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An ice nucleus, also known as an ice nucleating particle (INP), is a particle which acts as the nucleus for the formation of an ice crystal in the atmosphere.

Ice nucleation mechanisms

There are a number of mechanisms of ice nucleation in the atmosphere through which ice nuclei can catalyse the formation of ice particles. In the upper troposphere, water vapor can deposit directly onto solid particles. In clouds warmer than about −37 °C where liquid water can persist in a supercooled state, ice nuclei can trigger droplets to freeze.

Contact nucleation can occur if an ice nucleus collides with a supercooled droplet, but the more important mechanism of freezing is when an ice nucleus becomes immersed in a supercooled water droplet and then triggers freezing.

In the absence of an ice nucleating particle, pure water droplets can persist in a supercooled state to temperatures approaching −37 °C where they freeze homogeneously.

As per Web of Science, the key word "ice nucleation" that appeared under Met Atm Sci and Env Sci categories till Dec 2021 was plotted using number of papers published.

There are several research groups that study ice nucleating properties of atmospheric aerosols (for example see FIN-02 research article by DeMott et al. 2018 or the FIN-02 INP measurement intercomparison study). The ice nucleation research capability is also available through user facility call at EMSL, PNNL.

Cloud dynamics

Ice particles can have a significant effect on cloud dynamics. They are known to be important in the processes by which clouds can become electrified, which causes lightning. They are also known to be able to form the seeds for rain droplets. It has become clear that the concentration of ice nucleating particles in shallow clouds is a key factor in cloud-climate feedbacks.

Atmospheric particulate matter

Many different types of atmospheric particulate matter can act as ice nuclei, both natural and anthropogenic, including those composed of desert dust, soot, organic matter, bacteria (e.g. Pseudomonas syringae), pollen, fungal spores and volcanic ash amongst others. However, the exact nucleation potential of each type varies greatly, depending on the exact atmospheric conditions. Very little is known about the spatial distribution of these particles, their overall importance for global climate through ice cloud formation, and whether human activity has played a major role in changing these effects.

See also

• Bergeron process
• Cloud condensation nuclei
• Nucleation
• Snow
• Supercooling

References

1. ^ Murray; et al. (2012). "Ice nucleation by particles immersed in supercooled cloud droplets". Chem Soc Rev. 41 (19): 6519–6554. doi:10.1039/c2cs35200a. PMID 22932664.
2. Kulkarni G (2014). "Ice nucleation of bare and sulfuric acid-coated mineral dust particles and implication for cloud properties". Journal of Geophysical Research. 119 (16): 9993–10011. Bibcode:2014JGRD..119.9993K. doi:10.1002/2014JD021567. S2CID 133885221.
3. Koop, T. (March 25, 2004). "Homogeneous ice nucleation in water and aqueous solutions". Zeitschrift für Physikalische Chemie. 218 (11): 1231–1258. doi:10.1524/zpch.218.11.1231.50812. S2CID 46915879. Archived from the original on 2012-08-11. Retrieved 2008-04-07.
4. Murray B (2010). "Homogeneous ice nucleation in water and aqueous solutions". Physical Chemistry Chemical Physics. 12 (35): 10380–10387. Bibcode:2010PCCP...1210380M. doi:10.1039/c003297b. PMID 20577704.
5. DeMott, Paul J. (2018-11-19). "The Fifth International Workshop on Ice Nucleation phase 2 (FIN-02): laboratory intercomparison of ice nucleation measurements". Atmospheric Measurement Techniques. 11 (11). Copernicus GmbH: 6231–6257. Bibcode:2018AMT....11.6231D. doi:10.5194/amt-11-6231-2018. ISSN 1867-8548.
6. "Environmental Molecular Sciences Laboratory: A DOE Office of Science User Facility". Environmental Molecular Sciences Laboratory. Retrieved 2023-07-13.
7. Murray, Benjamin J.; Carslaw, Kenneth S.; Field, Paul R. (21 August 2020). "Opinion: Cloud-phase climate feedback and the importance of ice-nucleating particles". doi:10.5194/acp-2020-852. {{cite journal}}: Cite journal requires |journal= (help)
8. Vergara-Temprado, Jesús; Miltenberger, Annette K.; Furtado, Kalli; Grosvenor, Daniel P.; Shipway, Ben J.; Hill, Adrian A.; Wilkinson, Jonathan M.; Field, Paul R.; Murray, Benjamin J.; Carslaw, Ken S. (13 March 2018). "Strong control of Southern Ocean cloud reflectivity by ice-nucleating particles". Proceedings of the National Academy of Sciences. 115 (11): 2687–2692. Bibcode:2018PNAS..115.2687V. doi:10.1073/pnas.1721627115. PMC 5856555. PMID 29490918.
9. Christner BC, Morris CE, Foreman CM, Cai R, Sands DC (2008). "Ubiquity of biological ice nucleators in snowfall". Science. 319 (5867): 1214. Bibcode:2008Sci...319.1214C. CiteSeerX 10.1.1.395.4918. doi:10.1126/science.1149757. PMID 18309078. S2CID 39398426.

• Cloud and fog physics
• Particulates