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Dust-driven droplet freezing explains cloud-top phase in the northern extratropics
D Villanueva1, M Stengel2, C Hoose3
1Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland.
Science (New York, N.Y.)
|July 31, 2025
Summary
Dust aerosol significantly influences cloud-top ice formation in the Northern Hemisphere. This finding, based on 35 years of satellite data, clarifies factors controlling cloud properties and their climate impact.
Area of Science:
- Atmospheric Science
- Cloud Physics
- Climate Science
Background:
- Mixed-phase clouds between -39°C and 0°C can have liquid or ice layers, impacting radiative forcing and precipitation.
- The cloud-top ice-to-total frequency (ITF) is a key metric, but its controlling factors remain unclear.
Purpose of the Study:
- To investigate the factors controlling cloud-top ice-to-total frequency (ITF).
- To determine the role of dust aerosol in cloud glaciation.
Main Methods:
- Analysis of 35 years of satellite data.
- Spatio-temporal correlation analysis between dust aerosol and ITF.
- Comparison of observed ITF sensitivities with laboratory freezing experiments.
Main Results:
- A strong spatio-temporal correlation was found between dust aerosol and ITF in the Northern Hemisphere between -15°C and -30°C.
- The ratio of ITF sensitivities to temperature and dust aligns with laboratory droplet freezing measurements.
Conclusions:
- Cloud-top ice formation (ITF) in this temperature range is primarily attributed to dust aerosol.
- Dust aerosol acts as a crucial factor influencing cloud phase and climate interactions.
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