Aerosol Properties and Cloud Condensation Nuclei Dynamics

Aerosols are suspensions of solid or liquid particles in the atmosphere that vary in size, composition and origin. Their physical and chemical properties determine their ability to act as cloud condensation nuclei (CCN), the particles upon which water vapour condenses to form cloud droplets. Key aerosol characteristics include size distribution, mixing state and hygroscopicity, which together influence cloud droplet number concentrations, cloud lifetime and albedo. The hygroscopicity parameter, κ, provides a concise measure of the water‐uptake capacity of particles and links chemical composition—particularly the balance between organic and inorganic constituents—to CCN activation. Variations in aerosol properties on regional and global scales modulate indirect radiative forcing, affecting climate predictions and the hydrological cycle. Improved understanding of aerosol–cloud interactions underpins more reliable weather forecasting, air‐quality management and the assessment of mitigation strategies for climate change.

Research from Nature Portfolio

Global measurements spanning pristine marine, remote continental and polluted environments reveal that CCN activity can be predicted accurately by a simple linear combination of organic and inorganic mass fractions. The effective aerosol hygroscopicity parameter, κ, was derived as κ = ϵ_org·κ_org + ϵ_inorg·κ_inorg, where ϵ_org and ϵ_inorg denote the fine‐mode mass fractions of organic and inorganic particulate matter. Despite the chemical complexity of organic aerosol, a global average κ_org of 0.12 ± 0.02 captures its water‐uptake behaviour, while κ_inorg of 0.63 ± 0.01 represents inorganic salts. Sensitivity analyses demonstrate that uncertainties in κ_org and κ_inorg impart only small variations in simulated radiative forcing, thereby constraining a critical uncertainty in climate models and supporting the development of more robust parameterisations of aerosol–cloud interactions.

Aerosol Properties and Cloud Condensation Nuclei Dynamics publication trend

The graph below shows the total number of articles in aerosol properties and cloud condensation nuclei dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Aerosol hygroscopicity (κ): A dimensionless parameter quantifying a particle’s water‐uptake capacity, linking chemical composition to CCN activation.

Cloud condensation nucleus (CCN): An aerosol particle sufficiently hygroscopic to activate at a given supersaturation and form a cloud droplet.

Mass fraction (ϵ_org, ϵ_inorg): The proportion of fine aerosol mass constituted by organic (ϵ_org) or inorganic (ϵ_inorg) components.

Supersaturation (S): The amount by which ambient water vapour exceeds equilibrium vapour pressure over a flat surface of pure water, expressed as a percentage.

Köhler theory: A classical framework describing the equilibrium between water vapour and solution droplets, combining Raoult’s law and curvature effects to predict CCN activation.

References

1. Global organic and inorganic aerosol hygroscopicity and its effect on radiative forcing. Nature Communications (2023).
2. In-situ observations reveal weak hygroscopicity in the Southern Tibetan Plateau: implications for aerosol activation and indirect effects. npj Climate and Atmospheric Science (2024).
3. The impact of particulate pollution control on aerosol hygroscopicity and CCN activity in North China. Environmental Research Letters (2023).