What the study found
UKESM1.1 showed different aerosol biases in the upper troposphere and the marine boundary layer, and the pattern pointed to missing aerosol formation pathways in the remote marine atmosphere. The authors report that low aerosol number concentrations persisted even when precursor gases were overestimated, suggesting missing processes.
Why the authors say this matters
The authors conclude that these limitations leave an unbalanced cloud condensation nuclei budget, with too much dependence on primary emissions. The study suggests future model development should prioritize mechanistic representation of currently missing aerosol sources rather than empirical tuning to improve aerosol-climate interaction estimates.
What the researchers tested
The researchers evaluated UKESM1.1 against global aircraft observations from the Atmospheric Tomography (ATom) mission. They assessed aerosol precursor vapours, number size distributions, chemical composition, and environmental conditions, and tested process changes including sulfuric acid-ammonia nucleation, an ammonium nitrate scheme, methanesulfonic acid condensation, and low-temperature isoprene-derived secondary organic aerosol formation.
What worked and what didn't
In the upper troposphere, the model overestimated nucleation and Aitken mode particles and underestimated accumulation mode particles, which the authors interpret as insufficient growth. In the marine boundary layer, it overestimated primary aerosols such as sea salt and precursor gases but still underestimated nucleation and Aitken mode particles, even after updated nucleation and ammonium nitrate schemes were added. Sensitivity tests showed strong influence from dimethyl sulfide emissions and vapour condensation schemes.
What to keep in mind
The abstract does not describe detailed numerical results or observational coverage beyond the ATom mission. It also does not list all limitations, only that missing formation pathways are likely and may involve species such as iodine, amines, and organic vapours.
Key points
- UKESM1.1 showed different aerosol biases in the upper troposphere and the marine boundary layer.
- Low aerosol number concentrations persisted even when precursor gases were overestimated.
- The authors say missing formation pathways may involve iodine, amines, and organic vapours.
- Updated nucleation and ammonium nitrate schemes did not remove the marine boundary layer underestimation of nucleation and Aitken mode particles.
- Sensitivity tests showed strong influence from dimethyl sulfide emissions and vapour condensation schemes.
Disclosure
- Research title:
- UKESM misses key marine aerosol formation pathways
- Authors:
- Xu-Cheng He, Nathan Luke Abraham, Han Ding, M. R. Russo, Daniel P. Grosvenor, Yao Ge, Xuemei Wang, Anthony C. Jones, Pedro Campuzano-Jost, Benjamin Nault, Agnieszka Kupc, Donald Blake, Jose L. Jimenez, Christina Williamson, James Weber, Alexander Archibald, Hamish Gordon
- Institutions:
- Finnish Meteorological Institute, University of Helsinki, University of Cambridge, Carnegie Mellon University, National Centre for Atmospheric Science, University of Leeds, Royal Netherlands Meteorological Institute, Met Office, Cooperative Institute for Research in Environmental Sciences, Johns Hopkins University, Aerodyne Research, University of Vienna, University of California, Irvine, University of Reading
- Publication date:
- 2026-03-17
- OpenAlex record:
- View
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