Preprints
https://doi.org/10.5194/egusphere-2024-3376
https://doi.org/10.5194/egusphere-2024-3376
16 Dec 2024
 | 16 Dec 2024

High sensitivity of simulated fog properties to parameterized aerosol activation in case studies from ParisFog

Pratapaditya Ghosh, Ian Boutle, Paul Field, Adrian Hill, Anthony Jones, Marie Mazoyer, Katherine J. Evans, Salil Mahajan, Hyun-Gyu Kang, Min Xu, Wei Zhang, Noah Asch, and Hamish Gordon

Abstract. Aerosols influence fog properties such as visibility and lifetime by affecting fog droplet number concentrations (Nd). Numerical weather prediction (NWP) models often represent aerosol-fog interactions using highly simplified approaches. Incorporating prognostic size-resolved aerosol microphysics from climate models could allow them to simulate Nd and aerosol-fog interactions without incurring excessive computational expense. However, microphysics code designed for coarse spatial resolution may struggle with sub-kilometer-scale grid spacings. Here we test the ability of the UK Met Office Unified Model to simulate aerosol and fog properties during case studies from the ParisFog field campaign in 2011. We examine the sensitivity of fog properties to variations in Nd caused by modifications to simulated aerosol activation.

Our model with 500 m horizontal resolution and interactive aerosol and cloud microphysics significantly underpredicts Nd, although only slightly underestimates the cloud condensation nuclei concentration. With an updated version of the Abdul-Razzak and Ghan (2000) activation scheme, we produce Nd that are more consistent with those predicted by a cloud parcel model under fog-like conditions. We activate droplets only by adiabatic cooling. We incorporate more realistic hygroscopicities for sulfate and organic aerosols and explore the sensitivity of simulated Nd to unresolved updrafts. We find that both Nd and simulated fog liquid water content are very sensitive to the updated activation scheme but remain unaffected by the update to hygroscopicities. Our improvements offer insights into the physical processes regulating Nd in stable conditions, potentially laying foundations for improved operational fog forecasts that incorporate interactive aerosol simulations or aerosol climatologies.

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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Journal article(s) based on this preprint

24 Sep 2025
High sensitivity of simulated fog properties to parameterized aerosol activation in case studies from ParisFog
Pratapaditya Ghosh, Ian Boutle, Paul Field, Adrian Hill, Anthony Jones, Marie Mazoyer, Katherine J. Evans, Salil Mahajan, Hyun-Gyu Kang, Min Xu, Wei Zhang, Noah Asch, and Hamish Gordon
Atmos. Chem. Phys., 25, 11129–11156, https://doi.org/10.5194/acp-25-11129-2025,https://doi.org/10.5194/acp-25-11129-2025, 2025
Short summary
Pratapaditya Ghosh, Ian Boutle, Paul Field, Adrian Hill, Anthony Jones, Marie Mazoyer, Katherine J. Evans, Salil Mahajan, Hyun-Gyu Kang, Min Xu, Wei Zhang, Noah Asch, and Hamish Gordon

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3376', Anonymous Referee #3, 27 Dec 2024
  • RC2: 'Comment on egusphere-2024-3376', Anonymous Referee #1, 06 Jan 2025
  • RC3: 'Comment on egusphere-2024-3376', Anonymous Referee #2, 25 Feb 2025
  • AC1: 'Comment on egusphere-2024-3376', Pratapaditya Ghosh, 16 Jun 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3376', Anonymous Referee #3, 27 Dec 2024
  • RC2: 'Comment on egusphere-2024-3376', Anonymous Referee #1, 06 Jan 2025
  • RC3: 'Comment on egusphere-2024-3376', Anonymous Referee #2, 25 Feb 2025
  • AC1: 'Comment on egusphere-2024-3376', Pratapaditya Ghosh, 16 Jun 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Pratapaditya Ghosh on behalf of the Authors (16 Jun 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (18 Jun 2025) by Pablo Saide
AR by Pratapaditya Ghosh on behalf of the Authors (22 Jun 2025)  Manuscript 

Journal article(s) based on this preprint

24 Sep 2025
High sensitivity of simulated fog properties to parameterized aerosol activation in case studies from ParisFog
Pratapaditya Ghosh, Ian Boutle, Paul Field, Adrian Hill, Anthony Jones, Marie Mazoyer, Katherine J. Evans, Salil Mahajan, Hyun-Gyu Kang, Min Xu, Wei Zhang, Noah Asch, and Hamish Gordon
Atmos. Chem. Phys., 25, 11129–11156, https://doi.org/10.5194/acp-25-11129-2025,https://doi.org/10.5194/acp-25-11129-2025, 2025
Short summary
Pratapaditya Ghosh, Ian Boutle, Paul Field, Adrian Hill, Anthony Jones, Marie Mazoyer, Katherine J. Evans, Salil Mahajan, Hyun-Gyu Kang, Min Xu, Wei Zhang, Noah Asch, and Hamish Gordon

Data sets

High sensitivity of simulated fog properties to parameterized aerosol activation in case studies from ParisFog Pratapaditya Ghosh, Ian Boutle, Paul Field, Adrian Hill, Anthony Jones, Marie Mazoyer, Katherine J. Evans, Salil Mahjan, Hyun-Gyu Kang, Min Xu, Wei Zhang, Noah Asch, and Hamish Gordon https://doi.org/10.5281/zenodo.14004871

Pratapaditya Ghosh, Ian Boutle, Paul Field, Adrian Hill, Anthony Jones, Marie Mazoyer, Katherine J. Evans, Salil Mahajan, Hyun-Gyu Kang, Min Xu, Wei Zhang, Noah Asch, and Hamish Gordon

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Short summary
We study aerosol-fog interactions near Paris using a weather and climate model with high spatial resolution. We show that our model can simulate fog lifecycle effectively. We find that the fog droplet number concentrations, the amount of liquid water in the fog, and the vertical structure of the fog are highly sensitive to the parameterization that simulates droplet formation and growth. The changes we propose could improve fog forecasts significantly without increasing computational costs.
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