected, based on the model parametrizations, these increases in SO4 were mostly distributed to the accumulation mode aerosols.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.

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.
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Sini Talvinen, Paul Kim, Emanuele Tovazzi, Eemeli Holopainen, Roxana Cremer, Thomas Kühn, Harri Kokkola, Zak Kipling, David Neubauer, João C. Teixeira, Alistair Sellar, Duncan Watson-Parris, Yang Yang, Jialei Zhu, Srinath Krishnan, Annele Virtanen, and Daniel G. Partridge

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-721', Anonymous Referee #1, 10 Apr 2025
  • RC2: 'Comment on egusphere-2025-721', Anonymous Referee #2, 30 May 2025
  • RC3: 'Comment on egusphere-2025-721', Anonymous Referee #3, 14 Jul 2025
  • AC1: 'Response to reviewers', Sini Talvinen, 22 Aug 2025

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-721', Anonymous Referee #1, 10 Apr 2025
  • RC2: 'Comment on egusphere-2025-721', Anonymous Referee #2, 30 May 2025
  • RC3: 'Comment on egusphere-2025-721', Anonymous Referee #3, 14 Jul 2025
  • AC1: 'Response to reviewers', Sini Talvinen, 22 Aug 2025
Sini Talvinen, Paul Kim, Emanuele Tovazzi, Eemeli Holopainen, Roxana Cremer, Thomas Kühn, Harri Kokkola, Zak Kipling, David Neubauer, João C. Teixeira, Alistair Sellar, Duncan Watson-Parris, Yang Yang, Jialei Zhu, Srinath Krishnan, Annele Virtanen, and Daniel G. Partridge
Sini Talvinen, Paul Kim, Emanuele Tovazzi, Eemeli Holopainen, Roxana Cremer, Thomas Kühn, Harri Kokkola, Zak Kipling, David Neubauer, João C. Teixeira, Alistair Sellar, Duncan Watson-Parris, Yang Yang, Jialei Zhu, Srinath Krishnan, Annele Virtanen, and Daniel G. Partridge

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Short summary
Climate models struggle to predict how clouds and aerosols interact, affecting Earth’s energy balance. This study compares models to observations to see how they describe effects of clouds and rain on aerosols. While both models show similar overall trends, seasonal differences emerged. These, however, align with differences in key variables participating in cloud formation. The study provides tools to improve the representation of aerosol-cloud interactions in climate models.
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