What the study found
Ice crystal formation in the jet phase of contrails from hydrogen combustion is mainly governed by the number of ambient aerosol particles entrained into the exhaust plume. The study also found a regime in which ice crystal formation becomes nearly independent of ambient relative humidity, aerosol size, and hygroscopicity, where hygroscopicity means how readily particles take up water.
Why the authors say this matters
The authors say this matters because the number of early ice crystals affects the later life cycle and radiative forcing of contrail cirrus clouds, and a parameterization for hydrogen combustion has been lacking. The study suggests its results provide a basis for a data-driven parameterization of ice crystal number in hydrogen contrails, to be presented in a companion paper.
What the researchers tested
The researchers used a particle-based Lagrangian Cloud Module in a box-model framework to run more than 20,000 contrail formation simulations. They covered a broad range of atmospheric conditions and aerosol properties, and examined both single-population and multiple-population aerosol cases.
What worked and what didn't
The simulations showed that the total number of entrained particles primarily controls the nonlinear depletion of water vapor, while coarse-mode particles had negligible impact because they were too scarce. Ice crystal formation from multiple aerosol populations could be reconstructed from single-population simulations using population-specific size and hygroscopicity together with total number concentration. The study also identified conditions where homogeneous droplet nucleation, meaning droplet formation without a pre-existing seed, can be safely neglected as a potential ice-formation pathway.
What to keep in mind
The abstract describes a modeling study in a box-model setup, not a direct observational test. It also notes that the parameterization itself will be presented in a companion paper, so the available summary does not include the final parameterization details.
Key points
- Ice crystal formation in hydrogen contrails is mainly controlled by the number of entrained ambient aerosol particles.
- A regime was found where ice crystal formation is nearly independent of ambient relative humidity, aerosol size, and hygroscopicity.
- More than 20,000 simulations were run with a particle-based Lagrangian Cloud Module in a box-model setup.
- Coarse-mode particles had negligible impact because they were too scarce.
- Multiple-aerosol-population results could be reconstructed from single-population simulations using size, hygroscopicity, and total number concentration.
Disclosure
- Research title:
- Hydrogen contrail ice crystal formation depends on entrained aerosols
- Authors:
- Josef Zink, Simon Unterstrasser, Ulrike Burkhardt
- Institutions:
- Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
- Publication date:
- 2026-03-02
- OpenAlex record:
- View
- Image credit:
- Photo by Mylene2401 on Pixabay · Pixabay License
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