Preprints
https://doi.org/10.5194/egusphere-2023-1436
https://doi.org/10.5194/egusphere-2023-1436
29 Jun 2023
 | 29 Jun 2023

Global Observations of Aerosol Indirect Effects from Marine Liquid Clouds

Casey James Wall, Trude Storelvmo, and Anna Possner

Abstract. Interactions between aerosols and liquid clouds are one of the largest sources of uncertainty in the historical radiative forcing of climate. One widely shared goal to reduce this uncertainty is to decompose radiative anomalies arising from aerosol-cloud interactions into components associated with changes in cloud-droplet number concentration (Twomey effect), liquid water path adjustments, and cloud-fraction adjustments. However, there has not been a quantitative foundation for simultaneously estimating these components with global satellite observations. Here we present a method for assessing shortwave radiative flux anomalies from the Twomey effect and cloud adjustments over ocean between 55° S and 55° N. We find that larger aerosol concentrations are associated with widespread cloud brightening from the Twomey effect, a positive radiative adjustment from decreasing liquid water path in subtropical stratocumulus regions, and a negative radiative adjustment from increasing cloud fraction in the subtropics and midlatitudes. The Twomey effect and total cloud adjustment contribute -0.77±0.25 W m-2 and -1.02±0.43 W m-2, respectively, to the effective radiative forcing since 1850 over the domain (95 % confidence). Our findings reduce uncertainty in these components of aerosol forcing and suggest that cloud adjustments make a larger contribution to the forcing than is commonly believed.

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 preprint. The responsibility to include appropriate place names lies with the authors.

Journal article(s) based on this preprint

18 Oct 2023
| Highlight paper
Global observations of aerosol indirect effects from marine liquid clouds
Casey J. Wall, Trude Storelvmo, and Anna Possner
Atmos. Chem. Phys., 23, 13125–13141, https://doi.org/10.5194/acp-23-13125-2023,https://doi.org/10.5194/acp-23-13125-2023, 2023
Short summary Executive editor
Casey James Wall, Trude Storelvmo, and Anna Possner

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1436', Ying Chen, 14 Jul 2023
  • RC2: 'Comment on egusphere-2023-1436', Jianhao Zhang, 31 Jul 2023
  • AC1: 'Comment on egusphere-2023-1436', Casey Wall, 12 Aug 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1436', Ying Chen, 14 Jul 2023
  • RC2: 'Comment on egusphere-2023-1436', Jianhao Zhang, 31 Jul 2023
  • AC1: 'Comment on egusphere-2023-1436', Casey Wall, 12 Aug 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Casey Wall on behalf of the Authors (12 Aug 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (15 Aug 2023) by Matthew Lebsock
AR by Casey Wall on behalf of the Authors (30 Aug 2023)  Manuscript 

Journal article(s) based on this preprint

18 Oct 2023
| Highlight paper
Global observations of aerosol indirect effects from marine liquid clouds
Casey J. Wall, Trude Storelvmo, and Anna Possner
Atmos. Chem. Phys., 23, 13125–13141, https://doi.org/10.5194/acp-23-13125-2023,https://doi.org/10.5194/acp-23-13125-2023, 2023
Short summary Executive editor
Casey James Wall, Trude Storelvmo, and Anna Possner
Casey James Wall, Trude Storelvmo, and Anna Possner

Viewed

Total article views: 582 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
373 190 19 582 37 9 8
  • HTML: 373
  • PDF: 190
  • XML: 19
  • Total: 582
  • Supplement: 37
  • BibTeX: 9
  • EndNote: 8
Views and downloads (calculated since 29 Jun 2023)
Cumulative views and downloads (calculated since 29 Jun 2023)

Viewed (geographical distribution)

Total article views: 587 (including HTML, PDF, and XML) Thereof 587 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 18 Sep 2024
Download

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

One of the largest sources of uncertainty in the overall anthropogenic forcing of climate is still the aerosol impact on liquid clouds. Disentangling the various aerosol-cloud interactions helps to improve estimates of the magnitude of global warming in the future. The current study provides the most rigorous method to date in assessing the aerosol radiative effects from satellite observations across the global ocean. The aerosol responses are decomposed into the Twomey effect (cooling due to an increase in cloud-droplet number concentration), and the adjustments of the cloud liquid water path and cloud fraction (often analysed separately) at a near-global scale. The total effective radiative forcing of liquid clouds since 1850 has been found to be negative, with the cloud adjustments larger than the Twomey effect, which was previously thought to be larger.
Short summary
We use satellite data to investigate how aerosol particles affect the radiative properties of liquid clouds across the global ocean. In particular, we quantify radiative perturbations arising from aerosol-driven changes in the number density of cloud droplets, the vertically integrated cloud water mass, and the cloud amount. Our results imply that aerosol effects on clouds make a larger contribution to anthropogenic climate forcing than is commonly believed.