Constraining the uncertainty associated with sea salt aerosol parameterizations in global models using nudged UKESM1‐AMIP simulations

Venugopal, A. U. ORCID: https://orcid.org/0000-0003-2235-5964, Bhatti, Y. A. ORCID: https://orcid.org/0000-0003-1254-9845, Morgenstern, O. ORCID: https://orcid.org/0000-0002-9967-9740, Williams, J. ORCID: https://orcid.org/0000-0002-0680-0098, Edkins, N., Hardacre, C. ORCID: https://orcid.org/0000-0001-9093-4656, Jones, A. ORCID: https://orcid.org/0000-0002-3894-2867 and Revell, L. E. ORCID: https://orcid.org/0000-0002-8974-7703 (2025) Constraining the uncertainty associated with sea salt aerosol parameterizations in global models using nudged UKESM1‐AMIP simulations. Journal of Geophysical Research: Atmospheres, 130 (2). e2024JD041643. ISSN 2169-8996 doi: 10.1029/2024jd041643

Abstract/Summary

Sea salt is the largest source of natural aerosol in the atmosphere by mass. Formed when ocean waves break and bubbles burst, sea salt aerosols (SSA) influence Earth's climate via direct and indirect processes. Models participating in the sixth Coupled Model Intercomparison project (CMIP6) demonstrate a negative effective radiative forcing (ERF) when SSA emissions are doubled. However, the magnitude of the ERF ranges widely from −0.35 0.04 W to −2.28 0.07 W , with the largest difference over the Southern Ocean. Differences in the response to doubled SSA emissions arise from model uncertainty (e.g., individual model physics, aerosol size distribution) and parameterization uncertainty (e.g., how SSA is produced in the model). Here, we perform single‐model experiments with UKESM1‐AMIP incorporating all of the SSA parameterizations used by the current generation of CMIP6 Earth system models (ESMs). Using a fixed SSA size distribution, our experiments show that the parameterization uncertainty causes large inter‐model diversity in SSA emissions in the models, particularly over the tropics and the Southern Ocean. The choice of parameterization influences the ambient aerosol size distribution, cloud condensation nuclei and cloud droplet number concentrations, and therefore direct and indirect radiative forcing. We recommend that modeling groups evaluate their SSA parameterizations and update them where necessary in preparation for future model intercomparison activities.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/120470
Item Type	Article
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	American Geophysical Union (AGU)
Download/View statistics	View download statistics for this item